Hot water from the sun

Dave

An interesting concept. I don't think that simply adding a hose to the top and bottom of a tank will move any water around, unless the hose is the heating element.

Hot water will always flow higher then cold water so perehaps you can try a two part system with a storage tank and a large surface area "heating element". If you have the storage tank placed higher then the heating element then the coldest water will flow down to the heating element - warm up and flow up. Something like residential solar hot water systems.

Are you hoping for this to be permanantly attached to the car or something that is set up when camping?

Good luck and keep experimenting.

R.

Hello Dave,
I had two black plastic water heaters years ago which had deeply corrugated surfaces. these would heat water efficiently provided the quantity was small. trying to maximise the amount of hot water by overfilling was not on because it took too long to heat so much water.
So to try and get technical without, many qualifications to support me, it seems obvious to me that the ratio of water quantity to surface area exposed to the sun is critical here. Obviously the more water in close contact with the heating effect of the sun (thro the black plastic) the better off we are going to be. I guess then that if we put the water into a long plastic tube of say 35mm diameter we are going to heat that water faster than if it is in a black plastic tank. So if it is practicable to use a pipe as a tank and get enough volume this way it could do the job.
If you have a container of water with piping from top to bottom as you describe you will get the water at the top heating up but that lower down will not until conduction within the container heats it all, even then the water at the top will always be hotter. The plastic pipe in your scheme will not allow convection to happen.
If you have a much longer pipe fixed as you describe and have a 'snail coil' which is situated below the whole tank then you will get a convection current thus: the heated(therefore lighter) water in thepipe will flow up to the top of the tank and the cooler(heavier) water from the tank will flow down to replace it. Bingo circulation.
If the tank is black too you will be collecting heat there as well.
I'm tempted to say that this will work better if the tank is tall rather than squat, but I"m getting a migrane thinking about it (which is camper-speak for I am not sure and have to give this some more thought).
Anyway thanks for the entertainment.
If you get water to boil and we meat some time a cuppa from the system would be great!
Cheers,
Camper.

A lay flat type tube would be the best bet to provide the largest surface area. The other option would be a coil of 12mm micro irrigation tube with a small 12V bilge tube pump to circulate the water. They use a similar system to heat swiming pools and you know how hot the water in a hose gets lying in the sun.

Trying to set up a convection current wouldnt be too sucessful as the water at the top would get hot and try to stay at the top of the container and the cool would settle to the bottom.

If you used the hose thing mount the pump so it _Affordable_Storage_Drawers.aspx water from the bottom of the container and emepties into the top which would encourage uniform heating of the water column. You could also substitute the plastic hose coil for a copper pipe that you could throw it in the fire when the sun wasn't out

A few years ago I had to do a quick copper repair job to my sisters hot water system........it has a solar system attached as well which consisted of a heap of black tubed matting that lay on the roof.

I reckon you could get hold of some of that and probably adapt it to whatever size u wanted pretty easily and of course be able to use the natural movement of hot water rises principle to circulate it into a holding tank.........maybe a mat that could be used on your roof rack??

Dave,

If there was a more efficient way to heat water, I believe it would be commercially available by now.

As good as anything mate, is the old gas burner. Heat a couple of kettles of water and add to cold water in a container until you get the desired temperature.

Of course, there is a more expensive alternatives such as the Coleman, or Primus gas heated water systems that also come with a shower attachment, or units that attach (permanently) to the vehicles engine cooling (heating) system.

Depends on how sophisticated you want to get and how much you are prepared to spend.

Me, I use the kettle method and a cheap battery operated shower unit immersed in a 20 litre rectangular container that you stand in. (SWMBO gets first shot usually and I use recirculated water which is still warm enough)

Your existing black plastic "solar" shower is also a practical alternative.
You could also add (gas) heated water to this container, to speed things up.

I think the biggest problem lies in the amount of energy required to heat water. If I remember my physics correctly, if you take 1kg of steel and 1kg of water it takes 14 times more energy to elevate the water temp by 1degree than it does to get the same result with the steel.
Back on the subject, I have seen a troopy with a mass of black hoses attached to the side just like a home solar system, nobody around to ask how well it worked though...

Good luck Dave- I like your thinking.
The only thing I would add at the risk of repetion is that any tube must basically rise throughout it's length or the water will probably not flow- assuming no pump.
Good luck.

I have a similar system to the sandman,we use a 10 litre galvanized bucket,fill it with water ,and then just drop it on the fire!Keep stirring until your water suits your temp preference,and bingo!Then we just drop the 12 volt shower system that we got from bbq's galore in the bucket.Ive rigged up a 3 meter peice of conduit into a circle and it fixes to the side of the caravan.The wife has put a shower curtain around it and it works great..If I can sneak in a photo while she's using it you'll see how it works.But at the end of the day it's a simple idea and does us fine.

an uncle of mine uses the 'hot/warm' water out of 3-4 solar showers.. and empties into one big black (sealable) drum (used as a storage drum when not n use hence it has 2x uses!) - that is presurrised via an air compressor which uses a standard outlet threaded into the top of the drum lid... pushes the hot water up a standard peice of hose line fitted with on/off tap and shabang.. hot shower.. works on very similar principles to a keg and magic box setup with the gas pressurising the keg.. except the beer is taken over the ice chiller to get cold...

I'm a plumber by trade and I've seen black poly pipes left in the sun under pressure explode due to the water inside superheating. I'd make sure any system tried was vented to atmosphere somewhere.

Hi again,
My calculations and those of three others, one a professor of engineering,( because I couldn't figure out where the decimal point went in the answer) is 5.194m for 5litres.
Which is about 1m per litre.
"Oow me 'ead"
Camper

PS you could heat water well by wrapping suitable tube around your lower radiator hose. With the tank plumbed as we have discussed. You would need to vent it as Pat says in case it boiled, which would be unlikely but still important to guard against.
You don't get heat unless you are driving, or a total environmental vandal.
Cheers,
Camper