Optimising the operation of a district heating system

Policy instruments clearly influence the choice of production technologies and fuels in large energy systems, including district heating networks. Current Swedish policy instruments aim at promoting the use of biofuel in district heating systems, and at promoting electric power generation from renewable energy sources. However, there is increasing pressure to harmonize energy policy instruments within the EU. In addition, natural gas based combined cycle technology has emerged as the technology of choice in the power generation sector in the EU. This study aims at exploring the role of policy instruments for promoting the use of low CO2 emissions fuels in high performance combined heat and power systems in the district heating sector. The paper presents the results of a case study for a Swedish district heating network where new large size natural gas combined cycle (NGCC) combined heat and power (CHP) is being built. Given the aim of current Swedish energy policy, it is assumed that it could be of interest in the future to integrate a biofuel gasifier to the CHP plant and co-fire the gasified biofuel in the gas turbine unit, thereby reducing usage of fossil fuel. The goals of the study are to evaluate which policy instruments promote construction of the planned NGCC CHP unit, the technical performance of an integrated biofuelled pressurized gasifier with or without dryer on plant site, and which combination of policy instruments promote integration of a biofuel gasifier to the planned CHP unit. The power plant simulation program GateCycle was used for plant performance evaluation. The results show that current Swedish energy policy instruments favour investing in the NGCC CHP unit. The corresponding cost of electricity (COE) from the NGCC CHP unit is estimated at 253 SEK MWh−1, which is lower than the reference power price of 284 SEK MWh−1. Investing in the NGCC CHP unit is also shown to be attractive if a CO2 trading system is implemented. If the value of tradable emission permits (TEP) in such as system is 250 SEK tonne−1, COE is 353 SEK MWh−1 compared to the reference power price of 384 SEK MWh−1. It is possible to integrate a pressurized biofuel gasifier to the NGCC CHP plant without any major re-design of the combined cycle provided that the maximum degree of co-firing is limited to 27–38% (energy basis) product gas, depending on the design of the gasifier system. There are many parameters that affect the economic performance of an integrated biofuel gasifier for product gas co-firing of a NGCC CHP plant. The premium value of the co-generated renewable electricity and the value of TEPs are very important parameters. Assuming a future CO2 trading system with a TEP value of 250 SEK tonne−1 and a premium value of renewable electricity of 200 SEK MWh−1 COE from a CHP plant with an integrated biofuelled gasifier could be 336 SEK MWh−1, which is lower than both the reference market electric power price and COE for the plant operating on natural gas alone. Copyright © 2005 John Wiley & Sons, Ltd.

District heating system with power generation is integrated in the electricity system since combined heat and power (CHP) plants are used for heat supply. Nowadays, the changes happen in the electricity system and conventional CHP plant operation. They are caused by wide integration of renewable energy sources (RES) in energy production process, feed-in tariffs for RES, the implementation of market mechanisms, and the incremented requirement in energy efficiency and flexibility of power plants. This creates new opportunities and conditions for district heating (DH) and power system cooperation though the use of DH flexible technologies, i.e., power-to-heat (P2H) technologies (electric boilers (EB) and heat pumps). The use of P2H technologies is limited and they are not costs-efficient due to electricity tariff formed components. Two Targets of EB use at power plant are evaluated, omitting these components, to show the usefulness and significant of these technologies for conventional generation.

Gasification process integration with existing combined heat and power plants for polygeneration of dimethyl ether or methanol: A detailed profitability analysis

To answer the challenges presented by climate change, all aspects of our energy systems have to carry out a rapid transition towards decarbonisation. This is especially true for the European heating sector that still relies heavily on fossil fuels. District heating systems have been traditionally praised for their efficiency, but replacing old fossil fuel based combined heat and power (CHP) plants is an ongoing challenge, and also the sustainability of biomass as a large-scale option can be considered questionable. Small modular nuclear reactors are one of the potential sources of future CO2-free district heat production. We evaluate the suitability and cost-effectiveness of these plants for district heating through literature review and scenario modelling. The technical aspects of small modular reactors seem promising but there is still a significant amount of uncertainty around both their costs and deployability. The scenario modelling assesses the investment in 300 MWdh of new district heating capacity in the Helsinki Metropolitan area in 2030 either as a CHP plant or as a heat-only boiler. The results indicate that a modular nuclear heat-only boiler could be profitable, while profitable investment in a modular nuclear CHP plant relies heavily on future electricity market price levels.

A hierarchical dispatch method for tri-level integrated thermal and power systems

Modeling of combined heat and power plant performance with seasonal thermal energy storage

Cogeneration Cogeneration, also known as combined heat and power (CHP), describes the simultaneous production of both mechanical energy and useful heat from various sources of energy by a thermodynamic process in a technical plant [1, 2]. Combined heat and power plant (CHP Plant) A combined heat and power plant (CHP plant) or cogeneration plant provides simultaneously electricity and useful heat. Electricity generation efficiency Electricity generation efficiency or electrical efficiency is the ratio between the electricity output and the energy input of an energy conversion system.Whereas small-scale CHP plants with combustion engines feature electricity generation efficiencies of roughly 30%, large-scale CHP plants obtain up to 45% [3, 4]. Energy conversion efficiency Energy conversion efficiency or overall conversion efficiency is the ratio between the useful energy output and the energy input of an energy conversion system. For CHP plants, energy conversion efficiency is the sum of electricity conversion efficiency and heat conversion efficiency. Electrical and thermal auxiliary

The energy consumed by buildings for air conditioning accounts for a large percentage of global energy consumption. To promote efficiency and sustainability, the scientific community is making great efforts to develop renewable technologies. A well-known but unfortunately underestimated solution is the development of centralized heating and cooling systems that consistently reduce energy consumption.The work proposes a comparison between three heating configurations covering the demand of a settlement in the Latvian region: 1) centralized district heating (DH) system; 2) 5th generation district heating & cooling (5GDHC) system and 3) individual home heating (HH) systems. Thermal and electrical loads are evaluated by transient simulations of a residential area with 80 buildings for the Riga climate and compared with the same settlement in a Mediterranean region (Milan, IT). The energy plants are based on different technologies: combined heat and power (CHP) plants, gas-fired boilers, and domestic heat pumps.The analysis includes the option of power exchange with the national grid. A transient numerical model has been developed for each solution. Every component is modelled according to performance maps provided by the manufacturers, allowing an accurate simulation in both design and off-design operating conditions. The study includes energy, economic and environmental aspects.The result of the simulation highlights the large difference between the two locations, not only in terms of annual load, but also in terms of load distribution. On an annual basis, the Latvian residential complex requires almost twice as much energy as the Italian one. The thermal losses in the district systems are 4.21% in Milan solution and 5.65% in Riga. The district heating system coupled with heat pump represents the best layout in terms of primary energy consumption in both locations, with energy savings of 50% compared to other solutions. The use of 5GDHC is a good compromise that could increase the use of renewable energy. The adoption of cogeneration plant is a good choice in case of centralized district system that allows the installation of high efficiency genset. On the contrary, for small application as residential, the installation of cogeneration system results expensive and the conversion efficiency does not justify the installation.

Norway, like many countries, has realized the need to extensively plan its renewable energy future sooner rather than later. Combined heat and power (CHP) through gasification of forest residues is one technology that is expected to aid Norway in achieving a desired doubling of bioenergy production by 2020. To assess the environmental impacts to determine the most suitable CHP size, we performed a unit process-based attributional life cycle assessment (LCA), in which we compared three scales of CHP over ten environmental impact categories—micro (0.1 megawatts electricity [MWe]), small (1 MWe), and medium (50 MWe) scale. The functional units used were 1 megajoule (MJ) of electricity and 1 MJ of district heating delivered to the end user (two functional units), and therefore, the environmental impacts from distribution of electricity and hot water to the consumer were also considered. This study focuses on a regional perspective situated in middle-Norway's Nord- and Sør-Trøndelag counties. Overall, the unit-based environmental impacts between the scales of CHP were quite mixed and within the same magnitude. The results indicated that energy distribution from CHP plant to end user creates from less than 1% to nearly 90% of the total system impacts, depending on impact category and energy product. Also, an optimal small-scale CHP plant may be the best environmental option. The CHP systems had a global warming potential ranging from 2.4 to 2.8 grams of carbon dioxide equivalent per megajoule of thermal (g CO2-eq/MJth) district heating and from 8.8 to 10.5 grams carbon dioxide equivalent per megajoule of electricity (g CO2-eq/MJel) to the end user. Supporting Information S1: This supplement contains further details on life cycle assessment (LCA) methodology and the assumptions used for the case system, along with tables of the foreground life cycle inventories, contribution analysis for each product (1 megajoule [MJ] electricity and 1 MJ district heating to end user) for each impact category, and total environmental impacts at the combined heat and power plant (1 MJ useful energy at the plant). Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Waste management currently is a much-discussed topic. Waste should be treated in accordance with EU Directive 2008/98 EC. However, material recycling cannot be applied to all waste generated. It is not only for this reason that the construction of new waste-to-energy plants (WtEP) is being considered in many countries with high landfilling shares. When designing WtE projects, it is essential to assess their economic sustainability with regard to local conditions. Revenues from the sale of heat are one of the most important parameters for the economy of these facilities in the climatic conditions of Central Europe. This often involves the need to supply heat to an existing central district heating system (DHS). The paper presents a complex mathematical optimisation tool for integrated WtE assessment. It is a multi-period model, where the annual operation is analysed in 365 days. It is able to simulate the simultaneous operation of several heat sources (gas or coal boilers coupled with turbines), while respecting their design constraints and operation economy, such as the power range of individual boilers, turbines, variable operating costs and efficiency, etc. The tool is able to refine the estimate of the acceptable heat price and its amount from the WtEP through the change in the variable costs of heat production before and after the integration of the new WtEP. This is a key benefit compared to commonly used techno and economic models of WtEPs, which in most cases work with a simplified assumption that all heat produced can be utilised if its monthly output is lower than total demand in the DHS. As a result, the calculation of the minimum gate-fee or profitability of the project will be improved. The whole problem is the task of linear integer programming and is implemented in GAMS programming environment with the use of MS Excel for a user-friendly interface. The software functionality is presented in the second part of the paper on a real example of WtEP integration into existing DHS.

There are several barriers to increased use of biofuel in the transport sector (e.g., shortage of feedstocks, high production costs, and relatively low energy yields from standalone biofuel plants). One possible solution is integration of biofuel and district heating (DH) production. This study aims (1) to identify challenges (e.g. trade-offs) related to integration and to suggests possible ways of dealing with these challenges, (2) to highlight factors that may influence effects on global GHG emissions from integration, (3) to highlight factors which should be considered when evaluating economic aspects related to integration. After conducting a systematic review using a prescribed and structured protocol, 38 articles were identified as relevant for this study. These articles present four different approaches for integration: delivering the excess heat from biorefineries to DH networks, utilising DH in biofuel production processes, integrating biofuel production with existing DH facilities, and building new polygeneration biofuel production facilities in DH systems (DHS).If investments in biofuel compete with combined heat and power (CHP) production, the electricity price and the premium paid for renewable electricity influence profitability in CHP plants investments and therefore even profitability in investments in biofuel production. Competition should also be considered when weighing environmental benefits (the influence on global GHG emissions). Competition can create trade-offs related to DHS’s operating conditions, limited local and global biomass availability, and limited available heat sinks. To deal with these trade-offs and to avoid suboptimization, stakeholders in regional planning, investors and policymakers should cooperate.All identified studies noted that a comprehensive approach is needed to evaluate profitability aspects and effects on global GHG emissions.For instance, utilising excess heat or residues from a biofuel production process in a DHS requires consideration of alternative DH production and alternative fuels. If electricity is one of the by-products from the biofuel production, alternative electricity production should also be considered. The majority of the studies dealt with economic performance of integration. Some of the factors found to influence profitability include available heat sink, alternative DH and electricity production, expected operation patterns, energy policy and energy market conditions. The potential for reducing global greenhouse gases (GHG) emissions depends on alternative DH and electricity production but also on biomass availability and alternative biomass users.

Integration of solar thermal systems in existing district heating systems

In 2021, the global electricity and heat sector recorded the highest increase in carbon dioxide (CO2) emissions in comparison with the previous year, highlighting the ongoing challenges in reducing emissions within the sector. Therefore, combined heat and power (CHP) plants running on renewable fuels can play an important role in the energy transition by decarbonising a process, increasing the efficiency and capacity factor. Since 2003, Luxembourgish CHP plants have been transitioning from natural gas to biomass, mainly wood pellets. However, even though wood pellets are a renewable alternative, the market volatility in 2022 highlighted the vulnerability of a system reliant solely on one type of fuel. This study assesses the feasibility of using hydrogen to decarbonise a cogeneration plant powered by a natural gas-fuelled internal combustion engine. Although the technology to use hydrogen as a fuel for such systems already exists, a technical and economic analysis of implementing a hydrogen-ready plant is still lacking. Our results show that, from a technical perspective, retrofitting an existing power plant to operate with hydrogen is feasible, either by adapting or replacing the engine to accommodate hydrogen blends from 0 up to 100%. The costs of making the CHP plant hydrogen-ready vary depending on the scenario, ranging from a 20% increase for retrofitting to a 60% increase for engine replacement in the best-case scenarios. However, these values remain highly variable due to uncertainties associated with the ongoing technology development. From an economic standpoint, as of 2024, running the plant on hydrogen remains more expensive due to significant initial investments and higher fuel costs. Nevertheless, projections indicate that rising climate concerns, CO2 taxes, geopolitical factors, and the development of the hydrogen framework in the region—through projects such as MosaHYc and HY4Link—could accelerate the competitiveness of hydrogen, making it a more viable alternative to fossil-based solutions in the near future.

The district heating (DH) system of Greece, mainly supported from lignite fired stations, is facing lately significant challenges. Stricter emission limits, decreased efficiency due to old age and increased costs are major challenges of the lignite sector and are expected to result in the decommissioning of several lignite-fired units in the coming years. As a result, managers of DH networks are currently investigating alternative scenarios for the substitution of thermal power that it is expected to be lost, through the integration of Renewable Energy Sources (RES) into the system. In this paper, the DH systems of Kozani and Ptolemaida are examined regarding possible introduction of RES. The first study examines district heating of Kozani and alternative future options for covering a part of city’s thermal load whereas the second study refers to a biomass CHP plant (ORC technology, 1MWe, 5MWth) to be powered from a biomass mixture (wood chips and straw).

Metamorphoses of cogeneration-based district heating in Romania: A case study