District Heating Technologies Research Articles

Comparison of Suitable Business Models for the 5th Generation District Heating System Implementation through Game Theory Approach

Abstract District Heating and Cooling (DHC) technology is widely recognised as a promising solution for reducing primary energy consumption and emissions. The 5th Generation District Heating and Cooling (5GDHC) network is the latest DHC concept characterised by low-temperature supply, bi-directional heating network operation, decentralised energy flows, and surplus heat sharing. Unlike the 4th Generation District Heating (4GDH) technology, the 5GDHC technology switched to a consumer/prosumer-oriented perspective. The introduction of 5GDHC solutions requires high investments, an important barrier to further developing DHC systems. Therefore, a novel pricing and business model could include introducing co-owners or energy managers into the system. Three different local market business models for 5GDHC at the community level have been tested. The reverse technical and economic simulation has been used for a feasibility study to determine the resources, business models, and combinations closest to the break-even point with lower costs and higher gains for all involved stakeholders.

Decentralized Temperature and Storage Volume Control in Multiproducer District Heating

Modern district heating technologies have a great potential to make the energy sector more flexible and sustainable due to their capabilities to use energy sources of varied nature and to efficiently store energy for subsequent use. Central control tasks within these systems for the efficient and safe distribution of heat refer to the stabilization of overall system temperatures and the regulation of storage units state of charge. These are challenging goals when the networked and nonlinear nature of district heating system models is taken into consideration. In this letter, for district heating systems with multiple, distributed heat producers, we propose a decentralized control scheme to provably meet said tasks stably.

A Different Approach to Develop a District Heating Grid Based on the Optimization of Building Clusters

Currently, reducing energy consumption and fossil fuel emissions are key factors placed in the first position on the European agenda. District heating technology is an attractive solution, able to satisfy the energy and environmental goals of policymakers and designers. In line with this, a different approach to planning a district heating grid based on the optimization of building clusters is presented. The case study is Wilhelmsburg, a district of Hamburg city. This approach also investigates the usage of industrial waste heat as the grid’s heat source, which is CO2-neutral. First, the data acquisition regarding the buildings’ location and heat demand are described in detail. Based on the derived data and the source of the industrial waste heat, the district heating grid is created by clustering the buildings and connecting the obtained nodes. Furthermore, the grid’s efficiency is improved by eliminating nodes, which are too distant from the heat source, or have lower heat demand. Finally, a single building is simulated in Matlab/Simulink, showing the energy-savings and ecological results. The usage of the district heating grid saves 97.32 GWh annually, which results in financial savings of €5.83 million, and avoided CO2 emissions of 19,585 tCO2.

Involving 4th generation district heating technologies: residential buildings in remote areas of Russia

This study aims to justify the possibility of expanding the energy and economic efficiency of a district heating [DH] system. The case study territory is a remote area of the Omsk region (Russia); the method is electric heating. To address this issue, we (1) considered the potential of modernizing these DH systems, (2) analyzed available options, (3) designed the main and auxiliary heat generation equipment, and (4) committed a feasibility study. The design heat consumption was 0.24 MW. To achieve this goal, we suggested two heat pumps; their capacity was 280 kW, and the investment required to install two heat pumps of 150 kW was 2.6 billion rubles. The total capital cost was 4.0 billion rubles. The annual effect after the heat pumps were installed was 0.7 billion rubles. The payback period was 5.6 years; to decrease it, one should install multiple heat pumps on the consumer side. The reason is to avoid heat distribution losses. Replacing traditional DH plants with electric boilers is feasible only if the cost of heat is 6,600 rubles per MWh or above. This cost has already been achieved for several DH plants. Ground source heat pumps are viable at lower prices, approximately 4,100 rubles per MWh. This option is especially helpful in remote areas of the Omsk region where the billing tariff is already high. When modernizing the heat supply infrastructure of the northern areas of the Omsk region, one can increase annual electricity consumption by 6%, decrease tariffs, and become more ecologically friendly at the same time.

Heat recovery and thermal energy storage potential using buried infrastructure in the UK

Dispersed space heating alone accounts for 40% of UK energy use and 20% of carbon dioxide (CO2) emissions. Tackling heating and building cooling demands is therefore critical to achieve net-zero ambitions in the UK. The most energy-efficient way to reduce the carbon dioxide emissions of heating and cooling is through the use of ground-source heat pumps and district heating technology. However, capital costs are often high, sometimes prohibitively so. To reduce investment costs, it is proposed to use buried infrastructure as sources and stores of thermal energy. Barriers to this innovative approach include lack of knowledge about the actual net amount of recoverable energy and impacts on the primary function of any buried infrastructure, as well as the need for new investment and governance strategies integrated across the energy and infrastructure sectors. Additional opportunities from thermal utilisation in buried infrastructure include the potential mitigation of damaging biological and/or chemical processes that may occur. This paper presents a first assessment of the scale of the opportunity for thermal energy recovery and storage linked to new and existing buried infrastructure, along with strategic measures to help reduce barriers and start the UK on the journey to achievement of its infrastructure energy potential.

Fourth-Generation District Heating and Motivation Tariffs

Abstract Future district heating systems and technologies—also known as fourth-generation district heating—have a potentially important role to play in the green transition of societies. The implementation of fourth-generation district heating involves adjustments in the demand side to allow for low temperature supply. In order to facilitate such changes, district heating supply companies have in recent years introduced tariffs with penalties for high return temperatures and benefits for low return temperatures. This paper describes the case of a housing community of 17 buildings in their attempts to adjust to such tariffs as an integrated part of connecting to district heating. Replacing domestic hot water tanks with instantaneous heat exchangers and introducing smart meters resulted in abilities to lower the return temperature from around 40 °C to around 30 °C. However, the current design of the motivation tariffs does not yet fully compensate the consumers because the supply company provides unnecessarily high supply temperatures. Based on such efforts, this paper discusses the fairness and effectiveness of the tariffs and provides recommendations for improving them.

Challenges for the Transition to Low-Temperature Heat in the UK: A Review

To reach net-zero emissions by 2050, buildings in the UK need to replace natural gas boilers with heat pumps and district heating. These technologies are efficient at reduced flow/return temperatures, typically 55/25 °C, while traditional heating systems are designed for 82/71 °C, and an oversized heating system can help this temperature transition. This paper reviews how heating systems have been sized over time in the UK and the degree of oversizing in existing buildings. It also reviews if lessons from other countries can be applied to the UK’s building stock. The results show that methods to size a heating system have not changed over time, but the modern level of comfort, the retrofit history of buildings and the use of margin lead to the heating system being generally oversized. It is not possible to identify a specific trend by age, use or archetype. Buildings in Scandinavia have a nascent readiness for low-temperature heat as they can use it for most of the year without retrofit. Limitations come primarily from the faults and malfunctions of such systems. In the UK, it is estimated that 10% of domestic buildings would be ready for a supply temperature of 55 °C during extreme external conditions and more buildings at part-load operation. Lessons from Scandinavia should be considered with caution. The building stock in the UK generally underperforms compared to other EU buildings, with heating systems in the UK operating at higher temperatures and with night set-back; the importance of providing a low-return temperature does not exist in the UK despite being beneficial for condensing boiler operation. Sweden and Denmark started to develop district heating technologies with limitations to supply temperatures some 40 years ago whereas the UK is only just starting to consider similar measures in 2021. Recommendations for policy makers in this context have been drawn from this review in the conclusions.

Thermal energy transfer around buried pipe infrastructure

Decarbonisation of heating is essential to meet national and international greenhouse gas emissions targets. This will require adoption of a range of solutions including ground source heat pump and district heating technologies. A novel route to these solutions includes dual use of buried infrastructure for heat transfer and storage in addition to its primary function. Water supply and wastewater collection pipes may be well suited for thermal energy applications being present in all urban areas in networks already in proximity to heat users. However, greater understanding of their potential interactions with surrounding heat sources and sinks is required before full assessment of the energy potential of such buried pipe networks can be obtained. This paper presents an investigation into the thermal interactions associated with shallow, buried water filled pipes. Using the results of large scale experiments and numerical simulation it is shown that soil surface ambient conditions and adjacent pipes can both act as sources or sinks of heat. While conduction is the main mechanism of heat transfer in the soil directly surrounding any pipe, any adjacent water filled pipes may lead to convection becoming important locally. In the test case, the thermal sphere of influence of the water filled pipe was also shown to be large, at in excess of 4 m over a timescale of 4 months. Taken together, these points suggest that design and analysis approaches when using water supply and wastewater collection networks for heat exchange and storage need careful consideration of environmental interactions, heat losses and gains to adjacent pipes or other infrastructure, and in ground conditions for a number of pipe diameters from any buried pipe.

Sustainability insights on emerging solar district heating technologies to boost the nearly zero energy building concept

Arising the Nearly Zero Energy Buildings (NZEB) concept in Europe, the solar district heating systems (SDHS) present a potential solution to meet the buildings sector's European energy performance directive. Nevertheless, current practices face several technological and economical barriers to ensure service quality. In this context, our work presents a sustainability analysis (technical, economic, environmental, and social) for SDHS integration in the residential sector to meet the NZEB and positive energy building goals. This paper proposes an application of a machine learning model incorporating multi-objective optimization and multi-criteria decision making to facilitate a sustainability index for the decision-making stakeholders and policymakers. The proposed analysis application is illustrated through retrofitted residential communities with building energy rating (D) at different sizes (10, 25, 50, 100, and 500 houses) located in Emmen (Netherlands) and compared to a standard decentralized heat pump. The optimization results show the ability of SDHS to provide a solar fraction up to 95% in the community of 500 houses. Furthermore, achieving a NZEB status is only approved economically from a community size of 100 houses with a life cycle cost of 41 €/m2 and a payback period of 25 years. These results align with a substantial environmental and social improvement of 78.2% and 29.7%, respectively, compared to the decentralized heat pump. Overall, this study provides policy decision making with an evaluation for positive energy communities and suggests the SDHS integration to meet the global sustainability goals.

Analysis of District Heating and Cooling Energy Systems in Spain: Resources, Technology and Management

District heating and cooling (DHC) systems play an important role under the new European Union (EU) energy transition strategy. Thermal energy networks are helping to stimulate the development of alternative technologies based on a broad range of renewable energy sources. The present study analysed the current situation of DHC systems in Spain and provides an overview of the challenges and future opportunities that their use will entail. Its objective is to assess thermal energy conversion and management from a holistic perspective, including a study of existing energy infrastructures. The focus of this study lies on Spain given the country’s abundance of natural resources such as renewable energy sources including solar energy, biomass and geothermal energy, among others, as well as its strategic location on the map of the EU. Based on the analysis of the three factors for energy conversion in a district heating system, namely resources, technology, and management, the methodology provided an assessment of the different factors involved in running a DHC system. The results show an estimated total production for DHC networks of 1448 MWth, of which 72% is supplied purely by renewable energy sources.

Peak shaving in district heating exploiting reinforcement learning and agent-based modelling

District Heating (DH) technology is considered to be a sustainable and quasi-renewable way of producing and distributing hot water along the city to heat buildings. However, the main obstacle to wider adoption of DH technology is represented by the thermal request peak in the morning hours of winter days, especially in Mediterranean countries. In this paper, this peak-shaving problem is tackled by combining three different approaches. A thermodynamic model is used to monitor the buildings’ thermal response to energy profile modifications. An agent-based model is adopted in order to represent the end-users and their adaptability to variations of temperatures in buildings. Finally, a Reinforcement Learning algorithm is used to optimally mediate between two needs: on the one hand, a set of anticipations and delays is applied to the energy profiles in order to reduce the thermal request peak. On the other hand, the algorithm learns by trial and error the individual agents’ sensitivity to thermal comfort, avoiding drastic modifications for the most sensitive users. The experiments carried out in the DH network in Torino (north-west of Italy) demonstrate that the proposed approach, compared with a literature solution chosen as a baseline, allows to achieve better results in terms of overall performances and speed of convergence.

Exploring the pathways towards a sustainable heating system – A case study of Utrecht in the Netherlands

Heating accounts for about half of the final energy demand in the member states of the European Union. The challenges of a transition to a sustainable heat supply vary greatly at the local level indicating the need for incorporating local data for determining solutions. Current studies vary in the inclusion of heat savings, the level of details, and energy efficiency improvements of heat supply. The interactions between the heating system and the rest of the energy system are often ignored. In this study, coherent methodological steps are proposed to identify, develop, and assess the pathways of sustainable heating systems at the local level. It combines data on the application of generic sustainable heating strategies with the collection and usage of local data and allows the analysis of the impacts of a heat transition on the local energy system. A case study is carried out in the city of Utrecht, the Netherlands. The computer tool EnergyPLAN is applied to simulate the current and future energy system in 2050, including three fossil fuels-free heating scenarios, that depict different share of collective and individual heating. The individual heating scenario leads to 17% of annual energy-saving in comparison to the future reference scenario while the mixed-options and collective heating scenarios achieve 7% and 3% respectively. The individual scenario is, however, the most expensive option as its annualized costs are 170% and 80% higher than the costs of the collective and mixed-options scenario. To achieve a fossil fuels-free heating system, annual costs per building was calculated to be 375, 665, and 1030 euro in the collective, mixed-options, and individual scenario respectively. It is concluded that the most techno-economic pathway is a mixture of energy savings, individual and district heating technologies. The optimal balance should be determined at a neighbourhood level.

District heating energy efficiency of Danish building typologies

This paper provides a state-of-the-art and freely available online overview of the district heating (DH) efficiency of Danish building typologies. The overview is based on DH consumption data from 42 969 buildings constructed up until 2017 that in combination with data from the Danish Building and Dwelling Register constitutes a dataset with a previously unseen level of detail, confidence, sample size, and research opportunities. The paper also presents an initial analysis of the dataset in terms of three heating efficiency indicators, namely 1) Annual heating energy use intensity, 2) Daily heat load variation, and 3) Cooling efficiency. The overall finding was that building typologies perform significantly different from one another concerning indicators 1 and 2, but not for indicator 3. It is therefore not possible to declare one building typology more efficient than the other as this depends on the building construction year and the considered efficiency indicator. The data indicate that further energy-efficiency improvements of the existing building stock are essential to the realization of 4th Generation District Heating technologies in Denmark and that these improvements most likely will lead to increased heat load variations that need to be addressed, for instance by enabling a larger degree of demand-side flexibility in the existing district heating systems. The large temporal variation of the buildings’ cooling efficiency indicates that there is a potential for rethinking e.g. domestic hot water production in the summer or introduce differentiated billing based on the daily, weekly, or maybe seasonal cooling performance. The presented dataset can be subject to several future investigations which are also discussed in the paper.

Performance analysis and optimization for a novel air-source gas-fired absorption heat pump

In district heating technologies, gas fired boilers and conventional heat pumps have poor performance at low ambient temperature. To tackle this issue, this study has proposed a novel air-source gas-fired absorption heat pump for district heating with flue gas recovery. Compared with conventional absorption heat pumps, the proposed solution in this study can absorb heat from both air and flue gas. Additionally, the working fluid works properly when air temperature is below 0 °C, safe and nonflammable. To analyze the economic and the thermodynamic performance of this air-source gas-fired absorption heat pump, a mathematical model, considering energy, exergy, economy and environment, has been developed. According to the simulation results of the model, the proposed air-source gas-fired absorption heat pump system here had good stability and feasibility under various operational conditions. However, as the payback period and the exergy destruction were found to be conflicting with each other, a multi-objective optimization method was established to minimize the system’s payback period and exergy destruction simultaneously. Additionally, the technique for order preference by similarity to an ideal solution decision-making method has been applied to look for the optimal solutions in the Pareto frontier, with optimal solutions of the system under different operational conditions recommended.

District heating and ambivalent energy transition paths in urban and rural contexts

ABSTRACT Most institutions and industrial actors believe that district heating infrastructure can play a key role in accelerating the transition to low-carbon energy systems. In this article we test this belief in Italy, starting from a census of all existing plants, subdivided by sources of supply and business organization models. We isolate two types of district heating (urban and rural) and find that they are different with respect to their approaches to energy transition. In rural areas, networks constitute systems that can empower the local techno-institutional complex to achieve a technological leap. Set in a pre-existing social network, district heating reinforces a sense of community and facilitates the involvement of various local players in a collective project. In the case of biomass, we are faced with local systems that have almost completed the transition with regard to the production of thermal and sometimes electric energy. In urban areas, on the other hand, networks represent functional devices for the stabilization of the techno-institutional complex. They allow cities to work on the circularity of some economies, generating added value from the same factors of production. The discrepancy between urban and rural contexts thus highlights the need to consider the ambivalence of district heating technology.

Nodal-pressure-based heating flow model for analyzing heating networks in integrated energy systems

District heating technology has prompted the development of integrated energy systems, where energy flow models have been widely used. However, as heating networks become complicated, the traditional mass flow model fails to provide efficient solutions. This study proposes a novel heating flow model based on nodal pressure in heating networks. First, transmission models based on nodal pressure are formulated. Subsequently, nodal conservation models of mass and heating flow are developed. Further, the transmission and nodal conservation models are combined, and thereby nodal pressure and user load are directly correlated. As the number of variables depends only on the nodes, the resulting model is more efficient at adapting to new network connections when the nodes do not change. Moreover, as loop pressure conservation equations are omitted in this model, fewer iterations are required. Owing to the small relative fluctuations of nodal pressure, initial iteration values can be set more effectively in the solution of the proposed model. A case study was conducted, and it was demonstrated that compared with the traditional mass flow model, the proposed model is more effective in adapting to varying network topologies, and the computational burden is significantly reduced. Moreover, the proposed model can be efficiently applied for analyzing energy transmission loss as well as system planning in integrated power–gas–heat energy systems.

Long-term urban heating load predictions based on optimized retrofit orders: A cross-scenario analysis

District heating technologies are essential key elements of future sustainable energy systems. In order to support the design process, further information concerning long-term developments related to urban heat demand are crucial. Since building refurbishments are indispensable for achieving European CO2 reduction objectives, strategies for district retrofit orders are mandatory, which, in consequence, highly affect future energy demand of urban areas. In this paper, a data-driven approach for predicting long-term urban heating loads with Nonlinear Autoregressive Exogenous Recurrent Neural Networks (NARX RNN) based on an economically optimized retrofit order and two conventional retrofit orders is proposed. For demonstration, measured heat power data of a non-residential district in Germany is used for model training and statistical feature scenario generation enables mapping of future heat demand developments.

Economic analysis and optimization of combined solar district heating technologies and systems

To find an optimal economic solution for solar district heating (SDH) in China, an evaluation model based on the levelized cost of heat (LCoH) is developed. A Python program is developed to calculate the LCoH of SDH systems using the quasi-dynamic test method. Based on these calculations, the trend of LCoH with solar collector area under different heating load intensities, heating terminal units, heated areas and land rents is discussed. The optimal solar collector area and the solar fraction are determined for combinations of solar thermal with four types of auxiliary heat sources, including air source heat pumps, ground source heat pumps, gas boilers and gas boilers with seasonal heat storage. The calculations show an economic optimal solar fraction of 11%–33% for a SDH system with heat pumps. High dependency of LCoH on network temperature is found for a SDH system with gas boilers. Seasonal heat storage minimizes LCoH of a SDH system with gas boilers at 100% solar fraction. The findings can be used as a reference for local authorities, consultants and engineers in the early energy planning to determine the optimal proportion of solar energy in a district heating system with the lowest operating cost.

Achieving Lower District Heating Network Temperatures Using Feed-Forward MPC.

The focus of this work is to present the feasibility of lowering the supply and return temperatures of district heating networks in order to achieve energy savings through the implementation of feed-forward model predictive control. The current level of district heating technology dictates a need for higher supply temperatures, which is not the case when considering the future outlook. In part, this can be attributed to the fact that current networks are being controlled by operator experience and outdoor temperatures. The prospects of reducing network temperatures can be evaluated by developing a dynamic model of the process which can then be used for control purposes. Two scenarios are presented in this work, to not only evaluate a controller’s performance in supplying lower network temperatures, but to also assess the boundaries of the return temperature. In Scenario 1, the historical load is used as a feed-forward signal to the controller, and in Scenario 2, a load prediction model is used as the feed-forward signal. The findings for both scenarios suggest that the new control approach can lead to a load reduction of 12.5% and 13.7% respectively for the heat being supplied to the network. With the inclusion of predictions with increased accuracy on end-user demand and feed-back, the return temperature values can be better sustained, and can lead to a decrease in supply temperatures and an increase in energy savings on the production side.

Economical, environmental and exergetic multi-objective optimization of district heating systems on hourly level for a whole year

District heating systems are proven to be an effective way of increasing energy efficiency, reducing the environmental impact and achieving higher exergy efficiency than individual heating solutions. The leaders in district heating integration are Scandinavian countries with more than 50% of the covered total heating demand. Nevertheless, these systems haven’t reached their full potential in most European countries. The reason for this could be that energy planners often study only the economic feasibility of the system, thus neglecting other crucial aspects of the previously mentioned district heating. In research papers, district heating multi-objective optimization usually takes into account the minimization of the total discounted cost and the environmental impact. Most times, these two objectives are studied as a single objective optimization problem through the internalization of the cost related to carbon dioxide emissions. This paper presents the multi-objective optimization method which is capable of optimizing district heating technology supply capacities and their operation, including thermal storage, for a one-year time horizon in order to satisfy the optimization goals. The model was written in the open-source and free programming language called Julia, while linear programming solver named Clp was used to obtain the solution. The solver is part of Julia’s optimization package called JuMP. Three separate objective functions are included in the model: the minimization of the total discounted cost, the minimization of carbon dioxide emissions and the minimization of exergy destruction. Since these three goals are often in conflict, the final result of multi-objective optimization is the so-called Pareto surface which presents the compromise between all possible results. To deal with the multi-objective optimization problem, the weighted sum method in combination with the epsilon-constraint method was used. The most suitable result has been chosen using the knee point method which is a solution the closest to the Utopia solution where all three goals reach their optimal value.