Centralized Heat Supply Research Articles

OPTIMIZING FACTORS OF THE TEMPERATURE SCHEDULE OF HEAT RELEASE IN MUNICIPAL THERMAL ENERGY SYSTEMS. PART 1. MINIMIZATION OF HEAT LOSS WITH BOILER WASTE GASES

The reason for the ambiguous assessment of high-temperature modes of heat release is the influence of the heat carrier temperature in the return pipeline on the work efficiency and thermodynamic efficiency of heat sources in centralized heat supply systems (CSTs). Non-productive heat losses due to heat losses with waste gases.The purpose of the research is to substantiate the feasibility of implementing the utilization of the heat of combustion products in a condensing heat exchanger-utilizer.The results of the calculations confirm that a significant reduction in heat loss with waste gases and a corresponding increase in the efficiency of the unit can be achieved if the temperature of the waste gases after the heat exchanger is reduced below the dew point. Without the introduction of condensing boilers or condensing heat exchangers-utilizers and without changing the method of regulation, the transition to a low-temperature heat release schedule will only lead to a deterioration of the overall efficiency of the heat supply system.

OPTIMIZING FACTORS OF THE TEMPERATURE SCHEDULE OF HEAT RELEASE IN MUNICIPAL THERMAL ENERGY SYSTEMS

The need to maintain a high temperature of the coolant for hot water supply during the transition period of the year leads to large heat losses, and this is a significant drawback of high-quality central regulation of heat release. The purpose of the study is to substantiate the effectiveness of the transition to a combined quantitative and qualitative method of regulating heat release. The paper proposes the implementation of a combined quantitative and qualitative regulation, in which the release of heat is regulated by changing the temperature of the heat carrier before the cut-off temperature of the temperature graph, and after the cut-off, the transition to quantitative central regulation is carried out. The work shows that the need for such regulation is an organic need for centralized heat supply systems (СНSs) in connection with the thermal modernization of buildings and their equipment with automated IНPs. The low-temperature schedule of heat release, provided that the CНSs boilers are equipped with condensation heat exchangers, makes it possible to significantly increase the efficiency of heat generators and СНSs as a whole.

Efficiency of mine water use in the centralized heat supply system of city district

Technological solutions for the use of mine waters energy potential in district heating system of settlements in the coal-mining regions using heat pumps have been substantiated. Using the example of mines in the Central Donbas, an analysis of composition and quantity of mine waters has been carried out, an assessment of the energy potential of mine waters and an assessment of the sufficiency of such a potential to meet the needs of buildings of cities for heating and hot water supply have been carried out. A schematic diagram has been developed for the implementation of a project for the use of mine water in district heating systems in cities while maintaining the function of existing boiler heating systems as peak sources of heat. Thermodynamic calculations of the heat pump cycle in real conditions of using mine water have been carried out. A quantitative assessment of the main technical, economic and environmental indices of the project is presented. The selection of equipment has been carried out and the efficiency assessment of its work has been made. It is recommended to use heat pumps using the thermal potential of mine water in district heating systems for both operating and closed mines.

LPV Time-Delay System Identification and Its Application to the Centralized Heat-Supply System

In winter, the centralized heat-supply system (CHSS) is an important and indispensable heating equipment in the northeast of China. Hence, in this article, the introduction to the CHSS is first presented, especially for the thermal dynamics of the secondary pipe network (SPN) of the CHSS, and then the identification of the thermal dynamics of the SPN under constant flow is studied. To this end, the linear parameter varying (LPV) model with autoregressive exogenous (ARX) structure is chosen as the system model and the problems of outliers and unknown system delay are both synthesized in the identification process. The physical meanings of all the variables in the LPV model are introduced in detail. By using the expectation-maximization (EM) algorithm, the equations to estimate all the parameters are derived and the desired parameter estimates can be obtained in the context. Finally, the verification tests as well as the corresponding discussions are presented.

RENEWABLE ENERGY INTEGRATION FOR HOT WATER SUPPLY AND HEATING OF BUILDINGS

Solar energy is widely used in solar systems, where economy and ecology are combined. Namely, this represents an important moment in the era of depletion of energy resources. The use of solar energy is a promising economical item for all countries of the world, meeting their interests also in terms of energy independence, thanks to which it is confidently gaining a stable position in the global energy sector. The cost of heat obtained through the use of solar installations largely depends on the radiation and climatic conditions of the area where the solar installation is used. The climatic conditions of our country, especially the south, make it possible to use the energy of the Sun to cover a significant part of the need for heat. A decrease in the reserves of fossil fuel and its rise in price have led to the development of optimal technical solutions, efficiency and economic feasibility of using solar installations. And today this is no longer an idle curiosity, but a conscious desire of homeowners to save not only their financial budget, but also health, which is possible only with the use of alternative energy sources, such as: double-circuit solar installations, geothermal heat pumps (HP), wind power generators. The problem is especially acute in the heat supply of housing and communal services (HCS), where the cost of fuel for heat production is several times higher than the cost of electricity. The main disadvantages of centralized heat supply sources are low energy, economic and environmental efficiency. And high transport tariffs for the delivery of energy carriers and frequent accidents on heating mains exacerbate the negative factors inherent in traditional district heating. One of the most effective energy-saving methods that make it possible to save fossil fuel, reduce environmental pollution, and meet the needs of consumers in process heat is the use of heat pump technologies for heat production.

Analysis of the issue of the selection, operation and improvement of thermal insulation materials for pipelines of heating networks

Improving the energy efficiency of thermal energy generation, transportation and consumption systems is one of the priority tasks of the modern development of the fuel and energy complex of Russia. The climatic conditions of Russia determine the heat supply systems as an energy-intensive industry that consumes up to 40% of the primary energy resources of country. Russia is characterized by a high level of centralized heat supply, mainly from sources of combined generation of heat and electric energy, which led to the creation of an extensive pipeline system with a length of more than 250 thousand km with a diameter of 57 to 1400 mm. In practice, the following methods of laying pipelines are used: canal, canal-free, aboveground. The heat losses of pipelines of thermal networks amount to 324 million gcal/year, which is approximately 16% of the heat released to consumers, this indicates significant reserves of saving thermal energy. The successful solution of the problem of reducing heat losses during the transportation of the heat transfer agent can be achieved by using modern materials and developing highly efficient porous thermal insulation structures, as well as improving the methods of calculating heat networks and the optimal choice of thermal insulation materials for the required operating conditions.

Analysis of heat losses during heat supply of an urban-type settlement using a heat pump

Centralized heat supply systems include a network of pipelines connecting buildings and structures in such a way that entire districts and quarters are supplied with a heat carrier from a single boiler plant. District heating is a well-studied part of the energy system. Despite this, low temperature district heating is still underdeveloped, although it is one of the key technologies for energy efficient urban heating. Low-temperature heat supply systems are the basis of 4th generation district heating systems, since they can significantly reduce heat losses during transportation of the heat carrier to the heat energy consumer and allow the use of heat from renewable sources, for example, heat pumps. The study focuses on analyzing the heat loss of a district heating system by comparing simulation results at a standard flow temperature and at a temperature typical of the 4th generation heat supply schedule. On the basis of the created model, the calculation of heat and hydraulic losses of the low-temperature district heating system was carried out, as well as a comparative analysis in comparison with the standard heat supply system.

Hybrid Carbon Dioxide Heat Pump for the Multifamily Residential Buildings in the Heat Supply System Based on CHP

The work is devoted to centralized heat supply systems based on CHP plants and the use with them heat pumps (HP) on carbon dioxide as refrigerant. Heat pumps are used in heat supply systems for buildings and use the heat of the outside air and, at the same time, the heat of the return network water (WWR) as a source of low-grade heat (LHP). The aim of the study is to develop a structural diagram of such a heat pump, where the outside air is heated by a heat exchanger installed in the return water line of the heating system, to develop a hydraulic circuit of a heat pump taking into account the law of regulation of the building heating system, to develop an algorithm for controlling the operating modes of the so-called balancing heat exchanger installed after gas cooler and internal heat exchanger of the heat pump. The most significant results were the hydraulic circuit of the heat pump, the aerodynamic circuit of the air supply path to the heat pump evaporator, the balancing heat exchanger control system, taking into account the requirement to ensure the operation of the control valve in a single-phase flow. The significance of the results obtained consisted in obtaining the dependences between the CO temperature graph and the parameters of the thermodynamic cycle of the heat pump, which ensured the operation of the control valve of the heat pump in a single-phase environment.

Heat Transfer Research in Blown-Through Non-Passable Heating Mains Channels. Part 2

A schematic and structural solution of regenerative-utilization heat use in centralized heat supply systems was previously proposed in order to increase the efficiency of operation of heating networks located in non-passable channels. The impossibility of creating a full-scale experimental setup covering the required range of factors and the area of their change, the complexity of a passive experiment on existing heating mains led to the need to develop a virtual model based on the ANSYS sofware package. A six-factor experiment has been carried out on this virtual model. Regression equations have been obtained to determine the pressure required to provide air purging of the channel, as well as heat exchange with pipelines of direct and return network water located in the channel, and heat exchange with soil around the channel. In addition, a regression relationship has been derived to find the integral heat flux from the listed washed surfaces to the air flow. The transition from dimensionless to natural factors has been made in the paper. The most significant factors are identified with the help of Pareto cards. The obtained dependencies have been verified in Part 1 of the paper. The adequacy of the obtained regression equations has been determined using standard statistical estimation methods based on the calculated values of the Fisher’s, Student’s and other criteria. The response surfaces are presented and analyzed using two dimensional sections for a number of factor values at fixed values of one and a change in two most characteristic, physically significant for a given response function. They have been validated on the basis of the analysis of regression dependencies. The obtained regression equations cover almost the entire range of possible diameters of heating mains, which makes it possible to use them in the development of energy-saving projects.

INCREASING THE EFFICIENCY OF COMBINED PRODUCTION HEAT AND ELECTRICITY

The main directions of increasing the efficiency of combined production of electric and heat energy are considered, associated with the improvement of power generating equipment, regime and circuit changes in heat supply systems while ensuring heat load. For many years, centralized heat supply based on combined heat and power generation has been successfully developing in Russia, which is a very attractive energy and nature saving technology. Its use makes it possible to save about 20 million tons of fuel annually, which is about 14% of the total volume of fuel consumed in Russia for the needs of heat supply. More than 50% of electricity is generated at CHPPs in Russia, and the efficiency of fuel use at them reaches about 70–75%. Such areas include the use of steam and gas technologies (CCGT units and gas turbine superstructures of equipment of operating CHPPs) and GTU-CHPPs, increasing the initial steam parameters at CHPPs, superstructure of hot water boilers with gas turbine units, improvement and modernization of existing turbine equipment and CHPP schemes, as well as rejection of peak boilers in favor of peak boilers at CHPPs, transition to a lower temperature schedule and a change in the structure of heat supply systems. The main advantages of these areas and the problems associated with their implementation are presented. The conditions of possible and expedient application of some directions are considered. It is shown that, in many respects, the choice of certain technical solutions, despite the energy efficiency, is determined by the conditions of the regional heat and electric energy markets.

Improvement of methods of comprehensive assessment of the operation efficiency of centralized heat supply systems in municipal heat power engineering

The possibility of a comprehensive assessment of the efficiency of the operation of a district heating system based on the indicator of the overall efficiency of the equipment OEE (overall equipment efficiency) and its extension to the system as a whole is considered. The disunity of the direction of existing approaches in assessing the efficiency of operation of district heating systems does not allow a comprehensive assessment of the overall efficiency of the functioning of the technological sequence of the entire system. It is proposed to consider efficiency as the probability of full functioning of all elements of the heat supply system. It is shown that the heat output of the boiler house is proportional to the power consumption of the boiler house and is approximated by a periodic function. It is shown that the main element of the heat supply system, which determines its efficiency, is the heat-generating source. As a result of the study, it is determined that the efficiency of the heat-generating source functioning increases as the maximum value of its efficiency is reached. Numerical modeling has shown that the flexible use of the installed heat generator capacity contributes to an increase in the efficiency factor from 0.53 to 0.70 and the overall efficiency of the heat supply system can be increased by more than 30 %. When designing a boiler house, it was recommended to provide for the installation of capacities with gradation 1; 0.5; 0.25. It is shown that the OEE indicator allows one to characterize the efficiency of both the heat supply system as a whole and its individual components, and can be used in the design and analysis of the operation of systems

The Use of Phosphate Compositions for Chemical Treatment of Make-Up Water in Centralized Heat Supply Systems

The paper investigates two different protective phosphate compositions for the chemical treatment of water and the use of them with a view to improve quality of “make-up” water in water heating systems. The research proved a positive effect of reducing the corrosive activity of water and the amount of scale.

The Effect of Climatic Factors on the Electric Load of Thermal Power Plants (TPP) in the Southern Federal District by the Example of the Novocherkassk District Power Plant (GRES)

A statistical analysis was performed of the electrical load curve according to which the Novocherkassk District Power Plant (NсhGRES) operated in the period between 2009 and 2018. The effect of weather and climatic factors, such as daylight time, ambient air temperature, and wind strength, on the electrical load was examined. Climatic components of the NсhGRES electric load were estimated, and it has been demonstrated that the additional lighting load depending on the daylight time in Rostov oblast was as great as 35.4%, the seasonal heating load was up to 11.3%, and the seasonal cooling load was up to 20.2% of the normal baseload. It is shown that the basic heating load in Rostov oblast is carried by centralized and individual heat supply systems, and electric heating appliances are activated when the centralized heat supply systems cannot cover the heating load due to poor maneuverability. The heating component of the electric load depends not only on the ambient air temperature but also on the wind velocity. A formula was derived using the fuzzy logic technique for calculating heat consumption in a heating system depending on ambient air temperature and wind speed. It is noted that high wind speed aggravates the negative temperature factor, bringing about the need to turn on additional heating appliances and, thereby, increasing the electrical load. A fundamental change in the shape of the annual electric load curve within the studied period was revealed: the appearance of the summer maximum load whose amplitude in terms of the indicators approached the winter one and even exceeded it in certain years, which can be attributed to the climate change in the region of the power plant site and the advent of a new type of electrical equipment, i.e., climatic control cooling units. The maximum monthly power consumption of cooling units is 1.8 times the maximum monthly power consumption of heating units and 1.7 times less than the maximum additional monthly power consumption of lighting facilities. The maximum power consumption for each type of equipment occurs in different months of the year. This change is a stable trend that should be considered, in particular, in scheduling maintenance activities at the power plant.

Energy efficient optimization of heat supply system for oil therminal

In the context of the need to develop the transport infrastructure of Ukraine and to diversify sources of energy carriers supply to the country, including oil and oil products, the problem of the development of oil terminals arises. This work is devoted to the optimization of the structure of heat supply to oil terminals. In this sense it is relevant. The object of research is the heat supply systems of an oil terminal. At the same time, the subject of research is the energy efficiency of heat supply systems for oil terminals using water vapor and high-temperature organic heat carriers. The following research methods were used: an analytical review of information sources, a technical and economic analysis with the necessary substantiating calculations. As a result of the studies, the possibility of using high-temperature organic heat carriers for organizing heat supply to oil terminals has been shown. The advantage in the efficiency, environmental friendliness and reliability of systems with high-temperature organic heat carriers versus systems using water vapor as a heat carrier is shown. On-site heating networks in the oil terminal are recommended. The main advantages are that the heat losses in them have been reduced and the reliability of the system has increased. The cost estimation of capital investments of the compared variants of the heat supply system arrangement is carried out. The centralized heat supply systems have greater equipment cost compared with the decentralized ones. The operating cost for decentralized systems is also lower due to a decrease in specific fuel and electricity consumption. The materials obtained as a result of the research can be used as recommendations for the design of heat supply systems for oil terminals using high-temperature organic heat carriers.

Energy efficiency of buildings in the cities of Ukraine under the conditions of sustainable development of centralized heat supply systems

In the current economic situation in Ukraine, the operation of heat supply systems occurs at a reduced temperature of circuit water. The increased temperature graph of 95/70 °C due to the high cost of fuel is impractical. The experience of such countries as Denmark, Germany, Finland, Sweden and Holland with developed centralized heat supply indicates the need for the first-class equipment of an individual heating point (IHP) of a building with an automatic control system, and then the transition to technology with a reduced temperature graph is carried out. Therefore, the modernization of heat supply systems in Ukraine aimed at the use of a reduced temperature graph will require a transition to closed independent heating systems, to qualitative and quantitative regulation and to automation of consumer IHP systems. A lot of district heating systems in Poland also require modernization to meet the requirements of the European Directive EED 2018/2002. This paper presents the results of numerical study of the influence of design and operating parameters of the heat supply network on the choice of the optimal temperature and flow- rate of circuit water of a distric heating system (DHS).

Impact Analysis of Urban Morphology on Residential District Heat Energy Demand and Microclimate Based on Field Measurement Data

In this work, we focus on investigating the relationship between urban morphology parameters and residential building space heating energy performance, comparing microclimate conditions of existing residential blocks with central heating supply. Firstly, a dataset composed of district morphological parameters that measured heat energy consumption was established. Then, effects of morphological indicators including cover ratio, average building height, and floor area ratio on building space heating energy efficiency were assessed specifically. Analysis results show that a larger floor area ratio induced a reduction in heating energy consumption density, the observed effect is notable at an initial increase of floor area ratio. Thirdly, the case study shows that the heating load of residential districts with a high built density is more sensitive to solar radiation. To further assess how and to what extent urban forms alter microclimates, on-site measurement investigated detailed changes in the thermal environment of selected residential districts before and after the operational stage of central heating supply. Analysis results demonstrate that heat energy delivered by a central heating supply could dampen the variations of local outdoor air temperatures, more notable for residential districts with a higher floor area ratio during the night period. Findings from this work would be useful for urban planners considering energy-efficient design practices.

Аналіз організації централізованого теплозабезпечення великих населених пунктів в Україні та країнах світу

The presented research is aimed at defining the features of organizing the centralized heat provision of large localities in Ukraine and countries of the world. Within the terms of the set aim, the article considers the characteristics of the main heat supply organizations of large cities of Ukraine, the major regional and municipal programs that are effective in them, and the characteristic features of heat supply; the main problems of centralized heat supply in these localities. It is noted that Ukraine displays one of the world’s highest saturation of cities with heat networks: the total length of heat pipelines is approximately 47 thousand km in terms of two-pipe calculation. The share of centralized heating in the total structure of heat supply in Ukraine comprises about 42%. The centralized heat supply system is provided for approximately 60% of the total area, hot water supply – more than 40% of the total area of the country’s housing stock. On the basis of consideration of heat supply systems in several large cities of Ukraine, the general features of their district heating systems are identified. The experience of building a heat supply system in separated countries of the world (Russia, China, Denmark, Finland, USA, Canada, etc.) is analyzed. The scale of district heating systems in the researched world countries is considered. Modern trends in the development of district heating systems in Europe are studied and differences between Ukrainian district heating systems, including in terms of powers of local authorities in the field of heat supply, are determined. It is specified that local authorities in Ukraine are practically deprived of powers to regulate the development of CHP plants and capacities operating on renewable energy sources, which in developed countries is a priority for the development of centralized heat supply.

Развитие теплофикации в России: отечественная научная база

Relevance. The development of a scientific base in the field of thermal energy is inextricably linked with cen-tralized heat supply and its progressive direction of heating. Centralized heat production remains the main focus of improving the efficiency of heat supply systems. The scientific base, created in the Soviet period, confirmed the cor-rectness of the scientific and engineering decisions taken during its creation, made it possible to accumulate experience for improving the thermal power industry. The purpose of the study is to identify the facts of the development and practical activities of the domestic scientific base in the field of thermal energy during the years of Soviet power. The objective of the study is to analyze the features of the work of scientific institutes in the field of the devel-opment of domestic district heating at various stages of formation. Methodology. In the course of the analysis of various scientific sources, various methods were used: problem-chronological, historical, comparative methods. Thus, the choice of the historical method is applied due to the study of the dynamics of the development of the domestic science of thermal energy. Results. In the course of studying and generalizing various literary and archival sources, the study proved the fact that domestic scientific institutions have developed intensively and over the years have reached significant proportions, which have determined the development of modern thermal energy. Conclusions: In the process of studying various literary and archival sources, it can be concluded that the do-mestic scientific base in the Soviet years allowed for the perfect supply of heat energy to industrial and residential buildings of the Soviet state. These facts can contribute to the development of a strategy for improving modern domestic thermal power engineering.

Application of an alternative energy source in the form of solar radiation and carbon-based fuel flexible material for the heating of mobile farm housing

Abstract In residential and industrial premises, optimum conditions for human activity must be created. In areas without central heating supply, heating of a mobile living space is provided by solid fuel boilers. There may be fuel outages at a distance from an inhabited locality. Therefore, the purpose of the study is to create a heating system for a farmer’s house by using carbon-based fuel flexible materials and solar stations. Farmhouse heating system that heats mobile living quarters remote from power lines and communities through the use of carbon-based fuel flexible materials and solar stations is proposed by the authors. The technical result consists in that, in the claimed system, the heating device is a carbon-based fuel flexible material supplying electricity from the solar station. Carbon-based fuel flexible material is a thermal film (heating grid), which is made by interweaving longitudinal and transverse carbon filaments and, for safety reasons, covered with an electrical insulating material.

Аналіз тенденцій розвитку централізованого теплопостачання в Україні

The article is aimed at defining the main tendencies in the development of centralized heat supply in Ukraine. Objective prerequisites for the use of centralized heating sources, as well as levels of development of heat supply systems of settlements are identified. It is determined that the development of heat supply systems largely depends on climatic conditions and the climatic characteristics of certain cities of Ukraine are considered. The main stages of construction of district heating systems in localities of Ukraine are formed. Types of heat supply of cities of Ukraine are identified. The genesis of development of heat generation and heat supply processes in Ukraine is researched. The peculiarities of formation of the national legislative framework for regulation of issues on production and consumption of heat energy are analyzed. The provisions of the Concept for the implementation of the State policy in the sphere of heat supply are analyzed. Based on the carried out analysis, it is determined the following: firstly, the imbalance of financial capabilities and needs for financing investment projects of heat supplying enterprises, as well as a shortage of investment resources, which requires careful substantiation of investment programs, directions and order of modernization and reconstruction of available capacities; secondly, shifting the focus to the powers of local authorities (through decentralization of public administration), which received broad powers to license and set tariffs for heat energy, but at the same time received a wider range of obligations to maintain heat supply systems in working condition; thirdly, the lack of medium- and long-term planning for the development of heat supply systems in localities, which largely explains the current state of the heat supply sector. It is substantiated that such features of the current state of heat supply in Ukraine require the development of new approaches to planning and implementation of works on organizational-technological modernization of heat supply in conditions of limited financial resources.