Last year I installed two Renogy 100 watt semi-flexible solar panels on top of my bimini. I have noticed that their performance has been degrading ever since they were installed. I also noticed they were starting to become brittle. Originally, I had designed the bimini so it could be removed without too much trouble, but in the past year I never removed it. There were problems with the design of the bimini too. The edges had curled such that the bimini would collect water. I was going to reenforce the bimini by installing some fiberglass rods, but when I saw what had become of the solar panels, I decided to replace the bimini altogether. I decided to install two rigid Renogy 175 watt panels (like the three 100 watt panels on top of the hard dodger, which were chosen because the fit neatly between the hard dodger and the two backstays.
I began by installing two additional steel tubes from the frame to which the panels on the hard dodger are mounted to the steel tube hoop in the stern of the cockpit. This was easily accomplished using 90 degree tee fittings (the same way the frame for the panels on the hard dodger were mounted). 0ne and a half inch wide aluminum bars were bent slightly in the middle and the panels were mounted to them. The panels were then mounted to the tubes using stainless steel U-straps.
To conceal the wires and afford some protection for the underside of the panels (and my head), I sewed liners out of Sunbrella. The liners are held on with snaps, The bottom half of the snaps are screwed into the aluminum frames of the panels and the top halves of the snaps are installed in the fabric.
The three panels on the hard dodger are wired in parallel (because there is a risk of partial shading by the boom, which would significantly reduce performance if wired in series). However, there is less risk of partial shading of the two new panels over the cockpit, so they are wired in series, which reduces the amperage (while increasing the voltage). I have read that panels that are wired in series tend to perform better under low-light conditions (e.g., at sunrise/sunset or cloudy conditions), probably because the “band giap” is smaller for panels wired in series compared to panels that are wired in parallel.
Although the upgrade increases my solar capacity from 500 to 650 watts, initial tests suggest the two new rigid panels are twice as efficient than the old flexible panels. It seems like the capacity has almost been doubled.
I will note that the new solar panels and frame also significantly strengthens the stern pulpit. I have not been very satisfied with the strength of the outboard engine mount. I intend to redesign the mount with the now-strengthened pulpit. Also, t is my intention to sew removable side panels that will mount to the tubes under the panels and the stern pulpit to provide some additional shade and protection from wind/spray.