Charles Gray, the EPA head of the hydraulic hybrid work (2006) with Parker Hannefin and the University of Michigan as well as Ford, stated that he could hold a 500 horsepower hydraulic motor in his hand.
Check US 7677208, my patent for a hydraulic in wheel drive as well as 10,000 other applications, including the ability to store electricity.
Here's a link
http://www.google.com/patents/US7677208
regards
mech