District heating isn’t really a new concept, but we have come a long way since the inefficient communal heating systems of the 1960s and 1970s. These were installed within uninsulated apartment blocks, and tended to be unmetered and uncontrollable by occupants, resulting in high wastage of energy and poor comfort conditions.
In contrast, a new breed of district heating schemes looks to lower energy use through high-efficiency centralised plant, well-insulated pipework distribution, and heat metering for each dwelling or commercial unit.
Systems can be powered by heat pumps, biomass or gas boilers, with combined heat and power (CHP) units also used. As we decarbonise towards Net Zero, heat generation choices are likely to shift towards heat pumps and possibly hydrogen.
District heating in urban areas
District heating is most often found in London and other major cities, since it is most suitable for higher-density developments. The use of communal and district heating schemes has been pushed by urban planners for a number of years, as a way of reducing energy usage and providing a greater carbon dioxide reduction, as well as providing future-proofing for future green technologies to replace existing gas/oil/biomass infrastructure.
Some London Boroughs have taken a leading role in setting up and expanding district heating schemes, and larger developments have had no choice but to embrace the inclusion of district heating schemes, often at large capital costs.
There are now more than 17,000 heat networks already in place in the UK, with almost half a million connections to them (mostly domestic customers).
Does it have any drawbacks?
With recent rapid changes in technology, energy prices and UK energy strategies, district heating systems have been particularly exposed. It takes a significant amount of time to plan, design and install large scale systems, so by the time a system is commissioned it may not be as suitable as it had been during the design stages.
The decarbonisation of the national electricity infrastructure has also completely changed the required approach to heating systems, impacting everything from the fuels used, indoor/outdoor plant requirements, heating flow temperatures, choice of room heat emitters and more.
District heating schemes that relied on biomass or gas fired combined heat and power (CHP) with high water temperatures are now completely at odds with the current thinking, and it would be something of a struggle to convert current networks to suit low-temperature heating (such as heat pump systems).
There are also challenges around cost and fairness. Heat metering is necessary to create accurate billing for district heating, and our experience is that there are regular problems with heat meters in terms of poor installation, inaccuracies, and a significant failure rate due to poor quality manufacturing of the units. Also, some heat meters have been installed in inaccessible locations such as ceiling voids or locked riser cupboards, making it difficult for occupants to monitor their own energy usage and budget for bills accordingly.
Additionally, the administration costs of operating communal and district heating systems has always been a concern, with charges for metering and billing in some cases exceeding the actual energy costs. Some schemes that were promoted as being highly energy efficient, and therefore expected to have low energy bills, are still having high bills.
On a related note, communal heating systems are not protected by the energy price cap, as Ofgem classifies heat networks as a commercial, not domestic, arrangement. The Government announced on 21st September 2022 that commercial heat would be capped for six months under the new Energy Bill Relief Scheme, but we’re now waiting for details of what happens when this expires.
Is district heating the right choice?
We have become so good at reducing energy usage – through increasingly rigorous Building Regulations and Planning requirements – that on balance district heating may not offer the same weight of benefit it once did. The increases in building insulation and air tightness, coupled with other technologies such as waste-water heat recovery, mechanical ventilation with heat recovery (MVHR) and water saving fittings, have resulted in an increasingly smaller and smaller heat demand per dwelling.
There has to be a point at which the additional capital cost, embodied carbon of plant and materials, and maintenance costs outweigh the potential benefits of a district heating system. When a typical flat can be heated with 2 kW of direct electric heating, and a 3 kW electric immersion for hot water, should we really be using a lot of raw materials to create a large heating network?
District heating: future plans
Overall, we feel that the introduction of low-temperature heating networks within buildings is a sensible idea. However, the amount of heat needed for new-build schemes is so small that the embodied carbon of a communal system should be reviewed before final decisions are made. Any installed communal system also needs to be flexible and future proofed, to respond rapidly to changes in energy prices and policy.
Of course, it may now be difficult to get developers and consumers fully on board with the higher costs associated with district heating, when it is very obvious that mistakes in district heating policies historically have created more problems than they have solved.
To find out more about evaluating the suitability of all types of heating system, including district heating, call us on 01206 266755 or email firstname.lastname@example.org.