Solar Electricity

Collectors One-Sun vs Many Suns One-sun is what you get when standing directly under the midday sun Three suns, through a looking glass, will start a fire A thousand suns will melt steel Even in a Rain Forest in Washington  Photovoltaics (PV): One-sun Rooftop or ground-mounted Stationary or tracking Concentrators: Many suns

PV Arrays Rooftop Ground-mounted Stationary Tracking

PV Capacity World Capacity in 2011: 40,000 MW (1 Quad would require 200,000 MW & 1,500 hours of sun per year)

Concentrators Line Focus Troughs 320 acres in Nevada Point Focus Heliostats (Power Towers) Dishes CPV (Concentrator PV)

The first commercial solar power plant in the US 354 MW array in the Mojave Desert: Since 1984 Provides power to LA via Southern California Edison Kramer Junction

Archimedes’ Heliostats Legend has it that by focusing numerous bronze shields onto a sail, Archimedes set fire to a Roman ship in 212 BC He was subsequently killed by a Roman soldier That was the first solar concentrator known to history The first heliostat array in US 1981: Solar One, Barstow, CA, 10 MW

The First Concentrator IPO BrightSource has filed for a public offering 392 MW project in Nevada is under construction in partnership with NRG and Bechtel ($5.60 per watt) 1,300 MW contracted with Southern California Edison 1,300 MW contracted with Pacific Gas & Electric BrightSource has raised over $500 million to date Google and Alstom are investors Federal loan guarantee of $1.6 billion

The Next Generation Concentrator Photovoltaics (CPV) “By using optical concentrators to focus the solar radiation onto solar cells, the cell area, and consequently cell cost can be reduced by a factor of up to 1000.” Bob McConnell, NREL 28 MW installed: 689 MW under construction Source: GTM Research Soitec bought Concentrix Solar which has built a 25-MW manufacturing facility in Germany SolFocus has installed 3 MW in California, Hawaii, Mexico, Italy, Spain and Australia 5 MW Amonix system in NM

The Balance Sheet Troughs Tried and true, i.e., the most bankable solar technology Most time in the field 354 MW in Kramer Junction, CA since 1984 Heliostats Higher temperature steam is better for conventional utility turbines. Uses molten salts for heat storage. Dishes Highest efficiency Can cogenerate Heat Nothing scales like a dish

Solar’s Core Competence . . . is Heat & Light, not Power 200,000 thermal MW worldwide 100,000 MWt in China – hot water AC(CA + TX) = PV Air conditioning market in California & Texas = worldwide PV market AC runs on chillers fed by solar steam Solving the utility industry’s biggest problem (ie, peak power demand) at the lowest possible cost Subsidies Don’t Scale: Where would the market for solar electricity be without Germany’s Feed-in Tariff program? There is a compelling niche for PV, though . . .

PV4EV Electricity from sunlight 150 kW per acre & 2,000 hours of sun per year = 300,000 kWh per year (at 4 miles per kWh) = 1.2 million miles per acre per year 100 cars: 6 cents per mile (at 25 cents per kWh: price will go down) Ethanol from Corn in Iowa 150 bushels per acre yield 450 gallons (at 22 miles per gallon) = 10,000 miles per acre per year 1 car: 16 cents per mile (at $3.50 per gallon: price will likely rise)

PV: Cents per kWh 2011 Without subsidies (Rooftop < 30 kW) Source: Renewable Energy World