The motor-generator will be used to pull a load up a mountain side/steep incline on a rail system, the load is between 10 and 300 tonnes, its for a gravitational potential energy storage system. Excess electricity pulls the load up the incline, when there is demand for electricity the load is released driving the generator. Obviously a good gearing system is required. Is this technically possible? How much do you estimate one would cost? What would be the device's efficiency?