I've spent years experimenting with panel placement on my own boat.
My 26 foot Pearson
Ariel has very limited deck
space. Still I managed to mount 290 watts of panels. Instead of installing one set of panels that have a nominal horizontal alignment (pointed straight up), I installed 150 watts of panels on the deck
aligned to vessel-vertical (not visible in the photo), and 140 watts on the port and starboard shrouds. My design goal was to produce power throughout the day's arc
of the sun without the effort and mechanical complexity of a single
large adjustable panel on a vessel that continually rolls in swells and changes orientation (especially when tacking). I've spread out the panel orientations as much as possible.
Conventional wisdom says that the panels on the shrouds, which are polycrystalline type, should produce very little power except when the sun is near the horizon. In fact, those two panels, which comprise less than 50% of the total capacity, generate more than half the power output.
panel that is facing away from the sun still produces about 25% of its capacity due to bounce-light off the water
, and the array performs very well in diffuse light conditions (overcast skies).
The panels were chosen to have very similar Vmp (maximum power voltage), and all of the panels are wired in parallel through steering
diodes for each panel. I have a single MPPT controller. Individual MPPT controllers would improve performance, but only by a few percent (partially negated by multiple controller operating currents), and I traded that off for simplicity, space, and cost. Vmp does not change substantially with illumination. If parallel-configured panels have closely matched Vmp values and reverse currents are blocked by steering
diodes, implementing multiple MPPT controllers achieves very little.
I have people who are indoctrinated in the belief that panels have to be horizontal tell me that my shroud
panels can't work
- until I demonstrate that my polycrystalline panels aligned 45 degrees off axis to the Sun still produce 75% of maximum power and the panel facing away from the sun still produces 25% capacity when on the water
. There is very little data provided by panel manufacturers on panel performance in overcast conditions (which predominate here). My testing indicates the optimum configuration in that condition is a electrically parallel panel configuration in a hemisphere arrangement. I've done as much as I can to replicate that configuration.
I've also been challenged by claims the windage introduced by the shroud panels will disrupt handling of the boat. Since the panels are within inches of the center of lateral resistance, they have no practical effect on yaw stability, and are low enough to not substantially effect roll stability. With wind
abeam, they probably increase leeway slightly, but I can't detect the effect. Finally, as panels heat up, their output declines. The suspended panels receive maximum possible airflow.
The panels have so far survived 45 knot
winds and 6 years of continuous exposure. I did reinforce the frames with aluminum
flat stock to prevent twisting (racking).