Bill Totten's Weblog

Tuesday, November 29, 2005

How Much Energy Do We Have?

Are there enough renewables to keep the lights on?
The answer will be comforting to no one.

by George Monbiot

Published in the Guardian (November 29 2005)

In one respect, Simon Jenkins is right. "Nobody", he complained in the Guardian last week, while laying out his case for nuclear power, "agrees about figures" {1}. As a result, "energy policy is like Victorian medicine, at the mercy of quack remedies and snake-oil salesmen".

There is a reason for this. As far as I can discover, reliable figures for the total volume of electricity that renewable power could supply do not yet exist. As a result, anyone can claim anything, and anyone does. The enthusiasts for renewables insist that the entire economy - lights, heating, cars and planes - can be powered from hydrogen produced by wind. The nuclear evangelists maintain, in Jenkins's words, that "even if every beauty spot in Britain were coated in windmills their contribution to the Kyoto target would be minuscule". All of us are groping around in the dark.

So though this is not a scientific journal, and though I am not qualified to do it, I am going to attempt a rough first draft, which I hope will be challenged and refined by people with better credentials. Some of my assumptions are generous, others are conservative. This will be far from definitive and, I am afraid, quite complex, but at least, on the day the government's energy review is announced, we will have something to argue about.

The UK currently has an installed electricity generating capacity of 77 billion watts {2}. Demand for electricity peaks on winter evenings between 5 and 7 pm, when we use some 61.7 billion watts {3}. A recent report by Oxford University's Environmental Change Institute estimates that if we do everything possible to improve energy efficiency in the home and install mini-wind turbines and small "combined heat and power" boilers, we could reduce our demand from big power plants by 25 billion watts, or forty percent, by 2050 {4}.

I haven't been able to find a comparable study for offices and industry, so my first leap of faith is to assume that the same cut can be applied across the economy. This is likely to be generous. It is now clear that 2050 is too late: drastic cuts - eighty to ninety percent - in greenhouse gases need to be made by 2030. So my second assumption is that the forty percent cut can be evenly spread across time: that we can, in other words, reduce peak electricity demand by 22% by 2030. This means that it falls by 13.6 billion watts, to 48.1.

Because wind doesn't blow consistently, wind power cannot replace fossil fuels watt for watt. A paper published in the journal Energy Policy estimates that 26 billion watts of installed wind capacity (which could meet about twenty percent of current electricity demand) would replace 5 billion watts of fossil fuel plant {5}. Graham Sinden at Oxford University has shown that a more reliable mixture - 43% wind, 52% wave and 5% tidal stream power - could, at the same volume, replace 8 billion watts of coal or gas {6}.

The National Grid company tells me that wind power could directly deliver "at least twenty percent" of our electricity and remain "economically feasible" {7}. Assuming that the same can be said of Graham Sinden's mixture, 20 billion watts of installed renewable capacity will mop up twenty percent of our reduced demand (48.1 billion watts), displacing 6.2 billion watts of conventional power plant. This leaves us with 41.9 to find.

Figures from the Energy Technology Support Unit at Harwell suggest that if you build only in places with an average windspeed of at least seven metres per second, and keep out of national parks, areas of outstanding natural beauty, nature reserves and towns and villages, you could produce a maximum of 58,000 billion watt-hours per year of electricity from onshore wind (a watt-hour is an hour of electricity delivered at a rate of one watt). If you build only in shallow water with a firm seabed, out of the path of migrating birds and military exercises, and where grid connections are available, you could generate 100,000 billion watt-hours of electricity from offshore wind {8}. These estimates are probably conservative, as wind turbines are already bigger than the researchers envisaged.

The same study estimated that 53,000 billion watt-hours can be produced from wave power and 36,000 from tidal stream machines. A House of Lords committee reports that it might be possible to generate 24,000 billion watt-hours from tidal lagoons {9}. I won't count electricity from sunlight, because it's expensive and isn't produced when we need it most. This means that if we used all the available sources of variable renewable power in the UK, we could produce 271,000 billion watt-hours of electricity per year.

We have already used up 20 billion watts of installed renewable capacity. Assuming that renewable power is thirty percent efficient, we can multiply 20 by 8760 (the number of hours in the year) and 0.3, to make 52,600 billion watt-hours. Subtract this from 271,000 and we are left with 218,400.

Now here comes the biggest leap of faith. I am going to assume that by 2030 a cost-effective energy storage technology has been developed which has a fifty percent efficiency. The most likely technologies are hydrogen (which can be burnt in gas turbine engines) or a battery system like the one envisaged in the UK's Regenesys project, which was scrapped last year. Either one would add considerably to the costs of power generation, so investors are likely to become interested only if gas prices keep rising (which is likely) and nuclear operators are forced to carry their own insurance costs (which is unlikely). But if either the market or the government swung behind energy storage, then something like half the output from our variable power sources could be turned into a reliable supply of electricity. That means 109,000 billion watt-hours.

To this we could add 17,000 billion watt-hours from willow plantations grown on the farmland currently under set-aside {10}, 6,000 billion watt-hours from farm and forestry waste, 6,000 from hydro power and 5,000 from landfill gas {11}, to give a total for reliable electricity generation from renewables of 143,000 billion watt-hours. Assuming very conservatively that this is evenly distributed across the year (in reality much of it can be held over to meet peak demand), and that at any one time 85% of it is available, this gives us 19 billion watts of installed capacity. We needed 41.9, so our shortfall is some 23 billion watts at peak demand, and 34.8 billion watts of total capacity. (The need for spare capacity could be greatly reduced if we managed demand rather than supply, as the great free-thinker on energy systems, Walt Patterson, has suggested) {12}.

This is more than the apostles of renewable energy were hoping to see, but much less than the nuclear proselytes have predicted. It suggests that we could cut our demand for fossil fuel without building new nuclear power stations. But it is still too much: even 23 billion watts will help to cook the planet. So the choice then comes down to this: we make up the shortfall either with nuclear power, as Simon Jenkins suggests, or with gas or coal accompanied by carbon burial (pumping the carbon dioxide into salt aquifers or old gas fields). The first option means uranium mining, nuclear waste and the threat of proliferation and terrorism. The second means insecurity (gas) or open-cast mining and air pollution (coal) and a risk (though probably quite small) of carbon seepage.

Neither option, in other words, looks pretty. I fear I have succeeded not only in writing the densest column the Guardian has ever published, but also in demonstrating that this problem is harder to solve than I had hoped. Is there someone out there who can prove me wrong?

George Monbiot will be speaking at the Climate March on Saturday. For details see


1. Simon Jenkins, 23rd November 2005. At last Blair seems to see that our future is nuclear. The Guardian.

2. Eg

3. Brenda Boardman et al. 40% House. The Environmental Change Institute, University of Oxford.

4. ibid.

5. Lewis Dale et al, 2004. Total cost estimates for large-scale wind scenarios in UK. Energy Policy no 32, pp 1949-1956.

6. Graham Sinden, 2005. Wind power and diversified renewable energy portfolios. Presentation to the Carbon Trust.

7. Email from Chris Mostyn, Media Relations Manager, the National Grid.

8. Energy Technology Support Unit, 1999. New and renewable energy: prospects in the UK for the 21st century - supporting analysis. ETSU, Harwell.

9. House of Lords Science and Technology Committee, 15th July 2004. Renewable Energy: Practicalities. Volume I: Report. (it gives an installed capacity of 4.5 billion watts, and a capacity factor of 61% ).

10. Jim Watson et al., April 2002. Renewable Energy and Combined Heat and Power Resources in the UK. Tyndall Centre for Climate Change Research Working Paper 22.

11. Energy Technology Support Unit, ibid.

12. Walt Patterson, 2003. Keeping The Lights On: Working Papers 1-3. The Royal Institute of International Affairs.

Bill Totten


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