Huntorf
Large scale Compressed Air Energy Storage (CAES) site reliably running since the 1970s using SSS Clutches to store and release energy and provide grid support.
Huntorf was the 1st commercial scale diabatic Compressed Air Energy Storage (CAES) plant in the world. The SSS Clutches at Huntorf have been operational for over 40 years without the need for service and the plant rating has been upgraded from 290MW to 320MW with no change to the SSS Clutch.
During off-peak load periods, a motor consumes power to compress and store the air in underground salt caverns. Later during peak load periods, the process is reversed and the compressed air is mixed with natural gas and combusted to produce electricity. A gas turbine normally uses approx. 2/3 of the power output for compressing the combustion air, so when the compressor is supplied from the stored compressed air and separated from the expander, the power rating is 3 times larger. The plant is more efficient and emits less pollutants as it consumes 1/3 of the natural gas per kWh compared to a conventional combustion turbine.
The 340T and 272T SSS Clutches allow the system to switch between energy storage mode and power generation mode. In energy storage mode the Motor / Generator will accelerate and engage the Compressor through the compressor clutch, the expander clutch will disengage as the Motor / Generator is rotating faster than the Gas Turbine. In power generation mode the Gas Turbine will accelerate and engage the expander clutch to the Motor / Generator, the compressor clutch is automatically locked-out so the Compressor is not engaged.
Whenever the generator is synchronised i.e. whilst in energy storage or in power generation mode the system also stabilises the grid by supplying or absorbing reactive power as well as providing inertia to stabilise the frequency and fault current in the event of electrical system faults. The Generator can also be left synchronised to the grid with both SSS Clutches disengaged so it can act as a Synchronous Condenser.
The increase in renewable sources of electricity has highlighted the need for bulk energy storage solutions like CAES, which have much larger capacity and longer cycle times than batteries and can cover hours of demand. A number of new CAES sites are in development globally.