Economic Issues Simulation

Health Maintenance Organizations (HMOs) have an important role to their patients and their health care providers. Castor Collins Health Care Plan was found in the year of 1999, in Pantome. This particular HMO service provide health care insurance and health care services to a variety of physicians and hospitals. This company used the capitation idea for compensation to pay its health care providers. Castor Collins is currently serving 100,000 members, throughout Pantome, and is looking for ways to increase the their numbers.I am a representative of Castor Insurance Organization. I am as well the Vice President, Strategy and Financial Planning here at Castor Collins. My responsibilities include but not limited to, interacting with new potential clients and conveying health care plans that will be benefit them. My job here is to try and maximize profit and also minimize the risk for the company. I will do an analysis that will include the demographics of the employees, the health care risk factors or potential areas of high utilization, and the premiums the company is willing to pay.I will give at least two reasons why I would either choose the Constructit or the E-editor plans. I will state the plan I would be willing to sell to my company, and provide the reasons for my choice, and why the other plans would not be beneficial to my company. In January of 2006, Castor Collins was approached by two organizations looking for health insurance. The two groups Castor Collins have to choose from are Constructit and the E-editor. Construcit have total of a 1000 people, and the E-editor consist of 1600.Neither company provide insurance for their employees at the present time. The Constructit group are willing to pay at least $4000 per person, and the E-editor is willing to pay the least possible $4500 per person. The Castor standard plan do not pre-existing medical concerns, and the Castor enhanced insurance to cover pre-existing medical concerns. The plan to be consider ed first is the Castor Standard Plan. This plan will offer prescriptions, emergency facilities, hospitalization, and ways to help for preventive health services.This pan as we stated earlier do not cover pre-existing medical concerns. The fee for this plan is at least $3,428 which is $572 less than what they were willing to pay for each employee. The second option to consider for the insurance would be the Castor Enhanced Plan. This plan do cover pre-existing medical conditions it will provide coverage to all its employees. It will still provide services to the obese employees. The cost for pre-existing conditions can be estimated at a total of $4, 428, which is slightly higher than the company was willing to pay per employee.It would only work if the company agreed to pay the higher premium in order to benefit all employees especially those with pre-existing medical conditions. The last and final option is the Castor Enhanced Minor plan. This is also a good plan because it will cov er pre-existing medical conditions as well. This plan is the only one that will allow certain services to be removed in order to make the premiums at a lower cost. By removing certain services, it will allow the total cost per employee to be under $4000. It will still cover the bare services like hearing and vision care.The Health care plan I feel would be more beneficial to the company and its employees is the last choice. The Castor Enhanced Minor plan. This plan will cover the employees with the pre-existing medical conditions, and will offer the amount they are willing to pay per employee. This plan can be accustomed to fit the needs of the company. If the company wanted to remove obesity medical services as an option they could. This will save the company money on problems that is related obesity such as hypertension and diabetes. Choosing this plan there will bea charge of $3,943, that is a slight less than $4000.Castor Hall will benefit from this. They will make 3. 9million f rom Construcit. The company have a total of 450 women and a total of 550 men. The woman ages range from 26 to 42 years of age, and the men 26 to 45. The company Constructit work duties have 32% of duties that involve heavy physical activities and 25% that will involve light to moderate physical activities. A main factor to consider when choosing which type of insurance to choose from is the level of high risk for the employees. Obesity is the main problem that is affecting their company.Obesity can cause problems such as hypertension, and heart disease. This will include more doctor visits and prescriptions that will increase the cost of health care for this company. The health problems the company will have to deal with are nearly half of the employees are obese. With total of 198 men and 192 women. That is 39% of the personnel. Blood pressure is another cause of major medical concerns at Constructit. The percentage is 19%, 88 men and 105 women. There are employees that suffer with allergy. It affects 85 women and 92 men that is 17% .Migraine are 16%, this include 93 women and 75 men. Only 13% of the personnel surprisingly suffer with Respiratory Disease. That number include 57 women and 78 men. The last medical condition the company should be concerned with since it has lower percentage of employees suffering with is digestive orders is the least at 8% with total of 32 women and 52 men. Knowing the demographics of the medical conditions of all the employees, this help to choose a plan to benefit the employees and be affordable to Constritit also, and not go over the budget of $4000 per employee.As vice President, Strategy and Financial Planning at Castor Collins, I would not choose either plan. The standard plan will not cover obesity. With the rate of 39%, that would be important to make sure my employees are in a situation to receive the medical attention they need. The Castor Enhance plan do cover pre-existing conditions, but it don’t give the poss ibility to add or remove the medical services that’s more beneficial to the employees. The services offered in this plan would increase would extend the amount the employees are willing to pay, it would not be profitable to Castor Hall.

Street Light

INDEX |S.NO |TITLE |PAGE NO | |1 |Introduction |1 | |2 |Solar Energy |4 | |3 |Photovoltaics |24 | |4 |Solar Cell |28 | |5 |Solar Roadway |51 | |6 |Component description |55 | |7 |Working of Project |82 | |8 |Conclusion |86 | |9 |Images |91 | |10 |Bibliography |93 | INTRODUCTION INTRODUCTION: Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies.Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity and solar architecture, which can make considerable contributions to solving some of the most urgent energy problems the world now faces. Solar power is the conversion of sunlight into electricity, either directly using photovoltaic (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics convert light into electric cur rent using the photoelectric effect. A Street light, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or walkway, which is turned on or lit at a certain time every night.Modern lamps may also have light-sensitive photocells to turn them on at dusk, off at dawn, or activate automatically in dark weather. In older lighting this function would have been performed with the aid of a solar dial. It is not uncommon for street lights to be on posts which have wires strung between them; such as on telephone poles or utility poles. New street lighting technologies, such as LED or induction lights, emit a white light that provides high levels of scotopic lumens allowing street lights with lower wattages and lower photopic lumens to replace existing street lights. Photovoltaic-powered LED luminaires are gaining wider acceptance.Preliminary field tests show that some LED luminaires are energy-efficient and perform well in testing environme nts. This project is a LED based Solar Lights is an automatic street lightening system using a LDR and 6V/5W solar panel. During day time, the internal rechargeable battery receives charging current from the connected solar panel. Here IC 555 is wired as a medium current inverting line driver, switched by an encapsulated light detector (LDR). When ambient light dims, the circuits drive the white LEDs. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit. Block Diagram: SOLAR ENERGY SOLAR ENERGYSolar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity, solar architecture and artificial photosynthesis, which can make considerable contributions to solving some of the most urgent energy problems the world now faces. Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy.Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. In 2011, the International Energy Agency said that â€Å"the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global.Hence the additional costs of the incentives for early deployment should be co nsidered learning investments; they must be wisely spent and need to be widely shared†. The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet. Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their temperature. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection.When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface, completing the water cycle. The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones. Sunlight absorbed by the o ceans and land masses keeps the surface at an average temperature of 14  °C. By photosynthesis green plants convert solar energy into chemical energy, which produces food, wood and the biomass from which fossil fuels are derived. The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy in one hour than the world used in one year.Photosynthesis captures approximately 3,000 EJ per year in biomass. The technical potential available from biomass is from 100–300 EJ/year. The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined. Solar energy can be harnessed at different levels around the world, mostly depending on distance from the equator. [pic] Average insolation showing land area (small black dots) required to replace the world primary energy supply with solar electricity. 18 TW is 568 Exajoule (EJ) per year.Insolation for most people is from 150 to 300 W/m2 or 3. 5 to 7. 0 kWh/m2/day. Solar energy refers primarily to the use of solar radiation for practical ends. However, all renewable energies, other than geothermal and tidal, derive their energy from the sun. Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun.Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the need for alternate resources and are g enerally considered demand side technologies. APPLICATIONS OF SOLAR TECHNOLOGY Average  insolation  showing land area (small black dots) required to replace the world primary energy supply with solar electricity. 18 TW is 568 Exajoule (EJ) per year. Insolation for most people is from 150 to 300 W/m2  or 3. 5 to 7. 0 kWh/m2/day. Solar energy refers primarily to the use of  solar radiation  for practical ends. However, all renewable energies, other than  geothermal  and  tidal, derive their energy from the sun. Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight.Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies incr ease the supply of energy and are considered  supply side technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies ARCHITECTURE AND URBAN PLANNING [pic] Darmstadt University of Technology  in Germany  won the 2007  Solar Decathlon  in Washington, D. C. with this  passive house designed specifically for the humid and hot subtropical climate.Sunlight has influenced building design since the beginning of architectural history. Advanced solar architecture and urban planning methods were first employed by the  Greeks  and  Chinese, who oriented their buildings toward the south to provide light and warmth. The common features of  passive solar  architecture are orientation relative to the Sun, compact proportion (a low surface area to volume ratio), selective shading (overhangs) and  thermal mass. When these features are tailored to the local climate and environment they can produce well-lit spaces that stay in a comfortable temperature range. Socrates'  Megaron House is a classic example of passive solar design.The most recent approaches to solar design use computer modeling tying together  solar lighting,  heating  and  ventilation  systems in an integrated  solar design  package. Active solar equipment such as pumps, fans and switchable windows can complement passive design and improve system performance. Urban heat islands (UHI) are metropolitan areas with higher temperatures than that of the surrounding environment. The higher temperatures are a result of increased absorption of the Solar light by urban materials such as asphalt and concrete, which have lower  albedos  and higher  heat capacities  than those in the natural environment. A straightforward method of counteracting the UHI effect is to paint buildings and roads white and plant trees.Using these methods, a hypothetical â€Å"cool communities† program in  Los Ang eles  has projected that urban temperatures could be reduced by approximately 3  Ã‚ °C at an estimated cost of US$1  billion, giving estimated total annual benefits of US$530  million from reduced air-conditioning costs and healthcare savings. [23] AGRICULTURE AND HORTICULTURE [pic] Greenhouses  like these in the Westland municipality of the  Netherlands  grow vegetables, fruits and flowers. Agriculture  and  horticulture  seek to optimize the capture of solar energy in order to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields. [24][25]  While sunlight is generally considered a plentiful resource, the exceptions highlight the importance of solar energy to agriculture.During the short growing seasons of the  Little Ice Age, French and  English  farmers employed fruit walls to maximize the collection of solar energ y. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls were developed to make better use of sunlight. In 1699,  Nicolas Fatio de Duillier  even suggested using a  tracking mechanism  which could pivot to follow the Sun. [26]  Applications of solar energy in agriculture aside from growing crops include pumping water, drying crops, brooding chicks and drying chicken manure. [27][28]  More recently the technology has been embraced by vinters, who use the energy generated by solar panels to power grape presses. [29]Greenhouses  convert solar light to heat, enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first used during Roman times to produce  cucumbers  year-round for the Roman emperor  Tiberius. [30]à ‚  The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad. [31]  Greenhouses remain an important part of horticulture today, and plastic transparent materials have also been used to similar effect in  polytunnels  and  row covers. TRANSPORT AND RECONNAISSANCE [pic] Australia hosts the  World Solar Challengewhere solar cars like the Nuna3 race through a 3,021  km (1,877  mi) course from Darwin to Adelaide.Development of a solar powered car has been an engineering goal since the 1980s. The  World Solar Challenge  is a biannual solar-powered car race, where teams from universities and enterprises compete over 3,021 kilometres (1,877  mi) across central Australia from  Darwin  to  Adelaide. In 1987, when it was founded, the winner's average speed was 67 kilometres per hour (42  mph) and by 2007 the winner's average speed had improved to 90. 87 kilometres per hour (56. 46  mph). [32]à ‚  The  North American Solar Challenge  and the planned  South African Solar Challenge  are comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. [33][34]Some vehicles use solar panels for auxiliary power, such as for air conditioning, to keep the interior cool, thus reducing fuel consumption. [35][36] In 1975, the first practical solar boat was constructed in England. [37]  By 1995, passenger boats incorporating PV panels began appearing and are now used extensively. [38]  In 1996,  Kenichi Horie  made the first solar powered crossing of the Pacific Ocean, and the  sun21  catamaran made the first solar powered crossing of the Atlantic Ocean in the winter of 2006–2007. [39]  There are plans to circumnavigate the globe in 2010. [40] [pic] Helios UAV  in solar powered flight. In 1974, the unmanned  AstroFlight Sunrise  plane made the first solar flight.On 29 April 1979, the  Sol ar Riser  made the first flight in a solar powered, fully controlled, man carrying flying machine, reaching an altitude of 40 feet (12  m). In 1980, the  Gossamer Penguin  made the first piloted flights powered solely by photovoltaics. This was quickly followed by the  Solar Challenger  which crossed the English Channel in July 1981. In 1990  Eric Scott Raymond  in 21 hops flew from California to North Carolina using solar power. [41]  Developments then turned back to unmanned aerial vehicles (UAV) with the  Pathfinder  (1997) and subsequent designs, culminating in the  Helios  which set the altitude record for a non-rocket-propelled aircraft at 29,524 metres (96,864  ft) in 2001. 42]  The  Zephyr, developed by  BAE Systems, is the latest in a line of record-breaking solar aircraft, making a 54-hour flight in 2007, and month-long flights are envisioned by 2010. [43] A  solar balloon  is a black balloon that is filled with ordinary air. As sunlig ht shines on the balloon, the air inside is heated and expands causing an upward  buoyancy  force, much like an artificially heated  hot air balloon. Some solar balloons are large enough for human flight, but usage is generally limited to the toy market as the surface-area to payload-weight ratio is relatively high. [44] DAYLIGHTING [pic] Daylighting features such as this  oculusat the top of the  Pantheon, in  Rome, Italy have been in use since antiquity.The history of lighting is dominated by the use of natural light. The Romans recognized a  right to light  as early as the  6th century  and English law echoed these judgments with the Prescription Act of 1832. [45][46]  In the 20th century artificial  lighting  became the main source of interior illumination but daylighting techniques and hybrid solar lighting solutions are ways to reduce energy consumption. Daylighting  systems collect and distribute sunlight to provide interior illumination. This pass ive technology directly offsets energy use by replacing artificial lighting, and indirectly offsets non-solar energy use by reducing the need for  air-conditioning. 47]  Although difficult to quantify, the use of  natural lighting  also offers physiological and psychological benefits compared to  artificial lighting. [47]  Daylighting design implies careful selection of window types, sizes and orientation; exterior shading devices may be considered as well. Deciduous trees at the east and west ends of buildings offer shade in the summer and do not block the sun in the winter. [48]  Individual features include sawtooth roofs,  clerestory windows, light shelves,  skylights  and  light tubes. They may be incorporated into existing structures, but are most effective when integrated into a  solar design  package that accounts for factors such as  glare, heat flux and  time-of-use.When daylighting features are properly implemented they can reduce lighting-rel ated energy requirements by 25%. [49] Hybrid solar lighting  (HSL) is an  active solar  method of providing interior illumination. HSL systems collect sunlight using focusing mirrors that  track the Sun  and use  optical fibers  to transmit it inside the building to supplement conventional lighting. In single-story applications these systems are able to transmit 50% of the direct sunlight received. [50] Solar lights that charge during the day and light up at dusk are a common sight along walkways. [51]  Solar-charged lanterns have become popular in developing countries where they provide a safer and cheaper alternative to kerosene lamps. [52]Although  daylight saving time  is promoted as a way to use sunlight to save energy, recent research reports contradictory results: several studies report savings, but just as many suggest no effect or even a net loss, particularly when  gasoline  consumption is taken into account. Electricity use is greatly affected by g eography, climate and economics, making it hard to generalize from single studies. [53] SOLAR THERMAL Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation. [54] WATER HEATING [pic] Solar water heaters facing the  Sun  to maximize gain. Solar hot water systems use sunlight to heat water.In low geographical latitudes (below 40  degrees) from 60 to 70% of the domestic hot water use with temperatures up to 60  Ã‚ °C can be provided by solar heating systems. [55]  The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat swimming pools. [56] As of 2007, the total installed capacity of solar hot water systems is approximately 154  GW. [57]  China is the world leader in their deployment with 70  GW installed as of 2006 and a long term goal of 210  GW by 2 020. [58]  Israel  and  Cyprus  are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. 59]  In the United States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18  GW as of 2005. [18] HEATING, COOLING AND VENTILATION [pic] Solar House #1 of  Massachusetts Institute of Technology  in the United States, built in 1939, used  Seasonal thermal energy storage (STES)  for year-round heating. In the United States,  heating, ventilation and air conditioning  (HVAC) systems account for 30% (4. 65  EJ) of the energy used in commercial buildings and nearly 50% (10. 1  EJ) of the energy used in residential buildings. [49][60]  Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.Thermal mass is any material that can be used to store heat—heat from the Sun in the case of solar energy. Common therm al mass materials include stone, cement and water. Historically they have been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during the day and radiating stored heat to the cooler atmosphere at night. However they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, daylighting and shading conditions. When properly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment. [61]A solar chimney (or thermal chimney, in this context) is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an  updraft  that pulls air through the building. Performance can be improved by using glazing and thermal mass materials[62]  in a way that mimics green houses. Deciduous  trees and plants have been promoted as a means of controlling solar heating and cooling. When planted on the southern side of a building, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter. [63]  Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. 64]  In climates with significant heating loads, deciduous trees should not be planted on the southern side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter solar gain. [65] WATER TREATMENT [pic] Solar water disinfection  in  Indonesia [pic] Small scale solar powered sewerage treatment plant. Solar distillation can be used to make  saline  or  brackish water  potable. The firs t recorded instance of this was by 16th century Arab alchemists. [66]  A large-scale solar distillation project was first constructed in 1872 in the  Chilean  mining town of Las Salinas. 67]  The plant, which had solar collection area of 4,700  m2, could produce up to 22,700  L  per day and operated for 40  years. [67]  Individual  still  designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. [66]  These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications. [66] Solar water  disinfection  (SODIS) involves exposing water-filled plastic  polyethylene terephthalate  (PET) bottles to sunlight for several hours. 68]  Exposure times vary depending on weather and climate from a minimum of six hours to two days dur ing fully overcast conditions. [69]  It is recommended by theWorld Health Organization  as a viable method for household water treatment and safe storage. [70]  Over two million people in developing countries use this method for their daily drinking water. [69] Solar energy may be used in a water stabilisation pond to treat  waste water  without chemicals or electricity. A further environmental advantage is thatalgae  grow in such ponds and consume  carbon dioxide  in photosynthesis, although algae may produce toxic chemicals that make the water unusable. [71][72] COOKING [pic]The Solar Bowl in  Auroville,  India, concentrates sunlight on a movable receiver to produce  steam  for  cooking. Solar cookers use sunlight for cooking, drying and  pasteurization. They can be grouped into three broad categories: box cookers, panel cookers and reflector cookers. [73]  The simplest solar cooker is the box cooker first built by  Horace de Saussure  in 1767. [7 4]  A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90–150  Ã‚ °C. [75]Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers.Reflector cookers use various concentrating geometries (dish, trough, Fresnel mirrors) to focus light on a cooking container. These cookers reach temperatures of 315  Ã‚ °C and above but require direct light to function properly and must be repositioned to track the Sun. [76] The  solar bowl  is a concentrating technology employed by the Solar Kitchen at  Auroville, in  Tamil Nadu,  India, where a stationary spherical reflector focuses light along a line perpendicular to the sphere's interior surface, and a computer control system moves the receiver to intersect this line. Steam is produced in the receiver at temperatures reaching 150   Ã‚ °C and then used for process heat in the kitchen. [77]A reflector developed by  Wolfgang Scheffler  in 1986 is used in many solar kitchens. Scheffler reflectors are flexible parabolic dishes that combine aspects of trough and power tower concentrators. Polar tracking  is used to follow the Sun's daily course and the curvature of the reflector is adjusted for seasonal variations in the incident angle of sunlight. These reflectors can reach temperatures of 450–650  Ã‚ °C and have a fixed focal point, which simplifies cooking. [78]  The world's largest Scheffler reflector system in Abu Road,  Rajasthan, India is capable of cooking up to 35,000 meals a day. [79]As of 2008, over 2,000 large Scheffler cookers had been built worldwide. [80] PROCESS HEATSolar concentrating technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat for commercial and industrial applications. The first commercial system was the  Solar Total Energy Project  (STEP) in Shenandoah, Georgia, USA where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided 400  kW of electricity plus thermal energy in the form of 401  kW steam and 468  kW chilled water, and had a one hour peak load thermal storage. [81] Evaporation ponds are shallow pools that concentrate dissolved solids through  evaporation. The use of evaporation ponds to obtain salt from sea water is one of the oldest applications of solar energy.Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams. [82] Clothes lines,  clotheshorses, and clothes racks dry clothes through evaporation by wind and sunlight without consuming electricity or gas. In some states of the United States legislation protects the â€Å"right to dry† clothes. [83] Unglazed transpired collecto rs (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise the incoming air temperature up to 22  Ã‚ °C and deliver outlet temperatures of 45–60  Ã‚ °C. [84]  The short payback period of transpired collectors (3 to 12  years) makes them a more cost-effective alternative than glazed collection systems. 84]  As of 2003, over 80 systems with a combined collector area of 35,000  m2  had been installed worldwide, including an 860  m2  collector in  Costa Rica  used for drying coffee beans and a 1,300  m2  collector in  Coimbatore, India used for drying marigolds. [28] ELECTRICITY PRODUCTION [pic] The  PS10  concentrates sunlight from a field of heliostats on a central tower. Solar power is the conversion of sunlight into  electricity, either directly using  photovoltaics  (PV), or indirectly using  concentrated solar power  (CSP). CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using the  photoelectric effect. Commercial CSP plants were first developed in the 1980s. Since 1985 the eventually 354 MW  SEGS  CSP installation, in the Mojave Desert of California, is the largest solar power plant in the world.Other large CSP plants include the 150 MW  Solnova Solar Power Station  and the 100 MWAndasol solar power station, both in Spain. The 250 MW  Agua Caliente Solar Project, in the United States, and the 214 MW  Charanka Solar Park  inIndia, are the  world’s largest  photovoltaic plants. Solar projects exceeding 1 GW are being developed, but most of the deployed photovoltaics are in small rooftop arrays of less than 5 kW, which are grid connected using net metering and/or a feed-in tariff. [85] Concentrated solar power Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concen trated heat is then used as a heat source for a conventional power plant.A wide range of concentrating technologies exists; the most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems a  working fluid  is heated by the concentrated sunlight, and is then used for power generation or energy storage. [86] PHOTOVOLTAICS PHOTOVOLTAICS A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver selenite in place of copper oxide.Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discove ry. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4. 5–6%. By 2012 available efficiencies exceed 20% and the maximum efficiency of research photovoltaics is over 40%. OTHERS Besides concentrated solar power and photovoltaics, there are some other techniques used to generated electricity using solar power. These include: †¢Dye-sensitized_solar_cells, Luminescent solar concentrators (a type of concentrated photovoltaics or CPV technology), †¢Biohybrid solar cells, †¢Photon Enhanced Thermionic Emission systems. Development, deployment and economics Beginning with the surge in coal use which accompanied the Industrial Revolution, energy consumption has steadily transitioned from wood and biomass to fossil fuels. The early development of solar technologies starting in the 1860s was driven by an exp ectation that coal would soon become scarce. However development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum. [109]The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies. Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the US (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer Institute for Solar Energy Systems ISE). Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by cheaper and more reliable heating fuels.As with photovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interest subsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and growth rates have averaged 20% per year since 1999. [57] Although generally underestimated, solar water heating and cooling is by far the most widely deployed solar technology with an estimated capacity of 154 GW as of 2007. The International Energy Agency has said that solar energy can make considerable contributions to solving some of the most urgent problems the world now faces: The development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits.It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared. In 2011, the International Energy Agency said that solar energy technologies such as photovoltaic panels, solar water heaters and power stations built with mirrors could provide a third of the world’s energy by 2060 if politicians commit to limiting climate change. The energy from the sun could play a key role in de-carbonizing the global economy alongside improvements in energy efficiency and imposing costs on greenhouse gas emitters. The strength of solar is the incredible variety and flexibility of applications, from small scale to big scale†. We have proved †¦ that after our stores of oil and coal are exhausted the human race can receive unlimited power from the rays of the sun. —Frank Shuman, New York Times, July 2, 1916 SOLAR CELL SOLAR CELL A solar cell made from amonocrystalline silicon wafer Sola r cells can be used devices such as this portable monocrystalline solar charger. A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell (in that its electrical characteristics—e. g. urrent, voltage, or resistance—vary when light is incident upon it) which, when exposed to light, can generate and support an electric current without being attached to any external voltage source. The term â€Å"photovoltaic† comes from the Greek (phos) meaning â€Å"light†, and from â€Å"Volt†, the unit of electro-motive force, the volt, which in turn comes from the last name of the Italian physicist Alessandro Volta, inventor of the battery (electrochemical cell). The term â€Å"photo-voltaic† has been in use in English since 1849. Photovoltaics is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight.Cells can be described as photovoltaic even when the light source is not necessarily sunlight (lamplight, artificial light, etc. ). In such cases the cell is sometimes used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiationnear the visible range, or measuring light intensity. The operation of a photovoltaic (PV) cell requires 3 basic attributes: 1. The absorption of light, generating either electron-hole pairs or excitons. 2. The separation of charge carriers of opposite types. 3. The separate extraction of those carriers to an external circuit. In contrast, a solar thermal collector collects heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation. Photoelectrolytic cell† (photoelectrochemical cell), on the other hand, refe rs either a type of photovoltaic cell (like that developed by A. E. Becquerel and modern dye-sensitized solar cells) or a device that splits water directly into hydrogen and oxygen using only solar illumination. FURTHER IMPROVEMENTS In the time since Berman's work, improvements have brought production costs down under $1 a watt, with wholesale costs well under $2. â€Å"Balance of system† costs are now more than the panels themselves. Large commercial arrays can be built at below $3. 40 a watt,[12][13]  fully commissioned. As the semiconductor industry moved to ever-larger boules, older equipment became available at fire-sale prices.Cells have grown in size as older equipment became available on the surplus market; ARCO Solar's original panels used cells with 2 to 4  inch (51 to 100  mm) diameter. Panels in the 1990s and early 2000s generally used 5  inch (125  mm) wafers, and since 2008 almost all new panels use 6  inch (150  mm) cells. This material has less e fficiency, but is less expensive to produce in bulk. The widespread introduction of  flat screen televisions  in the late 1990s and early 2000s led to the wide availability of large sheets of high-quality glass, used on the front of the panels. In terms of the cells themselves, there has been only one major change. During the 1990s, polysilicon cells became increasingly popular.These cells offer less efficiency than their monosilicon counterparts, but they are grown in large vats that greatly reduce the cost of production. By the mid-2000s, poly was dominant in the low-cost panel market, but more recently a variety of factors has pushed the higher performance mono back into widespread use. CURRENT EVENTS Other technologies have tried to enter the market. First Solar  was briefly the largest panel manufacturer in 2009, in terms of yearly power produced, using a thin-film cell sandwiched between two layers of glass. Since then silicon panels reasserted their dominant position bo th in terms of lower prices and the rapid rise of Chinese manufacturing, resulting in the top producers being Chinese.By late 2011, efficient production in China, coupled with a drop in European demand due to budgetary turmoil had dropped prices for crystalline solar-based modules further, to about $1. 09[13]  per watt in October 2011, down sharply from the price per watt in 2010. A more modern process, mono-like-multi, aims to offer the performance of mono at the cost of poly, and is in the process of being introduced in 2012[citation needed]. APPLICATIONS [pic] Polycrystalline  photovoltaic cells laminated to backing material in a module [pic] [pic] Polycrystalline photovoltaic cells Solar cells are often electrically connected and encapsulated as a  module. Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the emiconductor  wafers  from abrasion and impact due to wind-driven debris,  rain,  hail, etc . Solar cells are also usually connected in  series  in modules, creating an additive  voltage. Connecting cells in parallel will yield a higher current; however, very significant problems exist with parallel connections. For example, shadow effects can shut down the weaker (less illuminated) parallel string (a number of series connected cells) causing substantial power loss and even damaging the weaker string because of the excessive  reverse bias  applied to the shadowed cells by their illuminated partners. Strings of series cells are usually handled independently and not connected in parallel, special paralleling circuits are the exceptions.Although modules can be interconnected to create an  array  with the desired peak DC voltage and loading current capacity, using independent MPPTs (maximum power point trackers) provides a better solution. In the absence of paralleling circuits, shunt diodes can be used to reduce the power loss due to shadowing in arrays with ser ies/parallel connected cells. To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connected  photovoltaic systems); in stand-alone systems, batteries are used to store the energy that is not needed immediately. Solar panels can be used to power or recharge portable devices. THEORYThe solar cell works in three steps: 1. Photons  in  sunlight  hit the solar panel and are absorbed by semiconducting materials, such as silicon. 2. Electrons  (negatively charged) are knocked loose from their atoms, causing an electric potential difference. Current starts flowing through the material to cancel the potential and this electricity is captured. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction. 3. An array of solar cells converts solar energy into a usable amount of  direct current  (DC) electricity. EFFICIENCY Solar panels on the Internatio nal Space Station absorb light from both sides.These Bifacial cells are more efficient and operate at lower temperature than single sided equivalents. The efficiency of a solar cell may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies. A solar cell usually has a voltage dependent efficiency curve, temperature coefficients, and shadow angles. Due to the difficulty in measuring these parameters directly, other parameters are measured instead: thermodynamic efficiency, quantum efficiency,integrated quantum efficiency, VOC ratio, and fill factor.Reflectance losses are a portion of the quantum efficiency under â€Å"external quantum efficiency†. Recombination losses make up a portion of the quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of the quantum efficiency, VOC ratio. The fill factor is defined as the ratio of the actual maximum obtainable power to the product of the open circuit voltage and short circuit current. This is a key parameter in evaluating the performance of solar cells. Typical commercial solar cells have a fill factor ; 0. 70. Grade B cells have a fill factor usually between 0. 4 to 0. 7. 14] Cells with a high fill factor have a low equivalent series resistance and a high equivalent shunt resistance, so less of the current produced by the cell is dissipated in internal losses. Single p–n junction crystalline silicon devices are now approaching the theoretical limiting power efficiency of 33. 7%, noted as the Shockley–Queisser limit in 1961. In the extreme, with an infinite number of layers, the corresponding limit is 86% using concentrated sunlight. [pic] Reported timeline of solar cell energy conversion efficiencies (from National Renewable Energy Laboratory (USA)) MATERIALS [pic] [pic] The  Shockley-Queisser limit  for the theoretical maximum efficiency of a solar cell. Semiconductors with  band gapbetween 1 and 1. eV, or near-infrared light, have the greatest potential to form an efficient cell. (The efficiency â€Å"limit† shown here can be exceeded by  multijunction solar cells. ) Various materials display varying efficiencies and have varying costs. Materials for efficient solar cells must have characteristics matched to the spectrum of available light. Some cells are designed to efficiently convert wavelengths of solar light that reach the Earth surface. However, some solar cells are optimized for light absorption beyond Earth's atmosphere as well. Light absorbing materials can often be used in  multiple physical configurations  to take advantage of different light absorption and charge separation mechanisms.Materials presently used for photovoltaic solar cells include  monocrystalline silicon,  polycrystalline sil icon,  amorphous silicon,  cadmium telluride, andcopper indium selenide/sulfide. [25][26] Many currently available solar cells are made from bulk materials that are cut into  wafers  between 180 to 240  micrometers thick that are then processed like other semiconductors. Other materials are made as  thin-films  layers, organic  dyes, and organic  polymers  that are deposited on  supporting substrates. A third group are made from  nanocrystals  and used as  quantum dots  (electron-confined  nanoparticles). Silicon remains the only material that is well-researched in both  bulkand  thin-film  forms. CRYSTALLINE SILICON [pic]Basic structure of a silicon based solar cell and its working mechanism. By far, the most prevalent bulk material for solar cells is crystalline silicon (abbreviated as a group as c-Si), also known as â€Å"solar grade silicon†. Bulk silicon is separated into multiple categories according to crystallinity and crystal siz e in the resulting ingot, ribbon, orwafer. 1. monocrystalline silicon (c-Si): often made using the Czochralski process. Single-crystal wafer cells tend to be expensive, and because they are cut from cylindrical ingots, do not completely cover a square solar cell module without a substantial waste of refined silicon. Hence most c-Si panels have uncovered gaps at the four corners of the cells. 2. olycrystalline silicon, or multicrystalline silicon, (poly-Si or mc-Si): made from cast square ingots — large blocks of molten silicon carefully cooled and solidified. Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient. United States Department of Energy data show that there were a higher number of polycrystalline sales than monocrystalline silicon sales. 3. ribbon silicon is a type of polycrystalline silicon: it is formed by drawing flat thin films from molten silicon and results in a polycrystalline structure. These cells have lower efficiencies than poly-Si, but save on production costs due to a great reduction in silicon waste, as this approach does not require sawing from ingots. 4. ono-like-multi silicon: Developed in the 2000s and introduced commercially around 2009, mono-like-multi, or cast-mono, uses existing polycrystalline casting chambers with small â€Å"seeds† of mono material. The result is a bulk mono-like material with poly around the outsides. When sawn apart for processing, the inner sections are high-efficiency mono-like cells (but square instead of â€Å"clipped†), while the outer edges are sold off as conventional poly. The result is line that produces mono-like cells at poly-like prices. Analysts have predicted that prices of polycrystalline silicon will drop as companies build additional polysilicon capacity quicker than the industry's projected demand. On the other hand, the cost of producing upgraded metallurgical-grade silicon, also known as UMG Si, can potentially be one- sixth that of makingpolysilicon.Manufacturers of wafer-based cells have responded to high silicon prices in 2004–2008 prices with rapid reductions in silicon consumption. According to Jef Poortmans, director of IMEC's organic and solar department, current cells use between eight and nine grams of silicon per watt of power generation, with wafer thicknesses in the neighborhood of 0. 200 mm. At 2008 spring's IEEEPhotovoltaic Specialists' Conference (PVS'08), John Wohlgemuth, staff scientist at BP Solar, reported that his company has qualified modules based on 0. 180 mm thick wafers and is testing processes for 0. 16 mm wafers cut with 0. 1 mm wire. IMEC's road map, presented at the organization's recent annual research review meeting, envisions use of 0. 08 mm wafers by 2015. Gallium arsenide multijunction:High-efficiency multijunction cells were originally developed for special applications such as satellites and space exploration, but at present, their use in terrestrial conc entrators might be the lowest cost alternative in terms of $/kWh and $/W. [35] These multijunction cells consist of multiple thin films produced using metalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconductors: GaAs, Ge, and GaInP2. [36] Each type of semiconductor will have a characteristic band gap energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum.Combinations of semiconductors are carefully chosen to absorb nearly the entire solar spectrum, thus generating electricity from as much of the solar energy as possible. GaAs based multijunction devices are the most efficient solar cells to date. In October 15, 2012, triple junction metamorphic cell reached a record high of 44%. [37] Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge p–n junctions, are seeing demand rapidly rise. Between December 2006 and December 2007, the cost of 4N gallium metal rose from about $350 per kg to $680 per kg. Additionally, germanium metal prices have risen substantially to $1000–1200 per kg this year.Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry. Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time World Solar Challenge winners Nuna in 2003, 2005 and 2007, and also by the Dutch solar carsSolutra (2005), Twente One (2007) and 21Revolution (2009). The Dutch Radboud University Nijmegen set the record for thin film solar cell efficiency using a single junction GaAs to 25. 8% in August 2008 using only 4  µm thick GaAs layer which can be transferred from a wafer base to glass or pl astic film. THIN FILMS [pic]Market share of the different PV technologies  In 2010 the market share of thin film declined by 30% as thin film technology was displaced by more efficient crystalline silicon solar panels (the light and dark blue bars). Thin-film technologies reduce the amount of material required in creating the active material of solar cell. Most thin film solar cells are sandwiched between two panes of glass to make a module. Since silicon solar panels only use one pane of glass, thin film panels are approximately twice as heavy as crystalline silicon panels. The majority of film panels have significantly lower conversion efficiencies, lagging silicon by two to three percentage points. 31]  Thin-film solar technologies have enjoyed large investment due to the success of First Solar and the largely unfulfilled promise of lower cost and flexibility compared to wafer silicon cells, but they have not become mainstream solar products due to their lower efficiency and corresponding larger area consumption per watt production. Cadmium telluride  (CdTe),  copper indium gallium selenide  (CIGS) and  amorphous silicon  (A-Si) are three thin-film technologies often used as outdoor photovoltaic solar power production. CdTe technology is most cost competitive among them. [32]  CdTe technology costs about 30% less than CIGS technology and 40% less than A-Si technology in 2011. CADMIUM TELLURIDE SOLAR CELLA cadmium telluride solar cell uses a cadmium telluride (CdTe) thin film, a  semiconductor  layer to absorb and convert sunlight into electricity. Solarbuzzhas reported that the lowest quoted thin-film module price stands at US$0. 84 per  watt-peak, with the lowest crystalline silicon (c-Si) module at $1. 06 per watt-peak. [33] The  cadmium  present in the cells would be toxic if released. However, release is impossible during normal operation of the cells and is unlikely during ? res in residential roofs. [34]  A square meter of CdTe contains approximately the same amount of Cd as a single C cell  Nickel-cadmium battery, in a more stable and less soluble form. [34]COPPER INDIUM GALLIUM SELENIDE Copper indium gallium selenide (CIGS) is a  direct band gap  material. It has the highest efficiency (~20%) among thin film materials (see  CIGS solar cell). Traditional methods of fabrication involve vacuum processes including co-evaporation and sputtering. Recent developments at  IBM  and  Nanosolar  attempt to lower the cost by using non-vacuum solution processes. GALLIUM ARSENIDE MULTIJUNCTION High-efficiency multijunction cells were originally developed for special applications such as  satellites  and  space exploration, but at present, their use in terrestrial concentrators might be the lowest cost alternative in terms of $/kWh and $/W. 35]  These multijunction cells consist of multiple thin films produced using  metalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconductors:  GaAs,  Ge, and  GaInP2. [36]  Each type of semiconductor will have a characteristic  band gap  energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb  electromagnetic radiation  over a portion of the spectrum. Combinations of semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible. GaAs based multijunction devices are the most efficient solar cells to date.In October 15, 2012, triple junction metamorphic cell reached a record high of 44%. [37] Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge p–n junctions, are seeing demand rapidly rise. Between December 2006 and December 2007, the cost of 4N gallium metal rose from about $350 per kg to $680 per kg. Additionally, germanium metal p rices have risen substantially to $1000–1200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry.Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time  World Solar Challenge  winners  Nuna  in 2003, 2005 and 2007, and also by the Dutch solar carsSolutra (2005),  Twente One (2007)  and 21Revolution (2009). The Dutch  Radboud University Nijmegen  set the record for thin film solar cell efficiency using a single junction GaAs to 25. 8% in August 2008 using only 4  Ã‚ µm thick GaAs layer which can be transferred from a wafer base to glass or plastic film. Light-absorbing dyes (DSSC) Dye-sensitized solar cells  (DSSCs) are made of low-cost materials and do not need elaborate equipment to manufacture, so they can be made in a  DIY  fashion, possibly allowing players to produce more of this type of solar cell than others. In bulk it should be significantly less expensive than older  solid-state  cell designs.DSSC's can be engineered into flexible sheets, and although its  conversion efficiency  is less than the best  thin film cells, its  price/performance ratio  should be high enough to allow them to compete with  fossil fuel electrical generation. Typically a  ruthenium  metalorganic  dye  (Ru-centered) is used as a  monolayer  of light-absorbing material. The dye-sensitized solar cell depends on a  mesoporous  layer of  nanoparticulate  titanium dioxide  to greatly amplify the surface area (200–300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from the  light absorbing dye  are passed on to the  n-type  TiO2, and the holes are absorbed by an  electrolyte  on the other side of the dye.The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows a more flexible use of materials, and is typically manufactured by  screen printing  or use of  Ultrasonic Nozzles, with the potential for lower processing costs than those used for  bulk  solar cells. However, the dyes in these cells also suffer from  degradation  under heat and  UV  light, and the cell casing is difficult to  seal  due to the solvents used in assembly. In spite of the above, this is a popular emerging technology with some commercial impact forecast within this decade. The first commercial shipment of DSSC solar modules occurred in July 2009 from G24i Innovations. [38] Quantum Dot Solar Cells (QDSCs)Quantum dot solar cells  (QDSCs) are based on the Gratzel cell, or  dye-sensitized solar cell, architecture but employ low  band gap  semiconductor  nanoparticles, fabricated with such small crystallite sizes th at they form  quantum dots  (such as  CdS,  CdSe,  Sb2S3,  PbS, etc. ), instead of organic or organometallic dyes as light absorbers. Quantum dots (QDs) have attracted much interest because of their unique properties. Their size quantization allows for the  band gap  to be tuned by simply changing particle size. They also have high  extinction coefficients, and have shown the possibility of  multiple exciton generation. [39] In a QDSC, a  mesoporous  layer of  titanium dioxide  nanoparticles forms the backbone of the cell, much like in a DSSC.This TiO2  layer can then be made photoactive by coating with semiconductor quantum dots using  chemical bath deposition,  electrophoretic deposition, or successive ionic layer adsorption and reaction. The electrical circuit is then completed through the use of a liquid or solid  redox couple. During the last 3–4 years, the efficiency of QDSCs has increased rapidly[40]  with efficiencies over 5% show n for both liquid-junction[41]  and solid state cells. [42]  In an effort to decrease production costs of these devices, the  Prashant Kamat  research group[43]  recently demonstrated a solar paint made with TiO2  and CdSe that can be applied using a one-step method to any conductive surface and have shown efficiencies over 1%. [44] Organic/polymer solar cellsOrganic solar cells  are a relatively novel technology, yet hold the promise of a substantial price reduction (over thin-film silicon) and a faster return on investment. These cells can be processed from solution, hence the possibility of a simple roll-to-roll printing process, leading to inexpensive, large scale production. Organic solar cells and  polymer solar cells  are built from thin films (typically 100  nm) of  organic semiconductors  including polymers, such as  polyphenylene vinylene  and small-molecule compounds like copper phthalocyanine (a blue or green organic pigment) and  carbon ful lerenes  and fullerene derivatives such as  PCBM. Energy conversion efficiencies achieved to date using conductive polymers are low compared to inorganic materials.However, it has improved quickly in the last few years and the highest  NREL  (National Renewable Energy Laboratory) certified efficiency has reached 8. 3% for the  Konarka  Power Plastic. [45]  In addition, these cells could be beneficial for some applications where mechanical flexibility and disposability are important. These devices differ from inorganic semiconductor solar cells in that they do not rely on the large built-in electric field of a PN junction to separate the electrons and holes created when photons are absorbed. The active region of an organic device consists of two materials, one which acts as an electron donor and the other as an acceptor.When a photon is converted into an electron hole pair, typically in the donor material, the charges tend to remain bound in the form of an  exciton, a nd are separated when the exciton diffuses to the donor-acceptor interface. The short exciton diffusion lengths of most polymer systems tend to limit the efficiency of such devices. Nanostructured interfaces, sometimes in the form of bulk heterojunctions, can improve performance. [46] In 2011, researchers at the Massachusetts Institute of Technology and Michigan State University developed the first highly efficient transparent solar cells that had a power efficiency close to 2% with a transparency to the human eye greater than 65%, achieved by selectively absorbing the ultraviolet and near-infrared parts of the spectrum with small-molecule compounds. 47]  [48]Researchers at UCLA more recently developed an analogous polymer solar cell, following the same approach, that is 70% transparent and has a 4% power conversion efficiency. [49]  The efficiency limits of both opaque and transparent organic solar cells were recently outlined. [50]  [51]  These lightweight, flexible cells can be produced in bulk at a low cost, and could be used to create power generating windows. Silicon thin films Silicon thin-film cells  are mainly deposited by  chemical vapor deposition  (typically plasma-enhanced, PE-CVD) from  silane  gas and  hydrogen  gas. Depending on the deposition parameters, this can yield:[52] 1. Amorphous silicon  (a-Si or a-Si:H) 2. Protocrystalline  silicon or 3. Nanocrystalline silicon  (nc-Si or nc-Si:H), also called microcrystalline silicon.It has been found that protocrystalline silicon with a low volume fraction of nanocrystalline silicon is optimal for high open circuit voltage. [53]  These types of silicon present dangling and twisted bonds, which results in deep defects (energy levels in the bandgap) as well as deformation of the valence and conduction bands (band tails). The solar cells made from these materials tend to have lower  energy conversion efficiency  than  bulk  silicon, but are also less expensive to p roduce. The  quantum efficiency  of thin film solar cells is also lower due to reduced number of collected charge carriers per incident photon. An amorphous silicon (a-Si) solar cell is made of amorphous or microcrystalline silicon and its basic electronic structure is the  p-i-n  junction. -Si is attractive as a solar cell material because it is abundant and non-toxic (unlike its CdTe counterpart) and requires a low processing temperature, enabling production of devices to occur on flexible and low-cost substrates. As the amorphous structure has a higher absorption rate of light than crystalline cells, the complete light spectrum can be absorbed with a very thin layer of photo-electrically active material. A film only 1 micron thick can absorb 90% of the usable solar energy. [54]  This reduced material requirement along with current technologies being capable of large-area deposition of a-Si, the scalability of this type of cell is high.However, because it is amorphous, i t has high inherent disorder and dangling bonds, making it a bad conductor for charge carriers. These dangling bonds act as recombination centers that severely reduce the carrier lifetime and pin the Fermi energy level so that doping the material to n- or p- type is not possible. Amorphous Silicon also suffers from the Staebler-Wronski effect, which results in the efficiency of devices utilizing amorphous silicon dropping as the cell is exposed to light. The production of a-Si thin film solar cells uses glass as a substrate and deposits a very thin layer of silicon by  plasma-enhanced chemical vapor deposition  (PECVD).A-Si manufacturers are working towards lower costs per watt and higher conversion efficiency with continuous research and development on  Multijunction solar cells  for solar panels. Anwell Technologies Limited  recently announced its target for mul

Empowerment of the theatre Dissertation Example | Topics and Well Written Essays - 3750 words

Empowerment of the theatre - Dissertation Example They are not only fulfilling, but play a leading role in enhancing the cultural wellbeing of a given population. When explored optimally, it is rewarding and satisfying both at an individual and community level. As the global environment becomes technologically advanced, this field of specification is increasingly exploring technological advancements to its advantage. Currently, technology is at the centre stage of the field of theatre. Just like other fields of social, cultural and economic importance, the field of theatre arts require empowerment and support in order to thrive. Empowerment in this regard involves financial, infrastructural and moral support. Undoubtedly, there are unique talents within the population that can be explored for economic gain. However, to attain optimal outputs from this, it is imperative for the affected persons to be encouraged and empowered accordingly. At this point, it is worth appreciating that in order for talent to be recognized as such, it nee ds to be nurtured and developed to maturity. This cannot be realized without the help from different relative institutions and individual personalities with an interest in this field. Thus although theatre arts largely lead to personal fulfilment, affected individuals and theatre institutions need to be supported in different ways in order for both themselves and the community to benefit from their talents. The theatre needs to be empowered because it equally empowers populations in different ways. Through this, local communities are able to present their views to relevant stakeholders. It is used as a ‘societal mirror’ and in most cases, considered to be reflective of the needs of the local populations. Through this, locals are able to articulate their views accordingly. The fact that they can make an impact on societal decision making cannot be disputed. Thus since theatre is an important community empowerment tool, it needs to be empowered too. Background to the Stud y Theatre is an artistic field that has gained great importance in the social scene in the recent past. It assumes different forms including drama, video productions and music amongst others. In his study, Rohd (1998, p. 63) indicates that theatre is a field of specification that has its roots in the cultural conceptions of global populations. Thus in most instances, relative presentations are reflective of the culture of the respective populations. Increasingly, this field has been explored for economic gains. It lies in the entertainment docket and relative pieces of art are always customized to meet the needs, interests and requirements of the clients. In response to the growing needs of the population, the academic sphere has also contributed to the improvement of this field. In this respect, theatre arts are taught in learning institutions from a very elemental level. This is in a bit to enhance the ability of the students and sharpen their talents. In the long run, they produc e products of highest quality and which are very competitive in the market environment. To a great extent, this enables them to not only survive but to also thrive in the entertainment industry. At this point in time, exemplary performance in any field of specification requires an individual to be endowed with essential skills and knowledge. In addition to this, Thompson (2003, p. 52) argues that individuals need to have

Fire Protection Research Paper Example | Topics and Well Written Essays - 4000 words

Fire Protection - Research Paper Example By so doing, possible damages that can be caused by occurrences of fire are likely to be reduced. On the other side, Ashmore contends that training is one of the best approaches to the issue of fire protection. In fact it will be of no use to install gadgets which people have no idea on how to use them. The two articles though, seem to approach the issue fully through the suggestions they propose to the practice of fire protection (Beattie 63). Both can prove very effective if implemented appropriately. Spiker, Joseph E., and Daniel Della-Giustina. Fire Protection in Underground Coal Mines. Professional safety, Vol. 42(9), 2000, pp. 20-23. According to Spiker & Daniel (20) fires that affect coals, have posed a major threat to the mining industry. A lot of government revenue has been lost through coal fires hence there is a great need to come up with solutions to the problem. Some of the problems associated with these fires include closing of mines and loss of personnel. To overcome this challenge adequate training has to done to the mining industries (Spiker & Daniel 22). Consequently, industrial managers should advice their manpower on the activities to avoid when in the sites that may be contributing most to such fires. Studies done on the causes of these fires indicated that most of them happen due to the ignorance of the people working there. From this article one can understand the loss caused by coal fires, hence the need to prevent the fires. Spiker & Daniel (23) is specific in his approach to the issue as he focuses on coal fires. He takes a deep study into what the possible causes of the fires can be and the d amage they can cause. While Spiker & Daniel study coal fires, Beattie, studies fire protection in general. He asserts that fires are generally very destructive and can cause great damages if one had no preparedness. According to him companies should install fire extinguishers in every apartment to be in a position to fight the fires in case of any occurrence. Two articles though have the same overall goal of preventing and reducing fires (Spiker & Daniel, 23). They both aim at empowering individuals so that they can be in a position of knowing what to do in fire emergencies. Messner, Michael. Fundamentals of Fire Protection for the Safety Professional. Professional safety, Vol. 51(3), 2006, pp. 40-45. Under this article the basis of protecting fires ranging from chemistry to physics are discussed. Messner (40) explain what fire protection is, what it entails and the challenges associated with the practice. In fact it is very important for one to understand what it means by fire prot ection since the practice demands more than the title suggest. Company owners should have all the OSHA regulation rules on their tips so as to know how to handle issues related to fires (Messner, 42). This is because they are required to provide a safe

Causes of the American Revolution Essay Example | Topics and Well Written Essays - 750 words

Causes of the American Revolution - Essay Example The thirteen states in North America had demonstrated the urge to be independent. In 1763, Britain won the Indian and French wars; however, it devastated the economic power of Great Britain necessitating it to pass laws to its colonies in order to raise funds1. In 1764, Great Britain passed the infamous sugar act. This act intended to increase taxes levied on sugar production. Unfortunately, the British colonies were not willing to pay taxes to representatives of the British regime. In 1765, the British parliament added more insult to the thirteen colonies by introducing the Stamp Act2. The act intended to collect taxes from printed materials. The aim the tax was to generate money that Great Britain could use to protect, defend, and secure its colonies. The colonist reacted vehemently to these laws arguing that they were not party to laws enacted without their participation. The people and the businesses in the thirteen states viewed the taxes as an extortion and control over their b usinesses. The Boston Massacre wounded the relationship between the Americans and the British. In 1770, the British troops did not succeed in quelling the colonists who had expressed their rejection to the colonial rule3. The incident led to the death of both British soldiers and the Americans. The incident spurred the reaction of the Americans in openly rejecting the British rule. The American people developed the urge to send their representative in the British parliament. The American community had been on the receiving end for a long time. The laws made by the British parliament did not address the interest of the Americans necessitating their cry for representation. It is arguable that the laws enacted and presented for adoption by the British colonies suppressed the interest of these states. The Tea Act enacted by British in 1773 granted British East India Company the opportunity to monopolistic activities in North America4. While the act intended to boost the economic status of the British owned company, the choice was hurting because it sought to give economic benefit to the colonist. The monopolistic policy did not only benefit the British owned company, but promoted economic â€Å"crimes† to the Americans. The Americans had no choice in influencing the prices of their tea an act that they did not accept. Another spectacular event that took place in 1773 was Boston Tea party. Colonist disguised as the Indians participated in dumping tea overboard from ships at the Boston Harbor. This act met vehement reaction because it did not plunder the tea trade but also wounded the trade relationship. In 1774 the colonist closed the Boston Harbor and outlawed meeting that the American held in towns. The passing of the intolerable acts in 1774 received contrasting response from the thirteen states. Twelve out of the thirteen states met in Philadelphia in the same year, September to October. The resolution of the meeting was to reject products from Britain. The boycott was an economic spat because it influenced the production of the British industries. British suffered because America was one of the chief consumers of her products. It is also arguable that the economic power that it derived from trade was instrumental in influencing its interest in the colonial territories. In 1775, British troops visited Concord

Common Sense in Criminology Essay Example | Topics and Well Written Essays - 1500 words

Common Sense in Criminology - Essay Example All along this essay we endeavor to find answers to the problem arising from the shortcomings in common-sense understandings. At the end, a multidisciplinary and eclectic approach to this judicial matter will guide the way into a correct path in search for a coherent solution. There is a great deal of criminological theories to choose from. A wide spectrum of contradictory ideas lies behind those theories. But the knowledge of all of those theoretical assumptions can help us a lot in the task of assessing the evidence in any legal case. They can be especially necessary when we face the problem of common-sense limitations. These shortcomings can be reduced to a minimum through the appropriate use of adequate theoretical and methodological criteria. The role of criminological theories cannot be underestimated. Dr. ... heories present conflicting and contradictory positions, so the overall state of the theoretical corpus in Criminology is somewhat chaotic and confusing when we study the different fundamental tenets that many theoreticians hold as valid. Despite this complex theoretical panorama, all of the opposing theories have something to teach us about crime and its interpretation. These theories can give us some insight into the phenomenon of crime as Diane M. DeMelo (2003c) states: "Theories not only provide a framework for us to interpret the meanings of observed patterns but they help us to determine when these patterns are meaningful and when they are not." It is necessary to have a general knowledge of most of the criminological theories, so we can enhance the common-sense understandings improving our interpretation of the evidence in any fact assessment case. And we have to notice that common sense can mean many different things depending on the person who defines it. Many things are taken for granted in the name of common sense, so we have to be aware of the implications the definitions might have. Common sense is widely applied by everyone, and it can help us in simplifying the way we think and arrive at a conclusion when assessing facts and data. Schutz (2005) gives us an excellent idea of what common sense implies: "Common-sense thinking consists of a system of constructs or meanings for organizing the world and acting in it. Although each of our total set of constructs is unique (originating in our biographical situation), most of our common-sense constructs are socially derived. This shared intersubjective stock of knowledge and assumptions we develop through interactions allows us to engage in joint projects with other people". Even though it is very

Corporate governance Essay Example | Topics and Well Written Essays - 1250 words - 1

Corporate governance - Essay Example Many efforts were made to facilitate governance mechanisms. These are introduced by the law â€Å"relating to directors’ duties, supervision via non-executive directors, executive compensation agreements, managerial labour markets that respond to past performance, the market for corporate control, discipline exercised by creditors, and competitive product markets†. (Armour, Deakin & Konzelmann, 2003) The mutual result of the Report of Cadbury Committee (1992), the Greenbury Committee (1995) and the Hampel Committee (1997) was the Combined Code. The Code is voluntary. However companies are required to report compliance with the code or explain the reason why this compliance is not possible. The Code includes a number of principles which serve the ground for the measurement of governance practices of companies. The principles highlight the importance of non-executive directors and independent directors for supervision of executives. Other principle recommendations are separation of chairman and CEO positions with the board chairman monitoring the performance of management; functioning of audit committee with each board. (Black et.al., 1994) Along with these principles the code highlighted the importance of automatic re-election of directors at least every three years, remuneration and audit with a major role in each case for non-executive and independent directors and the disclosure to shareholders of policy concerning remuneration and of service contracts. (Armour, Deakin & Konzelmann, 2003) Committees recommendations are supported by key institutions - the Bank of England, the Confederation of British Industry, and the London Stock Exchange. That’s why the Combined Code proved to be effective in provision of high level of compliance. For example, in 1999 PIRC found that 87% of their sample of listed UK companies had separated the roles of Chairman and CEO, and 93% had

Women and Culture in the West Research Paper Example | Topics and Well Written Essays - 1500 words

Women and Culture in the West - Research Paper Example nce, mathematics, history, philosophy, Latin, Italian, French, Greek and German unlike the majority who preferred the girl child doing worsted work and practicing quadrilles. Their education was his responsibility (Aler, 2008). All these teachings resulted to Florence being intelligent and well educated which in some way shaped her to the nurse she came to be. Since Florence came from a wealthy background she was not expected to work. Her mother most of all deemed it best if she was to get married some day because she assumed that was her destiny. It was after a long emotional battle that tutors were eventually allowed to teach Florence mathematics over home duties. She was taught a number of subjects such as algebra, geometry and arithmetic’s. During her leisure time, Florence spent it tutoring children on this particular topics thus in the process enhancing her knowledge and having a wider scope on mathematics. She enjoyed being of service to others (Aler, 2008). Unlike these present times where people are strongly campaigning for the girl child to have a decent education and a lead a decent life where they are able to fend for themselves and be independent there was once upon a time an era where the English girls had little or no education at all, this was during the nineteenth century. Boys had an advantage over girls in the sense that parents were more willing to take them to private schools and pay more since there was no system of free schools until the 1880s. Girls of all ages had a disadvantage in relation to boys of the same age and level because of the depravity of education knowledge. Governesses taught the girls of the upper –class since they did not go to school at all but the funny part is that these very governesses who are supposed to be the source of enlightenment had no formal training. The objective of this strategy of the upper-class being taught at home was to alienate them from the lower classes as well as to keep them away from the

Does Each Country Have A Unique Style Of Leadership Essay

Does Each Country Have A Unique Style Of Leadership - Essay Example The unique style of leadership is useful in transforming the potential into reality. It is the ultimate action which brings into success all the current potentials that an organization and the allied people have into reality. Leadership is about changing the mindset of the people to accomplish the desired goals and to move the organization or the country forward. Nevertheless, it is important to explore the fact that there is no one best way of leadership. The need of every area is different and the style of leadership depends on various factors. An organization might be effective by following a democratic style of leadership and the other by the transformational approach. This is because the demographics of every country and organization are different with dissimilar objectives. Hence, the similar form of leadership might not be effective and lead to the failure of the organization. Furthermore, leadership is based on strong effective pillars which include commitment, character alon g with increasing the level of consciousness. Leadership is unique and effective only when it brings about desired results for the enrichment of the people. Leadership is about building interpersonal skills, competencies, along with influencing and building teams for the accomplishment of the desired level of standards. The uniqueness of leadership is of significance for the effective performance of an organization. The evaluation of the unique traits of the leaders can enable to reach a justified conclusion regarding whether each of these countries demonstrates a unique style of leadership.

Fr, Michael Porters Five Forces Analysis Coursework

Fr, Michael Porters Five Forces Analysis - Coursework Example The forces have been referred to a microenvironment in the framework. The businesses have to reassess the market place in case of any changes to the forces. On the other hand, it is also important to note that the level of profitability for the organizations may not be the same despite operating in the same industry. The five forces can also be classified as horizontal or vertical. The horizontal forces include threat of substitute products or services, threat of new entrants and industry rivalry. The vertical forces include the bargaining powers of suppliers and bargaining powers of customers. Porter five forces analysis plays an important role in terms of enabling the businesses to gain more profitability and stability. On the other hand, the government also uses the framework for the purposes of stabilizing the industries. This framework has is usually used by most of the companies that intent to enter a new market. The cycle wear industry that FLAB operates in faces a threat of new entrants since it is profitable. The government policies on the industry are not strict which makes it easy for new entrants to enter the market. The capital requirement is not too high although any new entrant in the market has to meet the demands of the cyclists including those with 60 inch waist. The entry barrier in the industry is high due to patent issues since different designs have to be made to satisfy the needs of the customers. However, despite the entry barriers, the exit barriers are low. The presence of high entry barriers and low exit barriers is an indication that the industry is profitable (Vining, 2011). In the industry, the customer loyalty is not a major issue considering that most of the companies are unable to provide the cyclewear for the people with up to 60 inch waist. The customers usually move from one company to the other in search of required products. The bargaining powers of the customers in the

Forensics as a Crime Scene Investigator Essay Example for Free

Forensics as a Crime Scene Investigator Essay Thesis Statement Forensic is a field of that deals with psychology and the law. Forensic is defined as the intersection of psychology and the law. Forensics is the application of science to questions which are of interest to the legal system. For example, forensic pathology is the study of the human body to determine cause and manner of death. Introductory Paragraph Forensics will be my area of study where I will have to determine the cause and manner of death. As a Crime Scene Investigator, I will be scouring a crime scene for evidence. This is a science, and a field that has a growing in importance. Michigan State University has the nation’s oldest and largest forensic science program. As a Crime Scene Investigator you have to collect, analyze, walk through a virtual crime scene where a murder has occurred, and estimate when the victim was murdered. Then construct a report dealing what I have uncovered and offer an estimated time of death. After I graduate from EVC University I will pursue a career as a Crime Scene Investigator. I will be in charge of investigating Crimes scenes, collecting and analyzing evidence and testifying in court in when needed. I will have to go through law enforcements organizations that have been trained or gone through special certification courses. As a CSI investigator I will be specializing in areas of forensic science. Crime Scene Investigators have to be able to collect and analyze evidence. CSI have to be able to work in a stressful environment hazardous work conditions. You must be available at all times no matter what time of the day. CSI have to perform technical forensic analysis. I will have to be thorough and accurate to document a crime scene including evidence that I have collected so that officers and attorneys can use that evidence for solving and prosecuting crimes. CSI has to work regular hours sometimes they have to work longer hours if not overnight to solve a crime scene. (Hineman, 2011) Crime Scene Investigators annual salary $55,040 which means they make $26.46 hour. Some agencies offer bonuses which mean that another $5,000 can be added to your salary. Some agencies require a four year degree but not all. CSI requires educational requirements in chemistry, and anatomy, and criminal law. (Hineman, 2011) References Merriam-Websters Dictionary with Thesaurus. (n.d.). Zane . Zane Publishing. Google. (n.d.). Retrieved from http://www.wikipedia.com Hineman, G. (2011, July 10). MSN. Retrieved from ehow.com: http://www.ehow.com/info_8715626_forensic_scene investigator-job description

Not Enough Drinking Water Essay Example for Free

Not Enough Drinking Water Essay Pop culture has recently become obsessed with trying to provide clean drinking water to those who do not have it. This is a pathetic issue to choose to fix. These poor people are a waste of space and need to learn how to fix their own problems instead of turning to the reach to fix them. Do you think the rich got rich by relying on other people? No. They found easy solutions to their difficult problems. People have wasted tons of money on giving these people clean water supplies when there are cheap solutions to get the job done. For one these people should just drink their own urine. It is full of vitamins and nutrients that at the time the body doesn’t need but will at a later date. It also would make an endless cycle and the people would always have a supply of it. Drinking urine would be almost completely free, all that would be needed would be some kind of bottle to collect and contain it in until it was needed again. With this solution every person would have their very own source of water and people would never have to fight over it or share supplies again. It would also teach people to become much more self-sufficient because they are supplying their own source of life. Another easy solution is to make the people of these very poor areas used to not having any water by contaminating the little supply they have and forcing them to become assimilated to their new way of life. This is a perfect example of natural selection, the most fit will survive and be able to reproduce while the rest will die off. This will cause future generations of people to be well adapted to having little water and let them live much longer. This would be completely cost free; the only thing that would need to be done is some mud will need to be thrown into the large sources of drinking water. Some people feel that giving these pathetic people drinking water or drilling wells will fix the problems but they won’t this will only make the problem worse by showing these people that they can always rely on other people. Giving them other ways to get safe water is a complete waste of time and money. The world needs to see this fact and ban together to follow cheaper easier and faster ways of helping these poor pathetic people.

The Ranque-Hilsch Vortex Tube

The Ranque-Hilsch Vortex Tube David Newson Abstract The Ranque-Hilsch vortex tube is a simple mechanical device often used for refrigeration in industrial manufacturing as it requires only a supply of compressed gas. Despite having no moving parts the vortex tube is able to separate the compressed gas into two separate streams – one hot and one cold with temperatures observed in the range of -5 to 55. Different explanations for the processes taking place within the device haven been proposed but there is currently no single accepted theory. A fundamental understanding of the vortex tube and the equipment has been reached and the groundwork has been laid for further experimental investigation and numerical computational fluid dynamic modelling. Introduction The Ranque-Hilsch vortex tube, often referred to simply as a vortex tube, is a mechanical device involving no moving parts that can be used to separate a stream of high pressure compressed gas into two lower pressure streams of varying temperatures. The cold stream is able to reach temperatures as low as -30 ºC whilst the hot stream can reach temperatures of up to 110  ºC [1]. First invented by French physicist G. Ranque in 1933 [2] the vortex tube was unpopular at the time due to its low efficiency and the idea was discarded until 1946, when German engineer R. Hilsch took it upon himself to improve the design [3]. With increased efficiency the vortex tube became an effective and popular spot cooling device for laboratory equipment, cutting tools such as lathes and mills, and other industrial processes. Since then there has been numerous attempts to find ways to further increase its efficiency and fully understand the processes leading to the temperature separation. The processes taking place within the vortex tube are simple to observe, but more difficult to accurately explain and model. It begins with compressed gas entering the vortex tube tangentially through a swirl generator creating an initial vortex inside the tube with rotational speeds of up to 1,000,000 RPM. The vortex moves along the length of the tube until it reaches an adjustable valve allowing a fraction of the gas to escape. The remaining gas is forced back down the centre of the tube, creating a secondary vortex. This secondary vortex has a reduced diameter and is contained within the initial vortex and travels in the opposite direction back along the length of the tube. When the secondary vortex reaches the other end of the tube all remaining gas is expelled through an opening. While this is taking place, energy is transferred from the inner vortex to the outer vortex, causing the temperature of the outer vortex to increase, and the temperature of the inner vortex to decrease. As the gas from the outer, hotter vortex and the gas from the cooler, inner vortex are expelled at opposite ends of the tube the two streams of varied temperature can be directed as required and the ratio of the temperatures controlled by changing the amount of gas allowed to be expelled at the adjustable valve. Figure 1. Initial and secondary vortexes within a vortex tube [4] There are currently different explanations for the temperature separation within the vortex tube with no theory being conclusively proved. It is currently thought that the energy transferred between the vortexes is through friction of the two vortexes rotating against one another but it is unknown whether the gas within the tube experiences â€Å"solid body rotation†, where the angular velocities of the of both the inner and the outer vortexes are the same or if the two vortexes are rotating at different angular velocities. Further investigation into the speed of rotations of the vortexes within a Ranque-Hilsch Vortex Tube will provide greater understanding of the energy transfer. Equipment The experimental set up consisted of a Ranque-Hilsch Vortex Tube, two flow gauges that could be placed at positions A,B or C, two thermo couples, a gate valve and a pressure gauge positioned as shown on figure 2 below. Figure 2. Schematic of experimental setup The vortex tube was supplied by compressed air with a mains pressure of 6.6 bar with the gate valve used to control the pressures and flow rates into the vortex tube. The flow gauges used were rota meters with a range of 30-300 litres per minute. Rota meters are made of a tapered tube with a â€Å"float† inside that is lifted up by the drag force created by the flow of the liquid around it and pulled down by gravity. A higher flow rate increases flow speed and drag causing the float to be lifted higher up the tube, however, as the float is lifted higher up the tube the tube widens due to the taper and the drag force decreases until the float reaches its new equilibrium. The equilibrium can be found using the equation . (1) Where is the mass of the float, is acceleration due to gravity, is the density of the fluid, is the velocity of the object relative to the fluid, is the reference area and is the drag coefficient. With the float in equilibrium the flow rate can be read off scale at a specified point on the float. Due to the simple nature of rota meters they are affected by changes in pressure and temperature and the displayed numbers are only valid at atmospheric pressure and standard atmospheric pressure. Correcting for the effects of pressure (2) Pressures above atmospheric pressure allows greater capacity for a flow meter and the above equation is used to determine the actual flow rate at varying pressures. Correcting for the effects of temperature (3) Temperatures above standard atmospheric temperature decreases maximum flow rate and the above equation is used to determine the actual flow rate at varying temperatures. The flow gauges have an unknown impedance which has to be calculated in order to make sure placing them in the system doesn’t affect the measured pressures nor the fraction of gas expelled through the hot end valve. If it does affect the system knowing the impedance allows corrections to be calculated. The impedance is calculated by measuring the rate of flow through a single flow gauge as a function of pressure. Figure 3. Experimental set up to calculate flow gauge impedance The vortex tube itself has no moving parts and consists of very few pieces. Compressed gas is fed in through the air inlet and as it passes through the generator creates a vortex inside the spin chamber, the vortex propagates along the length of the tube with air exiting out both the hot end valve and the cold end cap. Figure 3. Schematic of Meech Vortex tube [5] The only interchangeable part of the vortex tube is the generator. The generators determine the volume of gas flow through the vortex tube and the fraction of the incoming air that exits in the cold stream – the cold fraction. The cold fraction may also be altered by adjusting the hot end valve. The total flow can be calculated using (4) Where PSIG is pounds per square inch gage. The cooling and heating power in BTUH (British Thermal Unit per Hour) can be found by using the following: For Cooling: (5) For Heating: (6) Where 1 = 0.293W, = cold fraction, = cold airflow, = hot airflow, = inlet pressure, = cold stream temperature, = hot stream temperature Results The impedance of the flow gauges were calculated by plotting flow against pressure and calculating the gradient. Figure 4. Calibration of flow gauges The gradient calculated from figure 4 is which equals The gradient was then used to calculate impedance using (7) This gives a value for the impedance of the flow gauges of acoustic ohms. Figure 5. Temperature of streams as function of pressure Figure 5 shows the relationship between the temperatures of the stream and the inlet pressure. The two trend lines intersect at 0 pressure at 23 which is the temperature of the compressed air before it entered the vortex tube. The gradient of the hot stream trend line is 8.3 and the gradient of the cold stream trend line is -7.8 0.05. This shows the temperature of the hot flow is increasing faster than the cold flow is decreasing suggesting a cold fraction of above 0.5. Figure 6. Flow rates as a function of pressure Figure 6 displays the flow rates at each of the 3 positions A,B and C from figure 2. The flow rate of the cold stream is higher than the flow rate of the hot stream confirming that the cold fraction is above 0.5 as proposed from the findings in figure 5. This figure demonstrates the corrections to the flow rate using equation (2) as before the equation is applied the measured flow rate in (green) is significantly lower than the measured flow rate out (cyan). After the correction is applied the measured flow in (magenta) is equal to the measured flow out. This is based on the assumption that the pressure at the flow gauge in position A is 6.6 bar – the pressure of the mains gas supply. Figure 7. Energy flow rates as a function of pressure Figure 7 shows the rates of flow of internal energy of the gas at points A,B and C calculated by combining the following equations (7) (8) Into (9) Where is pressure, is volume, is number of moles, is the molar gas constant, is temperature and is internal energy. From this figure it seems that no energy is lost from the system and it is simply transferred between the two flows of the gas. This is expected based on the previous result as internal energy is proportional to volume and the volumes of gas flowing in and out of the tube were constant. Discussion After much investigation the temperature and energy separation and rate of flow appear linear as a function of inlet pressure. This was not always the case as for a long period of time the volume of gas measured being expelled by the vortex tube was vastly larger than that being measured entering the tube and the rate of flows were not linear. However, after studying the equipment it was found that this was due to the flow gauges being effected by temperature and pressure. Once the raw data was corrected by taking into account for these varying conditions the data matched up to initial predictions and with far fewer anomalies. The temperature difference of the two streams was observed and; with a cold fraction greater than 0.5 the cold stream was measured to have a higher rate of flow but there was a greater temperature difference in the hot stream from the initial temperature of the gas. The current data suggests that the gas as a whole does not gain or lose any internal energy and that energy is only transferred between the gas from the cold stream to the hot stream, however, this is under the assumption that the pressure at the flow gauge in position A was constantly at 6.6 bar. If this is not the case a slight difference in pressure could reveal changes in the internal energy of the gas which could help explain the processes happening within the tube. Conclusion The equipment has been calibrated and raw data is able to be corrected to provide correct results. Temperature separation has been measured in the range of -5 to 55 with the rate of change of temperature corresponding to the cold fraction of the generator. The internal energy of the gas has been observed to remain constant; transferring only between the cold and the hot stream but there is scope to further investigate this. A basic understanding of the vortex tube has been reached and the groundwork has been laid for further investigation. With further sampling it is hoped the energy separation will be understood in greater detail and that the theory that the gas undergoes solid body rotation will be proved or disproved. Future work Future work will include experimental investigation continuing looking into the transfer of energy within the vortex tube including more detailed analysis of rate of energy flow examining whether the gas loses, gains or conserves internal energy. Different generators of varying efficiencies and cold fractions will be investigated and documented and an attempt to build a probe to determine whether the angular velocities within the vortex tube vary or are constant will take place. Aside from the experimental work computational fluid dynamics will be used to numerically explore the inner workings of the vortex tube by creating a two dimensional computational model of a vortex tube using COMSOL software using the k-ÃŽ µ model to simulate the temperature separation phenomenon. Figure x shows the temperatures of the hot and cold streams achieved by three different generators as a function of flow. The results show that the generators that produce the lowest temperatures have a lower flow rate, this is expected as there is a similar amount of energy separation for each of the generators and you can choose to have a smaller quantity of very cold gas or a larger quantity that is not as cold, or a compromise as desired. This is important as it makes the vortex tube more adaptable for industries using it for spot cooling and the temperature and flow rate can be adjusted as required. References [1] Meech air technology brochure. 2013. http://www.meech.com/resources/362/MAT.pdf [2] G. J. Ranque, â€Å"Experiments on Expansion in a Vortex with Simultaneous Exhaust of Hot and Cold Air,† Le Journal De Physique et le Radium (Paris), Vol. 4, 1933. [3] R. Hilsch, â€Å"The Use of the Expansion of Gases in a Centrifugal Field as Cooling Process,† Review of Scientific Instrument, Vol. 18, 1947. http://scitation.aip.org/docserver/fulltext/aip/journal/rsi/18/2/1.1740893.pdf?expires=1386863841id=idaccname=freeContentchecksum=2218A70412ADD7B3EFBAAC108BCC9ABE [4] http://en.wikipedia.org/wiki/Vortex_tube [5] Meech Static Eliminators Ltd www.meech.com