Groups such as the Renewable Energy Foundation (REF) (which has been described as 'an anti-wind lobbying organisation') (1) have regularly pointed out how large sums of money are spent on paying windfarms in Scotland to stop producing electricity. These payments are made in order to avoid the Scottish electricity grid from being overloaded. This is in a context where measures to increase the ability of the grid to absorb increasing generation of renewable energy (particularly including increasing the available capacity of large transmission lines) have been developed too slowly.
According to the Renewable Energy Foundation (REF) around £115 million was paid to Scottish windfarms in 2018 amounting to around £70 for each MWh of 'constrained' power (ie not generated). (2) This level of payment (£70 per MWh) is not excessive given that this amount is close to the average of what the windfarms earn for each MWh generated in a given year. Indeed, this is a bargain compared to what you would have to pay either of the Scottish nuclear power plant to turn down their power. Arguably they could not do at short notice at any price; certainly it would be very expensive for them. Both of the Scottish nuclear power stations are of a clunky design straight out of the early stone-age of nuclear power, replete with a dodgy (and cracking) configuration of graphite blocks which present a growing safety threat.
This problem of system overload is the reason that the recently completed transmission line linking Wales to Scotland was built. As Jonathan Marshall. Senior Analyst at the Energy and Climate Intelligence Unit put it recently: 'On top of reducing constraint payments, the link will reduce the cost of accommodating Scotland’s 2.6 GW inflexible nuclear power stations that work most efficiently when operating at full output'. (3)
In fact, in addition to increasing transmission line capacity, more decentralised solutions for absorbing increasing renewable generation should get more attention. These include development of local 'microgrid' strategies, more emphasis on storage solutions and a real effort to link large-scale heat pumps with district heating networks. The latter, heat pump solution, would also help to turn renewable electricity into heat. When there is too much electricity on the grid the heat pumps can produce hot water which is then stored in large hot water tanks to be used by local residents as is necessary. This is a technology that is being increasingly applied in Denmark.
Of course one immediate measure, with collateral safety advantages, can be taken to ease the current situation, and that is to ensure that Hunterston B is permanently closed. This power plant is currently shut down while the Office for Nuclear Regulation (ONR) conducts a safety review. A large number of cracks were found in the graphite blocks that surround the reactor core. The proper functioning of the blocks is essential for safety reasons, eg allowing fuel rods to be withdrawn and the control rods to be inserted in order to avert a calamitous accident (4). EDF is currently conducting a big public relations effort to convince everybody that the plant can be restarted without safety fears.
But in terms of balancing out the Scottish electricity grid, closing down Hunterston B would be very helpful.