The long term storage challenge – batteries not included

Battery storage technologies seem to be the hot topic wherever you look in the energy industry. Germany is investing heavily into domestic storage, California has a huge mandate, and the market for peak shifting and storing production is gaining the interest of consumers, pro-sumers and network operators alike.

But can battery storage really solve some of the issues faced by the growing penetration of intermittent solar and wind technology? In the short term, it probably can, but as the penetration of renewables starts to grow in major economies, many think that battery storage will at such scale either simply be too expensive, or not have enough capacity to solve some of the long term issues.

Three new technologies are now emerging as potential long term solutions, and all argue that they will be cost competitive and even displace some of the gas generation that is normally assumed to fill the gaps.

Here’s a brief look at three of them:

Chemical Energy Storage

In Germany, there is a view that the only way to provide the amount of storage needed for a nearly fully renewable grid in the long term is through chemical means – and right now there are a bunch of projects that are looking how to apply electrolysis to turn excess output from wind and solar and other generation into hydrogen and methane.

At the Fraunhofer Institute for Solar Energy Systems in Frieburg, Dr Gunter Ebert says hydrogen and methane is the only option for large scale “season storage”. Battery can provide some short term storage capacity, maybe up to 50GWh – and so can pumped hydro  (60GWh) – but he says the options are limited in Germany.

“We need a tremendous amount of long term storage – up to 70TWh,” Ebert told RenewEconomy in Frieburg last month. “That can only be done with hydrogen and methane.”

Ebert’s plan is to use caverns to store hydrogen, which can then me used for vehicles, or in fuel cells, or it can be converted into methane for use in the gas grid. Or it can be used for direct heat and power generation, as this rather complicated graph shows.



As Craig Morris reported on the Energiewende blog last week, the German company Thüga has exported the first hydrogen from electrolysis to the natural gas network.  The firm says it plans to go into official operation at the beginning of 2014 after a test run. The practical test under operating conditions will last for nearly 3 years until the end of 2016. The unit under investigation has a power capacity of 315 kilowatts and can produce 60 cubic meters of hydrogen per hour.

Ebert says there are  still many possibilities about how such a scheme could be put together – but some form of long term storage will be needed after 2020, when the share of renewables grows beyond 40 per cent, and more thermal generation is sidelined.

Compressed Air Energy Storage


The second big technology that is being looked at is compressed air energy storage, known as CAES. The Boston-based firm General Compression last year opened a 2MW/500MWh pilot plant in Texas last year, and its representatives have made three trips to Australia this year to talk to utilities, renewable energy developers, and government representatives about their technology.

Development officer Peter Rood says CAES would work best at the utility-scale with 10MW to 100MW. It requires below ground storage – either natural or man-made – and could work with storing the output of wind energy, or even as a “storage bank” for thousands of rooftop and other distributed solar systems.

Rood told RenewEconomy during a visit to Australia last week that CAES will help wind energy act like a flexible gas-fired power station, providing base-load and peaking generation when needed – storing energy produced on some windy days for use later in the week – or even the month.

That means it would not only be able to mimic the services delivered by gas turbines, it would be able to compete with even combined cycle gas turbines as gas prices head above $10/mmbtu, where they are surely heading in Australia as the gas market heads towards export price parity.

“I think there will be a pretty compelling case to build wind plus storage,” he says, noting that a lot of thermal generation is ageing, and a renewables-focused energy system will need storage and other ancillary services, such as frequency, that such a system could provide.

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