7 Oct 2021
For many years now, the main aim of government energy policy in the built environment has been to drive down demand; a simple strategy for cutting carbon that continues to make good sense, although with increasing wind and solar power supplying the UK, things are no longer quite so straightforward.
Alongside the overall amount of heating energy a building uses, the timing and size of the peak load is also important as this affects grid level carbon emissions, which increasingly follow the peaks and troughs of the renewable energy supply. Our renewable energy story is a good one, with it making up about 43% of the UK’s electricity in 2020.
It does however result in a more variable grid carbon intensity, that can fluctuate by over 50% across a winter’s day. So, it makes sense to try and shift a building’s energy demand away from periods of high carbon intensity i.e. when fossil fuels are needed to meet a short fall in renewable power.
This is the goal of Active Buildings; a new term to describe buildings that intelligently control the way power is used to support the energy network. Central to an Active Building is the use of smart-controls and some form of electrical and/or thermal storage, used to better align building energy demand with periods of lower grid carbon intensity.
One means of providing a simple, low cost thermal storage is to exploit the thermal mass in medium and heavyweight concrete buildings. How does this work? Basically, smart controls are used to monitor the grid carbon intensity and/or price (the two are closely linked) and in response, control the space heating system accordingly. If necessary, the heating load can be brought forward or delayed.
This is made possible by the buffering effect of thermal mass, which absorbs and releases heat slowly, meaning internal comfort remains relatively constant even if the heating comes on earlier or later than usual, and that’s the key to this approach.
So, it is a win-win for both the UK energy network and building occupiers. This includes the domestic market, with homeowners now able to take advantage of cheaper electricity using half-hourly energy pricing.
The advent of the Active Building, which looks set to be a component of the next major SAP update (SAP 11), means thermal mass is more relevant than ever. It now has an important role to play in the heating season, alongside its established summertime role of reducing overheating and mechanical cooling loads.