Guest Blog: Decarbonising Ireland’s Heat Sector

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If energy were an iceberg, electricity would be the part above the water and heat the part below, and, as it stands, it is the heat sector that will sink Irish efforts to reach net zero by 2050.

The first reason heat will sink us is simply that it involves a greater amount of energy than electricity; Ireland’s electricity demand is around 30 TWh, while heat demand is 45 TWh.

Second, progress, or lack of it, is our next challenge. Ireland’s electricity sector can now boast delivery of one of the finest engineering achievements on the planet. In the space of 20 years, we have gone from a nearly fully carbon-reliant electricity system to one that supplies around 40% of annual output from variable renewable sources, mainly through onshore wind. The only country in Europe to exceed this is Denmark, the country which invented the wind turbine! In contrast, Ireland performs worse than all other EU countries when it comes to our heat sector. Our paltry 5% renewable heat share is left in the dust by best-in-class performers like Sweden and Denmark. Worse still, our failing effort is also shown up by some of the less obvious suspects like Estonia and Latvia, both of whom provide for over 50% of their heat demand using renewable sources, some ten times Ireland’s share.


Essential Drivers of Change


Given the slow start and low base, we started from, it seems extraordinary that Ireland is now at 40% renewable electricity. That’s even more notable considering we have not yet begun to tap the enormous potential of offshore wind off Irish coasts. But when we look closer, all the key elements are there for success. We have an ecosystem of people, companies, knowledge, and capacity to drive innovation, change, and rapidly evolving solutions to continue decarbonising the sector. In contrast, the Irish heating sector is still in startup mode, with the notable exception of building fabric retrofits and heat pumps in new builds. What we currently lack are those key drivers that will help us establish and ramp up the sort of ambitious projects needed to make headway in decarbonising the Irish heat sector.

We do have cause to hope though, because what we need to do has been done before. That’s right! Unlike how the Irish electricity sector had to break new ground by developing a world-leading power system operating with 40% variable power on it, our heat sector just has to do what others have been doing for decades. Countries like Sweden, Denmark, Estonia and Latvia have all achieved renewable heat shares of over 50%. Before outlining what they have done, we first need to understand the problem and for me, the easiest way to do this is by chopping up the heat sector into different parts.


Understanding the Challenge of Decarbonising Heat


To understand how the heat sector works and the extent of the decarbonisation challenge, it is important to understand that, unlike electricity, not all kWh’s of heat are equal. This helps to simplify discussions on decarbonising electricity, the focus just needs to be on how to produce clean electricity. That’s not the case for heat as a kWh used to produce hot water in your house is not the same as the kWh of heat used to make cement. For heat, it’s not just about how it’s produced, but who will use it and for what purpose. As that’s the case, when considering how to decarbonise the sector, it’s important to know what sort of demand we’re looking at.

First off, the full extent of heat demand in Ireland is approximately 45 TWh; about two-thirds of which is used for buildings and one-third for industry.

Second, the location of buildings is important when it comes to understanding the decarbonisation potential of the heating system. The urban-rural divide plays a role here as how we heat our buildings depends more on building density than building type. In simple terms, buildings in Irish cities are more likely to be connected to a gas grid (i.e., a network solution) while those located in the countryside tend to use stand-alone systems, predominantly oil-fired boilers (i.e. an individual solution). This matters when it comes to identifying the most appropriate types of low-carbon heating solutions needed to decarbonise the Irish building stock. For the purpose of assessing the viability of heat networks, about half of building heat demand is in urban areas where buildings are in close enough proximity to merit building a network solution.

Third, in contrast to the situation with our building stock, the most important factor for industry is not geographical location or density but temperature. Buildings usually require a maximum of 70-80°C for heating purposes, but industrial processes can require hundreds and even thousands of degrees Celsius.  The key threshold for me when it comes to industrial heat requirements is 200°C as there are totally different options available to produce heat above and below this number. So, our final category to identify before we start talking solutions is the amount of heat above and below this threshold, which conveniently is split at around 50%.


Summary of Irish Heat Demand:

Heat in:TypeTWh

The biggest challenge of the heat sector in my view is understanding the problem as it is only then you can start to define what you need to solve it.  For heat this is a complex matrix of whos and hows which are heavily linked to the solutions which are available to decarbonise each one, so let’s close with a brief summary of those.


Laundry List of Decarbonised Solutions


Here are what I believe are the solutions to decarbonise each of the segments of Ireland’s heat sector:

Heat In:TypeTWhSolutions
BuildingsUrban15District heating can supply all this using waste heat, heat pumps, and geothermal and solar thermal as its supply.
Rural15Individual heat pumps can supply the vast majority of these with some timber/biomass boilers supplying older buildings
Industry<200°C8Industrial heat pumps for the majority of this, possibly district heating in an urban area if the heat requirement is <80°C or if neither, will require a similar solution to the >200°C segment.
[Energy savings around ~30% as a ballpark but this is a very tricky one, as savings in the industry is very difficult to be generic about.]>200°C8Electric boilers, biomass, biomethane and hydrogen


The wonderful part about this list is that except for hydrogen, all the solutions have been proven over a matter of decades elsewhere. Possibly the best established of these just happens to be the industry I work in day to day (funny that!), i.e., district heating, which I strongly believe has to be at the core of Ireland’s strategy to decarbonise heat.


Here Comes the Pitch!


The elevator pitch for district heating is that it involves a network of hot water in pipes ranging in diameter from ~40-800 mm that move heat from supplier to consumer. This is done in the same way that electricity, gas, or cold-water pipes move other utilities. Low-carbon district heating is achieved by using waste heat or a renewable heat producer.

Believe it or not, more heat is being wasted in Ireland today than is needed to heat all our urban areas combined[1]. In other words, if we had district heating networks in place in our cities, we could funnel heat that is currently being thrown away towards consumers, which would allow us to replace gas/oil for heating our buildings. In Copenhagen, where I lived for six years, district heating satisfied over 99% of the city’s heat demand, the central spine of which was over 100 km long. The SEAI concluded in its 2022 National Heat Study[2] that heat demand in 54% of Ireland’s buildings could be met using district heating. Shamefully, today less than 1% of heat demand is met this way, which the optimist in me chooses to see as a huge opportunity for carbon reduction, security of supply, and affordability.

While everyone in Ireland was feeling the pain of huge jumps in gas and oil prices in 2022, 90% of customers on district heating networks in Denmark saw no increase in their district heating prices[3]. Why? Because the price of the heat we throw away or of renewable energy doesn’t change in the way commodities like oil and gas do in relation to global markets. If we can supply the heat in our buildings with the heat, we currently waste, we are unlikely to experience the same shocks to consumer bills that come from depending on imported fossil fuels.

Here in 2023, I’m looking at Ireland’s heat sector hoping against hope that we meet our climate targets all the while knowing enough to understand it’s very unlikely, we’ll make it if we don’t accelerate the implementation of proven solutions very soon. For me, district heating is one of the critical solutions needed to unlock the decarbonisation of Irish heat and I’m determined to help deliver it in the months and years ahead.

Guest Blog is written by David Connolly PhD,

Chairperson Irish District Energy Association

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