Motor turns generator in new power storage facility
14 June 2011
Renewable energy is intermittent and as the infrastructure grows, energy storage systems must be available to fill gaps in the supply or to meet high peak demand. A novel way of storing electric power has been developed by Highview Power Storage. The company’s ‘CryoEnergy’ system runs during low-tariff periods and uses the cheap electricity to operate an air liquefaction plant, storing the liquefied air in an insulated tank at -196oC.
When the stored energy is needed, the liquefied air or liquid nitrogen is released from the tank, pumped while still liquid to a high pressure and allowed to warm and expand to its gaseous state. This high pressure air is then used to drive an expansion turbine connected to a standard ABB induction motor, which acts as a generator. The 500kW unit that is currently installed on a pilot module hosted by Scottish & Southern Energy is large enough to supply the electricity needs of several hundred homes.
Highview chief executive Gareth Brett says the application required a simple, robust machine with no special starting or cooling requirements and the ABB range offered exactly what was needed. Also, the price was right and delivery was within an acceptable timeframe.
ABB supported the project with advice about the motor’s operation. “Our prime mover is very sensitive to torque transients as well as speed excursions,” says Mr Brett. “ABB was able to provide transient torque plots under fault conditions, as well as the torque speed relationship at a part of the curve which would not normally be looked at for a motor application.”
Highview has plans to scale up the system to the 3 to 5MW range: “We will probably need to change to a synchronous generator, but based on past performance we will certainly be talking to ABB again about that scope of supply.”
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