A Smaller Scale Concentrator Technology Built on Multijunction Cells

A more modest system, in principle, similar to that described above is marketed by SolFocus. The individual parabolic glass mirrors are smaller and are packaged in arrays provided with two-axis tracking of the sun. A conceptual sketch for the SolFocus devices is shown in Figure 7.8. The literature suggests concentration in the range of 500-650. The dashed curve at the bottom of Figure 7.1 shows that a two – junction tandem cell at 500 suns has the capability of about 55% efficiency, a large improvement over single cells. SolFocus states the efficiency of their multijunction solar cells is 38%.

Подпись: Figure 7.8 Artist’s impression of concentrating solar cell including advanced GaAs-based tandem junctions. SolFocus markets arrays of these devices provided with two-axis tracking of the sun. There is a large

The SolFocus concentrating cell design addresses the problem of heating of the cell’s PN junctions, by insertion of a nonfocusing optical rod to transmit the multiplied active spectrum, but not the unutilized and deleterious infrared heat spectrum, to the tandem junctions. Concentration of light (by about a factor of 500) with individual parabolic and accompanying secondary mirrors addresses the issue of cost and availability of elements, for example, Ga, used in the cells, and of the multijunction fabrication, since the concentration reduces the area of solar cell required. It appears that water-cooling is not required to operate the tracking panels provided by SolFocus because of the smaller scale and the use of the glass rod delivering the active spectrum from the mirrors to the cell.

change of scale between this approach and the approach represented by Figure 5.8. SolFocus, Inc., 510 Logue Avenue, Mountain View, California, 94043 (2008) http://www. solfocus. com/en/technology/.

According to the Economist [91], arrays of multijunction concentrating solar cells are available from Sunrgi, Inc., which are reportedly 37% efficient at 1600 sun concentration and can produce electricity at 5 c/kWh. (By comparison, the price of electricity in New York is 14 c/kWh.) It appears that the junctions are similar in design to those shown in Figure 7.3. As stated, this is a very favorable cost figure, which awaits confirmation.

7.1.3

Updated: October 27, 2015 — 12:10 pm