Nuclear is not the answer - but not why you'd think

This year, 2012, is the United Nations Year of Sustainable Energy for All. As their promotional material says, "Energy services have a profound effect on productivity, health, education, climate change, food and water security, and communication services" and clean energy directly affects our ability to achieve the UN's "Millennium Development Goals" which are the kinds of basic services we in Australia take for granted. As I have noted in the past, energy is the limiting factor for most other animals on the planet. The delicate balance between expending energy to hunt down a feed and expending too much energy to live is what drives evolution. Humans are generally above this daily energy trade-off as we have found ourselves an abundance of cheap energy in the form of fossil fuels. The trouble is, of course, that carbon dioxide released when we burn these million-year-old plants is changing the Earth's climate. Animals derive their energy from the Sun. The Sun shines on the grass; photosynthesis happens; and the grass grows. Grazing animals then eat the grass for energy. Higher order predators eat the grazers and so on. Humans derive our energy from the Sun too. A few hundred million years ago the Sun shone on plants; they grew; when they died they sank to the bottom of swamps where sediments covered them, squashing them and incubating them until we dug them up as coal or oil or gas and burned them. So fossil fuels are indirectly solar energy. Wind and wave power are indirectly powered by our Sun too as heat from the Sun changes the weather patterns which drive those. Photovoltaics, obviously, directly harness the Sun. Nuclear, geothermal and tidal are really the only power sources currently in use that are not powered by the Sun. You might think that points to an argument for a greater use of nuclear - harness the power of those little atoms falling spectacularly apart and free ourselves from the restriction of our nearest star. But an article in New Scientist this week argues specifically against that. As the article notes, the energy that comes into the planet from the Sun, should go out. We get 120,000TW of energy from the Sun every day. So 120,000 must be re-radiated to space, otherwise we get hotter. Because of one of those handy laws of thermodynamics (the first) it doesn't really matter in what form the energy is. It might have been a plant leaf once, and a bit of coal at another time, and maybe a warm toaster further down the track. But the little bit of energy that came from the Sun 300 million years ago, eventually gets re-radiated to space. We humans use 16 terawatts (TW) of energy from various sources at any one time. As we run our computers, dishwashers, TVs and airconditioners, we make heat that we don't need. This heat drifts about, dissipates and we forget all about it (That'd be that second thermodynamic law). But the planet doesn't. And that's the core of the argument against nuclear, tidal and geothermal. Say we make some toast using the power generated in a nuclear power plant. (Call it French Toast, given their enthusiasm for the power source.)This upsets the energy balance of our planet. Of the 120,000TW going out into space, a tiny amount - the heat from our French Toaster - didn't come from the Sun. 'Quel dommage,' I hear you say. 'So a little bit of toast warmed the planet - it's hardly going to make a difference.' And indeed, one slice of toast won't. But the New Scientist article quotes "back of the envelope" calculations by Eric Chaisson that points to humans using 5,000TW of energy by 2300, up from 16TW today. Admittedly, that's a long way away and any number of things could happen to change that. But if we end up using 312 times the amount of energy we do today, then our waste heat will matter; our energy sources will matter. The figures point to solar being the only energy worth considering. If we are to maintain a planet whose energy inputs are in equilibrium with our outputs, then energy from the Sun is the only possibility. Fossil fuels in theory maintain energy equilibrium, but the carbon dioxide released is adding to the greenhouse effect, preventing some of those 120,000TW being re-radiated. Nuclear, tidal and geothermal would add to the overall amount of energy that we need to lose to stay stable. The nuclear reaction taking place inside our nearest star is the only form of energy we can harness at a scale fit to service the billions of us eking out a living on this globe without changing the balance of our energy in-energy out equation. It's a balance, we've discovered, that is not robust enough to withstand the collective energy use of seven billion people, let alone the many more expected to join us in the coming years.