Having warm water for showering and washing dishes while at anchor for an extended period can be a luxury for the cruising sailor. We at Custom Marine Products have come up with an easy and convenient solution; heating water using radiant energy from the sun.
Here's how it works:
Solar panels get quite warm on sunny days. The back of a solar panel tilted toward the sun may reach 140° F. Mounting a heat exchanger (collector) to the back of the solar panel enables the collection of radiant heat passing through the back of the solar panel. Circulating water from the water heater through the heat exchanger heats the water in the water heater. The water heater becomes a heat storage vessel. Water is circulated using a low draw circulation pump designed for this purpose so very little electrical energy is consumed.
You no longer need to run your engine at anchor to heat water.
Heat water to 115° F+ in an hour.
Kits are available for all CMP rigid panels and many other brands
Kits include: heat collector, insulation, panel backing, pump, tubing.
Click here for more information.
We tested our new 150 watt polycrystalline solar panel on a 35 day cruise in the North Channel area of Northern Lake Huron. This panel was equipped with the prototype of our solar water heating system which will be addressed in another blog entry. The solar panel was mounted on our pole mounting system and was rotated toward the sun The boat equipment and cruising pattern was essentially the same as last year (See prior blog entries). We were powering a freezer/refrigeration system, instruments, laptop computer, radios, autopilot, windlass and LED lights. Data was gathered using the remote display on our EP 10 amp dual output solar controller. The solar panel performance met our expectations. Our house battery bank consists of three 120 amp hour flooded batteries.
Both battery banks were usually fully charged by 2 PM when at anchor and on mostly sunny days so we often had excess power.
Data comparing the performance of the 150 watt solar panel with our 140 and 160 watt panels is presented below.
Average amp hours per day produced under various conditions:
150 Watt poly 140 Watt, poly 160 Watt, mono 160 Watt, mono
2015 2012 2013 2014
Overall average output per day 49 amp hours 53 amp hours 48 amp hours 48 amp hours
Sunny days 60 69 71 69
Mostly sunny days 56 50 50 56
Mostly cloudy days 36 35 37 39
Cloudy days 22 32 28 20
Avg. Output on days at anchor 60 62 61 51
Avg. Output when engine was used 42 43 44 45
Min amp hrs for a day 4 27 28 4
Max amp hrs for a day 84 74 77 76
Max amps output 11.8 amps 10.5 amps 11.5 amps 11.4 amps
This data is intended to provide a general idea of what to expect from the solar panels under various conditions. The two primary variables are the amount of sunshine and the running of the engine (the alternator charges the batteries so the controller shuts off power from the panels). Because the panel was equipped with a water heat collector on the back, it may have run hotter on sunny days when the water circulation pump wasn't run thus degrading the performance by up to 10%.The average panel output on sunny days at anchor with no motoring was 67 amp hours.
Our top-of-pole solar system addresses the need for power while at anchor and under sail. In fact, we have found the solar system usually provides us an excess of electrical power while cruising. Now we find the only additional thing we need while at anchor for an extended period is warm water for showers and cleaning dishes. Sure there is the old black bag absorb the sun's heat option but this is a bit cumbersome.
Then there is the option to run the engine until it heats up the water in the water heater. Running the engine for warm water is inefficient and undesirable.
Now we have what promises to be a pretty good solution; solar heated water. Because the solar panel is dark in color, it absorbs a significant amount of the sun's energy in the form of heat. This is dissipated through the back and front of the panel by air currents. By attaching a heat collector/exchanger to the back of the panel, properly insulating it and circulating water through the heat exchanger we are able to collect that excess heat and store it in the water heater tank or in a separate holding tank. While still in the test stages, we have completed proof of concept and can make the heat exchangers available to DIY mariners who are interested in setting up such a system. We plan on offering a complete water heating system retro fit kit within the next year.
Initial tests indicate that with our 140 and 160 watt systems we can heat 3 gallons of water from 60 to 110 degrees F in less that a half hour on a sunny day with the ambient temperature of 65 degrees F.
Our top-of-pole system is about to be a 3 in 1 assembly; solar panel mount, outboard motor crane and solar water heating system. Call us if you are interested in participating in our test program.
Thomas Trimmer has been cruising with his Ericson 38 sailboat on the Great Lakes for over 20 years. He has pioneered the use of solar energy for wilderness cruising. He is continually designing and building equipment to simplify and enhance the cruising experience.