Monday, August 1, 2016

Nuclear versus renewables

The other day I was doing some crude calculations on the feasibility of renewable energy in Britain. This came after I had detected some euphoria about the potential for solar power now that costs of solar panels have fallen and large-scale battery storage is becoming possible. I tentatively concluded that we could get all the energy we currently use if we were prepared to cover about 11% of the land area of the UK with solar farms. This was on the basis that, on average, a solar farm in the UK can deliver about 10 watts per square metre of land occupied by the farm. An on-shore wind farm, by contrast, can only deliver about 2 watts per square metre, though the land between the turbines can be used for other things. I then put together a very crude energy plan for the UK, using a combination of solar, off-shore wind, on-shore wind, tidal and wave power. It assumed that 30% of our current energy use would be from solar farms, occupying about 3% of our land, and that our energy demand would be reduced, through efficiency measures and demand management, by 37%. It looked just about feasible, technically if not politically.

Then I came across this video  in which the late and highly-respected Professor Sir David MacKay is interviewed by Mark Lynas eleven days before his untimely death in April. You can see what I thought was a pretty fair summary of the key points here. MacKay's book, Sustainable energy without the hot air, was my main source of information on the feasibility of renewable energy.

This reminded me of a devastating fact - that at midwinter in the UK, solar panels yield only about a ninth of the power they yield in midsummer, or about a quarter of their average yield. We would be getting the least energy from our largest single source at the time when our need for energy was greatest. To meet our winter energy needs with 30% solar, according to my very crude and questionable calculations, we would need to cover at least 12% of our land area - the same proportion as our urban and developed land - with solar farms. Tidal generators would be the only major source of reliable renewable energy in winter.

MacKay's conclusion was that nuclear power and fossil-fuelled power stations with carbon capture and storage were the only feasible main options for getting us through the winter. Also, if they gave us enough power to get us through the winter, they would be more than enough to get us through the rest of the year so that energy from renewable sources would be superfluous.

He stressed that this conclusion only applied to the UK. Most of the world's population lives at latitudes where sunlight is much stronger, where there is less difference in its intensity between summer and winter and where demand for energy, such as for air conditioning and refrigeration, is high when the sun is at its strongest. So over much of the world, solar power, combined with battery technology, really does look like a potential main source of energy - hence the euphoria over its falling cost.

However, the implications for the UK are depressing and disturbing. Our present nuclear strategy looks extremely dodgy, with heavy reliance on Chinese finance and on an unproven technology. The high strike price for electricity generated from the proposed new Hinkley Point reactor doesn't worry me unduly. At the moment, energy seems far too cheap when we take into account the risks from global warming. Fuel poverty should be addressed by relieving poverty generally and by making homes energy efficient. (The "rebound effect", whereby increased energy efficiency stimulates additional demand, would be negated by higher energy prices.)

Nor am I worried about the disposal of the resulting nuclear waste. Modern nuclear reactors are expected to generate about 10% of the waste from the earlier reactors so new nuclear power stations will add almost insignificantly to the waste problem we already have. My main worry is that we won't be able to build nuclear power stations, or develop and deploy carbon capture and storage, fast enough both to meet our energy needs and our commitments on emissions reductions. We risk either an energy gap or a major contribution to a future climate catastrophe.

Gas is generally seen as the answer to our woes as, at the point of burning, it generates about half the amount of CO2 per unit of energy compared with coal. However, it doesn't seem clear that gas is substantially cleaner than coal once we take into account the leaking of methane into the atmosphere between the extraction of gas from the ground and the point of burning.

Does this mean there is no place for renewables in the UK? In the interview, MacKay made clear one of his premises - that people and politicians in the UK want cheap energy. In my view, the need to decarbonise should take priority over the cheapness of energy. During the 2020s we will still be relying heavily on gas, both for domestic heating and for electricity generation. Gas-fired generators can be switched on and off. There is therefore a role for renewables in enabling gas-fired generators to be left switched off whenever there is adequate renewable energy available. This would probably be uneconomic in conventional terms as  it would be reducing the return on investment in the gas-fired generators. However, it probably looked uneconomic to resist Hitler in 1940. Some threats force us (or should force us) to look at economic considerations in a different light.

If carbon emissions were capped at a sufficiently low level to render catastrophic climate change extremely unlikely, and energy priced accordingly, then heavy investment in renewables might make sense to minimise our use of gas and help keep us warm until nuclear and / or other technologies are able to meet our energy needs.

I need to do more work on this.

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