Multi-sheet corrugated tank construction for passive solar heating

Abstract

A passive solar heating liquid storage tank is formed of multiple thin sheets of thermoplastic or thermoset material to provide a lightweight, inexpensive and high volume tank. The multiple sheets have a plurality of parallel undulations or corrugations transverse to their surfaces. The undulations form spacial wave trains of given amplitude and frequency so that when their peaks are secured together they form generally parallel circular tubes. One of the pair of sheets has a third sheet secured to its surface. The third also has undulations in its surface with spacial frequency at least as great as the frequency of the wave train of the pair of sheets. Peaks of the third sheet are then secured to exterior peaks of the pair of sheets. Such construction forms a tank having the strength of parallel cylindrical tubes but with total volume approaching that of tubes having a rectangular cross-section. In this way a lightweight tank with high volume and strength to resist structural beam flexure relative to the surfaces is formed. Such construction is particularly suitable for passive solar water heating installations at inaccessible locations over long periods of time, such as on the roof of a building.