Seasonal deployment – powering the clean energy revolution whatever the weather

Britain’s electricity system has undergone such radical changes that carbon emissions from the sector are now so low the ‘dirtiest’ hour of generation is cleaner than the average hour from just a few years ago.

The latest Electric Insights report, produced by researchers at Imperial College London in collaboration with Drax, analysed data from January to March 2017.  It reveals the dirtiest hour for generation during this winter period was at 8.30pm on the 16th January.

On that cold and calm winter evening 424 grams of CO2 were released per kWh (g/kWh). Compare this to the average hour from 2009 – 2013 when 471 per kWh (g/kWh) was being produced.  In fact, during the first quarter of 2017, emissions dropped by 10 per cent compared to the same period in 2016 and a massive 33 per cent from Q1 in 2015.

While this year’s mild winter played an important role in reducing emissions, the reduction in the use of coal should not be underestimated. Policy levers like the carbon tax continued to push coal off the system and the dramatic growth in renewables also reduced its role.

In January to March 2017:

  • Output from coal generation fell by 30% compared to the same quarter in 2016
  • Renewables hit new energy production records: wind – 11.3 TWh, biomass – 4.4 TWh, hydro – 1.6 TWh
  • Solar hit a new record peak output: 7.67 GW

Dr Iain Staffell, of Imperial College London, said: “The dirtiest hour in the first quarter of 2017, in terms of carbon intensity from electricity, saw 424g of CO2 produced per kWh – that would have seemed clean just a few years ago. The average from 2009 to 2013 was 471g/kWh.

“However, coal output – largely driven by the carbon tax – has fallen 82% in the last four years and has been replaced by mid-carbon gas, low carbon biomass and imports, as well as zero carbon wind and solar.

“Together these have driven decarbonisation in line with, or even slightly ahead of, the country’s targets – which are the most ambitious in the world.”

The rise of intermittent renewables like wind and solar, mean that gas, coal and biomass fired power stations are often not required throughout the day. They are instead being used to power up and down according to the weather and peaks in demand, making flexibility more important than ever before.

While in the winter months we are witnessing record breaking changes in the generation mix, the new data from the first quarter of 2017 suggests that this summer is likely to witness an even more dramatic shift.

In the last weekend of March – for the first time ever – we saw lower daytime than night time demand on the grid. This phenomenon was largely driven by the dramatic rise in solar. Both solar panels and small scale onshore wind are ‘invisible’ from the grid.  This means that effectively what they produce reduces what the grid is required to deliver.

During March, demand on the transmission system was 2.3GW higher at 9am than at 1pm, when solar panels achieve maximum output.  Dr Staffell predicts that based on previous data this gap is set to double this summer (June).

Dr Staffell explained that whilst this quarter was a record-breaker for all renewables, including solar, the sun often isn’t shining at the very times when the country needs the most power – when factories and offices are starting up in the morning – and when people settle down at home for the evening.

Dr Staffell said: “How we manage this changing pattern in demand requires a major change in how power stations operate.

“Solar output is still relatively hard to forecast in advance. Technologies that are flexible and can be turned on and off quickly, such as gas or battery storage will help accommodate these changes.”

Andy Koss, Drax Power CEO, said: “We continue to see dramatic changes in both the generation mix and new demands on the system, making reliable, flexible power increasingly important.  Seasonal changes are highlighting the changing role that power stations are now playing.

“This new role is set to increase and we will need more nimble technologies which can be up and running at the flick of a switch – like the rapid response gas power stations we are developing.

“This kind of flexible and responsive power generation is vital during times of system stress, such as when the sun isn’t shining or the wind doesn’t blow – it will also enable more intermittent renewables to come onto the grid, replacing coal and making the whole system cleaner.”

Electric Insights will be published once a quarter, and is supported by an interactive website – – which provides live data from 2009 until the present. The data sources and methodology used in Electric Insights are listed in full on the website.

Commissioned by Drax Group, owner and operator of the UK’s largest power station and Europe’s biggest biomass-fuelled power plant, the report will be delivered independently by Dr Iain Staffell from Imperial College London, facilitated by the College’s consultancy company – Imperial Consultants.

The full report can be read here: 


Notes to editors

  • Electric Insights reports that the carbon intensity of electricity averaged 284g/kWh during the first quarter of 2017. It ranged from just 102g/kWh on a windy Sunday night in March to 424g/kWh on a cold and calm January evening when coal output was high.
  • The lowest carbon intensity hour was 4.30am on March 19 when there was 0.78GW of coal generation, 4.4GW gas, 7GW nuclear and 12.0GW renewables.
  • Previously, minimum demand was always during the night and daytime demand never came within 5GW of the night time minimum. However, this gap narrowed to 2.4GW in 2015 and on March 25th 2017 it disappeared completely. This meant demand on the national grid was lower during the daytime than it was over night for the first time ever.
  • All forms of renewables had a record breaking first quarter of 2017:
    • Wind farms recorded their highest quarterly output, generating 11.3TWh over the quarter, beating coal output for the last consecutive four quarters.
    • Biomass also hit a new high of 4.4TWh, meaning the fleet ran at 95% of full capacity over the quarter, higher than any other technology has achieved in the last decade.
    • Hydro hit 1.6TWh – 4% above its previous best in 2014.
    • Solar reached peak output of 7.67GW at the end of March – enough to power a fifth of the country at the time.

About Electric Insights

  • Electric Insights Quarterly was commissioned by Drax and is delivered independently by a team of academics from Imperial College London, facilitated by the College’s consultancy company – Imperial Consultants. The report analyses raw data that are made publicly available by National Grid and Elexon, which run the electricity and balancing market respectively. Released four times a year, it will focus on supply and demand, prices, emissions, the performance of the various generation technologies and the network that connects them.
  • Along with Dr Iain Staffell, the team from Imperial included Professors Richard Green and Tim Green, experts in energy economics and electrical engineering, and Dr Rob Gross who contributed expertise in energy policy. The work to date has revealed scope for further research in this area, to inform both government and organisations within the energy industry.
  • The quarterly reports are backed by an interactive website which provides live data from 2009 until the present. It was designed by The Economist Group’s independent data design agency, Signal Noise.

About Drax

Drax Group plc plays a vital role in helping change the way energy is generated, supplied and used as the UK moves to a low carbon future. Drax operates the largest power station in the UK, based at Selby, North Yorkshire and supplies 7 percent of the country’s electricity needs. The energy firm converted from burning coal to become a predominantly biomass-fuelled electricity generator. Drax is the biggest single site renewable generator in the UK and the largest decarbonisation project in Europe.  Its 2,300-strong staff operate across three principal areas of activity – electricity generation, electricity sales to business customers and compressed wood pellet production.

The Group includes:

Drax Biomass, based in the US and manufactures compressed wood pellets produced from sustainably managed working forests.

Haven Power, based in Ipswich, providing businesses with electricity.

Opus Energy, based in Oxford, Northampton and Cardiff, providing electricity and gas to businesses.

Billington Bioenergy, based in Liverpool with depots across the UK, is one of the leading distributors of wood pellets for sustainable heating in the UK.

For more information visit


Ali Lewis
01757 612 165
[email protected]

Lynda Stamford
Imperial Consultants
020 7594 2069
[email protected]