Investigations of a Fresnel-lens solar collector

The Danish company Heliac has developed a concentrating solar collector based on a unique and inexpensive polymer film. The film features a microstructure surface of Fresnel-lenses, which is applied to the backside of a float glass. Each collector consists of eight lenses mounted on a two-axis solar tracker, shown in Figure 1, which refracts the solar radiation towards a central focus point. The film can be manufactured using a novel roll-to-roll manufacturing method at a fraction of the cost of conventional solutions. Due to the low-cost lens and usage of standard components, the collector has the potential to deliver very low-cost heat.

However, two barriers were identified as limiting the commercial adoption of the technology:
• The lifetime of the original film was only 3-5 years, reducing the economic viability
• The current design features a number of safety concerns that have the potential to lead to injuries or cause material damage

To address these two barriers, the project "New silicone-based lenses for low cost concentrated solar heat" was initiated as a collaboration between Heliac, the Technical University of Denmark, Inmold, and E.ON. The project was financially supported by the Danish Energy Agency's Energy Technology Development and Demonstration Program under grant number: 64018-0606.
The aim of this report is to present parts of the results of the project, namely a comparison of the transmissivity of alternative lens materials and an investigation of the undesired focus spots produced when not in tracking mode.