Return analysis of commercial solar thermal devices

A procedure for assessing the techno-economic viability of solar thermal systems in a dynamic economic environment is developed. It is shown analytically that the period for replacement of these systems depends upon the nature of their use. While determining investment viability, it is necessary to ascertain the exact life of the system. The life of a solar thermal system for non-commercial use is determined by optimum life for replacement, which is not influenced by energy inflation and energy saved. It is a function of maintenance cost and decreases with increases with increase in maintenance cost. For commercial purposes, the lifetime of the system is governed by optimum return on investment mode (Ζ), which is a strong function of energy inflation and energy saved per unit capital cost. (author)