Why Solar Energy?

Why are power utilities all over the world suddenly becoming interested in developing electric power plants that use renewable resources ? Today, utlitiy companies all over the world produce most of their electricity using fossil fuels including oil, gas and coal. In general, the production of electricity from fossil fuels is much cheaper than renewable sources. However, there are several factors that are pushing the utilities to use more renewable resources: - Local and federal governments all over the world are passing laws that require utility companies to generate part of their electricity from renewable sources. For example, California utilities today get 12% of their power from renewable sources and they are under a mandate to increase to 20% by 2011 and 33% by 2020. - Due to the increased cost of oil and gas, many new companies are working on technologies to lower the cost of renewable energies and become competitive with fossil fuels. Utilities are open to implementing new technologies as part of their energy diversification plans.

Q: Where is the oldest, large scale solar enegy plant in the world and who developed it ? In the early 1980's, Luz International, an Israeli company based in Jerusalem, designed, built and financed 9 solar power plants in the Mojave Desert in California. The 9 plants generate 354 megawatts of power and are still in use today after 20 years.

Q: What technology was used in the large solar energy plants developed back in 1984 ? The nine Solar Electric Generating System (SEGS) power plants in Southern California are hybrid systems that use both solar power and fossil fuels. When the sun is shining, oil is heated in the piping of parabolic trough collectors. This in turn generates steam. During cloudy weather or at night, a natural gas heater serves as a back-up to generate steam. On an annual basis, these plants produce 70 percent of their electricity from solar energy and 30 percent from fossil energy.

Q: What company took over the maintenance and development when Luz closed ? Luz's patents were inherited and improved upon by the Solel Company of Beit Shemesh. In July 2007, California Pacific Gas and Electric Company announced that it entered into a landmark renewable energy agreement with Solel to purchase renewable energy from the Mojave Solar Park, to be constructed in California’s Mojave Desert. The project will deliver 553 megawatts of solar power, the equivalent of powering 400,000 homes, to PG&E’s customers in northern and central California.

Q: What new type of solar based systems are being developed today? Many companies around the world are busy working on developing new processes and technologies for large scale solar power plants. Three different technologies show promising results in small scale pilot tests: Sterling Engines, Solar Towers and Distributed Power Towers (DPT).

Q: What is a Sterling Engine ? The Stirling engine is a heat engine that was invented by Robert Stirling in 1816. It was developed in order to offer an alternative to the frequently explosive early steam engines. It is basically a closed cylinder containing a piston and helium, nitrogen or hydrogen gas. The gas is heated at one end by concentrated sunlight, and cooled at the other end by air or water. As the gas expands and cools with the movement of the piston, a generator can be driven to produce electricity. Stirling Energy Systems, Inc. (not Israeli) is developing a solar energy technology called a SunCatcher, that combines a mirrored concentrator dish with a high-efficiency Stirling engine specially designed to convert sunlight to electricity. SES has contracts to build and operate two large power projects with major Californian utilities for up to 1,750 megawatts (MW) of power, representing the world's two largest solar power contracts ever granted. Collectively, these contracts require up to 70,000 SunCatchers.

Q: What is a Solar Updraft Tower ? In a solar updraft tower air is heated in a very large circular greenhouse-like structure, and the resulting convection causes the hot air to rise and escape through a tall tower. The moving air drives turbines, which produce electricity. The generating ability of a solar updraft power plant depends primarily on two factors: the size of the collector area and chimney height.

Q: What is Distributed Power Towers (DPT) ? Brightsource Energy (Israeli Luz II) is developing DPT technology in the Isareli Negev desert.The system consisits of a number of solar clusters, each of which includes a power tower surrounded 360 degrees by an array of heliostats. Heliostats are flat, glass mirrors which track the sun and reflect sunlight onto a receiver, which is located on the top of a power tower. Power towers are linked together by pipelines to a central location where electricity is generated and sent to a power grid. The DPT technology heats water to superheated steam at a temperature of 550 - 565 degrees. A high efficiency steam turbine converts the super heated steam to electricity, which is sent to the power grid. Source: Solar.co.il.