Scottish wind farms were paid to curtail nearly 40 percent of their scheduled output during the first six months of the year because the electricity could not be used locally, stored, or transmitted to areas of higher demand.

According to research from energy analytics company Montel, the unused output in northern Scotland cost 117 million pounds ($157 million) and amounted to 4 terawatt-hours, which would have been enough to power every household in Scotland for six months, reported the Financial Times newspaper on Monday.

Wind farms in northern Scotland represented 86 percent of the total 4.6 terawatts of electricity switched off across the United Kingdom during the period, which was an increase of 15 percent compared to the same period last year.

The FT said the figures highlight the urgent need for expanded power network capacity across Scotland, to allow for the power to be channeled to southern consumers, and fuel concern over the design of the UK's rapidly evolving electricity system.

Fintan Devenney, a senior analyst at Montel, called for collaboration between policymakers and energy companies to achieve solutions.

"Curtailed volumes of electricity are rising on average and may continue to do so as more renewable capacity comes online," said Devenney.

The increase follows rapid wind farm development in remote Scottish areas, particularly the Moray Firth off the northeast coast, where local demand is low and where there is a lack of infrastructure to move power output to southern consumers.

The National Energy System Operator, or Neso, must regularly pay remote wind farms to pause generation while simultaneously compensating gas-fired plants elsewhere to increase output, ensuring the grid remains balanced and consumers receive their contracted power.

"Chronic under-investment in the grid over the past few decades has resulted in these constraint payments," one industry executive told the FT. "Grid upgrades will provide the capacity to help transport the power to demand in the south."

Montel's data shows the 117 million pounds Neso paid out in the first half of the year to halt production at northern Scottish wind farms was largely compensation for the subsidies they would have received for actual power generation. Montel said these expenses are passed on through customer electricity bills.

The Department for Energy Security and Net Zero maintains Neso's assessment demonstrates it was feasible to produce clean and more cost-effective power by 2030, even when accounting for constraint payments.

A spokesperson said the government was "delivering the biggest upgrade in Great Britain's electricity network in decades, which will minimize constraint costs".

Scottish Energy Secretary Gillian Martin said: "I have been clear that the current UK energy system is not fit for purpose. Significant investment is required to achieve a clean power system."

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