We are at anchor, it is quiet, just three other cruising yachts in this bay, and the sun is shining for a change. With the sun now dropping towards our neighbors in the Southern hemisphere, or the earth tilting if you prefer being accurate, the sun’s angle to our flat solar panels is less than optimal. But is it worth adjusting the solar array angle?
At 0730 sun time (daylight savings time still being in place here), with the four panels flat we were seeing 10 amps at 25 volts output. With the stern facing southeast, angling the panels on a common axis, and bringing them almost vertical, kicks up output to 33 amps. The stern then swings to the southwest, and the panels are no longer aimed directly at the sun.
As a test we aimed the starboard array directly at the sun. This partially blocks the port array, so that its inboard (shaded) panel is shorted out and therefore not contributing. We are surprised to find that the three correctly angled panels produced more power–30 amps–than the four panels on a common horizontal axis.
If we were tied to a dock, held in place with a stern anchor, or steady trade winds, it would be easy to optimize angles and thereby improve average output during the day. But for us, with the boat moving at anchor, the answer is still flat panels, on the assumption that we do not want to bother with constant changes. However, if we needed to, we now know that with a little extra work, say a stern anchor, we could substantially increase daily energy capture.
This leaves the question of a tracking system, of which there are now commercially available systems. You could generate the same power from three panels as we do from four, if your array kept the sun at optimal angles. However, adding a fourth panel is a much simpler and less expensive method of matching the tracking power output.
We continue to be impressed by the function of these four panels, which have essentially eliminated the need to run the genset in the short-hop, long-stay cruising mode we are presently enjoying. And there is something very satisfying about the ability to generate all this power without burning diesel.
Yesterday, for example, we did three loads of wash, the big computer with its external drives was operating for eight hours, three meals were cooked electrically, and we consumed just 3% of our battery capacity beyond what we received from the solar panels (clothes were dried on the life lines rather than running the dryer).
It is 0700 the next day (sun time) as we edit this post, and we have taken five minutes to put the panels back to vertical; those 30 amps are again flowing at this early hour.We are going to work on making the panel rigging system more amenable to quick angular adjustments.
Two days later, we are on a mooring in Southwest Harbor, swinging back and forth with the tidal current.Panels are flat. In Maine, at the end of August, on a sunny day with 20% cloud cover, those four panels produce 7.4kWh.