Solar Hot Water (SHW) Blog 2

The Tranquility System and how SHW can work

Tranquility is all but self sufficient in hot water with an annual bill below £10 for the gas used. But this is light years ahead of systems for sale.  White Paper 1 proved how little heat normal systems actually collect, and while here we will skim how T does it – it is well explained in White Paper 2 see Sorry about the length of the Paper but there is a lot to explain.

The golden Rules:

  • Catch everything you can as effectively as you can
  • Don’t lose what you fought hard to gain
  • Use the hot water wisely
  • Never assume that because you have a ‘solution’ it cannot be improved on.  Good solutions are often multi tiered
  • Consider other problems at the same time – the solution to one may help or hinder another

The system was developed for T – a new house.  But with 23M existing houses, all the development work here is for existing buildings.

We are also very short of water, so being water independent was another goal.  So there must be a substantial store of water – the main tank holds 15,600 litres.  But all the water must be potable (drinkable).  So the individual solutions were as follows:

  1. By locating this tank inside the perimeter of the house and at the right depth its temperature is perfect – as high as possible but not above 20°.  This provides 28% of the total heat required through the summer.
  2. Batch move the water from here to a 450 litre top loft tank where it gains another 2.5°.  Total heat supplied now 36% (in summer)
  3. Add a cylinder between the loft tank and the hot cylinder and passively solar heat it with a homemade hater which is inside the house. We are now already 73% of the way to hot water!  If the SHW plates don’t collect much it is probably sufficient to reach tap temperature and stop the boiler firing.
  4. Blend the water from the Hot Cylinder with water from the passive cylinder – which is already quite hot – to get to the 42° required.  There is now a lot of hot water.
  5. When the passive cylinder is too hot, blend instead with water from the loft tank.  This means the house can have about 1,600 litres of hot water with only 2 cylinders.
  6. Dump excess heat from the hot cylinder into the main underground tank so neither water nor heat is lost.
  7. Insulate the cylinder properly – see White Paper 2 where there is a document explaining how to do it.  Don’t just add more!


It has been shown that while existing SHW products don’t achieve much; certainly ‘don’t do what it says on the tin’,  and are not cost effective – superior and cost effective performance can be achieved.

Tranquility has a solution for existing houses that should achieve all the above but not in this way.