If new nuclear doesn’t get built, it will be fossil fuels, not renewables, that fill the gap

The UK’s programme to build a new generation of nuclear power stations is in deep trouble. Last month, Hitachi announced that it is pulling out of a project to build two new nuclear power stations in the UK; Toshiba had already announced last year that it was pulling out of the Moorside project.

The reaction to this news has been largely one of indifference. In one sense this is understandable – my own view is that it represents the inevitable unravelling of an approach to nuclear new build that was monumentally misconceived in the first place, maximising costs to the energy consumer while minimising benefits to UK industry. But many commentators have taken the news to indicate that nuclear power is no longer needed at all, and that we can achieve our goal of decarbonising our energy economy entirely on the basis of renewables like wind and solar. I think this argument is wrong. We should accelerate the deployment of wind and solar, but this is not enough for the scale of the task we face. The brutal fact is that if we don’t deploy new nuclear, it won’t be renewables that fill the gap, but more fossil fuels.

Let’s recall how much energy the UK actually uses, and where it comes from. In 2017, we used just over 2200 TWh. The majority of the energy we use – 1325 TWh – is in the form of directly burnt oil and gas. 730 TWh of energy inputs went in to produce the 350 TWh of electricity we used. Of that 350 TWh, 70 TWh came from nuclear, 61.5 TWh came from wind and solar, and another 6 TWh from hydroelectricity. Right now, our biggest source of low carbon electricity is nuclear energy.

But most of that nuclear power currently comes from the ageing fleet of Advanced Gas Cooled reactors. By 2030, all of our AGRs will be retired, leaving only Sizewell B’s 1.2 GW of capacity. In 2017, the AGRs generated a bit more than 60 TWh – by coincidence, almost exactly the same amount of electricity as the total from wind and solar.

The growth in wind and solar power in the UK in recent years has been tremendous – but there are two things we need to stress. Firstly, taking out the existing nuclear AGR fleet – as has to happen over the next decade – would entirely undo this progress, without nuclear new build. Secondly, in the context of the overall scale of the challenge of decarbonisation, the contribution of both nuclear and renewables to our total energy consumption remains small – currently less than 16%.

One very common response to this issue is to point out that the cost of renewables has now fallen so far that at the margin, it’s cheaper to bring new renewable capacity online than to build new nuclear. But this argument from marginal cost is only valid if you are only interested in marginal changes. If we’re happy with continuing to get around 80% of our energy from fossil fuels, then the marginal cost argument makes sense. But if we’re serious about making real progress towards decarbonisation – and I think the urgency of the climate change issue and the scale of the downside risks means we should be – then what’s important isn’t the marginal cost of low-carbon energy, but the whole system cost of replacing, not a few percent, but close to 100% of our current fossil fuel use.

So how much more wind and solar energy capacity can we realistically expect to be able to build? The obvious point here is that the total amount is limited – the UK is a small, densely populated, and not very sunny island – even in the absence of economic constraints, there are limits to how much of it can be covered in solar cells. And although its position on the fringes of the Atlantic makes it a very favourable location for offshore wind, there are not unlimited areas of the relatively shallow water that current offshore wind technology needs.

Currently, the current portfolio of offshore wind projects amounts to a capacity of 33.2 GW, with one further round of 7 GW planned. According to the most recent information I can find, “Industry says it could deliver 30GW installed by 2030”. If we assume the industry does a bit better than this, and delivers the entire current portfolio, that would produce about 120 TWh a year.

Solar energy produced 11.5 TWh in 2017. The very fast rate of growth that led us to that point has levelled off, due to changes in the subsidy regime. Nonetheless, there’s clearly room for further expansion, both of rooftop solar and grid scale installations. The most aggressive of the National Grid scenarios envisages a tripling of solar by 2030, to 32 TWh.

Thus by 2030, in the best case for renewables, wind and solar produce about 150 TWh of electricity, compared to our current total demand for electricity of 350 TWh. We can reasonably expect demand for electricity, all else equal, to slowly decrease as a result of efficiency measures. Estimating this by the long term rate of reduction of energy demand of 2% a year, we might hope to drive demand down to around 270 TWh by 2030. Where does that leave us? With all the new renewables, together with nuclear generation at its current level, we’d be generating 220 TWh out of 270 TWh. Adding on some biomass generation (currently about 35 TWh, much of which comes from burning environmentally dubious imported wood-chips), 6 TWh of hydroelectricity and some imported French nuclear power, and the job of decarbonising our electricity supply is nearly done. What would we do without the 70 TWh of nuclear power? We’d have to keep our gas-fired power stations running.

But, but, but… most of the energy we use isn’t in the form of electricity – it’s directly burnt gas and oil. So if we are serious about decarbonising the whole energy system, we need to be reducing that massive 1325 TWh of direct fossil fuel consumption. The most obvious way of doing that is by shifting from directly burning oil to using low-carbon electricity. This means that to get anywhere close to deep decarbonisation we are going to need to increase our consumption of electricity substantially – and then increase our capacity for low-carbon generation to match.

This is one driving force for the policy imperative to move away from internal combustion engines to electric vehicles. Despite the rapid growth of electric vehicles, we still use less than 0.2 TWh charging our electric cars. This compares with a total of 4.8 TWh of electricity used for transport, mostly for trains (at this point we should stop and note that we really should electrify all our mainline and suburban train-lines). But these energy totals are dwarfed by the 830 TWh of oil we burn in cars and trucks.

How rapidly can we expect to electrify vehicle transport? This is limited by economics, by the world capacity to produce batteries, by the relatively long lifetime of our vehicle stock, and by the difficulty of electrifying heavy goods vehicles. The most aggressive scenario looked at by the National Grid suggests electric vehicles consuming 20 TWh by 2030, a more than one-hundred-fold increase on today’s figures, representing 44% a year growth compounded. Roughly speaking, 1 TWh of electricity used in an electric vehicle displaces 3.25 TWh of oil – electric motors are much more efficient at energy conversion than internal combustion engines. So even at this aggressive growth rate, electric vehicles will only have displaced 8% of the oil burnt for transport. Full electrification of transport would require more than 250 TWh of new electricity generation, unless we are able to generate substantial new efficiencies.

Last, but not least, what of the 495 TWh of gas we burn directly, to heat our homes and hot water, and to drive industrial processes? A serious programme of home energy efficiency could make some inroads into this, we could make more use of ground source heat pumps, and we could displace some with hydrogen, generated from renewable electricity (which would help overcome the intermittency problem) or (in the future, perhaps) process heat from high temperature nuclear power stations. In any case, if we do decarbonise the domestic and industrial sectors currently dominated by natural gas, several hundred more TWh of electricity will be required.

So achieve the deep decarbonisation we need by 2050, electricity generation will need to be more than doubled. Where could that come from? A further doubling of solar energy from our already optimistic 2030 estimate might take that to 60 TWh. Beyond that, for renewables to make deep inroads we need new technologies. Marine technologies – wave and tide – have potential, but in terms of possible capacity deep offshore wind perhaps offers the biggest prize, with the Scottish Government estimating possible capacities up to 100 GW. But this is a new and untried technology, which will certainly be very much more expensive than current offshore wind. The problem of intermittency also substantially increases the effective cost of renewables at high penetrations, because of the need for large scale energy storage and redundancy. I find it difficult to see how the UK could achieve deep decarbonisation without a further expansion of nuclear power.

Coming back to the near future – keeping decarbonisation on track up to 2030 – we need to bring at least enough new nuclear on stream to replace the lost generation capacity of the AGR fleet, and preferably more, while at the same time accelerating the deployment of renewables. We need to be honest with ourselves about how little of our energy currently comes from low-carbon sources; even with the progress that’s been made deploying renewable electricity, most of our energy still arises from directly burning oil and gas. If we’re serious about decarbonisation, we need the rapid deployment of all low carbon energy sources.

And yet, our current policy for nuclear power is demonstrably failing. How should we do things differently, more quickly and at lower cost, to reboot the UK’s nuclear new build programme? That will be the subject of another post.

Notes on sources.
Current UK energy statistics are from the 2018 edition of the Digest of UK Energy Statistics.
Status of current and planned offshore wind capacity, from Crown Estates consultation.
National Grid future energy scenarios.
Oil displaced by electric vehicles – current estimates based on worldwide data, as reported by Bloomberg New Energy Finance.