Fight the gas prices

[kandrathe]

Oh, I agree about the problems with solar panels right now. I wasn't actually referring to solar energy, at least not in the way it's typically thought of. I saw a special on TV last week (I apologize, it was late and the details are a bit fuzzy) where somewhere in Europe (Spain was it?) they built a large array of mirrors to reflect the sunlight onto one focal point at the top of a large tower. If I recall correctly it was the direct heat used to boil water into steam, producing energy via a turbine. It's possible it was solar panels, but I doubt it.

Cheers,

Munk

PS. Now that I'm not a student and don't have papers to do, I end up reading/watching tid bits of information. On NASA TV they were talking about advances in Solar Panels. That the ones used on Spirit and Sojourner were 30-40% efficient, which was a large contributing factor to their longer-than-expected use. Beyond that I'm afraid I don't know much. And I certainly know you have a stronger chemical/physics background for understanding the actual workings than I do. So take it as you may.

There are solar systems using large parabolic mirrors to focus solar power to melt salt. You might be talking about Solar Tres. I looked up the efficiency of Solar Tres design. It is 18%. Mind you, this is all experimental as they don't know how this plant would operate over time (Solar One and Solar Two only operated for 3 years). The total reflective area will be 240,000 m² (60 acres of glass with an unknown area of buffer, storage and plant space) and it will produce 15MW (15/60 = 4MW(min) / acre for this design). My calculations would be then that in a very sunny place, like California, this plant would produce about 28,000 MWh per year (467 MWh / acre). A larger storage tank will be used giving the plant the ability to store 600 MWh, allowing the plant to run continuously during the summer (if the salt drops below a threshold temp they would burn fossil fuels to heat it). This solution might be good for a small town in the desert SW or even rural south of the USA with a population less than 2000 people, or up to 4000 homes if they had no industry. So minimally counting the cost of the heliostats, and building the operating plant it would cost about 120 million dollars. The startup cost per household would be about $30,000. Operating and maintenance? Who knows? My spot check on plant costs per MW is about $1.5 million, so it appears that Solar Tres will be about 5x the norm in plant costs, but thankfully, the fuel will be cheaper. The clincher for a Solar Tres, as in previous solar plants, will be in its maintenance and operational costs.

For comparison, some stats I found for Los Angeles proper shows they use 2500MW or 22 million MWh a year for 1.4 million consumers (2kW or 15 MWh / person / year which counts residential, business and industry). Extend that to the 5 county LA area with 20.6 million people. Let's see how many acres of land they would need for the power consumption of just the 5 county LA region, shall we? Oh... About 691570 acres, or 1,080 sq. mi. For comparison, the State of New Hampshire is 8,968 sq. mi., and Yellowstone National Park is 3,472 sq. mi. It would cost the 5 county LA area at least 65 to 80 billion dollars to build it (2x the normal rate).

Summary: Solar power still falls on the Earth at 1000 W/m2. If you have a huge 100 m2 reflector beaming it into the size of a postage stamp the postage stamp is getting 1Kw of energy when the sun is out. There are 8760 hours in one year, so a solar plant at 100% solar efficiency is going to get a fraction of that even in a very sunny place due to the available sunshine. LA gets 1861.5 hours of sunshine per year on average (less smog). Hence, 240000 m² of reflecting area results in 240MW(potential)/15MW(actual) = 6.5% of the suns potential energy is converted to power.

P.S. My investigation shows that Sojourners solar panels averaged 15% efficiency.
P.P.S I found the actual estimate for Solar Tres plant costs from MIT. $7500/KW, so actually 5x the norm.