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Project profile: Flywheel energy storage

An innovative energy storage technology using a flywheel developed in Qatar is being installed on remote Scottish Islands

Ben Sampson
February 18, 2014

From the deserts of Qatar to the chill winds of the Isles of Fair and Eigg in Scotland, Williams F1 has been searching high and low for applications for its Kinetic Energy Recovery System, originally designed for use in its race cars.

The technology has been in development in the Middle East since 2009, when Williams opened its technology centre in Qatar. KERS was destined for use in public transport systems such as the metros which are built in cities throughout the region.

But last month the focus of the project shifted dramatically - in geographical terms. Thanks to funding from the Department of Energy Climate Change in the UK, engineers are to install the flywheels on the Isle of Eigg, north of Skye and the Fair Isle, which is located between the Orkney and Shetland Islands in the North Sea.

Both islands rely heavily on renewables for their power and have electricity grids in the hundreds of kilowatts range. The Fair Isle is powered by wind turbines and a diesel generator. The Isle of Eigg uses a wider mix of renewables, including solar, hydro and wind power as well as lead acid batteries to store excess energy and smooth the flow of power. 

Wind turbines supply the electricity on the Scottish Isle of Eigg

Wind power is used for most of the day on the Fair Isle. Diesel generation is only used for guaranteed hours when the wind drops, but there are issues in power quality and frequency, due to the variations in wind speed. 

Less than one hundred people live on each island and blackouts are a common occurrence. Matthew Burke, chief engineer of Energy Systems for Williams, says: “The power quality aspect is one of the key drivers for the Fair Isle. From the islanders perspective we can reduce the number of blackouts which are a result of when the wind drops and the diesel generators start up. The system will increase their quality of life as well as reducing costs and emissions.

“In the Isle of Eigg, they have a mix of renewables and our focus is to improve the battery life by using the flywheel to perform more of the frequency control and relieve the battery from that activity.”

The islands are providing a test bed for the flywheel energy storage technology. The installations in Scotland are the first time the technolgoy has been used for a stationary application in the energy sector. 

Each flywheel has a 200kW capacity and a 90 x 90cm footprint. The main advantage of the flywheel is its longevity. It has around 10 million charge / discharge cycles, making it suitable for applications with high duty cycles over batteries and other electrical equipment.

The flywheel uses a permanent magnet with an integrated composite rotor that sits outside of the stator. The unit is placed inside an evacuated containment system to ensure low drag losses. Passive magnetic bearing technology means the rotor and the stator never physically touch. Burke says the unique part of the machine is the “magnetic loading composite” used in the rotor. This is mixed into the rotor during manufacturing and the magnetic pattern is then imprinted onto it. This has the dual benefit of  making the unit safer and reducing the number of eddy current losses, so power can be put through the rotor more frequently. “This is what makes it suitable for smoothing power from intermittent renewables,” he says.

“We’re not storing energy for use hours later. The flywheel will act as a short term energy buffer for the high energy throughput and provide support to help stabilise the grid and ensure a tighter frequency,” Burke says.

Engineers have so far installed logging equipment to record data from the Islands’ electricity grid. This data is being used at Williams’ laboratory in Grove, Oxfordshire. The flywheel is connected to hardware that recreates the Island’s electricity grid, using the logged data recreate scenarios and verify the flywheel’s predicted performance . “It’s a classic automotive development methodology, but in a very different sector,” says Burke. “It lets us set up the flywheel’s controls and calibration most effectively and begin measuring what the performance improvements will be. We can derisk the program sufficiently to have high confidence in their performance.”

The next step is to install the system during the summer this year when the weather and daylight is at its best. Williams is currently working with the islanders to assess the best location for the flywheels. Once installed they will be in place for about a year, to give performance details throughout the four seasons and in varying wind conditions. They are designed to last 20 years.

“We see a real need for the flywheels in islands like Fair and Eigg now. But as the penetration of intermittent renewables increases, the role of energy storage to provide a reliable energy grid and supply will only grow,” says Burke.

The flywheels can be banked together for larger grid applications. Other uses are also being pursued in the transport sector. From Qatar to Eigg, where the flywheel will appear next is not known, but its use somewhere outside of F1 looks increasingly likely.
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