On pulsing heating of the heat transfer medium in thermal delivery systems

The paper selects distributed solar water heating system of certain high-rise house in Jinan City as research object, its field performance test and energy efficiency assessment are made, obtains annual solar guarantee rate and conventional energy substitution quantity of solar water heating system of the building, makeseconomic benefit assessment, analyzes energy saving effect and economic benefit of the system, and gives out energy saving index and economic index. Research results show distributed solar water heating system of the high-rise building has good energy saving effect and economic benefit.

Combined air and water heating schemes have been actively used recently for heating public and residential premises. They have certain advantages in countries with a warm climate, whereas in a temperate climate, their use may be unfeasible. The most effective regulation of the heating system in the building can be expected, if all the technology specifics are taken into account, in terms of both the purpose of the room and the methods of regulation. A system focused only on weather-based regulation falls short of meeting to energy-efficient control classes: a heat carrier with the same temperature is distributed among rooms with different requirements for temperature and humidity characteristics. The issues of ensuring the energy efficiency of the combined air and water heating system in public buildings for the temperate continental climate of Russia — the academic building (AB) and laboratory building (LB) of the Kazan State Energy University (KSEU) have been considered. Heating devices of the KSEU heating system have manual control valves installed in the premises, or radiator valves with thermostatic heads, but without room controllers, which does not meet the energy-efficient control classes. An experimental survey of the functioning of the heating system of the KSEU buildings during the 2019 – 2020 and 2020 – 2021 heating seasons was conducted. The optical pyrometry method was used to measure the temperature of the surfaces of windows, walls and elements of the heating system, as well as the temperature and humidity of the air in lecture rooms and corridors of the AB and LB of the KSEU. The parameters of heating devices and indoor air in rooms of various purposes were found compliant with the current sanitary and hygienic requirements. At the same time, the need to switch to a higher class of regulation has been revealed, since, under the current situation, the parameters of the indoor air depend on the outdoor temperature: in the abnormally warm winter of 2020, the indoor air temperature was at the edge of the maximum permissible value, while in the normal climate of winter of 2021, it was at the edge of the minimum permissible value.

Hydronic heating and cooling systems are among the most common types of heating and cooling systems installed in older existing buildings, especially commercial buildings. According to the 2012 Commercial Building Energy Consumption Survey (CBECS) data set, hydronic heating systems in the United States include two main systems: (i) boilers inside the building represented with a boiler system and (ii) district steam and hot water systems represented with district heating, which are connected to seven different types of zone-level equipment. Similarly, there are two main hydronic cooling systems: central chillers inside (or adjacent to) the building and district chilled water piped in from outside the building. Chiller systems are investigated based on three different classes: (1) water-cooled, (2) air-cooled, and (3) absorption chillers. This study presents a deep analysis of the 2012 CBECS microdata to characterize hydronic heating and cooling systems by year of construction, census division, building area, building site hydronic system energy use index (EUI), and the types of mechanical systems. The results show that nearly 65% of commercial buildings built before 1990 utilize hydronic heating systems. Hydronic heating and cooling system design are a function of a building area. District heating systems are considered as the main heating systems in buildings with an area greater than 18,600 m2 (200,000 ft2). In addition, systems with central chillers inside the buildings are responsible for providing cooling for more than 50% of the commercial buildings with areas greater than 9,000 m2 (∼100,000 ft2). Among the types of chiller systems, the chiller systems connected to the central air handling units, fan coil units, and duct reheats are the most common systems for large buildings. The results of this building stock characterization provide useful insights into the characteristics of hydronic heating and cooling systems in US commercial buildings.

The district heating (DH) system is in its transition towards the 4th generation district heating (4GDH), and the high DH return temperatures need to be addressed during the process. In the existing building heating systems, many faults, malfunctions, or sub-optimal operations can lead to high DH return temperatures. However, the field of fault detection and diagnostics (FDD) within heating systems is notably under-researched in contrast to their counterparts in ventilation and air conditioning in building HVAC systems. This divergence can be attributed to several factors, including limited digital integration, a scarcity of data, and the non-obvious nature of faults in heating systems. In this study, we utilized heat cost allocators (HCA) and energy meters to investigate the features and potential impacts of four untraced faults that can lead to high district heating (DH) return temperatures in both space heating and domestic hot water systems in large buildings. We identified component-level faults, including heat exchanger overflow, space heating temperature controller failures, and excessive operating temperatures due to bypass, as well as system-level issues such as non-uniform heat distribution in buildings and its impacts. This exploration provides new, critical insights for advancing FDD research in HVAC and DH systems.

Objective . The aim of the study is to develop and implement software algorithms for engineering calculations designed for the automated determination of the parameters of mixing, water-jet and circulation pumps used in water heating systems of residential buildings. Method . The methodological foundation of the study is based on regulatory provisions in the fields of heating and heat supply, the heat balance equation, and the principles of hydraulic calculation for heating systems. The algorithms are implemented as three interrelated software modules, structured according to a block-logical scheme: input of initial data, thermal and hydraulic calculations, and output of parameters for pump selection. The calculations are performed with consideration of the steady-state thermal regime, outdoor and indoor air parameters, hydraulic losses in the system, and the design features of the pumping equipment. Result. Three specialized software programs have been developed for selecting the operating parameters of mixing, jet, and circulation pumps used in hydronic heating systems of residential buildings. The automated determination of input and calculated parameters is provided, including maximum thermal load, mass flow rate of the heat carrier, flow mixing ratio, hydraulic head, and geometric characteristics. The structure of each software module is presented, with justification of the input data, intermediate computational results in the form of listings, and output parameters. Conclusion. Algorithms simplify and accelerate the process of selecting pumping equipment operating parameters and minimize errors in engineering calculations. The software ensures that design solutions comply with regulatory requirements and takes into account external and internal climatic conditions and building performance characteristics. They also allow calculation algorithms to be adapted to heating supply conditions, including independent connections and closing sections of systems. Automated calculations facilitate the intensification of design work and are integrated into CAD and BIM technologies.

A mixed integer linear programming-based simple method for optimizing the design and operation of space heating and domestic hot water hybrid systems in residential buildings

Space cooling energy consumption is a significant component of building energy consumption, and in recent years it has attracted much attention worldwide owing to its significantly increasing usage. The variable refrigerant flow (VRF) system is one common type of cooling equipment for buildings in China and is applied extensively to residential and office buildings. The performance of VRF systems significantly influences the cooling energy consumption of buildings. The system energy efficiency and electricity consumption are the main indicators employed to evaluate the performance of VRF systems. It is hard to obtain the actual energy efficiency and electricity consumption of VRF systems in buildings because of the high cost of the required complicated measurements. This study proposes a virtual sensor modeling method to determine the actual energy efficiency and electricity consumption of 344 VRF systems in residential buildings. Statistical and clustering analyses are conducted to determine the energy efficiency and electricity consumption to obtain distributions and typical operation load patterns of VRF systems in residential buildings in China. The main findings are as follows: the main range of the Seasonal Energy Efficiency Ratio (SEER) for the cooling season is from 2.9 to 4.4; the median SEER in the Hot Summer and Cold Winter zone is lower than in another climate zones; the longer cooling duration may lead to greater electricity consumption, and the electricity load for VRF systems electricity load is periodic for each day. The oversizing issue is common for VRF systems in the dataset, which also led to the lower energy efficiency of VRF systems. The high usage of VRF systems appeared from July 27th to August 26th. The findings provide recommendations for designing VRF systems in residential buildings.

The article presents the analysis of the performance of a concentrating collector in the heating system of a residential building. Air was used as the working fluid. The heating requirements of the building were determined for each day of the year. The amount of direct irradiation reaching the absorber’s surface on all the days of the year was determined with the use of hourly meteorological data for Wroclaw, shared by the Ministry of Infrastructure and Growth. It was assumed that the collector is equipped with a tracking system working in one axis. Calculations and comparisons were made for the amount of solar irradiation for three values of the receiver’s inclination angle: β 1 =60°, β 2 =90° and β 3 =30°. Statistical method was used in order to determine the optimum inclination of the mirror and the amount of flowing air. This method involves creating a plan of experiment with three levels of changeability for two input factors. In the last stage, the amount of heat obtained from the installation during all the days of the year was analysed. The gains were juxtaposed on the diagram with the building’s heat demand. The analysis has shown that the heat requirements can be met only partially.

Theoretical investigation of the performance of a novel loop heat pipe solar water heating system for use in Beijing, China

Energy-related occupant behaviour is crucial to design and operation of energy and control systems in buildings. Occupant behaviours are often oversimplified as static schedules or settings in building performance simulation ignoring their stochastic nature. The continuous and dynamic interaction between occupants and building systems motivates their simultaneous simulation in an efficient manner. In the past, simultaneous simulation has relied on co-simulation approaches or customized source code changes to building simulation programmes. This paper presents Buildings. Occupants, an open-source package implemented in Modelica, for the simulation of occupant behaviours of lighting, windows, blinds, heating and air conditioning systems in office and residential buildings. Examples were presented to illustrate how the models in the Occupants package are capable to simulate stochastic occupant behaviours. The major contribution of this work is to introduce the equation-based modelling approach to simulate occupant behaviours in buildings and to develop an open-source Occupants package in the Modelica language.

In this paper an abstract model for adaptation of enterprise technologies in heterogeneous networks of small devices is proposed. The model is based on hierarchical multi- tier approach for better manageability and administration. Its structure allows not only separation between business and presentation logic, but also separation of enterprise and automation functions. Thus, changes in business and automation logics do not affect the user. The actual distribution of functions appears on the service and automation tiers. The level of abstraction of the model allows its usage in various environments - home and office automation, industry, medicine, agriculture. In the paper an experimental application of the presented model for an effective management of HVAC (heating, ventilation and air conditioning) systems in buildings is discussed. subsystems. The key goal of the work, presented in the paper, is the analysis of the latest off-the-shelf technologies in business information systems and their possible adaptation in distributed automation, based on controllers with embedded communication facilities. For this purpose, a model of information flow and representation in distributed automation systems is developed, employing the standards of e-business, working on the web. An experimental application of the presented model for an effective management of Heating, Ventilation, and Air-Conditioning (HVAC) systems in residential buildings is proposed. The limited resources of the embedded devices as well as the dynamic nature of building's automation networks are impending factors for the adaptation of web services into the systems. The rest of the paper is organized as follows:

Demand response potential of ventilation systems in residential buildings

Heating, ventilation, and air conditioning (HVAC) systems in buildings have great potential to provide regulation capacity that is leveraged to maintain the balance of supply and demand in the power system. In order to make full use of HVAC’s regulation capacity, it is important to accurately evaluate it ahead of time. Because physical model-based approaches are hard to implement and highly personalized for each building, data-driven approaches are preferable for this capacity evaluation. However, given the insufficient data for individual buildings and buildings’ potential unwillingness to share their data because of privacy concerns, it is extremely challenging to build a high-performance data-driven regulation capacity evaluation model. In this paper, we propose a privacy-preserving framework that combines federated learning and transfer learning to evaluate the regulation capacity of HVAC systems in heterogeneous buildings. Specifically, a classified federated learning algorithm is proposed to build capacity evaluation models of HVAC systems for different building types. Each building trains its model locally without sharing data with other buildings to preserve privacy. The algorithm also tackles data insufficiency and achieves high evaluation accuracy. In addition, we design a cross-type transfer learning algorithm to enhance model generalization and further address data deficiency. A protocol is created for the above two algorithms to protect privacy and security. Finally, numerical case studies are conducted to validate the proposed framework.

The main users of district heating (DH) systems are multi-apartment buildings – 53% of these buildings in Lithuania are supplied with heat from DH systems. Heating systems in buildings are the largest final consumer of energy, accounting for almost half of total energy consumption in many European countries. One of the measures planned for the Lithuanian energy policy in the heat sector of renewable energy sources (RES) until 2030 is the installation of heat pumps (HP) in the DH networks. The purpose of the study is to evaluate the technological possibilities of integrating HP into existing buildings to evaluate the low temperature heat supply. To evaluate the potential temperature lowering of the building heating system, a graph of the lowest possible building heating system temperatures is set, according to which the heat pump for the heating substation is selected, which would raise the temperature of the heat carrier supplied from DH networks to the required temperature for the heating and hot water systems of the building. Applying thermodynamic analysis, a mathematical model is developed that evaluates the ability of the HP to raise the temperature of the supplied heat carrier at the heat substation and determines the energy efficiency of such a solution. During the simulation, two alternatives of constant (regardless of outdoor air temperature) heat carrier temperatures supplied from DH networks were considered: 60 °C (alternative A) and 55 °C (alternative B). To adapt the most appropriate option for the integration of HP, it would be appropriate to combine both alternatives, i. y. to supply 60 °C from the DH network in the cold period of the year and 55 °C in the warm period of the year.

Modern energy systems worldwide are facing the imperative of transitioning to sustainable energy supply models that do not contribute to the accumulation of carbon in the atmosphere or exacerbate the greenhouse effect, a factor now widely recognized as a key driver of global climate change. To ensure universal access to energy resources, improve environmental quality, and meet the growing energy demands of humanity, a comprehensive transformation of all elements of energy infrastructure is required. This transition does not have a singular or simple solution and demands a multidimensional approach. Reducing greenhouse gas emissions can be achieved through the integration of various energy sources and technological solutions that ensure high levels of efficiency and economic viability. The renewable energy sources and improvements in energy efficiency play a leading role in achieving climate neutrality. The reliable methods for comprehensive implementation, ensuring sustainable heat energy supply in buildings while providing comfortable conditions during the winter season is of key importance. Energy-efficient modernization of heating systems in buildings, with an increased share of renewable energy sources for heat production, is of paramount importance for the reconstruction of Ukraine. The paper proposes an approach, based on a heating system model that evaluates the impact of each innovation through the integration of energy, environmental, and economic performance indicators. The mathematical model of the building heat consumption estimation based on energy audit, which determines the initial building condition is presented. Every possible renovation action, including the change of the heating source is evaluated, and energy, environmental, and economic performance indicators are defined, enabling to find the optimal solution based on the multi-objective optimisation. The proposed approach serves as a valuable tool for preliminary engineering calculations during the design phase. The application of this model is demonstrated through a case study of an administrative building in Kharkiv. The evaluation of building thermal modernization and the installation of a heat pump was carried out based on environmental and economic performance indicators. The implementation of the recommended modernization measures in 2020, coupled with the analysis of measurements at the actual site, revealed a discrepancy of 15% between the predicted and measured heat consumption values. This finding supports the recommendation of the proposed method for enhancing heating systems in buildings.