Hi All,
I hope you can bear with me while I discuss some speculative and somewhat half baked ideas for improving PV performance. Some of these concepts have been tested, some are from patents, and some are just from my own brain. When I worked for a tech company about 6 years ago I was tasked with reviewing the patent literature to find any ways that PV and thermoelectric performance could be improved electronically. I found considerable material in both areas. I'm starting to discuss some of the thermo stuff in the newbie section, but it seemed more appropriate to put the PV stuff here. In this post I'll only talk about what might be called 'parametric' utilization.
1) The C of a solar cell varies widely near the maximum voltage, and less so at lower voltages. This principle was used in a patent in the 50s, assigned to the Navy as I recall, that made a solar cell into a parametric oscillator for power transfer at a distance. A light beam of oscillating intensity was fixed on a solar cell in a balloon or perhaps satellite. The solar cell was part of a circuit tuned to twice the oscillation frequency, and the variation of C of the solar cell drove parametric oscillations in the tuned circuit, whereby power could be generated to run sensors or such. A rotating mirror near a solar panel would create variations of C in the panel, and a tuned circuit associated with the panel could tap these parametric oscillations. The AC would be isolated from the DC output. The output of parametric oscillators with a fixed C variation is dependent on the oscillation frequency, so the faster the mirror rotated the more power would be generated.
2) The capacitance of the panel varies with ambient light and temperature changes even at night, so panels not connected to controllers could be charged as capacitors when their C was high, and then discharged into a load or storage when the C dropped. A sensor cell connected to a capacitance bridge or or other C measuring setup would determine when the C of the panel was changing to control the charge/discharge circuit. In this case, the output power depends on the level and number of C changes, as well as how much charge is put on the cells in each cycle. Such devices were used, with pyroelectric capacitors rather solar cells, in the 50s to power ocean buoy transmitters and such. (the 50s were the true age of weird technology!)
3) Finally the C of the panel can be actively changed electronically, to generate additional energy. In this case one group of cells is switched in and out of series with another group to create the C changes, and these are then picked up by a circuit tuned to the switching frequency, or more ideally twice that frequency, as the harmonic usually has more power in parametric circuits. This is the most speculative idea since I haven't seen this in print or in a patent.
Although these technologies may seem strange, they are completely conventional, although not used much outside of low noise amplifiers for radio telescopes, optical fiber amplifiers, and other esoteric devices. There's no reason why the principles couldn't be applied to PV.
The next installment will be about using the PV cell as a charge storage device rather than a current generator.
Fred
