The pdf below provides detailed information from Alan Rushforth of Rushforth Solar on building large cylindrical water tanks for storing heat. These tanks are commonly used to store heat generated by an array of solar collectors in space and water heating applications.
The tanks that Alan makes typically range from a thousand gallons up 4000+ gallons, but the design could certainly be used for smaller tanks that would be typical of residential solar applications.
This design is very structurally efficient, light weight, and material efficient.
Alan also includes some very helpful material on building heat exchangers for these large tanks.
Thanks very much to Alan for providing this material!
The tanks structural shell is basically a large sheet metal panel that is wrapped into a cylinder with the ends lap spliced with bolts. Inside this cylindrical shell, layers of insulation are installed, and then an EPDM liner is installed.
Its a very structurally efficient design in that all the water pressure loads are reacted in simple hoop tension in the tank wall -- there are no bending loads in the tank wall as there are with flat sided tanks. The tanks are vented to the atmosphere, so the only loads in the tank wall are due to the water pressure.
Layers of polyisocyanurate insulation are installed inside the metal outer wall, and then a layer of EPDM is fitted inside the insulation as a waterproof liner. These tanks are good for water temperatures up to about 170F with a long life.
Alan also provides information on several alternatives for heat exchangers that work well with these tanks.
All the details on Alan's tank building method here.... (PDF)
January 5, 2013