A system for emptying a gravity separated fluid including a flexible bag storing the fluid arranged within a protection structure, the protection structure including a bottom element forming the lower section of the protection structure, the flexible bag being connected to the protection structure, and includes at least one fluid conduit providing fluid communication between the flexible bag and outside the protection structure. A first outlet pipe is arranged inside the flexible bag near the bottom element and is connected to and in fluid communication with the at least one fluid conduit. A perforated tube surrounding the outlet pipe provides an annulus fluid passage, water is supplied to the structure volume, and the fluid is emptied through the at least one fluid conduit, through the perforations in the perforated tube, through the annulus fluid passage to the first outlet pipe.

A modular structure for being at least partly submerged in a body of water, is disclosed. The modular structure comprises structure elements and strengthening elements providing structural integrity and flexibility, and can typically be a closed structure like e.g. a tank structure. Further, macro structures comprising attached modular structures are presented. Finally, methods for construction of such structures are disclosed.

An underwater energy storage system includes a tank for storing a compressed gas that is adapted to be stored underwater. The tank includes at least one water opening through which water from surrounding environment can flow into and out of the tank, and at least one gas opening through which the compressed gas is received. The underwater energy storage system further includes at least one duct communicating between the at least one opening for gas flow and a source of compressed gas and a compartment constructed over a roof of the tank, wherein said compartment is adapted for receiving weights at a sinking site of the tank.

An underwater energy storage system includes a tank for storing a compressed gas that is adapted to be stored underwater. The tank includes at least one water opening through which water from surrounding environment can flow into and out of the tank, and at least one gas opening through which the compressed gas is received. The underwater energy storage system further includes at least one duct communicating between the at least one opening for gas flow and a source of compressed gas and a compartment constructed over a roof of the tank, wherein said compartment is adapted for receiving weights at a sinking site of the 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.

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 subsea fluid storage system comprising a soft bladder disposed within a pressure balanced reservoir, a rotatable piston, and a piston rotator which rotates and twists the rotatable piston as it travels along a predetermined axis within the pressure balanced reservoir, predictably and repeatabley collapses the soft bladder when the rotating piston cooperatively travels about the piston rotator, twisting the soft bladder as the rotating piston moves along the predetermined axis, collapsing the bladder inward and thereby emptying the bladder of fluid within the bladder. The piston's rotation pulls the soft bladder away from the pressure balanced reservoir's interior, thereby preventing the bladder's binding or pinching the pressure balanced reservoir's interior. In configurations, fluid is allowed to enter the pressure balanced reservoir via a valve until a balance is achieved between an interior and an exterior of the pressure balanced reservoir.

A subsea fluid storage system comprising a soft bladder disposed within a pressure balanced reservoir, a rotatable piston, and a piston rotator which rotates and twists the rotatable piston as it travels along a predetermined axis within the pressure balanced reservoir, predictably and repeatabley collapses the soft bladder when the rotating piston cooperatively travels about the piston rotator, twisting the soft bladder as the rotating piston moves along the predetermined axis, collapsing the bladder inward and thereby emptying the bladder of fluid within the bladder. The piston's rotation pulls the soft bladder away from the pressure balanced reservoir's interior, thereby preventing the bladder's binding or pinching the pressure balanced reservoir's interior. In configurations, fluid is allowed to enter the pressure balanced reservoir via a valve until a balance is achieved between an interior and an exterior of the pressure balanced reservoir.

A system for emptying a gravity separated crude oil including a flexible bag storing the crude oil arranged within a protection structure, the protection structure including a bottom element forming the lower section of the protection structure, the flexible bag being connected to a flange that is connected to the protection structure, and includes at least one fluid conduit providing fluid communication between the flexible bag and outside the protection structure. A first outlet pipe is arranged inside the flexible bag near the bottom element and is connected to and in fluid communication with the at least one fluid conduit. A perforated tube surrounding the outlet pipe provides an annulus fluid passage, water is supplied to the structure volume, and the crude oil is emptied through the at least one fluid conduit, through the perforations in the perforated tube, through the annulus fluid passage to the first outlet pipe.

A system for emptying a gravity separated crude oil including a flexible bag storing the crude oil arranged within a protection structure, the protection structure including a bottom element forming the lower section of the protection structure, the flexible bag being connected to a flange that is connected to the protection structure, and includes at least one fluid conduit providing fluid communication between the flexible bag and outside the protection structure. A first outlet pipe is arranged inside the flexible bag near the bottom element and is connected to and in fluid communication with the at least one fluid conduit. A perforated tube surrounding the outlet pipe provides an annulus fluid passage, water is supplied to the structure volume, and the crude oil is emptied through the at least one fluid conduit, through the perforations in the perforated tube, through the annulus fluid passage to the first outlet pipe.