A. Millioud1* and J. Dreyer2

1 NEP Europe GmbH, Badenerstrasse 18, 8004 Zurich, Switzerland
2 NEP Solar Pty Ltd, Unit 21, 14 Jubilee Avenue, Warriewood, NSW 2102, Australia
* Corresponding Author, antoine. millioud@newenergvpartners. com

Abstract

A small aperture medium temperature solar parabolic collector system has been developed. Its primary application is to drive high temperature and high efficiency thermal refrigeration systems such as double stage chillers; a combination which is shown to achieve the best economic performance in solar cooling. The collector system makes use of composite reflector carriers. The carrier consists of an efficient sandwich structure of fibre-reinforced polymeric skins and a specialised core material, onto which an aluminium reflector is bonded. Multiple design iterations have lead to a structure which is form stable, accurate and cost effective. Finite element analysis and photogrammetric testing on the prototype were conducted to confirm the optical precision of the solution. A 50m2 aperture pilot solar field was installed and is currently undergoing thermal testing.

Keywords: Solar cooling, parabolic trough collector, polymer carrier, absorption chiller, composite materials, polymeric materials, reflector, concentrating solar collector

1. Introduction

Air-conditioning loads in cities around the Sun Belt regions of the earth are increasing leading to rising consumption of electricity with associated green house gas emissions and increased pressure at peak hours on congested municipal electricity distribution networks. The deployment of solar heat driven absorption chillers is an effective way to address these issues. In particular, double stage absorption chillers driven by parabolic trough solar collectors custom-designed for solar cooling applications, is a financially viable approach to solar cooling and in general to the substitution of grid electricity with solar energy. Solar cooling projects are thought to be most viable where they are integrated in large building air-conditioning systems and where they take the role of peaking chillers. Ideally such a system is implemented as part of an upgrade or new build. Solar thermal systems can easily be integrated into existing building thermal energy systems and can accommodate thermal storages. The integration solution has to be optimised such that the collected solar energy is fully utilised, if necessary through cascading (from high temperature requirements down to lower temperature requirements). The concentrating solar collection system has to be designed such that it can be installed on roofs of varying sizes and geometries. This flexibility is required at minimal additional costs. Furthermore concentration factors, absorber design and choice of materials must be selected in function of the desired output temperature of 150-200°C.