I am in the process of reconfiguring my
solar system because I was disappointed with the performance of my first attempt. In trying to figure out why things did not go well initially, I have dug much more deeply into the subject and I was wondering if more experienced
solar people than I could critique my thinking.
I believe I have identified three areas that contributed to my problems.
1.
Wiring size, length and losses. I was unaware of the calculators (
DC Cable Sizing Tool - Wire Size Calculator - MM2 & AWG - solar-wind.co.uk) that quantify those three parameters. With that tool, I am relocating the controllers, shortening up the wire runs, oversizing the wire gage and ensuring that all
cables are multi strand or tinned multi strand.
2. I have a number of different
panels totalling 290 watts at 12v. My
research tells me that in a parallel array the controller will "see" the lowest voltage within the array. This is not a concern in static installations such as on a roof top, because all
panels are equally exposed.However, on a
boat, the panels are almost never equally exposed, there is almost always some shading, especially when sailing. So, even if all of your panels have the same nominal voltage, shading will vary the voltage as seen by the controller. In effect, our solar arrays are being controlled by the most shaded panel.
3. Based on the thinking in Point 2, the controlling panel is a moving target, since shading is never static. The effect is minimal if the
boat is at
anchor and either bow or stern to the sun. Whenever the sun is not on the boat's axis, or the boat is heeled, we have some form of shading. The panels one one side of the boat will be exposed to less sunlight that the other so it doesn't matter how sunny it is on the sunny side,the shady side is controlling the output of the entire array. My solution is to have two controllers, one for the panels on the starboard side and one for those to port. My thinking is that this will allow the sunnyside to operate at its maximum voltage while the shaded side does its best, without degrading the entire array. I may be particularly sensitive to this issue since my boat is a
ketch.
I believe there was an oblique reference to this arrangement by Erik Dolson in the recent Thread, Solar: Panels, controller so perhaps I am not totally in left field. However, electrics are not my strong suit so any advice will be very welcome.