A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

A carbon dioxide cycle power generation system includes storage collectively storing portions of carbon dioxide liquid and gas and a transfer connection selectively directing flow of the carbon dioxide through a turbine. The system cycles between different seawater depths in order to employ at least one of seawater pressure and seawater temperature in creating the carbon dioxide flow. Inlet/outlet control valves on variable volume tanks, positioned below movable pistons within the respective tank, selectively allow seawater into or out of a lower portion of the respective tank below the piston to pressurize the carbon dioxide therein relative to the carbon dioxide within the other tank when at depth rather than near the surface. Inhibited versus uninhibited heat transfer between storage portions and the seawater allows different seawater temperatures at depth and near the surface to create the carbon dioxide flow. Acoustic communications may be driven concurrent with the turbine.

A carbon dioxide cycle power generation system includes storage collectively storing portions of carbon dioxide liquid and gas and a transfer connection selectively directing flow of the carbon dioxide through a turbine. The system cycles between different seawater depths in order to employ at least one of seawater pressure and seawater temperature in creating the carbon dioxide flow. Inlet/outlet control valves on variable volume tanks, positioned below movable pistons within the respective tank, selectively allow seawater into or out of a lower portion of the respective tank below the piston to pressurize the carbon dioxide therein relative to the carbon dioxide within the other tank when at depth rather than near the surface. Inhibited versus uninhibited heat transfer between storage portions and the seawater allows different seawater temperatures at depth and near the surface to create the carbon dioxide flow. Acoustic communications may be driven concurrent with the turbine.

An apparatus includes multiple tanks each configured to receive and store a liquid refrigerant under pressure. The apparatus also includes one or more insulated water jackets each configured to receive and retain water around at least part of an associated one of the tanks. The apparatus further includes at least one generator configured to receive a flow of the liquid refrigerant and to generate electrical power based on the flow of the liquid refrigerant. The apparatus also includes one or more first valves configured to control the flow of the liquid refrigerant between the tanks and through the at least one generator. In addition, the apparatus includes one or more second valves configured to control a flow of the water into and out of the one or more insulated water jackets.

Techniques for subsurface thermal energy storage of heat generated by concentrating solar power enable smoothing of available energy with respect to daily and/or seasonal variation. Solar thermal collectors produce saturated steam that is injected into a producing or wholly/partially depleted oil reservoir that operates as a heat storage reservoir. Some of the saturated steam generated by the collectors is optionally used to generate electricity. Heat is withdrawn from the reservoir as saturated steam and is used to operate an active thermal recovery project (such as a producing thermally enhanced oil reservoir) and/or to generate electricity. Withdrawn heat is optionally augmented by heat produced by firing natural gas. The reservoir is optionally one that has been used for thermally enhanced oil recovery and thus is already warm, minimizing heat losses.

Techniques for subsurface thermal energy storage of heat generated by concentrating solar power enable smoothing of available energy with respect to daily and/or seasonal variation. Solar thermal collectors produce saturated steam that is injected into a producing or wholly/partially depleted oil reservoir that operates as a heat storage reservoir. Some of the saturated steam generated by the collectors is optionally used to generate electricity. Heat is withdrawn from the reservoir as saturated steam and is used to operate an active thermal recovery project (such as a producing thermally enhanced oil reservoir) and/or to generate electricity. Withdrawn heat is optionally augmented by heat produced by firing natural gas. The reservoir is optionally one that has been used for thermally enhanced oil recovery and thus is already warm, minimizing heat losses.

An apparatus includes first and second tanks each configured to receive and store a refrigerant under pressure. The apparatus also includes at least one generator configured to receive flows of the refrigerant between the tanks and to generate electrical power based on the flows of the refrigerant. The apparatus further includes first and second hydraulic drives associated with the first and second tanks, respectively. Each hydraulic drive includes a first piston within the associated tank, a channel fluidly coupled to the associated tank and configured to contain hydraulic fluid, and a second piston within the channel and configured to move within the channel in order to vary an amount of the hydraulic fluid within the associated tank and vary a position of the first piston within the associated tank. The channel of each hydraulic drive has a cross-sectional area that is less than a cross-sectional area of the associated tank.