Tuesday, August 18, 2015

Solar Panels

Solar panels are installed and making electricity. The past few weeks has been a crash course in solar power technology. We ended up with six Kyocera panels for a total of 840 watts. We went with Blue Sky MPPT controllers for their compact size and excellent efficiency. With solar panels, shading is the enemy as it will reduce the output of other panels that are in the same circuit. To provide some isolation (which minimizes shading on one panel from affecting the rest of the array) we wired the panels in parallel, with home runs from each panel down to the controllers. We put three panels on each controller to further isolate the effects of shading on the overall output and to provide some redundancy. Each panel is fused before the controllers and the output of each controller is fused where it meets the positive bus of the house battery bank. This was a lot of wiring and took most of a three day weekend to finish. With everything online, we have been able to pull 50 amps out of the array at 14.2 volts during the day with clear skies. It could probably go a little higher if the house batteries a little less charged up. We had to turn on a lot of electrical stuff to get the controllers to see enough demand to get the output up to 50 amps. Our target for the rooftop array was 50-60 amps max output so we are pretty close to our expectations. We have been "off the grid" for three days now, with daytime solar charging seeming to keep up with our 24 hour demands. Each afternoon, our "state of charge" for the house batteries is back up to 100%. The nice summer weather and long days have helped. We are still using the shore power for the electric element in the water heater but when cruising, our domestic hot water can be heated on demand with the diesel burner that provides our hydronic heating circuit or via the heat exchanger with the engine coolant when we are underway. Everything else is running off the 12 volt house bank (refrigeration, lights, pumps, etc.) or using the AC output of the inverter (misc appliances, home depot freezer, and some electronics) which is fed by the same house battery bank. I think that a couple of more panels (maybe on top of the aft dinghy davits when we get those built) will give us a very solid solar power set-up to meet most of our demands most of the year. A wind generator would be a nice add-on too. Of course the beauty of solar is no moving parts and little to no maintenance.


  1. A new DD 462 owner has posted some comments about his being off grid with his boat using PV and wind generators on Duck Talk, http://ducktalk.net/eve/forums/a/tpc/f/5621093711/m/5227067776?r=5257029776#5257029776


  2. Sounds like they are experiencing very similar performance to ours. Right now we are seeing our state of charge at around 90% first thing in the AM (from evening and overnight electrical use). When I get home in the afternoon it's back up to 99-100%. Having very efficient lighting and refrigeration helps, but we are using a standard home depot chest freezer and other AC appliances that run off the inverter and the 12 volt system seems to be keeping up with no charging from shore power. Thanks for the link.