Put the Sun to work

  • Put the Sun to work
  • Put the Sun to work
  • Put the Sun to work
Date:31 March 2006 Tags:

Are you tired of paying lip service to renewable energy? Then build your own solar hot-water system, and stop feeling guilty

AS MILLIONS of Capetonians will attest, there’s only so much electricity to go around. When grid power is interrupted for whatever reason – perhaps as a result of huge urban growth, or when a stray bolt falls into a nuclear reactor – things start falling apart, sometimes literally.

At times like this, the most unlikely people speak darkly of an imminent breakdown in society, start hoarding cans of baked beans, and speculate on the practicality of a cabin in the woods powered by solar energy and biological waste.

Okay, we’re not suggesting that every South African could or should immediately abandon the Eskom grid, switch to renewable energy and take up useful hobbies such as home brewing and basket-weaving (although the idea is rather compelling). What we’re saying is that just about anyone can build and install a small solar water-heating unit. It won’t solve the energy crisis, to be sure, but it will certainly save you money in the long term (your electricity bills will go down dramatically) – and the sense of satisfaction is indescribable.

Save energy, save money
Even the more expensive solar waterheating systems make sense when you consider that, from the moment you install the system, you start saving energy – and therefore money. Depending on usage, the break-even point could come a lot sooner than you think. More good news: you don’t need the expensive version. With some knowledge of woodwork and brazing, you can make your own collector panel and connect it to a hot-water cylinder (or “geyser”, in South African parlance). You’re not bound by too many rules, either. If you prefer, you can substitute black plastic tubing for the copper piping. See what materials are available at your local hardware store, check your budget, and plan accordingly.

Before you begin, you need to take note of a few points:

  • If you use a galvanised iron backing plate, remember that copper and galvanised iron will corrode where they touch (after all, we’re talking about a damp and hot environment). To prevent this, insulate the two surfaces with thick coatings of black paint or apply plumber’s tape to areas where the metals are in contact.
  • Solar geysers are a little different from “normal” geysers, and more expensive. Contact your local supplier for details. It is possible to modify your existing geyser, but don’t attempt this unless you really know what you’re doing. Ask your local supplier if your panel will work with a high-pressure geyser (you may need to adjust the way in which you braze or solder the joints).
  • Install the solar collector panel as close as possible to the geyser; this way you won’t need a water pump. The top of the panel should be at least 600 mm below the bottom of the geyser to take advantage of the thermo-syphon effect (hot water rising and initiating circulation).
  • For southern Africa, the collector panel must face north, and be oriented at an angle of 35 to 45.

You will need…
>> 2,2 m of 22 mm-diameter copper piping
>> 10 m of 15 mm-diameter copper piping
>> Drill with 16 mm hole saw (available from your local hardware store)
>> Brazing unit and brazing rods (ask a plumber or metalworker)
>> 2 lengths of wood 1 025 mm long by 100 mm wide by 22 mm thick
>> 2 lengths of wood 900 mm long by 100 mm wide by 22 mm thick
>> Dowels, screws or nails to make the wooden box
>> 1,2 m by 1,2 m of Masonite
>> Wood glue and panel pins (very thin nails)
>> 900 mm by 930 mm galvanised sheeting
>> 500 ml metal primer
>> 500 ml matt black paint (blackboard paint)
>> 4 brackets for the 15 mm piping
>> Rivet gun and 8 pop rivets
>> Insulation material (pink glass fibre or polystyrene foam)
>> 940 mm by 1 025 mm glass, 4 mm thick (or transparent plastic)
>> 8 glass clips
>> Silicone sealer
>> Copper-to-copper connectors (elbow joints) to connect solar panel to geyser

How it works
As the sun shines on the solar panel, it heats up the water in the copper pipes and pushes this water into the geyser. Your 1 m solar panel will need to be connected to a 150-litre solar/electric geyser (a geyser with additional connector pipes for the solar panel), which must be installed above your solar panel. Most homes have electric geysers only.

A new 200-litre solar water heater will cost about R6 000. If you’re planning to build a house, or tackling major alterations, now would be a good time to specify a solar/electric hot-water geyser. If six grand sounds like a lot of money (and it is), consider that the system should last for at least 15 years, which translates into 15 years of much smaller water-heating bills. You’ll be saving electricity, of course, and in so doing helping to reduce greenhouse-gas pollution (a by-product of generating electricity, and one of the causes of global warming). Ergo, you’ll feel good about yourself.

Here’s what to do
1. Cut the copper pipe to size. You need to cut it into two 1 100 mm by 22 mm lengths and eleven 900 mm by 15 mm lengths. Mark out 11 points on each length of 22 mm pipe, 75 mm apart. With the hole saw, drill 16 mm-diameter holes at these points. Make the framework (see Step 2). Join the eleven 16 mm pipes to the two 22 mm pipes by brazing the joins. If you don’t know how to braze copper, take the framework to your local plumber or metalworker and ask them to do it for you.

2. Your framework will look like this. Now make the timber box, basing it on the size of the copper pipe framework. Make sure there is enough space to insert the pipes. Join the corners of the box using dowels, nails or screws. Drill four holes in the box to allow the two 22 mm-diameter pipes to protrude beyond the box on either side (these will eventually be joined to your geyser). Fasten the masonite to the back of the box, using wood glue and panel pins.

3. Paint the copper pipes and the galvanised backing sheet with primer. When it has dried (about half an hour), paint thickly with the black paint so that it absorbs more heat.
4. Place the copper frame on the galvanised backing. Mark where the holes need to be drilled for the pop rivets; attach one bracket near each corner of the framework. Cut and fit the insulation material into the box. Next, place the frame, attached to the backing, in the wooden box, on top of the insulation, inserting the 22 mm-diameter pipes through the four holes.

5. Cover the whole box with the glass or transparent plastic sheet (use the latter if you live in a hail-prone area). Use silicone sealer to seal the glass to the box. Fasten it with the glass clips.

6. Connect the pipes leading to your solar geyser with elbow joints (you may use plastic piping instead of copper). Ask the supplier of your solar/electric geyser for advice.

  • Technical advice: AGAMA Energy
  • For more information on renewable energy initiatives, contact SESSA (Solar Energy Society of South Africa on 012- 804 3435 (e-mail: ). Alternatively, visit Earthlife Africa on

Latest Issue :

May / June 2021