Multimode solar-heating system--Columbia, South Carolina

Report describes failure of six-mode pyramidal-optics system to reduce winter energy savings. Over 12 month period, control problems, energy dissipation, and high operating-energy requirements undermined system efficiency. Energy savings were maximal when system in direct space-heating or hot-water preheating mode. In least efficient mode, heat pumps alternatively mingled storage or collector energy, and space heating was provided by electric heat strip.