Big boosts beat blackouts

Professor Jon Gibbins, University of Sheffield and Director, UKCCSRC gives his response to the National Grid’s ESO Technical Report into the 9 August power outage.

Professor Jon Gibbins, University of Sheffield and Director, UKCCSRC gives his response to the National Grid’s ESO Technical Report into the 9 August power outage.

National Grid’s report on the power cut in August[1] shows how important it is that operating power plants can give a big enough extra boost to the grid when things – for whatever cause – go wrong. When the UK’s grid slows down because unexpected generation shut-downs mean power demand exceeds supply something has to be able to provide enough ‘primary response’, a big boost of energy in a matter of seconds, to avoid electricity consumers getting cut off. In the past this boost used to be provided automatically by large coal power stations, which, if they were intentionally kept running at slightly less than full output, could quickly open their control valves and, for a short period, draw on the stored energy in their massive boilers to produce some extra steam and generate additional electricity. But these big steam plants are no longer there and the smaller boilers used to recover the exhaust heat from the large ‘jet engines’ in the gas turbine combined cycle power plants, which were providing the bulk of the firm and controllable fraction of power on the grid at the time of the power cuts in August, store much less energy and, on a fairly windy summer’s day, relatively few of these plants were running anyway.

Fortunately, though, even such a small fraction of gas and biomass power generation might soon be able to provide much more rapid primary response power on demand, so that the UK’s electricity grid can take mishaps like this in its stride and customers never notice. The key is to add units to these power plants to capture carbon dioxide (CO2) for secure storage, kilometres underground out in the North Sea (CCS, carbon capture and storage). This allows emissions from natural gas plants to be nearly as low as from renewables and nuclear, while biomass plants actually go net negative on emissions; capabilities that are essential anyway to achieve net-zero GHG emissions across the whole economy in 2050[2].

Capturing and compressing carbon dioxide requires energy, giving a reduction of somewhere between approximately an eighth (for gas) and a quarter (for biomass) in the plant’s electricity output. But part or all of this electricity can be restored just as quickly as the old coal plants used to be able to boost, and, unlike the coal plants, is available even when the CCS plants are running most economically, at full load. And not only is the power available for the primary response period of around 30 seconds: if needed it can continue to be supplied for however long it takes for additional secondary response generation capacity to come on line. For shorter and more limited boosts CO2 capture would not even need to be interrupted. In real emergencies capture might have to be stopped for up to a few hours. But, since total long-term CO2 emissions are what matters for climate change, the relatively small extra amounts of CO2 that would then be released can be made up by additional capture at other times, when electricity is abundant or even in surplus, to meet the required annual targets.

So, how soon can this combination of much lower CO2 emissions from our electricity system and much better grid security be achieved? Well, it could begin surprisingly soon. The recently-launched Industrial Decarbonisation Challenge[3] provides support activities and planning for the first UK CCS power plants, potentially both gas and biomass, to start delivering power by around 2025. Sufficient knowledge already exists to design them, including the boost concepts, which have largely been developed by UK CCS researchers. What is also needed, though, is the money to pay industry to actually build and operate them. The government is about to develop variations on the ‘Contracts for Difference ’ (CfD) electricity support scheme, already used for renewables and nuclear, to support CCS power[4]. CCS power plants can provide 24/7 power to complement intermittent renewables, net negative emissions with biomass and also give a big boost when it is really needed. But to get these valuable features built in to new CCS power plants and operated to save consumers money – and hours spent on immobilised trains or worse problems – it is crucial that regulators recognise and reward the transformational opportunities that these unique capabilities provide for the UK’s 21st century electricity and wider energy systems.





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