By Loyd Eskildson
'Plugging Into the Sun' by George Johnson in National Geographic, Sept. 2009 tells of 182,000 gently curved mirrors lined up in 760 arrays spread across 250 acres in Nevada that focus sunlight on long-steel pipes filled with circulating oil, heating it up to 750 degrees F. The steam generated produces as much as 64 MW (14,000 households). The plant belongs to Acciona (Spanish co.) and the mirrors were made in Germany. On a clear summer day with the sun directly overhead about 21% of the sun's energy is converted to electricity. A 30% federal tax credit helped offset its construction costs; motivation also came from a state deadline requiring utilities in Nevada to generate 20% of their power from renewable sources by 2015.
Efforts to further lower costs of solar power from steam generators such as this one include making 
mirrors from lightweight polymers instead of glass, and implementing methods of storing power for release at night. One way of accomplishing the latter is through using heat during the day to melt salt and store it until evening; this is already in operation at a site in Spain. The Solana Generating Station in Arizona (also Spanish built) will also use the same technology. When it goes online in 2012, three square miles of parabolic troughs will produce 280 MW for Phoenix-Tucson. (Heliostats operate similarly, except the sunlight is concentrated on a sphere and doesn't need long-steel pipes to transport the hot oil. The 10 MW demonstration facility at Daggett, CA. produced an eerie star-like glow when it was operated.)
Solar panels convert sunlight directly into electricity, but are expensive and provide efficiency of only 10-20%. Layering different semiconductors to capture different colors from sunlight has produced 41% efficiency - at a cost of $10,000/square cm. Thin-film solar cells (10% efficiency) cost about $1/watt - close to competitiveness with fossil fuel. Both the U.S. (Solar First) and China are competitive in manufacturing these films.
Germany is the largest producer of photovoltaic power in the world.
Man's power needs in 2020 are expected to reach 20 terawatts (TW; tera = trillion). The energy of sunshine on the Earth's land mass is 120 thousand TW. Experts believe renewable resources could provide 975,000 TWH, with 76% coming from solar. Solar now produces only 0.02% of the earth's total electricity. One expert believes the sun can provide two-thirds of U.S. electricity by 2050 for about $400 billion - including high-efficiency power transmission lines. Comparisons: Hoover Dam - 2,080 MW; Palo Verde Nuclear Plant (outside Phoenix - largest in the U.S.) - 3,200 MW. The West Texas 36,000 acre wind farm (one of the largest in the U.S.) will produce 600 MW of electricity beginning in 2011; its 240 turbines will be made in China, and receive a $450 million stimulus grant.
Loyd Eskildson is retired from a life of computer programming, teaching economics and finance, education and health care administration, and cross-country truck driving. He's now a reviewer for Basil & Spice.
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