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FocusFresnel - Concentrating Fresnel Lens
The Fresnel lens is a very interesting optical device. In 1822 Augustin Fresnel designed a large optical lens made out of flat glass plate. Instead of the massive volume of a large conventional lens, he designed the plate with a series of concentric grooves each of which has the same profile as the corresponding part of a conventional lens. This provides a flat device with the same optical properties as a normal lens - actually this depends on the number of grooves. This gives an immense saving in material, which reduces the production costs. These lenses are ideal for solar energy applications for concentrating solar energy: either to get higher temperatures with a thermal absorber, even for steam generation; or for focusing solar radiation on photovoltaic cells, thus reducing the required photovoltaic cell area and hence the cost of the generated electricity. On sunny days you can do great experiments with this lens: For example, trying to set a piece of wood on fire or boiling water in a test tube. Danger! Be careful: Never put your finger or eyes in the focus of the lens.Technical data
- Dimension 18 cm x 26 cm
- Focal length ~30 cm
- Thermal focal power ~40 W
