Efficiency Gain of a Solar Trough Collector Due to an IR-Reflective Film on the Non-Irradiated Part of the Receiver

Abstract

In order to reduce the thermal emission from a glass-covered receiver tube of a trough collector, the part of the glass not facing the collector can be covered with an IR-reflecting layer. The advantages of such a covering are discussed in this preliminary study by means of optical and thermal simulations of three configurations of a receiver (two configurations with two different IR-reflecting layers, and one configuration without any IR-reflecting layer). From the simulations, it was observed that one of the layers produce a relative gain of 3.84% of the efficiency over a year (location: south of Italy). An upper bound on the cost of the covering is given.

Keywords:

• IR-reflective covering
• Selective film
• Glass-covered receiver
• Trough collector
• Trough efficiency

Notes

¹However, it would not be appropriate to see this comparison as a metal film–semiconductor comparison, since each of the two groups (especially the semiconductors) can show a large variety of properties depending on the layer thickness and on the material: a thick layer of semiconductor, for example, can have IR reflectivity and solar transmission levels similar to those of metallic films.

²For this reason, the efficiency values found are higher than one could reasonably expect from a real plant. However, the relative gain due to the IR-reflecting cover should be the same.