Current forecasts indicate peak solar output for Friday to be just under 12GW. This is close to the UK’s total capacity for installed solar generation. It is also 3.5GW above the previous high for the year. Nearly 5GW of the installed capacity is supported by the Feed-in Tariff (FiT). The majority of these panels are installed on homes around the UK.
This expected jump in solar generation will reduce demand on the national transmission grid. Houses and business that would have taken electricity from the transmission network are instead able to generate their own.
Day-ahead power prices for Friday fell to eight-month lows of £37/MWh, to reflect the forecasts of low demand and high renewable output.
With solar output only available during daylight hours, the bright weather conditions have created an unusual demand curve for Friday. Peak consumption for the day is 8 o’clock in the morning, instead of in the early evening. As solar output rises through the day, transmission demand is forecast to fall to a low of just 25GW by 3pm. The traditional evening rise in demand is also going to be lower on Friday as the Bank Holiday weekend begins. The high of 32GW would be the lowest weekday demand peak for the year so far, and down nearly 5GW from the previous week’s high.
On Wednesday 17 May, cloudy weather conditions meant peak solar output was just 2GW. With lower embedded generation, demand on the transmission grid increased, reaching a high of 37.5GW at 6pm.
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Could we see another day of zero coal use?
Weekend power prices have also fallen to their lowest level since September 2016. Peak demand is expected to reach just 27GW on Saturday. Higher wind generation, of 4.5GW, will help boost renewable output. This will significantly reduce the need for gas and coal power stations in the generation mix. There is therefore the potential for another day of zero coal use. With nuclear power stations expected to provide over 8GW of electricity this could lead to a potential localised use of National Grid’s Demand Turn Up scheme. This is available for operation on summer weekends between 1pm and 4pm to minimise power oversupply on the grid. Demand side providers are paid to either increase consumption or reduce embedded generation during periods where supply may be higher than demand.
With five months of summer left to run, it is likely solar output will continue to play a significant role in the generation mix. This would continue to impact on power demand and pricing for the rest of the season.