Innovative overheating solution for solar thermal collector using a reflective surface included in the air gap

Abstract

In this work, a new solution to prevent the overheating of solar collectors in the case of stagnation is presented. The solution proposed consists of inserting a reflective sheet inside the solar collector between the absorber and the glass cover to reduce the incoming energy by reflecting solar radiation. This protection is switched ON or OFF according to the absorber temperature. A prototype has been manufactured and tested in outside conditions and in laboratory. The prototype was tested with different percentages of protection. With 50% of protection, the overheating problem is eliminated. A simplified numerical model of the solar collector with the protection was developed and has been validated. The calculated temperature values are very close to the measured data. The experimental and numerical results showed the good behaviour of the proposed solution.