PV and solar collector arrays are often modular so why not design a heat storage system that's also modular? Modular designs are easy to assemble, versitile and easy to troubleshoot and modular plastic drum heat storage systems have the additional advantage of providing a unique metod of heat stratification that improves solar heat collection performance.
Integral PermaCulture Curriculum > 4. Energy & EcoTech > 9. & 10. EcoTechnology > a) Heating >