Methods and means for storing energy

Claim 2

A plant including means for storing energy and subsequently releasing said energy when required, said means comprising: refrigeration means, responsive to said energy, for refrigerating gas and liquefying said gas at substantially below atmospheric temperature; storage means for storing said liquefied gas at substantially below atmospheric temperature; a closed cycle heat engine having an upper temperature end and a lower temperature end; means for utilising said liquefied gas to maintain said lower temperature end at substantially below atmospheric temperature and means for maintaining said upper temperature end at not significantly below atmospheric temperature, thereby driving said heat engine and yielding mechanical energy, said engine including a working fluid independent of said liquefied gas.

Claim 3

The plant in claim 1 wherein said stored liquefied gas comprises nitrogen and oxygen in any proportions and is used to maintain said lower temperature end of said closed cycle heat engine at below -118° C.

Claim 4

The plant in claim 1 wherein means are provided to maintain said upper temperature end of said closed cycle heat engine at substantially atmospheric temperature.

Claim 5

The plant in claim 1 wherein said means for maintaining said upper temperature end of said closed cycle heat engine at not significantly below atmospheric temperature includes means for supplying waste heat available at said plant at above atmospheric temperature to said upper temperature end of said engine.

Claim 6

The plant in claim 1 wherein said closed cycle heat engine is a Stirling engine.

Claim 7

The plant in claim 1 wherein said closed cycle heat engine is designed so that its operation transfers heat from its lower temperature end to said liquefied gas at a temperature only slightly above that of the liquefied gas, thereby yielding a maximum of mechanical energy per unit quantity of liquefied gas supplied to said lower temperature end.

Claim 8

The plant in claim 1 wherein there is further provided: means for collecting gas vaporised during operation of said closed cycle heat engine from said liquefied gas utilised to maintain said lower temperature end of said engine at substantially below atmospheric temperature; a small number of additional auxiliary open cycle heat engines, such number being at least one; means for passing said collected vaporised gas through each of said open cycle heat engines sequentially; means for raising the temperature of said collected vaporised gas, thereby raising its pressure, before entering each said open cycle heat engine, thereby driving each said open cycle engine and yielding mechanical energy.

Claim 9

The plant in claim 7 wherein said means for raising the temperture of said collected vaporised gas before entering each said open cycle heat engine includes use of an additional auxiliary closed cycle heat engine with upper temperature end and lower temperature end and working fluid independent of said gas, each said auxiliary closed cycle engine being supplied at its upper temperature end with heat at a temperature not below atmospheric, including any waste heat available at said plant and not otherwise used therein, and designed so that its operation transfers heat from its lower temperature end to said gas at a temperature only slightly above the temerature at which said gas enters said open cycle engine.

Claim 10

The plant in claim 1 wherein there is further provided an additional prime mover for driving a dynamo for the production of electrical power.

Claim 11

A plant for producing electrical power, including: prime mover means for driving a dynamo for the production of electrical power; refrigeration means for producing liquid nitrogen and liquid oxygen gases from the atmosphere at temperatures substantially below atmospheric; storage means for storing said liquid gases; an additional Stirling heat engine of closed cycle form, employing a working fluid independent of said liquid gases, having an upper temperature end and a lower temperature end; means for transferring said liquid gases to said lower temperature end of said Stirling engine, thereby maintaining said end at a temperature below -118° C.; means for supplying heat to said upper temperature end of said Stirling engine at above atmospheric temperature from any suitable waste heat available at said plant and not otherwise used therein, thereby driving said Stirling engine and yielding mechanical power for driving a dynamo to produce electricity; means for collecting gas vaporised from said liquefied gases at said lower temperature end during operation of said Stirling engine; means for heating said collected gas, thereby raising its pressure; at least one additional auxiliary open cycle heat engine; means for using said pressurized collected vaporised gas to drive said open cycle engine to yield mechanical energy.

Claim 12

A plant for producing electrical power, including: prime mover means for driving a dynamo for the production of electrical power; refrigeration means for producing liquid nitrogen and liquid oxygen gases from the atmosphere at temperatures substantially below atmospheric; storage means for storing said liquid gases; an additional Stirling heat engine of closed cycle form, employing a working fluid independent of said liquid gases, having an upper temperature end and a lower temperature end; means for transferring said liquid gases to said lower temperature end of said Stirling engine, thereby maintaining said end at a temperature below -118° C.; means for supplying heat to said upper temperature end of said Stirling engine at above atmospheric temperature from any suitable waste heat available at said plant and not otherwise used therein, thereby driving said Stirling engine and yielding mechanical power for driving a dynamo to produce electricity; means for collecting gas vaporised from said liquefied gases at said lower temperature end during operation of said Stirling engine; means for heating said collected gas, thereby raising its pressure; at least one additional auxiliary open cycle heat engine; means for using said pressurized collected vaporised gas to drive said open cycle engine to yield mechanical energy.