Development and improvement of self-pumping boiling collector solar hot water storage system, June 1987--May 1988, in Colorado State University Solar House 3

Abstract

The results of an experimental study of a pilot scale passive solar hot water heating system utilizing a boiling collector are presented. This work was supported by the US Department of Energy under grant No. FG03-86SF16306. The self-pumping system was designed and built in 1986. Heating season performance of the initial system during the winter of 1986-87 confirmed the viability of the design concept. This report details the continued experimental study of an improved self-pumping system during the period from June 1987 through May 1988. The system alternates between two modes of operation. During the run cycle, vapor pressure drives the evaporated refrigerant downward from the collector to the condenser. Once a preset quantity of refrigerant is condensed, vapor pressure is again used to force the return of the condensate to the collector during the pump cycle. The pilot system is optionally configured to operate with a mechanical pump. Daily operating characteristics and seasonal performance are discussed. The loss in thermal efficiency due to the use of vapor pressure to return liquid refrigerant to the collector is assessed by comparing self-pumping and mechanical-pumping operation. Daily thermal efficiency of the self-pumping system is relatively low as compared to fully developed commercialmore » domestic solar hot water systems; however, mid-day cycle efficiencies are 40 to 50 percent. It is anticipated that daily efficiencies may be improved to the point that the self-pumping system will be an attractive alternative to more conventional sensible heat systems. Performance of the self-pumping system is strongly influenced by transient thermal losses. Refinement of the system design, including individual components, is required to reduce losses and improve performance. 21 refs., 27 figs., 2 tabs.« less