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Tim Dodd

05.08.2013 | 1:45pm
ScienceDiesel generation won’t be used as renewables backup, despite critics’ claims
SCIENCE | August 5. 2013. 13:45
Diesel generation won’t be used as renewables backup, despite critics’ claims

Making sure there’s always enough electricity for us all to enjoy that after-work cup of tea is a problem old as your grandma’s kettle. And as the UK ramps up renewable electricity generation, new plans are needed to guarantee power supply can meet demand when the sun isn’t shining and there’s no wind to spin turbines. The problem is, not everyone is keen on having to pay for what they see as unnecessary extra renewables backup.

The company that owns the UK’s supply network, National Grid, has to make sure electricity can get wherever it’s needed, whenever it’s wanted. This means it has to keep some power generation in reserve in case renewable sources can’t generate, or if large fossil fuel power plants unexpectedly fail.

Gas plants are the most common form of backup generation, and this has typically been what renewable energy critics have focused on – saying it’s a waste of money to keep gas plants online just for when renewable energy supply is low, when they could be generating all the time. But recently they’ve turned their attention to another backup source: diesel generation.

At the moment, National Grid can ask large buildings like hospitals or government offices to switch on their small diesel generators – which they keep just in case there’s a power cut – under a scheme called the Short Term Operating Reserve (STOR). The Department of Energy and Climate Change (DECC) tells us that last year, approximately 496 megawatts of diesel generation were available through STOR.

Critics claim government plans to ramp up renewable generation mean the diesel generators will be needed more frequently, and this could cost consumers £1 billion a year by 2015. But the plans have been blown out of proportion – the diesel scheme isn’t meant to back up renewables, and it doesn’t look like it’s going to cost anywhere near as much as critics suggest.

Fossil fuel failures

Over the last couple of months, three articles have been published in the Mail on Sunday and Sunday Telegraph claiming consumers will soon be paying through the nose for diesel to back up renewable generation.

STOR is mainly in place in case large fossil fuel power plants fail, however, not to back up wind and solar power. National Grid’s head of energy, Richard Smith, tells us it’s actually fairly easy to predict when renewable generators won’t be able to provide power. And when they can’t, National Grid calls on conventional, cheap forms of generation – such as gas plants – to back up renewables – not STOR.

National Grid tells us STOR is instead used as short-term cover for when large power plants – often coal, gas or nuclear – unexpectedly stop working.

Alastiar Martin, Chief Strategic Officer for demand side reduction provider, Flexitricity, says National Grid has called on its STOR generators to provide backup due to a renewable generation dip about three times. That’s out of 2,500 requests since 2004. The rest have been to cover large power outages or unexpected peaks in demand.

Martin says STOR is a “premium service for occasional use in tight circumstances”. So it’s extremely rare that diesel generators are used to back up renewable generation, despite what renewable energy critics say.

Better alternatives

And diesel generation is only a small part of STOR. Last year, only 18 per cent of available STOR power generation was diesel, DECC says. What’s more, it’s not likely to grow much, as more efficient forms of power generation generally push diesel to the end of the backup queue.

STOR participants, Flexitricity and Kiwi Power, both say that while about 40 per cent of their portfolios include diesel generation, it’s rarely used. Martin says that for every megawatt hour of diesel generation Flexitricity provides, 10 megawatt hours come from more efficient combined heat and power (CHP) plants. While they also burn fossil fuels, like diesel generators, they convert the normally wasted heat into power.

Martin says:

“[The economics of providing peak electricity mean] diesel is the capacity of last resort… and that’s going to continue regardless of what happens to wind or any other source of renewables”.

That’s because it doesn’t make sense to bring expensive small scale diesel online if more efficient power plants are available.

Unrealistic projections

Since STOR isn’t really going to be used to back up renewables – and diesel generation is only a small part of the scheme – it’s unlikely it will cost anywhere near as much as the £1 billion critics project.

National Grid tells us “STOR is a £100 million-a-year service” – ten times less than has been suggested.

The £1 billion figure certainly comes as a surprise to the companies that would benefit from such a boom. Ziko Abram, Director of KiWi Power, says he’d be “surprised” if that were the case. Martin says the £1 billion figure is simply “not a realistic projection”.

So while renewables do need some fossil fuel backup, diesel generation is a long way down the list of generators National Grid will call on. Instead, STOR is in place for when fossil fuel plants fail to provide power – not wind turbines.

That’s likely to continue to be the case regardless of how many wind turbines are built, as diesel generation is expensive and National Grid already has plenty of cheaper alternatives.

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