Solar Energy Summary

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Summary Solar technology can be used for space heating and cooling, to generate electricity, or in various industrial and scientific applications such as drying, desalination, and manufacturing. It also can provide power to operate electrical appliances, and for telecommunication and lighting in remote areas. For solar energy to capture a major utility market share, large power plants with capacities comparable to a coal or nuclear plant in the range of 100-200 MW must be developed. The major drawback of solar energy is the diffuse nature of sunlight that requires a large surface area for capturing 24 Fairley, P, “Solar on the Cheap,” Technology Review, January-February 2002. Solar Sail FYI ... Its time to set sail for the stars ~ Carl Sagan Did you know that solar light can exert a gentle pressure just like water squirting out of a nozzle onto a plate? A team of Russian and American scientists have pioneered Cosmos-1, the first solar sail spacecraft which uses the impact of light particles or photons off of a reflecting surface to propel a spacecraft without heavy and expensive onboard fuel sources. Sunlight pressure is enough to accelerate the spacecraft at the rate of 100 mph a day. That doesn’t sound like much, but it can quickly add up over time. The effort opens a new chapter in space travel, offering a hope for future interplanetary missions. The first such spacecraft was launched on June 21st, 2005 from a Russian submarine in the Arctic Barents Sea. Unfortunately, the spacecraft was lost during the launch and experiment had to be postponed. Source: Matloff, G. L., Deep Space Probes: To the Outer Solar System and Beyond, Springer-Verlag New York, LLC, 2005. 2nd edition. 237 Chapter 10 - Solar Energy enough light. Another problem is that solar energy is intermittent, available only during daylight and in favorable atmospheric conditions. One way to address this difficulty is to store the power in large, bulky, and expensive batteries. Another is to design a pumping storage water facility that stores water in an elevated reservoir during the day and releases it downhill to turn a water turbine and a generator as needed. Many homes use a backup system to supplement their primary solar systems when necessary. Compared to current PV technologies with typical efficiencies of 5-17%, solar thermals are more efficient and can reach efficiencies of up to 30%. Unlike solar concentrating technologies that rely on direct radiation, photovoltaic cells rely mainly on indirect radiation and therefore can be used in areas with few hours of sunlight. Currently, none of the solar electric generating stations can compete economically with the low cost of electricity generation using conventional coal and nuclear power plants. Both the capital and the operating costs are much higher, and the solar stations take up a much larger land area. Further research is needed to design larger heliostats and mirrors, as well as lenses with better optical properties and lower costs.