Optimum storage of heat with a solar house

This paper reports calculations of the economic feasibility of solar house heating (and cooling) for different localities in the United States, and presents results in terms of maximum cost per square foot of solar collector which can be afforded if the solar system is to be competitive. Sunny mountainous regions, with cold winters (large fuel bills to be saved) are the most favorable areas.

Particular attention is given to the efficiency and capacity of energy storage and to the possibilities of saving summer heat for winter use. It is found that long-term storage is less economical than short-term storage. Storage costs of about a dollar per therm (10⁵ Btu), or solar collectors built and installed for $1.50 per sq ft, would make solar houses commercially competitive.