Concentrated Photovoltaic (CPV )
Photovoltaic energy represents very important renewable source of energy, as the insolation of the earth surface reaches the values up to 1000 W/m2. Using the photovoltaic effect, the solar energy is converted to the electrical energy.
The efficiency of wide-spread stable solar systems without concentration of the solar energy (i.e. the sun factor = 1) varies from 8 to 18 %, depending on used solar sensitive material (thin films, Si amorphous, poly- or mono-crystals, etc).
The second type of solar systems is based on the concentration of the solar energy on the small photovoltaic chip with high concentration factor from 300 to 1000 suns. In this case the precise 2-axes tracking of the sun is necessary. The panel construction is then based on refractive (lenses) or reflective (mirrors) concentrators and special solar chips. The maximum efficiency of sun light-to-current conversion is now possible with multi-junction solar cells based on III-V compound semiconductor materials. In comparison to silicon, III-V materials allow high yield operation even at concentrations of hundreds of suns. Currently the up-to-date cells show an laboratory efficiency of 40 % at 500 x sun and 25°C. The next generation of cells with 42 % are in development.
In our solution we have focused, in cooperation with the firm ELCERAM a.s., to the development of CPV solar systems based on special Fresnel lenses and ceramic-encapsulated high efficiency CPV solar cell with nominal efficiency of 38 %.
On the pictures are visible the schematic drawing of CPV system with Fresnel lens (left) and (right) the experimental panels placed on the tracker and complemented by sun tracking electronically navigation system (top right). We were participated on both tracker and navigation design and construction.
On the following graph is the sample of the measurements of V-A characteristic and maximum Power of the solar cell in realistic condition on the sun with the intensity of 850 W/m2 , using Fresnel lens 70 x 70 mm.
142 21 Praha 4
Measured values of the solar module parameters
The solar cell was encapsulated in the ceramics according to Datasheet mentioned bellow:
In the present is finishing the development of the solar panels, each containing 96 Fresnel lenses and 96 solar cells of the active place of. 0,5 m2. These panels will be placed on the tracker with navigation system and the long term parameters will be measured. More information will be published after testing of this system.
The solar system is developed with the support of the Grant provided by the Ministry of Industry and Trade of the Czech Republic.