The Fresnel Lens

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The Fresnel Lens
The lens looks sort-a like a LP (long play) album, except it’s semitransparent. Most are made of plastic. The Fresnel lens has been around since 1822. The lens is able to generate steam when used with thermal energy absorbers and fluid. It can also concentrate solar energy into photovoltaic cells.

The main benefit of Fresnel solar collectors is their space saving quality and cost of manufacturing. Lens efficiency depends upon the number of groves regardless of it’s flat construction. It’s focal point is close to the lens plate, therefore collector panels needn’t be very deep.Remembering the magnifying glass example, this lens will do much more than burn a leaf. It will set a piece of wood on fire and boil a test tube full of water.

Danger - you should exercise extreme caution when handling one of these in direct sunshine. Due to their high efficiency, allowing eyes or fingers in the focus of the lens could cause blindness and severe burns. It can be dangerous if one is careless.Return to Concentrator List
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Parabolic Dish Collector
This class produces very-very ultra high-temperatures. They can generate steam. They can to power destroy hazardous materials (thermal detoxification).The dish looks like a TV satellite dish. It can be small to very large. The idea is to focus the sun’s energy on a small precise focal point, allowing the sunlight to produce heat. Similar to trough concentrators, parabolic dish systems utilize positional heliostat tracking for both horizontal and vertical axes.
Concentrated temperatures of 2000°,F are possible. Parabolic Dish Concentrators are capable of achieving the highest efficiency of any concentrating system.Return to Concentrator List
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The Parabolic Trough
A Parabolic Trough looks like the capitol-letter U. Its shape focuses the sun's radiation on a linear receiver located at the focus of the parabola. The receiver is an absorbing tube positioned in the troughs focal plane and runs the length of the trough. Fluid flowing through the tube, circulates through heat exchangers where high pressure superheated steam is generated.During the day, single axis heliostats track the sun from east to west to maintain continuously focused solar radiation on the receiver. Large trough arrays are almost exclusively used to produce steam for steam turbine generators. Troughs can focus up to 100 times the sun’s normal intensity. Liquid temperatures can reach as high as 800°,F.Return to Concentrator List
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Power Tower System
Power towers (heliostat power plants) use a central tower in which a fixed target is located. Trough collectors or flat (heliostats) mirrors are positioned so that as the sun sweeps across the sky, the solar radiation reception is maximized.The simplest heliostat uses a clockwork mechanism connected to turn the collector mirrors, or solar panels in synchronization with the earth’s rotation. More sophisticated systems use computers to track the sun.

One site uses over 1,600 heliostats to track solar radiation, reflecting the sunlight onto a 195 ft tower. The intensity of the concentrated energy reaches from over a 1000°,F to over 2700°,F. The hot liquid exchanges heat to a storage (salt) medium for steam generation la