Duplicat's Diary

All that power!
by Rick at 08:43:06, 2020-03-29 (day 2156)

I mentioned that I’d put more solar power onto Duplicat whilst she was on the hard. We now have 3 x 330w on the hardtop (from before) and 3 x 375 watts over the davits (new). So why do I want 2.1kw of solar? The simple answer is... hot water!

The old setup was pretty close to meeting all our daily needs every day. We could spend quite a bit of time at anchor without having to run the generator (other than if we were diving, and thats only a short 30min runs to fill tanks). This included making all the water we needed (and we use quite a bit washing down dive kit). Early in the season (whilst we are still out of the tropics, like now) it was a bit tougher and I found myself reaching for the generator a couple of times last season whilst waiting to sail to New Cal.

However, during last season, we were progressively coming back from dives colder and colder and began to dream of a hot shower. We could leave the solar shower bags out, but we would forget, or they don’t work well for some crew who can’t reach up through the deck hatch to use them efficiently.

At the end of last season, Tom, David and I thought long and hard about this. The original plan was to run some pipe work up into the sun and pump water or glycol around it - but there are a few drawbacks. Glycol breaks down into an acid when it gets hot, so you need to run the circulation pump all the time (even when not on the boat) and using water from the fresh side is awkward on my setup due to the thermostatic protection valve at the tank.

It become obvious that the best way to do it was add more PV (photovoltaic) and then divert some of the power to the immersion heater when the batteries were getting full. That’s what I trialled today.

The numbers: The batteries were 176ah down over night. By 9:30am we’d recovered 76ah, so I diverted about 500watts to the immersion heater using some electronics I made whilst back in the UK. The batteries continued to charge (at up to 40amps), and the heater was taking about 2.2amps at 240v. Around 1pm I put the washing machine on (also on the inverter, cold wash). Once that had done, I turned the water maker on to replace the water I’d used - about 80litres. By 4pm, the hot water tank was fully hot (thermostat hit), the batteries were full as were the water tanks. We’d generated over 530ah from the solar panels.

To say that I’m delighted with this new setup is an understatement. Its particularly useful at the moment as I’m not moving around much - waiting for cyclone season to end and also my furler to arrive (hah, shipping in the present circumstances could be interesting). So I’ve been here off South Stradbroke since Wednesday, not run an engine since then (other than 5 mins of generator to check all was ok after the service) and yet I still have full water tanks, full batteries and most importantly, hot water.

The shower this afternoon was lovely....