Gas used for power generation in GB is expected to fall by over 10% this summer, down from 97.3TWh last year to 82.7TWh, according to National Grid Gas’s annual Summer Outlook. The change continues a downward trend that has seen gas demand for power fall from 121TWh since 2016 because of the growth in renewables and the commissioning of new electricity interconnectors.
Two further interconnectors are due to begin commissioning this summer: the North Sea Link with Norway and a third link to France dubbed ElecLink.
The figures, which represent gas taken directly from the high pressure gas network for power plants, masks a large increase in small scale gas engine arrays, who take gas from the distribution networks. But the fact that such small units are used only for short term peaks is supported by the fact that gas offtake by distribution networks and industry has remained steady over the period.
This summer NGG expects that exports of gas to Ireland will be slightly higher than last summer while those to Europe will fall, although that may change as European gas stocks are relatively low and may be refilled. It also expects that more of UK’s gas will come from Norway and the UK Continental Shelf because global liquified natural gas (LNG) prices suggest cargoes will go to higher-paying customers overseas.
The company was relaxed over operability of the network, although it said it needed more flexibility to move gas. “The rapidly changing dynamic of the NTS means that we are prepared to use compression at short notice, to both maintain locational pressures and respond to changes in the supply of LNG” due to changes in global markets.
Electricity supply recovering
NGESO has also published its Summer Outlook and it expects to see demand recover after being suppressed in 2020 by business closures due to Covid.
The SO is managing a long term fall in demand on the high voltage transmission system as a result of more distributed generation being connected to the low-voltage network and generally lower system demand as a result of energy efficiency. That issue was highlighted by low industrial and commercial demand last year and the SO said “Managing low demand is one of the most complex scenarios our control rooms have to face and can require a greater number of actions to protect the network”.
Last summer the record low demand was 13.4GW, at which point NGESO takes action to raise demand, including by putting pumped storage into ‘pump’ mode, exporting power to Europe and using its new Operating Downward Flexibility Management (ODFM) product to provide ‘foot room’ to allow it to bring plant with the necessary inertia online. NGESO expects this year’s minimum demand to be slightly higher but it expects to have to take similar action at times. The weekend of 29-30 May 2021 is currently forecast to be “challenging”, it said, with daytime minimum demand only 1.6 GW higher than overnight minimum on 29May, and morning peak demand 4.4 GW higher than overnight demand on 30 May.
The control room will be required to take fewer actions to increase system inertia, NGESO said. This is partly because of higher demand and partly because the Accelerated Loss of Mains Change Programme (ALoMCP) has made progress in adjusting the ‘set points’ of distribution-connected generation assets so they better ‘ride through’ system disturbances. Previously they would self-disconnect, contributing increasing the risk of a cascading fault.
Reactive power tender
The system operator also has to maintain system voltage, and to do that it needs so-called ‘reactive power’ which provides energy to the system. This is location-specific and is often supplied by gas-fired power plants which typically schedule thier maintenance outages for the summer (and whose numbers are declining, see above).
NGESO will go to the market to source it for the London area. It says, “The outage pattern of reactive power providers through early May indicates that there will be a deficit in reactive power on the network across the north of London, exacerbating voltage management challenges. We will be running a tender covering this area to gain access to additional sources of reactive power.”
It will keep the outage patterns of reactive power providers under review to identify any other areas of concern.