Optimum configuration of compound parabolic concentrator (CPC) solar water heater types for dwellings situated in the northern maritime climate

For northern maritime climates with a high diffuse component of solar radiation, non-imaging CPC solar collectors with concentration ratios of up to 2 can be used to concentrate direct as well as diffuse incident solar radiation without tracking. Due to the concentrated solar flux incident on the absorber these systems can produce temperatures in the excess of those produced by conventional solar water heaters thus reducing the auxiliary energy demand. Additionally a smaller absorber area is required reducing the cost of the solar collector making these systems more economically attractive. Two CPC solar collectors with an identical cavity profile were fabricated in house, the only discernable difference between these was that one utilised a heat-pipe absorber whereas the other used a simple direct flow absorber. These were both tested under steady state operating conditions at inlet temperatures of 20°C, 30°C 40°C and 50°C to simulate the conditions experienced by a typical domestic solar water heater. It was found that the direct flow CPC performed better at higher solar intensities and lower inlet temperatures as the heat-pipe CPC had a much higher absorber plate temperature. Thus for domestic applications simple direct flow CPC systems would be preferred due to their higher efficiency and lower cost.