Almost Free Solar Hot Water System.
This page is about a solar hot water system I installed in 2018. It provides us with free washing up water and free pre heated water for the kettle. Water is sent out from below the sink, through the wall and then through about 15 metres of black plastic tubes. The water stays in the tube and heats up during the morning. By 11am the temperature is around 35C (95 F) and later on the temperature can get up to over 45C. (115 F)
Black tubing strong enough to withstand house water pressure is very cheap and a system like this could be installed very easily by anyone with some basic plumbing skills. If you take the concept a little further you could extend the black tube and provide a lot more water for showers etc. My system is quite untidy but if someone lives in a more urban place you could make the tubes look more tidy.
I am not a very good TV presenter but I made made this video to explain the system.
There are subtitles in English, Spanish and French.
We are about to have a climate conference in Glasgow where the politicians will probably come up with inadequate solutions to avoid climate disaster. As an individual it is very frustrating but at least we can try to reduce our carbon emissions on a small scale in our personal lives and save some money.
Several years ago I started using black PVC tubes to heat water up with 100 metres of 16mm PVC tubing which adds water to our swimming pool every day. Black plastic tubing is very cheap and as long as you have some space to put the tube in the sun it is very easy. You see lots of complicated you tubes with coiled up tubing but if you don’t mind it being a little untidy you can let the tube just run over any surface.
We tend to have our main meal in the middle of the day which is normal in Spain so for months on end I use this hot water to do the washing up. It is also useful for preheating water for making tea. During the hours of strong sunlight I use a 900 watt electric kettle for boiling water and using pre heated water cuts down the boiling time considerably.
Some facts about black tubing:
In one metre of 32mm (1 inch) tubes there is 804cc of water.
In perfect conditions a 1 metre length of tube perpendicular to the sun would receive around 40 watts of energy.
In Spain 100 metres of PVC tube that can withstand 10 bars of pressure costs around 100 euros.
This system has been running for over 3 years. At first my tube was not long enough and it did not completely fill the sink, so I extended it. As the tube gets hot it needs to be good quality 10 atmosphere tube.
To work out the length of the tube, you have to work out how much water the tube can hold. The best way to do this is to use a this online calculator. https://www.omnicalculator.com/construction/pipe-volume The formula is: pipe volume = π * (radius * radius) * length, where radius = inner diameter/2. Pi is 3.14 Asterisk means multiply.
If I were going to do this for a pool shower or for showers I would buy a 100 metre roll. In my pool heater set up I have 100 metres of 16mm tubing in the sun. Even with flowing water it heats the water up to around 45C. By the way: Tubes don’t hold the heat for very long. By 4 or 5pm the tubes will have cooled down.
In the winter I empty the tubes during January and February because the tubes might freeze during the night.