Evacuated-Tube Heat-Pipe Solar Collectors Applied to the Recirculation Loop in a Federal Building: Preprint

This paper describes the design, simulation, construction, and initial performance of a solar water heating system (a 360-tube evacuated-tube heat-pipe solar collector, 54 m2 in gross area, 36 m2 in net absorber area) installed at the top of the hot water recirculation loop in the Social Security Administration's Mid-Atlantic Center in Philadelphia. When solar energy is available, water returning to the hot water storage tank is heated by the solar array. This new approach, in contrast to the more conventional approach of preheating incoming water, is made possible by the thermal diode effect of heat pipes and low heat loss from evacuated-tube solar collectors. The simplicity of this approach and its low installation costs support the deployment of solar energy in existing commercial buildings, especially where the roof is some distance away from the water heating system, which is often in the basement. Initial performance measurements of the system are reported.