Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 21/09/2012 08:30:01
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lotha timothy m asked the Naked Scientists:
How do I connect multiple solar panels for better efficiency, in series or in parallel?
What do you think?
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Technically, parallel or series would be equivalent.
However, there are a few differences to keep in mind that may be important to your installation.
When you take equivalent power sources. Wire them in series, and you get higher voltage. Wire them in parallel, and you get higher amperage.
One of the problems, however, is if the power sources are not equivalent (shade? damaged? different model?), then you can run into problems.
If you wire your panels in series. Then, if one panel is putting out lower amperage than the others, I think I heard that all the panels put out the lower amperage.
Likewise, if you wire them in parallel, if a panel puts out less voltage than the other panels, it could potentially take power away from the other panels, or at least not contribute anything to the net.
Depending on your wire run, there are less transmission losses at higher voltage. However, for a residential installation, you may choose to keep your DC system voltage under 120V or so, so you may choose to mix parallel and serial connections.
Another option you may consider for "grid tied" installations would be the use of micro-inverters, so that each panel is essentially wired independently.
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Each panel to feed its own voltage converting electronics would probably yield the most power but would also the most expensive and probably unreliable, I think the best thing to do is just to wire them in series/parallel to give the required voltage and try to place them so that they get similar illumination.
It might be sensible to incorporate some current/voltage sensors at key points to check how they are performing so that any defective panels can be serviced.
It would be a good idea to put a diode after each series group before they are paralleled so that any faulty group does not siphon off of power.
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Large Solar panels are already wired up as a series group because they consist of several sections. These are then wired in series groups to get a reasonable voltage for efficient conversion to mains AC. Individual cells only produce around 1.5 volts. Conversion at a voltage this low is very inefficient.
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The micro-inverters are competitive in cost with the larger ones, at least so they say, the costs do add up quickly. They also allow monitoring of each individual panel, so faults can be detected and repaired.