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Posted by Bill S on June 25, 2007 at 6:31:10 pm EDT
In reply to E-85 posted by Blackbeard on June 13, 2007 at 6:21:32 am EDT

MTB416 said "The sun gives off so much energy per day I find it ridiculous we don't pour billions upon billions into solar energy development."

Problem is that solar energy is limited by the energy density. That is, the energy per square meter. (so you will know, all the hot water for my house is solar-heated). Solar (and wind, geothermal, hydro including low-head hydro, co-generation, etc) can and should make a larger percentage contribution than they do. But there is a limit. Where I live, we do get a significant contribution from all those I mentioned.

Another problem is that at present solar electric still is not cost-effective in terms of dollars (that's because the environmental costs are ignored in setting rates). I am in the process of building a new house and looked hard at including photovoltaics as part of my roof. The average house in this area can see a payback with the current tax breaks, subsidies, and feeding the excess back into the grid (effectively using the grid as your battery) in 7-8 years. But the net cost of installation for a house of the size we are putting up, after subsidies and tax break is about $30,000, vs our annual electricity bill of $250-300, or a bit under 3000 kw-hr at about 7-8 cents/kw-hr. That's a full century for payback, which is longer than the expected lifetime by quite a few decades. Even with the quality we are building into the house, the house probably won't last that long. According to the DoE, the average US household uses 10,656 kilowatt-hours (kWh) per year.

Yes, we were using more electricity when we lived in Mississippi and used A/C and an electric stove (6000-8000 kw-hr annually), but this would still be a 50 yr payback, again longer than the lifetime of the photovoltaic system by a lot.

Don't misinterpret me. I am strongly in favor of developing alternatives to coal- and petroleum-based fuels for transportation, electric generation, etc. I spent some time professionally researching alternative energy sources and energy conservation, and as you can tell from our energy usage being way below the average per household for a house of the present size, practice what I preach. Photovoltaic systems will continue to drop in price. But they are a long way still, and there will still be that limit.

The Earth intercepts 21.3 kW/person at the present population of the Earth. This sounds like a lot - 187 thousand KW-hr per person per year. But that has to support all life on Earth, including all the food we raise or capture, all the transportation of that food, and all the electronic widgets we use (including the computer you are reading this on right now). Conversion rates into the movement of that car you drive to work are currently so low that solar-powered cars are only capable of carrying a single person (the solar challenge for cars takes place each year about 3 miles from my house, plus another event in Australia). Absorbing all that energy into the electric grid would require shutting down all weather (no more wind power, no more hydroelectric) and no more fields of corn to feed the cattle and hogs (a poor, extremely inefficient way of converting sunlight energy into food, anyway).

This again is not to say forget about solar energy. It is, rather, only a part of the solution. The most important part is reducing the impact per person. As long as you have politicians like Al Gore (excuse me, "environmental advocates") "setting the example" by using nearly 221,000 kWh (his 2006 usage) of electricity (plus an average $1,080 per month in gas bills in 2006), it is going to be hard to convince the average person to cut his usage. Our "green Gubernator" Arnie here in California still has a fleet of Hummers - yet another example for the average person to "look up to".

I am not that great an example myself. My household use may be below average, but last year I did rack up something like 40,000 miles of air travel (though commercial jets use less fuel per passenger mile than a Prius), and 20,000 miles in my cars (getting to climbing and skiing areas mostly, plus something like 4000 getting to and from the OR Shows). At least we get to the supermarket mostly by foot or bicycle.

An exercise for the reader - how many kW-hrs do you use in driving a 200 horsepower car to your local hills for a hike? For simplicity, assume you average half the power of the engine for the trip. I think you will be surprised. Then figure out how many hours you can run your house for the energy consumed on that trip.

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