CPC-lightweight construction collector

Status

finished

Summary

Motivation:

The latest solar thermal collectors consists of metal casings, mineral wool for insulation, piping and absorber made of copper and transparent covers made of glass.

This construction causes high weight and high energy consumption in the production chain. The high weight of the modules leads to increased costs for production, transport and assembling.

A reduction in weight (as well as an improvement of the ecological balance) could be achieved by manufacturing the collector casing of new materials such as plastics or plants that grow again. The same goal is reachable if the reflector and the casing of the CPC collector are put together to one part. Doing this we reduce the amount of needed material and we save production costs, because the number of production steps is reduced. Absorber material savings up to 50 percent can be achieved if one use absorber that are coated on both surfaces instead of only one side.

Also the accuracy of the reflectors geometry can be increased significantly, compared to the current situation. This leads to a better optical efficiency and thus to a better performance of the collector (higher temperatures and higher energy output during one whole year). So we can think of using the CPC - collector in the sector of process heating and it can compete with the more expensive vacuum tube collectors.

The aims of the project CPC-Leichtbaukollektor are to rise the performance of the product, to reduce the weight and to use new, "ecological cleaner" materials.

Results

One collector that is optimised in its optical properties was developed, built and measured. The casing of the collector was still made of aluminium. For holding the reflectors at the right geometry, insulation material was milled to this geometry. This insulation material supports the reflectors.

Collector casings out of different plastic materials was deepdrawed. Polycarbonate was the thermoplastic material with the best results in matter of heat-resistance. An other material that is very interesting in economical and technical aspects is glass-fibre reinforced plastic (GRP).

Using a testing collector there was made tests with a compound plate material (Polycarbonate - Aluminium - Polyethylene - Compound). As a result we saw that Polyethylene do not withstand the temperature inside the collector.

An absorber - register with double coated absorber sheet material was produced and measured in the test collector. The results in terms of energy - output are satisfying, but the long term stability of the welded connection between the aluminium-absorber and the copper-tube may be a critical point.

The transmission of the new solar glass (3 mm in thickness) was measured. It is lower than that of the 4 mm thick glass.

Contact

Johann Kalkgruber
Kalkgruber Solar- und Umwelttechnik GmbH
Werkstraße 1
A 4451 St. Ulrich / Steyr
Tel.: +43 7252 50002 0
Fax: +43 7252 50002 10
E-Mail: kalkgruber@kalkgruber.at