DBDH publishes Hot Cool, but the main business is helping cities or regions in their green transition. We will help you find specific answers for a sustainable district heating solution or integrate green technology into an existing district heating system in your region – for free! Any city, or utility in the world, can call DBDH and find help for a green district heating solution suitable for their city. A similar system is often operating in Denmark, being the most advanced district heating country globally. DBDH then organizes visits to Danish reference utilities or expert delegations from Denmark to your city. For real or virtually in webinars or web meetings. DBDH is a non-profit organization - so guidance by DBDH is free of charge. Just call us. We'd love to help you district energize your city!

NO. 8 / 2023




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THE AWARDS By Dr. Robin Wiltshire and Sabine Schimetschek, 5 4





HEATING By Peter Jorsal





NEW MEASURES FOR REDUCING LEGIONELLA IN HOT WATER SYSTEMS By Kaj Bryder, Ditte Andreasen Søborg, Leon Buhl, Torben Schifter-Holm, Henrik Kjeldsen, Carl Hellmers,

Tommy Steen Møller, Nikas Arp-Wilhjelm, Søren Anker Uldum, and Hagbard Clausen

DBDH Stæhr Johansens Vej 38 DK-2000 Frederiksberg Phone +45 8893 9150

Editor-in-Chief: Lars Gullev, VEKS

Total circulation: 5.000 copies in 74 countries 10 times per year

Grafisk layout Kåre Roager,

Coordinating Editor: Linda Bertelsen, DBDH

ISSN 0904 9681

What if digitalisation could make energy more sustainable?

With frequent data readings, automated measurements, and real-time decisionmaking, digitalisation optimises districtheating. At Kamstrup, we have theknow-how and digital solutions to improve energy efficiency.


The Global District Energy Climate Awards is an international initiative coordinated by Euroheat & Power assisted by the IEA DHC and with the support of the UN Environment Programme, the International Energy Agency (IEA), the International District Energy Association (IDEA) and the Asian Pacific Urban Energy Association (APUEA). THE AWARDS

By Dr. Robin Wiltshire, Chair, GDECA and Chair, International Energy Agency Technology Collaboration Programme on District Heating & Cooling (IEA DHC)

It is always a great pleasure to be involved with the Global District Energy Climate Awards (GDECA), by the way co-initiated by DBDH back in 2009. I speak here not only for myself but also for the other members of the panel. Members of the panel convene biennially to judge the new submissions. The panel comprises experts with breadth and depth of experience over many years in technical consultancy, financial, and managerial roles. Why, you may ask, do we find ourselves waiting with bated breath for the new group of submissions? The answer is sim- ple: across the world, innovative people and supportive munic- ipalities are conceiving and delivering new and exciting ideas for district energy! And we hope that these examples will also inspire others to act! We notice particularly the versatility of this technology that can be applied in so many case-specific circumstances - the range of building types, climate, and, crucially, its ability to make use of a vast range of heat sources. This flexibility enables heat net- works to spearhead the penetration of renewable heat sources and is the only way to effectively recycle locally available ‘waste’ heat at scale. We have also noticed the increasing importance and presence of district cooling. The very fact that individual systems are so case-specific means that it is not easy to bring these successes to the attention of a wide audience and, crucially, to decision-makers. It is our mis- sion to reveal these successes. The Global Awards are an excel- lent way to demonstrate the possible achievements and diver- sity of approaches. Winners benefit from recognition at the Awards Ceremony and beyond, with their submission receiv- ing international media attention and ongoing presence on the GDECA website, and local prominence is raised through a letter to community dignitaries. Applicants can enter a system into one of six categories. These are intended to cater to coun- tries with mature district heating markets and countries where the market is still being established. There is also a category for countries with developing economies. Brand new systems have their own category, as do systems that are being modern- ised and extended and those which demonstrate increasing synergies between thermal energy systems and electricity sys- tems (i.e. sector coupling).

The panel assesses each submission across a range of criteria. Applicants must highlight the Why? the How? and the What? for the system they are entering. These aspects embrace, respectively, clean energy transition and community benefits, how technical and financial aspects have been tackled, and greenhouse gas reductions. Future sustainability, innovation, and replicability potential are key elements, a testament to the vital role that heat networks can play. But now, having explained why we engage in this process, how about some of the specific systems that have applied and won? Here, I would encourage you, when you have a spare moment or two, to turn to our website and see for yourself!

Winners | Global District Energy Climate Awards (

The task of identifying the winners is always difficult because so many submissions have achieved great things, but only the winners secure an Award! For that reason, we occasionally issue a Certificate of Merit if an applicant misses out by a hair's breadth. You would not expect me to reveal the winners of the latest edition of the Global Awards. That is the purpose of the cere- mony that will be taking place on 14 November in Brussels as part of the Euroheat & Power Summit. Suffice to say that the range and quality of submissions this time fully lived up to the predecessors from earlier rounds. Once more, difficult decisions were made, but I can confidently say that we once again have a truly impressive set of winners. Maybe you will have been with us in Brussels for the ceremony itself, but if not, please do look at our website to find out! Finally, please consider joining in with your own submission to the next edition. In this industry, there are so many innovative examples of new initiatives and modernisation of existing sys- tems that the world needs to know about! So please watch out for announcements! You can stay up to date and receive the latest information by subscribing at the website.

Schemabild Elektroöfen © Badische Stahlwerke

On the German-French border in the region of Strasbourg-Kehl, a showcase project for cross-border cooperation in the municipal heat transition is emerging. In the future, 7,000 households on both sides of the Rhine will be supplied with waste heat from the local steel mill. Due to its transnational nature, the project faces several challenges. Nevertheless, the high level of commitment of all partners and the active support of governmental institutions combined with financial support from French (ADEME), German (BAFA), and European (INTERREG) funding agencies have made the project possible. EXCESS HEAT FROM STEEL MILL FOR CROSS-BORDER DH COOPERATION

By Dr.-Ing. Volker Kienzlen, KEA-BW,

Reiner Hagemann, Badische Stahlwerke GmbH (BSW),

Sabine Schimetschek, Calorie-Kehl Strasbourg (CKS)

Badische Stahlwerke has been looking for a way to use this waste heat for decades. In the nearby industrial area of the port and the town of Kehl, three kilometres away, there are no suitable customers for such large quantities of heat. On the other side of the Rhine lies Strasbourg - a city that already op- erates large district heating facilities and would like to expand these even further regarding the climate policy goals. By 2050, at the latest, Strasbourg's heating networks are to be entirely climate-neutral. Therefore, Strasbourg not only plans to extend the district heating system but also intends to lower the net- work's temperature. The first idea to use the enormous amount of excess heat dates back to 2014. In 2018, the KEA-BW, the state energy agency in Baden-Württemberg, initiated another attempt to use the heat that cannot be used within the company. The rising importance of climate protection and the neces- sity to become climate-neutral was a new baseline for the discussion with BSW and the cities of Kehl and Strasbourg. Improved funding conditions were also helpful. In July 2018, the Baden-Württemberg Ministry of the Environment com- missioned a study to the engineering company EGS-Plan, confirming the project's technical and economic feasibility. Since then, the Eurometropolis of Strasbourg, the Badische Stahlwerke, and the city of Kehl have been working with KEA-BW, dena1, ADEME2, and several other stakeholders to push forward the German-French cooperation project. This was followed by further studies to clarify the potential, the heat requirements in Strasbourg and Kehl, as well as the pos- sible layout of the heating grid. Since the district heating network in Strasbourg is rather old, some areas of the network still require flow temperatures of more than 140 °C when the ambient temperature is very cold. For BSW, this means that the outlet temperature in the heat exchangers has to be raised to 160 °C, which increases the operating pressure significantly. The existing system cannot meet the safety requirements, which is why the entire prima- ry cooling system must be rebuilt. This also includes replacing the heat exchangers for the secondary cooling tower circuit, which ensures heat dissipation during low district heating de- mand periods. The part of Strasbourg’s district heating system relevant to the project consists of the two interconnected heating networks, Esplanade and Elsau. Two gas-fired boilers are used to cover the peak load. The base load is generated by a biomass co-

BSW, the Badische Stahlwerke, runs a steel mill in Kehl. In the harbour area north of Kehl, they produce 2 million tons of steel per year, mainly for the construction sector. Two electrical fur- naces use steel scrap to produce reinforcing steel. The main waste heat source is the exhaust gas from the two electric arc furnaces where the steel scrap is melted. There are also other potential sources of excess heat, e.g., the pusher furnaces, where billets are reheated for further processing. In the first step, the waste heat from the electric arc furnace will be used. In the future, however, other waste heat potentials could also be used. The exhaust gases, up to 1,300°C hot, will flow through a water-cooled heat exchanger, which pre-cools the gases to approx. 600°C. The cooling water in the heat ex- changer runs in a closed circuit and has a flow temperature of approx. 70 °C and an outlet temperature of up to 90 °C. Due to the melting process, the water temperature fluctuates greatly since cold scrap is charged at the beginning of the process, and molten steel is tapped at 1,600 °C at the end. In addition, there is a short production downtime in summer and a three- week downtime in winter. On average, a heat flow of 20 mega- watts is cooled to ambient air. Based on the production data of the steel mill, this results in a total available waste heat of 135 gigawatt hours per year.

Direct dedusting of electric arc furnace

to the baghouse

electric arc furnace


heat exchanger (160°C)

Badische Stahlwerke GmbH

Schemabild Elektroöfen © Badische Stahlwerke


2 French environment and Energie management agency -

Badische Stahlwerke

To District Heating Network Strasbourg

District Heating Network Kehl

The coordination effort is very high, given the many players from both countries involved. In the practical implementation, many organisational and legal issues must be solved. This in- cludes a suitable binational organisational structure. For the construction and operation of the necessary pipeline, a mu- nicipal public company was founded under French law, al- lowing foreign local authorities to participate. In this “Société d’économie mixte locale Calorie Kehl-Strasbourg” (SEML CKS), the Eurometropolis of Strasbourg has the largest share of 47 %. Smaller shares are also held by the city of Kehl (12.75 %), the region Grand Est (12.75 %), the state of Baden Württem- berg (12.75 %), and the French Banque des Territoires (CDC) (15 %). Badische Stahlwerke (BSW) also holds one share and is involved as an observer. The general director of Calorie Kehl-Strasbourg, Sabine Schimetschek, was born and raised in Germany but worked most of her professional life in France. Thus, she embodies the cross-border character of the project. Since the common goal is to start operating the system by 2027, CKS pushes the design and planning process forward. The rise in construction costs combined with increasing ener- gy prices due to the energy crisis of 2022 requires an update of the calculation of project economics. Now, an engineering company analyses the outline of the pipeline with the need to minimize construction costs and the requirements in the approval process at the same time. The initially preferred micro tunnelling minimizes the interference with existing infrastruc- ture but is the most costly solution. Therefore, alternative con- struction methods are investigated.

generation plant and the municipal waste incineration plant. This means about 60 percent of the heat is already provided by renewable or CO2-neutral energy sources. As the heat from the biomass cogeneration plant is still subject to a multi-year pur- chase obligation, the waste heat from BSW will only be able to replace a significant part of the heat produced by gas boilers in the winter months. The planned increase in annual district heating sales from the current 256 GWh to 318 GWh in 2030, however, allows for more and more waste heat use, especially in the transitional months of the year. With the expansion of Strasbourg’s heating system in mind, further sources of excess heat from the steel mill can be used. Furthermore, the opera- tor of Strasbourg’s district heating system intends to lower the operating temperature in the long run. In the coming years, the new development “Zollhofareal” will also be built in Kehl, on the southern Rhine harbour near the main station, which will also be supplied with waste heat from BSW. Accordingly, at least 70 GWh of the total available waste heat of 135 GWh can be used in the district heating networks of Strasbourg and Kehl. 7,000 households can be supplied with this energy, thus saving almost 20,000 tons of CO2 emissions per year. Kehl’s district heating system is already at a much lower temperature level. With a maximum temperature of 90 degrees, the return flow from Strasbourg can be used today as a supply for Kehl. This leads to an increased temperature spread in the transport pipe and reduced pumping energy. Should the return temperature from Strasbourg be below Ke- hl’s operating temperature in the long run, an injection system can raise the temperature level for Kehl. Implementing district heating projects using industrial waste heat is complex and costly. The cross-border dimension of the project faces additional challenges. The different languages spoken on the two sides of the Rhine and the different cultures of project management require additional effort to make the project successful.

For further information please contact: Volker Kienzlen, volker.kienzlen@

PertFlextra – A NEW FLEXIBLE PIPE SYSTEM to improve the efficiency of District Heating

By Peter Jorsal, Product & Academy Manager, Kingspan LOGSTOR

A new flexible pipe system with plastic service pipe is the result of Kingspan LOGSTOR’s participation in the COOL DH development project. This is the pipe system the district heating industry has been waiting for. The main objective of the COOL DH development project was “to support cities in their endeavor to plan and deploy new, efficient district heating and cooling (DHC) systems and extend and refurbish existing ones to higher standards and thus, allowing greater uptake of renewables, recovering of excess heat or cold while improving the overall efficiency of the systems.”

PertFlextra is a result of the COOL DH development project. More than three years ago, together with other companies, we joined an EU development project, COOL DH.

District Heating as a concept has a vital role in the green tran- sition in Europe, a journey towards fossil-free energy electricity, district heating production, and lower CO2 emissions. The green transition has kickstarted a massive need for expand- ing existing and building new district heating pipe systems. In many countries, this results in a lack of contractors to do the job. Therefore, the district heating market is looking for a solution that can be a good alternative to traditional steel pipe systems in relevant dimensions where there is no dependency on steel welders. Or, to be more specific:

The Kingspan LOGSTOR objective for the COOL DH project was to “Design and build a low-temperature district heating grid with non-conventional pipe materials. Test new innovative pipe components introduced by COOL DH”.

High speed of installation

The focus of the development project was the following:

Less dependency on steel welders

Develop a plastic service pipe that should have a more robust performance on temperature and pressure than the present standards on the market, service pipe 25 - 110 mm SDR 7,4

Sustainable solutions

Low heat loss over a lifetime

Lifetime and performance of the PE-RT service pipe Lifetime on a plastic service pipe can, according to EN15632-2 Annex A and prEN17878-2 Annex A, be calculated according to Miner’s rule when knowing the typical temperature and pressure profile of the pipe system. The service pipe in PertFlextra is SDR 7,4 PE-RT, whereas the service pipe on PEX pipes on the market is SDR 11. SDR 7,4 will have a higher wall thickness than SDR 11, and when doing the calculations according to Miner’s rule, PE-RT SDR 7,4 will have better lifetime performance compared to PEX SDR 11. In other words, a system with PE-RT SDR 7,4 can be operated with higher pressure than a system with PEX SDR 11 at the same temperature profile. Low heat loss during the entire lifetime of the system There are three contributors to the low heat loss over a life- time.

Secure low heat loss in the entire lifetime of the pipe system

Develop a system with plastic service pipe with the possibil- ity of having an integrated surveillance system.

The plastic service pipe shall be weldable, leading to the possibility of using electro-fusion couplings when connect- ing the service pipe.

The flexible pipe shall be easy to install with a focus on the work environment.

During this project, LOGSTOR developed PertFlextra, and 1900 m TwinPipe was installed in a project in Høje Taastrup, and 1900 m single- and TwinPipe was installed in Lund.

For further information about the COOL DH project, please see

PertFlextra in details PertFlextra is a complete range of diffusion-tight, flexible, pre-insulated pipe systems for community heating and district heating, according to prEN17878-1/2. The service pipe in PertFlextra is made of polyethylene PE-RT type II SDR 7,4 featuring an aluminum diffusion barrier that prevents the diffusion of oxygen into the media and water vapor from the water into the PUR foam, thereby ensuring that the foam stays dry over a lifetime and heat loss remains low. The service pipe is insulated with PUR foam, and the outer casing of HDPE has a built-in EVOH diffusion barrier that will ensure that heat loss property will not deteriorate over the life- time.

Low lambda value of the PUR foam

Diffusion barrier for water vapor on the PE-RT service pipe

Diffusion barrier in the corrugated casing for the PUR foam insulation gasses

Low lambda value of the PUR foam: The PUR foam where cyclopentane is the blowing agent.

Cyclopentane is accepted in the REACH regulations and does not conflict with any future additional restrictions, e.g., related to PFAS restrictions. Cyclopentane leads to insulating proper- ties that are far better than, for example, pure CO2-blown PUR foam.

The following describes the outcome of the targets defined in the COOLDH project.

The latest lambda test on FlextraPipe has been carried out at


Corrugated outer casing and high density polyethylene (HDPE) with built in diffusion barrier (EVOH)

Polyurethane (PUR) with blowing agent Cyclo pentane

PE-RT protection layer

Aluminium diffusion barrier

PE-RT type II SDR 7,4

On the project in Høje Taastrup, a Detector type X6 for imped- ance measurement is connected to the 3dc wires in the flex- ible pipes. Flexibility of the pre-insulated flexible pipe High flexibility is secured by combining the design with a cor- rugated casing and a soft PUR foam. We have tested the flexibility of PertFlextra by bending tests and compared it to the flexibility of the corresponding dimen- sions of PexFlextra and AluFlextra. The dimensions of the ser- vice pipes are 32 mm, and the casing dimension is 90 mm.

the institute IMA Materialforchung und Andwendungstechnik GmbH, according to requirements in the EN standards, show a lambda50 on 0,0201 W/mK. Diffusion barrier for water vapor on the service pipe: The aluminum diffusion barrier on the PE-RT service pipe shall prevent oxygen diffusion into the water and avoid water vapor diffusion into the PUR insulation. Concerning heat loss, the European standard for flexible pipe systems EN15632-1 Annex B and prEN17878-1 Annex B defines that if a supplier does not have the diffusion barrier for water vapor on the service pipe, the declared lambda value shall be multiplied with a factor 1,1 to achieve the design lambda value. Reference is made to a report done by the Danish Technolog- ical Institute, “Fleksible præisolerede rør med fugtig isolering” (Translated to English as “Flexible pre-insulated pipes with wet insulation”). The pipes tested in this project are flexible with PEX service pipes (without water vapor diffusion barrier) oper- ating for some years.

Diffusion barrier in the casing for diffusion of insulation gasses:

An EVOH diffusion barrier co-extruded into the casing of Pert- Flextra shall prevent the diffusion of insulation gases out of the PUR foam and the diffusion of atmospheric air into the PUR foam. About heat loss, the European standard for flexible pipe sys- tems EN15632-1 Annex B and prEN17878-1 Annex B defines that if a supplier does not have the diffusion barrier for insula- tion gasses, the declared lambda value shall be multiplied by a factor of 1,25 to achieve the design lambda value. Possibility of having a surveillance system on a pre-insulated flexible pipe system with a plastic service pipe With an integrated surveillance system on a flexible system with plastic service pipe wet foam can be detected whether the moisture is coming from a leaking service pipe or from out- side due to wrong joint installation or due to damage on the casing. On pre-insulated flexible pipe systems with a plastic service pipe without a water vapor diffusion barrier, it will make no sense to include a surveillance system as an integrated part of the flexible pipes. This is because it is known (see above) that there will be water permeation into the foam, and the foam might get wet over a lifetime. PertFlextra has a water vapor diffusion barrier on the service pipe, enabling the possibility of integrating a surveillance sys- tem in the pre-insulated flexible pipes, PertFlextra. In the COOL DH project, the pre-insulated flexible pipes were delivered with the 3dc surveillance wires for an impedance surveillance system.

Tests show that the flexural stress needed to bend PexFlextra (SDR 11) is 19% lower than bending PertFlextra (SDR 7,4), and the flexural stress needed to bend PertFlextra is 18% lower than bending AluFlextra. Qualifying an electro-fusion coupling for connection of the PE-RT service pipes: This was defined as part of the COOL DH project, but time was too short to do this qualification during the development period of this project. Tests done to qualify PertFlextra Before the launch of the new pre-insulated flexible pipe sys- tem, it is necessary to conduct several tests on the service pipe itself, the service pipe together with couplings, and tests on the pre-insulated pipe. This is to ensure that the pipe system with components will live up to the requirements in the standards and ultimately have the expected lifetime.

All below tests are done, and requirements in the standards are fulfilled.

Thermal stability test of the PE-RT service pipe (Danish Technological Institute): PE-RT service pipe is tested with 2,4 MPa and 110 °C for 15.000 hours. No break on the service pipe is allowed.

Coupling test of press couplings and compression couplings installed on the PE-RT service pipe (Danish Technological Institute): Thermal cycling test of the coupling installed on the PE-RT ser- vice pipe for each pipe dimension. 2000 cycles up to 32 mm and 1000 cycles from 40 mm and bigger dimensions. No leak- age allowed. Oxygen diffusion tightness of the PE-RT service pipe (KIWA): Oxygen diffusion shall not exceed 1,8 mg/m2*day at 80 °C. On the test was measured 0,06 mg/m2*day Water vapor permeation (Danish Technological Institute): We have tested water permeation (mg/m/day) on PE-RT type II SDR 7,4 with an aluminum diffusion barrier and on PEXa SDR 11 at 95 °C. Dimension of pipe 32 mm.

Axial shear strength (Type test, internal): Axial shear strength shall be a minimum of 0,08 MPa.

On the test of PertFlextra, the axial shear strength was meas- ured to 0,22 MPa.

Complete range of products for the PertFlextra system, service pipe dimension 25 – 63 mm PertFlextra is available as single pipe and TwinPipe systems and includes all press couplings, casing joints, fittings, and tools needed to establish a complete pre-insulated piping network.

The dimensions of the service pipe will be 25 – 63 mm, and the casing dimensions will be 90 – 180 mm.

On a PEXa SDR11, water permeation was tested at 367 mg/m/day.

On PE-RT type II SDR 7,4 with an aluminum diffusion barrier, the water permeation was tested to 2,3 mg/m/day, which is considered within the measurement uncertainty. At lower temperatures, the water permeation will be lower. At 75 °C, the water permeation will be approximately 50% lower than at 95 °C. The conclusion is that on plastic service pipes without a water vapor diffusion barrier, there is considerable water permeation, and on PE-RT with an aluminum diffusion barrier, the issue with water permeation is solved. To secure the water vapor diffusion tightness of the entire installed system, couplings shall be wrapped with an alu wrap before installing the casing joint. Please see the below picture:

Further development to meet the full potential of the COOL DH project The reason for not introducing dimensions 75 - 110 mm at the first launch is that during the production of these dimensions for the COOLDH project (Deliveries to Lund) were safety issues for the production employees that should be solved first.

At a later stage, larger dimensions of PertFlextra and electro-fu- sion couplings will be introduced.

Linear water tightness (Type test, internal): The requirement is that the amount of water leaking through any of the pipe ends shall not exceed 100g after 168 hours.

For further information please contact: Peter Jorsal,

On the test of PertFlextra, no water was leaking through the pipe ends after 168 hours.


By Steen Schelle Jensen, Head of Business Development – Heat/Cooling Solutions, Kamstrup

To meet future demands, district heating must become the most attractive option in terms of reliability, price, and colour. Utility professionals know this. What many of them don’t know is how to get there. Fast. The key lies in optimising across the entire value chain and balancing supply and demand better. Unlocking the demand side through end-user engagement and data-driven transparency is especially important. The good news is that ambitious utilities and solution providers are already leading the way with innovative digital solutions available today.

European district heating utilities are at a crossroads. While recognized as an established and proven technology today, there is little dispute that the future district heating system must be green, reliable, and attractive. At the same time, dis- trict heating has never been more relevant, necessary, or pop- ular – which means the pressure truly is on to connect more and more consumers and buildings to both new and existing district heating networks. The green transition is undeniably linked with low-temperature district heating. First and foremost, lowering flow and return temperatures is a prerequisite for integrating more renewable energy sources and waste heat. Secondly, it also allows district heating systems to be operated more efficiently – in terms of

energy as well as costs. And finally, reducing return tempera- tures is vital for utilities to ensure that they are utilising their existing network capacity to the fullest as they connect new buildings and end users. Involving the end users and putting frequent data from man- datory remotely read smart heat meters into play is critical to achieving all three things. Unlocking the demand side After years of intense focus on digitalising district heating, there’s no shortage of insights and digital tools tapping into which heat sources utilities should use or how to build and optimize their distribution network, etc. As a result, most util-

Today, a lack of overview and scalability means that issues are mitigated reactively as they arise. Manual processes mean that diagnostics often require experts to interpret graphs and trends. Finally, limited knowledge of effects and results means utilities don’t always know what actually works, what doesn’t – and how to get the most out of their efforts. Attacking the demand side, therefore, requires a whole new set of knowledge, competencies, and digital tools for engaging and serving end users. Together with some of our most ambi- tious customers, we have seen the pros, cons, and effects of three concrete digital solutions to this challenge. — No. 1: Motivation tariff When influencing customers to lower their return temperature, implementing a motivation tariff is one of the lowest-hang- ing fruits. It may be the obvious place to start. Still, it is also a somewhat one-dimensional approach that relies solely on the financial punishment of poor-performing end users rather than optimization as such. This approach also adds an obligation to the utility itself as incentivizing your customers to make a change – rather than just paying the added tariff – requires you to educate, sup- port, and guide them. After all, even if they do contact, e.g.,

ities today have a good understanding and full control of the production and distribution parts of their value chain – both of which are also made up of the utilities’ own assets. The demand side of district heating, however, remains severely underserved. While this part of the value chain is the end users’ territory – and responsibility – it holds enormous potential for utilities because what happens inside the con- nected buildings in your network significantly impacts its overall efficiency. Considering, for example, that reports have shown 50-60% of all heat installations to be either faulty or installed incor- rectly and that some utilities say that as little as 6% of their poorest performing customers account for 20% of the total flow in the network, there’s no time to waste. The problem is that many utility professionals don’t have the right tools for the job. One goal – three tactics Engaging and motivating end users to optimize their heat installation to improve return temperatures and lower supply temperatures is both difficult and time-consuming. On top of that, optimizing faulty heating systems is a continuous task if you want to avoid temperatures going back up.

a plumber to help solve a particular issue, they will still need to know what to tell that person. In other words, this option cannot stand alone, which is also the experience we hear back from our customers. — No. 2: Customer guidance Data-driven customer consultancy and guidance is the next step in motivating customers to take responsibility for their heat installation and return temperature. This can occur in many interactions – from onsite visits and targeted letters to digital notifications (often well-hidden behind demotivating three-step log-ons). Kamstrup’s customers’ experiences show that by combining the best of both worlds with customized letters, utilities can multiply the effect of their communication to end users whose installations are faulty or misadjusted. But just as these letters must be customized, relevant, and easily accessible for the consumer, they must also be efficient for the utility to make – and both demands speak to the need for data. DIN Forsyning in Esbjerg, Denmark, has taken the first signifi- cant steps from reactive fault detection to proactive low-tem- perature operation in its network supplying heat to its 27,000 consumers. The utility’s energy consultant saw positive results from creating customized letters outlining specific challenges and potential, which led to a temperature of 9-12 °C – com- pared to almost no reduction from generic letters simply stat- ing that something is wrong. However, each letter took approx- imately 30 minutes because he had to pull data from different systems manually. Through a collaboration with Kamstrup, it became clear that he didn’t need a longer, more detailed list of optimization opportunities – he only tackled the tip of the iceberg anyway. Instead, he needed help prioritizing the most relevant heat installations to address and generating customer-specific let- ters in seconds. Today, a dedicated cloud solution does just that. As a result, the utility now sends out 16 times more cus- tomized letters. With an innovative digital low-temperature assistant tool, DIN Forsyning also benefits from continuously monitoring all instal- lations to ensure issues are identified, prioritized, and resolved efficiently. In addition, the tool enables easy access to notify end users and keep track of interactions, plus full transparency in progress and results. And this is only the beginning. Imagine a future where data is used to pinpoint the problem and enable the utility to pro- vide exact information on what needs to be fixed – maybe even putting the end user in direct contact with somebody who can help immediately. — No. 3: Heat Installation as a Service The third option takes utilities one step closer to their custom- ers. By offering rental units and service agreements to monitor, maintain, and optimize utilities, they can take responsibility – and thereby control their end users’ heat installations’ per- formance. This move naturally demands significant effort from the utility’s side, especially in the beginning.

“The green transition is only possible if we bring the customers with us and are able to heat buildings optimally.” — Claus A. Nielsen, business development director, DIN Forsyning

Several Danish utilities have already seen great success with this option – which only highlights the importance of having the right tools and data for the job. Having network optimiza- tion in their hands not only enables direct influence and trans- parency but potentially allows for new offerings and business models. Danish Næstved District Heating utilises all three tactics to optimize the demand side of its value chain. In addition to a motivation tariff and energy consultants doing customer visits, the utility developed a rental and maintenance program for heat installations, which they offer to end users as a customer service – with great success. One of the results of their proactive approach is a reduction in the average flow temperature at the entrance of the distri- bution network from 85.3 to 73.7 °C in 2020. In addition, the average return temperature at the end of the distribution net- work was reduced from 47.9 to 43.9 °C, and the heat loss in the distribution network was reduced by 8%. Finally, the utility also reduced the number of bypasses in their network from 131 to 10. Næstved District Heating has seen total annual savings of €350,000. And today, none of the utility’s customers get a flow temperature of more than 75 °C. The resulting lower return temperature also means that significantly fewer cubic meters of water now have to be pumped. From more efficient to better and beyond As the examples from DIN Forsyning and Næstved District Heating clearly show, with the proper insight and tools, the optimization potential on the demand side is enormous. And with more data, we can go so much further. What if we didn’t stop at enabling utility professionals to be more efficient but even better? What if we co-created digital solutions designed to provide some specialist knowledge that

would otherwise be both time and resource-heavy to acquire? What if we fully utilized the value of data from smart energy meters and innovative digital tools? One thing is certain: To future-proof district heating, we’re beyond simply showing our understanding of the challenges utilities face. It’s time for solution providers to present real- world results and proven solutions – ready for implementation.

Today Best effort approach with the available resources

Limited overview and scalability

Reactive fault detection

Limited tracking of results and impact

With a digital assistant tool Continuous monitoring of all heat installations at scale Prioritized list of most relevant heat installations to address, but existing and future problems Easy access to notify end-users and to keep track of who has been contacted when

Full transparency in the progress and results achieved

For further information please contact: Steen Schelle Jensen,

Figure from Næstved District Heating.


Legionnaires’ disease, a severe pneumonia caused by Legionella bacteria, has become a growing challenge in Denmark and other European countries. A comprehensive Danish project on Legionella in domestic hot water systems has developed and demonstrated three innovative solutions to minimize the problem.

Denmark has had a relatively higher disease prevalence than in most other European countries. As a result, there has been a specific focus on the problem in Denmark. It is generally recognized that relatively low domestic hot water temperatures may have contributed to this. The low temperature allows the growth of Legionella, and the bacteria may spread to humans in small water particles (aerosols) from, e.g., showers. Approximately two-thirds of Danish homes - and the associ- ated domestic hot water - are heated with district heating. As for the rest of the households, heat pumps are gaining

Legionnaires’ disease is a severe form of pneumonia caused by the Legionella bacteria. According to ECDC (The European Center for Disease Prevention and Control), there has been an increase in Europe in the incidence and number of deaths from Legionnaires’ disease since the early 2000s. In 2022, the incidence rate per 100,000 inhabitants reached 2.6, com- pared to approximately 1.3 in 2005, as the graph below indi- cates. The significant growth in the incidence occurred around 2016-2018. Coinciding with the rise in incidence, there has been a corre- sponding increase in the number of deaths from Legionnaires’ disease in the EU/EEA. Deaths rose from around 350 in 2005 to nearly 800 in 2022.

Source: Graph showing the incidence per 100000 of Legionnaires' disease year 2006-2022

EUDP (Danish Energy Technology Development and Demonstration Programme) project “Legionella protection and energy efficiency for installations and supply” carried out from September 2020 to February 2023:

The project group:

Søren Anker Uldum, Statens Serum Institut (SSI)

Henrik Kjeldsen, Danish Technological Institute (project responsible)

Tommy Steen Møller, The Project office - Region Zealand

Kaj Bryder Danish Technological Institute (project responsible)

Leon Buhl, Danish Technological Institute (project responsible)

Nikas Arp-Wilhjelm, KAB

Hagbard Clausen, Danish Clean Water (DCW)

Ditte Andreasen Søborg, VIA University College

Torben Schifter-Holm, METRO THERM

Carl Hellmers, Fredericia Fjernvarme

ground to a considerable extent. Regarding energy efficiency and the possibilities of using alternative energy, both energy systems need to have water temperatures as low as possible. There is thus a significant temperature-related dilemma about ensuring Legionella-safe domestic water installations while simultaneously meeting the need to save energy, use renewable energy sources, and reduce the climate footprint. An interdisciplinary project co-financed by the EUDP (Danish Energy Technology Development and Demonstration Programme) has investigated this dilemma and pointed to some solutions. The diverse group of partners has included the Danish Tech- nological Institute and Statens Serum Institut (SSI, under the auspices of the Danish Ministry of Health). The project included partly a literature study on previous investigations and requirements for Legionella in domestic hot water and the derived energy consumption, partly developing and demonstrating three measures for control of Legionella in domestic hot water installations. These were, respectively, a tool for risk assessment of Legionella (Danish Technological Institute), an electric booster for monitoring and ensuring the necessary water temperature (METRO-THERM), and an innovative solution for biocide dosing (Danish Clean Water). Responsible partner is shown in brackets. Results from the literature study The study was based on a major literature search followed by contacts to selected knowledge and research centers. The

study included an examination of the influence parameters affecting the spread, growth, and reduction of Legionella, as well as of authority requirements, standards, and guidelines. The study showed that due to especially biofilm, the temperature requirements for controlling Legionella are often underestimated, and the Danish temperature requirements and practices are often challenging about Legionella. The study also leads to the following conclusions: It is generally agreed that Legionella pneumophila develops at temperatures higher than 20 - 25°C and lower than 45 - 50°C. The Legionella will die at 50°C and higher temperatures in the water. Due to, e.g., biofilm formation, it is at varying temperatures, however, often uncertain if the necessary temperatures have been obtained in the biofilm, although fulfilled for the water. An overall water temperature of 50°C or above will normally limit the Legionella content to the recommended max. 1,000 CFU/L (Colony Forming Units per Liter). However, these temperatures are particularly challenging for energy efficiency, climate footprint, and running costs as the necessary comfort requirement for the water temperature is only 45°C. Besides the water temperature and the biofilm, several other parameters impact the growth/reduction of Legionella, such as water flow conditions, water quality, pressure, and affected materials. However, the study showed that the knowledge of the conditions influencing the growth and reduction of Legionella is often relatively poorly founded or

Figure 1: Risk assessment for Legionella via review of the domestic water installation.

unclearly documented; e.g., it has not been clarified how temperature and flow conditions play a role together.

The new EU drinking water directive will increase the focus on Legionella as well as direct or indirect on the risk assessment of domestic water installations.

Nationally and internationally, there is relatively limited regulatory encouragement to search for alternatives to temperature protection against Legionella.

Due to the dilemma between protection against Legionella in domestic hot water and achieving high energy efficiency

Part of installation

Parameter influencing Legionella-associated risk

Severity for Legionella risk

Likelihood for occurrence in actual period (e.g. a year)

Controle procedure avoiding occurrence or mitigating risk

Risk-score contribution





Unit/ Component



Potential impact

Possible cause

Detection controle

Which parameter tobe investigated? Select from list

Which value assumes the parameter, compared to what is allowed to?

Potential effect in words and numbers?

Possible cause in words? Select from list/ Own assessment

Procedure for detection and control?

Risk-score contribution

Select from list/ Own assessment

Select from list / Own assessment

Select from list/ Own assessment

Legionella.spp; Measurements performed & Legionella detected

Moderate content of Legionella.spp.

From pumped drinking water

Cold-water supply








0 - 20 °C; Temperature OK No growth of Legionella





Cold-water supply


0 - 20 °C; Temperature OK No growth of Legionella





In periods 20 - 25 °C; temperature too high

Moderate risk of Legionella growth



Poor insulation





24 pcs. rarely-used tapping points at waste chutes

Dead ends or rarely-used pipes

Rarely-used cold-water pipe

Moderate risk of Legionella growth






Temperature prevents growth of Legionella Considerable risk of Legionella growth

Hot water supply


> 50 °C; Temperature OK





Often 45 - 50 °C; temperature low

Inappropriate type thermostatic valve



100% Non (will be replaced)



Water replacement often less than 1 times per day

Small risk of Legionella growth

Water flow


Insufficient pump capacity 100%




Figure 2: The risk assessment tool illustrating initial risk factor screening

installation (figure 1). These risk factors are assessed through a set of questions based on the identified impact parameters that significantly influence Legionella occurrence (figure 2). The assessment considers both the hot water installation, including possible circulation, and the drinking water supply itself; that means it recognizes the potential for Legionella growth in lukewarm water pipes above 20°C. An overall risk assessment is determined by adding up the risk factors identified during the overall review of the domestic water installation. The purpose of the risk assessment is to identify specific areas where Legionella risks are present and opportunities for improving the installations, and it also includes considera- tions for supplementary temperature and biocide treatment. Through subsequent activation of these options, the overall risk can be reduced. In a pilot version, the tool has been tested on practical domes- tic water installations at KAB, a large Danish housing company representing 70,000 homes. Several numbers of properties were inspected and assessed, with a comparison to Legionella analysis from samples. The risk analysis and tests showed crit- ical conditions for one of the installations. Implementing an improvement measure involved installing a biocide system with hypochlorous acid (see later).

3a) The electric booster under test in lab

Electric booster unit ensuring temperature monitoring and optimal control.

The electric booster unit ensures monitoring and optimal control of the temperature of the domestic water installa- tion based on knowledge of Legionella growth and reduction from the literature search. Also, it can give an alarm if some of the temperature requirements are below the limit values and thus reduces the risk of using the hot water installation. Furthermore, it conducts a thermal heat treatment of 60°C of the water producer and the circulation, if present, when the control has calculated that there is a theoretical possibility that the Legionella content has doubled.

Figure 3: The electric booster tested in the lab for domestic hot water circulation. 3b) Complete control with attached sensors and cables

and low climate footprints, it is essential to focus on all poten- tial improvement opportunities, just as new knowledge and insight into the problems must be ensured. Tool for Legionella risk assessment The developed tool is based on the widely recognized and used method FMEA (Failure Modes and Effects Analysis) for assessing risks and opportunities for improvement of technical facilities. It has been further adapted to include impact parameters related to Legionella in domestic water installations. The tool aims to provide a simplified approach to reviewing and improving both existing and new domestic water installations.

Fel tt est: Single family house




Disinfec ti on at temperature 63 °C, fl ow 1 L per minute and for 20 minutes for all taps

Electric booster






04.05.22 13.06.22 13.06.22 14.06.22 23.08.22

30.02.23 06.09.22 12.10.22 26.10.02 16.11.22 14.12.22

Tap 1 Køkkenvask

Tap 2 Håndvask

Rather than relying on statistically based risk analysis, the tool considers risk factors associated with each component of the

Figure 4: Demo results (field test) of electric booster for a non-circulated hot water system.

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