Can solar PV really power the UK?

I am writing this in Tucson, Arizona, under an immense blue sky from which a powerful sun radiates strong energy almost all the year round. Surrounding the city is the Sonora Desert, a biodiversity wilderness full of beautiful cacti and other dryland species. Tucson has huge numbers of very large buildings with surely thousands of acres of combined roof space – and hardly a solar PV array to be seen.

It goes without saying that solar photovoltaics makes a lot of sense here. Solar delivers the most energy right when it’s needed – during the hottest part of the day and the hottest time of the year, when temperatures are consistently over 100F for weeks at a time and everyone has their air-con pumped up to maximum. There is a big role too for solar hot water. Instead, the region’s energy is two-thirds fossil fuels, with 40% supplied by coal power and 27% gas.

This is a place that desperately needs to go solar. The state needs a ramped-up feed-in-tariff to dramatically accelerate PV installations, which few homeowners or businesses can currently afford. PV arrays on rooftops also have the additional benefit of providing shading, further reducing the demand for cooling. However you look at it, solar in Arizona is a win-win-win.

Does the same really go for the UK? I strongly doubt it. Yet solar advocates make a lot of sweeping claims that don’t stand up to serious scrutiny – or even a little bit of basic common sense. Take for example, this statement, in a document on nuclear ‘subsidies’ produced by an anti-nuclear outfit called Energy Fair:

Photovoltaics (PV) could generate about 266 TWh/yr in the UK—about 66% of the UK’s present electricity demand. See “Renewable Energy and Combined Heat and Power Resources in the UK”, Tyndall Centre, 2002.(95) PV is quick and simple to install.

By the way, I regard Energy Fair as little more than a solar industry front group, whose main – though undisclosed – argument with the nuclear industry seems to be competition over who gets the ‘economic rent’ of state subsidies. (I dream of a future where renewables and nuclear advocates work together to get fossil fuels off the grid entirely, thereby avoiding dangerous climate change. But then I’m a hopeless utopian who believes human beings should generally be rational.)

Anyway, let’s look at this claim more closely. 266 TWh/yr is a lot of juice. So it’s time to follow up sources. First let’s go to the source referred to in Energy Fair statement. This is a paper by the Tyndall Centre from 2002, which says the following:

ETSU estimates the practicable resource to be 266 TWh in 2025 (calculated as electricity generated by the application of PV to all surfaces of available domestic and non-domestic buildings, allowing for 10% non-suitable surfaces and 25% shading, ETSU 2000 p.141).

So our realism alarm bells are already beginning to ring. Firstly, this estimate is calculated on the basis of PV applied to ‘all surfaces’ – walls, north-facing roofs and so on, allowing for only 25% shading, which is highly unrealistic as a cursory glance at any building in any location will tell you. Plus, I haven’t seen any wall-mounted PV for a long time. Is it even happening?

Second, this is ‘practicable resource’, which I assume means practicable in a technical-engineering sort of way. It does not mean economic. How much would it cost to install this amount of PV by 2025, given that the UK capacity factor is likely to be about 8% (meaning your hefty capital investment is sitting around idle for 92% of the time)? Note that the Germans, well-off as they may be, are now having to dramatically scale back their own feed-in-tariff due to the long-term cost liabilities now reaching hundreds of billions of euros.

Third, this assessment of the ‘practicable resource’ is not even original to the Tyndall Centre source. Instead, it is merely lifted out of ‘ETSU, 2000’, a bigger study by the now-defunct Energy Technology Support Unit. I can’t find this document anywhere on the web, which is perhaps not surprising as it is more than a decade old. (Let me know if anyone comes across it and I’ll post a link.) Couldn’t Energy Fair come up with anything newer? Or does nothing more recent have a similar and conveniently-large figure? Looks like a classic cherry-pick to me.

Perhaps a better way to more realistically assess the practical UK solar resource would be to use DECC’s energy calculator. Here you can select a very optimistic assumption of 9.5 square metres of solar PV panels per person, with “all suitable roof and facade space used”, by 2050. All this adds up to about 140 TWh/year in terms of generation, but that is still only 25% or so of what is needed given a realistic scenario of electricity demand increase. (Electricity demand will increase even if overall energy use falls due to efficiency; this is largely the result of electrification of transport and heating. The specific scenario selections on the graph are my own.)

[It has also been pointed out to me by David MacKay, after the first iteration of this post, that “the peak capacity for 140 TWh/yr would be
about 140 GW which is far more than midsummer demand – in fact it is
more than any demand ever. So you’d either need to shed solar (or wind or nuclear)
at midday on most sunny days, or you’d need to set up very large capacity energy
stores of some sort.” Worth bearing in mind also in trying to keep things realistic.]

Perhaps a more realistic assumption would be 4 square metres of PV panels per person by 2050, still a major achievement, but delivering only 60 TWh/yr of electricity and a relatively small contributor therefore to overall production. (And one needing a lot of backup, depending on the fuel mix of the rest of the grid.)

What is this telling us? That setting solar up against nuclear is a sure bet to a climate fail. I agree that solar has a role to play even in the cloudy UK, but it is not a big one. It’s great that the solar enthusiasts are working to achieve the end of covering all suitable rooftops, and let’s hope that costs continue to fall sufficiently so that this will one day become an economically-feasible endeavour. But please, solar folks – just focus on doing your own jobs. Stop trying to squeeze other low-carbon generation technologies – like nuclear, which can deliver far more, more reliably, and at lower cost – off the grid at the same time.

© Mark Lynas
« · »