Heating Grid Research Articles

Resilience enhancement strategy of multi-energy coupling distribution network considering movable energy storage equipment

With the deepening of energy transformation, multi-energy coupling has become an effective method to alleviate the energy gap and improve the energy utilization rate. As a bridge connecting users and the power system, the distribution network is becoming multi-energy coupling as well. Therefore, to ensure a stable supply of power, heat, and other energy sources, it is of great significance to study the resilience improvement of multi-energy coupling distribution networks. This paper proposes a strategy for improving the resilience of multi-energy coupling distribution networks considering movable energy storage equipment (MESS) configuration. Firstly, the multi-energy coupling distribution network model is established, and the mathematical model of each piece of equipment is established considering the coupling of the power grid and heat grid. Secondly, based on the loss of load probability (LOLP), considering the importance of the load, it is expanded to the loss of important load probability as an index to evaluate the resilience of distribution networks. Thirdly, a distribution network resilience improvement model based on the configuration and operation of the MESS is established, and the optimal configuration capacity and operation strategy of the MESS is solved by taking the minimum operation cost as the objective function, i.e., the configuration cost of the MESS, the load shedding cost and the cost of wind and PV abandonment. Finally, based on the IEEE-33 node distribution network, a multi-energy coupling distribution network model is built, which verifies that the method proposed in this paper can effectively reduce the total cost and improve the resilience of the multi-energy coupling distribution network.

A prosumer-based sector-coupled district heating and cooling laboratory architecture

New control strategies for thermal systems and innovative district heating and cooling grids can help to decarbonize the thermal sector. Before implementing these new concepts, they should be validated, ideally with commercial hardware but without influencing user comfort. For this reason, the laboratory at the research center for Combined Smart Energy Systems (CoSES) at the Technical University of Munich (TUM) was designed. By combining commercial hardware with Power Hardware in the Loop simulations, the laboratory enables research in a controllable, but realistic setting without affecting real users. It consists of five prosumers equipped with heat generators and thermal storages. All prosumers are linked with an adjustable district heating and cooling grid. The modular hardware and control architecture presented in this paper covers management-, automation-, field-level control and offers interfaces to external control. A case study shows that prosumer integration into flexible district heating grids can reduce overall heating costs but requires intelligent control concepts for transfer stations and heat generators. The conducted experiments emphasize the importance of validating control strategies in laboratory environments. They allow the analysis of phenomena that are difficult and impractical to model accurately with existing simulation tools. The structure and capabilities of the laboratory are presented in order to foster collaboration with other researchers.

Dynamic pricing and the flexible consumer – Investigating grid and financial implications: A case study for Germany

Due to the ongoing expansion of renewable energies and the increasing energy demand of household consumers, e.g., due to the electrification of the mobility and heating sectors, grid bottlenecks and voltage band violations in low-voltage grids in Germany are expected to occur more frequently in the future. Dynamic pricing, implemented through digitization, is seen as one option to incentivize flexible and responsive electricity use of household consumers. Flexible consumption of household consumers could make grid utilization more efficient. So far, most studies on the effects of dynamic pricing focus on only one tariff for all household consumers within one low-voltage grid, whereas, in reality, households are free to choose between many different static and dynamic electricity tariffs. As previous studies have shown, the choice of tariff plays a major role in how flexibility is used. To address this research gap, we developed a model which integrates households and their static and flexible consumption and generation units into a home energy management system (HEMS) and minimizes the households’ power purchase costs. The model considers a range of dynamic tariffs that are already available today and includes the decision-making of heterogeneous household customers regarding the choice of tariff. Load flow calculations are then used to determine and analyze the effects on a low-voltage grid area. With this methodology including the free choice of tariff we go beyond the state of the art and paint a more realistic picture of the effects of dynamic tariffs on low-voltage grids. Our results show that, even though dynamic tariffs lead to increased peak demand at the level of individual households, peak loads are spread more widely within a grid area as the result of households choosing different tariffs based on economic considerations. Due to these effects, dynamic pricing has positive effects on grid utilization and could reduce the need for grid expansion.

Solderable conductive paste for electronic textiles

Background: In recent years, electronic textiles (e-textiles) have attracted widespread attention due to their versatility, but still lack a good packaging technique. Soldering, one of the electronic packaging technologies, has been widely used to provide electronic joints with good electrical and mechanical properties. However, direct soldering on e-textiles has to overcome several problems, such as melting at high soldering temperature and non-solderability of printed conductive patterns.Methods: The thermal stability and wettability of the resin were enhanced by adjusting the formulation to provide a base polymeric adhesive material. The formulated polymeric resin was then mixed with 85 wt% metal fillers to reach good conductivity after curing. A surfactant was also added to enhance particle dispersion and lowered the paste viscosity to screen print complicated conductive patterns on textile materials.Significant findings: The printed thin film showed good solderability with a low wetting angle for solder melt. A layer of intermetallic compound (Cu6Sn5) was found between solder and solderable patterns, which provided a great adhesion strength and peel strength on fabrics. Solder joints on the printed conductive adhesive also showed great shear strength. The solderable paste was printed into a heating grid on textiles to show good electrical interconnectivity with solder joints. In summary, this study provides a general guideline for the preparation of solderable paste and can be extended for other packaging applications in electronic textiles.

Entrained flow gasification-based biomass-to-X processes: An energetic and technical evaluation

A large number of process routes is available for the production of sustainable energy carriers from biogenic residues. Benchmarking these routes usually suffers from a lack of comparable performance data. The present work addresses this through a comprehensive model-based comparison of various biomass-to-X routes. Herein, seven routes (methanol, synthetic natural gas, dimethyl ether, Fischer-Tropsch syncrude, ammonia, and hydrogen with and without carbon capture) are modelled in detailed Aspen Plus® simulations. The evaluation itself is based on various key performance indicators, which capture both energetic (i.e. energy yield and usable heat per feedstock) and material-based (i.e. carbon and hydrogen conversion efficiency, and CO2 emissions) properties of the routes. The results show, that no simple correlations can be drawn between energetic and material-based indicators. In summary across all considered properties, the methanol route exhibits the best combined results, in particular with the highest carbon efficiency of 40 %. Fischer-Tropsch is more suitable for integration into existing industrial parks due to the lowest energy yield of 40 % with a lot of by-product formation and the highest amount of useable heat per feedstock of 211.3kWMW-1. Whereas dimethyl ether and synthetic natural gas have potential for integration into heat grids, mainly due to their good conversion and simultaneous large heat dissipation. Ammonia and hydrogen should only be considered in combination with carbon capture. Therefore, the key performance indicators determined herein must be considered together with project- and location-specific requirements and the market outlook for the product.

CO[formula omitted] handling in binary geothermal systems — A modelling approach for different CO[formula omitted] contents, salinity, pressure and temperature conditions

The decarbonisation of power and heat production is recently one of the major challenges in the Energy sector. Among other technologies, deep geothermal energy is an interesting option, because source temperature, plant capacity, low environmental footprint and high availability allow the application in district heating grids. The majority of geothermal reservoirs contains a certain amount of non-condensable gases dominated by CO2. With respect to corrosion and precipitation effects as well as environmental friendliness and economic optimisation, the handling of these gases is challenging.In this study three different technical options – a gas bypass system, a certain pressure regime and a secondary gas turbine – are investigated to overcome this challenge. The geothermal plant at Bruchsal/Germany was selected as case example for process simulation and further analyses.The major outcome shows that a gas bypass excluding CO2 from the power plant results to be the best option for the existing plant in terms of avoiding CO2 emissions and reaching highest possible power output. Furthermore, the study results recommend the best CO2 handling solution for different conditions within the simulated range (temperatures from 100 to 160 °C, salinity from 0–200g/L, pressures from 15–135bar, and flow rates until 100kg/s) as an essential contribution to the field.

Decentralised multi-grid coupling for energy supply of a hybrid bus depot using mixed-integer linear programming

The present work refers to two current problems in the context of achieving Greenhouse gas (GHG) neutrality: first the curtailment of renewable, volatile power generation units and secondly the high share of the mobility domain in total GHG-emissions. Both problems can be countered by a decentralised, smart energy system that supplies electricity, gas and heat to a hybrid public transport bus fleet and is simultaneously coupled to the public gas grid, public electricity grid and the district heating grid (Multi-Grid-Coupling). The enabling energy conversion unit is a reversible solid oxide cell (rSOC), which is operated in combined heat and power (CHP) mode or in power-to-gas (P2G) mode. P2G is primarily a solution approach for the first-mentioned problem and can thus successively lead to the replacement of fossil energy sources. Furthermore, by integrating industrial waste gases – as a necessary CO2 source for the P2G process – an additional benefit is gained from the CO2 that is emitted anyhow. The hybrid bus fleet constitutes an ecological alternative concept in public transport and therefore addresses the second-mentioned problem. The system, developed under the current state of the art technologies and the current ecological and economic conditions for Europe and Germany, can be operated profitably from the perspective of the system operator. This applies to the economically and ecologically optimised operating schedule of the controllable system elements such as the electrical, thermal and compressed gas storages, rSOC, compressor and the energy exchange with the public grids. To derive the optimal operating schedule of the cross-sectoral system, a mixed-integer linear programming (MILP) model is implemented and simulated under the current legal situation.

Demonstration of a concentrated solar power and biomass plant for combined heat and power

This study presents the design and performance of the Brønderslev hybrid plant – the world’s first concentrated solar power (CSP)-biomass plant to utilize waste heat. The combined heat and power plant consist of a 16.6 MW parabolic trough collector field, two 10 MW biomass boilers, and an organic Rankine cycle (ORC) system with an electrical output of 4 MW. The solar collector field and biomass boilers are hydraulically connected and supply heat in parallel to the ORC system. A multi-stage heat recovery process ensures that the waste heat is supplied to the local district heating grid. The solar field can also be operated independently of the biomass plant, supplying heat directly to the district heating grid. The plant operation was investigated by analyzing measurements for 2020, and the monthly heat and electricity generation was calculated for each component. Additionally, the performance of the solar field and ORC was elucidated, and the ORC was found to have a maximum electrical efficiency of 20.6 %. Detailed results are shown for one day with joint heat supply to the ORC from the solar field and biomass boilers, and the corresponding energy flows are visualized using a Sankey diagram. The total efficiency of the biomass plant for the investigated year was 93.6 % based on the higher heating value of the fuel. Overall, it was found that the hybrid plant performed reliably and successfully demonstrated the potential of CSP-biomass hybridization.

Techno-Economic Optimization Study of Interconnected Heat and Power Multi-Microgrids with a Novel Nature-Inspired Evolutionary Method

The world is once again facing massive energy- and environmental challenges, caused by global warming. This time, the situation is complicated by the increase in energy demand after the pandemic years, and the dramatic lack of basic energy supply. The purely “green” energy is still not ready to substitute the fossil energy, but this year the fossil supplies are heavily questioned. Consequently, engineering must take flexible, adaptive, unexpected directions. For example, even the natural gas power plants are currently considered “green” by the European Union Taxonomy, joining the “green” hydrogen. Through a tight integration of highly intermittent renewable, or other distributed energy resources, the microgrid is the technology of choice to guarantee the expected impacts, making clean energy affordable. The focus of this work lies in the techno-economic optimization analysis of Combined Heat and Power (CHP) Multi-Micro Grids (MMG), a novel distribution system architecture comprising two interconnected hybrid microgrids. High computational resources are needed to investigate the CHP-MMG. To this aim, a novel nature-inspired two-layer optimization-simulation algorithm is discussed. The proposed algorithm is used to execute a techno-economic analysis and find the best settings while the energy balance is achieved at minimum operational costs and highest revenues. At a lower level, inside the algorithm, a Sequential Least Squares Programming (SLSQP) method ensures that the stochastic generation and consumption of energy deriving from CHP-MMG trial settings are balanced at each time-step. At the upper level, a novel multi-objective self-adaptive evolutionary algorithm is discussed. This upper level is searching for the best design, sizing, siting, and setting, which guarantees the highest internal rate of return (IRR) and the lowest Levelized Cost of Energy (LCOE). The Artificial Immune Evolutionary (AIE) algorithm imitates how the immune system fights harmful viruses that enter the body. The optimization method is used for sensitivity analysis of hydrogen costs in off-grid and on-grid highly perturbed contexts. It has been observed that the best CHP-MMG settings are those that promote a tight thermal and electrical energy balance between interconnected microgrids. The results demonstrate that such mechanism of energy swarm can keep the LCOE lower than 15 c€/kWh and IRR of over 55%.

Environmental assessment of a heating, cooling and electric energy grid from a geothermal source in Southern Italy

The development of human societies, of lifestyles and of technologies are responsible for increasing trends of the worldwide energy consumption and of the related greenhouse gas emissions, in addition to a widespread energy inequality. Therefore, novel solutions are much needed to address the global need for energy without further degrading natural and urbanized ecosystems. This work proposes a sustainable medium enthalpy geothermal system in Campania region, Southern Italy, capable of generating electricity and thermal energy with low environmental impacts. The electricity, produced by means of an Organic Rankine Cycle (ORC), is sent to the Italian electricity grid. The thermal energy is used for providing district heating and cooling to office and residential buildings. The designed system is assessed by means of the life cycle assessment method, in order to understand the kind, amount and hot spots of the related environmental burdens. The current heating and cooling configuration in the considered buildings is compared to possible improvement scenarios and to the investigated case study, while the generated electricity is compared to the conventional electricity production from the Italian mix. In both cases, the investigated system shows significant benefits, performing better than common energy systems, with reductions of around 90% in terms of impacts on different environmental compartments.

Simulative comparison of concepts for simultaneous control of heat flow and outlet temperature of heat exchangers for highly flexible use in the test facility “District LAB”

An important measure for decarbonising the heating sector is the transformation of existing district heating (DH) systems into low-emission heating grids based on renewable heat sources. The test facility for DH applications “District LAB (D-LAB)” is currently being set up in order to support the transition by enabling the experimental investigation of various transformation measures. It consists mainly of a Flexible Heating Grid (FHG), which connects several decentralised Hardware-in-the-Loop (HIL) and is fed by a central generation plant. The HIL units in the FHG should be able to map almost any heat producer or consumer, so that a wide range of investigation scenarios is possible. In order to fulfil this requirement, the Heat Exchanger (HEx) that connects the HIL units with the FHG must extract or feed a defined heat flow from the grid and at the same time ensure a defined secondary-side outlet temperature. In a literature research conducted to the best of our knowledge, it turned out that in all technical applications only one outlet temperature is controlled. Therefore a suitable control concept had to be developed. This has been done by extensive simulative investigations, which are presented in this paper. Two control concepts, (I) “decoupled PID controller”, (II) “Characteristic Field (CF)-Based Control”, were self-developed and compared with each other. In order to represent a large spectrum of possible operating conditions with regard to the transformation of DH systems, 48 investigation scenarios based on target value steps were defined and used for the comparison. Subsequently, the average performance using the Root Mean Square Error (RMSE) as well as the time dependant step responses were examined. It turned out that, the CF-based concept appears to be more suitable for use in the D-LAB. It is conceivable that these results can also be transferred to other test facilities in which both, the heat flow and one outlet temperature need to be controlled.

An agent-based model to support the preliminary design and operation of heating and power grids with cogeneration units and photovoltaic panels in densely populated areas

The increase in the energy demands of residential neighborhoods constitutes a huge challenge to be faced. A viable option lies in the insertion of both renewable energy production systems and cogeneration units within urban territories. On-site production allows for the satisfaction of the heating and electrical demands of end-users and favors the distribution of produced energy within the neighborhood, especially under the regulatory framework of energy communities. This paper proposes a tool to model heating and electricity networks integrated with cogeneration units and PV panels installed in urban areas. The tool accounts for the following possibilities: (i) energy flow management and power sizes of both heating and electric networks, and (ii) evaluation of the electricity sharing configurations arising within energy communities. To better clarify the capability of the tool in supporting energy analysts and decision-makers, a densely populated area in Southern Italy is proposed as a case study. Regarding thermal distribution, results demonstrated that it is better to plan pipelines extended up to 300 m to take full advantage of the insertion of the CHP in the areas. Different considerations apply to the electrical distribution; here, an energy community extended over a geographical area with a radius of around 100 m is sufficient to guarantee an almost fully connected grid and obtain in any case exceeding production to be released to the centralized network.

Participation of Grid-Connected Energy Hubs and Energy Distribution Companies in the Day-Ahead Energy Wholesale and Retail Markets Constrained to Network Operation Indices

In this paper, the optimal scheduling of energy grids and networked energy hubs based on their participation in the day-ahead energy wholesale and retail markets is presented. The problem is formulated as a bilevel model. Its upper level minimizes the expected energy cost of electricity, gas, and heating grids, especially in the form of private distribution companies in the mentioned markets, in the first objective function, and it minimizes the expected energy loss of these networks in the second objective function. This problem is constrained by linearized optimal power flow equations. The lower-level formulation minimizes the expected energy cost of hubs (equal to the difference between sell and purchase of energy) as an objective function in the retail market. Constraints of this model are the operation formulation of sources and active loads and the flexibility limit of hubs. The unscented transformation approach models the uncertainties of load, renewable power, energy price, and energy demand of mobile storage. Then, the Karush–Kuhn–Tucker approach and Pareto optimization technique based on ε-constraint are adopted to extract the single-level single-objective formulation. Finally, obtained results verify the capability of the present method in improving the economic status of hubs and the economic and operation situation of the mentioned networks simultaneously so that the proposed scheme by managing the power of energy hubs compared with power flow studies has been able to reduce operating costs by 8%, reduce energy losses by 10%, and improve voltage profile and temperature by 36% and 30%.

The benefits of 4th generation district heating and energy efficient datacentres

This paper identifies the energy system benefits of transitioning district heating infrastructure from current 3rd generation district heating (3GDH) to 4th generation district heating (4GDH) with lower grid temperatures and more integration with other energy sectors. Previous papers have investigated the effect of going from 3GDH to 4GDH on a local perspective. In this paper it is investigated how this transition affects the energy system on a national level, where both the costs and energy effects are evaluated based on national hourly energy systems simulations including all energy sectors in a climate neutral energy system scenario. Moreover, the paper identifies the effects of different cooling solutions in datacentres. The analyses include effects on heat sources as well as the effect on the cost and losses in the district heating grid. This is done for the case of Denmark. In the case of Denmark, it is found that transitioning from 3GDH to 4GDH decreases the system cost by 220 M EUR/year, corresponding to 7 M EUR/TWh delivered heat at the end-user. Increasing the temperature outlet of datacentre waste heat has a value for the system as high as 52–59 M EUR/year, corresponding to 1.7–1.9 M EUR/TWh delivered heating at the end-user.

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.

Planning to grow, planning to rock on – infrastructure management and development in shrinking municipalities

ABSTRACT Previous work on shrinking cities has mainly addressed shrinkage and its effects in large and former industrial cities and not as much in municipalities in rural areas. In this paper, we focus on infrastructure challenges, responsibilities, and growth strategies in Swedish municipalities. We argue that there is a tension between the responsibilities connected to the municipal operations and infrastructure challenges posed by being a shrinking municipality on the one hand, and the ways the municipalities are planning for growth on the other hand. The municipalities are all struggling with the effects of population decline, leading to economic strains in all areas, including infrastructure management and development, but investments in infrastructure are many times directed towards the establishment of specific industries such as the tourism or mining industry with the belief of attracting new inhabitants, visitors, firms and industry. In addition, many of the municipalities lack the capacity and jurisdiction needed to manage the infrastructure development in some areas such as fibre optics, district heating, and electricity grids. Also, in some municipalities, the populations are spread over large geographical areas but must still provide infrastructure services to all inhabitants.

Research on Optimal Energy Flow Calculation of an Electro-Thermal Coupled System via an Interior-Point Approach

With the contradiction between energy consumption and ecological protection becoming increasingly prominent, it has become a serious issue to study an energy system with high efficiency, low pollution, and strong controllability. The application of the backpressure unit and the peak-shaving electric boiler makes the power grid and the heat grid connected and becomes an electro-thermal coupling system, which can be studied as a representative of the integrated energy system. In this study, to make full use of energy, a power system model considering a large number of distributed energy injections and a multi-source thermal system model are constructed. After the energy flow is solved, the optimization method of the electrothermal coupled system is studied to minimize the fuel consumption and obtain the minimum operating cost. In addition, a more comprehensive algorithm is proposed in this study, and the actual model is used in the fourth section of the article to verify that the algorithm can be practically applied.

Unlocking the Flexibility of District Heating Pipeline Energy Storage with Reinforcement Learning

The integration of pipeline energy storage in the control of a district heating system can lead to profit gain, for example by adjusting the electricity production of a combined heat and power (CHP) unit to the fluctuating electricity price. The uncertainty from the environment, the computational complexity of an accurate model, and the scarcity of placed sensors in a district heating system make the operational use of pipeline energy storage challenging. A vast majority of previous works determined a control strategy by a decomposition of a mixed-integer nonlinear model and significant simplifications. To mitigate consequential stability, feasibility, and computational complexity challenges, we model CHP economic dispatch as a Markov decision process. We use a reinforcement learning (RL) algorithm to estimate the system’s dynamics through interactions with the simulation environment. The RL approach is compared with a detailed nonlinear mathematical optimizer on day-ahead and real-time electricity markets and two district heating grid models. The proposed method achieves moderate profit impacted by environment stochasticity. The advantages of the RL approach are reflected in three aspects: stability, feasibility, and time scale flexibility. From this, it can be concluded that RL is a promising alternative for real-time control of complex, nonlinear industrial systems.

A new multigenerational solar energy system integrated with near-zero energy building including energy storage–A dynamic energy, exergy, and economic-environmental analyses

The main objective of this study is to propose and analyze a multi-generation system to cover heating, electricity, and water demands of a building in St. Petersburg (Russia). The main energy source of the system is solar energy to integrate with hydrogen energy storage system (HESS), and multi-effect desalination (MED). Hot water storage tank, and hydrogen energy storage system are used to store solar energy as heating and electricity, respectively at peak solar radiation. The stored energy will be used at off-peak hours to supply the demands of the building. Photovoltaic-thermal (PVT) collectors are used to cover heating load of the building and parabolic trough collectors (PTC) are suitable for providing heat demand of MED and HESS. In order to supply whole demands, auxiliary systems such as a heater for heating load and grid for electricity load are used whenever even storing systems are unable to cover them. The tools used for analyzing the proposed system dynamically are a comprehensive approach of energetic, exergetic, and economic-environmental under fixed conditions. Results of the transient analysis show that the proposed system can cover up to 70% and 57.9% of the electricity and heat demands, respectively, without any auxiliary system. At the same time, all the annual demand of the required freshwater of the building and the HESS is supplied by the proposed system. Moreover, the energy and exergy efficiencies of the integrated system with constant input parameters are obtained equal to 20% and 7%, respectively. Finally, by economic analysis, it is found that the net present value (NPV) of the proposed system, assuming an interest rate of 3%, becomes positive after 9 years.

Energy, exergy and economic investigation of operating temperature impacts on district heating systems: Transition from high to low-temperature networks

District Heating (DH) systems, owing to their remarkable techno-economic benefits compared to decentral heat production methods, are getting more and more popular worldwide. Today, DH systems are much more efficient than in the past but investigations show that there is still much to explore for more benefits and higher efficiencies considering such systems, where lowering the operating temperature is one of the points with the highest potential advantages. This study evaluates the effects of using different levels of operation temperatures of DH systems. For making the assessments quantifiable, specific case study DH network with a CHP plant as the main tool of supply is considered for the analyses. Three different design scenarios for the system are considered for all of which the results of the energy, exergy, and economic analyses are presented for the subsystems and the whole heat grid. Through thermoeconomic analysis, the unit exergy costs of electricity and heat and unit exergy costs of Space Heating (SH) and Domestic Hot Water (DHW) are determined. The results showed that lowering the operating temperatures increased the overall energetic and exergetic efficiencies of the CHP-supplied DH system, while reduced the cost per exergy unit associated with the SH and DHW supply.