I first noticed a problem with our solar panels when we got back to the boat after our enforced break last year. It became clear that it wasn’t just my over-optimism on midsummer’s day. At local midday with a clear sky we were generating 7W – not even enough to power the lights, never mind the kettle or the propellor.
The performance gradually deteriorated further. We eventually got confirmation from Ortomarine that another boat had had similar issues. Sticking the solar panels to a metal roof was recommended by the supplier, but it turns out to be a poor idea. Ortomarine offered to fit replacement panels, charging us only cost price for the replacements.
Rob and Ian came out to fit the panels in October, but had to abandon because everything was too wet. When they suggested coming again today, I hatched a plan. By mooring up overnight under the Warwick Bypass we could give ourselves a large concrete umbrella. This was probably our least enticing mooring ever, but when Rob and Ian arrived bright and early (they were bright, we were just early) the roof was dry! We helped carry a few things from the van and then tried to keep out of the way of the workers.
Before work had got started, there was a blustery shower. The stern deck was soaked in minutes, but the roof was completely unaffected. I was characteristically smug. The main part of the work involved drilling through the old panels directly above the electronic unit which rests in a matching hole in the roof. Removing the old panels would have been a considerable effort. This way the new panels can be stuck directly on top of the old ones.
The idea is that the old panels will provide protection for the new ones. The hot roof will be thermally separated from the new panels, and any expansion will be buffered too. Inside the boat, the roof trim on the port side covers all the relevant parts. We’d cleared most things from that side of the boat in preparation. I’d taken the trim down myself when investigating last summer. Today the trim was reluctant to come down – a winter boat is a little shorter than a summer one so the wood was tightly squeezed.
As worked progressed to wire up the new panels, some confusion arose as to the location of one of the ten diode blocks. I had removed some of these last year when I was trying to make best use of the panels that were still working. I found one in the bathroom cabinet where I knew I had placed it, and there were eight more in situ. We still haven’t found the tenth one – I can’t imagine what I could have done with it.
Fortunately this may be academic as Rob concluded that some of the others were beyond re-use. He has some more on order, he hopes they’ll be delivered next month. Fortunately the role of the diodes is not critical. When a panel is in shade, the other panels will try to drive current through it. The diodes allow a shaded panel to be by-passed. Without them, we will get slightly poorer performance in some conditions.
Rob has managed to rescue enough working diodes to equip the front string of four panels. He will send me replacement diodes when he can, and I should be able to install them – if the weather is warmer by then, removing the roof trim should be easier too.
Once everything was sorted, we drove out from under the bridge in to the warm afternoon sunshine. Our power generation leapt to 750W – ten times the highest value we saw last October. During the afternoon we’ve generated more solar power than we had for the rest of the month combined.