The Governments proposed reforms to the electricity market have been eagerly awaited. We are pleased that the Department of Energy and Climate Change (DECC) sought evidence earlier this year on the role of gas generation. This is a welcome sign that DECC recognises the importance of gas in ensuring we are all reliably supplied with electricity in the future.
Gas is currently the largest source of electricity (40 per cent in 2011), and it seems inevitable that new gas-fired stations will have to be built as the UK faces power station closures amounting to the loss of 40 to 50 gigawatt (GW) of capacity by the mid 2020s due to emissions restrictions and old age. The closures are on an unprecedented scale and matched possibly only in Japan, following the Fukushima disaster in March 2011. No other technology can fulfil our electricity needs on this scale within the required timeframe.
The coal-fired stations, built between the mid-1960s and mid-1970s, have been the mainstay of the electricity system for several decades but are now reaching the end of their working lives. Even with Government reforms, the amount of new nuclear generation which can be built in the next 10 years or so will almost certainly be less than the existing capacity which has to be retired (9.5GW).
Meanwhile, even with plans to install 25 to 30GW of wind turbines, there will still be a substantial shortfall in power generating capacity. The total capacity in the UK is currently about 80GW with maximum winter demand of around 60GW (demand is forecast to rise as the economy becomes more electrified).
New gas-fired power stations, mainly combined cycle gas turbine (CCGT) plants, will provide crucial back-up for intermittent renewable power, will close the shortfall in base load generating capacity and ensure grid stability.
Gas, however, is not just a transition fuel towards decarbonisation of the electricity market. It offers benefits in ensuring a realistic and flexible electricity mix for the future and is suitable for carbon capture and storage (CCS) once this technology becomes proven on a commercial scale.
The benefits are:
– low capital costs making it easier to finance
– proven technology that can be built quickly at the required scale, providing reliable generation with high load factors
– the flexibility to be located near demand, using former coal or oil-fired station sites with existing grid connections but with smaller footprints than the plants they replace
– large reductions in emissions relative to the coal and oil-fired stations
– suitable for carbon capture and storage
There will nonetheless be difficulties in building enough gas-fired generation. Creating a framework to encourage new CCGT build is essential, as is ensuring a more flexible national transmission system (NTS). The demands on gas infrastructure, mainly the NTS, are going to change as gas demand responds to variability in wind generation (see graph left).
The graph shows actual daily wind generation versus grid-connected capacity during the winter of 2015 to 2016, the windiest in some years. Daily generation swings between over 70 per cent to less than 10 per cent of installed capacity and reveals the extent to which back-up generating capacity will have to react to these rapid variations.
Also, gas demand for heat currently far exceeds that for electricity. If all the heat satisfied by gas on cold winters days were instead to be supplied by electricity, the electricity system would need to have four times its
The scale of the forthcoming changes in electricity generation is very large. While it is understandable that most of the attention to date has focused on reducing emissions, security of supply and affordability, with which comes economic competitiveness, are also high level objectives.