A pressure vessel assembly comprising: a plurality of lobes (25,30,35), each of the lobes (25,30,35) having at least one vertically arranged interior wall (45,50,55), the plurality of lobes (25,30,35) being positioned in a side by side arrangement such that a first interior wall of a first lobe is positioned adjacent a second interior wall of a second lobe, the first interior wall having a first wall top side and a first wall bottom side, the second interior wall having a second wall top side and a second wall bottom side, the first wall top side is joined to the second wall top side and the first wall bottom side is joined to the second wall bottom side; a first end wall surface and a second end wall surface of each of the plurality of lobes (25,30,35); and a plurality of end caps, each of the end caps joined to the end wall surfaces (22,24) of the lobes (25,30,35); wherein the first wall top side, the first wall bottom side, the second wall top side and the second wall bottom side each are aligned parallel to a horizontal plane of the pressure vessel assembly and are disposed adjacent a curved wall portion (40, 60, 65) of the lobes (25,30,35); wherein the plurality of lobes (25,30,35) are formed of at least one of high strength aluminum alloys, 4000 series steel, pH stainless steel, and high strength 400 series stainless steel; wherein adjacent lobes (25, 30, 35) are coupled with one or more bonds; and wherein a process for fabrication of these bonds includes at least one of fusion welding, solid state welding, linear friction welding, brazing, capacitive discharge welding, transient liquid phase bonding, and cold spraying; characterized in that each of the end caps is joined to at least one adjacent end cap; and each of the lobes comprises a shoulder region located at the first wall top side, the first wall bottom side, the second wall top side and the second wall bottom side, wherein the shoulder region comprises a shoulder wall thickness greater than a wall thickness of the remainder of the lobes (25,30,35). a plurality of lobes (25,30,35), each of the lobes (25,30,35) having at least one vertically arranged interior wall (45,50,55), the plurality of lobes (25,30,35) being positioned in a side by side arrangement such that a first interior wall of a first lobe is positioned adjacent a second interior wall of a second lobe, the first interior wall having a first wall top side and a first wall bottom side, the second interior wall having a second wall top side and a second wall bottom side, the first wall top side is joined to the second wall top side and the first wall bottom side is joined to the second wall bottom side; a first end wall surface and a second end wall surface of each of the plurality of lobes (25,30,35); and a plurality of end caps, each of the end caps joined to the end wall surfaces (22,24) of the lobes (25,30,35); wherein the first wall top side, the first wall bottom side, the second wall top side and the second wall bottom side each are aligned parallel to a horizontal plane of the pressure vessel assembly and are disposed adjacent a curved wall portion (40, 60, 65) of the lobes (25,30,35); wherein the plurality of lobes (25,30,35) are formed of at least one of high strength aluminum alloys, 4000 series steel, pH stainless steel, and high strength 400 series stainless steel; wherein adjacent lobes (25, 30, 35) are coupled with one or more bonds; and wherein a process for fabrication of these bonds includes at least one of fusion welding, solid state welding, linear friction welding, brazing, capacitive discharge welding, transient liquid phase bonding, and cold spraying; characterized in that each of the end caps is joined to at least one adjacent end cap; and each of the lobes comprises a shoulder region located at the first wall top side, the first wall bottom side, the second wall top side and the second wall bottom side, wherein the shoulder region comprises a shoulder wall thickness greater than a wall thickness of the remainder of the lobes (25,30,35).