The impact of optical and thermal properties on the performance of flat plate solar collectors
The impact of optical and thermal properties on the performance of flat plate solar collectors
- Renewable Energy, 28, p.331-344, 2003 .
The impact of the optical properties on the annual performance of flat plate collectors in a Swedish climate has been estimated with the MINSUN program. The collector parameters were determined with a theoretically based calculation program verified from laboratory measurements. The importance of changes in solar absorptance and thermal emittance of the absorber, the addition of a teflon film or a teflon honeycomb, antireflection treatment of the cover glazing and combinations of these improvements were investigated. The results show that several improvements can be achieved for solar thermal absorbers. A combined increase in absorptance from 0.95 to 0.97 and a decrease in emittance from 0.10 to 0.05 increase the annual performance with 6.7percent at 50 ¢XC operating temperature. The increase in performance by installing a teflon film as second glazing was estimated to 5.6percent at 50 ¢XC. If instead a teflon honeycomb is installed, a twice as high performance increase is obtained, 12.1percent. Antireflection treatment of the cover glazing increases the annual output with 6.5percent at 50 ¢XC. A combination of absorber improvements together with a teflon honeycomb and an antireflection treated glazing results in a total increase of 24.6percent at 50 ¢XC. Including external booster reflectors increases the expected annual output at 50 ¢XC to 19.9¡V29.4percent depending on reflector material. ÆÉ 2002 Elsevier Science Ltd. All rights reserved
SOLAR THERMAL COLLECTOR
MATERIALS
TEFLON
ANTIREFLECTION TREATMENT
SOLAR ABSORBER
BOOSTER REFLECTOR
The impact of the optical properties on the annual performance of flat plate collectors in a Swedish climate has been estimated with the MINSUN program. The collector parameters were determined with a theoretically based calculation program verified from laboratory measurements. The importance of changes in solar absorptance and thermal emittance of the absorber, the addition of a teflon film or a teflon honeycomb, antireflection treatment of the cover glazing and combinations of these improvements were investigated. The results show that several improvements can be achieved for solar thermal absorbers. A combined increase in absorptance from 0.95 to 0.97 and a decrease in emittance from 0.10 to 0.05 increase the annual performance with 6.7percent at 50 ¢XC operating temperature. The increase in performance by installing a teflon film as second glazing was estimated to 5.6percent at 50 ¢XC. If instead a teflon honeycomb is installed, a twice as high performance increase is obtained, 12.1percent. Antireflection treatment of the cover glazing increases the annual output with 6.5percent at 50 ¢XC. A combination of absorber improvements together with a teflon honeycomb and an antireflection treated glazing results in a total increase of 24.6percent at 50 ¢XC. Including external booster reflectors increases the expected annual output at 50 ¢XC to 19.9¡V29.4percent depending on reflector material. ÆÉ 2002 Elsevier Science Ltd. All rights reserved
SOLAR THERMAL COLLECTOR
MATERIALS
TEFLON
ANTIREFLECTION TREATMENT
SOLAR ABSORBER
BOOSTER REFLECTOR