My boss wants to create a large, LARGE disc that spins in order to store energy. Like, an acre in size. It would do so in much the same way a flywheel would store energy. I've shown him that there are several small size flywheels that work on the same principal but at high revolutions. His argument is that the large size means that it wouldn't have to spin as fast. Think cement disc floating in water. I think it's folly. What are the pros and cons of such a system as my boss wants to create.