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Right,

We were thinking about making one of these last year but never got off the ground. As this year is on the way and life is looking up its time to think again.

I want to make my own Solar Panel for hot water and need to make a heat exchanger as our cylinder has only one coil.
Does anyone have any links or info on the basic design?

Do standard soldered copper pipe joints stand up to the temps of the water/anti freeze mix?
I can make the heat exchanger at work from stainless, tig welded joints etc etc but could do with a basic design priciple to start.

I was thinking of the standard 15mm copper pipe, grid pattern inside insulated type box. Expansion vessel, high temp pump, heat exchanger supplying the hot taps.

Nick


Lets discuss

Hi Nick
Dont know how to link but there is a thread still active on DIY solar water heating that has links and info. Have a look think its what you want!

Hi Ruth,

Ive read that thread and all the links, Ill look at the Navitron forum for advice .

It seams the people of that forum all try to sell their own navitron products. I wanna make my own panel and heat exchanger!!!!

There's some stuff here for the design of shell / tube heat exchangers that might be helpful. It occurs to me that a "U" tube exchanger (it is covered) might be a simpler option than a classic design with passes. If you've got access to stainless steel you should have few problems with corrosion / errosion.

Ive finally managed to get some good info regarding homemade soalr panel and heat exchangers. Im going to speak to our head fabricator tmw re-HE.
Hopefully during the summer I can start the construction of the set-up and can update this thread as I go.

Eyes peeled people. This will be cheap to make btw. Looking at around £100 tops.

mr fairy here, my wife asked me to comment.
standard lead solder joints work fine, I'd also read that the temperature ranges were too high, but I cant see how this can be so, even if pressurised the water would boil at about 110 degrees, far short of solders melting point, we use the vacuum glass tubes in conjunction with soldered pipes with no problems.

keep the pipes small, less water to heat in the system, = faster response rate.

don't buy a fancy control unit, there's a guy on ebay does a curcuit board (ready wired) that you put in your own box, comes with instructions, and works fine, about £35.

dont forget the anti freeze MUST be food grade, car antifreeze is a killer, I also added loads of food colouring, so if it leaks I can easily see it.

the pressurised balloon system is also unnecessary, I've just got a big sauce pan with lid as a header tank, as long as it's the highest thing in the system it works fine.
it needs no ballcock feed, just fill it once with your antifreeze mix, I checked it regualarly at first, but it looses no fluid.

single panel radiators painted black will work as collectors, matt black not gloss, and use the back of the radiator? the big radiant ribs will give more surface area, box it in under glass or perspex.

that should help for now, feel free to ask for more specific info.


ooh I nearly forgot, all solar tanks use a lower coil to preheat the water, then top up with the boiler, if you make your coil so it fills the top half of the tank, you'll get half a tank of hot water, rather than a full tank of tepid water.

Depending on your set up, you might not need a heat exchanger.

You can use the thermosiphon effect, whereby any fluid (be it gas or liquid) will rise above another cooler fluid.

If your collecting tank is above the panel then the hot water in the panel will rise above any cold water and into the tank.

You want your hot inlet going into the bottom of your collecting tank and the outlet from the tank over-flowing back into the panel.

I did a little experiment a while ago and am waiting to move afore starting again.

Good luck!

JayBee wrote:Depending on your set up, you might not need a heat exchanger.

You can use the thermosiphon effect, whereby any fluid (be it gas or liquid) will rise above another cooler fluid.

If your collecting tank is above the panel then the hot water in the panel will rise above any cold water and into the tank.

You want your hot inlet going into the bottom of your collecting tank and the outlet from the tank over-flowing back into the panel.

I did a little experiment a while ago and am waiting to move afore starting again.

Good luck!

Thanks for the reply, as I said in my first post, my cylinder only has one coil so it isnt possible to get the solar hot to the bottom of the cylinder. Hence the heat exchanger which seems common practice.

Nick69 wrote:Thanks for the reply, as I said in my first post, my cylinder only has one coil so it isnt possible to get the solar hot to the bottom of the cylinder. Hence the heat exchanger which seems common practice.

I've used "cylinder connectors" to add pipes to copper tanks.

Have a look at http://bit.ly/aFA5Hd

If you don't feel up to the job, I am sure a plumber will do it quite cheaply.

Its not that but im not going to fill the solar system with usable water as you run the risk of freezing in the winter months. By keeping it seperate and adding Propylene Glycol, you avoid the unnessessary risk of freezing.

Nick69 wrote:Its not that but im not going to fill the solar system with usable water as you run the risk of freezing in the winter months. By keeping it seperate and adding Propylene Glycol, you avoid the unnessessary risk of freezing.

Ah, I understand.

Two alternatives.

a) In that case, if you are not going to use the panel in the winter, you could drain it.

b) Use your panel as a pre-heater. Freecycle a small cylinder or make something up. You can then have the anti-freeze in your panel. The smaller tank (with a diy coil) is heated by the panel. Water from this tank is then the water input for your main tank. Does that make sense? It's the system I intend using as I have PV panels and want an electric immersion heater as the dump circuit from my charge controller.

Just thought of a third alternative.

You could make a heat exchanger. The panel's output pipe is coiled around your tank's input pipe and then heavily lagged to trap the heat.

Yeah B is almost the same way a Solarsyphon is meant to be installed.

Hi Nick

Did you get this built and if so, how is it going?

I am thinking of building a similar system. I am thinking of using oil in the solar collector/HE system as it has a higher boil point.

Any thoughts

mamos