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November 12, 2015

UK Must Use Diesel Generators to Back-Up Wind Turbines

November 12, 2015
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On October 4, the United Kingdom’s wind turbines produced almost zero electricity during the early morning hours. The UK has over 9,000 megawatts of metered wind capacity, but during that period on October 4, wind provided 66 megawatts—just 0.7 percent.[i] Many of these turbines are located either offshore or in the Scottish highlands, where wind is supposed to be the strongest. Because of the unreliability of these wind turbines (and solar farms), the UK government is subsidizing diesel generators over $670 million to provide back-up power.[ii] The country has 1,500 megawatts of diesel turbines registered for subsidies to provide that back-up power. The subsidies are so lucrative that solar farms are purchasing them to supply power when the sun is not shining.

The diesel generators are purchased from China and they are made to plug directly into a grid connection. Their low capital cost makes them relatively cheap given that the alternatives are either expensive or being shuttered. Natural gas is expensive in Europe and old coal plants are being taking off-line to comply with European Union climate policies.

The Wind Doldrums in the UK

The following chart shows wind capacity available for the 7-week period from September 1 to October 22. (The 66-megawatt load on October 4 is depicted below.) Besides the virtually zero wind available on October 4, there are several periods where wind was in the doldrums as shown.



In the UK, large and small wind farms are treated differently. Large wind farms (i.e. utility scale) are connected to the high voltage grid and are metered. Small wind farms, individual turbines and rooftop solar are connected to the low voltage grid (i.e. net-metered) and appear as negative demand. As a result, only 68.5 percent of the wind capacity in the UK currently is metered, while the remainder of the capacity is accounted for by demand reductions.

The Renewables UK and the Renewable Energy Foundation report wind capacity at about 13,400 megawatts. Since 68.5 percent are connected to the high voltage grid, over 9,000 megawatts are metered.

From September 1 to October 21, metered wind produced 2,018 gigawatt hours of electricity out of a possible 8,990 gigawatt hours, representing a load factor of 22.5 percent during this period. Total metered demand was 38,884 gigawatt hours or 5.2 percent of metered demand. Adding the non-metered portion, wind produced 7.6 percent of total demand. However, because wind can fall effectively to zero, it cannot offset dispatchable capacity that the system operator can dispatch whenever the need arises. Dispatchable capacity are the non-renewables—coal, petroleum, natural gas, and nuclear.

High Prices Bring End to UK Renewable Subsidies

By the mid-2020s, the UK wants to end renewable energy subsidies because of the energy tax added to the bills of British homeowners to pay for the more expensive renewable energy. Because of the “green energy tax”, 38 percent of British households are cutting back on essential purchases, such as food, to pay for their high energy bills. Another 59 percent of British homeowners are worried about how they are going to pay for their energy bills in the future.

According to a study released by the UK government in July, renewable energy subsidies represent about 7 percent of British energy bills. If subsidies are not cut, the government expects an increase in domestic electricity prices of 18 percent by 2020, driving up household bills by an additional 5 percent.[iii]

In 2014, British consumers paid 54 percent more for electricity than American consumers[iv], partly due to the renewable energy taxes. These taxes cost residents and businesses an estimated £4.3 billion (about $6.6 billion) every year.[v]

UK Turns to Diesel Generators

To avoid blackouts and brownouts, the UK has turned to mini-diesel generators (under 50 megawatts) to back-up their unreliable wind and solar power or to provide electricity when there is a rapid surge in demand—in other words, the government is providing insurance to keep the lights from going out. The need for these diesel generators has come about because old coal and nuclear power stations have been shuttered and fewer than expected new gas-fired plants have been built. While the diesel equipment is expensive to run, it is used to respond to peak demand, operating for less than 50 hours a year on average. They are designed to reach full output quickly, doing so in as little as 45 seconds.

The UK’s solution to counter the instability of wind power is known as the Short Term Operational Reserve, or STOR. The plan is to have a reserve capacity of eight gigawatts by 2020. The diesel generators will provide immediate computer-controlled back-up for periods when the wind turbines are not operating.[vi]

Green Frog Power, for example, is a firm that has taken advantage of STOR and is paid for the diesel generation even when it is not used. Green Frog was originally established to collect cooking oil which could be turned into biofuels for generating electricity but switched to using traditional fossil fuels to generate power. It has built 214 megawatts of diesel generation including a 52-generator site producing 20 megawatts of power at Neath in south Wales, a similarly sized one in Swansea and others in Hull and Plymouth.[vii]


Renewable energy has driven up electricity prices and bills in the UK, making it necessary to turn to reliable sources of energy to ensure that the lights do not go out. The expense of wind and solar and the energy tax on bills has forced the British government to phase out renewable subsidies by the mid-2020s because British consumers were being forced to give up essentials.

The government has found that natural gas plants have not materialized as quickly as expected, most likely owing to the high cost of natural gas in Europe. These gas plants were to replace coal and nuclear power plants being shuttered to accommodate European policies. As a result, the government has turned to small diesel generators to ensure that the lights stay on, subsidizing them regardless of whether they generate power. These generators not only emit carbon dioxide, but they also emit particulates and nitrogen dioxide. Thus, the UK’s renewable program has resulted in high cost energy for its citizens and the need to subsidize an entirely new generation source to ensure reliability, despite the emissions that result.

[i] Energy Matters, Flat Calm Across the UK, October 26, 2015,

[ii] Daily Caller, UK Using Diesel Generators to Avoid Blackouts From Too Much Wind, Solar Energy, November 4, 2015,

[iii] Daily Caller, UK Pledges to Ax Green Energy Subsidies, October 15, 2015,

[iv] The Statistics Portal, Electricity Prices in Selected Countries in 2014,

[v] Daily Mail, Solar power subsidies to be slashed by ministers to cut energy bills as part of a ‘big reset’ of green taxes, July 17, 2015,

[vi] Daily Mail, The dirty secret of Britain’s power madness: Polluting diesel generators built in secret by foreign companies to kick in when there’s no wind for turbines – and other insane but true eco-scandals, July 13, 2013,–insane-true-eco-scandals.html

[vii] The Guardian, UK energy bill subsidies driving boom in polluting diesel farms, May 6, 2015,

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  • wg

    If you want it renewables why you must use Diesel instead of newer modular nuclear technologies as liquid fuel molten salt reactors, there are many companies waiting just for licensing!

    • Tom Stacy

      WG – It is true that the no-emissions SMRs have the flexibility to fill that role, but think about it: If you are going to build an SMR that emits nothing and has incredibly low fuel costs compared with diesel, NG and even coal, why in the WORLD would you want to then have a clean SMR back down for some weather-dependent power source? What good is wind or solar to the environment if it displaces a perfectly clean source like nuclear? And what is the /MWh cost of SMR+wind vs. the cost of SMR as a full-time source of base load energy (and capacity)?

      • wg

        Well you nail it perfectly! All the problem is just ideological against anything “Nuclear” and how to manage to keep fossil fuels alive at all costs without most of the ignorant masses to notice it!

      • AuldLochinvar

        Worst of all, I read that in Ontario, where they get 60% of their electrical energy from nuclear, and I think about 20% from hydro (the Niagara!), the misguided ideology of wind-lovers is causing intermittent reduction of nuclear operation, and then gas turbines have to be running on standby,
        But molten salt reactors can indeed respond as well as any gas burning turbine, because the neutron-poisoning gaseous fission products are easily removed from the liquid’s surface.
        Strangely enough, liquid fuel does not melt down when the reactor is stopped, even without energy to circulate it with pumps.
        If a mix of fuel types is needed, it might be nuclear molten salt and nuclear LMFBR, and if we want hydrogen powered or electric powered private vehicles, off peak nuclear can charge batteries and electrolyse water.

  • AuldLochinvar

    It is false to say that nuclear power is not renewable. The USA has had two different designs of nuclear breeder technology that ran successfully for decades but were dropped for essentially political reasons. Both were intrinsically immune to meltdown, and the IFR, the second one, proved so by deliberate test weeks before Chernobyl. To the disgrace of both Clinton and the Sierra Club, the program was abandoned in 1994 in deference to these “environmentalists”

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