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 The Solar Car Book A complete kit for making a cool solar racecar. Everything is included: wheels, axles, motors, wires and a genuine one-volt solar cell. |
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Solar Thermal Energy See also:
Solar Chimney Solar Air Conditioning Solar Pond Salt Evaporation Pond Solar Furnace Solar Cooker Solar Still Solar Water Disinfection Solar Desalination Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation.[32] Water Heating
Solar hot water systems use sunlight to heat water. When sited in low latitudes (below 40 degrees), solar heating system can provide around 60 to 70% of domestic hot water use with temperatures up to 60 °C.[33] 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.[34] As of 2007, the total installed capacity of solar hot water systems is approximately 154 GW.[35] China is the world leader in the deployment of solar hot water with 70 GW installed as of 2006 and a long term goal of 210 GW by 2020.[36] Israel is the per capita leader in the use of solar hot water with 90% of homes using this technology.[37] 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.[38] Heating, Cooling and Ventilation
In the United States, heating, ventilation, and air conditioning (HVAC) systems account for over 25% (4.75 EJ) of the energy used in commercial buildings and nearly 50% (10.1 EJ) of the energy used in residential buildings.[39][29] Solar heating, cooling, and ventilation technologies can be used to offset a portion of this energy. Thermal mass, in the most general sense, is any material that has the capacity to store heat. In the context of solar energy, thermal mass materials are used to store heat from the Sun. Common thermal mass materials include stone, cement, and water. These materials have historically been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during the day and radiating their stored heat to the cooler atmosphere at night, but they can also be used in cold temperate areas to maintain warmth. The size and placement of thermal mass should consider several factors such as climate, daylighting, and shading conditions. When properly incorporated, thermal mass can passively maintain comfortable temperatures without consuming energy. A solar chimney (or thermal chimney) 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 in a way that mimics greenhouses. These systems have been in use since Roman times and remain common in the Middle east. Deciduous trees and plants can be used to provide heating and cooling. When planted on the southern elevation of the building, the leaves can provide shade during the summer while the bare limbs allow light and warmth to pass during the winter. Process Heat
Concentrating solar technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat for commercial and industrial applications. The first commercial process heating project was the Solar Total Energy Project (STEP) in Shenandoah, Georgia where a field of 120 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory.[40] This system generated 400 kW of electricity, 3 MW of thermal energy in the form of steam, and had a thermal storage system which allowed for peak-load shaving. A prototype Scheffler reflector is currently being constructed in India for use in a solar crematorium.[41] 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. Evaporation ponds represent one of the largest commercial applications of solar energy in use today.[42] Clothes lines, clotheshorses, and clothes racks dry clothes through evaporation. These devices use wind and sunlight instead of electricity or natural gas. Florida legislation specifically protects the 'right to dry' and similar solar rights legislation has been passed in Utah and Hawaii.[43] Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise the incoming air temperature up to 22 °C and deliver outlet temperatures of 45-60 °C.[44] The short payback period of transpired collectors (3 to 12 years) makes them a more cost-effective alternative to glazed collection systems.[44] As of 2003, over 80 systems with a combined collector area of 35,000 m² had been installed worldwide,[22] including an 860 m² collector in Costa Rica used for drying coffee beans and a 1300 m² collector in Coimbatore, India, used for drying marigolds.[22] Cooking
Solar cookers use sunlight for cooking, drying and pasteurization. Solar cooking offsets fuel costs, reduces demand for fuel or firewood, and improves air quality by reducing the generation of smoke. The simplest type of solar cooker is the box cooker first built by Horace de Saussure in 1767. A basic box cooker consists of an insulated container with a transparent lid. These cookers can be used effectively with partially overcast skies and will typically reach temperatures of 50-100 °C.[45][46] Concentrating solar cookers use reflectors to concentrate light on a cooking container. The most common reflector geometries are flat plate, disc and parabolic trough type. These designs reach temperatures up to 315 °C but require direct light to function properly and must be repositioned to track the Sun.[46] The solar bowl is a unique concentrating technology used by the Solar Kitchen in Auroville, India that uses a stationary spherical reflector. This reflector focuses light along a line perpendicular to the sphere's surface and a computer control system moves the receiver to intersect this line. Steam is produced in the solar bowl's receiver at temperatures reaching 150 °C and then used for process heat in the kitchen.[47] 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 °C and have a fixed focal point which improves the ease of cooking.[48] The world's largest Scheffler reflector system in Abu Road, Rajasthan, India is capable of cooking up to 35,000 meals a day.[49] By early 2008, over 2,000 large Scheffler cookers had been built worldwide.[50] Desalination and Disinfection
Solar distillation is the production of potable water from saline or brackish water using solar energy. The first recorded use was by 16th century Arab alchemists.[51] In 1589, Giambattista della Porta distilled water from crushed leaves.[51] The first large-scale solar distillation project was constructed in 1872 in the Chilean mining town of Las Salinas.[52] This 4,700 m² still could produce up to 22,700 L per day and operated for 40 years.[52] Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick and multiple effect.[51] These stills can operate in passive, active or hybrid modes. Double slope stills are the most economic for decentralized domestic purposes while active multiple effect units are more suitable to large-scale applications.[51] Solar water disinfection (SODIS) is a method of disinfecting water by exposing water-filled plastic PET bottles to several hours of sunlight.[53] Exposure times vary according weather and climate from a minimum of six hours to two days during fully overcast conditions.[54] SODIS is usually applied at the household level and is recommended by the World Health Organization as a viable method for household water treatment and safe storage.[55] Over two million people in developing countries use SODIS for their daily drinking water needs.[54] NotesThis article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "Solar Energy" |
