Flexible floating reservoir for storing and transporting liquids heavier than the environmental liquid in which the reservoir is immersible

A flexible floating reservoir for storing and/or transporting a stored liquid in an external environmental liquid, the external environmental liquid having a density ρe and being in contact with environmental air through an external environmental liquid surface, the flexible floating reservoir being immersible in said external environmental liquid and comprising at least one enclosure configured to contain at least one inner layer of the stored liquid and comprising:

• at least one lower pliable membrane configured to separate the at least one inner layer from the external environmental liquid;
• at least one upper pliable membrane configured to separate the at least one inner layer from the environmental air;
• wherein a vertical direction is defined from the at least one lower pliable membrane to the at least one upper pliable membrane, and a horizontal plane is defined as a plane perpendicular to said vertical direction, the vertical direction and horizontal plane substantially coinciding, in use and with the external environmental liquid at rest, with a direction inverse to the gravitational force and the plane of the external environmental liquid surface, respectively;
• wherein the at least one enclosure is configured to contain the stored liquid that has a density ρs such that ρe<ρs,
• the flexible floating reservoir further comprising:
• perimeter connection means between respective perimeters of said at least one lower pliable membrane and the at least one upper pliable membrane;
• barrier means extending in said vertical direction and configured to keep, in use and with the external environmental liquid at rest, a volume of the environmental air comprised within the barrier means, the at least one upper pliable membrane and the horizontal plane, the barrier means being dimensioned so that the flexible floating reservoir is at hydrostatic equilibrium in the external environmental liquid at rest;
• lateral stabilization means configured to substantially balance out, in use and with the external environmental liquid at rest, a hydrostatic pressure of the external environmental liquid and a hydrostatic pressure inside the at least one enclosure along any direction on a plane parallel to said horizontal plane;
• and
• a plurality of tensioning means constituted by either:
• a plurality of tensioning elements with a lower end and an upper end fixed within the at least one enclosure to the at least one lower pliable membrane and the at least one upper pliable membrane, respectively;
• or
• a plurality of weldings joining the at least one lower pliable membrane with the at least one upper pliable membrane, along pre-determined corresponding segments of the at least one lower and the at least one upper pliable membranes;
• the plurality of tensioning means being configured to substantially transfer, in use, movements along the vertical direction between the at least one lower pliable membrane and the at least one upper pliable membrane in conjunction with further means selected from the group comprising enclosure pressurization means, a mooring system, and a tubular structure connected to the flexible floating reservoir around the perimeter connection means;
• and
• wherein the plurality of tensioning means is distributed throughout the at least one enclosure with a maximum reciprocal distance perpendicular to the vertical direction, that is, in use and with the external environmental liquid at rest, smaller than a minimum half-wavelength of a perturbation that amplifies instabilities on the at least one lower pliable membrane as defined by Rayleigh-Taylor instability theory.

A method for operating a flexible floating reservoir, the method comprising:

• providing a flexible floating reservoir for storing and/or transporting a stored liquid in an external environmental liquid, the external environmental liquid having a density ρe and being in contact with environmental air through an external environmental liquid surface, the flexible floating reservoir being immersible in said external environmental liquid and comprising at least one enclosure configured to contain an inner upper layer of external environmental liquid on top of an inner lower layer of the stored liquid along a vertical direction, and comprising:
• at least one lower pliable membrane configured to separate the inner lower layer from the external environmental liquid;
• at least one upper pliable membrane configured to separate the inner upper layer from the environmental air;
• wherein a vertical direction is defined from the at least one lower pliable membrane to the at least one upper pliable membrane, and a horizontal plane is defined as a plane perpendicular to said vertical direction, the vertical direction and horizontal plane substantially coinciding, in use and with the external environmental liquid at rest, with a direction inverse to the gravitational force and the external environmental liquid surface, respectively;
• wherein the at least one enclosure is configured to contain the stored liquid that has a density ρs such that ρe<ρs<2ρe,
• the flexible floating reservoir further comprising:
• perimeter connection means between respective perimeters of said at least one lower pliable membrane and the at least one upper pliable membrane;
• barrier means extending in said vertical direction and configured to keep, in use and with the external environmental liquid at rest, a volume of the environmental air comprised within the barrier means, the at least one upper pliable membrane and the horizontal plane, the barrier means being dimensioned so that the flexible floating reservoir is at hydrostatic equilibrium in the external environmental liquid at rest;
• enclosure pressurization means comprising liquid connection means between the inner upper layer and the external environmental liquid which are configured such that, at a given elevation along said vertical direction, a hydrostatic pressure of the inner upper layer substantially equals a hydrostatic pressure of the external environmental liquid;
• and
• a plurality of tensioning means constituted by either:
• a plurality of tensioning elements with a lower end and an upper end fixed within the at least one enclosure to the at least one lower pliable membrane and the at least one upper pliable membrane, respectively;
• or
• a plurality of weldings joining the at least one lower pliable membrane with the at least one upper pliable membrane, along pre-determined corresponding segments of the at least one lower and the at least one upper pliable membranes;
• the plurality of tensioning means being configured to substantially transfer, in use, movements along the vertical direction between the at least one lower pliable membrane and the at least one upper pliable membrane in conjunction with operation of the enclosure pressurization means;
• and
• wherein the plurality of tensioning means is distributed throughout the at least one enclosure with a maximum reciprocal distance perpendicular to the vertical direction, that is, in use and with the external environmental liquid at rest, smaller than a minimum half-wavelength of a perturbation that amplifies instabilities on the lower pliable membrane as defined by Rayleigh-Taylor instability theory;
• immersing the flexible floating reservoir into the external environmental liquid;
• filling the at least one enclosure at least partially with the stored liquid and additionally with external environmental liquid in the inner upper layer;
• and
• regulating internal pressure Pint of the at least one enclosure by the enclosure pressurization means.

A method for operating a flexible floating reservoir, the method comprising:

• providing a flexible floating reservoir for storing and/or transporting a stored liquid in an external environmental liquid, the external environmental liquid having a density ρe and being in contact with environmental air through an external environmental liquid surface, the flexible floating reservoir being immersible in said external environmental liquid and comprising at least one enclosure configured to contain at least one inner layer of the stored liquid and comprising:
• at least one lower pliable membrane configured to separate the at least one inner layer from the external environmental liquid;
• at least one upper pliable membrane configured to separate the at least one inner layer from the environmental air;
• wherein a vertical direction is defined from the at least one lower pliable membrane to the at least one upper pliable membrane, and a horizontal plane is defined as a plane perpendicular to said vertical direction, the vertical direction and horizontal plane substantially coinciding, in use and with the external environmental liquid at rest, with a direction inverse to the gravitational force and the plane of the external environmental liquid surface, respectively;
• wherein the at least one enclosure is configured to contain the stored liquid that has a density ρs such that ρe<ρs,
• the flexible floating reservoir further comprising:
• perimeter connection means between respective perimeters of said at least one lower pliable membrane and the at least one upper pliable membrane;
• barrier means extending in said vertical direction and configured to keep, in use and with the external environmental liquid at rest, a volume of the environmental air comprised within the barrier means, the at least one upper pliable membrane and the horizontal plane, the barrier means being dimensioned so that the flexible floating reservoir is at hydrostatic equilibrium in the external environmental liquid at rest;
• lateral stabilization means configured to substantially balance out, in use and with the external environmental liquid at rest, a hydrostatic pressure of the external environmental liquid and a hydrostatic pressure inside the at least one enclosure along any direction on a plane parallel to said horizontal plane;
• and
• a plurality of tensioning means constituted by either:
• a plurality of tensioning elements with a lower end and an upper end fixed within the at least one enclosure to the at least one lower pliable membrane and the at least one upper pliable membrane, respectively;
• or
• a plurality of weldings joining the at least one lower pliable membrane with the at least one upper pliable membrane, along pre-determined corresponding segments of the at least one lower and the at least one upper pliable membranes;
• the plurality of tensioning means being configured to substantially transfer, in use, movements along the vertical direction between the at least one lower pliable membrane and the at least one upper pliable membrane in conjunction with further means selected from the group consisting of enclosure pressurization means, a mooring system, and a tubular structure connected to the flexible floating reservoir around the perimeter connection means;
• and
• wherein the plurality of tensioning means is distributed throughout the at least one enclosure with a maximum reciprocal distance perpendicular to the vertical direction, that is, in use and with the external environmental liquid at rest, smaller than a minimum half-wavelength of a perturbation that amplifies instabilities on the at least one lower pliable membrane as defined by Rayleigh-Taylor instability theory;
• immersing the flexible floating reservoir into the external environmental liquid;
• filling the at least one enclosure at least partially with the stored liquid;
• and
• regulating internal pressure Pint of the at least one enclosure by the lateral stabilization means.