Thursday, January 27, 2005

Nuclear Family Upset By Battery Charges

Wired has a very frustrating article this month about nuclear power (not online yet - link forthcoming.) It's frustrating because it clearly expresses much of the problems with our current energy supply - and unlike other American publication often do, Schwartz and Reiss are emphasizing the coming dangers of Climate Change, not pushing it off to the side. Further, they note that carbon fuels' wastes are untaxed, whereas nuclear energy is taxed to support construction of long-term storage (the notorious Yucca mountain.) I've mentioned before how we should be thinking of CO2 the same way we think of U235.

The article loses me because it basically argues that we'll have to adopt nuclear as our primary energy source because none of the other non-carbon possibilities will do - dismissing wind and solar essentially out of hand. Now, I've said here before that I'm open to considering nuclear after we do everything else necessary to replace carbon energy. What I think woud be foolish to do is engage in a decades-long policy of building hundreds of nuclear reactors, when the price of solar and wind are both coming down precipitously. Schartz and Reiss talk about solar being 8 times more expensive than nuclear, but the price for next-generation, "clean, green and safe" nuclear energy they give is roughly $1.2/watt of installed capacity, which is roughly equal to the price quoted for solar power by Akzo-Nobel, which I mentioned previously here. They also resort to the straw man of a centralized solar utility somewhere in the desert - possibly the stupidest idea possible for solar power.

Now, one of the points the article stresses is that our global energy demands are going to increase in a huge way, and Schwartz and Reiss argue that nuclear is the only technology that can be deployed in sufficient volume to meet demand. Here I think they're just being ridiculous. As efficiencies increase and costs come down, I would be surprised if solar doesn't begin to out-compete even natural gas for peak power production. Further, unlike nuclear power, solar panels are a technology that can be mass-produced quite readily. What do you think is going to happen when the force that brought you $20 DVD players gets in to the energy game?

The Achilles Heel to solar power is the down-time problem. Our nighttime energy uses are quite a bit less than our daytime uses, but they're not zero. So long as we selfishly insist on heating our homes in the winter nights, we'll need backup. If we want to talk about long-term switching of our energy supply to solar, then we need to talk about the costs of a combined solar production/storage system, i.e. batteries or fuel cells. Fortunately, the solution is one I've mentioned before: electric cars. Because even the smallest, most efficient electric car is still going to require several day's worth of a typical household's electricity demand, this is a huge storage capacity that would otherwise mostly be wasted. Let's look at Volvo's latest concept car, the 3CC. With a full-charge range of 180 miles, most people would use only 20-25% of their car's stored energy in their daily commute. That leaves the other 75-80% to be used for other purposes.

Let's imagine an unlikely world in which every watt of energy we used was delivered by the sun. Your car - which you only use for at most a few hours a day, after all - spends most of it's time plugged in to the grid, either at home or at work. During the daytime, the grid feeds in solar electricity to your car, until the batteries are full. Once sunset comes, however, the car's batteries start putting out a stream of energy back on to the grid until the sunrises agan. The car would probably need a cutoff - preferably something the owner could customize - at which point the batteries would stop emptying, so that we don't have cars running out of batteries in the morning rush hour. How much energy could our cars store? The Stanford Electric Vehicle (SEV), which I mentioned before here, would store 40 kilowatt-hours onboard, roughly four days worth of energy for a current home. A four-person model, assuming energy storage scaled up with the size of the car, would store more than two weeks worth of power. If you owned the car and the solar panels it charged off of, and had free access to sell your solar energy the grid (an unlikely assumption, but let's run with this) your car could make you almost $7 every time you "emptied your tank" on to the grid, still assuming you kept 25% of the car's charge for your daily commute. $7 isn't much, but on the other hand it currently costs my brother somewhere in the vicinity of $30 to empty his tank out his tailpipe. (Okay, that sounds kind of dirty. Moving on...)

The real bonus to this scenario, however, is that our storage system for solar energy doesn't cost us anything extra - we're buying the cars anyway, we're just using them more intelligently. It's a variation on an idea originally proposed by the people at RMI as an additional selling point for fuel cell cars. However, I think we'll have to wait a bit longer for that. I've mentioned before, the solar-hydrogen-fuel cell system is currently far less efficient than a solar-battery system, though that could change. Even if it's more efficient, however, it's not certain to cost less. Even if both ends of the fuel-cell system are 85% efficient, it's still only slightly more efficient in real terms than the 70% most batteries get, and batteries are much simpler pieces of technology.

Oh, and please excuse the pun in the title.

Assuming Akzo-Nobel's price point of C$1.6/watt of installed generating power, how expensive a system would we need to charge a 4-person SEV with an oboard charge of 160 kwh each day? When does this system break even?

Assuming a mean of four hours of peak solar input each day, we need 40,000 watts of input. This comes to $64,000 for the solar power. Assuming the following:
  • The car is actually used, so we only sell 75% of the power back on to the grid.
  • Electricity sells for $0.06/kwh
  • The batteries are emptied every night, and fully charged every day.
  • Access to the grid is free (maybe to encourage solar power - who knows?)
That gives us 160*.75*0.06 = $7.2/day solar power.
$64,000/ $7.2/day = 8,888 days, or 24 years and a bit.

So... we still have some cost issues to work out. Or does someone see a huge math error?

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