Q2 2017: Soaring solar power

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by Dr Iain Staffell – Imperial College London 

Solar power is reaching new heights in Britain, and having a growing influence on system operations. 

For eight hours over the quarter, solar power produced more power than all fossil fuels combined. It set two new records for instantaneous output: supplying 25% of demand on the 8th of April, and producing 8.91 GW on May 26th. Over the quarter, solar panels produced 4 TWh of electricity, 12% above the previous maximum set back in 2015.

Solar panels rely directly on the levels of sunshine, so their output varies across the seasons and also from one day to the next. The figure below-left shows the maximum solar output during each day over the last 18 months. This peak output normally occurs between midday and 2 PM, and can vary by up to 5 GW from one day to the next if the weather suddenly shifts.

Solar output is depressing the need for other generation during afternoons, which we explored last quarter. California coined the phrase ‘duck curve’ to describe the shape of their daily demand profile as more PV is added. The figure below-right shows what might be better described as Britain’s ‘camel curve’. The increasing amount of solar power creates two humps in the profile of net demand which other power stations must produce, one at 9 AM, one at 9 PM. The difference between 2013 and the 2021 prediction is equivalent to the country’s entire nuclear fleet powering up for a few hours every sunny afternoon.

The UK has 12.4 GW of solar PV capacity installed; more than many analysts once thought would be installed by 2050. The majority of this capacity (57%) is concentrated in 1,400 large ground-mounted and standalone farms, averaging 5 MW each. The rest is distributed over 910,000 small rooftop systems less than one-thousandth the size.

Left: the peak output (in GW) from solar PV during each day in 2016 and 2017

Right: demand in each half-hour, averaged over the 10 sunniest days of Q2 2017. Coloured lines show demand on the transmission system, net of embedded wind and solar farms1

Authors: Dr Iain StaffellProfessor Richard GreenDr Rob Gross and Professor Tim Green

1: Based on National Grid’s Future Energy Scenarios, with projections of 14, 16 and 18 GW of solar capacity being installed by 2019, 2021 and 2023 respectively.

Live Grid Data