Hot water, a thermal store we can’t ignore

9th Dec 2019


One of the drawbacks to an all-electric energy scenario is the need to match supply with demand. Now that is simpler when you can turn on and off supply quickly but with the challenge to meet Net Zero, and the UK’s increasing reliance upon wind power, the on-off switch is no guarantee.

We have become increasingly weather dependent, and our geography means we do have variable meteorological patterns. So we will experience wind power generation to be in excess of demand, sometimes, and have a shortfall, sometimes. Smoothing out this supply is key. With gas, pressure differentials and storage both allow this to happen.

In addition, converting surplus power, through electrolysis into hydrogen gas has a real future. But there are also other ways of storing energy, much closer to home.

The hot water cylinder has often been overlooked. Yes, combi-boilers have given access to instantaneous hot water but they aren’t the only solution to meeting a household's needs. Hot water storage can do this job too and utilise surplus electricity generated in the home (via solar thermal but increasingly through solar PV). Smart networks will also be able to achieve this for many in the future.

Although the technology isn’t new it does come with its challenges. Increasingly the problem is encouraging house-builders to create the space to fit them. Once there, then renewable and low carbon solutions can embrace the hot water cylinder.

So why the importance of hot water? Well, as we move to an increasingly more thermally efficient new build, the space heating load reduces from its current levels but our hot water demand remains constant. Hot water is often overlooked in the debate around Net Zero. Hot water cylinders can utilise renewable solar, renewable wind and yes, work with clean gas too. That versatility needs to be recognised. 


Best wishes

Mike Foster, CE