Solar concentrators

In the photovoltaic industry, a concentrator is a mirror that reflects additional sun radiation to the solar panels. By this, the solar panels get more light and produce more electricity. The concentrators can be produced from various materials such as stainless steel, aluminum alloys, silver coated polymers or silver coated hardened glass.

New Tracking Solar Concentrator

The principle of the tracking stand keeping the solar panels in the perpendicular position towards the solar radiation all day long is described on the site “Solar Trackers”.

Usage of such a stand considerably enhances the amount of the energy generated. Another increase in the energy generation may be reached by the application of the Sun radiation concentrators.

However, the current concentrators had certain disadvantages, which have been removed by the new configuration of the whole solar system.

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The new system is a relatively cheap TRAXLE Solar Tracker with additional mirrors, however, unlike the V-shaped concentrator, with the ridge concentrator, the outside mirrors have been totally eliminated (Fig_1, Fig 2). The internal ”ridge“ is formed by a slight (ca C=1.6) radiation concentrator. As for the one-axial trackers with both the horizontal and polar axes, the mirror should be prolonged at the edges behind the photovoltaic panels, so as to secure the homogenous lighting of the solar panels also with the seasonal angle amendment between the panel and the sun traveling panel in the sky.

This triangular prolongation on both edges is illustrated in the first figure. With the Solar Trackers having the polar axis and an adjustable pitch attitude in accordance with the season of the year, the prolonged mirror is not necessary.

Second figure shows the lateral section trough the solar photovoltaic system with the rack radiation concentrator.

It is an advantage that the solar concentrators for the photovoltaic systems do not require any highly specialized and expensive mirrors. However, the mirrors must be resistant to any weather conditions for the period of ten years as the minimum and must be with high total photons reflectance in the wave lengths intervals of ca l=300-1100nm.

Mirrors May Be Made from

• Rolled plate from stainless steel with a special surface finish
• Rolled aluminum plate protected with a polymer finish protecting against weather conditions (PVF)
• Silver-coated acrylate foil
• Aluminum-coated acrylate foil

The material b) should be best in the process of the mutual comparison of the reflectance and the price. Instead of the PVF coating the aluminum mirror may be protected with a transparent self-adhesive PVF foil. The production of a self-supporting, bent, sheet-metal mirror is a very easy matter.

The new, tracking solar concentrator is highly compact, simple and reliable. It was successfully tested on current mobile stands. Unlike the V-grooved concentrators any other supporting system for the mirrors shall be necessary. Therefore, the moments of forces caused by the wind have been significantly reduced.

The new solar concentrator is of common availability. The standard version of the moving solar concentrator may be adjusted from two small photovoltaic panels (50W) up to ten large-size photovoltaic panels (120W). Such a large, mobile, photovoltaic system is in the conditions of a dry sunny climate an equivalent to a stationary system with twenty photovoltaic panels (120W). The application of a solar concentrator to various mobile systems is also very simple. It may be applied for one-axis tracker with both horizontal and polar axes, for two-axis trackers, as well as for trackers rotating by 360° for applications in the space or behind the polar circle.

The concentration ratio (ca C=1.6) reduces the temperature of the solar panels in comparison with the concentrators with a higher radiation concentration, which has as a consequence also that the efficiency of the photovoltaic transformation is higher. The degradation of the panel encapsulation is prevented as well. The new arrangement also enables better air motion around the collector in comparison with the V-chute. Thus, even the more efficient cooling has been achieved. The concentration ratio (ca C=2.4) with the standard V-chute concentrators causes the EVA encapsulation turning brown and a decrease in efficiency of the photovoltaic energy transformation because of a higher panels temperature.

The new tracking solar concentrator mounted on a mobile stand may double the annual amount of the energy produced in comparison with the configuration, where the solar panels are mounted on stationary stands. An increase by 100% is possible in the dry, sunny climate conditions (for example northern Africa, Arabia, Arizona, western Australia, etc.), an increase by 70% is possible in the conditions of central Europe. The increase in pumping capacity may reach up to 150%.

The annual energy production comparison between stationary photovoltaic panels and panels mounted to a mobile stand with a polar axis and with a solar concentrator was carried out near Prague (50° of the geographical latitude). The results show that on a bright day in July (6.8 kWh/m2.day) the increase in the produced energy measured was by 107%. Photogallery