Reducing the Cost of Solar Thermal: Integrating a Novel Freeze Tolerance Approach with Flat Plate Solar Thermal Panels

Lead Participant: Aes Limited


The aim of the project is to integrate Soltropy’s patented freeze tolerance solution, developed for vacuum tube

solar thermal collectors, with AES Ltd’s (AES Solar) flat plate solar thermal collectors. This will help to

significantly reduce the installed cost of their solar thermal systems. Most solar thermal systems in the UK do

not run water directly through the collector panels as it can cause freeze damage. Instead they run an

antifreeze fluid through the collector which means that when a new solar thermal system is installed a perfectly

good tank is replaced by a new hot water tank with a heat exchanger. This can double the price of the installed

system due to the new tank and additional labour costs. A new tank is not required with Soltropy’s solution

which allows water to be used directly in the system. It works by using a compressible tube inside the copper

piping which takes up the expanded volume of the water if/when it freezes. The cost savings made from not

needing a new hot water cylinder and from the reduced installation time will lead to a steep reduction in the

installed cost of solar thermal systems

Lead Participant

Project Cost

Grant Offer

Aes Limited, FORRES £74,978 £ 52,485


Heriot-Watt University, United Kingdom £99,230
Soltropy Limited, GLASGOW £24,947 £ 17,463


10 25 50