Green Emerald Series Part 1 6

My Soul is full of longing
For the secret of the sea,
And the heart of the great ocean
Sends a thrilling pulse through me.
-”The Secret of the Sea,” Longfellow.

Well hasn’t it been a while since my last blog. I do apologise, but thankfully my wonderful wife Nichola has been writing the blog more eloquently and diligently than I have. I’ve been meaning to write this for a while now but somehow the time and space to sit down and do it never arose. In truth I hadn’t really finished the projects to be able to write about them!

However I am pleased to say Emerald is becoming greener by the day, and I don’t mean in colour. I don’t want to get on a soap box and preach about climate change or pollution, if you want to find out about that use Mr Google and search for ‘robertscribbler’, read his work and draw your own conclusions.

For me what is important is that I live my own life with as small an impact as possible on the environment and world around me, but without the hair-shirt approach to it. i.e. I want minimum harm with maximum comfort!

To that end there are a series of modifications we have made to Emerald that both save money (which helps keep us cruising) and helps us use less fossil fuels so in my mind that is a double victory. The projects were also a good engineering exercise with practical applications of some simple ideas to keep the grey matter working and improve my skills.

There are six basic projects that have been ongoing on-board for a while now (in some cases years!!) that have come to fruition in time for the sailing season this year. We will have a proper test of our success whilst lazily bobbing at anchor in the Greek islands somewhere later this year all being well. The first of these is our long running solar water heating plan.

Currently we have 3 ways to make hot water on board. We have a hot water tank (known as a calorifier) which has an immersion heating element in it. This we use in winter when plugged into shore power. As it takes 750 watts of power, it isn’t really practical to use this in the summer when we don’t have shore power, as we would have to run the portable petrol generator to use it. We can run it off the inverter but it takes over 100 amps out of our expensive battery bank, and they would wear out pretty quickly at that rate of use.

We can also make hot water by running the main engine (which circulates it’s cooling fluid through the water tank), but we don’t like running the engine purely for making hot water. It heats the inside of the boat up and burns 3 litres of diesel an hour, which means both cost and wear and tear on the engine. Diesels don’t like to be run regularly at tick over as they ‘soot up’ so we try and avoid damaging our expensive new engine.

During the winter months we can also make hot water using our wonderful diesel Refleks stove, which has a water boiler inside that heats both radiators and the hot water tank. However we don’t use this during the summer months, as the boat would quickly become a sauna!

This means we only really use our propane stove to make hot water for washing up, by boiling a kettle during the summer cruising season. Therefore we are hoping that the solar water heater will give us warm/hot water during the summer, and help cut our propane consumption down. This will both save us some money, and helping cut our carbon output. It also makes us that little bit more self sufficient, another one of our aims with these green projects.

  1. Solar Water Heater

    This has been a pet project of both Nichola and I now for nearly two years so we are delighted that it is finished and excited that we will get to test it in anger this year at last. We saw an article about a home made solar hot water panel in ‘Practical Boat Owner’ which is a British Sailing Magazine (it was issue no. 557 Feb 2013) a few years ago and it appealed to our sense of frugality. The principal is simple, a copper tube is spiralled onto a metal plate, all of which is painted matt black and mounted in a box. This is insulated underneath and a perspex screen over the top, and mounted in clear view of the sun. It is plumbed into Emerald’s hot water system and pumped into the hot water storage tank.

    We used a circulation pump and a little digital controller which we bought on ebay. The controller was from a company called REuk who make lots of DIY project gear. (we used the 2013 model controller) Their website is below:


The circulation pump also came from ebay and is perfect for the job (search for 12 volt solar pump)

solar pump

The theory of operation is straightforward. There is a temperature sensor at the panel, and one at the hot water tank. When the panel is x deg hotter (set by me on the controller ) than the water tank, the controller switches the pump on to send the water from the tank to the panel until the temperature sensors reach a defined difference (again set on the controller) when the pump switches off. The idea being that the water gradually cycles hotter and hotter through the day.

Even though we are only in March here in the Mediterranean we have already made water warm enough to wash dishes on sunny days. This bodes well for the six hotter months of the year. We want to eliminate running the main engine for hot water altogether in the summer, and drastically reduce our propane gas use by having hot water for the kettle which is already hot before we have to boil it. I’m confident that we will achieve this.


Solar Water Heater in place on top of our bimini

What remains to be seen is whether or not the components will hold up to field use, especially the circulation pump, but if the pump lasts 2~3 years, then we’ll buy a couple of extra spares to keep on board.

The most taxing part of this project was designing the water circulation flow through the panel. We used a number of components such as one way valves to ensure we don’t get cooling at night by reverse circulation. We shall have to wait until May/June to check if this is working correctly. Below is a schematic of the circulation system.

Schematic of water flow

Schematic of water flow

I will cover the other five projects in further blogs. The Green Emerald series will include: Solar panels, arches and options; wind generation; prop shaft alternators; water maker; and conspicuous consumption – the LED challenge and energy use reductions, and perhaps a blog on what future projects I would like to do to reduce our carbon (and hence costs) even further, and whether that makes economic sense and comfort sense for us.

If anyone has any questions please drop us a note, and we’d be delighted to try and help. You could also do this on your house to reduce ever increasing energy bills in the summer months and save just a tiny little bit of the planet.

Fair Winds

Slainte skip

6 thoughts on “Green Emerald Series Part 1

  • James F

    Awesome stuff. Do you have to worry about overheating and pressure build up? I understand that’s an issue with solar water heaters – water boils, system explodes, everyone has a very bad day…

    Shame the old convection setup doesn’t really work for a boat – no way to have your panel lower than your tank. For houses these can be beautifully simple setups.

    • Colin Wright

      Hi James, the tank itself has a pressure relief valve. I wanted to add an auto vent at the highest point of the system but haven’t got the clearance with the boom, above the panel. I can bleed it manually but hoping it will be ok. The engine gets the tank up to 90deg C on a long passage under motor, so fingers crossed, that we can cope with the pressure. I think our main prob will be an air lock if it does boil at the panel. Cheers c

  • carsten

    hi from vonitsa, we are at anchor and found your blog by incident. This marysol from Lagos with the blue windgen blades. See you somewhere, we will winter in bari this year.

    • Nichola

      Hi Carsten, good to hear from you! We are enjoying the quietness of the blue blades. Just missed you by a week in Vonitsa, down on Ithaca now. We may visit the Adriatic next summer so may see you there, we will head back to Sicily this winter.

  • Peter Morgan

    Thinking of doing the same.before I do a couple of questions.
    Firstly, does it work and was it worth doing?
    Can you suppy some sizes, ie how much copper pipe, frame dimensions.
    What pipe did you use for the flow and return from the HW tank to the panel?



    • Nichola

      Hi Peter,
      It does work, yes. I used 10mm bore copper pipe onto a 50cmx50cm brass plate. However if I was doing it again, I think I would use 15mm straight copper pipe, with u bends at each end, and squeeze as much volume of water in as I could. We used a cheap variable speed 12v pond pump from ebay, and a microcontroller from ebay also, which switches the pump on and off depending on tank/solar collector temp. It raises the water approx 20degC above ambient air temp.
      Would we do it again? I’m not sure to be honest. With the decrease in the price of solar I think I would approach the problem differently, with a 100w, 12v immersion heater into the cold feed of the hot tank. I’d power it off the load of our mppt solar controller and it would come on once our batteries are full. Currently we have 760 watts of solar on Emerald (we use a 12v water maker, run a freezer etc so are a power hungry boat), and plan to upgrade this to 910 watts in the near future, which will give us more power than we use to remain completely green on anchor most of the time). It
      was a fun project, and I think was an article in a uk sailing magazine called Practical Boat Owner (PBO), which is where we saw it, and we will continue to use it on the boat as it gives us washing up water most days. Hope this helps.
      Best wishes
      Colin and Nichola

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