Though still little known, compressed air energy storage (CAES), a form of grid-scale energy storage which works by compressing air and expanding it again when needed, has been around for decades, but has been a vastly underused tool. 

One of the major challenges of renewable energy over the years has been its seasonality and issues of storage. Sources rely on weather conditions and cheap, reliable and longer-term storage has been a challenge.

Back in 1991, a facility was developed in Alabama, USA, while as long ago as 1978, a plant was built in Huntorf, Germany, pioneering the technology. However, both still relied on burning fossil fuels, using gas fired power plants for generation. 

Powered by the PowerSouth Energy Cooperative, the Alabama project at the McIntosh facility, can generate as much as 110 megawatts of electricity within 14 minutes of startup during peak periods.

Scientists are revisiting the use of compressed air now that costs are coming down and technology has improved. Storelectric, a startup in the UK, is one company capitalising on this and has won awards internationally. Unlike the gas-powered plants of years ago, the newer versions of the technology extract the heat of compression and store it separately, to reuse for the expansion phase, eliminating the need for gas burn and in turn, emissions.

Using salt caverns, which are in plentiful supply in areas of the UK and internationally, but can also be made cheaply, the air can be harvested for use at times of higher need and price, and can be harnessed at short notice. 

Partnering with the likes of Price Waterhouse Cooper, the company has also pioneered the technology in the Netherlands, after winning a competition run by Dutch energy company, NAM, which is jointly owned by Shell and Exxon Mobil. The entities will be exploring the idea of repurposing oil and gas infrastructure for use in energy storage as well as building new underground storage sites in the Netherlands and under the North Sea, where energy from wind farms and onshore solar power plants could be stored.

The North Sea has also been the focus for researchers in Scotland, where universities have been working with engineers to better utilise underground storage. Some time ago, the Scottish Government concluded that other than hydro power, CAES is “the only other technology with the current ability to deliver large scale energy storage”. 

Research at the University of Strathclyde published in January, found that the North Sea’s seabed could provide a vital storage place for renewables. Trapping the air in porous rock formations, using electricity from renewable technologies, could see the compressed air later released and used to drive turbines generating large scale electricity.

The research suggests it could store enough compressed air to meet the whole of the UK’s electricity needs during winter, when demand is highest, harnessing steady and reliable sources such as wind and tidal turbines.

The porous rocks beneath the sea could store one and a half times the UK’s typical energy demand for high use months January and February, according to engineers and geoscientists at the Universities of Edinburgh and Strathclyde. 

The University of Strathclyde system generates compressed air through a motor powered by renewables. The air is stored at high pressure in the pores of the sandstone, in deep wells drilled into the rock. Easily accessible, during times of energy shortage, this pressurised air can be quickly released from the well, in turn powering a turbine, creating the electricity which is then fed into the power grid. 

It is very similar to the process using salt caverns and Dr Julien Mouli-Castillo, of the University of Edinburgh’s School of GeoSciences, who led the collaborative study, said it would allow energy harvesting during the summer months, to fuel the cold winter months. He said it was still an expensive option, though viable, to help ensure the UK’s power supply remains resilient through the seasons. More research he says is needed, to help bring costs down.

The solutions are very much needed, globally. A recent study by LUT University in Finland and the Energy Watch Group (EWG) in Germany, claimed that electricity consumption in 2050 will account for more than 90% of the primary energy consumption with the near ceasing of fossil and nuclear energy. But efficient storage, is key. The report spoke specifically to MENA region needs and said between 2015 and 2050, there will be a major shift from fossil fuels to wind and solar power, with some infiltration of hydropower.

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