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Old 02-01-2013, 12:45   #1
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Solar Hot Water

Currently building a solar water panel to heat hot water. It will be roughly the same size as my 3 85 watt solar PV panels 28"x 36". 3/4" manifolds, 7 (1/2") tubes conecting the upper and lower manifolds. Copper pipe and aluminum heat sinks, I would like to use glass for the collecter cover, but worry I might easily smash it. A drainback system, water reaches temp, 12v pump shuts off, and water drains out of collecter back to heat exchanger tank. Anyone have a solar water system?
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Old 02-01-2013, 13:11   #2
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Re: Solar Hot Water

Yes I do. It's that black plastic bag from chandlers. They actually work extremely well.

I blu tack closed half the holes to reduce water consumption. But in the tropics it's hot in 3 hours and if you don't time it right its too hot!

I run the novel and hose into the aft head. The bag sits on deck.
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Old 02-01-2013, 13:29   #3
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Re: Solar Hot Water

Yea I got that as well, but I'm in need of somthing more complex, and I've busted a bag or two. I think the copper collecter will outlast a few shower bags. Plus I NEED to be building/modifing something or i go crazy. I don't do KISS. I'm on a mission to make boat showering more like home. and why not I have all the free time in the world to work it out. I only wish i had this 5 gallon stainless beer tank thats sitting in my shop 2000 mile away. Some people have bigger problems I guess.
Solar water systems anyone?
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Old 02-01-2013, 14:27   #4
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Re: Solar Hot Water

Subscribed.

Pictures?

I use the pump-up version from Duckworks, but have considered a "real" system. I have huge surface area to use for this purpose.
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Old 02-01-2013, 14:28   #5
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Re: Solar Hot Water

I built a system that rolled up and went into the laz when not in use it was black (and white on the bottom) pvc sandwiching about 150ft of 5/8 soft tubing it is about 5ft long by 6inches when rolled (it is 5ft by 4ft, it has a 20watt solar panel and tiny 12volt pump to circulate the water, it plumbs into the hot water tank with 2 slip fittings. It takes about 3-4 hours to heat 11gals to 45C. It takes 5 minutes to setup and disassemble. I looked at a vacuum tube permanent mounted system but needed the space for another solar panel. I like the system and have sold the previous 2 as I refined it, the first one was 5ft by 2 feet and is working well in the South Pac. I just drape it over the boom and use it as a bit of a boom tent over the deck house. It doesn’t work so well on a passage, but could be deployed over the deck house. I’m amazed that black bags are all that is out there, but they do work well. A friend has a black painted 12gal keg on his foredeck permanently mounted that works great in the tropics. I built my system to use the laz mounted 10 gal hot water tank.
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Old 02-01-2013, 15:20   #6
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Re: Solar Hot Water

pretty cool project, but what about the weight of the panel and water. Will this be deck mounted or hung on a bimini?

I always liked the bug/weed chemical sprayer idea. Built in pump and the spray nozzle is adjustable, but I would still mount a regular shower head to it. Also, you can add water from a kettle if you need to shower without sunlight.
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Old 02-01-2013, 15:31   #7
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Re: Solar Hot Water



This is one method that is used in many styles of solar water heaters.

I would think that just having a 1/2" black PEX pipe with a small 12V water pump pushing water through it for a few hours when it was sunny would heat up a tank of water as well, if the air temp is above 50F (10C).
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Old 02-01-2013, 15:40   #8
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Re: Solar Hot Water

I've been considering a possible modification to one of my solar panels for some time. I am considering using some aluminum radiant floor heating panels mounted to the bottom of one of my PV units with heat sink compound (I need to find a cheap source for heat sink compound) and covering the back with spray urethane foam. I haven't decided whether to use copper or aluminum tubing in the panel but would plumb it into the heating coil in my hot water heater that comes from my starboard engine. My solar panels get very hot in the tropics and would gain a bit of efficiency by being cooled. I'd use a small 12v circulating pump on with a temperature differential controller. I currently get plenty of hot water when motoring, but miss it at anchor.
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Old 02-01-2013, 15:55   #9
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Re: Solar Hot Water

No bimini here, pilot house with 3 PV panels. The weight of the heat exchanger tank will be very low in the hull next to the waste tank under the rear bunk. The weight is not really a concern as I added 1000lbs and 1' draft to the keel this summer to counter the pilot house. I solderd the copper collecter this morning (plenty of jet ski traffic to hone my skills) and will post a pic soon.
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Old 02-01-2013, 17:28   #10
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Re: Solar Hot Water

Quote:
Originally Posted by Captain Bill View Post
I've been considering a possible modification to one of my solar panels for some time. I am considering using some aluminum radiant floor heating panels mounted to the bottom of one of my PV units with heat sink compound (I need to find a cheap source for heat sink compound) and covering the back with spray urethane foam. I haven't decided whether to use copper or aluminum tubing in the panel but would plumb it into the heating coil in my hot water heater that comes from my starboard engine. My solar panels get very hot in the tropics and would gain a bit of efficiency by being cooled. I'd use a small 12v circulating pump on with a temperature differential controller. I currently get plenty of hot water when motoring, but miss it at anchor.
I had this idea too, and was wondering why no commercial PV panels are setup to do this.

The only thing I would worry about is if you insulated it too much and had enough hot water to switch off the pump that the panel would get even hotter than normal.
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Old 02-01-2013, 17:39   #11
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Re: Solar Hot Water

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Originally Posted by SunDevil View Post
I had this idea too, and was wondering why no commercial PV panels are setup to do this.

The only thing I would worry about is if you insulated it too much and had enough hot water to switch off the pump that the panel would get even hotter than normal.
Actually there are such panels made in Turkey, but I have not seen them in the states. They're called hybrid panels and their combined thermal/PV efficiency is over 90%. The thermal is actually a lttle less efficient than a pure thermal flat plate because you loose about 15% of the energy to the PV.

You have a good point about overinsulating. Maybe I would need to consider a diverter valve. One of my concerns was controlling the flow of the coolant so that it did not go through the engine, but perhaps that is the answer. Once the water in the tank is hot enough divert the water/coolant through that big block of iron.
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Old 02-01-2013, 17:44   #12
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Re: Solar Hot Water

Even in Northtern countries like Holland people DIY Solar Collectors.

DIY Solar Boiler (Dutch website "Google Translate"

Many YouTube's about this subject
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Old 02-01-2013, 17:46   #13
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Re: Solar Hot Water

The 36" x 28" panel is a good size for the boat. Having contemplated solar hot water on a boat and designed a few for land side buildings, I would recommend sizing the headers for 1/2" and use several 1/4" branches on 6 to 8 inch centers. Or use two or three loops of soft 1/4" tubing. The flow rate for such a small panel is low and, only need about a 1 gpm pump or even less. You might have laminar flow issues using such a relatively big header used with a small panel. Pipe it reverse return, in on one side, out the other.

Another option is to put a small copper / aluminum tank painted black under a glass top box on the cabin top.

Due to the temperatures possible heating solar hot water, glass is about the only way to go. You could go plexi-glass but would need to change out the glazing when it got too hazy.

I had also thought of using the underside of a PV panel and just put a aluminum backplate with 1/16" standoffs every 6" with a 4 pass design, that is the standoffs making a back and forth pattern. Then just connect two threaded nozzles to the plate, using one 220-240 watt panel with a 2/3 sized back plate attached with 5200.

The problem I see using a PV panel is the water mass could heat up under no flow conditions even hotter then normal, where it might adversely effect the PV panel. I think that a separate solar hot water panel / tank would be the way to go.
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Old 02-01-2013, 18:45   #14
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Re: Solar Hot Water

We are looking at installing Solar hot water and I know there are several boats in Australia that have one installed . As far as I know the panels are made by Products Look good. There was a write up about them in one of the Cruising Mags. The install was done by Nod at Multihull Solutions in Queensland and they where impressed with how well it worked. Only issue for us is the cost to ship the panels from the US to here is about $140 us, makes them expensive. We think we will still go that way as they look very sturdy and efficient.
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Old 02-01-2013, 21:10   #15
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Quote:
Originally Posted by funjohnson
I always liked the bug/weed chemical sprayer idea. Built in pump and the spray nozzle is adjustable, but I would still mount a regular shower head to it.ht.
http://www.duckworksbbs.com/gear/shower/index.htm

Done, works well.

But for a family of 5 a bigger solution is needed. I like the idea of this thread
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