A squeeze on electricity supplies brought Ireland close to power cuts on Wednesday, it has emerged.
The Single Electricity Market Operator (SEMO) issued an amber alert to power suppliers, meaning there was expected to be enough energy to meet demand, but possibly not enough in reserve should something go wrong.
The message predicted "tight generation capacity margins" on January 6th, adding that the Republic and Northern Ireland could enter a system alert "amber state" in late afternoon and early evening.
High demand, combined with power plant shutdowns, low wind speeds and the export of a large quantity of electricity to Britain, prompted the market overseer to issue the warning.
An internal ESB memo shows that national grid operator, Eirgrid, asked the the company to start up one of its three generators at Moneypoint in Co Clare, which had been shut down, to avoid any possible risk of blackouts.
Eirgrid confirmed that the alert lasted from 4pm to 6:05pm on Wednesday, during which time demand was calculated to have hit a peak of about 5,200 mega watts (MW).
Industry sources say another electricity plant shut down during that period could have left some areas at risk of power cuts, or at least left the country with “tighter than ideal” reserves.
“This amber alert was a result of the increased system demand during the current cold weather, combined with the low amounts of renewable generation available today,” Eirgrid confirmed.
“Our neighbours in Great Britain have similar issues which has limited the capacity available for trading via the two interconnectors that link the islands.”
Bord Gáis Energy's Whitegate gas-fired generating plant in Co Cork was out of action for technical reasons. Two of three generators at the coal-burning Moneypoint facility were functioning, while the ESB said it expected to have the third on line later on Wednesday.
At the same time, two electricity lines, one connecting Co Antrim with Scotland, the other linking Co Dublin with Wales, exported 700 mega watts of electricity to Britain, where prices were higher because of a similar squeeze there.
Eirgrid owns the Dublin-Wales line while private investors control the Antrim-Scotland link.
Low wind speeds left most of the country’s renewable generators unable to produce electricity. Wind farms accounted for 40 per cent of the power used here in 2020.
Industry figures say that amber warnings are not “uncommon” but pointed out that Wednesday’s alert followed another in December.
They argue that December's closure of the ESB's two peat-fired generators, in Shannonbridge, Co Offaly, and Lanesboro in Co Longford, contributed to the problem. Both closed after they failed last year to get planning permission to burn wood alongside peat. They would have produced about 240MW of electricity, helping to underpin supplies during the alert.
State-owned Eirgrid pointed out that it works to ensure that there are enough generation reserves available to meet demand from homes and businesses.
Suppliers did not expect Wednesday’s warning to be repeated on Thursday as wind speeds were forecast to pick up, bringing renewable generators back on line. However, they warned that repeated amber alerts could hit the country’s reputation with foreign investors.
Eirgrid stressed that it worked closely with ESB networks, which distributes electricity from the national grid to homes and businesses, to monitor the situation during the alert period.
The ESB said that as of 4:30pm, 30 of its 31 electricity generators across the country were supplying power to the national grid.
The electricity market operates on an all-Ireland basis. The SEMO is a joint venture between System Operator Northern Ireland and Eirgrid.