Solar Hot Water System

[Simi 60]

We have a standard household 180 litre rheem 240v hws on board that on a sunny day is powered 100% by 9 x 250w panels.

I reckon its not warranted for our usage so when it dies I'll replace it with a 50 litre version of the same.
They come in at around $350

[coopec43]

I don't think the experts cost/benefits analysis of Solar HWS Vs solar panel/electricty/heating element to be relevant as they take into account capital cost and estimated life of units. ( Of course if you worry about cost maybe you shouldn't be boating)

As far as boatys are concerned space on deck would be a major factor. (A tube attached to the stanchions with cable ties would not be a problem)


Clive

[TassieBloke]

Just be done with it using this:

Copperhead Water Heater - Copperhead Water Heaters

AUD300

[cj88]

For land-based houses, as the price of solar panels dropped it started to make sense to just install extra panels to power an electric hot water heater instead of installing a solar water heater. For boats with limited space for solar panels, some form of solar water heater can make more sense when you look at your total energy needs.

Heating water takes power and not everyone has the spare electric capacity. The reason I quite like what Custom Marine Products has done and also I see Green Yachting has done with a heat exchanger mounted to the rear of the solar panel is that their approach doesn't take up more space and can even improve the solar panel efficiency at the same time by cooling the panel and leaves all the available electric power for other needs.

Of course, you could always run the solar hot water through an electric water heater as well, with the electric used to top up the temperature if required thus reducing the power consumed by it or it could even act as a load dump if excess power is being generated by a wind generator, solar, etc.

[coopec43]

Originally Posted by TassieBloke

Just be done with it using this:

Copperhead Water Heater - Copperhead Water Heaters

AUD300

You haven't mentioned solar panels!! (You don't sell snake oil by any chance?)


Clive

[TassieBloke]

Originally Posted by coopec43

You haven't mentioned solar panels!! (You don't sell snake oil by any chance?)


Clive

Nope, no snake oil, just live Bunyips. Caught one just last night at Bunyip itself

[RaymondR]

Originally Posted by TassieBloke

Just be done with it using this:

Copperhead Water Heater - Copperhead Water Heaters

AUD300

More bloody electrical stuff when life is already a battle to keep the expensive batteries charged.

I figure on less than $100 and almost zero running cost for the direct solar plus I enjoy making things and am extremely gratified when my DIY stuff works.

[Uncle Bob]

Originally Posted by Uncle Bob

Have to say, this, https://www.custommarineproducts.com...ng-system.html looks really interesting, double the function with no real estate loss.

Have to say, just back from the boat on the mooring where it is 30 deg C today and the back of the solar panels were not hot at all,warm but not hot, I fear that this system may not be all that productive.

[coopec43]

Originally Posted by Uncle Bob

Have to say, just back from the boat on the mooring where it is 30 deg C today and the back of the solar panels were not hot at all,warm but not hot, I fear that this system may not be all that productive.

I guess if the back of the solar cell was ventilated well it would not get hot. Maybe it has to be installed in a certain way? Maybe?


Clive

[Milko Berben]

To all people who are considering to make something with black tube please find out if that particular pipe doesn't give of bad chemicals when being heated. like black tyleen pipe which normally used underground.

[coopec43]

Originally Posted by Milko Berben

To all people who are considering to make something with black tube please find out if that particular pipe doesn't give of bad chemicals when being heated. like black tyleen pipe which normally used underground.

Good point. And is it suitable for hotter water? (I only contemplated using it in the bathroom but....? Exposure to chemicals occurs when we breathe, eat or touch soil, water, food or air that contains chemicals.)


Is PE pipe suitable for potable water applications?
Polyethylene pipeline systems have been used by our customers for drinking water supply since their introduction in the 1950s. The plastics industry has taken great responsibility in ensuring that the products used do not adversely affect water quality.

https://www.pe100plus.com/PE-Pipes/T...ions-i250.html

And while we are on the subject of potable water never drink from a garden hose and don't fill your dog's water bowl via the garden hose because it may give your dog brain damage.

Before taking another drink, consider investing in a chemical-free, drinking-water-safe option. The vast majority of garden hoses are made of polyvinyl chloride (PVC), which contains harmful lead that leeches into water in levels deemed unsafe to drink.

Clive

[cj88]

Originally Posted by coopec43

I guess if the back of the solar cell was ventilated well it would not get hot. Maybe it has to be installed in a certain way? Maybe?


Clive

The area between the heat exchanger tubes is filled in and then attached to the back of the panel with silicone to create a flat surface to better transfer the heat. It is then backed with two layers of Reflectix style insulation and covered with corrugated plastic sheet. Foam pipe insulation is also used to retain as much heat as possible. They claim it drops the temp of the solar panel by at least 20 degrees F and warms the water from 60 to 105 degrees F on a sunny day. Wind and clouds will reduce efficiency.

[FlyingScot]

Originally Posted by coopec43

I guess if the back of the solar cell was ventilated well it would not get hot. Maybe it has to be installed in a certain way? Maybe?


Clive

My 4 panels (LG Neon 360w) are very well ventilated. Hung over the dinghy, stern into the wind (10-12kts) right now at a dock. Putting out about half rating the back side of the panels were between 46-48C just now in Curacao. I'm guessing they get hotter when putting out closer to full rating. Used a Fluke mini IR thermometer for measurements. I checked multiple spots per panel and they were within .5C.

[noelex 77]

Solar photoelectric performance decreases reasonably significantly with temperature. Typically, power drops around 1% for each 3 °C rise in cell temperature.

Solar cell temperatures are often over 50°C in warm, sunny conditions even with well ventilated rigid panels. So there is a reasonably significant performance gain if this could be cooled with water.

There is a lot of appeal using freshwater to cool the solar panels and perhaps at the same time creating hot fresh water. It removes the space issue, which is the fundamental drawback of solar water heating on a boat.

In the deck areas that receive good sunlight, solar hot water can be installed, but this reduces the area available for photoelectric panels. If the same space could be used to generate electricity and hot water at the same time it would be ideal. If the system for collecting hot water increases the efficiency of the photoelectric panels it is a very attractive combination.

However, there are significant practical problems. Mainly if we cool the solar panels significantly, the water is too cold for showering. Perhaps this is solvable with a hybrid system where cold water is preheated under the photoelectronic panels at the same time cooling the panels and is then passed to solar water heater that raises the temperature? However I suspect even if such a system works it is too complex to be practical.

A system that just cools the photoelectric panels, perhaps with seawater, is more feasible and commercial units have been produced to do this, but that does not solve the hot water problem.

[senormechanico]

If salt water cooling gave enough extra solar output to reduce or eliminate the amp hours needed to run a hot water element it's in effect, free or almost free hot water.

The main advantage of using electricity to heat the water is, no problem with over temp.