Gas winter review: increasing variability puts pressure on compressor fleet

National Grid Gas (NGG) saw a different winter in 2020/21 than it had forecast, according to its Gas Winter Review and Consultation
The gas grid operator expected the trends of recent years to continue, forecasting that use of LNG would continue to increase. In fact, LNG imports fell to 8.9 bcm, compared with 13.4 bcm in 2019/20. This was because cold weather in Asia increased LNG prices in that region, so LNG cargoes were sold in that market.
Althogh UK prices did not rise far enough to attract as many LNG cargoes as in previous years, they were more favourable for suppliers than prices in Europe, so 4.8 bcm was imported to the UK via the gas interconnector, compared with a very small amount, just 0.3 bcm, in 2019/20.
The change from the previous year meant a big increase in the running hours for the fleet of ‘compressors’ that drive gas around its high pressure network, up from from 14,158 hours in 2019/20 to 25,533 hours in 2020/21. Overall, NGG had to increase use of compressors in central and eastern England, including at Peterborough, Kings Lynn, Diss and Cambridge. But it also had to vary compressor use from week to week, as supplies switched between the interconnector (on the East coast) and LNG terminals in South Wales and Kent.
Finally, NGG places an increasing load on compressors to ensure the system maintains its minimum pressure within the day, as users tap into the supply.
The amount by which pressures ‘swing’ within the day has been consistently increasing, as gas is used for short term balancing such as in peaking power plants, and this continues to rise.
NGG correctly anticipated that gas demand for electricity generation would increase in 2020/21, although the use of gas for electricity generation has been declining since winter 2016/17 and this overall trend is expected to continue. The operator expects the total demand for gas used for power generation will continue to fall, but the peak level of demand for electricity generation will remain the same, because gas power plants will respond at times of low renewables instead of providing continuous power. That will mean further need to use compressors to manage short term pressure swings.
NGG wants comments on the review and the upcoming winter by 24 July.
Read the Gas Winter Review and Consultation here