The Naked Scientists

The Naked Scientists Forum

Author Topic: Just in case you missed it: A DIY thermal solar panel for under a hundred quid  (Read 8634 times)

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
« Last Edit: 06/05/2009 21:09:59 by Andrew K Fletcher »


 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Andrew...How much is 100 Quid in a american currency?
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Currently 150.69.
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Whoa! :o

You thinking of making one Chem? If you are let me know and I may be able to offer some advice. First advice is do not use the copper connections with the solder already inside, they are crap and more expensive than the plain copper joints.
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Karen, reckon I could have made it for 50.00 had I have had time to source the tubes and connections second hand. But the delay in saving on energy would have been counterproductive.

I would go so far as to say this baby is as efficient as the heavily over priced thermal solar panels. So if it rains, we get free rainwater and when the sun comes out we heat it for free :) We like free.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Whoa! :o

You thinking of making one Chem? If you are let me know and I may be able to offer some advice. First advice is do not use the copper connections with the solder already inside, they are crap and more expensive than the plain copper joints.
Well you've certainly got me thinking!
 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Karen, reckon I could have made it for 50.00 had I have had time to source the tubes and connections second hand. But the delay in saving on energy would have been counterproductive.

I would go so far as to say this baby is as efficient as the heavily over priced thermal solar panels. So if it rains, we get free rainwater and when the sun comes out we heat it for free :) We like free.

Me too..I want to build one and I also need to get measurements in inches etc, not metric...Lol..I am really bad at converting..lol ! I only have my phone again....not my computer intrnet...Money has been too tight for both so the phone it is!
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Measurements are totally flexible, depend mainly on the size of the corrugated tin sheet you decide to use. You can source all of the copper pipe and connections second hand from your local scrap yard or from the recycle centre. You will need to borrow if possible 2 copper pipe cutters a 15mm and a 22mm, or the type that relate to US pipes..

As you are using this system for domestic hot water rather than drinking water, I preferred to use 60/40 tin-lead solder as it is far easier to work with. Good flux is essential so you will need to source this by asking a plumber and tell him/her what type of flux you will be working with. You will also need some wire wool to clean the joints prior to soldering, even on new pipe this is advisable as saves lots of hassle later.
As I said before use only the cheep copper pipe connections / joints as these solder far easier than the type with the ring of solder inside them.

A canister blow lamp are inexpensive, and at a push you could even solder the joints on a gas cooker ring, or even a gas camping stove I have in the past. Anything to save a buck.

Our corrugated tin sheets are 7 feet x 4 feet so this was the size of my panel and works well.

The idea of using 15 mm tubing for the heat exchanger / radiator inside the cabinet is that it contains more water and compliments the combi boiler perfectly. The coil of black pipe doubles up as a heating source and also an expansion tank as the plastic becomes more supple when warm so can stretch to relieve the extra pressure. Although an expansion tank could be connected also and again can be obtained from a plumber who probably has a few of these second hand laying around and will be very interested in your DIY solar Panel.

The mat black stove paint cost around 3.40 and by spraying the copper tubes (after they have been pressure tested for leaks) on top of the corrugated sheet both sides, you will find you can just about cover the rest of parts of the sheet missed by the overspray. Alternatively, buy 2 cans as I am quite an experienced car refinisher :) The paint is essentially the most important part, so choose the right paint. Open fire stove paint is the best because it is thin and does not inhibit heat transfer and is readily available in most diy stores.


will paste this in the main thread also


 

Offline Karen W.

  • Moderator
  • Naked Science Forum GOD!
  • *****
  • Posts: 31653
  • Thanked: 5 times
  • "come fly with me"
    • View Profile
Thank you Andrew!
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Have posted a few more pictures in main thread to show how it was made.

Boiler switched off and sun not even shining through clouds yet :)

Thank you Andrew!
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Corrugated sheet         5.00
Lagging silver             2.00
Fittings       20.00
Pipes         55.00
Plastic connectors   6.70
Perspex      10.00
Black plastic pipe   10.00
Black spray paint   3.75
Miscl fittings               3.00
Pipe laggings      1.50

Total cost including external plumbing 116.90


Bump
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8670
  • Thanked: 42 times
    • View Profile
Does the thread's title refer to the ex VAT price?
:-)
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Does the thread's title refer to the ex VAT price?
:-)

Including vat from plumbers merchant at least, but seriously this simple panel is very efficient, the corrugated steel sheet is where it scores due to the amount of heat it absorbes when painted mat black. Not measured the temperature of the hot water but the water coming out of the tap is almost boiling. And Free from VAT considering it falls on my roof first :)
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8670
  • Thanked: 42 times
    • View Profile
It looks like a really useful system. I'm sure that I'm not the only one who would like to know how much water it heats and how hot it gets it.
 

lyner

  • Guest
AKF. Interesting, It's not clear how this fits in with the domestic system. You mention a combi boiler but those do not use an indirect system. If it is direct, what do you Do about storage of heat and about frost resistance?
« Last Edit: 13/05/2009 10:21:10 by sophiecentaur »
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
At present the contents of the coil of tube can hold sufficient water to fill the automatic washing machine using a jug. This saves the need for using electricity to heat the wash and pre wash. It takes 15 minutes to heat it to a temperature that will burn when touching the metal tap body. The washing machine holds 2.5 kettles of water, which contains 2.5 litres giving us 6.25 litres. A larger black plastic coil with a larger bore size could easily double the capacity of warmed / pre heated water entering the solar panel, But I favour adding an additional stainless steel 20 litre pressurised drinks canister to the top of the panel affording a storage sufficient for taking a shower.

During rare severe frost, simply closing the outside stopcock feed and running the tap will partially empty the panel affording an air pocket to allow for ice expansion. But I have to say, we have external plastic and copper pipe that has not frozen for many years and possibly about 4 or 5 times in 21 years.

If I have a problem, a burst pipe will be outside of the home so no major catastrophe will take place and because of my rainwater harvesting system the water would simply be returned to the main storage tank from the guttering. Net loss = a little more soldering perhaps and a little electricity used to pump the water back to the tank.

Considering also the possibility of installing an internal tank, but really like the pressure from either the mains or from the rainwater demand valve and pump.

Think anyone considering this would have to make sure their combi boiler is happy with preheated water as some of the older ones have a thermostatically controlled inflow. Also consider adding an expansion tank, this is a pressurised metal tank, usually fitted with a car tyre valve for pumping air into it. The idea is that as the water heats up the non return valve will prevent the pressure from equalising so that added tank would act the same as an expansion tank in a vehicle by providing a compressible air pocket.

A pressurised tanked system can be seen here: http://www.diydoctor.org.uk/projects/domestic_hot_water_systems.htm
 

lyner

  • Guest
I see. So is it not actually integrated into the domestic system?  Good effort and very satisfying to get a free shower but it seems that you need to do a bit more to make use of all the available Solar Energy on any particular day.
Most / all commercial systems are clearly a rip off but they all require a hot water tank. If it's an indirect system them you need a special (two coil) tank - upsetting!
There is a system which I found on the Web and which B&Q seemed to be offering recently.  It uses a direct system and a solar powered pump (you only need the pump to work during the day, so that seems ok) which feeds hot water into the TOP of your hot tank. The pump speed ensures that the water is a usable temperature by slowing the flow accordingly. The panels claim to be a bit special (don't they all) but something  home made would be so much cheaper that its poorer performance wouldn't matter.  The collector pipes have to be made of a flexible material to allow for freezing  because they carry fresh water - but that's a problem for your system anyway. As also is the problem of limescale, particularly as the panels use a small bore of pipe. They recommend a softener (chemical, not magnetic - in fact they make a point of saying that magnetic inhibitors should not be used). South Devon is not much of a worry in that direction, I shouldn't think, but Brighton definitely would be.
As I have a hot tank, that type of system seems more attractive.
Here's a picture of the system.  http://www.heavens-solar.com/solartwin.htm
I thought it was quite attractive. All I need is some flexible pipe for the heat exchanger and some effort.
 
 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Instead of cold water feeding the combi boiler, I have hot water feeding into the combi boiler, so it is a direct heating system, fully integrated and functional. The plastic coil of tubing on the felted roof acts as a primary heat source and an expansion tank, when the water heats up, the tubing becomes supple and expands a little to afford the pressure relief. However, going to fit an expansion tank also, again this extra expansion capacity from a freeze, might just prevent a fracture too. Indeed, we have mdp pipe fully exposed to the elements as I have mentioned before and it has never caused any problems, even when frozen, it remains water tight on thawing out.

Your system is ideal also, and you can have antifreeze in the panel rather than water, plus you will have sufficient water to provide your night time usage, so the bigger the tank in your case the better.

Before you fork out for a new tank make several trips to the local recycle / public disposal place. There they have lots of the fully lagged tanks, and if there were any leakage on them it would be fairly obvious. Last time I got one for free with a header tank sitting on top of it and a copper coil already inside. The tanks are very common as more people move to combiboilers throwing out perfectly good tanks

Might eventually go down that route, but for now enjoying the savings and finding the water much hotter than when the combi boiler is used. But would probably still go the direct route with an expansion tank fitted to the outlet. These tanks cost a little more, but from the tip the price will still be next to zero :)

Solar pump is a good move as would prevent the reversed heat transfer when the sun is hidden.

I think you might be in for a shock when you see just how efficient the corrugated sheet is when thermal lagging is applied to the back of the sheet. I am amazed. Also, using 22mm and 15mm copper tubing rather than microbore there is zero problem with lime scale.

The corrugated sheet is the key to this panel as the surface area is greater and the corrugations wrap around the 15mm juxtaposed vertical pipes maximising the heat transfer to the water inside the mat black copper pipes.

This type of stainless keg is ideal:
http://www.jimsbeerkit.co.uk/cornelius.htm

 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Water temperature from the DIY Solar Panel measured 75 degrees C at 1.30 pm outside temp in shade was 26.7

Even on a relatively dull day it compliments the combi boiler by reducing the gas consumption. Now have to wait and see how the electricity and gas bills alter compared to previous bills. As I mentioned before saving on electricity by filling washing machine with solar heated water and now installed mixer taps from Ebay for 50 including postage, should have been 345.00 "Don't ya just love Ebay :) "

Also purchased a shower head set complete with stainless rail and chrome plastic fittings at Lidle for 2.00 LOL but the thing about this shower head is it has a water saving device and a setting that introduces air into the spray saving around 25 % of the water and therefore an additional 25% of the gas consumption used to heat the water.

 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Ultimate test was performed today by my wife and I.

Yes, we both had our first thermal solar panel only shower and we had ample hot water. Now we really start saving money :)
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length