VENDOROVERVIEW
sunlight) and concentrate them at magnifications up to 6,500 suns. The concentrated light is focused on an optical device that spreads the sunlight evenly onto individual cells, each of which is smaller than a thumbnail. The concentration at the cell level is upwards of 1,000 suns – in other words, the optic system produces light up to 1,000 times the normal intensity of the sun, which is then captured by substrate-based cells. Figure 2 shows the Pyron Solar HE Optics System.
The resulting modules, consisting of connected cells, are able to achieve efficiencies approaching 30% and considerable higher energy output at a significantly lower per-unit cost for the installation footprint. Obviously, the concentrating optics are most efficient when they capture the highest possible amount of sunlight at all times.
This is achieved by a dual-axis tracking system that follows the sun along the horizon over the course of the seasons, and from sunrise to sunset each day. Dual-axis tracking increases the number of kilowatt-hours produced over static installations.
Another difference between conventional PV and concentrated photovoltaic has to do with the photon-absorbing material used in the cells. Instead of crystalline silicone or thin films of PV cells, CPV employs multi-junction cells that incorporate three layers. Each layer is designed to absorb a different wavelength for improved and fuller absorption of electromagnetic radiation over the solar spectrum. In short, those cells are able to generate electricity from the widest possible spectrum of the sun.1
Energy / kW
The effort to produce a viable, cost-effective CPV system is resulting in the implementation of a number of creative approaches. To suit the target market for CPV installations (utility scale solar developers, off-grid rural/village electrification, project developers, and larger commercial installations) one technology, employed by Pyron Solar, offers an interesting technology innovation.
The Pyron Solar Technology
The Pyron Solar system differs from all other CPV systems in the market – the initial product is a 60 kWp DC CPV generating system with dual-axis solar tracking that is protected by a number of issued and pending patents. The system is comprised of three 20 kWp DC floating arrays whose tracking system in azimuth is driven by a small 12V DC motor. Each array is 45’ in diameter. Figure 3 shows Pyron Solar’s 20kW full-scale prototype under construction at SDG&E Mission Skills training center.
Pyron has a very low-profile dual-axis tracking system, accomplished by nesting its modules, ideally spaced, on a floating ring array. The water provides many advantages: highly efficient cooling, establishment of a perfect horizontal solar tracking
HE Optics System Incoming Sunlight
Figure 2
Lens
Optic Cell
71
Reference:
1. Multi-junction III-V cells are e.g. a product of Spectrolab, Inc. Competing
concentrator cells, originally developed for space and
terrestrial applications, can be obtained from other manufacturers as well. The Spectrolab cell holds the current record for conversion efficiency over 39%. The efficiency of the Spectrolab cell has been measured and confirmed by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).
www.solar-pv-management.com Issue V 2010
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