Design Of District Heating Systems Research Articles

Return-Temperature Reduction at District Heating Systems: Focus on End-User Sites

This review presents a comprehensive examination of recent advancements and findings related to return-temperature reduction in District Heating (DH) systems, with a focus on enhancing overall system efficiency at end-user sites. The review categorizes and clarifies various return-temperature reduction techniques, emphasizing aspects such as building energy performance, heat emitters, thermostatic radiator valves, and substation units. One shall note that return temperature is not a parameter that can be directly controlled within a DH system; instead, it is influenced indirectly by adjusting various system parameters throughout the design, commissioning, operation, and control phases. Key insights include the direct impact of heat demand on return temperatures; the pivotal role of indoor heating systems in optimizing thermal energy use in relation to heat demand; the significance of thermostatic radiator valves in regulating heat output and maintaining low return temperatures; the advantages of ventilation radiators and add-on fans in enhancing radiator efficiency; the necessity for effective substation operation to improve system cooling capacity; and the critical role of operational control strategies in achieving optimal system performance. These findings underscore the need for integrated approaches in DH system design and operation to achieve lower return temperatures and improve overall system efficiency.

Novel multi-level optimization of district heating systems: Managing spatial scale and equipment portfolio design

The design of district heating systems often involves the consideration of the appropriate system scope, referred to as spatial scale. In order to achieve climate-neutral heating in neighborhoods, it is necessary to address spatial scale in the early planning stages. This study presents a novel optimization method aimed at sustainable dimensioning of the district heating system by optimizing the system type, scope, and equipment simultaneously. The method quantifies the spatial scale of targeted district heating system and assists in the decision between decentralized and centralized systems by using clustering algorithms and the genetic algorithm. The proposed approach was rigorously tested in a city-scale case study against centralized pipe network and standalone approaches. Our findings reveal that the proposed methodology outperforms traditional threshold methods and fixed-scope optimization through a three-group comparative study, culminating in a globally optimal solution for district heating systems.. Finally, the study offers insights into the intricate interplay between energy systems and district heating network scopes, underscoring the pivotal role of spatial scale considerations in the design of district heating systems toward climate-neutral paradigms.

Design of district heating system with dual-temperature supply based on thermal energy discretisation and matching method

As heating requirements continue to evolve and heating technology advances, radiators and radiant floor heating devices, which require different supply-water temperatures, have gradually become the two main heating terminals in district heating systems. However, the primary return-water temperature of current solutions based on heat exchangers and heat pumps is relatively high and fails to recover waste heat from the combined heat and power plants, owing to improper use of heat sources. To address this issue, a heat exchanger network optimisation method—the thermal energy discretisation and matching method—was used to design a dual-temperature water district heating system consisting of two absorption heat pumps and two heat exchangers. The primary supply water flows through the two generators, two heat exchangers, and two evaporators of the absorption heat pumps. The radiator and floor heating return water was divided into two parts and heated by the heat exchanger and the absorber and condenser of the absorption heat pump, respectively. The performance of the designed heating station was evaluated using the coefficient of performance and the primary return-water temperature and compared with that of other district heating systems. The changes in the district heating system's configuration when the boundary conditions changed were investigated. Results showed that (1) the designed system based on thermal energy discretisation and matching method -had the lowest primary return-water temperature of 18.8 °C and the highest coefficient of performance of 5.62. (2) When the low-temperature load ratio changed from 0% to 100% while maintaining a constant total load, the system's form changed regularly. (3) When the primary supply-water temperature increased, the heating station's form remained unchanged and the capacity of the heat exchange equipment changed regularly. (4) When the secondary supply and return-water temperatures increased, the evaporation temperature of the absorption heat pump increased, resulting in a change in the system's form. This study provides valuable insight into the design of district heating systems that supply dual-temperature water under various design conditions.

Developing an equipotential line method for the optimal design of an energy station location in a district heating system

The district heating system with distributed variable-frequency speed pumps (DVFSP) can provide substantial energy savings. Moreover, the energy station location has a great impact on the capital expenditure of heating system. Therefore, to determine the optimal energy station location in DVFSP system, this paper initially built a theoretical model of a DVFSP district heating system based on a cost-oriented index. Subsequently, an equipotential line method was illustrated and applied to a case study. This novel method can intuitively present the district distribution of the relative cost (RCnetwork) of DVFSP district heating system, which can conveniently determine the optimal location of an energy station. In the case study, six oval equipotential RCnetwork lines were described. The maximum RCnetwork reached 137.04% in the E4 location, and the minimum RCnetwork was 89.22% in the E11 location. The results showed that the optimal energy station location was near the district load center and biased to the side with higher building loads. Finally, a new energy utilization mode that coupled a combined cooling, heating and power (CCHP) system and a DVFSP district heating system was proposed. Economic analyses were carried out for the coupled system based on the following electric load (FEL) strategy and the following thermal load (FTL) strategy. The results confirmed that, in terms of the payback period and partial load rate (PLR) of the prime mover, the FEL strategy was more suitable for the coupled system. These results can provide guidance for district heating system design and management.

Bottom-up and top-down heat demand mapping methods for small municipalities, case Gllogoc

The identification and spatial distribution of heat demand for space heating is of high importance for the planning and design of district heating systems because around 70–80% of total final energy consumption by the household sector is consumed for space heating purposes. The aim of this research is the quantification and validation of heat demand distribution within a small municipality using a newly developed Bottom-up and Top-down heat mapping method. The Bottom-up mapping method is based on building features such as surface floor area, building height, building use and the share of the heated area while the top-down mapping method relies on energy balances and population distribution densities. These mapping methods are based on a GIS analysis of heat demand with high spatial resolution grids 100 m × 100 m. Two bottom-up scenarios have been created, one of which overestimate and the other which satisfy the actual heat demands of the buildings and the results of both are compared with the top-down analysis to quantify the impact of the assumptions and input data on the final result.

Development of a software platform for the design of district heating systems

The paper presents a new methodological approach to developing a universal platform for the design of district heating systems. The reasons for the development of the platform are considered and a scientific statement of the problem is given. The main methodological results obtained during the development of the platform are presented. The description of the scientific and practical significance of the results is given. A new methodological approach was developed using modern information technologies. The methodological approach is based on the paradigm of Model-Driven Engineering. The essence of this paradigm is that the software is generated on the base of formal description provided by the models. The proposed approach allows one to successfully solve the problem of separation of methods for solving applied problems and models of elements of a district heating system. The paper describes the developed architecture of the software platform. A description of the architectural subsystems of the platform is presented: the computing subsystem and the graphics subsystem.

Evaluation of design objectives in district heating system design

Energy system design is complex and the long utilization time of plants and the variance in economic parameters induce uncertainty into the outcome. In this article, different design objectives in a mid-sized district heating system design are evaluated. A mixed integer linear multi-objective optimization model is formulated and solved for maximum profit, minimum exergy losses, minimum CO2 emissions, minimum district heat primary energy factor and minimum district heat primary exergy (PeXa) factor. Energy system design should include metrics that take externalities into account. A combination of profit, CO2 and primary energy factor is recognized as a feasible set of design objectives. Exergy losses do not represent sustainability viewpoint well in energy system design — PeXa method expands it to fit system evaluation better. Optimization models such as this may provide relevant information for system operators, and for setting policy actions.

Cost Assessment of a District Heating System in Northern Japan Using a Geographic Information–Based Mixed Integer Linear Programming Model

AbstractThis paper presents a geographic information-based mixed integer linear programming model for a district heating system design. The model minimizes the annualized investment and operation costs of the system, with the key results showing the optimal distribution network structure and optimal capacity and dispatch of heat plants. A network topology of nodes and edges, providing accurate geographic representation of the district, is generated using a geographic information system and acts as a constraint. A case study is conducted for a district in Hirosaki city, located in the northernmost prefecture of mainland Japan. The results demonstrate the considerable economic benefits of integrating locally available woodchips in heat-only boilers instead of using city gas due to lower fuel costs. Low temperature operation reduces the fuel costs due to less network heat loss compared to medium temperature operation, but it is overcome by the cost of the larger pipe size and the pumping power. Implementatio...

A feasibility and performance assessment of a low temperature district heating system – A North Japanese case study

This paper presents a high spatial resolution based method for design and operation of a low temperature district heating system and evaluates its feasibility and energy and exergy performance through case comparison. Selected case area is existing district in North Japan. The district heating system design and operation follows a bottom-up approach. The study scope takes into account the demand side, distribution and supply side where biomass CHP (combined heat and power) plant is selected as main supply source. Radiating floor heating system model is used to estimate building temperature requirement. Results indicate that low temperature heating is infeasible for non-residential buildings in North Japan at high loads. Improving building insulation decreases heating quality demand considerably. Low temperature district heating performs better than medium temperature, especially in terms of exergy efficiency, however requires a bit larger pipe diameter indicating cost trade-off between installation and operation cost. Implementing cascade configuration based on quality level of building energy demand results in highest system performance. Lower network temperature provides least net primary energy consumption primarily due to higher electricity generation of CHP plant. This transcends to favourable system exergy efficiency of low temperature operation due to high quality of electricity, increasing the exergy of the product.

Computer-aided design of district heating systems based on heat pump

Computer-aided design of district heating systems based on heat pump

Piping network design of geothermal district heating systems: Case study for a university campus

Geothermal district heating system design consists of two parts: heating system and piping network design. District heating system design and a case study for a university campus is given in Yildirim et al. [1] in detail. In this study, piping network design optimisation is evaluated based on heat centre location depending upon the cost and common design parameters of piping networks which are pipe materials, target pressure loss (TPL) per unit length of pipes and installation type. Then a case study for the same campus is presented.

District heating system design for a university campus

İzmir Institute of Technology campus is in use since 2000 and still under development. At present, heating is provided by individual fuel boilers. On the other hand, the campus has a geothermal resource in its borders with a temperature of 33 °C. Because of this low geothermal fluid temperature; heat pump district heating system is considered for the campus. As an alternative, fuel boiler district heating system is studied. Each heating system is simulated using hourly outdoor temperature data. For the simulations, a control system with constant flow rate and variable return water temperature is used and the main control parameter is the indoor temperature. Various heating regime alternatives have been studied for heat pump district heating system for the various condenser outlet temperature and geothermal fluid flow rate, and two of these alternatives are given in this study. Furthermore, economic analysis has also been done for each heating system alternative based on investment and operational costs. Results indicate that heat pump district heating system has the highest investment but lowest operational cost. The alternatives are evaluated according to internal rate of return method, which shows the profit of the investment and resulted that, the heat pump district heating system has minimum 3.02% profit comparing with the fuel boiler district heating system at the end of the 20-year period.