Has anyone diverted spare solar electricity to heat water?

[FullCircle]

Just wondered if anyone has some form of immersion heater arrangement which kicks in to put hot water in the system when the batteries are full/floating with the solar/wind generated electricity?

 

[HoratioHB]

Good question - we looked at it recently but as our heating element is AC and the Windythingy is DC the wiring would have to be changed every time we went on shore power. Also the element would take the power but not sure if it would heat up much. Me I'm just looking for a 1 Ohm resistor with heat sink to do the same job without setting the boat on fire.

 

[[2574]]

Nigel Calder refers to this idea in his bible. If the solar/wind regulator is a shunt dump type you can put the excess power to good use to the immersion heater - and he talks of connecting the 12v supply to the 240v element. However he goes on to say that there is little warming effect on the water due to insufficient ooomph! Not sure how helpful that is!

 

[starfire]

Unless you can find a 12v immersion heater, no chance.

Using the standard 240v immersion heater you would be putting in the grand total of 2 watts.

But, could investigate the units the refuse trucks & some vans use for heating water for hand washing ?

ah ! just before I post, a quick check on ebay finds this:-

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=180270059207

Might be worth investigating if you have lots of power spare.

 

[Saguday]

I wondered about this too and looked into it a while ago. I'm sure I once saw a tank in the US that had dual elements, one 12V one 120V. We have 230W of solar panels so once the batteries are topped up we could get a nice trickle of dunno 60-70W-ish into the tank on average. Enough to keep it topped up a while anyway.

Can't remember where I saw it though... I did find this one in Oz:

http://allfabsydney.trustpass.alibaba.co...ter_Heater.html

but it draws 300W which is too big for a boat really.

I'll dig through me old files and see if i can find it.

 

[FullCircle]

Thanks so far.
I have been pondering. You could use microbore piping to create a secondary circuit of indirect water. Heating element could be from a 12v Soldering iron. In fact, its possible to assemble a soldering iron in and then be able to get it out again to use it!
Other ways to do it would be to create an inductive loop straight around the small bore pipe, which would create heat.

Getting completely carried away, you could also create a solar water circuit, assisted by the 12v power dump from the solar panel/wind generator excess.

What has Calder done on his latest machine?

 

[Deleted member 478]

Erm, those black-bag type solar showers work really well. I've had to add cold water on the odd occassion just so that I don't scold my delicates, you understand. And they are much, much cheaper than a 12v soldering iron - circa £12 each IIRC (from a caravan or camping shop) and they don't need complicated electrickery to make them work.

 

[Gwylan]

You may as well try a heat exchanger to recover heat from your wee!
Solar shower bags are €3,00 in our local £ shop in the Netherlands - looks a snip compared with solar cells

 

[Abigail]

We also use jerry cans, a 12v pump and a length of hose and grden spray on deck as a freshwater shower. Gets very warm in the sun. The pump just gets it out quicker and makes a nice spray!

Why go the long way round? (depending where you are)

 

[jeremyshaw]

I too have pondered this one.

The best discussion I came across is here:
http://www.reuk.co.uk/200W-12V-Immersion-Heater.htm

But when you do the maths it's a bit disappointing.
1 British Thermal Unit is the heat required to raise 1lb of water through 1 degree F

1 British Thermal Unit = 0.252k calories = 17.5 watt minutes.

Looks to me like you'd need an awful lot of surplus power to make an appreciable difference.

 

[grumpygit]

Hi, You can always use an inverter and maintain you 230v heater. Ohms law will still apply and you will have the same power consumption on your 12v system. No magic solution for this one I am afraid.

You do not get "owt f' nowt" when looking for power. /forums/images/graemlins/wink.gif

 

[CPD]

Jim, A Bavaria 40 I did a transatlantic in in 05 had this arrangement fed from a duogen. There were severe problems with the duogen itself so the "water warming" characteristics were never tried, but the general essence was supposed to be exactly that which you describe. To me the theory is sound.

 

[mandlmaunder]

We now leave a 5 gallon water jug in the sun all day and have free hot water.
Sounds simple and is!!
If we were to need more water we'd leave more jugs in the sun, still free.
Just a point , we can both shower using less than 4 pints(2lt).
We now also have a large awning/water catcher up and are water independant now.

 

[lenseman]

You will find this web-site interesting as they supply 12volt immersion heaters.

I have been looking into this as a means of getting rid of the electricity supply companies stranglehold on the energy market.

http://www.reuk.co.uk/200W-12V-Immersion-Heater.htm

And before you go ahead and purchase the one with the largest wattage, the following info was taken from their web-site:

A 100 watt immersion will heat 1 Litre of water 1 degree C in 1 minute and draws just over 8 Amps.

A 400 watt immersion will heat 1 Litre of water 4 degrees C in 1 minute and draws approx 35 Amps.

A 600 watt immersion will heat 1 Litre of water 6 degrees C in 1 minute and draws around 50 Amps.

ps: I thought I would do a Lakesailor whilst he was away with his 3-wheeled competition winner looking for a steep hill with road cones at the bottom! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[MASH]

[ QUOTE ]
A 100 watt immersion will heat 1 Litre of water 1 degree C in 1 minute and draws just over 8 Amps.


[/ QUOTE ]

So to raise a measly 10l of water by 30' you'd need 300 minutes - 5 hrs - at 8A!!!

This is a perfect example of why photovoltaics are all but useless for anything except trickle charging batteries. They are usually just too big and expensive to produce helpful amounts of power.

Who has 8A going spare for 7-8hrs realistically (for system losses?) If you were in that sort of sun you wouldn't be needing hot water, surely?

 

[lenseman]

I absolutely agree with you and that is why I edited my original post to include the Amperage required to drive the temperature of the water up. Glad to see there are other engineers on this forum. /forums/images/graemlins/grin.gif

The idea of using a 12 water heater to warm water is a concept which might be useful if you wanted a small amount of hot water.

Nominally, cold water 'from the mains' comes out of the tap at about 14ºC - 16ºC. I have designed a solar water heater which cost £100 and on a hot day in southern UK will raise a tankful of cold mains water up to 58ºC which is VERY HOT indeed! (The tank is a nominal 60cm x 40cm x 30cm which is 75 litres). On cloudy days, the temperature from 'mains' cold will rise to about 30ºC - 35ºC which is not to be sniffed at. You can comfortably wash in 35ºC and it is all FREE!!

The design has been successfully implemented and used in a school in Uganda and was originally designed around and built using recycle materials, Plastic, fizzy-soda bottles!.

I am fairly frugal but I still spend about £2.70 per day on electricity, anything which can be done to lessen the impact of the rinsing costs of electricity and gas is all for the better? /forums/images/graemlins/smile.gif

 

[Heckler]

Have just got my hands on an eberspacher handiwash, do a search in ebay on handiwash. Anyway have opened her up and basically it is a 12v element in a plastic tank, with all the control sensors etc, it has plastic taps on it BUT the element etc is removable so would make a good basis for a 12v immersion heater system, dump spare solar power to it etc etc.
owes me £25, if anyone wants it to experiment, its quite big and i suspect would cost a bit to post, pwllheli or llangollen or somewhere in between?
stu