HEATING, VENTILATION & SERVICES 69


LOCAL SOLUTIONS FOR LOW-CARBON HEATING


Steve Richmond from Rehau Building Solutions looks at the key considerations when commissioning a district heating network – an key option to consider in the race to reduce carbon in residential developments.


T


hough the UK’s green transition will likely be ushered in by a multitude of technologies, district heating has emerged as one of the forerunners of a low-carbon nation. Recent schemes such as the £288m Green Heat Network Fund (GHNF) as part of the wider £338m Heat Network Transformation Programme (HNTP) have demonstrated government faith in the technology as a key method of achieving net zero. For this reason, many housing developers are beginning to explore the possibility of using district heating for their low-carbon housing projects. Here, it is important to examine the key considerations for integrating a district heating system into a low-carbon housing development in order to derive the maimum benefi t.


SUCCESSORS TO THE GAS BOILER There is much debate around which technology will succeed the traditional gas boiler come the introduction of the Future Homes Standard in 2025. Of these, heat pumps, district heating networks and hydrogen appear to be the most touted. However, it should be noted that with the latter currently early in its R&D phase, it won’t be available come the scheme’s


introduction, meaning it remains a long-term potential solution. For this reason, heat pumps and district heating networks remain the most sensible options. That said, many heat networks can make use of a large, centralised heat pump as a heat source, with the latest statistics from the Heat Networks Planning Database (HNPD) indicating that this is the case for over 70% of planned installations. Naturally, this means that the question is not of heat pumps versus heat networks, but individual heat pumps versus heat networks. This subject should therefore be broached on a project-by- project basis, with both technologies able to offer a wide variety of benefi ts. Initiatives such as the Boiler Upgrade Scheme (BUS) offer ample support for the uptake of domestic heat pumps, but do not extend to new build properties, unlike the GHNF. Regardless of which technology is opted for, it is critical that these alterna- tives are adopted sooner rather than later, ahead of the UK Government’s ambition to phase out all new purchases of gas boilers by 2035.


THE GENERATION GAME The fi rst thing to be aware of before


undertaking a district heating installation is the fundamental differences between each generation of this technology, as the applications and benefi ts can vary wildly depending on the system specifi ed. At present, most district heating networks installed in the UK are third generation, circulating water at 70-95°C with a gas combined heat and power (CHP) system usually as the source. While these systems still make use of fossil fuels, distributing heat from a singular energy centre proves more effi cient than heating homes individually resulting in carbon savings.


That said, the true potential for district heating networks lies in fourth genera- tion systems. This technology operates at a lower fl ow temperature than its predecessor, usually around 40-60°C, reducing heat losses and increasing energy effi ciency. It should also be noted that due to this lower temperature, fourth generation heat networks are ideally suited to polymer pre-insulated pipework. Moreover, this also presents an opportunity for the build to be heated by a number of more environmental- ly-friendly sources – a key consideration for any low-carbon housing development. This includes heat pumps, solar thermal


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