Storing energy in compressed air has been around for decades, and has been used world-wide in many systems.

When power is abundant and demand is low, it’s drawn from the grid to compress air into a salt cavern hundreds of metres underground. When the power is needed, the air is let out from the cavern to regenerate the electricity.

Salt caverns have been used for many decades to store natural gas because not only are they naturally hermetic, but also salt undergoes plastic flow under pressure, so it seals any cracks that may occur. And what is safe for gas is safer for air.

There are salt basins globally, in which caverns can be made cheaply and easily.

Flexible Generation Plants

• Zero or low emissions
• 20MW to multi GW
• 4 hours to multi-day
• Balancing and ancillary services
• Enables renewables to power the grid

Optimising Wind and Solar

• Intermittency into dispatchable electricity
• Co-location with renewables also enables the generator to avoid grid access charges on its output energy, storage to avoid them on charging energy and storage to avoid capital costs of grid connections
• Increases revenues
• Eliminates curtailment
• Cuts grid connection costs

Grid Investment Deferral

• Relieves grid congestion at choke points
• Reduces local overloads at interconnectors
• Reduces overloads at wind farm landfalls
• Co-location with renewables benefits grids by greatly reducing reinforcement and adding real inertia 24/7
• Well placed for major generation and demand

The energy transition is essentially about replacing dispatchable (i.e. on-demand) power generation with intermittent, asynchronous renewables. It was recorded following Mark Howitt’s participation in a panel event on “Markets and policies for future flexibility needs”. In this podcast, Mark talks with Laura Sochat of Charles River Associates, a global energy consultancy, about what this entails, its consequences and what can be done about it to enable the energy transition to be affordable, reliable and resilient.

Currently there are only 2 technologies that have proven references of over 30years. These are Pumped Hydro Energy Storage (PHES) and Compressed Air Energy Storage (CAES). Other technologies are developing but are severely hampered by longevity issues, size and duration restrictions. As a project developer Storelectric Ltd is focused on investing in proven, scalable and competitive concepts. PHES while well proven is geographically constrained and very much more expensive than CAES with the added difficult of identifying suitable locations that have not otherwise been built upon or rejected. This leaves CAES which is proven, competitive, less geographically constrained and has the potential for scalability at both the distribution and transmission scales.

Huntorf, Lower Saxony, Germany

Compressed air energy storage (CAES) has been in operation since 1978 in Huntorf in Germany, and since 1992 in McIntosh, Alabama, USA. Both of these plants regenerate the electricity by feeding it into a gas-fired power station, roughly tripling the efficiency of the power station.
When compressing the air it heats up. When expanding it again, heat needs putting back into the air. Both Huntorf and McIntosh do not utilise the heat from the compression process, leading to only 42% overall efficiency in Huntorf and 54% in McIntosh (the difference being because McIntosh’s power station is Combined Cycle).