District heating
Unlocking the potential of heat networks
Steve Dawson, from Guardian Water Treatment, explores the challenges and opportunities of district heating systems, explaining the critical role of water quality monitoring in improving energy efficiency, reliability and performance outcomes
D
istrict heating systems hold a great deal of potential for the low carbon future, but problems with aging infrastructure, poor
maintenance practices and a lack of regulation threaten to stall progress, with system operators caught in an expensive game of ‘catch-up’ and tenants exposed to dangerous situations. There are two sides to every story, and district heating is no exception. On one hand, heat networks are seen as a key low-carbon technology in the transition to Net Zero. They offer great potential to incorporate low-temperature systems, such as heat pumps, as well as integrating a growing proportion of energy from waste facilities and industrial processes, geothermal sources and renewables into the heating mix. Heat networks meet around 2% of heat demand in the UK, but according to government research, this could rise to 18-20% by 2050. In a changing energy landscape, district heating
networks have emerged as an effective solution to delivering reliable and affordable heat to domestic tenants, particularly for social housing providers. 90% of the UK’s 17,000 heat networks serve residential developments; however, to date, their potential remains largely untapped – most are still powered by natural gas and a lack of understanding surrounding system maintenance means operational issues are common. Not only does this result in severe energy efficiency and cost implications, but also poses a danger to residents. One tenant, who lived on a district heating-
powered housing estate in London, told The Observer how two radiators exploded in his child’s bedroom during the night, shooting scalding hot water across the room and damaging ceilings and floors. Luckily, the family was away at the time of the incident, but this sorry tale illustrates how high the stakes are here for network operators. One of the key problems is that many heat
networks are run by local councils, housing associations or private companies that lack expertise
18 July 2023
www.heatingandventilating.net
and resources. Many are simply overwhelmed by the sheer scale of the upgrades required and are caught in a continual cycle of ‘catch-up’ rather than taking any meaningful or preventative action. While it may seem tempting to bury heads in the
sand, ignorance is certainly not bliss. If operational issues such as regular leaks or poor efficiency are neglected, it will almost certainly lead to increased replacement/remedial costs, reduced overall lifetime of valuable plant and equipment and high costs for service users. District heating networks tend to operate at higher pressure and temperatures compared to traditional central heating systems and un-serviced equipment can easily be overwhelmed, potentially resulting in costly litigation. So, what can district heating providers do to mitigate these risks? Invest in a proactive and data-driven approach to district heating network management, with a particular focus on water quality, which has been proven to be a leading cause of heat network failure.
In a 2019 study published in CIBSE journal,
Jon Greaves, managing director of Hydro X Water Treatment and WCS Water Division, identified specific issues leading to system failure across 185 heat networks, which included poor water
quality at handover and corrosion-related water loss, concluding that “continuous monitoring and automatic dosing should be installed on all district heating networks to minimise the risk of corrosion and associated water treatment issues.” Real-time remote monitoring technology is the
only way to detect early signs of corrosion. By tracking key parameters, such as pressure, pH, galvanic currents, crevice corrosion, make-up water, inhibitor/glycerol concentration, as well as critical dissolved oxygen levels – known to be the precursor to all corrosion in closed circuit water systems – network operators can make informed service interventions and begin to identify and rectify the root cause of operational issues, rather than just treating the symptoms. Network operators should not be afraid of data. Heat networks are hugely complex systems and the only way take back control is through increased transparency. With a true and accurate picture of water quality within the system, those responsible for heat network maintenance can deliver better outcomes, minimising unexpected costs and downtime, while helping this key technology to meet its potential to deliver affordable, sustainable and reliable heat to those who need it most.
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