Flywheel operates within a vacuum
The M32 long duration flywheel operates within a self regulated vacuum. The main purpose of the vacuum is to reduce friction with air and particles on the rotor. Key Energy gets a lot of questions around the operation and range of this vacuum.
The vacuum environment
The vacuum environment is created using a standard rotary vane vacuum pump. The pump requires approximately 250W of power for normal operation. The Vacuum Pump normally operates during daytime from excess solar energy. It is set to maintain a pressure between 7mTorr to 35 mTorr. Initially, the pump is set-up to run for 1 hour each day to keep the vacuum consistent, however we find that after a few months of operation the vacuum stabilisies and the vacuum pumps require much less operation.
The vacuum stabilisies test
We conducted a test to see how long the vacuum would be maintained in the Flywheel housing without running the vacuum pump.
In the test result below you can see that the vacuum pressure has a slight fluctuation each day during normal operation. There is one vacuum pump operation on the 20/11 ( 20th of November). The vacuum did not need to run until 30 days later ( 19th of December). See below Image
Conclusion
The vacuum is very stable on the flywheel and only required 1 to 1.5 hours runtime for a 30 day period. This averages out to (0.012 – 0.02)kWh/day of energy required to run the vacuum pump. Please note that this test is from one operations flywheel unit, each unit varies in its vacuum characteristics. We are continuing vacuum testing to reduce and optimise operation even further.
