Non-circular pressure vessel

A reservoir assembly comprising:

• a first pressure vessel surrounding a first volume and having a constant cross-section along a first length between two first ends, wherein the constant cross-section defines a closed shape;
• and
• a second pressure vessel adjacent to the first pressure vessel and enclosing a second volume outside of the first volume, the second pressure vessel having a constant cross-section defining a closed shape and extending along a second length that extends parallel to the first length,
• wherein the first pressure vessel is larger than the second pressure vessel,
• wherein the first volume and the second volume are independent with neither of the first pressure vessel or the second pressure vessel surrounding any part of the other one of the first pressure vessel and the second pressure vessel,
• wherein the second pressure vessel is attached to the first pressure vessel by a bracket disposed therebetween, wherein the first pressure vessel, the second pressure vessel, and the bracket together define a constant cross-section of the reservoir assembly extending entirely the first length between the two first ends and having an irregular shape configured to fit within a corresponding irregularly-shaped space having a first region with a first width and holding the first pressure vessel, and a second region with a second width that is smaller than the first width of the first region and which holds the second pressure vessel, and
• wherein the first pressure vessel is wider than the second width of the second region.