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100% renewables – a fantasy?

By Dave Elliott

‘Electricity comprises just one fifth of annual energy demand in the UK, so creating a 100% renewable energy economy would be an order of magnitude more difficult than the already challenging task of powering our existing electricity grid with 100% renewable sources’. So says a report from the Policy Exchange, putting the case for Small Modular Reactors. It’s a familiar line – 100% for power will be very tough, 100% for all energy impossible.

The Policy Exchange claims that The diffuse and intermittent nature of solar and wind means that we cannot rely on them for 100% of our energy needs – for example, January typically sees at least one week where virtually no electricity is produced by either wind or solar compared with what is needed. Buying in electricity through interconnectors from other Western European nations will be increasingly difficult as our neighbours also turn to wind and solar and so have less capacity to export, while the battery storage capability to back up renewables could cost up to £1 trillion. We need a reliable and affordable low carbon form of energy – small modular reactors have the potential to be that technology.’

Citing David McKay’s views, it says ‘there are two main challenges with moving to a 100% renewable energy system. The first is simply in producing enough electricity from sources of energy that are very diffuse. Powering a country by wind, water and biomass, for example, would require hundreds of times more land (or sea) than doing so with fossil fuels or especially nuclear power. The second challenge is in coping with the intermittent nature of wind and solar power’. And it develops these views in some detail.

However, this is all going over old ground. There have been many global and national studies suggesting that it is possible to reach near 100% of electricity by 2050 and some saying 100% of all energy is possible by then, without significant land-use conflicts. The most notable of the latter is the 139 country study by a team from Stanford University led by Prof Mark Jacobson. But there are many more. The most recent is the global and regional study from LUT in Finland/EWG in Germany.

The Policy Exchange report seeks to discredit studies like this by citing studies by Heard et al, and an Energy Innovation Reform Project (EIRP) report, which looked at some of them (initially 24, and 30 respectively). The Heard review rejects many such studies on the basis of their failure to meet the criteria it sets for credibility, including grid balancing, although it accepts that some studies do address that. Its main concern (apart from the absence of nuclear in the scenarios) seems to be that there is too much optimism about the role of storage.

Certainly, while short-term flexible balancing is being achieved and batteries can help with that, long-term storage to deal with the occasional long-term lulls in renewables is only now taking off seriously. Though storage of surplus output from wind and PV, converted to storable hydrogen, and then maybe methane, looks like a winner. However, it will take time to deploy widely. But then so would the new nuclear options and, given varying demand, they too will at times have surpluses to deal with, so to some extent it’s really just a matter of which supply option you like. The supply variations would be different with renewables, with short-term variations being the most obvious, but smart grid demand management could help deal with these, and reduce demand peaks. The longer-term lulls are also mostly unique to renewables, although nuclear plants can also go offline suddenly. Given proper balancing and top-ups from supergrid imports/exports, it’s not clear (see below) if a system based on renewables would be any less robust or costly than one based on nuclear.

The EIRP report disagrees. It reviews 30 deep decarbonisation studies that were published since 2014. They say there was a consensus that near 100% decarbonisation is much more challenging than making it to 50-70%: ‘While it is theoretically possible to rely primarily (or even entirely) on variable renewable energy resources such as wind & solar, it would be significantly more challenging & costly than pathways that employ a diverse portfolio of resources. In particular, including dispatchable low-carbon resources in the portfolio such as nuclear energy or fossil energy with carbon capture & storage would significantly reduce the cost and technical challenges of deep decarbonisation.’

However, there are studies suggesting that, with flexible smart grid balancing/supergrid trade, which could avoid some losses by better matching supply and demand, a diverse renewables-based system could be just as reliable and also possibly less costly. Indeed one study claims that ‘flexibility can significantly reduce the integration cost of intermittent renewables, to the point where their whole-system cost makes them a more attractive expansion option than CCS and/or nuclear.’ At the very least, with a large renewable capacity, sufficient to meet most demand most of the time, there would be some surpluses that, if stored, could meet demand when renewables were low and/or demand was high, with the export of some of these surpluses providing an income that could offset the cost of the system. Basically we are looking to a new more efficient system, with lowered costs. Not much need for big inflexible nuclear then, or CCS, with, given proper attention to energy efficiency, renewables able to supply all power by around 2040:  With enough to spare, in time, to also meet most heat and transport fuels needs, directly or via surpluses, in a balanced system. See my next post.

However, the Policy Exchange report sees it very differently – Small Modular Reactors can step in: SMRs could offer a number of advantages in a flexible power system, including the potential for dual output, producing other useful services in addition to electricity, like hydrogen or heat. SMRs could, for example, provide a demand/grid management solution by redirecting the power from an SMR to hydrogen production when renewable output is high’.

It is not at all clear if SMRs will be any more flexible than conventional nuclear plants. It is claimed that some types might be – molten salt reactor systems, for example. But they are decades away. Most current designs are just smaller versions of standard reactors e.g. NuScale’s mini PWR. Being smaller might make them easier to fit into gaps and niches, including for local heat supply. However, the SMR ‘Combined Heat and Power’ heat supply concept assumes SMRs can be in or near cities, which may not be acceptable, given safety and security issues. Indeed, the Policy Exchange report notes that 62% of those asked in a recent YouGov UK survey said they would be unhappy living within 5 miles of one. The economics are also far from certain. Being able to sell heat as well as power would seem vital, but even that may not make SMRs economically viable, although mass production might improve the situation, if enough sites could be found.

But as it stands, SMRs look likely to be expensive. Moreover, given the government’s low level of support, that may not change soon. Only £4m has been allocated initially for R&D on new reactor types, although maybe £40m later on, plus £7m for assessment. In which case the timetable in this ETI report, with SMR start up in 2030, may be very unrealistic.

All this would also seem to make the Policy Exchange report’s recommendation that ‘when the UK leaves the EU it should abandon renewable energy targets’ very unwise. We are going to need as much as we can get, and targets help. And with the UK likely to get to 50% of power by 2035,  near 100% by 2050 wouldn’t be a bad one, with 100% for most energy as the next hurdle. See my next post.

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