HOT|COOL NO. 2/2019 - "Smart Heating System Integration"

SURPLUS HEAT Many industrial enterprises have a challenge with surplus heat. The heat may originate from cooling or special processes. The heat is considered surplus when the enterprise cannot utilize it itself, and it often ends with the heat being cooled to the atmosphere or into a water source. At best this will be a waste of resources, but often flora and fauna in the recipient will suffer. And this really is a shame. We must stop considering surplus heat as a waste problem. For the enterprise's own sake and for the sake of the society, we must regard it as a resource. Heat, especially surplus heat, is a low-quality energy source. It is not only wasted in industrial plants, but also in the energy sector. Even today, many power plants waste maybe 60% of the production, which is transformed into heat and not power. The use of cogeneration technology can solve these problems if there is a districting heating network nearby. One of the benefits of the district heating and perhaps its primary raison d'être is the ability to utilize low-quality energy source.

NO. 2 /2019




Smart integration of energy and waste water

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THE COLUMN: SURPLUS HEAT By Bent Ole Gram Mortensen, Professor, University of Southern Denmark


FOCUS DIGITALISATION A KEY LEVER FOR LOW-TEMPERATURE DISTRICT HEATING By Steen Schelle Jensen, Head of Product Management – Heat/Cooling Solutions, Kamstrup


FOCUS SMART INTEGRATION OF ENERGY AND WASTE WATER By Hasmik Margaryan, Engineer, Taarnby district heating and cooling company; Anders Dyrelund, Senior Market Manager, Ramboll; Troels Hansen, Energy Engineer, Ramboll


FOCUS COOL AND SUSTAINABLE WITH ABSORPTION HEAT PUMPS By Lars Sønderby Nielsen, Managing Director, Enexio Solutions


FOCUS CAN SMART CITIES HEAT THEMSELVES? By Kristina Lygnerud (PhD), Energy department manager at the Swedish Environment Research Institute (IVL)


FOCUS NEW MANAGEMENT SYSTEM FOR DHC NETWORKS By Dirk Vanhoudt, senior researcher district heating and cooling networks, EnergyVille – VITO, Belgium; Tijs Van Oevelen, researcher district heating and cooling networks, EnergyVille – VITO, Belgium; Christian Johansson, CTO, NODA, Sweden




MEETING THE STRATEGIC CHALLENGES OF UK DISTRICT HEATING By Professor Janette Webb and Dr Ruth Bush, Heat and the City, University of Edinburgh


THE LAST INVESTMENT CYCLE By Lars Andersen, CEO, Geotermisk Operatørselskab A/S



Front page: Energy plant in Bjerringbro, a partnership between Grundfos and the consumer-owned district heating company Gudenådalens Energiselskab. The heat pumps supply cooling to Grundfos Campus and heat to the district heating system in combination with ground source cooling.

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Green business and black numbers

Digitalisation is the lever for an integrated and efficient energy system with district heating as its natural cornerstone. It even delivers measurable results of energy efficiency and optimised operations.

Extra capacity?

Heat loss


Leak in building

Data-driven temperature optimisation



High return temperature

Improved customer service

Poor cooling

Peak load limitation

Low forward temperature

Misadjusted installation

Let us – just for a second – put aside the fact that digitalising district heating will enable a greener, more integrated energy system utilising renewable energy sources and surplus heat to decarbonise the heating of buildings. Digitalisation is also simply good business. The total savings potential from digitalisation in the Danish utility sector is estimated at between 360 million and 1.3 billion euros. These savings will come from using data-based transparency to reduce losses, increase operational efficiency, improve utilisation and maintenance of the distribution network as well as streamline the heavy investments in this area.

We are now beginning to see realisations of a data-driven approach to district heating supply. For example in Assens, Denmark initial steps towards digitalisation has made the utility far more energy efficient and realised savings of EUR 33 per end consumer – and that is just the beginning! There is no shortcut to realising this potential – and it will not happen automatically. For district heating utilities, reaping the financial benefits from digitalisation is a process that begins with them investing both their time and money in digital tools that enable them to change the way they do things today.

Read about the realised benefits of digitalisation


By Bent Ole Gram Mortensen, Professor, University of Southern Denmark

SURPLUS HEAT Many industrial enterprises have a challenge with surplus heat. The heat may originate from cooling or special processes. The heat is considered surplus when the enterprise cannot utilize it itself, and it often ends with the heat being cooled to the atmosphere or into a water source. At best this will be a waste of resources, but often flora and fauna in the recipient will suffer. And this really is a shame. We must stop considering surplus heat as a waste problem. For the enterprise's own sake and for the sake of the society, we must regard it as a resource.

It is important that the legislators observe the potential of the exploitation of surplus heat. E.g. an inappropriately designed tax system can destroy the incentives to have the surplus heat utilized. This has been debated in Denmark, where the government on the one hand would like to reduce the use of fossil fuels, and on the other hand fear the loss of fiscal revenue, if the use of the highly taxed fossil fuels is reduced. At a time when we are talking about circular economy, climate change and renewable energy, the legislator's task is to establish framework conditions that ensure optimal utilization of the surplus heat. For the industrial enterprise, the possibility of being able to utilize its surplus heat makes a difference. For some enterprises, the green image is essential, and the possibility for utilizing surplus heat may be crucial for where the next production plant is located. In fact, there are enterprises that are willing to give away for free the surplus heat, if it can be utilized. For other enterprises, the economic contribution from sales of surplus heat may be an element, which makes it possible to maintain a production facility rather than being outperformed by plants in places where wages and environmental costs are lower. Of course, there will be different interests, respectively, from the industrial enterprises and the district heating companies. Among other things, investment for the sake of utilizing and the price of surplus heat must be considered. Inspiration can be found in a pricing model that a district heating company in the vicinity of Copenhagen (VEKS) has entered into with an industrial enterprise. Here, the parties share the benefits that come from the utilization of the cheap surplus heat compared to the alternative costs of producing the same amount of heat using fuel. The industrial company receives the full benefit of the surplus heat project until their project-related investments have been repaid. Afterwards, VEKS receives the entire gain until their investment is repaid. After the investments of both parties have been repaid, the parties divide the profit by utilizing the cheap surplus heat for the common good.

Heat, especially surplus heat, is a low-quality energy source. It is not only wasted in industrial plants, but also in the energy sector. Even today, many power plants waste maybe 60% of the production, which is transformed into heat and not power. The use of cogeneration technology can solve these problems if there is a districting heating network nearby. One of the benefits of the district heating and perhaps its primary raison d'être is the ability to utilize low-quality energy source. One of the sources of surplus heat comes from data centers. It is a growing business. Both businesswise and as citizens we use more and more data connections and storage space in the "cloud". The servers in the required data centers must be cooled and thus surplus heat arises. There are several considerations that are crucial when determining the location of these data centers. It is optimal if the location decision also can include the possibility of utilizing the surplus heat. In some places, such placement can be facilitated through planning law. Elsewhere, it is the parties' mutual interest in exploiting the surplus heat that will carry the project. Who else than the district heating sector can at present utilize surplus heat from data centers? When I, as a professor of environmental and energy law, see a resource that is wasted, my first thought is whether there is anything in the legislation that is problematic. Are sufficient incentives given for the individual market players to perform also socioeconomical optimally? Is there even a barrier to this?


5-10% reduction of heat loss in the district energy network

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By Steen Schelle Jensen, Head of Product Management – Heat/Cooling Solutions, Kamstrup

The district heating system of the future is characterised by high efficiency and low temperatures enabling integration of green and sustainable energy sources. International regulatory frameworks are paving the way but making it a reality is in the hands of utilities and their customers. Digitalisation is part of the solution. From all levels of the district energy sector there is a clear consensus that the decarbonisation of Europe’s energy supply relies on the expansion of district heating as well as increasing the share of renewable energy and waste heat. This includes energy generated from fluctuating sources like solar and wind as well as waste heat e.g. from industry, data centres and super markets, which the district heating system can utilise and store. The regulatory framework promoting these changes is already in place as part of the EU’s Clean Energy Package including the Energy Efficiency Directive (EED) and the Renewable Energy Directive (RED). THE CLEAN ENERGY PACKAGE According to Article 14 and 15 of the Energy Efficiency Directive, member states must perform comprehensive assessments to evaluate the potential for implementing more district heating. And Article 23 in the new Renewable Energy Directive stipulates that they must endeavour to increase the share of renewables and waste heat in district heating by 1.3% each year.

Today, buildings account for half of the total energy consumption in Europe and are still largely fossil fuelled. Expanding the use of sustainable district heating and optimising the energy performance of buildings are therefore critical components in the green transition. This makes network temperatures a key factor. LOWER TEMPERATURES = HIGHER EFFICIENCY Integrating more green energy into the district heating system requires utilities to lower temperatures in the network – both flow and return temperatures. As an example, the lower your flow temperature, themore waste heat you can utilise in your system. While some waste heat has a high enough temperature to go directly into the district heating system, most of it does not reach the temperature levels of traditional heat sources, which means heat pumps are necessary to raise the temperature. And the lower return temperatures you get into your heat pump – which could be powered by renewable energy – the more efficient it will be. An average utility’s cost curve (Figure 1) shows that in addition to benefitting the environment there are also significant financial savings to be made from lower temperatures, e.g. through reduced heat loss, pumping costs and more efficient production. But while the advantages of lowering temperatures are well-known, it remains a complex task. However, today’s technology has now reached a point where it can support utilities in their temperature optimisation by making it more streamlined and data-driven.



OPTIMISING FLOW TEMPERATURES The utility itself controls and manages the flow temperature from the production side. The challenge here is knowing the actual heat demand and operating conditions to avoid or reduce safety margins and run production as close to the limit as possible while still meeting their customers’ comfort level. Traditionally, flow temperatures have been based on theoretic models or a limited number of carefully selected critical points. But with the rollout of remotely read smart meters, which is now required with the revised EED directive, comes the opportunity for utilities to both base and validate decisions on a much higher number of measurements.

delivery quality, but the tool showed that they were no longer necessary. As a result, this utility was able to lower the return temperature in the entire network by almost 2 degrees C resulting in significant savings. Another crucial element is the end users’ heat installations. Often, these have been installed incorrectly, are faulty in some way, or conditions may simply have changed leaving them no longer optimised for a particular building or purpose. In single- family houses, fixing the problem will be the home owner’s responsibility, where as a professional, e.g. a plumber, will be called for apartment blocks, commercial buildings etc. The challenge this poses for most utilities is that while their responsibility ends on the primary side of the installation, it is

very much affected by what happens on the secondary side – but neither home owners nor plumbers have the overall performance of the district heating system as their primary focus, and this is reflected in their behaviour, i.e. their approach to optimisation. MOTIVATION FOR CHANGE Behavioural changes can be triggered through different stimuli. If the incentive is strong enough, a person will change a certain behaviour even if it is hard to do. Many initiatives have been made in recent years to give end users access to their own consumption data, expecting that this insight would prompt them to e.g. improve their energy behaviour or heat installation. But in practice, this has proven difficult as most people seem to not have enough interest in energy consumption.

Figure 1

As an example, the analytics platform Heat Intelligence enables utilities to see what goes on underground in their supply area. Combining smart meter data with a GIS model of their pipe network, the tool calculates how heat travels through the distribution network and creates a digital twin of exactly that. This transparency allows utilities to see the consequences of their temperature optimisation. There is a huge potential in data-driven algorithms for optimising flow temperatures. Some of our Danish customers succeeded in lowering their flow temperature by 6-8 degrees C based on their efforts working with data from their meter reading solution. OPTIMISING RETURN TEMPERATURES Lowering return temperatures is less straightforward because they not only depend on what happens in the distribution network but are also closely linked to what goes on inside the buildings. Smart meter data and analytics help utilities identify conditions – both inside and outside – that can be optimised. Using Heat Intelligence, one of our customers was able to remove several bypasses in their distribution network. They had originally been placed in certain areas to ensure a satisfactory

For example, motivational tariffs either rewarding or punishing end users based on e.g. return temperatures are often inefficient, because the size of a potential penalty or reward is too small compared to their total heat bill and the hassle of uncovering the actual problem. For a plumber called out to fix a building’s heat installation, the main barrier will often be limited knowledge of the root cause of the problem hindering them from making the link to the best long-term solution for the utility. The result will therefore often be a quick fix that solves the issue at hand but may have a negative effect on the overall heat system. In a joint project with one of our customers, we are exploring the idea that making heat installation optimisation easier to do will be more effective – which matches the Fogg behaviour model on how to successfully trigger behavioural changes. In other words, rather than increasing the reward for making a certain change, we want to improve the easiness and convenience of making it.

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heat installations. Their assumption is that by comparing data from these two sources they may, through machine learning, be able to predict what will happen on the secondary side. This is a great example of the fact that because this area is still unchartered territory, asking questions and testing assumptions is the necessary way for a utility to go. It also highlights the need for utilities to use their expertise and data to take more responsibility by providing the framework to better guide end users and plumbers to make the right decisions.


In addition to enabling temperature optimisation, smart meter data, data from additional sensors and advanced analytics also unlock new opportunities for e.g. pressure optimisation.

Figure 2

As with network temperatures, detailed insight into where the network pressure is either higher or lower than necessary will lead to more efficient use of time, resources and energy. As an example, if the digital twin of a utility’s distribution network could show not only temperature levels, but also calculate and show pressure levels, utilities would have full transparency on the two parameters they require to deliver district heating in the most efficient way possible. We are working on models that can assist utilities in making exactly that evaluation, and we have already seen very positive results. It is also worth mentioning, that the optimisation potential mentioned above relates only to the operations side (OPEX). Because of its both cost-intensive and time-consuming nature, the investment and asset management side (CAPEX), which includes infrastructure expansion and lifetime costs, may hold an even bigger savings potential through data-driven optimisation. In other words, not only is digitalisation necessary to create the right conditions for low-temperature district heating and the integration of sustainable energy sources in a green energy future. It also delivers black numbers and increased competitiveness for district heating utilities.

Increasing easiness could be done through data-driven decision support for both end users and professionals in the form of a tool that makes it easier to find both the cause, location and solution to a given problem. This could include using smart meter data to identify e.g. the 10 most common heat installation errors and possible solutions. However, that will require scalability and continuous monitoring. LARGE-SCALE BIG DATA First of all, the way data is used by utilities has to be more scalable. Utility experts should not be the only ones able to decode data and graphs to find and fix the most typical issues. These conclusions must also be made available to home owners and plumbers. Errors could be wrong dimensioning, faulty or worn out components, but often it is a question of making simple adjustments. What is complex is finding the cause and solution – especially for those looking at pipes rather than a computer screen. That takes the right data, delivered at the right time in the right format. Secondly, fixing a specific problem and adjusting a heat installation based on current conditions will only last so long, as those conditions will change over time. Continuous monitoring will help utilities detect changes that will negatively affect the performance of the installation. This calls for digitalisation and machine learning from the large amount of smart meter data available to make this process automated and dynamic. In the project mentioned above, our customer often sees cases where the installation performance varies significantly in both old installations and new ones that should theoretically outperform the former. They are therefore now testing their idea to supplement energy meters on the primary side with additional temperature sensors on the secondary side to get even more information about what actually goes on in the

Steen Schelle Jensen, For further information please contact:




By Hasmik Margaryan, Engineer, Taarnby district heating and cooling company; Anders Dyrelund, Senior Market Manager, Ramboll, Troels Hansen, Energy Engineer, Ramboll

Taarnby Forsyning, TF, is a municipality-owned public utility company that takes care of the municipal services: water, waste water, district heating and the newest addition of district cooling. TF exists for the benefit of residents and companies in the municipality and now also includes companies that have a cooling demand. In 2019, TF is going to establish one of the most spectacular energy plants integrating the energy system and waste water. The project demonstrates the symbiosis between district heating, district cooling, electricity, waste water and ground water for smart integration of fluctuating renewable energy like wind energy. In 1980, the utility’s, only activities concerned water and waste water, and all heating was based on individual oil boilers in the municipality of Taarnby, a suburb of Copenhagen with a population of 43,000. Encouraged by the national energy policy, TF established a new business for district heating, and the municipality took part in the formation of the district heating transmission company CTR, with the purpose of establishing district heating based on CHP and residential waste in a cost-effective way. At the same time, the municipality joined the new regional gas company. In the heat planning process, the district heating and the natural gas infrastructure competed, and the heat market was divided between district heating and gas in a cost-effective way. Thus, since 1985, this new district heating unit has supplied around 60% of the heat demand to mainly large buildings in the municipality, including Copenhagen Airport, based on efficient low carbon heat from CTR. CTR is one of the two transmission companies in the Greater Copenhagen district heating system, which owns and operates the heat transmission system and optimises the heat production from the most cost-effective plants available, including biomass CHP plants with large heat storage tanks, waste incineration CHP plants and peak load boiler plants. This district heating system is a landmark for smart integration of the energy system, including electricity, waste, district heating and natural gas. KARA/NOVEREN








Copenhagen Airport



Figure 1: Map of Greater Copenhagen district heating and Taarnby municipality

Based on a screening of the potential for district cooling in Taarnby along with a business plan, TF decided that it was feasible to establish the new district cooling business unit. The new unit will service the new urban development area north of the airport. The business plan showed that it would be profitable to establish traditional district cooling based on central electric chillers and a chilled water storage tank compared to local individual building level chillers. The business plan also proved that the profitability would become even better by installing a large-scale electric heat pump in combination with ground source cooling, Aquifer Thermal Energy Storage (ATES), instead of traditional chillers, benefitting from the symbiosis between district heating and district cooling through co-production of heating and cooling. 10 km The cooling demand is mainly present in the summer; thus, the heat production in winter is limited unless another heat source is identified. The waste water turned out to be very profitable in terms of using the surplus cooling capacity of the heat pump to cool the waste water and thereby generate heat. There was a good match between the capacity of the heat pump, designed for cooling, and the potential of heat capacity using the waste water as heat source. Waste-to-ene gy plant District cooling plant CHP station Peak load plant Transmission pipeline CTR + HOFOR VEKS Vestforbrænding Other Heat supply areas:

Køge Kraftvarmeværk

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The schematic cold duration curve below illustrates the production of district cooling in combination with ATES (including a warm and a cold well) and waste water. The cold well (dark green) is base load cooling in summer heating up the warm well, whereas the heat pump is peak load in combined production with heating (grey). Moreover, the heat pump generates process cooling in combined production with heat as first priority. (grey). The heat pump must, to comply with Danish legislation, cool down the ground water in winter (dark blue). Thereafter the heat pump is available for the rest of the year to “cool” the treated waste water or rather to extract heat (light green). Heat from combined production of heat and cold, directly or via ATES, is very efficient corresponding to a COP factor of 5.6. It will in general be more cost effective than heat from the CHP plants, whereas heat from waste water “only” has a COP factor of 3.4. Heat pump- Combined heating & cooling Heat pump- Cooling ground water 10 9 8 7 6 MW COLD

Moreover, as the heat production cost in the summer period is very low in the heat transmission system, it turned out to be profitable to establish ground source cooling in combination with the heat pump and thereby store cold water from winter to summer and supplement the heat from the waste water with heated ground water in winter (ATES). In this way, the project adds district cooling, waste water and ground water to be part of the integrated energy system in Copenhagen. As the heat pump installation is connected to both a chilled water tank, ground source cooling and the district heating system, it is possible to optimise the production with respect to both electricity prices and the alternative heat production cost of all plants that produce heat to the Greater Copenhagen district heating system.

Heat pump



Finally, it turned out that there was available space at the existing waste water treatment plant for the construction of the chilled water tank and the heat pump energy centre. This symbiosis is another good reason for organising all municipal services into one municipality-owned organisation that operates in the interest of the local community. As the heat pump is expected to operate with more than 6,000 max load hours and having a 10 kV cable close to the plant, it proved to be profitable for TF to connect to the high voltage grid and invest in transformers and thus establish a small “micro power grid at the waste water treatment plant” owned by TF. Heat pump Hours 0 Winter


Heat pump- Cooling waste water







Ground source cooling

Heat pump- Combined heating & cooling





Heat pump- Cooling ground water 1

Peak from storage tank



Heat pump- Combined heating & c



8760 Summer

Heat pump- Cooling waste water

Heat pump- Cooling ground wa



Heat pump



Ground source cooling

Heat pump- Cooling waste wa


Figure 2 shows the district cooling area and the waste water treatment plant.



Ground source coo

Peak from storage tank




8760 Summer

0 Winter

Peak from storage t



8760 Summer

0 Winter

Figure 3: Schematic duration curve of the generation of cold energy.

As there are other heat sources and heat storage tanks in the district heating system, the heat production from waste water will be optimized considering the electricity price and the value of the heat in the Greater Copenhagen district heating system. It will e.g. typically not generate heat in case of large electricity prices due to lack of wind energy (intermittent operation in light green area).

Heat Pump Installation

2000 m3 chillet water tank

Energy Centre District Cooling Phase 1 District Cooling Phase 2 Waste Water Piping District Heating Existing District Heating








Figure 2: Map of the district cooling system in Taarnby.




Stage 2 11 170

ADDITIONAL INFORMATION Number of buildings Floor area in total ENERGY Cooling demand Cooling capacity demand Expected capacity to network Heat pumps cold Stoage tank capacity Ground source cooling Total installed cooling Heat pumps heat Heat from combined H&C

Stage 1 3 55

no m2

In addition to the cost-effective integration and optimisation with respect to the electricity price and thereby integration of fluctuating wind energy, there are several additional environmental aspects of the project for the community as well as for the consumers: • The district cooling plant for combined heating and cooling will, as shown in the picture above, be located at the waste water treatment plant and therefore it will not occupy valuable space in the urban development area. • A roof has been established to cover the water basins to prevent environmental impact of bad smell from the untreated waste water in the neighbourhood. This is why it has been possible to establish new buildings close to the plant and thereby benefit from the symbiosis between cooling and waste water. • To reduce the noise level, from the heat pumps to a low level for residential areas, special precautions will be taken, and the building will be covered in green vegetation. • The generation of heat from the treated waste water will reduce the temperature and improve the dispersion in the sea water. • There will be no visible or noisy installations on the rooftops of the cooling client’s buildings, it is planned to use the roof space of one of the buildings for a rooftop café and there will be no refrigerants and vibrations in the basements of the buildings. To conclude on the environmental aspects: this project demonstrates that smart cities have smart “backyards” in which there is a symbiosis between infrastructure for energy and environment to the benefit of the local community. ADDITIONAL TECHNICAL ASPECTS Besides the optimisation of the technical system design, there have been some interesting technical aspects under consideration, e.g.: • District cooling could be based on water technology (e.g. plastic HDPE pipes and underground concrete storage tanks) or district heating technology (steel pipes and tanks using the same water quality as for district heating). For this project we have chosen the district heating technology as it can be combined with: a steel tank (which is the best solution for storage in this project), leak detection in the preinsulated cooling pipe system, efficient insulation of the pipes (due to short distance between district heating and cooling pipes), direct connection of the consumers (to reduce temperature drop) is an option. • The supply temperature and required return temperature for comfort cooling must be 10/15 for new buildings in accordance with the Danish building code, but it has been considered to meet the request of the largest consumer to offer a slightly lower temperature for process cooling.

9 10.2

3.5 4.3 4.3 4.3 1.2 0 1.2 6.7 4


9.2 4.6 2.5 2.0 9.2 6.7

11 39 50

41 45

Heat from waste water Total heat generation INVESTMENTS Building Ground source cooling Heat pump Waste water heat exch.

4 9 41 2 4 14 5 3 80

4 0 38 2 4 10

Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK Mill.DKK %

2 3 62 Chilled water tank District cooling grid Consumer connections Connection to DH network Total investmetns NPV BENEFIT, INCLUDING ENVIRONMENTAL COSTS Society of Denmark District cooling business Consumers Internal rate of return 60 17 5 13

103 52 8 41

Figure 4. Basic infomation on the technical and economical data

PARALLEL PROCESSING The planning of the project has been a challenge as the largest cooling client had a deadline for cooling. From the day that TF decided to pursue the project, we had several critical activities concurrently: • Negotiation with the clients, the heat transmission company CTR and the banks. • Updating the feasibility study for design concept, location, trench, temperatures, sales revenues, taxes and value of the heat. • Formation of a business unit for district cooling. • Application to the city council and the Energy Agency for approval in accordance with the Heat Supply Act.

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CONSTRUCTION WORK STARTED A public tender has been produced for four separate components: the district heating and cooling network, the building construction, the steel tank and the heat pump installation. The offers have been within the estimated budget, and the construction work started on 16th of May 2019. CONCLUSION This project demonstrates the benefits of local democratic ownership of all assets for energy and environment in the local community. This ownership serving the interest of all inhabitants and companies in the municipality opens for co-operation –

• The system has been prepared for additional capacity in a flexible and cost-effective way, by increasing peak from the storage tank, by investing in ground source cooling and by preparing the system for a mobile temporary chiller. • To avoid digging in an important road, a 160 m trench in DN300 for the cooling pipe and DN200 for the heating pipes was constructed with the nodig trench method as an alternative to a longer route. (See picture above.) • How to connect to the power grid: TF could buy low voltage power from a transformer, but TF decided to be owner of the new transformer and buy electricity directly from the high voltage grid.

the so-called “collective impact” – and transparent exchange of information and data among all stakeholders. Thereby it has been possible to identify the important economy of scale factors, synergies and local resources to optimize this smart integration to the benefit of the consumers. Since TF really started this journey in 1985, we have used digital simulation models and data, which have been necessary for optimal planning and operation, but this has just been tools. The important thing is the open cross-sector co- operation, which has enabled Taarnby Municipality to implement smart solutions, as if the local community was one large campus. We hope this project will inspire ministries, cities, utilities and large energy consumers in Denmark and internationally.


isoplus Piping Systems is a leading manufacturer within pre-insulated piping systems with low heat loss for district heating and cooling. Low heat loss guarantees low running costs throughout the entire service life of your pipe network. The environment also benefits from reduced CO 2 emissions. Innovation and quality are keys in both our products and the service we provide, which spans from project optimiza- tion, pipe drawings and plans for leak detection to the training of joint fitters and supervisors. With 9 factories we provide the widest range of products and components in the industry; and for more than 30 years. Our steel and flexible pipe systems are delivered in accordance with the norms and demands of the industry and we have considerable expertise in meeting interna- tional as well as national standards.

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please contact:

Anders Dyrelund,

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By Lars Sønderby Nielsen, Managing Director, Enexio Solutions

Absorption technology offers a sustainable and well proven technology for district heating and cooling. With water as natural refrigerant, the technology offers GWP (global warming potential) value at 0 and a low CAPEX (capital expenditure) that gives a favourable payback period. Large heat pumps are a key in the green transition of district energy. The overall value of heat pumps is that they can utilize waste energy at low temperatures for usable energy at a higher temperature. Key challenges for all heat pump projects are to identify adequate low temperature heat sources and at the same time to ensure that the necessary energy source for operating the heat pumps is sufficiently sustainable. In addition, the legal frameworks and market demand are increasingly pushing for natural refrigerants. WHY THERMAL DRIVEN HEAT PUMPS? As an alternative to compressor driven heat pumps, absorption heat pumps and chillers offer several features that are attractive for district heating projects. The machine is ideal for utilising heat at low temperatures, thus recovering energy that would otherwise be wasted. Unlike a conventional heat pump, the absorption heat pump is fuelled by thermal energy, resulting in minimal electricity consumption and very low operating costs. In a heating plant, the necessary thermal heat source is often "freely" available since the heat used in the absorption pump is delivered back to the district heating system. The machine uses water as refrigerant, which means that the GWP value is practically zero. The technology is mature and well-proven, with hundreds of thousands of commercial installations worldwide. PROVEN TECHNOLOGY An absorption heat pump basically consists of 4 large heat exchangers, which together act as a thermal heat pump. The machine uses water as a refrigerant and a salt (LiBr) to absorb water vapour at low pressure. The fundamental working principle is that the refrigerant water evaporates in vacuum (0.8 kPa) and removes heat from the low temperature energy source. A LiBr solution mixture absorbs the refrigerant vapor and maintains the necessary low pressure in the evaporator chamber. This solution is then pumped to the generator where the refrigerant is revaporized using a high temperature heat source. The refrigerant-depleted solution is then returned to the absorber via a throttling device.

Figure 1. Operating principle of an absorption heat pump and chiller

MULTIPLE APPLICATIONS Heat pumps increase efficiency and improve the economy regardless of the type of production plant and available fuel. When establishing large solar heating systems, absorption heat pumps are used to cool the district heating return from the consumers before being sent back to solar panels and seasonal storage. The absorption heat pump can also be used to utilize surplus heat from nearby industry or data centres. In the Danish market, the current most common application is for flue gas condensation in biomass and waste incineration plants, where the driving energy for the heat source is freely available. Future development of geothermal energy sources is also expected to include absorption heat pumps for upgrading ground sources temperatures to applicable district energy levels. COP IS NOT ALWAYS THE MOST IMPORTANT FACTOR The heat pump COP is a measurement of efficiency and thus always to be considered. For practical applications, the heating COP (COP = heat output/heat source input) is equal to 1.7 for absorption heat pump applications. In direct comparison, this COP is low compared to mechanical chillers. Nonetheless, absorption can substantially reduce operating costs because they can be driven by low-grade surplus heat.

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In a heating plant, the heat source energy can often be found as hot water from existing boiler installations. In such case, the heat source energy is in principle “free”, since the energy used for the absorption process is fully returned to the district heating system, only at lower temperature. In such cases, the heating COP is less important. Focus should rather be on exploiting the low temperature energy source to its maximum.

Figure 4: Jægerspris Kraftvarme in Denmark has installed 3 MW absorption cooling for increasing the efficiency of its solar heating plant.

DISTRICT COOLING Using absorption for district cooling purposes is the ideal way of upgrading low quality waste heat in the summer period. The operation principle of an absorption chiller is the same as for an absorption heat pump, only with the difference that it is the chilled water from the evaporator of the machine that is utilised and distributed to the consumers. When working as a chiller only, the energy from the absorber/condenser circuit is deposited in a cooling tower. District cooling is largely used already in for example Sweden, Finland, Germany and France. In Gothenburg, Sweden, for example, absorption chillers are widely used for district cooling purposes, converting surplus heat from waste incineration at typically 90°C to district cooling that can be delivered at 6°C to commercial building connected to the cooling network of the city.

Figure 2: The new biomass fired District Heating plant in Grenaa, Denmark, with a boiler capacity of 2 x 15 MW has installed 2 absorption heat pumps for flue gas condensation each providing additionally 2 MW heat.

FLUE GAS CONDENSATION For energy efficient district heating boilers, the first step is to install adequate economizers to cool down the flue gas and extract most possible energy. However, this will only cool down the flue gas to a few degrees above the district heating return temperature, meaning that a large amount of energy is wasted and discharged through the stack, often at about 50 °C or more. With an absorption heat pump, the flue gas can be cooled down to temperatures typically below 20 °C and in the best case all the way down to 10 °C, which means that the last residue of available energy can be used in the district heating.

Figure 5: Göteborg Energi in Gotenborg operates a large district cooling network, where 3 absorption chillers contribute with 12 MW cooling.

Figure 3: Basic energy balance in an absorption heat pump used for flue gas condensation

COMBINED HEATING AND COOLING SOLUTIONS If there is a simultaneous heating requirement, the chilled water circuit of the evaporator can be used for cooling at the same time as the absorber/condenser circuit is used for heating. An example of such a solution has recently been installed at the new University Hospital, DNU, in Aarhus, Denmark, where an absorption chiller delivers 3 MW of cooling to the hospital’s new centre for particle therapy. During summer operation, the waste heat is disposed of in cooling towers, while the waste heat in winter can be utilised for heating in the hospital’s local district heating network. The absorption chiller is powered by hot water at 105°C from the district heating transmission network. This converts 4.3 MW heat to 3 MW cooling and 7.3 MW district heating, which are used simultaneously.

SUMMER UTILISATION WITH SOLAR AND WASTE HEAT While many boiler installations with auxiliary heat pumps are out of operation in the warm summer period, absorption still finds its place with both solar heating and district cooling installations. For solar heating plants, absorption heat pumps can be used for optimisation of the solar field output. This is done by cooling of the district heating return temperature before it is reheated by the solar field heat exchangers. Such installations can yield up to 30% of increased performance from the solar panels. The feasibility of course needs to carefully examine the nature and cost of the thermal heat source required for the process.



(unusual) warm summer of 2018, the heat price for operating the absorption chiller generator varied between 0 and 20 EUR/ MWh, whilst the electricity price saw big variations with an average of 190 EUR/MWh. Such a price scheme would give an advantage for absorption over mechanical cooling, despite the higher COP of the compression chillers. In cooling seasons to come, the input energy prices and resulting operation priorities may be opposite. But all together, the combined system forms a robust solution for the future. CONCLUSION Absorption heat pumps and chillers can play a key role in sustainable and flexible energy system. Absorption technology is ideal for utilizing heat at low temperatures, thus recovering energy that would otherwise be wasted. Unlike a conventional heat pump, the absorption heat pump is fueled by thermal energy, which means minimal electricity consumption and very low operating costs. An absorption heat pump is characterized by a minimal electricity consumption and low operating costs. Thus, the prerequisites for the investment are very robust, and payback times of less than 3 years can typically be achieved.

Figure 6: The new University Hospital DNU in Aarhus, Denmark has 3 MW absorption cooling installed, from which 7 MW of waste heat is reused for heating.

FLEXIBILITY OF FUEL The absorption chiller at DNU is installed in conjunction with mechanical cooling from compressor chillers. This is a big advantage for continuous cost optimization of the cooling plant. Heat prices as well as electricity prices may vary substantially during summer, depending on market spot prices. With both absorption and mechanical cooling capacity installed, production can be planned according to energy prices. In the

Lars Sønderby Nielsen, For further information please contact:

NIRAS Energy Private as well as public investors prefer NIRAS’ international experience within district heating and biogas plants. This applies to both renovation of existing plants and establishment of new plants. We provide expert consulting through- out the entire process – from business plan and authority approvals to design and tender documents. We supervise the construction phase and during commissioning.

Expert consulting – all the way from idea to commissioning PURE ENERGY

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By Kristina Lygnerud (PhD), Energy department manager at the Swedish Environment Research Institute (IVL) and researcher focusing on business model innovation in district heating at Halmstad University (HU)

Urban waste heat recovery is a key to smart cities but to get there, many challenges need to be managed. The industry needs to go beyond its tradition of technical orientation and grasp the window of opportunity of the low temperature heat recovery. The opportunity allows the companies stepping over the threshold of technology to capitalize on the value of green and long-term customer relationships. Heating and cooling are important players on the European energy scene. Approximately half of the final energy is consumed by these sectors. Even so, the sector is challenged and needs to be modernized to be part of the future, smart city. One challenge is the increasing energy efficiency of the building stock. Another challenge is the changing customer demand. Customers see an optimized energy consumption as being the responsibility of their energy provider and they want the possibility to generate and sell energy on a heat market. Indeed, the energy citizen who is a prosumer is materializing. Yet another challenge is the competitive pressure from other heating alternatives (notably gas on the European continent and heat pumps in the Nordics). In the light of challenge, it is important to identify new ways to undertake business. INTEGRATION WITH THE URBAN ENERGY SYSTEM One way is to become smarter, becoming an integrated part of the urban energy system. Today, approximately one fifth of the fuels used in district heating are renewable. One efficient pathway to go fossil free is to recover waste heat. In European district heating networks, 9% of the heat comes from waste heat sources. These are predominantly high tempered originating from industry, the potential of industrial waste heat in Europe can be as high as 2.7 EJ/year. There is however, a growing interest for recovering low temperature heat sources into district heating. Those sources are really smart since they are both local (reducing the transport costs and CO2 emissions from fuel transport) and fossil free (being the result of people living and moving around in cities).

In combination with heat pumps, the low tempered sources found in cities, the urban waste heat, can be an important heat resource in the future fuel mix of district heating. Low temperature heat recovery is gaining attention and an ongoing project under the IEA-DHC framework (the TS2 project on 4th generation implementation found at confirms that there is a low temperature district heating trend. To date, the project has identified over 100 low temperature district heating installations across Europe. In another project, the Reuseheat project (H2020 found at specifically targeting urban waste heat recovery the potential of four urban waste heat sources has been quantified. In the project, four urban heat sources are addressed (heat from metro systems, computer centers, service sector buildings and sewage water). The combined, brute potential of these sources has been assessed to be 1,562.5 PJ/year. SHIFTS IN DISTRICT HEATING GENERATIONS That there have been several district heating generations is known, and the shift from 3rd (current technology) to low temperature installations (4th: low temperature and 5th: ultra- low temperatures) is a nascent paradigm shift. There are many advantages from using the low temperature heat sources. Lower distribution losses and integration of renewables such as solar and geothermal heat have been addressed as explicit advantages. In the Reuseheat project, the low temperature heat sources and their potential to decarbonize Europe are explicit. In a survey addressing five stakeholder groups (policy makers, investors, district heating operators, owners of waste heat and end customers) in eight European countries (Sweden, Denmark, Germany, Belgium, Romania, Spain, France and Italy), it is confirmed that there is an interest in low temperature heat installations amongst all five stakeholder groups. Advantages mentioned are, apart from the distribution costs and increased efficiency of solar heating, a lower need for district heating companies to reinvest in central production units. Instead, the decentralized heat installations can be a more cost-efficient alternative.


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