UK eliminated electricity generation from coal in 2024. It was supposed to be replaced by renewable sources This article presents how UK power sources output changed prior to coal phase out and some unintended consequences of the transition.
Analysis is based on Digest of UK Energy Statistics (DUKES) data. Source data are organized in tables, I used Table 5.6.E Electricity supplied (gross) and Table 5.13 Net imports and utilisation of interconnectors. Some sources were renamed to make captions shorter. A group of low output sources was aggregated under name “minor”. Table below shows those sources.
| DUKES name | alias | |
|---|---|---|
| 1 | Oil | minor |
| 2 | Hydro (natural flow) | minor |
| 3 | Onshore wind | windons |
| 4 | Offshore wind | windoffs |
| 5 | Shoreline wave / tidal | minor |
| 6 | Thermal renewables [note 9] | biomass |
| 7 | Other fuels [note 10] | minor |
| 8 | Energy storage | minor |
Sources not mentioned in table have original DUKES names. Energy storage output should probably be excluded since other sources are used to charge the storage. We keep it to stick with table 5.6.E convention and aggregate with other minor sources.
Figure below shows how energy generation changed over time for each source. Import represents net import (import-export). Prior to 2010 coal, gas and nuclear were responsible for majority of generation. Then share of renewables started to grow.
Coal generation replacement
Figure below shows what replaced coal generation. Please note renewable sources like solar and wind are volatile and have to be replaced by discretionary ones in adverse conditions (no wind no sun). Annual generation total ignores it thus simplifies transition challenges. One can say biomass (thermal renewables) generation was the true replacement for coal with some power plans (probably) converted from burning coal to biomass. This source share grew significantly.
Figure below shows how generation from biomass changed over time compared to coal. We see the former surged as the latter declined.
Gas and nuclear generation almost intact
Figure below shows generation from gas, nuclear and minor sources. We can say it is somehow constant over time if compared with sources from previous figure.
Same energy sources presented relative to 1996 output volume. We can see gas output increased while nuclear decreased more than 50%. The latter can be explained by decommissioning some old units reaching end of practical lifetime.
Share in total generation figure below shows gas reached around 40% of generation share around year 2000 and stayed at that level with some fluctuations. Between 2005 and 2015 gas and coal were sort of competing/replacing each other in overall share. It’s hard to say what caused those swings.
Total energy generation drop hints industry decline
Total energy generation shows interesting behavior as we can see on figure below. It was growing until 2003, then reached plateau and from 2008 onward declined. What is interesting total generation drop coincides with coal generation reduction due to planned phaseout. Most probably industry demand reduction was driving generation drop. Coal replacement by renewables was likely to push price up and create more price volatility. In order to avoid this risk some industries, especially energy intense ones, decided to relocate (or discontinue operation in UK) thus causing electricity demand drop, generation output followed.
Volatile sources force energy import to balance grid
Figure below shows how total energy import and solar&wind generation share changed over time. Growing renewable generation pushed import up. Windless and still night requires traditional sources or import to cover missing solar&wind generation. There is nothing wrong with energy import, but if neighbors have similar weather conditions and plenty of solar&wind sources, power becomes scarce and balancing cost soars. If it reaches £5,000 per MWh some call it market manipulation. Usually desire to understand why price spiked drops once the spike passes. Unfortunately risk of next price spike grows with volatile renewables share in electricity generation.
Conclusions
This article is not supposed to prove coal is cool and renewables bad. Large scale transformation of energy supply has to be handled with care, especially if new renewable sources are volatile. Power grids are based on balancing principle: generation has to meet demand at any period. So far balancing is achieved via generation adjustment. In 2023 UK generated 34% of total electricity generation form solar and wind sources. I believe further growth will push energy price up and increase risk of balancing failure resulting in blackout. Decarbonisation targets set at political level have to be matched with available means.