Building Heating Systems Research Articles

Economic Model Predictive Control in Buildings Based on Piecewise Linear Approximation of Predicted Mean Vote Index

Energy shortage is a challenge for many countries, and building energy consumption accounts for a considerable proportion of global energy consumption. The main work of this paper is to optimize the energy consumption of heating, ventilating, and air conditioning (HVAC) systems in buildings based on economic model predictive control (EMPC). The cost in EMPC design includes energy consumption and predicted mean vote (PMV), which is an index that evaluates the thermal comfort of indoor occupants. In order to model the nonlinearity of the PMV index, we propose a lattice piecewise linear (PWL) approximation, which has high approximation precision and facilitates the resulting optimization problem, which is basically a piecewise quadratic programming problem. For the piecewise quadratic programming, we propose a descent algorithm that converges quickly and scales well with the length of the prediction horizon in the EMPC problem. The experimental results demonstrate that the proposed method saves 19.78% of the electricity cost compared to the conventional control strategy and significantly increases indoor comfort. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> — The motivation of this article is to provide a control strategy to reduce building energy consumption and ensure indoor thermal comfort. In most of the existing methods for air conditioning temperature control, the occupants’ comfort hasn’t been considered. In this paper, thermal comfort is described by the PMV index, which is basically nonlinear. In order to model the thermal comfort more accurately, in this paper, the PMV index is approximated piecewise linearly in order to meet the requirements of accuracy and computational efficiency. The resulting optimization problem is not hard to solve, and we provide an efficient algorithm for solving this optimization problem. Preliminary simulation experiments demonstrate that this approach is practical, i.e., it achieves energy reduction and ensures thermal comfort. Our strategy, however, has not yet been deployed in real buildings. In future research, we will propose similar techniques for large-scale systems in order to solve energy optimization problems containing multiple thermal zones and realize the proposed technique in real buildings.

EVALUATION OF THE ENERGY EFFICIENCY OF HEAT SUPPLY SYSTEMS OF A RESIDENTIAL BUILDING WITH HEAT PUMPS BASED ON COMPUTER SIMULATION

This article presents an analysis of the energy efficiency of the heating system of a single-family residential building with the integration of a heat pump (HP) using climate data for Kyiv city. Specialized software complexes for calculation (GeoT*SOL), dynamic energy modeling (DesignBuilder/EnergyPlus), and techno-economic justification of HP systems implementation (RETScreen) were used for this purpose. The analysis was conducted for two types of HPs: air-to-water (air-based) and ground-source (ground-based), considering various temperature regimes of the indoor heating system. Based on the modeling results, it was determined that for an air-to-water HP with a nominal capacity of 7 kW, the average seasonal efficiency rating could be approximately 3.6 for the HP itself and 2.7 for the overall system. For a ground-source HP with a nominal capacity of 6 kW, the average seasonal efficiency rating is 4.7 for the HP itself and 3.75 for the overall system. The total electricity consumption varies within the range of 4800–5700 kWh for air-based HP and 3200–4300 kWh for ground-based HP. Depending on the HP capacity, the share of heating energy coverage ranges from 85-98% for ground-based HP and 79-98% for air-based HP. The simple payback period of the HP-based heating system compared to electric convectors is 15.2–17.0 years.

Analysis of the Physical Phenomena and Modelling Procedures of Building Heating and Cooling Emission System Energy Losses

An important research issue in assessing the energy performance of buildings concerns the modelling of the interaction between the built environment and the heating/cooling emission systems. Several methods can be used to evaluate the effect of the heating emitter characteristics, including the possible embedment in the building structure, non-uniform space temperature distribution, and the accuracy of the indoor temperature control. Generally, technical standards specify simplified, yet insufficiently validated methods, based on tabulated values. This paper outlines the main simplified procedures for assessing the efficiency of the emission subsystem, with a particular focus on the hydronic systems. It describes the essential datasets required for the analysis and highlights the interaction with phenomena related to the emitter heat loss. The simplified calculation procedures are then methodologically compared with detailed simulation tools, such as EnergyPlus, to identify differences and limitations in the models. The main discrepancies in the procedures and the required input data are highlighted, and possible strategies for improving the simplified methods are presented. A building representative of the European residential building stock is then analysed in the Italian climate using different calculation procedures. The results, in terms of thermal output of the emitter, are then analysed and compared.

Optimisation of solar thermal photovoltaic heating systems for buildings considering stability

Optimisation of solar thermal photovoltaic heating systems for buildings considering stability

Analysis of thermal characteristics of building envelope structure for night storage heating

In order to understand the thermal characteristics analysis of nighttime thermal storage heating, the author proposes a study on the thermal characteristics analysis of nighttime thermal storage heating of building envelope structures. In some places, the writer will use an office room as a research object. The main purpose of the experiment is to measure, compare and analyze the surface temperature and heat flow rate of the room sample volume under two conditions: constant power 24 hour heating and night constant thermal power (12 hours) heating. In order to verify the accuracy of the dynamic thermal process of the heating room, the indoor air time variation will be performed along with the simulation results. Thermal performance parameters and characteristics of building thermal envelope heating effect of storage room were studied. The mathematical model of the thermal dynamic process of the heating room was established using the heat balance method and verified by experiments. According to the experiment, when the heating time increases from 5-12 hours, the additional heating consumption of the building heating system decreases by 500 Wh, and the additional heating consumption decreases to 19.4. In addition, it is important to change the heating time of the night-time packing model and the total heat accumulation. In addition, external wall insulation is useful in reducing additional heating consumption and building heating costs, but all heat transfer between model blocks is low. As the weather changes and the heat transfer coefficient of the external window increases, the additional amount of heat consumption and the additional value of heat consumption for heat storage of the building will increase. In the process of continuous heating operation, the additional heat consumption of the building heating system, the additional heat consumption gradually decreases, the heating equipment changes per hour, and the total heat accumulation of the night packing structure is important.

Feasibility of carbon-capturing in building heating systems: A life cycle thinking-based approach

Buildings are responsible for 40 % of the global energy consumption, thus leading to significant climate change and other environmental impacts. Adopting carbon capturing, storage, and utilization technologies (CCSU) can be a solution for reducing greenhouse gas (GHG) emissions from natural gas building heating systems. However, the current knowledge base lacks definitive knowledge on the possibilities and impacts of building level CCSU. The goal of this study is to investigate the feasibility of implementing CCSU technologies in natural gas building heating systems. A comparative performance assessment framework was developed to evaluate the environmental and economic performance of building-level CCSU technologies over their life cycle. These performances were then compared against alternative GHG emissions mitigation methods used for building heating systems. The results obtained by a case study indicated that adopting CCSU technologies in residential buildings is not economically and environmentally competitive against electricity-based heating systems when the regional electricity is generated using renewable energy sources and nuclear energy. However, there is a potential for the building-level CCSU in regions that depend on fossil fuels to generate electricity. The research outcomes will further develop and improve building-level carbon capturing technologies and will provide confidence to stakeholders to invest.

Влияние заполнения прослоек малотеплопроводными газами на тепловую защиту оконных блоков с экранами

ISPU scientists have developed energy-saving constructions of window units with heat-reflecting screens, have tested them in a climate chamber, and have carried out simulation modeling of the heat transfer process through these constructions. Despite a large number of scientific papers that consider experimental laboratory studies and numerical simulation of heat transfer processes through translucent constructions, there is no data on the effect of the application of low thermal conductivity gases in the gaps formed by glass and metal elements on increasing the thermal protection of window units with screens. The correct calculation of the reduced heat transfer resistance of window units with screens and low-thermal conductivity gases affects the correctness of the heat balance for premises and, consequently, the quality of the design of energy systems to ensure the indoor microclimate. Thus, the development of models of heat transfer process through a window unit with screens is an urgent task to ensure the indoor microclimate. Simulation numerical modeling is carried out using the finite element method based on the fundamental laws of heat transfer. The authors have developed a two-dimensional simulation model of heat transfer through a window unit with heat-reflecting screens, in which the gaps between the glass and aluminum foil are filled with argon and krypton. The distribution of resistance to heat transfer along the height of a translucent enclosing structure has been studied. The adequacy of the proposed simulation model is confirmed by comparison with data of other scientists and regulatory documentation. Filling the gaps between glass and metal foil with argon makes it possible to increase the zonal heat transfer resistance of a window unit with screens in relation to the base-case scenario (air) by 6–23 %, krypton by 8–58 % (depending on the measurement location and the number of screens). The application of the developed simulation model will make it possible to more accurately determine the potential to use heat-reflecting screens in windows for intermittent heating systems of buildings.

Performance boost of a commercial air-to-air plate heat recovery unit by mesh-net insert; thermal-frictional, economic, and effectiveness-NTU analysis

This research proposes, tests, and comprehensively investigates the application of mesh-net to increase the efficiency of any air-to-air plate heat exchanger (mainly as a building heat recovery unit). The idea is tested through a commercial heat-recovery unit and all parameters including Nusselt number, pressure drop, friction factor, thermal performance factor, effectiveness, number of thermal units, pumping power and economical profitability are comprehensively investigated and reported with and without mesh-net insert. In economic evaluation the price of electricity and type of building heating system (resistance heater, heat pump and so on) are considered. In the maximum air flow rates, the overall heat transfer coefficient is enhanced from 24 to 36 W/m2K. Nusselt number increases up to 75 % depending on air flow rate. The economic results were found very interesting, and even by paying further fan power due to the higher pressure drop, the economic profitability is positive when the building heating system is resistance heater or heat pump with lower coefficient of performance. The profitability of the mesh net insert is higher for the region with higher electricity price. This means the gained recovered heat overcomes the further energy required for pumping power. Nonetheless, final decision making from pure economic viewpoint depends on the desired supply air flow rate, type of heating system and local price of electricity.

BUILDING HEAT SUPPLY SYSTEM BASED ON HYBRID SOLAR COLLECTORS

Increasing the efficiency of solar heat supply systems is one of the important problems of solar energy. The research presented in this article is aimed at improving the efficiency of hybrid solar collectors without a transparent coating for building heating systems. One of the key challenges in the field of solar energy is the development of new technologies to ensure high collection of solar energy and to integrate it into traditional heating and hot water systems. The study shows that hybrid solar collectors with the placement of heat carrier circulation circuit tubes above the heat absorber can increase the thermal efficiency factor with a certain change in the angle of inclination and the density of solar radiation. A nomogram was also developed that determines the dependence of this coefficient on the angles of arrival of solar radiation and its density.

Automation of air heating systems of buildings

Automation of air heating systems of buildings

A hybrid control strategy for frequency regulation with variable refrigerant flow air conditioning system

Heating, ventilation and air conditioning (HVAC) systems of buildings are abundant sources for the Frequency Regulation (FR) ancillary service, whose actuating devices are controlled to follow the real-time power reference signals with the contractual capacity. For HVAC practice, model-based FR controls are hindered by expensive model acquisition. This paper presents a two-layer control strategy for HVAC systems to perform energy efficient FR service, with a rather low model requirement. At the lower level, the FR operation with a selected actuator is realized with a sliding mode control which is robust to power map variation. At the higher level, system efficiency is optimized in real time via a model-free constrained extremum seeking control (CESC). A conceptual variable refrigerant flow (VRF) system is used as the illustrative application, for which the outdoor unit fan offers the FR power reference tracking with SMC. At the outer loop, the compressor discharge pressure is adjusted by a CESC to minimize the total power consumption while the zonal temperature regulation is reinforced as equality constraint. The proposed strategy is evaluated with simulations on a Modelica simulation, and the results validate its effectiveness. The Net Energy Cost can reduce by 15% to 23% under different load levels.

TECHNICAL AND ECONOMIC ANALYSIS OF THE SYSTEM LONG-WAVE INFRARED HEATING IN DIFFERENT TYPES OF BUILDINGS

The paper presents the calculation of energy costs for heating buildings with three different heating systems, in order to determine the feasibility of using long-wave radiant heaters. The current rules of energy certification of buildings and related state standards of Ukraine were used as the calculation method. A technical and economic analysis was carried out, thanks to which savings from the transition to a radiant heating system in residential, public and industrial buildings located in the same weather environment were determined. The feasibility of radiant heating systems beyond the usual scope of use, namely in residential buildings, which make up the majority of all heating structures in Ukraine, and small architectural forms, such as, for example, modular buildings of retail establishments, public catering, etc., has been studied and provided. Bilux electric infrared long-wave heaters were chosen as the main research system. Competing systems are a water two-pipe system with free-flowing radiators and electric wall convectors. The key difference between traditional water heating systems, from the point of view of calculating energy consumption, is determined, which is the absence of losses in pipelines. It is justified that radiant heating systems are more appropriate in buildings with a floor height of more than 4 meters. It has been proven that in buildings of smaller volume, the cost reduction is also quite significant.

Techno-economic feasibility assessment of a photovoltaic water heating storage system for self-consumption improvement purposes

Photovoltaic excess energy export to the grid starts to be a common issue among residential grid-tied PV systems. Its impact is more significant when the feed-in tariffs are not available (Moroccan case) or if they are far from competition. Load shifting, batteries and thermal energy storage all have the potential to diminish the excess energy sent to the grid. However, the water heating strategy has received little literature attention so far. In this study, we seek to assess the techno-economic feasibility of using the PV excess energy in a hot water storage tank by means of a diverter as the main water heating system for a bioclimatic building. The excess energy of a 2kWp grid-tied PV system has been monitored for one year with a 1-min time resolution. The data is used within a TRNSYS numerical simulation for the city of Marrakesh, Morocco. In comparison to an ordinary solar thermal water heating (STWH) system, the results of the simulation revealed that both systems maintain the setpoint temperature using practically the same amount of auxiliary energy. Additionally, a 52.23 % relative improvement to the self-consumption rate has been obtained by integrating a PV water heater (PVWH). The Levelized Cost of Energy found to be 33 % lower for the PVWH compared to that of the STWH solution, evaluated at 0.06 and 0.09 $/kWh respectively. In addition, PVWH's Payback Time period was four years, while that of the STWH was six years. Ultimately, the Net Present Value was significantly higher for the PVWH (1840.28 $) than for the STWH (1008.8 $).

Calibrating subjective data biases and model predictive uncertainties in machine learning-based thermal perception predictions

Heating, Ventilation, and Air Conditioning (HVAC) systems in large-scale buildings often struggle to ensure satisfactory thermal comfort for diverse occupants while minimizing energy waste. Achieving this goal requires developing reliable prediction models that capture the changing and varied occupant thermal perceptions in different spaces. Despite their widespread use, many machine learning (ML) based prediction models suffer from subjective data biases and model predictive uncertainties, causing inaccurate estimation for occupant needs and leading to suboptimal building controls. The authors propose a data-model integration method that identifies and calibrates the inherent uncertainties of existing ML models in both data and model dimensions, ensuring reliable thermal perception predictions. This method introduces the Multidimensional Association Rule Mining (M-ARM) algorithm to identify biased human responses by exploring interrelationships among four perception metrics: thermal sensation, comfort, acceptability, and preference. Our method reveals significant performance enhancements in seven ML models, enhancing the F1-score by up to 5.53%. By leveraging reliability diagrams and Expected Calibration Error (ECE) scores, we also expose the models’ vulnerability to miscalibration and the need for calibrated predictions. We further evaluate six calibration techniques (e.g., Platt Scaling and Isotonic Calibration) on these models and uncover their potential to enhance prediction reliability performance, highlighting a reduction of up to 80.66% in ECE scores. The authors also investigated the impacts of dataset sizes, classifiers, and calibration methods on the proposed method. Our research offers insight into creating robust data-driven strategies for thermal perception predictions, ultimately contributing to optimized occupant comfort and energy efficiency in buildings.

Досвід застосовування теплових акумуляторів в умовах блекауту

This study is the first and so far the only one in Ukraine dedicated to the experience of using mobile thermal energy storage in emergencies, in particular blackouts. The article considers the issue of ensuring energy security. The classification of heat storage system parameters is given. The considered model of an autonomous heating system with a heat storage system. The impact on the thermal energy storage heating system with different designs of heat generators and fuel types is shown. The results of the operation of a combined system consisting of an autonomous heating system of a separate building equipped with an electric boiler and thermal energy storage are presented. Thermal energy storage is used not only as a buffer between the heat generator and the heating system but also as a source of heat. Integrating the thermal energy storage into the building's heating system ensures constant heat supply to the building, 100% coverage of peak dynamic loads, halving the boiler unit capacity and operating costs by 20%. It has been proven that the presence of thermal energy storage allows solving the problem of providing a stable heat supply in the conditions of a power outage. A detailed description of the conducted study of methods and equipment used during field operation and data processing is given. The results of the field tests of the thermal energy storage in winter operation conditions are provided. Features of the use of the controller for monitoring the heating system's operation with thermal energy storage are provided. The results of field tests are given. An analysis of the received data was carried out. Formulated directions for further scientific research, development, and practical recommendations for the use of mobile heat accumulators in the national economy and the state emergency service of Ukraine. Economic criteria and efficiency criteria aimed at reducing operational costs are considered. The obtained research results can be used to predict the operation of heating and cooling systems equipped with thermal energy storage. Keywords: Heating system, security, blackout, thermal energy storage, monitoring.

Synthesis of model predictive control based on neural network for energy consumption enhancement in building

The problem addressed in this work is the enhancement of energy efficiency in buildings, primarily focused on heating control. The paper highlights the importance of addressing this challenge, given that HVAC systems are responsible for over 60% of total energy consumption in buildings, making them the largest energy consumers in both the residential and nonresidential sectors. This paper presents a methodology for developing a model predictive control (MPC) system based on artificial neural network (ANN) models, with the aim of improving the energy efficiency of buildings. This approach involves the creation of a training dataset using dynamic thermal simulation tools, enabling the learning of the ANN model that is responsible for predicting future states within an MPC optimization loop. Additionally, the implementation leverages advanced technologies such as Field-Programmable Gate Arrays (FPGAs), specifically the PYNQ board, Wi-Fi modules, and MQTT communication to enhance scalability, deployment, and adaptability. The study evaluates the proposed Neural Network Model Predictive Control (NNMPC) strategy implemented on the PYNQ, reporting a substantial reduction of 38.53% in heating energy consumption in buildings compared to a basic On/Off control approach for 24-hour simulation. This outcome underscores the solutions significant potential for energy savings in building heating systems.

The impact of heating systems scenarios on air pollution at selected residential zone: a case study using AERMOD dispersion model

The present case study considers fuel base substitution in operation of actual district heating system and in other scenario replacing of district heating system by individual heating system in each apartment building and non-residential building in selected residential zone Zvolen-Sekier, Slovakia. The impact of each heating system was assessed with focus on ambient air quality based on air dispersion modelling of NO2 and CO pollutans using the AERMOD dispersion model. To identify the exposure level on residents, the magnitude and duration of exposure to the hazard were considered according to human health risk assessment method. Results showed that the individual heating systems released significantly higher NO2 and CO concentrations directly in the residential zone compared to district heating system. The obtained results were highly variable for individual scenarios and averaged periods of pollutants concentration. Investigated heating systems scenarios showed low (< 1.0) hazard quotient value, however, individual heating systems would lead to adverse health effects, especially in infants and children population.

PCM embedded square channel receiver for effective operation of Net Zero Emission/Energy PDC building heating system

Net Zero Emission / Energy recommends reducing energy consumption to zero (use of renewable sources) and ensuring no pollution and emissions. Parabolic Dish Collector (PDC) is such a device, which utilizes the Solar energy (Zero Cost of Energy) for heating (Zero Emission of Carbon gases) by converting solar energy into heat transfer fluids (HTF). The recent researches PDC receiver’s efficiency improvement by different designs or arrangement inside the receiver as well as different types of phase change materials (PCMs) incorporated to it. This investigation aims to improve the PDC by involving the square channel type solar receiver as an alternate receiver and embedding it with the PCM for building heating applications. The thermal performance of 14 m2 square-channeled PDC was investigated with and without PCM embedded conditions. For embedding PCM of Paraffin wax, 3 kg was used in thermal storage in this experiment. The square-channeled receiver recorded the lowest receiver surface temperature and the highest discharge water temperature. Black coating is employed to reduce the heat loss from the receiver substance.The average energy and exergy efficiencies are around 65.8 % and 6.8 %, respectively, at a flow velocity of 0.07 kg/s. As PCM maintains a constant temperature, the solar receiver can hold its internal temperature around triple times higher than the conventional PDC (without PCM case). Hence it was experimentally ensured that PCM-filled PDC (solar receivers) is suitable for heating applications in domestic and industrial buildings.

Research on renewable energy coupling system based on medium-deep ground temperature attenuation

Medium-deep geothermal has large reserves, a high temperature, a high heat flow density, and other characteristics, but the traditional medium-deep ground heat pump system have long relied on heating from the ground, and soil temperature decreases annually. Using a community building heating system as an example, from a point of view of heat accumulation or not, this article examines the design of a photovoltaic photothermal coupled medium-deep ground source heat pump system (PV/T-GSHP) and a photovoltaic-assisted medium-deep ground source heat pump coupled air source heat pump system (PVGSHP-ASHP). First, the operational performance of a typical GSHP system was compared to that of the PV/T-GSHP and PVGSHP-ASHP systems, both of which were built using TRNSYS. Second, the energy balance and electrical consumption of each system were compared. Finally, the effect of the PV/T-GSHP system’s key parameters and the different ASHP load ratios in the PVGSHP-ASHP system on soil temperature were analyzed. The results showed that after 20 years of operation, the average soil temperature decreased from 38.29 °C to 36.89 °C for the GSHP system, resulting in a decrease in the performance coefficient of the ground source heat pump and the system performance coefficient. The PV/T-GSHP system can address the issue of declining soil temperature with an increase in soil temperature of 0.09 °C. The PVGSHP-ASHP system can mitigate the issue of decreasing soil temperature. The PVGSHP-ASHP system is better than the PV/T-GSHP system in terms of electricity economy. In the PV/T-GSHP system, the larger PV/T component area of similar structures, the smaller flow rate of the heat collector pump, and the volume, inclination, and set temperature of the heat storage tank that are more suitable for the system can achieve higher soil temperatures. As the air-source load ratio increases, the rate at which the soil temperature in the PVGSHP-ASHP system decreases progressively decelerates.

Design errors during major repairs of apartment buildings

The main design errors during the overhaul of the heating system of apartment buildings on the example of a 5-storey building made of expanded clay concrete panels are considered and analyzed. A comparative analysis of the values of the heat transfer resistance of external walls obtained by calculation and based on the results of experimental data is performed. Based on the obtained values of the heat transfer resistance of the exterior walls, the calculation of the heat losses of the building was performed. As a result of the identified shortcomings, the amount of thermal energy that the residents of the surveyed house located on the territory of the city of Samara did not receive was calculated.