Lightweight, safe hydraulic power system and a method of operation thereof

A hydraulic accumulator system for alternately storing energy in the form of gas pressure and converting the stored energy into work by gas expansion, said hydraulic accumulator system comprising:

• a high-pressure reversible fluid drive unit operable in a motor mode to produce work and operable in a pump mode;
• gas pressure storage means including at least one gas vessel;
• a bank of high-pressure liquid vessels connected in parallel between and providing fluid communication between said high pressure reversible fluid drive unit and said gas pressure storage means;
• a low-pressure, reversible fluid drive unit operable in either a motor mode or a pump mode, said low-pressure reversible fluid drive unit having a peak efficiency at a discharge pressure head substantially below the discharge pressure head for peak efficiency of said high-pressure reversible fluid drive unit;
• a bank of low-pressure liquid vessels connected in parallel between and providing fluid communication between said low pressure reversible fluid drive unit and said gas pressure storage means;
• and
• a liquid reservoir for receiving fluid from said high-pressure bank through said high pressure fluid drive unit operating in the motor mode, for receiving fluid from said low-pressure bank through said low-pressure fluid drive unit operating in motor mode, for supplying fluid to said high pressure bank through said high pressure fluid drive unit operating in the pump mode and for supplying fluid to said low pressure bank through said low pressure fluid drive unit operating in the pump mode.