Stronghouse in Sønderborg - investigating district heating

05 October 2022 - Published by Deirdre Buist
The Stronghouse partners came together again in Sønderborg on 27th – 28th September. Denmark, with a sturdy tradition in district heating, is the place to be as we all look for immediate alternatives and sustainable solutions for the current energy crisis. During this second 'live' partner meeting, hosted by ProjectZero, the consortium was keen to learn more about the Danish approach to community heating solutions.

The widespread use of district heating (DH) and combined heating and power (CHP) is one of the most important reasons why Denmark has been able to increase energy efficiency and reduce carbon emissions over several decades. District heating is a cornerstone in the country’s green and efficient energy system, ensuring availability, reliability and affordability while maintaining a sustainable energy sector and fulfilling the long-term energy policy targets.

Some simple facts

Did you know that District Heating in Denmark:       

  • supplies heat to 3.6 million people living in 1.7 million buildings.
  • must be proven cost effective for the homeowner in a socioeconomic analysis before further development. This is a government requirement.
  • is highly competitive (price) compared to individual heating solutions in cities and towns.
  • is now the cheaper solution because it is not linked to gas prices.
  • is hugely popular, with applications for connections rising sharply in recent months.

A full programme

Focussing on this theme, our hosts from Project Zero - frontrunners in the sustainable energy sector -  designed a full and varied programme, which included inspiring presentations on the planning and implementation of traditional district heating and heating pump systems, and some insights into homeowner involvement  and communication.

A number of partners also shared knowledge and experience. Gate21, for example, introduced their 5th generation heating solutions called Thermonet, while ateneKOM presented  LOWTEMP 2.0,  an Interreg Baltic Seas project about enhancing the energy efficiency of DH supply and promoting Low Temperature District Heating (LTDH) . The City of Roeselare also told more about their approach to district heating, the context, plans and goals for the coming years. Their current  system is  mainly for  big municipal buildings and consists of 20km of high temperature heating, dating back to 1986. Roeselare is now aiming to create a net that can switch to low temperature heating and faces many challenges when connecting individual existing homes in the historic centre.

Local stakeholders & expertise

During an afternoon of site visits, guided by Tue Gejl Christensen, Project Manager at Sonderborg Varme (local district heating company), the consortium heard more about the background and development of district heating in Denmark. We visited a plant to learn about energy sources, using surplus heat from local enterprises, stakeholder involvement, technical solutions and challenges – and more. We also heard the current approach to energy retrofit loans from  Danske Bank and  property evaluation before and after energy renovation from Henning Brock, a realtor and local stakeholder.


Stronghouse partners visit a brickmaking enterprise. Their surplus heat is part of the local district heating energy mix.

Energy mix

During our visit to a local brickmaking enterprise, Tue explained the importance of a varied energy mix. The surplus heat from the brickmaking process is one of  several sources the plant uses to heat 15,000 homes in the area. At the Varme district heating plant itself, we saw huge bales of biomass stacked high and ready for use this winter.

All in all,  the day provided the Stronghouse partners with lots of inspiration, fuel for animated discussions and exchange of ideas.


 Sønderborg Varme district heating plant 

Project progress & updates

The last day of the Stronghouse meeting in Sonderborg kicked off with some important project administration and reporting reminders, followed by status updates per partner. It’s exciting to hear that the partners continue to make excellent progress and real results ripen further.

So what have the partners  been up to since the last time we met? We made a compact overview.

Shifting focus

With regards to the Stronghouse focus on the Customer Journey, partners agree that as a result of the energy crisis people are very much more aware of possibilities and options to retrofit their homes. Now, with a lack of energy professionals and craftsmen, inflation and uncertainty regarding national and European policy for the direct future, Stronghouse will adapt to this state of affairs, shifting support for homeowners by guiding them through their energy journey as efficiently as possible. Digitalization is playing an increasingly important role in the energy transition and the project.

Digital learning tools

In that respect, the E-learning course developed by ateneKOM, with input from the partners, will be a real asset. Martin Guth presented the latest updates and did a quick test with the audience. The ambition is to complete this course in the coming months. ateneKOM is also responsible for a Smart Home Manual and Claire Piqueret Rose told us more. The manual contains best practices using smart technology (living appliances) and includes a Smart Home Journey. This can be helpful for homeowners starting an energy transition journey.

Innovative H2O district heating

Citizen and resident involvement is already high in Hoogeveen’s hydrogen project where the Municipality is developing an alternative for natural gas  using the existing pipeline infrastructure. The highly innovative project involves realizing a hydrogen network, connecting 100 new builds and then connecting 400 retrofit houses. Project Manager Kees Boer shared some of the legal complexities and explained three phases in the system – the supply, using electrolysis and connecting to the national  gas grid.  There are many stakeholders involved and, while continuously  adapting, there is a real commitment to creating an affordable, reliable and safe hydrogen energy system.

Power to X 

For those with less technical savvy, Kees also explained ‘Power to X’. This term is used to  describe the making of a new form of energy from any green power (e.g. the excess from wind turbines that cannot be stored via electrolysis into green hydrogen). Full focus is on energy efficiency –  for the quickest payback all rest heat must be utilized. Electrolysis is not  new but this conversion technology is now receiving lots of attention.

Digital 'One-stop-shop'

Martin Wikman of Klimatfastigheter joined forces with Linnaeus University to develop a customer-oriented One-Stop-Shop, and later paired up with Hemma to launch a digital tool for customers after undertaking his own home energy renovation.  

Martin demonstrated their online tool which provides all data regarding the property to be renovated, including the current energy label, potential retrofit options, energy savings, financing suggestions and forecast return on investment etc. Klimatfasigheter is the ’one-stop-shop’ that  then contacts all stakeholders and provides a digital renovation plan (approx. 90% accurate)  with an all in quote for the  customer, without further obligations on their part. This one-stop-shop tool contains practically all the steps of the Customer Journey. There have been some challenges with GDPR but this collaborative tool is now being piloted amongst E.on customers.

Nudging & motivation

iNudgeyou presented on behavioural insights through nudging – they’ve  teamed up with the  Municipality of Helsingør, using their data. Cooperating with Gronbolig and other Danish partners, a  key stakeholders list was created to develop a communication strategy focusing on energy efficiency, renovations, potential collaboration with craftsmen etc. Nudging is not about people but about behaviour. From preliminary research and first conclusions, iNudgeyou have found that most homeowners are motivated by price not climate - certainly a point of discussion for some.

Blockchain, banks, bonds

Spring and Gothenburg University continue their digital tool development so that customers and banks can securely share data  using anonymous blockchain technology. The software interfaces are more or less ready so the partners are now looking for a suitable blockchain. Aim is to help the banks to do accurate green reporting, proving their green loans so that they can invest further in so-called green bonds.  Spring is currently looking for banks to test and play with the technology.

CRM support tool

Gronbolig, an offspring of Project Zero, aims to help municipalities accelerate the energy renovation of private houses. Together with three Danish municipalities the project is developing a CRM system and aligning support tools. There are several comparisons  the CRM developed for the Drents EnergieLoket (DEL).  Data shows that the interest in energy efficiency is way up and live meetings with citizens are still the most effective – particulaly if there's a one-on-one  question time. Gronbolig believes contact numbers will increase even more  with digital tools – using the relevant customer data and tools per step. Every area is different and may need a different approach. “Be flexible and adapt” is the advice from Henrik Dahlerup.

Low Temperature District Heating

Meanwhile the Municipality of Albertslund has developed a conversion strategy towards Low Temperature District Heating by 2026, which is technically possible but not a popular switch to make in one go. So, using their short lines of communication ( through the Users’ Council, Energy Team and a neighbourhood approach, for example) Albertslund is motivating homeowners, offering free energy consulting, technical advice and further support on the energy renovation journey. Using own data from smart meters, the municipal company can also target so-called ‘red’ consumers - those with an extraordinarily high heat consumption.

Adapting support

According to the Municipality Fredensborg, the war has really contributed to the increased interest in sustainable energy, renovation etc. all numbers and results are high across the board, resulting in waiting lists and a lack of skilled workforce. It is clear that much has changed since the start of the Stronghouse project but the consortium is also adapting strategies in continued support of homeowners and their energy renovation journey. 


 With thanks to Anne Branderup, ProjectZero and our Danish partners for a very warm welcome