Flattening the supply profile: domestic heating and hot water

02 Dec 2019

A key challenge for meeting the UK’s net-zero target is the decarbonisation of Britain’s domestic space heating and hot water demand.

To help achieve this, a primary aim should to reduce the amount of energy required to satisfy this heating demand. There should therefore be a strengthened focus on constructing buildings to more ambitious specifications, and upgrading the thermal performance of existing building fabrics with deep retrofits.

Adherence to standards

Essential to demand reduction is the tightening of building standards and also importantly, the independent measurement of compliance to these standards during construction and operation. Continuing to construct buildings that may not meet future needs is unacceptable on many levels; not least that the cost of upgrading these in the future is likely to be more expensive than constructing to a more ambitious specification now.

Domestic gas demand

Reducing overall energy demand is vitally important, but the UKERC FlexiNET project has also highlighted how flattening the supply profile for domestic space heating and hot-water should be a greater focus of the research community, industry and policy makers.

In 2018, domestic gas demand (mostly space heating and hot water) was 35% (309 TWh) of the total gas demand for Britain (880 TWh) Domestic customers are connected to local gas grids, and the shape of the energy demand curve that these grids currently have to cope with helps to better evidence the starting point for decarbonising domestic heat.

Two significant points become clear from the research behind the briefing notes on local gas demand and the overnight linepack changes that help to accommodate these changes.

  1. The local gas grid and national transmission gas grid provide the largest fractions of within day flexibility to allow energy (gas and electricity) demand to flex throughout the day
  2. The regularity and scale of the 5am to 8am increase in demand on local gas grids through the heating season (October to March) is particularly notable (illustrated in Figure below – from briefing note)2.
The shape of space heating and hot water demand

The building fabric, heating technology, weather, time of year, day of the week and work-life patterns of the occupants influence when domestic heating and hot-water is needed. Due to many of these being somewhat coincident between different end-users, it is no surprise that we see the demand patterns on local gas grids shown in the Figure.

Costs of having a flexible system

If we assume that the transition to a low-carbon energy system brings additional requirements (and potentially greater costs) for within day flexibility of energy systems, we should be asking how much flexibility do we actually need, and how best to provide this?

In answer to the first issue on how much flexibility we need – this is an open research question that is impacted by the interaction between future energy supply and demand profiles. How can the retrofit of existing building fabrics reduce the spikiness of heat provision? How much demand profile flattening can we expect from changes in behaviour, changes in heating technology, thermal storage and changes in weather patterns?

We need to better understand the tools available to flatten the supply profile for domestic space heating and hot water demand, and their relative advantages and disadvantages.

Research and Innovation

Understanding these will help provide the evidence of different approaches to reaching a net-zero target by 2050, and requires more focus across a multi-disciplinary research community. Targeting research and innovation funding to flatten the supply profile for domestic space heating and hot water would seem to be a fruitful area over the next few years to enable wider energy system benefits.

Dr Grant Wilson was part of UKERC Phase 3 FlexiNET project, and is currently part of the Active Building Centre.