Increasing the rotational speed of the flywheel, for example, increases stored energy, but may also dramatically increase the stress on the flywheel, requiring the use of stronger and more expensive material for the rotor. Similarly, a heavier or larger diameter wheel will increase energy storage, but perhaps with an unacceptable tradeoff in system size or transportation and installation costs. Active Power’s CleanSource flywheels balance weight, size, speed, stress, and material strength to support a stored energy and cost profile optimized for our target markets in mission critical applications.