Homes that already have a hot water storage cylinder provide heating engineers with an opportunity for talking to the owner about upgrading and future-proofing their heating system. A smart cylinder, such as a Mixergy smart hot water cylinder, which has been validated by Energy Saving Trust to be up to 21% more efficient than a conventional cylinder, can save money on energy bills straightaway, as well as being ready for use with new technologies in the future.
As the UK’s environmental goals require us to move from gas to heat out homes, which can deliver up to 65kW of thermal power, to electric, which can deliver around 18kW – approximately a quarter of the instant power we are used to – stored hot water will be the only way of achieving a quick-running bath or shower. This is true whether the plan is to install a heat pump, solar PV or electric storage heaters.
After the heating engineer has carried out a home’s heat loss calculations, checked there are no microbore pipes and ensured the existing radiators would be adequate, they may suggest to the homeowner that a heat pump could be appropriate for them in the future. If a smart hot water cylinder is installed now, it could easily be converted to work with a heat pump in the future by retrofitting a plate heat exchanger. This would achieve the highest heat transfer performance to improve the coefficient of performance (COP) by as much as 10% when compared to a high surface area coil.
Alternatively, for homes that have poor fabric and may not be suitable for a heat pump installation, solar PV, with radiant heating and fabric improvements, could be a consideration. In this case, the smart hot water cylinder can be simply retrofitted with a PV diverter which would allow the provision of free hot water whenever there is surplus solar energy from the PV installation. This is a great alternative to a home battery system which would otherwise cost several thousand pounds or more.
When connected with solar PV, the Mixergy smart cylinder uses thermal stratification. Simply put, thermal stratification is the result of heat rising; hot air rises above cooler air and hot water floats on top of cooler water. This means that, unlike most cylinders that have a coil at the bottom and heat up the whole tank of water, this cylinder starts by heating a small volume of water at the top of the cylinder and then growing that volume downwards. Consequently, the cylinder only heats the water needed, reducing heat losses, and gets to the set temperature more quickly. And there’s more space to accommodate surplus solar energy from the property’s solar PV system.
Smart hot water cylinders also have an important role to play as flexible electricity tariffs become more available as the latest generation of smart meters is rolled out. Second generation smart meters will allow energy suppliers to operate real-time dynamic pricing, which means they can turn on the hot water whenever there’s a surplus of wind, solar or nuclear power. Thermal stratification means there’s more space in the smart cylinder to take advantage of this economical hot water.
Finally, a brief word on training for heating engineers of the future. It is well-publicised that if we are to meet the government’s targets for installing renewable heating systems in our homes, we need many more appropriately qualified installers. I would therefore encourage qualified gas engineers to get their Part P and 18th Edition Wiring qualifications, which will help with heat pump installations and smart technology. Other qualifications, such as MCS and Unvented G3, will give them much more flexibility and help them to play a crucial role in preparing their customers for the future.