A modular subsea fluid storage unit comprises a variable-volume inner tank having a rigid top panel and a peripheral wall that is flexible by virtue of concertina formations. The peripheral wall is extensible and retractable vertically while the horizontal width of the tank remains substantially unchanged. A side wall of a lower housing part surrounds and is spaced horizontally from the peripheral wall of the inner tank to define a floodable gap between the peripheral wall and the side wall that surrounds the tank. An upper housing part extends over and is vertically spaced from the top panel of the inner tank and overlaps the side wall to enclose the inner tank. The floodable gap and the upper housing part enhance thermal insulation and trap any fluids that may leak from the inner tank.

A modular subsea fluid storage unit has a variable-volume inner tank having a rigid top panel and a peripheral wall that is flexible by virtue of concertina formation. The peripheral wall is extensible and retractable vertically while the horizontal width of the tank remains substantially unchanged. A side wall of a lower housing part surrounds and is spaced horizontally from the peripheral wall of the inner tank to define a floodable gap between the peripheral wall and the side wall that surrounds the tank. An upper housing part extends over and is vertically spaced from the top panel of the inner tank and overlaps the side wall to enclose the inner tank. The floodable gap and the upper housing part enhance thermal insulation and trap any fluids that may leak from the inner tank.

A modular subsea fluid storage unit has a variable-volume inner tank having a rigid top panel and a peripheral wall that is flexible by virtue of concertina formations. The peripheral wall is extensible and retractable vertically while the horizontal width of the tank remains substantially unchanged. A side wall of a lower housing part surrounds and is spaced horizontally from the peripheral wall of the inner tank to define a floodable gap between the peripheral wall and the side wall that surrounds the tank. An upper housing part extends over and is vertically spaced from the top panel of the inner tank and overlaps the side wall to enclose the inner tank. The floodable gap and the upper housing part enhance thermal insulation and trap any fluids that may leak from the inner tank.

A modular subsea fluid storage unit comprises a variable-volume inner tank having a rigid top panel and a peripheral wall that is flexible by virtue of concertina formations. The peripheral wall is extensible and retractable vertically while the horizontal width of the tank remains substantially unchanged. A side wall of a lower housing part surrounds and is spaced horizontally from the peripheral wall of the inner tank to define a floodable gap between the peripheral wall and the side wall that surrounds the tank. An upper housing part extends over and is vertically spaced from the top panel of the inner tank and overlaps the side wall to enclose the inner tank. The floodable gap and the upper housing part enhance thermal insulation and trap any fluids that may leak from the inner tank.

In one aspect, a variable volume vessel includes an expandable/contractable bellows along with one or more components and/or features that prevent over-travel of the bellows and/or that prevent binding of the bellow relative to an outer housing of the vessel.

An enhanced apparatus system and method may be used to facilitate the construction of a processing tank such as an anaerobic digester. The kit may include a cover assembly that can be assembled to form a cover for the processing tank, a side wall assembly that can be assembled to form a side wall for the processing tank, and a plurality of ballast support assemblies. Each ballast support assembly may have a retracted configuration in which the ballast support assembly avoids significantly impeding vertical motion of the ballast block from an initial ballast location to a final ballast location, and a deployed configuration in which the ballast block can be supported by the ballast support assembly in the final ballast location.

An enhanced apparatus system and method may be used to facilitate the construction of a processing tank such as an anaerobic digester. The kit may include a cover assembly that can be assembled to form a cover for the processing tank, a side wall assembly that can be assembled to form a side wall for the processing tank, and a plurality of ballast support assemblies. Each ballast support assembly may have a retracted configuration in which the ballast support assembly avoids significantly impeding vertical motion of the ballast block from an initial ballast location to a final ballast location, and a deployed configuration in which the ballast block can be supported by the ballast support assembly in the final ballast location.

Systems and techniques for compressed air energy storage and regeneration thereof are described herein. A compressor for compressed air energy storage and regeneration thereof can include a housing, a actuator, and a heat exchanger. The housing can define a volume. The actuator can be operable to expand the volume and compress the volume. The heat exchanger can be located at least partially within the housing. The heat exchanger can be configured to compress when the actuator compresses the volume, expand when the actuator expands the volume, and transfer heat with a working fluid.

Systems and techniques for compressed air energy storage and regeneration thereof are described herein. A compressor for compressed air energy storage and regeneration thereof can include a housing, a actuator, and a heat exchanger. The housing can define a volume. The actuator can be operable to expand the volume and compress the volume. The heat exchanger can be located at least partially within the housing. The heat exchanger can be configured to compress when the actuator compresses the volume, expand when the actuator expands the volume, and transfer heat with a working fluid.