Dr David Connolly, HeatGrid and Irish District Energy Association
– Bridging the Gap: The case for district heating in Ireland
The landscape of Irish energy is at a critical juncture, particularly as the nation seeks to climb out of an unenviable position regarding its climate commitments. According to SEAI, district heating can supply up to 54% of Ireland’s building heating needs, thereby reducing carbon emissions (District Heating and Cooling Report 2022). Transitioning to district heating will play a crucial role in slashing CO2 emissions within the heating sector, propelling Ireland toward its net-zero goals by 2050.
HeatGrid Ireland
Dr DAVID CONNELLY, CEO of HeatGrid Ireland and Chairperson of the Irish District Energy Association (IDEA), is candid about the scale of the challenge of delivering a district heating network in Ireland. He points out that Ireland is very much behind Europe in the share of renewable heat in any league table.
According to Dr Connolly, one of the big reasons the country remains at the bottom of the pile is the lack of district heating. He notes, “There is almost a direct correlation between the countries that have more renewable heat and the countries that have more district heating. The reason for this is that it is much easier to deliver renewable heat at scale if there is a network of hot water pipes to deliver that heat through, rather than trying to do it through individual solutions or gas grids, which are very challenging to get large volumes of renewable heat into.”
The Danish model
The disparity between Ireland and its European neighbours is perhaps best illustrated by Dr Connolly’s personal experience. Having lived in Copenhagen for six years, he observed an urban population of about 1.4 million—similar to Dublin—served by a staggering 3,000 kilometres of district heating pipework. In stark contrast, Ireland’s current level of district heating, in the sense of pipes in public roads, consists of one pilot project in Tallaght with approximately 2km of pipework. This comparison provides insight into the gap between a city just starting and one that has been refining its infrastructure for 40 years.
History suggests that necessity is the mother of invention.
He comments, “While Copenhagen’s first small scheme began a century ago, the real acceleration happened during the oil crisis of the 1970s. At that time, most Danish buildings relied on oil boilers, and when supply became insecure and expensive, Denmark implemented a long-term energy plan to foster independence.
“The biggest shift was recovering heat that was being lost from power production. Much like Ireland today, Danish power stations were losing 60% of their energy to the air or nearby rivers. The massive uptake of district heating from the 1980s onwards was driven primarily by this urgent need for security of supply.”
Building a district heating spine
Moving from ambition to reality requires a pragmatic, project-led approach. Dr Connolly draws a parallel with his previous work in the wind energy sector, noting that large national targets were only met project by project.
“District heating will be no different. At a project level, there are natural limitations regarding affordability and risk. Typically, in areas with no existing infrastructure, projects start with a spine route of 5km-20km of pipework. This allows the first customers to be connected, usually starting with large heat users before moving to smaller ones, much like the development of the electricity grid.”
He envisions greenfield (areas without a district heating network) urban areas in Ireland, beginning with these initial networks connecting large users to a centralised heat production facility that ideally incorporates waste heat.
He adds, “Over time, these networks can be densified as smaller users join. join. Although the flagship Poolbeg project in Dublin has been discussed for two decades and is still not completed, future projects should not take that length of time.”
He highlights that, elsewhere, some projects have moved from concept to operation in just four years. So he emphasises that it is vital that Irish projects move into the construction phase quickly so that the public can see the benefits.
The capital cost barrier
One of the most significant hurdles remains the high upfront cost of building the first spine routes. Dr Connolly argues that because these networks are designed to last 50 to 100 years but must be paid for on day one, the initial customers cannot be expected to carry the full cost if the heat price is to remain competitive.
He describes this as a never-ending chicken-and-egg scenario. “To overcome this, we need only look at the success of the 50% capital support grant in England, which offsets initial costs to a level that encourages customers to join.”
Under Ireland’s National Development Plan (NDP) for 2026– 2030, up to €100m has been allocated to support the development of district heating networks, reinforcing the country’s decarbonisation strategy. This funding aims to scale up sustainable heating, utilising waste heat and renewable sources.
Dr Connolly welcomes the recent transformation in government policy, with a dedicated District Heating Division now established within the Department of Climate, Energy and the Environment. “We are now waiting for the SEAI to finalise the terms and conditions to release funding to develop the first spines. I believe that once this is in place, we will see the first 5km-20km projects for which we have been advocating. Between now and 2030, the priority must be getting enabling funding into the market to kickstart these initial networks.”
Data centre district heating
A unique opportunity for Ireland lies in its data centre clusters. Dr Connolly dismisses the notion that heat can only be moved short distances, noting that networks in other European cities move heat over 50km.
“Data centres present a huge opportunity to use waste heat, and since they are often located near urban centres, they are well-placed to act as sources. Commercial buildings would play a huge role as anchor customers, getting the first pipes in the ground, allowing the network to eventually expand into smaller residential areas.
“For facility managers, district heating would be a way to outsource the heat utility. Instead of managing an on-site plant room with a gas boiler or heat pumps, a pipe delivers hot water at 80°C to the door. This allows the building manager to focus on the commodity delivered rather than the production equipment. More importantly, it offers a cost-effective way to decarbonise. Rather than upgrading individual buildings one by one, district heating decarbonises the heat source for a large network of buildings simultaneously.”
What this all means for building services engineers
From an engineering perspective, district heating simplifies buildings. Having a single point of connection to supply an entire building is a major advantage compared to multiple plant rooms.
Dr Connolly explains, “District heating thrives on low supply temperatures and a wide Delta T, similar to heat pumps, though district heating typically supplies water at around 80°C, which is higher than what many heat pumps provide.”
He adds, “Crucially, district heating provides a path for the retrofit of older buildings. If a building connects to a network on day one, it is immediately decarbonised because it is purchasing low-carbon heat. This removes the immediate pressure to perform costly and challenging building fabric upgrades. Fabric improvements can be overseen over the subsequent decade, but the primary goal of decarbonisation is achieved from the start. This flexibility is a primary reason why so many European cities have chosen district heating as their primary tool for the energy transition,” he concludes.
In conclusion
As the first spine networks move from concept to construction, Ireland has a unique opportunity to turn its data centre clusters and industrial waste heat into a cornerstone of national energy security. By focusing on these pragmatic, project-led successes, the goal of supplying over half of the country’s heating needs through district networks by 2050 becomes less of a distant ambition and more of an engineering certainty.
To learn more visit www.heatgrid.ie or www.districtenergy.ie