I was reading some posts people had written on energy, as well as commenting on another blog, when it struck me that those who promote green energy have a strangely myopic vision of energy use and production. They take their personal experience with solar cells or windmills and think it gives them some universal insight. Which is kind of like drawing conclusions about the Chili's chain from having run a lemonade stand as a child, or telling Hyatt how to operate because you had friends over last weekend.

How often have I heard someone say "My solar cells allow me to run my house and even have a bit extra, so I could power an electric car"?

First of all, I am very dubious of any such claims. The average solar energy world wide in a 24 hour period is 164 Watts per square meter. The best solar cell I could find has 28% efficiency. So, if you have an optimal cell and keep it spotless, have no trees to obstruct the light, and so on, you would need at least 22 square meters to get 24 kWh per day. And that is pretty much from a house setting in the middle of a barren plain, so that ti could get maximal solar exposure.

As the average family uses about 30 kWh per day, that would mean to replace just household energy consumption would require about 27 - 28 square meters, or a square about 16 feet on a side. Now, that sounds quite possible, but that assumes absolute peak efficiency, as well as no energy loss in storage batteries and so on. And it only covers AVERAGE home consumption. During spring and fall it would be far too much energy, in winter and summer when we use heating and cooling, it would be far too little.

If we assume peak usage is probably 2 to 3 times as much, and that efficiency is probably in the 15-20% range, we end up with a much larger solar panel requirement. To allow for peak consumption, dirty collectors, loss of energy in storage, subpar performance due to trees, other houses, whatever else gets between the sun and the collectors, we would probably need a much larger grid. Let us assume peak usage may rise as high as 3 kWh per hour, and that our collectors run about 15% efficiency. That means a square meter produces about 25 watts per square meter. So we need 40 square meters per kilowatt, or 120 square meters to meet peak demand. Since peak demand usually coincides (in summer) with peak energy production, I doubt we can rely on storage, and so we need to be able to produce it on demand. Meaning we would need a square almost 11 meters on a side, or a  set of solar collectors 33 feet by 33 feet. That is quite larger than most I have seen, which is why I doubt the rosy picture painted by many that they can completely power their house with solar panels.

Now, I could be wrong. If they have no air conditioning, use firewood for heating, and live in a relatively cloudless environment, as well as using less energy than a normal family, it is possible. I do not dispute that. But I think to extrapolate form that to claim that every family could do the same is just absurd.

And it gets more absurd the more you think about it. Let us allow that Joe Green can power his house in Arizona with solar cells. It means he gives up air conditioning and electric heat, and can't run the washing machine and oven at the same time, but he does do it. However, what about Emily Brown who lives in an apartment in New York? Even a six unit apartment would not have enough roof space to provide for all the tenants, not to mention the fact that neighboring buildings obstruct the sun except for a few hours around noon. And when we move to huge tenements, with a dozen floors and hundreds of units, separated from the neighboring building by only an alley, how should we put enough collectors on the roof to power them?

And residential power is actually the EASY part. If we take this "carry your own weight" philosophy to non-residential uses, it gets more absurd. Let us imagine a factory trying to power itself with only solar panels? Even if the residential ratio of roof area to power consumed (barely) allows solar to supply all the electricity, there is simply no way most factories could function solely on on-site solar collectors.

And since the comments I have seen mention electric cars, let us take that and ask, could the average UPS depot provide enough electricity to power its entire fleet of delivery trucks? Or your average train station provide enough solar electricity to power the entire fleet of trains? Could a cruise ship power itself with solar cells? Or a battle ship?

Yet, those advocating solar power make these silly extrapolations from their own experience. They even claim that they make enough power they could "sell it back to the grid". I am sorry, but even if they adopt a spartan lifestyle, there is simply no way roof top solar collectors could generate enough power to both supply themselves during non-generating times, level out their supply during unexpected drops, such as storms, and still provide any meaningful power to the "grid". This is simply a pipe dream.

And even if they could, it is a drop in the bucket compared to the true energy consumption of the US. In 2005 we consumed 29,000 TWh. That is a truly massive amount of energy. As I showed in an earlier essay, there is just no way some rooftop collectors are going to generate it. In fact, there is no way anything short of giving up entires states to nothing but electrical generation is going to replace it.

Solar is a nice idea for heating water and maybe charging cell phones. It is nice for powering gates at rest stops and maybe recharging lights in remote locations, but it really will never become our primary source of energy anytime soon. Perhaps in some distant future, when we develop a viable method for massive power transfer without wires, we can use huge space-based collectors which somehow beam home energy, but until then, I think we will need to either step up our production of petrochemicals, find another source of chemical energy, or, recognize the power inherent in the atomic nucleus, and go nuclear. Anything else is just fantasy.

POSTSCRIPT

By the way, theoilpatchplug on his blog does a similar review of windmills, though I think he may have been a bit overly generous to the windmill in his evaluation. Windmills, at least those about which I have information, are far from reliable, require regular maintenance, and are simply not feasible many places. As breakdowns are frequent if not properly maintained, any numbers need to include a large allowance for outages, making the numbers he used probably far too optimistic. Yet even then they don't seem to appealing, so I guess it doesn't make that much difference.

Well, you can read his post yourself and decide.