Existing Heating System Research Articles

Experimental and Numerical Studies of Heat Transfer Through a Double-Glazed Window with Electric Heating of the Glass Surface

This paper presents experimental and theoretical studies of heat transfer through single- and double-glazed windows with electrical heating of the internal surfaces. Heating is achieved by applying a voltage to the low emissivity coating of the inner glass. A thermophysical model has been developed to simulate the heat transfer through these units, allowing us to determine their thermal characteristics. Experimental data are used to validate the numerical model. The resulting heat flux and temperature distributions on the external and internal surfaces of electrically heated double-glazed units are analysed. According to the results of experimental and numerical studies, it was found that the adopted electric heating scheme allows 83–85% of the heat to enter the room and 15–17% is removed to the outside. This makes it possible to increase the radiation component of the heat flow from the window to the room and improve the thermal comfort in the room. In general, this article shows that existing industrial windows with low-emissivity glass surface coating can be upgraded with simple and inexpensive modernisation, without compromising the main function of the window—efficient transmission of visible light—and create an additional (backup) heating device that can work effectively together with the existing heating system in the event of a sudden cold snap at low temperatures (below −20 °C), to prevent condensation of water vapour in the windows, and to prevent condensation on the surface of the window facade wall. Formally, a back-up (emergency) heating system is created in the room, which contributes to the energy sustainability of the building and therefore to energy security in general.

Retrofitting of the Italian precast industrial building stock. LCA analysis as decision-making tool

The challenging European goal concerns the achievement of a carbon-free economy by 2050 must necessarily consider the improvement of the construction sector along with the redevelopment of the existing buildings. In fact, according to a European report concerning existing buildings, 80% of the built environment will remain the same by 2050. Nowadays buildings are responsible for 30% of the global final energy consumption and 37% of global energy and process emissions. As regards industrial buildings, they account for 33% of global final energy demand. The research aims to define some effective retrofitting measures to be applied in the existing Italian industrial facilities to improve their both energy and environmental performance. Several redevelopment scenarios and their possible combinations related to external envelope technological solutions and systems are analysed. The different interventions are applied to an existing Italian industrial building chosen as a case study and are compared by Life Cycle Assessment (LCA) analysis considering different environmental indexes (GWP, AP, PERT and PENRT). The calculation of the primary energy demand is also performed. Phase B6 accounts for about 80% of the whole environmental impact calculated considering 20 years as building lifetime. The redevelopment scenarios that foresee the intervention on the external envelope are the most impactful ones in terms of the production phase (A1-A3). Those related to the existing roof are characterised by a significant impact due to the demolition, disposal and landfill of finishing panels made of asbestos. The configurations that include the substitution of the existing heating system with an air-to-air heat pump coupled with renewables to produce electrical energy on-site are the most advantageous ones. The latter make the industrial building carbon-zero thanks to the considerable amount of surplus electrical energy produced on-site. In this case, phase D mostly recovers the environmental impact of the whole life cycle considering the different indexes.

The role of practical knowledge in keeping existing systems: a qualitative study of Finnish homeowners with oil heating

The uptake of homeowner energy retrofits and related policy instruments are lagging behind targets. The Finnish government has decided on the phasing out of oil heating by 2035, but despite financial and other support for homeowners, only 14 per cent of homeowners with oil heating reported planning to switch their heating systems. Homeowner decision-making on energy investments is typically seen as an outcome of rational evaluation based on calculations about costs, payback times, and savings in energy and money. However, informal, experience-based knowledge contributes centrally to situations where people end up keeping their current heating system, yet there is little research on practical knowledge when households consider energy investments. This article presents findings from interviews with Finnish homeowners (N=29) living in detached houses with oil heating systems and argues that homeowners’ embodied heating habits and practical knowledge are important in understanding homeowner willingness to keep existing heating systems. In the in-depth interviews conducted in spring 2022, homeowners discussed their energy use practices, past renovations and future renovation needs, as well as concerns related to switching oil heating to a low carbon heating system. The findings suggest that homeowners’ practical knowledge on heating with their existing system and the lack of such knowledge in relation to alternative heating systems may be one reason why homeowners are reluctant to switch their heating systems. The study contributes to a growing body of research which highlights the relevance of everyday practices in homeowner energy renovations.

A simple load model based on hybrid mechanism and data-driven approach for district heating in building complex

Accurate prediction of heating loads in district heating systems is essential for the implementation of demand-driven heating. This work presents a novel heating load prediction model that is particularly suitable for complex multi-user buildings. The input characteristics of the model are established through the heat transfer mechanism, considering factors such as the cumulative impact of outdoor temperature and user demand (indoor temperature). The specific form of the heating load function is determined using the MLR-PSO (Multiple Linear Regression-Particle Swarm Optimization) method. Only the indoor and outdoor temperatures need to be provided for the model to calculate future heating loads. Practical engineering tests demonstrated that the model achieved normalized mean bias errors of daily loads between 4.98 % and 5.54 % across different heating seasons, with a minimum annual relative deviation of 0.75 % for annual loads. Additionally, the model helps guide the operation of heating systems. For example, during the 2021–2022 heating season, setting the target indoor temperature at 18 °C reduced weekly energy consumption by 15.3 % compared to the previous season. This approach may be employed to construct a simple load model for existing heating systems to accurately predict both short-term and long-term loads, providing valuable insights into the management and control of heating systems.

HAPPENING: an efficient cascade heat pump system for multifamily buildings

An innovative hybrid heat pump system is presented as a novel solution for multifamily building heating system retrofitting. This system is very efficient on the one hand thanks to its innovative configuration in cascade, minimum thermal losses and on the other hand, the maximization of local solar energy self-consumption due to decoupling generation and consumption and applying smart control strategies. It is aimed at facilitating retrofitting of existing heating systems in multifamily buildings, enabling an efficient decarbonization. Three variations of the system have been designed, installed, and tested in real buildings across Europe, within the H2020 project “HAPPENING”. The project is now under monitoring phase and the preliminary results are positive, demonstrating the high efficiency of the concept

Process design, performance comparison and operating test of the multi-stage vertical absorption heat exchanger realizing independent heating in three zones

Absorption heat exchangers applied in district heating systems can significantly reduce the outlet water temperature of the primary network, thereby expanding the heating scale and promoting low-temperature waste heat recovery. However, nearly 50% of the existing heating systems in high-rise buildings are divided into three independent zones. At present, there is a lack of research for absorption heat exchangers in this scenario. The main task of this paper is to address this issue to expand the application range of absorption heat exchangers. Firstly, two different processes are designed in this paper. The first process is to add a plate heat exchanger in the existing two-stage process, while the second process is a novel three-stage vertical process, consisting of three absorption heat pumps with different pressures and three sets of plate heat exchangers. Then, the operating performance, self-adjustment ability and the system cost of different processes are compared based on the simulation method. Although the price of Process 2 is 26.4% higher than that of Process 1, the efficiency of Process 2 is 20.3%-27.7% higher, and the self-regulation ability is significantly better. Thus, Process 2 has better overall performance. Moreover, the system development and operating test of Process 2 are conducted. Throughout the whole heating season, the overall efficiency of the system is 1.17–1.23. Without manual intervention, the relative standard deviations of the inlet water temperature of the secondary network and the actual heat supply rate ratio are less than 5% and 16% respectively, which proves that the system has great self-adjustment ability. The conclusions in this paper can guide the design and application of the absorption heat exchanger in three-zone independent heating scenarios.

Synthetic natural gas in the private heating sector in Germany: match or mismatch between production costs and consumer willingness to pay?

BackgroundThe residential heating sector in many European countries requires a fundamental transformation if it is to become climate neutral. Besides the introduction of efficiency measures and updating heating systems, scholars and practitioners consider replacing fossil fuels in existing heating systems a viable approach. Drop-in renewable gases such as biomethane and synthetic natural gas (SNG) cause considerably fewer carbon dioxide (CO2) emissions than natural gas and can be used in natural gas boilers, the dominant heating system in many European countries. To move the ongoing debate around e-fuels forward, this study reports on a Discrete Choice Experiment with 512 respondents in Germany that analyzed consumer preferences and willingness to pay (WTP) for SNG. I build on these insights by comparing WTP to the production costs, making evidence-based decision-making possible.ResultsThe results show that consumers prefer renewable gases over natural gas. Comparing the two types of renewable gases, SNG and biomethane, reveals that consumers clearly favor the latter despite the criticism it has come under in the last 10–15 years. Consumers show a surprisingly high WTP for increasing shares of SNG, with premia of 40 to almost 70% over a natural gas-based tariff. Comparing production costs to the WTP reveals that only tariffs with small shares of SNG (5% and 10%) can be offered at cost-covering prices.ConclusionsGiven the urgent need for a fundamental transition of the residential heating sector, marketers and policymakers should consider carefully whether it is worth channeling a rather unknown and expensive product like SNG into the voluntary market for heating gas, especially as biomethane is already established in the market and clearly a cheaper and more popular alternative.

RECONSTRUCTION OF HEATING SYSTEMS IN RESIDENTIAL BUILDINGS WHILE MAINTAINING EXISTING HEAT SOURCES

The purpose of the article is to substantiate the need for real reconstruction of single-pipe vertical centralized heating systems, which are operated in most multi-story residential buildings in Ukraine, into apartment horizontal systems. The paper presents the main design shortcomings of heating systems in residential buildings built in the second half of the 20th century. The feasibility of using horizontal apartment systems is substantiated. For the first time, the heating system was reconstructed during the heating season without displacing residents and without stopping the existing heating system. A technical solution is proposed for supplying heat to apartments from an existing individual heating station with an elevator without its reconstruction. The article presents the results of a number of studies aimed at improving the heating system and determining the indicators of its economic and energy efficiency. Installation work can be carried out selectively in any number of apartments, and "old" and "new" heating systems can operate in parallel. The methodology for the reconstruction of heating systems presented in this paper can be used in the process of post-war restoration of the destroyed infrastructure of the housing stock of Ukraine. Modernizing in-building systems while maintaining the existing heat source is much cheaper than decentralizing heat supply by installing independent heating systems with a gas boiler in each apartment. The main conclusions of the article include that the reconstruction of existing heating systems is an objective necessity, without which the subscriber's influence on his heat consumption is impossible. The modernization described in this article is dictated by all the regulatory deadlines for major repairs of heating systems, which in most cases are more than twice as long.

Thermal characteristics of resistive heating composite panels for the interior parts of railway vehicles

The pandemic of highly infectious diseases like COVID-19 has highlighted the vulnerabilities of public transportation. In particular, railways are more vulnerable due to their dense environment, and the heating system used in winter is a major factor in increasing the transmission and risk of the virus. To improve the existing heating system, a study was conducted to develop a resistive heating composite capable of radiant heating. In this study, the applicability of heating elements, heating performance, and internal thermal deformation factors of laminated panels and sandwich panels used as rail vehicle components were analyzed in detail to consider the actual application of this technology in the railway industry. The experimental results confirmed that both types of panels effectively heated above the target temperature (120℃) in the heating element layer, demonstrating uniform heating characteristics. Additionally, sandwich panel is more affected by thermal deformation compared to the laminate panel. These experimental results are expected to serve as essential foundational data for the effective utilization, safety, and reliability considerations of resistive heating composite materials in real industrial environments.

Development and optimization of an energy saving strategy for social housing applications by water source-heat pump integrating photovoltaic-thermal panels

Residential buildings account for 84 % of Italy's built environment, playing a pivotal role in the EU's aim to cut GHG emissions by 55 % through enhanced energy efficiency and climate adaptation. This necessitates comprehensive energy retrofit initiatives, especially in sectors like social housing, which has been relatively overlooked in terms of energy efficiency strategies. This study focuses on a multi-story building from the 1980s in Rome, implementing an innovative energy system proposed by the RESHeat European project. This system, aimed at standardizing energy retrofits for late 20th-century social housing, leverages the underexplored potential of water-source heat pump (WSHP) systems. The novelty of this research extends to its examination of multi-family housing, a sector that has seen less attention compared to public spaces and smaller residential buildings. Through experimental validation and annual dynamic simulations using TRNSYS and Simulink, the research compares the existing heating system with a proposed upgrade that includes a WSHP and Photovoltaic-Thermal (PVT) panels. This upgrade demonstrated a significant efficiency improvement, achieving an annual COP of 6.1 for the WSHP and a 36 % Primary Energy Savings (PES) from the PVT panels, showcasing the effectiveness of these technologies in enhancing the energy profile of multi-family residential buildings.

Моделирование системы управления отоплением дома с применением нейросетевых технологий

The aim of the work is to develop methods to improve the characteristics of existing heating systems through the use of a new control algorithm based on the parallel principle of operation and using neural network technologies. The proposed control method provides for the analysis by a special computer program of feature matrices consisting of both control actions and resulting maps. The computer, which knows in advance that different images correspond to different modes, selects the appropriate mode based on the image received at the program input. This mode can be selected in such a way that there will be minimal energy consumption while providing the conditions that the user needs. An application has been developed that uses a neural network algorithm, with the ability to change settings. Sets of images have been prepared indicating class membership by characteristic features (datasets), on which the neural network was trained and tested. More than 600 experiments with a different number of learning epochs have been performed. The influence of the number of epochs on the average percentage of image recognition of building temperature regimes has been studied. To demonstrate the possibility of implementing the proposed algorithm, a control system architecture and a distributed application consisting of a main control program with a human-machine interface and a remote web application with a human-machine interface and a microservice with an access point were developed. A mock-up of the building was made with a connected room temperature control system. The experiments carried out have confirmed the effectiveness of the proposed control method. This technology provides for the possibility of switching from managing a single building to managing an array of buildings without changing the management settings of individual buildings. Using this method will increase the convenience of management, the comfort of people's living conditions and reduce energy consumption for heating.

Methodology for Modernizing Local Gas-Fired District Heating Systems into a Central District Heating System Using Gas-Fired Cogeneration Engines—A Case Study

Sustainability can be achieved by improving process efficiency, among other methods. In the case of heat supply systems for cities, one of the ways to increase the efficiency of fuel use, and thus reduce resource consumption and greenhouse gas emissions, is the generation of heat and electricity in one process—the use of cogeneration (CHP). The main goal of this paper is to deliver the methodology for a step-by-step modernization process for local gas-fired heating plants through the use of gas cogeneration engines in common central district heating systems. The presented methodology was applied on the basis of a real system located in north-western Poland (case study from Białogard). The profitability of cogeneration was simulated against the background of changing gas prices. The financial and environmental profit from modernization was calculated. The technical requirements that had to be met in order to adapt the existing heating system to cooperation with the new energy source were also presented. The importance of selecting the supply and return temperature of water in the heating system after modernization was emphasized. Based on investment experience, we show that installing a cogeneration engine improves a company’s financial result by 33% (calculated as the difference between the revenue from the sale of energy and the cost of gas only) and is less harmful to the environment, among other benefits, significantly reducing CO2 emissions by 78%.

Analyzing excess heat factors of convective/radiant terminals: Balancing beginning and steady stage

With the improvement of living standards in China, space heating has become a focal point, where energy efficiency and thermal comfort play crucial roles in the utilization of heating devices. Addressing the limitations of existing heating systems, convective/radiant terminals have been developed to balance rapid heating during the beginning stage with sustained thermal comfort during steady stage. The convective-to-radiant unit ratio is a crucial determinant of terminal performance and a key design consideration. The excess heat factor represents the additional fraction of convective heat transfer during the initial stage. It is influenced by the excess load factor, a characteristic of building loads, specifically referred to as the excess heat factor in the design of convective/radiant terminals. This study utilized building energy simulations based on the time-series conduction transfer function by energy simulation software, considering various configurations such as enclosure structure, number of exterior walls, indoor set-point temperature, and the time required to reach the set-point temperature. Results indicate that an excess heat factor of 0.80 is technically and economically feasible based on daily operating factors and annual design factors. The research contributes valuable insights into optimizing terminal design for enhanced energy efficiency in the context of space heating. Two types of convective/radiant terminals, direct expansion, and heat pipe terminals were developed for preliminary validation, providing fundamental parameters for the specification of terminals.

Potential of Energy Saving of Propane Heat Pump as replacement of gas boilers with low and high temperature emitters

This work deals with the analysis of the energy performance and the environmental impact of a Heating, Ventilation and Air Conditioning (HVAC) system based on an innovative Air-to-Water electrical Heat Pump (AWHP) using propane (R290) as the refrigerant. A building of the University of Bologna located in Forlì (North of Italy) is considered for replacing a condensing gas boiler and a conventional chiller with an AWHP using R290. To evaluate the efficiency of the existing heating system and the potential savings linked to the adoption of the propane AWHP, the building energy model was created and calibrated by collecting monthly thermal and electrical consumptions as a function of the actual climate data. In this paper, the main features of the R290-based AWHP are described in detail by emphasising the device performance as a function of the operating conditions (i.e., air and water temperature and speed of the scroll compressor). A series of scenarios have been studied to evaluate the energy performance of the propane AWHP with respect to the reference scenario under various operating conditions. The results show that while the total primary energy demand increases adopting the propane AWHP with respect to the case of a gas boiler, the non-renewable primary energy fraction decreases significantly, with a dramatic increase in the renewable quote. From an economic point of view, lower annual costs are obtained by adopting a propane AWHP coupled to fan coils, mainly when the electrical heat pump is used in a thermally insulated building in which a photovoltaic system is installed.

Energy analysis of multi-source heat pump system: A real case study application

In the last years the HVAC sector has seen the growing interest in using the so-called multi-source heat pump systems. This type of plant aims to improve the energy performance of the heat pump. As widely known the heat pump represents the most promise solution in terms of potential for exploitation of renewable energies. The sun and air can be used as alternative sources to the ground during the middle season or when they are available and convenient, while the ground could be used during the peak periods of the seasons keeping good energy performances of the system. The present work summarizes the monitoring results of a large-scale experimental plant used for the air conditioning of a 100 m2 snack bar in Ferrara, Italy. The energy behaviour of the plant has been monitored for one year and its performance has been compared with the existing plant. The results have proved an energy saving between 20 % and 70 % in cooling mode. In heating the proposed plant is less competitive due to the share of renewable energy considered in the existing heating system. The work shows how these systems are potentially suitable for the electrification and decarbonisation process in the building sector.

Study into the efficiency of additive infrared heating of industrial buildings in areas with low outside temperatures

Heating of industrial buildings is a complex and labor-consuming task requiring major financial investments. The complexity of this task grows in the case of large-size construction objects and strict requirements to their reliability, economic performance, and energy efficiency. The problem is even more complicated in those Russian regions, where low temperatures remain for a longer period of time. Significant financial investments are caused by the wear and obsolescence of the existing heating systems, leading to enormous heat losses. Due to the large size of the considered property types, it is difficult to select heating equipment that could provide the required temperatures inside the building while meeting all the aforementioned requirements. The solution can be found in the currently popular industrial infrared heaters, which provide both uniform heating of the building or room in question under significant energy savings. The application of infrared heaters as the main heating system equipment makes it possible to organize zonal (additive) heating of buildings of any type and purpose allowing different air temperatures even inside a single room. In this paper, a numerical study of the efficiency of additive heating systems with gas infrared emitters was carried out using a warehouse building as an example. Based on the analysis of the obtained results, the economic justification of the proposed technical solution was provided.

Valorisation of Waste Heat in Existing and Future District Heating Systems

To recover thermal energy from different sources, its quality and possibilities for utilisation are essential. The wide range of engineering solutions includes a direct connection to the district heating (DH) system and the integration of low-quality heat using heat pumps to increase the temperature level of recoverable heat. Therefore, this article compares waste heat valorisation strategies for integration into existing DH networks, low-temperature DH, and ultra-low heat supply systems using the multi-criteria assessment method. In addition, a local scale assessment was performed to identify the waste heat role in existing RES-based DH systems. The results show that the highest waste heat valorisation rate could be reached when integrated into low-temperature DH systems due to high waste heat potential and suitable temperature conditions. However, a local scale assessment shows a significant impact on the already implemented solar technologies, as waste heat could cover around 70% of the summer heat load.

Carbon reduction options for churches using oil for heating

To limit global warming, a rapid reduction in the carbon emissions from our buildings is required. Heating buildings contributed to 17 per cent of the UK overall carbon emissions in 2018 which is why it is important we look to decarbonise the heating systems that serve our buildings. In 2020, only 7.9 per cent of the energy to heat our buildings came from renewable sources. In the UK, existing heating is predominantly by natural gas. The most significant challenge is the rural buildings that are not served by mains gas but have oil supplies, due to the high carbon content of this fuel. The Diocese of Gloucester was invited to participate in a research project carried out by Historic England into viable methods of low and zero carbon heating in churches and their associated buildings. The focus of this research explores oil-fired heating systems as this fuel produces more carbon dioxide emissions than other fuels used to heat buildings. The key finding from this research is that no single heating technology is recommended for either all historic buildings or even each historic building type. Across the six case studies, air source heat pumps, biomass and electric heating were recommended in an equal proportion of cases. It is not possible to determine the most viable heating technology without carrying out a detailed technical feasibility study at the early concept stage of a project. The recommended heating technology depends on many factors including the building’s site and location, the size and form of the buildings, the use and operation of the buildings, the condition of the existing heating system and the existing utility infrastructure. The wider background to this research includes the 2030 net zero carbon target set by the Church of England and the UK government’s 2050 net zero carbon target.

Анализ теплоэнергетических параметров тепличных комплексов

The analysis of existing heating systems for greenhouse complexes was carried out, their advantages and disadvantages were identified. Tasks have been set for the use of structures based on an energy-efficient surface-distributed method of heating (heating) using plate and volumetric multi-electrode composite electric heaters. A complex for determining the heat balance in the greenhouse has been carried out, inflows and outflows of heat have been identified. The possibility of using heat influx from a plate multi-electrode composite electric heater is presented, which makes it possible to normalize the microclimate in the greenhouse during the cold periods of the year. Keywords: TEMPERATURE HEAT SUPPLY, HEATING, GREENHOUSE, ENERGY BALANCE, HEAT BALANCE, HEAT TRANSFER, ENERGY SAVING

MAIN ERRORS DURING THE REPAIR OF EXISTING CENTRALIZED HEATING SYSTEMS OF THE HOUSING FUND

The article examines the main mistakes in the repair, which is not carried out centrally, but at the expense of the owner of the apartment, of the existing heating systems of the housing stock of buildings from the middle to the end of the twentieth century. The heating systems in these residential buildings are central, single-pipe (with upper or lower wiring), not adjustable, made of steel pipelines, either cast-iron radiators or steel "Accord" ("Comfort") convectors are installed as heating devices. Connection schemes of heating systems to heat networks are dependent. A decrease in the temperature of the heat carrier for the heating system of the residential part is provided with the help of an elevator unit. These systems have no regulation, neither local nor individual. These heating systems have both physical and moral wear and tear. Modern heating systems, which belong to the construction of the twenty-first century, are centralized or decentralized two-pipe heating systems, which are made of non-metallic pipelines, and bimetallic radiators or steel panel radiators are installed as heating devices. As a rule, these heating systems have both local and individual regulation. The article examines the difference between the concepts of repair and reconstruction; the consequences of changing steel pipelines to non-metallic ones; errors when choosing the type of pipes; replacement of existing heating devices with other types, with a different heat capacity; changes in the configuration of the heating system, additional installation of heating devices, creation of a heating system "Heat floor" in the apartment; reconstruction of one-pipe unregulated heating systems into one-pipe regulated ones with the installation of radiator valves and thermostatic elements. In addition, the concepts of heating, heat capacity, heat load, types of regulation of heat supply systems are considered. The main conclusion is that any work related to the reconstruction of the heating system of the apartment leads to an imbalance of the hydraulic and thermal regime of the indoor heating system of the residential building and must be carried out with the knowledge of the balance keeper of the residential building, in accordance with the technical conditions of the heat supply organization and on the basis project solutions.