Innovative Fixed Mirror Solar Concentrator for Process Heat
V. Martinez1*, R. Pujol1 and A. Moia1
1 UIB, Phisics Department, Campus UIB, Ctra de Valldemossa km 7.5, 1070122 Palma de Mallorca, Spain
* Corresponding Author, victor. martinez@uib. es
Abstract
The development of a solar thermal collector with fixed reflector and tracking absorber, specially designed for supplying process heat in industrial processes and solar cooling, is described. Initially the project was based on the Fixed Mirror Solar Concentrator (FSMC) concept already developed during the 70’s, but after a detailed optical analysis it was decided to use a similar concept based on parabolic mirrors. With this design a maximum theoretical annual averaged efficiency of about 39% could be reached. In order to reduce the number of the necessary mechanisms, the positioning system consists of a grid of 8 lines of receivers driven by 4 articulated arms. The reflector has been manufactured as a sandwich structure with a high reflectivity aluminium sheet as the reflecting surface. Each collector has a 4.5 x 6 m reflector that consists of 16 pieces of 1 x 1.5 m assembled together by means of 5 laser cut steel profiles. The receiver consists of 32 standard U-pipe Sydney collectors. The first prototype has started operation in July 2008 and the main problem detected has been the breaking of some of the evacuated tubes due to thermal stresses. At the moment a complete evaluation of the system is being carried out.
Keywords: Concentrating collector, process heat, medium temperature, stationary reflector
About 30% of the energy consumption in Europe is attributed to the industrial sector [1]. More than fifty percent of that energy spent corresponds to process heat applications at temperatures up to 250°C [2]. The scientific bases of the technology required to supply solar heat at such temperatures are well established. Nevertheless, this great potential does not result in wide-range use of solar thermal collector systems within the industry.
For low temperature range applications (up to 80°C), the main obstacle is probably the relatively long payback periods of the initial investment, typically longer than 10 years. However, other factors should also be taken into account: limited suitable surfaces available, the lack of experience in the installation and operation of large facilities or processes and machinery not adapted to incorporate solar energy.
In the mid temperature range (up to 250°C) one of the main obstacles to overcome, is the lack of a well developed market for solar collectors that are easily integrable into industrial buildings, competitively priced and which can reliably operate at temperatures above 100°C
To address these needs, a project was engaged to promote the development of a new collector specially designed for process heat applications at up to 160°C. On July 2008 the first prototype of this new development has started operation.
