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Carbon Brief Staff

Carbon Brief Staff

10.09.2013 | 2:50pm
ScienceInvest in storage to reap renewables’ bounty
SCIENCE | September 10. 2013. 14:50
Invest in storage to reap renewables’ bounty

Giant batteries the size of suburban semis could start popping up across the UK to balance out intermittent renewable electricity generation – but not if governments get smart about energy storage, a new report suggests.

As any cyclist currently packing sunglasses and waterproof trousers knows only too well, the UK gets a mixed bag when it comes to the weather. Sporadic gales and fleeting autumnal sunshine can be great for renewable electricity generation, but intermittent renewable electricity can make balancing the grid difficult. In such moments, technicians have two choices: store the excess power for later or ask sites to power down.

The latter has led to some unfavourable headlines, but a new paper from Stanford University suggests it’s sometimes more efficient to stop generation than invest in saving electricity for still, grey days.

Intermittency

The new study says it currently takes too much energy to build and maintain battery systems to make storing some renewable energy worthwhile. It looks at the ‘energy return on investment’ (EROI) – the total energy expended in constructing and maintaining the installations, and generating and storing electricity – of wind and solar farms.

The paper shows that if large battery arrays are included in the calculation, the return on the original energy investment significantly decreases. The overall payoffs are slightly better for solar than wind energy, the study finds.

This presents a tricky dilemma for the government as it tries to ramp up renewable generation and reduce emissions without overloading the grid. The paper’s lead author, Charles Barnhart, told PhysOrg:

“If a battery’s energetic cost is too high, its overall contribution to global warming could negate the environmental benefits of the wind or solar farm it was supposed to support.”

That doesn’t mean the UK should abandon storing renewable electricity altogether, however. Barnhart tells us, in some cases, “storage holds many advantages [over switching off] that go beyond a simple energetic calculation. Energy availability can be crucial in specific situations, like after superstorm Sandy last year”.

So the paper doesn’t imply the government always has to pay windfarms to sit idle on blustery days. Instead, it suggests storage technology needs to be developed to help countries cope with the pressing challenge of balancing the grid as they transition to low carbon energy systems.

Storage solutions

The government has pledged to attract £110 billion of investment in the UK’s ageing energy infrastructure, with a veritable smorgasbord of storage technologies it could give a piece of the action to.

One option is to invest in improving storage facilities. For example, increasing the amount of energy batteries can store and for how long.

Alternatively, the government could invest in ‘pumped storage’, where excess electricity is used to pump water into lakes to be released through a hydro-dam when renewable generation is scarce.

Pumped storage is pretty efficient, so if all renewable energy could be stored in that way it would rarely be necessary to ask the generators to switch off, Barnhart says. Unfortunately, hydro dams take up a lot of space so there are environmental constraints on how much pumped storage an energy system can include.

Finally, the government could invest more widely in upgrading the grid infrastructure – extending interconnectors across the country and with neighbours in Europe to make sure electricity can be delivered to where there is demand, and installing smart meters to help match demand to supply, for instance.

Trade body RenewableUK’s Director of Policy, Dr Gordon Edge, says this final option should be the UK’s top priority as “battery storage technology is advancing all the time, but any solution to large-scale storage is a long way off… Improving our grid infrastructure so that it can make better use of wind power is an immediate and pressing task”.

So while National Grid may get a bit of a headache trying to balance the grid as more renewable electricity comes online, the government has plenty of investment options to make the task easier.

Shifting focus

The Stanford University paper is a timely reminder that energy policy isn’t always about getting more capacity online – it’s also necessary to work out what to do when it’s there. It shows that while renewable generation itself isn’t really a problem, the government does need to think carefully about how to deal with the electrical bounty on those glorious (if rather breezy) autumnal days.

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