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. 6 / 2024
INTERNATIONAL MAGAZINE ON DISTRICT HEATING AND COOLING
ENERGY STORAGE
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Contents
THIS EDITION'S FOCUS THEMES
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ENERGY STORAGE
PREFACE ENERGY STORAGE
LARGE THERMAL ENERGY STORAGE (LTES) WILL HELP SHAPE THE FUTURE ENERGY
LANDSCAPE By Geoffroy Gauthier
HEAT SOURCES
By Oddgeir Gudmundsson and Jan Eric Thorsen 10
WASTE HEAT —THE OVERLOOKED RESOURCE WAITING TO BE HARNESSED
ELECTRIC NETWORKS
By Niels Hansen 14
LOW-TEMPERATURE DISTRICT HEATING FOR OLD AND NEW BUILDINGS
By John Tang Jensen 18
VALUE OF DISTRICT HEATING HEAT SOURCE DESIGN AND STORAGE
LOW-TEMPERATURE DISTRICT HEATING
ELECTRIFICATION OF SPACE HEATING By Lars Gullev, Hanne Kortegaard Støchkel and Jesper Koch 26
Magazine Cover Photo: Heat Storage in Rostock, Germany
To supply the Hanseatic city and the surrounding region, a 55-meter- high heat storage tank in the northwest of Rostock stores 45 million liters of hot water. Photo by Morten Jordt Duedahl, Business Development Manager, DBDH
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, kaare@68design.dk
Coordinating Editor: Linda Bertelsen, DBDH lb@dbdh.dk
info@dbdh.dk www.dbdh.dk
ISSN 0904 9681
WHAT IS NAAS? • A service where Kamstrup designs, owns and operates a data collection network tailored to the utility’s special data needs • It guarantees both the uptime of the communication net- work, and that the data is re- ally collected to your defined systems KEY BENEFITS OF NAAS • The utility does not have to worry about technology phase-outs, unforeseen costs, maintenance of network com- petencies or changes in leg- islation. • NaaS ensures a strong data foundation, removes risks and frees up resources that can create greater value. • NaaS is delivered at a fixed agreed price per metering point throughout the contract period.
Simple meter data collection at Silkeborg Heat Utility and Novafos With Network as a Service (NaaS), the two utilities need much less resources on operation and maintenance of the data collection network. They can use this freed-up time to utilize the data and create more value for their custom- ers. Silkeborg Utility will retrieve frequent data from around 37,000 heat and water meters via this service, as they finish the deployment of their entire meter park. At Novafos, the solution serves approximately 75,000 water meters spread over nine municipalities in the Capital Region of Denmark, and it works flawlessly.
Priorities set based on data, went with increased optimization ”NaaS helps us work in a more data driven way. We can better filter out irrelevant things and focus on, for example, customers who have zero consumption, extremely high consumption or a very high return tempera- ture. It can also contribute to optimizing the efficiencies of our production facilities, as we can better map current issues in the pipeline network and locate customers where there is a high return temperature.” Jonas Campau, Asset Management Program Manager at Silkeborg Utility Better customer service for all parties ”Our customer department has experienced a huge upgra- de in the way they can send out bills. Having precise meter data at hand spares us from a lot of phone calls and from sending a lot of wrong bills out. We find it easier to provide customer service. We need to tweak our calculations to be just a bit more precise, and people will have the opportunity to follow their own consumption. So, there are many positive things about NaaS.” Anders Fisker, Water Distribution & Service Team Leader at Novafos
Read more on Kamstrup.com
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PREFACE
ENERGY STORAGE AND THE VALUE OF DISTRICT HEATING
And, of course, at the heart of this issue is a deep exploration of heat storage, which stands as a cornerstone for creating resil- ient and climate-friendly heating systems. As the demand for sustainable energy solutions rises, heat storage is emerging as a game-changer in balancing supply and demand, particularly as we integrate more fluctuating renewable energy sources in the power and district heating system. We hope this issue provides you with valuable insights into the future of district heating and the role it plays in achieving a more sustainable, low-carbon world.
In this edition of Hot Cool, we dive into some of the most press- ing and innovative developments in district heating. The pri- mary focus is energy storage, a critical component of ensuring reliable and sustainable system integration in an evolving en- ergy landscape. But while energy storage is the headline topic, we explore a range of other key aspects that are reshaping dis- trict heating today. From the growing relevance of low-temperature district heat- ing (LTDH) to the vast potential of waste heat recovery, this is- sue takes a comprehensive look at the innovations driving the future of energy-efficient heating solutions. Electrification of space heating is gaining momentum, but it is not so simple if it must be done intelligently simultaneously. Here, district heating often will be the intelligent solution compared to the individual solutions. In addition to these advancements, we delve into the inher- ent value of district heating, offering insights into how it con- tinues to play a pivotal role in reducing carbon emissions and supporting local energy security. Understanding source design and storage is essential for optimizing both the reliability and sustainability of district heating networks, as they must adapt to varying energy inputs and fluctuating demand.
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!
Best regards
Lars Hummelmose, Managing Director, DBDH, lh@dbdh.dk, +45 2990 0080
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HOTCOOL no.6 2024
LARGE THERMAL ENERGY STORAGE (LTES) WILL HELP SHAPE THE FUTURE ENERGY LANDSCAPE
By Geoffroy Gauthier, Energy and Calculation Engineer - Project Manager, PlanEnergi
LTES emerges as a key for the energy transition, facilitating cost-effective and reliable renewable heating and cooling for District Heating and other large-scale applications. Moreover, it enables sector coupling, harnessing excess heat and bolstering electricity grid flexibility. During periods of surplus renewable electricity, heat or cold can be generated, stored, and later deployed during peak demand, curbing additional electricity consumption. Similarly, excess heat from renewable-energy-based combined heat and power plants can be stored in LTES for later use, mitigating demand spikes while generating more profits for the plant operators. This use is key in the business model behind the Pit Thermal Energy Storage (PTES) in Høje Taastrup.
Figure 1: Aerial view of the Pit Thermal Energy Storage in Høje Taastrup (Denmark), finished in 2022 and commissioned in 2023. Photo: Ioannis Sifnaios
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Figure 2: The main stages and main stakeholders of LTES projects identified in Task 39
LTES are crucial for the energy transition Heating and cooling constitute nearly half of the world’s energy consumption, underscoring the critical role of thermal energy storage in aligning renewable energy production with the energy demand. Results from IEA-ES Task 39 have unveiled essential insights: Affordability and Efficiency: Large-scale thermal energy storage (LTES) is cost-effective compared to electrical storage solutions, with specific investment costs plummeting from 4 to less than 1€/kWh capacity. In comparison, large-scale pumped hydro storages run between 100 and 200 €/kWh capacity. Moreover, specific heat losses diminish as storage volume increases, meaning that efficiency increases.
• Online and physical leaflets, serving as an introduction to LTES and providing use cases
• Synthetic reports about how to carry an LTES project from idea to implementation, fostering informed decision- making and facilitating project implementation
• Reports about:
· LTES project development stages · The development of a materials and components database · A modeling tools comparison methodology specifically developed for LTES
• List of project references for the main types of LTES technologies
Long-term Storage Capability: LTES systems excel in storing heat and cold over extended periods with minimal losses.
• A database of materials and components
Utilization of Low-tech Solutions: LTES technologies leverage readily available and easy-to-produce materials, ensuring accessibility. Insights from IEA-ES Task 35 (another task from the Energy Storage branch of the International Energy Agency) emphasize the indispensable role of LTES within District Heating systems for optimizing energy system costs and enhancing energy efficiency. One study’s results show that doubling the thermal storage capacity for a reference scenario in Germany would lower primary energy use while reducing total energy production costs. Advancements in Thermal Energy Storage Technologies The task’s deliverables are directed to diverse stakeholders, including policymakers, researchers & engineers, and project developers. Deliverables include:
• A policy workshop (recording and presentations are available online)
All of these deliverables are available on the website of IEA-ES Task 39: https://iea-es.org/task-39/deliverables/.
IEA-ES Task 39, which ended with a policy workshop in December 2023, focused on four primary technologies capable of annually storing over 1 GWh of thermal energy: Tank, Pit, Borehole, and Aquifer Thermal Energy Storages. The task aimed to provide reference materials to accelerate LTES implementation in District Heating (DH) and industrial settings, drawing on expertise in energy system simulations, storage materials, and construction. The systems studied in Task 39 have been defined as large sensible thermal energy storages designed to store a minimum of 1 GWh/year at atmospheric pressure. The stored
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VEKS (transmission company for the Western suburbs of Copenhagen), is facilitating the optimization of electricity production in the Copenhagen area and is used in the local distribution DH network for peak shaving, yielding significant environmental and economic benefits. The PTES in Høje Taastrup received the Global District Energy Climate Awards in the Sector Coupling category during the Euroheat & Power Summit on 14-15 November 2023 in Brussels, Belgium. Figure 4: The concept of seasonal storage can be illus- trated with the mismatch between solar thermal energy production, which peaks during the summer, when the heat demand is lowest: an LTES can then be used to store large amounts of heat during the mismatch period to be reused later during the year (hence the term “seasonal” storage).
Figure 3: The main types of LTES technologies can store heat or cold in water or the subsurface
heat should be suitable for discharge into District Heating networks, maintaining temperatures between 50°C and 100°C. These technologies offer versatility, serving as daily, seasonal, or multifunctional thermal energy storage adapted to various heat sources and load profiles..
Pit Thermal Energy Storage (PTES): Denmark’s Innovative Solution
Denmark has emerged as a pioneer in Pit Thermal Energy Storage (PTES), particularly in combination with Solar District Heating (SDH) for seasonal storage. PTES, now utilized for short-term thermal storage in district heating networks, holds immense promise for decarbonizing the heating sector. The PTES project in Høje Taastrup, Denmark, illustrates this new use of the PTES technology, showcasing substantial fuel savings and CO2 emissions reductions. This 70,000 m3 PTES, owned by Høje Taastrup District Heating and
The list of PTES implemented by Danish Companies and consultancies can be seen in Table 1:
Looking Ahead: Accelerating the uptake of LTES. According to a recent study by Aalborg University, the extension of DH to reduce fossil fuel imports and consumption has tremendous potential, for instance, to use the large amounts of available waste and geothermal heat. “District Heating is the
Country
Project
Size
Heat capacity
Year commissioned
DK
DTU
500 m³
1983
DK
Ottrupgaard
1'500 m³
43.5 MWh
1995
DK
Marstal Sunstore 2
10'000 m³
638 MWh
2003
DK
Marstal Sunstore 4
75'000 m³
6'960 MWh
2012
DK
Dronninglund
60'000 m³
5'500 MWh
2013
DK
Gram
122'000 m³
11'300 MWh
2014
DK
Vojens
203'000 m³
18'800 MWh
2015
DK
Toftlund
85'000 m³
6'500 MWh
2017
CN
Tibet
15'000 m³
1'000 MWh
2018
DK
Høje-Taastrup
70'000 m³
3'300 MWh
2023
Table 1: Historical table of PTES development in Denmark or initiated by Danish companies and consultancies. The last line is the only storage that is not used as seasonal storage for solar thermal heat.
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Figure 5: Function of the PTES in Høje Taastrup. Source Høje Taastrup Fjernvarme and VEKS
These will be tackled by Task 45, the follow-up of IEA-ES Task 39. This new project will run from 2024 to 2027 and aims to leverage insights from the previous task. In parallel, the EU- funded project “TREASURE” will focus on demonstrating PTES in five European countries, building upon reference initiatives like the PTES in Høje Taastrup.
next enabling technology for integrating Renewable Energy.” This potential can only be supported by using LTES, which in turn needs to be widely implemented.
Within Task 39, the policy workshop has highlighted the main challenges and opportunities for the vast deployment of LTES:
raising awareness about LTES technologies, demonstrating their robustness, and illustrating typical implementation process from idea to commissioning
For further information please contact: Geoffroy Gauthier, gg@planenergi.dk
reducing uncertainties by facilitating the permitting process and increasing standardization
1 GWh (1,000 MWh) is enough heat to supply the demand of 62 households for one year. Households in Denmark consume, on average, 16 MWh/year for space heating and hot water in 2020. (Source: Danish Energy Agency)
shortening the realization time of LTES by sharing experiences and involving all stakeholders
decreasing costs through materials and process development and industrial network expansion
The PTES in Høje Taastrup serves three CHP plants and three waste-to-energy plants (partners in the project). Optimizing electricity production (sector coupling) and reducing peak production in the Copenhagen area is expected to represent 27.4 TJ of fuel saved/year and a total CO2 reduction of 6,200 tons/year. The total investment is 10.7 Mio €. The simple payback period is 12 years.
What are IEA-ES Task 35 and Task 39? A Task is an activity in the Energy Storage Technology Collaboration Programme (“TCP”) of the International Energy Agency (“IEA-ES”). It is working on a specific topic: Large Thermal Energy Storages (LTES) for Task 39. Task 39 gathers 60 experts from 36 institutions and 11 countries: Austria, Canada, Denmark, France, Germany, Italy, the Netherlands, Sweden, Turkey, the UK, and the USA. They can be found here: https://iea-es.org/task-39/ institutes-companies-and-experts/. The experts work in the fields of Research and Development and Industry
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HELLO, HOW CAN WE SUPPORT YOUR CITY? DBDH is the Go-To-Partner for district energy. We cooperate with all DH stakeholders and support cities in their quest for a sustainable city transformation. Use our strengths to help your city. We are the link to: Achieving climate goals through fossil-free district energy Strategic energy planning Knowledge on district heating and cooling A wide network of experts Visiting green solutions in Denmark
We do not know everything about district heating, but we know who does :-) Contact one of us. Our advice is free of charge.
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WASTE HEAT — THE OVERLOOKED RESOURCE WAITING TO BE HARNESSED
By Oddgeir Gudmundsson, Director, Climate Solutions, Danfoss A/S, Nordborg
Jan Eric Thorsen, Director, Climate Solutions, Danfoss A/S, Nordborg
In an era of energy innovation, it’s almost paradoxical that vast amounts of heat generated by urban infrastructure and industrial processes continue to go to waste. Supermarkets, data centers, large office buildings, subway stations, and even wastewater treatment plants constantly release valuable thermal energy into the atmosphere. Yet, despite the growing focus on sustainability, this untapped heat escapes largely unnoticed, dissipating into the air.
But let’s think about them!
Given the variety and sheer scale of waste heat sources surrounding us, a simple question arises: Why aren’t we capturing and repurposing this abundant energy resource? The potential is enormous, and the energy efficiency and sustainability benefits are equally compelling. The challenge now lies in recognizing waste heat as the asset it truly is and turning it into a cornerstone of our energy systems. Why do we not capture the abundantly available waste heat and use it for something useful? The answer to that question can vary depending on whom is being asked, but in many cases, the answer will be in the following directions: A. It is not economical compared to using normal high-quality energy carriers, such as natural gas, coal, electricity, etc. B. Waste heat recovery is not our business. C. Once we have modernized our processes there will be so little waste heat that it is not worth capturing it. D. There are no options to deliver it to anyone who can use it. E. It is too complicated to capture it! F. No need; decarbonized electricity is just around the corner... Of course, there can be some merit in some of the answers, particularly if basing it on the past and turning a blind eye to the future.
A) It is not economical compared to using normal high-quality energy carriers, such as natural gas, coal, electricity, etc. Clearly, this would represent a closed and ignorant mindset, as those readily available fossil fuels are not a long-term viable option. It would even be simple to argue that if their real cost to society were included, they would not have been a viable option for a long, long time. Once decarbonization really takes off, it will become clear that utilizing waste heat sources will become essential for enabling an ecologically and economically sustainable transition of the energy system. B) Waste heat recovery is not our business. The traditional approach is, as the statement indicates, not to bother about the waste heat and treat it as an unavoidable waste product. Historically, there have been no monetary benefits from capturing and reusing the waste heat due to the low cost of primary fuels during the era of fossil fuels, and thus, there was no basis for taking up the business. With the changing energy landscape and phase-out of fossil fuels, the focus on waste heat utilization is obvious. Nonetheless, the primary challenge is intact: waste heat utilization is not
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scale heat recovery can be found in many Danish supermarkets. The supermarket heat recovery cases clearly show that it makes good sense to capture even a small amount of waste heat and make it available for others to use 2 . D) There are no options to deliver it to anyone who can use it. Yes, this is true in many cases, and it is complex and even time- dependent! We would, however, argue that this is still a poor excuse, as one should expect that initiatives like mandatory heat planning and a requirement to assess the feasibility of district energy systems in urban areas in the European Union will be the norm around the globe in the future. With proper heat planning, current and future local heat sources and heat demands are mapped to create a long-term holistic approach to fulfilling local thermal demands. As heat planning becomes more widely adopted, new opportunities will arise. Opportunities can emerge either through establishing city- wide district energy systems or through area zoning and local microgrids, where smart city planners designate areas for industrial processes with low-temperature waste heat next to areas with industries with low-temperature heat demands. While waste heat has a great potential for fulfilling building space heating and hot water demands other use cases could be onshore fish farming, greenhouses, spa facilities, etc. E) It is too complicated to capture it! Fortunately, the notion that heat recovery is complicated is, in most instances, wrong! While it can be difficult to retrofit new means to capture the waste heat in existing constructions, whether in a tightly optimized industry production hall, an old subway station, or elsewhere, it might not be necessary. In most industry processes, existing cooling systems ensure that the industry process is running smoothly and that products are produced with consistent quality. In essence, this means that the waste heat is already being captured; it is just not used for anything. In other instances, the waste heat is dissipated directly into the air, particularly if it has really high temperatures. Such examples can be found in metal smelting operations. Capturing such waste heat is a bit more complex, but even in these cases, there are commercially available methods. Similarly, in any commercial cooling system, whether in a large building, supermarket, or data center, there is no way around having a chiller system that generates the required cooling. Again, this means that the waste heat from commercial operations that require cooling will be available in a central location.
a core business of manufacturing companies. To facilitate waste heat utilization, creating new and motivating business models is necessary. Appropriate business models can, on the one hand, create the foundation for the waste heat owners to integrate waste heat recovery into their production processes and, on the other hand, provide the foundation for establishing specialized waste heat recovery companies that can bridge the gap between the waste heat owners and eventual heat users, for example, district heating utilities. Typically, the business setup involves the waste heat owner, who can be considered a heat supplier or a cooling customer, and a counterpart, who can be either a heat customer or a cooling supplier. Where district heating networks are present, the utility is the obvious counterpart. Depending on the business model, the district heating utility could either buy the heat for a substitution price, which could reflect the lowest cost of an alternative heat source, or sell cooling to the waste heat owner, which could reflect the alternative cost of dissipating the waste heat. The choice of the business model will depend on various factors, such as waste heat temperature, accessibility, availability, investing entity, etc. A common denominator for waste heat is that the cost of the waste heat will be low, as it will always be measured against the lowest-cost alternative heat generation, which can either be existing or planned heat sources. Due to the wide variety of waste heat sources and district heating system setups, the business opportunity should be investigated in each case to ensure long-term viability and minimum risks for all partners. Today, many concrete examples of reusing waste heat in district heating systems exist 1 . The learning from these examples provides a strong basis for adapting regulations and reporting obligations to ensure simple and favorable conditions for utilizing this important low-carbon resource. C) Once we have modernized our processes, there will be so little waste heat that it is not worth capturing. Everyone should embrace this statement and jump on the energy efficiency train. However, all processes have unavoidable waste heat—the last step should always be heat recovery for secondary usage! The first step should always be to energy-optimize processes. The second should be to reuse as much waste heat as possible internally. The third should be to export/sell the remaining waste heat for other purposes. After all, if companies do not ensure that they have an economic operation, someone else will eventually outperform them and potentially put them out of business. It is important to note that waste heat recovery is not only viable for large-capacity sources. Heat recovery from supermarkets is a perfect example of how even small-scale waste heat recovery is economically attractive. A great example of successful small-
1 Danfoss whitepaper: The world’s largest untapped energy source: Excess heat. Danfoss Impact, vol. 2, 2023. https://www.whyenergyefficiency.com/solutions/allsolutions/the-worlds-largest-untapped-energy-source-excess-heat 2 Supermarkets turned into heat suppliers. https://www.danfoss.com/en/service-and-support/case-stories/cf/danish-supermarkets-turned-into-heat-suppliers/
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of the supply and demand. The key features here are cost- efficient large-scale thermal storage, which come at a fractional cost compared to alternative energy storage, such as battery storage. Heat recovery applications Clearly, simply capturing the waste heat is not enough; it will also need to be made available to the waste heat user at the right temperature level. Depending on the temperature level of the captured waste heat relative to the temperature requirement of the waste heat users, different temperature adaption options are available. These can be 1) direct heat exchange via heat exchanger, 2) a combination of a heat exchanger and a heat booster unit, could be a heat pump, or 3) a heat pump.
In other instances, such as subway stations, the ventilation systems can be retrofitted with simple air-to-water heat exchangers to capture the waste heat. The bottom line is that waste heat recovery is typically not complicated from a technical point of view. The complexities are generally on the organization side, where it can be narrowed down to the lack of knowledge of the potential value of the waste heat, complicated local regulations, unfavorable tax regulations, or complex reporting and documentation requirements. F) No need; decarbonized electricity is just around the corner... Which corner and at what cost? The fact is that while electrification and decarbonized electricity are very big parts of the future solution, it truly matters how electrification takes place. It can be made sustainable and cost-effective with a minimal ecological footprint, or it can be made with a major ecological footprint and high cost. Smart electrification is to utilize all available resources to minimize the final electricity demand, and by this, the investment in the generation and distribution capacity is also minimized. In this regard, waste heat sources and other renewable, low-temperature sources are immensely important. Another important aspect is ensuring as much decoupling of the electricity demand and generation as possible. In fact, decoupling is the number one measure for enabling sustainable and cost-effective electricity generation based on intermittent and fluctuating renewables. This is where district heating and district cooling come into play, as no other technology can make as cost-effective decoupling
The following section will present the general heat recovery options with district heating in mind.
Case 1: Direct heat exchange via heat exchanger In case the temperature of the waste heat is high enough to directly fulfill the temperature requirement of the district heating system, a simple heat exchanger solution should be applied:
Figure 1: An example of simple direct waste heat recovery using heat exchangers.
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Case 2: Combination of direct heat exchange and a temperature booster If the waste heat temperature exceeds the return temperature from the district heating system, the return flow should be preheated via a heat exchanger and subsequently boosted by a temperature booster. The temperature booster could either be a heat pump or it could be any type of heat source, like a fuel boiler or direct electrical heater. The choice of the boosting application can depend on, for example, the required return temperature to the process or available waste heat capacity.
Case 3: Heat pump boosting Even if the waste heat temperature is lower than the return temperature of the district heating system, it can be hugely beneficial to the district heating system, as the waste heat source can ensure high energy efficiency of the heat pump. Further, as waste heat sources tend to have stable temperature levels over the year, it will ensure that even during winter, the heat pump will have stable and predictable operations, unlike heat pumps that rely on ambient heat sources, air, or water sources.
Heat pump booster application:
Figure 4: An example of a low-temperature waste heat recovery using a heat pump.
Conclusions Waste heat is a valuable resource that should not be wasted; it’s there and can be utilized! District heating systems are key solutions for urban areas to take advantage of available waste heat sources and, by that, make our cities more sustainable, livable, and resilient.
Figure 2: An example of a combination of a direct waste heat recovery using heat exchangers and further temperature boosting using a heat pump.
Boiler booster application:
Further, recycling waste heat reduces pollution, retains money in the local community, and creates local jobs.
And finally, it’s the basis for realizing that the future renewable and sector-coupled energy system will be smart and cost- efficient.
We have no excuse, as all necessary solutions are already commercially available!
For further information please contact: Oddgeir Gudmundsson, og@danfoss.com
Figure 3: An example of a combination of direct waste heat recovery using heat exchangers and further temperature boosting using a fuel or electric boiler.
The boiler could, for example, be an existing boiler on the waste heat source premise, where typically, a smaller share of the capacity is used for boosting the recovered waste heat temperature.
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LOW- TEMPERATURE DISTRICT HEATING FOR OLD AND NEW BUILDINGS
By Niels Hansen, Senior Consultant, Albertslund Municipality
Albertslund Utility, Denmark, has cracked the code to lower the district heating temperature all over the town. With shunt valves and temperature zones, the utility can lower the temperature in the 60-year- old grid without changing the existing pipes and upgrading the 6-bar net to a 10-bar net. With shunt valves, both the temperatures and the pressure in the grid can be lowered simultaneously. And the flexibility gained by temperature zones is highly valued by the utility.
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for 100% LTDH in Albertslund by January 2026. The social housing areas, covering more than 50% of the housing stock, were thoroughly energy refurbished with support from the National Building Fund of Denmark. In 10 years' time, half of the homes of Albertslund would be low-energy buildings with no need for high DH temperatures. Should we continue with two grids – one for high temperatures and one for LTDH? Or should we try to go for 100% LTDH? We chose LTDH, and we informed all building owners two times by mail: Be ready for lower temperatures by 2026”, explains Catarina Nørgaard Marcus-Møller, head of the district heating utility of Albertslund. A long-term strategy for lowering the temperatures How to get started? Albertslund Utility created an action plan to fulfill the DH strategy. Initially, there was a lot of focus on energy consulting and guiding the end users. Energy refurbishment concepts were created for privately owned terraced houses. However, it took a lot of effort, and the results were limited. Things simply went too slow. The next step was changing all the heat meters to intelligent meters, which provided the utility with a lot of data to analyze. Then, a new service was started, where the end users could
Low-temperature district heating (LTDH) has been in operation for several years in Denmark. Also, in Albertslund, newly built and energy-refurbished housing areas have been supplied with LTDH for the last 15 years. LTDH significantly reduces heat loss and improves the opportunities for exploiting local renewable energy sources, such as industrial surplus heat or geothermal energy. Albertslund is a town located 15 km west of Copenhagen with around 30,000 inhabitants. Most of the town was built in the 1960s and 1970s. However, in recent years, urban development has been happening in three major areas of Albertslund. The goal is 45,000 inhabitants by 2045. Despite all the new buildings being built, the main concern for the utility has been how to lower the DH temperature for the existing buildings. When new housing areas in Albertslund were built or when housing areas were energy refurbished, the DH temperature was lowered. It happened with a shunt valve, supplying LTDH to the specific area while higher temperatures were still supplied to the rest of the town. The number of LTDH areas grew.
”In 2016, the municipality of Albertslund agreed on a strategy
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This approach, we had the opportunity to test, or demonstrate, in the REWARDHeat project, funded by the EU Horizon 2020-programme.
grid. With no grid division, the DH plant's temperature should be much higher than 60 degrees to provide the last customer with 60 degrees DH. With this approach, many of the end users would never reach LTDH. Instead, Albertslund Utility will supply higher temperatures in the main pipes and then lower the temperatures with shunt valves to the end users. Even if the temperatures in the main pipes exceed 60 degrees, the temperature will be much lower than today. Albertslund Utility expects to have around 35 shunt valves in operation in a few years. The heat loss is bigger in the small pipes With the use of shunt valves, more end users will be supplied with LTDH – compared to a central lowering of the temperature. Thereby, the temperature is lowered in a greater part of the entire net. The shunt valves increase the overall efficiency and limit the overall heat loss in the grid. The heat loss in the main pipes is smaller compared to the heat loss of the smaller pipes supplying the end user with DH. In Albertslund, the heat meters are placed indoors by the end users. Therefore, all the heat loss in the grid is covered by the utility – or included in the heating price. Shunt valves improve the flexibility Probably the most important thing learned from the work with shunt valves is the flexibility obtained in the grid – flexibility concerning temperatures and flexibility regarding the pressure in the pipes. For example, if one housing area needs higher temperatures on a cold day, Albertslund Utility can increase the temperature in this area while keeping the temperature lower in other areas. The DH grid of Albertslund has been in operation for 60 years and is dimensioned as a 6-bar grid. When lowering the temperature, a given need for energy will result in a larger flow of water. It can be solved with larger pipes and/or with higher pressure. Traditionally, the DH pressure is created from the DH plant or with strategically placed booster pumps in the grid. However, according to the local circumstances, shunt valves can increase the pressure locally for each individual DH area. Therefore, Albertslund Utility can lower the temperature in the existing
rent a new DH unit from the utility. To participate in the service, house owners need sufficient radiator capacity and adjustable valves on the radiators. Catarina Nørgaard Marcus-Møller explains, “The question was how to move a step further towards LTDH in Albertslund. We came up with the idea, and with the help of shunt valves, to divide the grid into smaller islands or temperature zones. Thereby we can target our work towards smaller limited housing areas. We can lower the temperature stepwise in one single area without other areas having to wait for lower temperatures. With this approach, we had the opportunity to test, or demonstrate, the REWARDHeat project, funded by the EU Horizon 2020-programme.” An EU project showed the way In 2020, with the REWARDHeat project, Albertslund Utility installed a Grundfos iGrid-shunt at the end of a typical Danish street with one-family houses from the 1960s. The DH temperature was lowered step by step, with the return temperature from all 104 houses being monitored. Troubles were expected but never really occurred. In February 2021, the whole street was supplied with 60 degrees LTDH, even though the outside temperature was below zero. Five houses had needed consulting. In three houses, smaller adjustments were made without changing any components. In one house, a smaller component was changed. And in the fifth house, the heating unit was changed. The learnings from REWARDHeat and the street named Porsager strengthened the belief in fulfilling the strategy of lowering the temperature in all of Albertslund. Lowering the temperature by 20-30 degrees on a cold winter day in an ordinary Danish housing area was much easier than expected. Due to the REWARDHeat experience, the last two housing areas of Albertslund, heated by natural gas, were converted directly to LTDH areas in 2023. The use of shunt valves became permanent when the benefits became clear The work with shunt valves has changed in Albertslund. Initially, shunt valves were regarded as a temporary component in the grid, awaiting the lowering of the temperatures in the DH grid. Today, shunt valves have become a permanent part of the DH
16 HOTCOOL no.6 2024
The REWARDHeat project, which established a shunt valve on the street named Porsager, was carried out in close cooperation with the homeowners' organization. Meetings were held with the homeowners, and they had a direct phone number for an energy consultant during the process. Three good advice Find out what temperatures are really needed. There is a lot of focus on keeping the temperature on the coldest day; however, how often is it really that cold? If we cannot supply our end users with LTDH all year, then LTDH 350 days/year is far better than high temperatures all year.
6-bar grid without needing to upgrade to a 10-bar grid. It would have been costly for the utility and for the end users who were still directly supplied with DH without a heating unit. There are also downsides to working with shunt valves: They take up space. They need service. They cost money. The division of the greater old grid into smaller islands means a limited number of buildings will never have LTDH. However, the temperature will be lowered for all end users. The transition to LTDH is one of Albertslund Utility’s contributions to the green transition of Albertslund Municipality. By lowering the temperature, the DH supply was made more efficient with less heat loss and improved the possibility of exploiting local renewable energy resources. Overall, Albertslund's DH is prepared for efficient interaction with the electricity market. Albertslund Utility believes that if one day a geothermal plant is considered, the heat from the underground can be exploited as DH with no need to increase the temperature. This improves the business case significantly. Smaller quantities of surplus heat will also be easier to exploit. Since 2015, surplus heat from a data center in Albertslund has been exploited. Albertslund expects a greater part of the DH base load will be covered by surplus heat in the near future. Involvement of end users The DH Utility of Albertslund has, since the beginning in 1964, been operated by the municipality. Since 1980, the User Council, with representatives from all housing areas, has been asked on all new initiatives, before they were approved by the city council. Direct citizen involvement has played a major role in the development of Albertslund Utility.
Communication and open dialogue with the end users. Be reachable. Pick up the phone. Show up if invited. Be present.
With the service of renting out heating units, it is easier for the end users to obtain a well-functioning, high-quality heating unit. There is no money upfront; it’s a pure subscription. The service brings the utility closer to the end users.
4 things we have learned The buildings perform much better with LTDH than expected
Improved flexibility with shunt valves and the division of the grid into smaller islands
Minimal need for upgrading the grid when lowering the temperatures
DH end users are generally positive towards the transition into LTDH
For further information please contact: Niels Hansen, nej@albertslund.dk
”Finally, the service of renting out heating units has proven to be a major success. Most end users come to us when their heating unit needs replacement. More and more, we deliver comfort, rather than ‘just’ DH, to our customers”, Catarina Nørgaard Marcus-Møller says.
Catarina Nørgaard Marcus-Møller, head of the District Heating utility of Albertslund
17 www.dbdh.dk
VALUE OF DISTRICT HEATING HEAT SOURCE DESIGN AND STORAGE
By John Tang Jensen, District Heating Specialist
The advantages of having a district heating system for heating buildings are multiple, and this article investigates investment benefits compared to individual solutions and how heat source design, including storage, can minimise investments and costs by com- bining different fuels, technologies, and sources.
Introduction Heat source design for district heating can save investments compared to individual heat source design in four different ways: Reducing extra individual capacity need Reducing capacity demand
In this article, benefits from different heat source designs are made by an example, and it is additionally investigated what influence heat storage will have on both investments and on heat production price if the storage is used to optimise the costs for electricity by using a heat pump, an electric boiler, and income if using a natural gas combined heat and power (CHP) unit. The following standard data are used to keep the comparisons simple: Table 1 shows basic data.
Reducing cost with classic heat source design Reducing costs by combining technologies
Basic data Annual heat demand
100,000
MWh
Capacity demand per household
12.0
kW
Investment of 12 kW individual heat pump air-to-water, including installation
14,721
£/unit
Number of households
7,143 105.2
households
Total investment in individual heat pumps
Million £
Energy demand per household annual
14
MWh
Tap water Demand
20 %
Heat loss if District heating
17%
Table 1: Basic scenario parameters. Investment data from the Danish Technology catalog.
18 HOTCOOL no.6 2024
A temperature curve for Manchester, which is a typical UK urban area suitable for district heating, is used. The chosen year (2020) shows only 4 days with an average temperature below 0 °C. How low the temperature can get in cold years is important when it comes to choosing the maximum capacity of equipment. In the above example, a 12.0 kW air-to-water heat pump unit is chosen for the individual demand, which is above the maximum demand on the coldest day (11 kW) in the example. If the temperature is lowered by an average of 10 °C, the 12.0 kW capacity still covers days with average temperatures at – 10 °C. For the same reason, the capacity demand for the district heating network is chosen to be higher than the 2020 temperature curve requires. For the district heating capacity design, it is for the security of supply reasons expected that reserve capacity is included and can cover if the largest unit is falling out of production. The investment prices and technology lifetime are all based on Danish Technology Catalogues made by the Danish Energy Agency and converted to British Pounds Sterling. It is assumed that investment costs in the UK are the same as in Denmark. If investments are higher, the benefits of establishing district heating networks may be less significant. When it comes to CHP production, the investments should be shared between the heat and electricity sides, which will reduce the investment costs paid by the heat side. But if the district heating company 100 % operates the CHP plant independently, then the full investments, which is the case in these calculations, are included in the heat side costs. The
income from selling electricity is then used to reduce the costs of producing the heat.
A production model is developed for calculating heat production costs (OPEX) without and with heat storage, including a strategy for producing the heat as cheaply as possible. Daily, the technology with the lowest hourly heat production prices is chosen first. If storage is included, the model allows loading the storage at low heat prices and unloading it in hours at high heat prices. The model without storage can only produce the daily needed heat demand, but the technologies with the lowest heat production price are preferred first. Summary and conclusion Table 2 shows investments in an individual heat pump solution (105 million £) compared with six different district heating source designs, from a basic design to a waste heat source design combined with a heat pump and a storage tank. Delivering heat for households in an urban area around Manchester shows investment savings if a district heating network is established. The investment level can be kept at the same low level even if more technologies are combined and a heat storage system is added (Storage is added in the last three columns). According to the example, total investment costs can be reduced by between 32% and 45% by establishing district heating networks and using classic or combined heat source design compared to an individual heat pump solution.
WP + HP + storage
WP + HP + storage
Summary
Individual
Basic Classic HP + CHP HP + CHP + storage
Investment costs per delivered heat
£/MWh-heat
42.1
28.6 20.4 21.1
21.3
21.3
17.9
Capacity demand
MW
86
60
50
40
40
50
45
Investment production and network
Million £
105
71
64
66
66
66
58
Reduction % 32% 39% 37% 37% 37% 45%
Investment savings by district heating
1. Reducing extra individual capacity
Million £
8.1% 8.5
8.5
8.5
8.5
8.5
8.5
2. Reducing capacity demand
Million £
24.0% 25.2 25.2 25.2
25.2
25.2
25.2
3. Reducing costs by classic design
Million £
7.0%
7.3
7.3
7.3
7.3
7.3
4. Reducing costs by combining technologies
Million £
17%
17%
17%
Reducing OPEX costs by combining technologies Average heat price January-june 2023
£/MWh-heat
29.34 31.66 15.55
15.4
11.2
15.36
Saving by having storage
£/MWh-heat
0.15
Investment storage over 25 years
£/MWh-heat
0.002
Table 2: Four ways to reduce investment costs for heating buildings with district heating network systems. (HP= Heat pump, WH=High-grade Waste heat and CHP=Combined heat and Power heat sources)
19 www.dbdh.dk
is constructed at 12 kW-heat, which is (12-11)/11 = 9.1 % above needed capacity. This extra individual capacity investment is not needed the same way when a district heating solution is established because a peak and reserve load capacity deliver the security of supply. If, instead, an 11 kW capacity could be installed, the investment would totally be 8.5 million £ lower, which is 8.1 % lower than the original individual heat pump investment. See Table 2. Reducing capacity demand District heating systems are not affected by peak load hot tap water demand the same way as individual heat pumps because households in a heating network do not use hot tap water at the same time. The stored energy in the district heating network water can deliver the needed energy in peak load hours either by reducing the forward temperature momentarily or by increasing the forward temperature a couple of hours before the peak load hour occurs. Figure 1 shows a capacity duration curve for Manchester. The heat production capacity demand for one household is compared with the same need for capacity in a district heating system, including hot tap water and heat loss. In our example, the production capacity in the district heating system only needs to be 4.0 kW-heat compared to 11.0 kW- heat for the individual household. The reason is that the district heating system only needs to deliver average capacity demand on a daily basis compared to an individual heat pump delivering on an hourly basis. Theoretically, this saves 61.6 million £ investments in individual heat pumps or 59% of investments if the individual heat pump would have been 4 kW instead of 11 kW. This saving, though, is theoretically because of the heat piping network, and each household needs a district heating unit, which requires investments. The district heating capacity for producing heat, including heat loss, is significantly cheaper than individual technology.
The saved investment costs compared to individual solutions on the identified ways to reduce investments are calculated to be 8.1% regarding saving the extra individual capacity, 24.0% by reduced capacity demand, including heat network investments, and 7.0% by making a classic heat source design. The investment in heat source capacity by combining more technologies is almost on the same level as the classic design, as shown in the last four examples (columns). In the last three heat source designs, a heat storage capacity of 200 MWh (3,450 m3) is combined. See also tables 3 and 4 for more details. The OPEX cost comparison clearly shows that combined technologies, including heat storage, can reduce heat price costs significantly from a price of around 30 £/MWh to a price below 16 £/MWh. The reason for this is the possibility to choose operation on different technologies in hours where electricity prices result in very low heat prices. This result is important because society additionally gains value from this by reduced electricity prices, reduced electricity curtailment from wind turbines and solar PV, saved investment in power grids, saved investments in renewable power production capacity, and reduced balancing costs and investment costs for the security of supply in power system. Reducing extra individual capacity When an individual heating solution is established, the heat source capacity must be able to cover demand on the coldest day and hour during the year and heat the hot water immediately, which often requires 25 kW-heat capacity or within an hour less to heat a water tank. In our example, the capacity for individual supply must be at least 11 kW. To ensure capacity demand is covered, the installed equipment is chosen to be the size just above the maximum capacity demand, which in our example means the heat pump capacity
Figure 1: Heat production capacity demand district heating and individual heating per dwelling
20 HOTCOOL no.6 2024
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