We have finally had a proper day of solar energy testing: free of the dock, booms out so no shading, minimal overcast. The results are surprising.
We were worried that we’d not care for the appearance of this array. However, it does not bother us on or off the boat, and we’ve just had a couple of days with the new look. Within a week they will disappear from our consciousness.
The transition from deployed to storage mode (shown above) takes less than three minutes. Once we add a few Wichard snap hooks to the tie downs, this process will go even faster.
The final tilting and swiveling mechanism is very simple, and robust. Main support is a schedule 80 one inch (25mm) 316L stainless steel pipe (3/16″ /4.5mm wall). The masts are two inch (52mm) aluminum tube with 3/8″/10mm thick wall. There are no bearings.
Paralleling the pivot pipe are a pair of two by one inch aluminum rectangular tubes. The solar panels themselves are electrically isolated from the framework using G10 (epoxy) blocks.
Anchored here in front of Beaufort with minimal swinging room, and traffic, we decided to store the panels so they didn’t overhang. It was the end of the day, the sun was low, and we were pleasantly surprised to find an output of 10 amps/25 volts from one of the two arrays in this orientation. That is a little under half power output, which we think is wonderful at the end of the day.
The Outback 80 MPPT charge controller through which these four Sunpower 320 Watt panels feed the batteries, reports on maximum and minimum voltage/amps in and out plus the day’s power generation. Yesterday the maximum amperage we saw was 43 at 26.5 volts. The theoretical max is 50 amps. However, this is with panels at right angles to the sun, standard temperature (25C), with no allowance for wiring or conversion losses. Chuck Meier of SALT in Marathon, Florida, who supplied our panels, did a few calculations for losses from temperature, conversion, etc, and came up with 44 amps. So, we are right on target here.
Output varies with the changing sun angle and cloud cover, or lack thereof. The real question is total power generated for the daylight period. The Outback 80 reported yesterday at 7.5kW. Today we did not deploy the panels until 1030, and by 1500 it was overcast with a thunderstorm blocking the sun. The reported accumulation was 5.4kW.
Our daily power burn is between 7500 and 11,000 watts per day, depending on how much time we spend on the computers and whether or not guests are aboard. If we can average half of our daily power burn with the solar panels it would be great. We could easily cut our burn to 5/6000 watts if needed, which means the solar system is capable of sustaining us if required.
We have not yet totaled up the costs, but the old rule of installation doubling the acquisition cost will probably hold true. We think this makes sense compared to a backup genset.
It will be interesting seeing how this works out over the summer.