Solar Cooling and Heating System
Solar radiation is the fundamental, basic, energy source for the earth. Solar thermal receivers with parabolic trough reflectors, focusing on surface treated pipe absorbers in evacuated glass tubing, can recover 60% of the incident solar radiation in the sensible heat of a fluid flowing in the pipe at a temperature up to 200°C. Currently available solar photovoltaic collectors recover 10 – 15 % of the incident solar radiation as electric power. Solar thermal heat can be used effectively in a two stage absorption chiller with a coefficient of performance of 1.2 to provide chilled water at 7°C for cooling a building in summer. This use is particularly effective since the need for building cooling is strongly correlated to the availability of solar radiation. Solar thermal heat can also be used directly in winter for building heating. This solar project component of IWESS explores the design, installation, and performance of solar thermal technology in supplying building cooling/heating/ventilation.
The IW solar thermal system, located in Pittsburgh, PA, consists primarily of 52 m2 of parabolic trough solar collectors and a 16 kW double effect absorption chiller driven by either hot fluid from solar receivers or natural gas fuel.
The system’s 4 parabolic trough solar collector, PTSC, modules are installed in two valleys of the IW saw tooth roof. Each row of two collectors has its own tracking mechanism, whose axis is orientated 15° east of true north. The collectors track the altitude of the sun as it travels from east to west during the day to ensure that the radiation from the sun is continuously focused on the linear receiver. A heat transfer fluid, HTF, an aqueous solution containing 50% propylene glycol, is heated in the receivers and circulated to the absorption chiller, where it is used to generate either chilled water or hot water for space cooling or heating. If the solar radiation is not adequate to provide required energy for the absorption chiller, the heat transfer fluid is by passed back to the collectors in solar collection loop to accumulate the energy. A natural gas burner is then used to drive the absorption chiller to provide cooling or heating for the IW.
The PTSCs on the roof of the IW