LUT University in Finland has found that a 100% renewable energy/storage mix would save the UK over €120 bn by 2050 compared with the UK Government’s current net zero plan. That’s one conclusion from a series of scenarios in a new LUT report. Its ‘Best Policy Scenario’ (BPS), aims for 100% renewable energy in 2050, with offshore wind as the main resource, limiting onshore wind and solar according to available land area, but its backed up by a second scenario called ‘Inter-Annual Storage’ (IAS) which adds on to the BPS the required inter-annual storage needed to provide good levels of insurance against the possibilities of low-wind years. A third scenario (BPSplus) tests the limits of higher land area availability for onshore wind and solar photovoltaics, and where also renewable electricity-based e-fuel imports are allowed. And finally, a fourth scenario, called ‘Current Policy Scenario’ (CPS), looks at the UK Government’s strategy for net zero as published in 2020.
The generation shares in the offshore wind dominated scenario are 44% offshore wind, 16% onshore wind, 25% solar PV (including prosumers), 11% wave energy, and 4% others. That’s based on solar PV being limited to 1% of total land area, with an upper limit for solar PV therefore being 183 GW, while on shore wind is assumed to be limited to 2% of total land area, leading to a 42 GW capacity limit. However, in the scenario with less land limitations, the generation shares are 39% solar PV (including prosumers), 31% offshore wind, 27% onshore wind, and 3% others.
The preferred scenario is the one dominated by offshore wind, supplying 509TWh, but, as well as battery storage for short-term balancing, the IAS variant includes large amounts of inter-annual energy storage to cope with fluctuations in wind power outputs within and between years. The study finds that storing renewable energy as renewable electricity-derived methane in conventional natural gas storage facilities is the most cost-effective means of inter-annual storage. The methane is made from direct air captured CO2 and green hydrogen, the latter being produced using renewable electricity: methane is preferred as the storage medium due to its higher volumetric energy density.
There is a trade-off between land-use and cost: the more onshore wind power and solar photovoltaics are used, the cheaper the path to net zero becomes. A scenario with low land area impact and priority on offshore wind power has a €68bn total annual cost and an LCOE of 43 €/MWh in the target year 2050, while a scenario with ‘stronger area impact caused by onshore wind power and solar PV use is able to reduce the total costs by 15% to €58 bn and the LCOE to 41 €/MWh’. For comparison, CPS, the government’s current policy scenario, with nuclear and CCS also featured, along with offshore wind, has a higher annualised cost, €86 billion in 2050, and a highest LCOE, at 74 €/MWh, in 2050. Note that the same assumptions for demands for energy services are used in all scenarios, and that it is therefore concluded that ‘the 100% renewable energy scenarios are superior in achieving these services for lower cost and lower systemic risk compared to Government plans’.
Carbon savings are achieved in all sectors by electrification. Heat generation shifts from natural gas boilers to heat pumps with high efficiencies for low-temperature heat, while e-fuels and direct electric heating become important for medium- and high temperature industrial heat. Electricity demand for the transport sector grows significantly to 486TWh in 2050. But of course you may want to try to reduce this by social policy and behavioural changes. Indeed energy saving in all sectors could cut all the scenario costs, so, as Jonathon Porritt says in his Forward to the LUT report, we need to put ‘as much emphasis on energy efficiency as on renewables and storage.’
LUT do focus on what can be done technically, mostly on the supply side, although clearly they would also be happy to see social policy and demand side changes. For example, they say ‘for the purposes of analysis (although not policy preference) substantial growth in demand for road and air transportation use is assumed in all scenarios’. But this is not a policy paper. Instead it’s a quite hard-headed technology assessment, with the main speculation being about whether hydrogen or methane will be the best long-duration storage option. LUT come down on the side of methane, as being cheaper. That may not pan out in reality and there is also the problem that the combustion of methane will lead to more CO2 generation (LUT do, arguably, seem overly fond of DACU), whereas the combustion of green hydrogen doesn’t, or need energy to run. It is also a little odd that LUT back wave power as a possible bit player, but not tidal power.
However, details like this apart, overall this is still a very worthwhile assessment exercise - all credit to Dr David Toke and the ‘100% Renewables’ lobby group for supporting it. It does clearly show that a zero carbon 100% renewables scenario is possible, at lower cost than any other scenario. As Toke notes the implications are that ‘all public and enforced consumer spending on new nuclear power and carbon capture and storage should be scrapped and instead funding should be put into renewable energy, energy efficiency and storage capacity.’
Nevertheless, it does also open up some challenges, not least the need for ‘a compromise between land area impact and total system costs.’ Further, LUT says, ‘the necessity of inter-annual balancing requirements that originate from high shares of wind power implies a trade-off between energy independence on the one hand and total system costs on the other hand.’ For example, the cost of producing and storing methane within the UK adds 31% to the system cost, but, it says, some of that could be avoided by ‘importing sustainable methane from other countries’. Of course that may not be what the UK wants to do - after the recent run in with Russia! Ultimately, LUT concludes ‘those decisions have to be made carefully in a socio-political discourse.’ But let’s not leave it too long…there is no time to waste. And, the UK is well placed to make big gains in this area.