Solar water heating?

Came across this lastnight on ebay:

http://www.ebay.ie/itm/Dernord…Sw1KxXNXjg

A 12v 600w DC immersion heater. I know you'd need <600w of solar panels to run it, but I thought it was a good idea that maybe worth adding to the Solar panel forum... MIght spark some ideas.

Your thoughts?

probably fabricating a "Willis" heater cylinder with the 12v element would be best for efficiency.
1 kilowatt element would produce a useful amount of hot water quite quickly, and over time it would produce and store it more efficiently than a direct immersion in the cylinder.
Only my thoughts.

Flipperdipper same here except our solar panels cost us €12k (after a lot of haggling!). That's a great price- think we were had. Though I must say the benefits of constant hot water for most of the year are great, especially with 3 small children who will be teenagers in no time.
Would love something similar for the motorhome (at a significantly cheaper cost obviously).

I setup an outside shower for Sunflowerfest a couple of years ago. 50 metres of blue piping spread out through one tonne of mulch. As the mulch rots it creates heat, we had to add a cold water tap as it got that hot. 3 months later and you could still shower in it, although not as hot.

Does anyone know of someone in Ireland who manufacture water heating solar panels?

Particularly the type below (not the more common vacuum glass type).

Used those in Spain when we were building the house and you could have made a cup of tea from it they were that hot, so again useless unless you wanted third degree burns

I built a small water heating solar panel for my leaving cert (construction studies) project back in 1988.
The following year, my dad and I scaled it up and made one for his place in Crosshaven. A simple set up. An 8ft X 4ft X 6inch box, painted black, with black 40mm wavin pipe snaked back and forth under a sheet of acrylic 'glass'. Simple as f*ck and not very pretty, but in the summer months, it supplied us with enough hot water for kitchen duties & showers. We HAD to fit a hot/cold mixer as the hot water would often get way too hot. It was a direct gravity fed system, meaning it only heated the water in the pipes and the volume of available water was limited to about 75 litres, all up on the roof of the bungalow. It was only good for a few hours during the warmest part of the day, but by 6pm, it's start cooling off. I'd like to fit an indirect system to the camper with an insulated storage tank that could be fitted down low in a cabinet and we could have solar heated hot water available after sundown. I could also plumb this indirect storage tank into the engine cooling circuit so that the water would be heated by the engine as we drove along.

Fitting something to the camper has aways been an idea floating around in the back of my mind, I'll get to it eventually!

I like the look of the panels above (in post #9). They look sharp. Very pricey though.

Completely implausible I'm afraid. Not unless you are talking about heating more than a cup of water. Lets assume you have two 100Ah batteries, you want to heat 20 litres of water, and you have a 12V 600W heating element.

Well if my math is correct,

Power required to raise temperature of 20L water from 15 to 60 degrees = (4.2 * 20 * 45)/3600 = 0.9333 kWh

Time needed to heat the water with 600W element = 0.9333/0.6 = 93 minutes

Available battery power = 2 * 100 * 12 = 2.4kWh

Available battery capacity after heating water = (1- (0.9333/2.4) * 100%) = 61% state of charge

You would be discharging your batteries close to the 50% limit. It would take over 9 hours of perfectly performing solar power to replenish that, which is impossible. More likely it would take 3 to 4 days in summer.

I have solar tubes on my sunroom roof and it is made up of 20 1.5 metres long evacuated tubes (vacuum inside) linked to a pump and insulated water tank. It is specially designed and placed to maximise efficiency and yet I wouldn’t rely on it to heat my water on a cloudy day.

My father has a big array of pv panels on a shed that pass any excess power to a heating element in an insulated tank for domestic hot water. The panel area would cover about 40 Motorhomes and it still needs a very sunny day with little power elsewhere being used to heat the water.

You should keep some of these ideas to yourself Martin. Now off to the patent office with yourself!

Lad's...Life is too short. Just flick the switch on the already fitted gas heating system and hey presto....Hot water... job done!

This time next year Rodney! If you do Dave give me your address so I can send the begging letters

John. don't be a spoil sport even big children must play
As said
( it's fun trying to be green and efficient and you never know we might get something right and become millionaires )
I'll bet someone said what would we want a mobile phone for ,can't we just send a pigeon.

Seeing Bounders blog about heat exchangers takes me back to a time when grimey cafes where the only thing on the road and if you got a nice piece of fish or steak ,wrapped it up in tin foil and secured it on the top of the exhaust manifold. Down the road a few hours later you had a nice tea and freshly cooked fish.

But you wouldn't be able to do that if some bright spark didn't think of it instead of a potbelly stove.

Sorry Martin...Didn't mean to be a spoilsport I think you all are very inventive tbh....best of luck with the experiments!
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That's ok John. I know you'll love it if one one off us would be millionaire are successful.

And Robert. You needn't think we are going to put photos up,just so you can sneak off and get the patent