TIM-PCM EXTERNAL WALL SYSTEM FOR SOLAR SPACE HEATING AND DAYLIGHTING

An external wall system for solar space heating and daylighting compos ed of transparent insulation material (TIM) and translucent phase chan ge material (PCM) is presented. This system enables selective optical transmittance of solar radiation. Visible light is mainly transmitted and invisible radiation is mainly absorbed and converted to heat, caus ing in particular phase change. The storage medium is also the absorbe r. The concept of the system is presented in detail together with the investigations carried out, including a brief outline of modeling, opt ical experiments on PCR? samples and long-term experiments on a protot ype wall as well as numerical simulations. The results indicate a prom ising thermal-optical behavior of the system. For instance in a Swiss lowland climate (Zurich-airport) a mean energy dux of 13 W m(-2) (syst em efficiency 0.27) was calculated through a south facing TIM-PCM wall into the building during the month with the lowest irradiation (Decem ber). The parameters of the prototype wall with a mean melting tempera ture of the PCM of 26.5 degrees C were assumed. When considering the p ercentage of time in which the building does not lose energy through t he south facing TIM-PCM wall, a maximum can be reached with a mean mel ting temperature of approximately 20 to 21 degrees C. In this case ene rgy losses through the facade occur only during 1% of the time. With r egard to the practical application of the system in buildings, aspects of reliability and durability have to be further investigated. (C) 19 97 Published by Elsevier Science Ltd.