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gmctoyman

Lake Livingston, Texas

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Posted: 03/03/12 03:21pm Link  |  Print  |  Notify Moderator

I've seen where folks talk ov using excess solar capacity to heat water. How can you do it, is there a 12v element made that will fit RV water heaters ?


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skipnchar

Topeka or somewhere else

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Posted: 03/03/12 03:27pm Link  |  Print  |  Notify Moderator

Never tried it but it doesn't sound at all practical to me. HEAT is the most expensive thing you can use at 12 volts. It would NEVER compete with good old fast,low cost LP gas.


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robatthelake

Vancouver Island

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Posted: 03/03/12 03:43pm Link  |  Print  |  Notify Moderator

Over the Years I have seen all kinds of Homemade Water Heaters.
Most were just Black Garden Hoses coiled in such a manner that the Capiliary action of the heated (By The Sun) hose allowed the Water to collect in a Tank or Tub secured to the Roof rack of the RV.
The Tank Too was painted Black to absorb Heat. A Short Shower Hose fed the heated Water to a Stall outside the Rig or through the Bathroom Window.
I'm sure there were various ways to circulate the Water ,pumps,checkvalves Etc.
We just use a Solar Shower Bag that we bought at a Flea Market or Boating Store.
It hangs in a Tree or on the Ladder, for use at the End of the Day. Lays on the Ground during the Day to gather Heat. Holds about 3 Gallons of Water.


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naturist

Lynchburg, VA

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Posted: 03/03/12 04:16pm Link  |  Print  |  Notify Moderator

Running an AC, an electric heater, or an electric water heater on photovoltaic (solar) cells is not feasible. These draw so much power, it would require completely impractical arrays of PV cells. Solar hot water is much better done using the black hose trick to heat the water directly.

PV cells get at most 15% efficiency. You can buy a LOT of propane for the cost of solar cells needed to feed a 1500-2000 watt heater.

You can get way better efficiency, probably 80% or more, via black hose, for maybe $20.

* This post was edited 03/03/12 04:22pm by naturist *





nvreloader

Western Nevada

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Posted: 03/03/12 07:16pm Link  |  Print  |  Notify Moderator

Do posters really read and understand about what the OP is talking about?

gmctoyman wrote:

I've seen where folks talk of using excess solar capacity to heat water.


This would be a way of using this EXCESS power from the solar panels that would be other wise wasted during the summer months and could possibly be used during the winter time also, depending on the solar setup thay have.


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Fisherman

Angus, Ontario, Canada

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Posted: 03/03/12 07:44pm Link  |  Print  |  Notify Moderator

nvreloader wrote:

Do posters really read and understand about what the OP is talking about?

This would be a way of using this EXCESS power from the solar panels that would be other wise wasted during the summer months and could possibly be used during the winter time also, depending on the solar setup thay have.


Well you sit down and calculate how many amps it would take to heat water using solar power at 12V DC. At 120V AC, a 1500 watt element takes about 15 amps, at 12V DC, it would take about 150 amps. Now you figure out how many watts of solar panel is needed. That gives you an indication of why stick house electric water heaters use 240AC or you'd be running wire the size of a fire hose.

gmctoyman

Lake Livingston, Texas

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Posted: 03/03/12 07:49pm Link  |  Print  |  Notify Moderator

Thanks for the well meaning replys, but it seems that only one really understood the question. But I found what I needed to know Here

Thanks again

nvreloader

Western Nevada

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Posted: 03/03/12 08:16pm Link  |  Print  |  Notify Moderator

gmctoyman wrote:

Thanks for the well meaning replys, but it seems that only one really understood the question. But I found what I needed to know Here Thanks again


Dave,
Thank you for the info of this heater, just what I have been looking for.
Don

nvreloader

Western Nevada

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Posted: 03/03/12 09:22pm Link  |  Print  |  Notify Moderator

Fisherman wrote:

nvreloader wrote:

Do posters really read and understand about what the OP is talking about?
This would be a way of using this EXCESS power from the solar panels that would be other wise wasted during the summer months and could possibly be used during the winter time also, depending on the solar setup thay have.


Well you sit down and calculate how many amps it would take to heat water using solar power at 12V DC. At 120V AC, a 1500 watt element takes about 15 amps, at 12V DC, it would take about 150 amps. Now you figure out how many watts of solar panel is needed. That gives you an indication of why stick house electric water heaters use 240AC or you'd be running wire the size of a fire hose.


Fisherman,
I do believe that you missed this point, EXCESS POWER, in meaning, and just for talking and as a example,

I have a 900 watt solar setup on the RV's roof, it produces about 150 amps of power PER HOUR of sunlight, I use about 150A of power for that night/day useage.

I have 4 hours of good sunlight, which will produce about 600a of power from the panels. I only need to replaced the 150A used, this is done in the first hour of the solar panels working as they should.

150a minus from 600a total is 450a of power remaining, that is EXCESS POWER, Not being used for NOTHING, wasted, thrown away or how even you want to define it,etc,etc,etc.

But now, I have a heating element that fits my water heater, I can use this EXCESS POWER to heat the water (to whatever/some degree of temp), I don't really care, how many amps of power it takes, etc, I am using the EXCESS solar power that would not be used for anything else.

I AM USING THIS EXCESS SOLAR POWER in some way, instead of wasting it etc,etc,etc. This is all that matters, if this solar heater only raises the tempature 10* p/hr, that is 10* less of LPG power I would have used to heat the water, if I did not use the EXCESS SOLAR power being wasted.

I am NOT talking about being effiecent or anything else, only meaning I am using EXCESS power that would not be used, to obtain a better result that will lessen the amount of $$$ comning out of my pocket.
Tia,
Don

christopherglenn

Near Yosemite

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Posted: 03/03/12 11:36pm Link  |  Print  |  Notify Moderator

A inverter and transfer switch / controler may end up being easier. push the electric element at full power off the inverter for 30 seconds at a time, then shut down till the batteries are full again. repeat.


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