By Dave Elliott
A recent paper in Applied Energy, from two researchers at Imperial College London, offers some helpful policy and economic insights on the impacts of various UK possible energy mixes for electricity supply, including a high renewables mix, but with biomass use not included, based on detailed spatial (20 regions) and temporal (hourly) modelling. Scenarios with nuclear and fossil/CCS were also explored.
The overall prognosis for renewables is very good. The headline conclusion was that ‘up to 60% of variable renewable capacity is possible with little cost increase’. Moreover, it was claimed that ‘using current technologies, renewable shares up to about 80% are possible without significant cost increases’, although the paper adds ‘to go beyond that, improved technologies (either for dispatchable supply or for storage) and/or significantly increased interconnection and imports from beyond the UK are necessary’. However, assuming that was attended to, it concluded ‘even with the conservative cost assumptions used, achieving renewables shares above 80% is feasible from a cost perspective and from a technical perspective to the degree that hourly data can demonstrate this’.
The paper is quite keen on storage to backup variable renewables: ‘The availability of grid-scale storage in scenarios with little dispatchable generation can reduce overall levelized electricity cost by up to 50%, depending on storage capacity cost’. But for high renewable scenarios, it also sees a need for supergrid links and firmer renewables. So overall a mix is needed: ‘for more than an 80% renewable generation share to be economically feasible, large-scale storage, significantly more power imports, or domestic dispatchable renewables like tidal range must be available’.
The mix in the various sub-scenarios for a non-nuclear 80% renewables contribution ranges up to around 25 GW of large scale PV, 61 GW of roof-top PV, and 84 GW of onshore wind. In some variants tidal range is at 7.6 GW and tidal stream at 15 GW. Oddly only around a maximum of 8 GW of offshore wind is called on, but CSP imports are put at around 20 GW in one sub-scenario. Gas turbines make up most of the rest, along with 5 GW of HVDV supergrid links, 2.74 GW of pumped storage and 1.1 GW of standard hydro in all variants.
Interestingly it was found that ‘for a large range of combinations between renewables, nuclear and fossils, the costs are essentially the same as they are for today’s system. Only for the scenarios with renewables above 70% of installed capacity do costs start rising above 0.10 GBP/kWh, and only for 90% and 100% renewables do the costs go significantly beyond that figure’. Note that this is using DECC’s cost estimates for all sources, which may be optimistic on nuclear and pessimistic on renewables, and it excludes the use of biomass.
As to future policy, the paper says ‘A “no clear direction” policy does not send a strong message to investors, and later changes in focus may leave them with stranded assets.’ Instead, it calls for ‘a policy built on clear framing of goals and conscious choice to support investment into a specified set of options, for a minimum duration of time.’ It adds ‘It is important to create a transparent framework so that whichever system is desired is actually built. Only clarity on goals can result in the participation and buy-in of government actors, market actors, and civil society actors, all of which are necessary for a successful energy system transformation.’ Applied Energy Vol.152, 15 Aug. 2015, pp83–93: www.sciencedirect.com/science/article/pii/S0306261915005656
Imperial College is not alone in looking at grid balancing in high renewable UK scenarios. For example, a study last year from the University of Southampton, comparing energy storage and interconnectors, also used hourly modelling and found that some storage systems (specifically, hydrogen gas stored in underground caverns) were cheaper than supergrid interconnections, although as yet much less developed: http://digital-library.theiet.org/content/journals/10.1049/iet-rpg.2014.0042
Clearly, with storage moving up the agenda, including Power-to-Grid systems, along with demand-side smart-grid management, but supergrid interconnections also looking viable (see my next post), there is still some way to go before we can be certain what might be the best approach to balancing in practice. But these and other studies are beginning to throw light on what the best options might be. Most likely, across the EU, it will be a mix of all or most of them, large and small, depending on geography, the local demand context and local supply optimals.
How does this sort of inspiring scenario stand up against where we are at present? It has to be said we are a long way off – and heading, in the UK, mostly in the opposite direction. The recent moves to block on-shore wind from access to support from the Renewables Obligation and also from the Contracts for Difference system, coupled with the existing block to large solar farms and plans to extend that to smaller schemes, does not bode well. Similarly for the move to remove the exemption for renewables from paying the climate change levy.
Allegedly all this is because renewables are now becoming cost-effective and do not need more subsidy support. That might be true of some of them, if the rival options, nuclear and shale gas/CCS, were not getting increased support. As Labour’s Lord Granchester pointed out in a Lords debate on the new Energy Bill, ‘although the majority of the Bill is devoted to providing certainty of benefits for investors in offshore oil and gas, the two clauses that deal with onshore wind as a future energy source do the exact opposite for investors in renewable energy. These changes to the financial support for onshore wind threaten the future of 19,000 jobs supported by that sector. These changes certainly curtail future development of the lowest-cost source of low-carbon power, and by setting dangerous precedents for other renewable sources of energy, investor confidence in a stable UK business environment is being shattered’. And he quoted the company E.ON as saying: ‘This jeopardises the reputation of the UK as a stable and attractive market to invest in’. http://www.publications.parliament.uk/pa/ld201516/ldhansrd/text/150722-0001.htm#15072240000325
Nuclear is also getting significant support. E.ON has long since given up supporting new nuclear in the UK, but now even former Conservative Secretary of State for Energy (1979-81) Lord Howell of Guildford has expressed doubts. In the Lords debate he described the proposed Hinkley station as ‘by far the biggest future burden on consumers and households’ and ‘one of the worst deals ever for British households and British industry’. Though he was still ‘very pro-nuclear’ and looked to new projects in the future, he said he ‘would shed no tears at all if the elephantine Hinkley C Project was abandoned’. There are reportedly signs the Treasury may agree. If that’s the eventual outcome, then, with £24bn freed up and more if the shale gas drive is abandoned, perhaps the UK could get stuck into an expanded renewables programme, rather than throttling back support prematurely – just as some of the key technologies were nearing competitiveness. The technical options are there to avoid fracking: http://bit.ly/1G79f2J and, longer term, as the Imperial College scenario showed, to squeeze out most of the rest of the non-renewable sources.