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Solar panel controller
On Fri, 09 Feb 2007 23:09:58 +0000, Ian Malcolm
wrote: Goofball_star_dot_etal wrote: I do see where you are coming from, as both myself and Larry made the obvious but incorrect assumption that a PV panel could be modelled adequately as a controlled voltage source. It was labelled as an assumption and an approximation, i.e. a simplification, NOT A FACT. Yes but it is not an approximation, it was totally wrong and useless not "useful" at all. As it happens, the only effect that correcting that has is to move the modelled MPP for the better panels above the charging voltage of a Lead acid battery. This means a small simplification in the topology of the switching converter. A closed loop converter based on the simplistic analysis would soon settle within a few percent of the MPP anyway so the results would be almost identical. The MPP is light and temperature sensitive. The quoted patent states that they sample the open circuit volage and apply an offset to arrive at the (instantaneous MPP) Leaving out any personal attacks *this* time, Mr Ball, Their approach is actually questionable *FOR A MARINE APPLICATION* as they make no provision for extracting power if the panel voltage is below that of the battery. This frequently happens if the panel is partially shaded and some cells bypass diodes are conducting. This wouuld be a not uncommon situation aboard an yacht at anchor, on a swinging mooring or underway. The panel has to deliver over 140ma at over 14V before *any* power is transferred. Elsewhere they say it is stable down to 0.8A and as it seems to be designed for 10A nominal output, what proportion of the time will it not operate? They seem to be excessively concerned about keeping the converter in continuous operation mode, *Probably* to avoid violating a competitor's patent. It looks like it would be advisable to disable their regulator and run a float regulator if layed up for the winter as the trickle charging capabilities are suspect to say the least. I suspect that the manufacturer the OP was considering were rather optimistic in their test conditions for a 30% efficiency boost, they probably tested it normal to the sun, totally clear sky and at 10 degrees C ambient temperatue into a very flat battery. At more normal insolation levels and temperatures, averaged over a normal battery charging cycle, the 10% to 15% improvement that most other sources claim is more plausible. After all, you CANNOT get more out than you can get at the MPP. Yes. http://www.blueskyenergyinc.com/pdf/...PSB2KErevE.pdf page 8 table 2 |
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