Experimental and numerical analysis of an efficiently optimized evacuated flat plate solar collector under medium temperature

Medium temperature solar thermal systems have a great prospect to be an efficient energy source for practical industrial applications. Although the evacuated flat solar collector is a potential non-concentrating collector for this application, current designs have not fully demonstrated its superiority. In this paper, a medium-scale (50.96 m(2)) solar thermal system based on an efficiently optimized evacuated flat plate solar collector structure is designed. A systematic four months long real-time experiment under the natural environment is conducted for medium solar thermal applications in a region with four distinct seasons. An annual performance analysis is then conducted in four different locations through a validated numerical model. Experimental results demonstrate that, when the inlet temperature is 123.0 degrees C, the ambient temperature is 35.7 degrees C and the solar irradiation is 835.2 W/m(2), the thermal efficiency and exergy efficiency can reach 59.67% and 14.35%, respectively. The efficiently optimized evacuated flat plate solar collector can also achieve a stable annual average thermal efficiency at the four studied locations with values reaching up to 50%. Therefore, the superiority of this efficiently optimized evacuated flat plate solar collector design over previous ones is demonstrated.