Electric Heating System Research Articles

Design and optimization of a baffle-type phase-change heat storage electric heating device

Aiming at the phenomenon of excess power and large peak-valley power difference in various application areas, here we design a baffle-type phase change heat storage electric heating device. The device uses expanded graphite (EG)/paraffin (PA) as the heat storage medium, and encapsulates the EG/PA composite phase change materials (CPCM) in a rectangular slab that is directly heated using an electric heating slab. To investigate the impact of the number and thickness of the rectangular plates on the thermal storage and exothermic performance of the device, we perform three-dimensional numerical simulations. We further make performance comparisons with the commonly used shell-and-tube and concentric tube types. In addition, the designed device was optimized by adding fins using the orthogonal test method. To verify the heating effectiveness of the device, we also simulated the temperature field, PMV (Predicted Mean Vote), and PPD (Predicted Percentage Dissatisfied) of the heating room. Our investigations confirm continuous heat release of the device for 7 h during the day which meets home heating requirements. It is also shown that the heat storage and exothermic efficiency reach to 85.83% and 90.1%, respectively, after the device is optimized, the storage and exothermic efficiency increased by 8.15% and 6.43% respectively, and the real-time outlet temperature has increased by 4.98 °C compared with that before the optimization; the average indoor temperature of the heating room is 22.49 °C, PMV is 0.55, and PPD is 15.3% in line with the thermal comfort requirements. The device can realize heat storage and heating at the same time when the power is in the valley, during the peak period, the power supply is turned off and the heating is directly supplied by CPCM. compared with the direct electric heating systems can reduce users' electricity costs, and shift peaks and fill valleys and provide a broad commercialization prospect. The research results provide a reference for the design and optimization of heat storage devices and their application in practical engineering.

Energy management optimization of integrated energy system with electric hydrogen hybrid energy storage

Abstract Integrated energy system (IES) has attracted wide attention as an efficient solution to a comprehensive utilization of hybrid energy system including electricity, heat, and hydrogen in recent years. This paper investigates the stochastic optimal operation for the micro integrated electric power, heat, and hydrogen delivery system. Firstly, the mathematical model of the micro integrated energy system for residential communities and other similar scenarios is discussed, including the energy interface, power microgrid, micro-heat system and micro-hydrogen system with considerations of distributed energy supply, energy storage, load, upstream energy network interface and their mathematical models. Secondly, the correlated uncertainty, such as wind power, solar power, and loads, are considered and handled in micro integrated energy system. Finally, a scenario-based approach is proposed for the stochastic operation of micro integrated energy system. The objective function is formulated to minimize the expected total operation and environmental costs, the hourly schedule of controllable components in micro integrated energy system. Numerical results demonstrated that the effectiveness of the proposed method. The correlated uncertainty and the corresponding impacts are accurately presented in the optimization model.

Cross-sector flexibility, storage investment and the integration of renewables: Capturing the impacts of grid tariffs

This article captures the role of electricity grid tariffs in the flexible electrification of district heating in the Nordic region at the horizon of 2050, in a situation of limited and optimal interconnections. Optimization of electricity and district heating systems is performed using the Balmorel energy systems model. Our results indicate that current volumetric tariffs substantially limit investment and flexibility from power-to-heat technologies and seasonal thermal storage in district heating. We also demonstrate how the additional flexible coupling of district heating enabled by adapted grid tariffs affects investment and generation in the electricity sector through a ratchet effect. We show that appropriate tariffs may result in up to 27% more electrification in district heating, 5% more wind and solar capacity investment in the electricity sector and up to 12% more wind and solar generation. Our results shed new light on the role of grid tariffs in the energy transition and inform policy-makers about the dynamics at play around tariff designs.

A dual-driven linear modeling approach for multiple energy flow calculation in electricity–heat system

The multiple energy flow (MEF) model is inherently nonlinear, which challenges the fast steady-state analysis and the efficient optimization of the integrated energy system (IES). This paper presents a hybrid mechanism- and data-driven (dual-driven) modeling approach to generate accurate linear models for MEF calculation. A linear regression model for the electricity–heat system is proposed to represent the underlying linear relationship among electrical, thermal, and hydraulic variables. Partial least squares (PLS) regression is used to deal with data collinearity which may lead to over-fitting. Furthermore, a dual-driven modeling approach is proposed to realize the complementarity between mechanism- and data-driven approaches. In this approach, mechanism analysis screens critical features before data processing and provides a fundamental linear model based on physical mechanism. Data-driven regression generates linear models to replace the complicated nonlinear elements and trains an approximation error model to further improve the overall accuracy. Numerical findings on a basic and a complex electricity–heat system confirmed the dual-driven linear model’s accuracy advantage over existing linear models. Overall, this study proposes a dual-driven modeling approach that provides high-precision linear models while avoiding the intractable convergence problem in the nonlinear MEF calculation. It also reveals that linear models driven by data and mechanisms can closely fit the energy flows in the nonlinear electricity–heat system.

Preparation and thermal performance enhancement of sodium thiosulfate pentahydrate- sodium acetate trihydrate /expanded graphite phase change energy storage composites

Heat energy storage using phase change materials (PCMs) in electric radiant floor heating system (ERFHS) is a favorable solution to the improvement of energy efficiency. In this paper, the sodium thiosulfate pentahydrate (Na2S2O3•5H2O,STP)- sodium acetate trihydrate (CH3COONa•3H2O, SAT) eutectic mixture was prepared by adding 30 wt.% STP and 70 wt.% SAT. Sodium carboxymethyl cellulose (CMC) and sodium pyrophosphate (Na4P2O7,TSPP) were added to fabricate the modified STP- SAT phase change material. The results showed that almost no phase separation occurred in STP- SAT eutectics with 1 wt.% CMC and 0.4 wt.% TSPP, and its supercooling degree was reduced to 0.3 °C. The thermal properties of the composite phase change material (CPCM) with different contents of expanded graphite (EG) were studied. And the experimental results showed that the composite containing 8% EG displayed a high phase change enthalpy (186.0 kJ/kg) and an ignorable supercooling degree. The addition of EG increased the thermal conductivity of STP-SAT from 0.748 to 2.92 W/m•K. The thermal reliability of CPCM was confirmed through the thermal cycle test and thermogravimetric analysis (TGA). After 200 thermal cycles, CPCM exhibited fantastic thermal stability and reliability.

Matching-design for inverter air-source heat pump system based on heating load characteristics of civil buildings

Although the inverter air-source heat pump (IASHP) and composite systems have a characteristic of energy conversion, the design of IASHP and the application of IASHP assisted with additional heat sources are absent based on the relationship between the demand side and supply side. Therefore, this paper proposes a heating load decomposition method to design IASHP with an auxiliary heat source system to offer users heating in severe cold regions. Specifically, the heating load decomposition method divides the heating load of the civil building into three regions by seeking heating energy balance points. It can get an optimal heating energy balance point with the best HSPF and an optimal design heating energy balance point with the best evaluating parameter. On these grounds, we produce an IASHP prototype. The experimental results confirm the superiority of the heating load decomposition method. Compared to the traditional design method, it improves by 6.5%-12.6% of heating capacity and 2.3%-17.4% of COP of IASHP porotype. Besides, the heating performance of IASHP assisted with an electric heating system selected by an optimal heating energy balance point is better than that of an independent IASHP heating system. In contrast, electric heating only pays 6.7% of the heating capacity of the IASHP unit operated at −27.0 °C of ambient temperature.

Mobile Equipment for Transportation and Storage of Water Reserves

In conditions of reduced freshwater reserves, the problem of its extraction of transportation and storage requires scientific justification of the relevant technical and technological solutions and the development of technical means. The article offers a mobile drinking water module. The design of the module provides for its placement in a thermally insulated container including a system of heating, power supply, distribution, filling and disinfection of water. For the development of the drinking water module, modern technical solutions are used to reduce the heat loss of the tank due to the use of a composite material and a cable of electric heater system. Reduction of microorganism propagation activity in water is provided by ultraviolet treatment and disinfection through ultraviolet gate. The design of the container is designed taking into account the possibility of its transportation in all modes of transport as a separate cargo unit. With the device of belts for loading and unloading. For loading into cars without the use of crane equipment, extendable outriggers are installed in the container, which can be used to install the container on water distribution sites. Mobility of the drinking module is ensured by the inclusion of a diesel generator unit in its composition. The tank of the module is made of stainless steel ensuring the safety of water without the formation of harmful impurities in it, and the coating of the tank with a composite material creates the effect of a thermos. The function of filling and distributing water from the tank is implemented using a distribution column with a vortex pump of a system of shut-off valves and hoses for supplying water. Experimental studies of mobile module operation have been performed. It was established that in order to maintain the water temperature in the tank at 10 ° C at an ambient temperature of minus 30 ° C, the heating system should not be switched on. The innovative design of the heat insulated layer reduces the thermal conductivity of similar water storage tanks made of traditional materials by 4 times. The proposed design of the mobile drinking module provides the possibility of creating clean water reserves for catering and household supplies.

Electric supplementary heating technology of municipal heating for city heat exchange station

Municipal heating in northern areas generally suffers from heat sources, heat grid gaps, and high dependence on fossil fuels. It is difficult to guarantee the heating effect of incremental buildings at the end of the building, and relying on traditional capacity expansion methods has caused a waste of social resources to a certain extent. A “no capacity increase” municipal heating electric supplementary heating technology for urban heat exchange stations is proposed. First, the design concept of the electric supplementary heating system is explained. Then, the investment calculation model of the electric supplementary heating system is established. Finally, an office building in Shijingshan, Beijing is used as a research example to perform simulation calculations.

Simulation Research on Performance of a Novel Heating and Cooling System with Thermoelectric Module

This work proposes a novel heating and cooling system, with incorporated thermoelectric module, that can achieve energy balance using a self-water supply heat exchange subsystem. The thermoelectric effect is used to achieve controlled and adjustable heating of the circulating water. Simulations were conducted to study the thermal performance of the system while it simultaneously produces hot and cold water, with different working conditions for the hot-and cold-side water outlets. The results show that the water temperature at the hot side outlet increases from 32°C to 75°C when the power increases from 4.5 to 50 W. Additionally, the use of thermoelectric modules to heat water and recover waste heat is 22% more efficient than ordinary electric water heating systems.

Adjustable Robust Interval Economic Dispatch of Integrated Electricity and District Heating Systems Under Wind Power Uncertainty

Adjustable Robust Interval Economic Dispatch of Integrated Electricity and District Heating Systems Under Wind Power Uncertainty

A Double-Deck Deep Reinforcement Learning-Based Energy Dispatch Strategy for an Integrated Electricity and District Heating System Embedded with Thermal Inertial and Operational Flexibility

A Double-Deck Deep Reinforcement Learning-Based Energy Dispatch Strategy for an Integrated Electricity and District Heating System Embedded with Thermal Inertial and Operational Flexibility

Study of experimental resource-saving mould operation for subsequent casting of aluminum alloys into it

A patented design of a steel mould operating on the principle of a heat pipe, with a two-circuit cooling system for casting of cylindrical billets with a diameter of 60 mm made of high-alloy aluminum alloys, is made. Preliminary studies of the mould operation are carried out, based on the use of an electric wall heating system, as well as modeling of the thermal operation of the mould when water is supplied to the condenser casing.

Analysis on influencing factors and energy saving potential of photovoltaic curtain wall preheating fresh air system in severe cold area

In the general building air conditioning load, the fresh air load accounts for more than 30%, especially in the severe cold areas in the north, with long winter and large indoor and outdoor temperature difference, the fresh air heat load will account for a larger proportion in the air conditioning system load. Making full use of renewable energy can effectively reduce building energy consumption. In this paper, the air flow field distribution in the ventilation duct of photovoltaic curtain wall is numerically simulated by fluent simulation software, and the air distribution form and temperature field distribution in the system cavity under different ambient temperature, cavity thickness and tuyere position are analyzed and compared, so as to obtain the influence of different influencing factors on the performance of the fresh air preheating system, and combine the photovoltaic curtain wall preheating fresh air system and electric heating system to explore its energy-saving potential. The results show that when the cavity thickness is greater than 400mm, the reduction range of photovoltaic curtain wall temperature becomes smaller, and the overall temperature distribution of the cavity tends to be uniform. When the ambient temperature is different, with the increase of ambient temperature, after the fresh air passes through the photovoltaic curtain wall preheating system, the temperature difference at the inlet and outlet of the air flow channel decreases, and the maximum temperature difference decreases from 4.6k to 3.4K.The combination of photovoltaic curtain wall and electric heating is used to preheat the fresh air. Compared with the traditional method, the same fresh air load is treated, and the energy-saving rate is 60% ∼ 70%. It shows that using photovoltaic curtain wall to preheat the fresh air can achieve better results, which provides guidance for putting forward more appropriate, economic and energy-saving design schemes in the project.

Synchronized Full-Field Strain and Temperature Measurements of Commercially Pure Titanium under Tension at Elevated Temperatures and High Strain Rates

Understanding the mechanical behavior of materials at extreme conditions, such as high temperatures, high strain rates, and very large strains, is fundamental for applications where these conditions are possible. Although tensile testing has been used to investigate material behavior under high strain rates and elevated temperatures, it disregards the occurrence of localized strains and increasing temperatures during deformation. The objective of this work is to combine synchronized full-field techniques and an electrical resistive heating system to investigate the thermomechanical behavior of commercially pure titanium under tensile loading at high temperatures and high strain rates. An electrical resistive heating system was used to heat dog-bone samples up to 1120 °C, which were then tested with a tensile Split Hopkinson Pressure Bar at strain rates up to 1600 s−1. These tests were monitored by two high-speed optical cameras and an infrared camera to acquire synchronized full-field strain and temperature data. The displacement and strain noise floor, and the stereo reconstruction error increased with temperature, while the temperature noise floor decreased at elevated temperatures. A substantial decrease in mechanical strength and an increase in ductility were observed with an increase in testing temperature. The localized strains during necking were much higher at elevated temperatures, while adiabatic heating was much lower or non-existent at elevated temperatures.

Experimental investigation of flow and exergy transfer characteristics in the air-cooled randomly packed particle bed based on second law analysis

Randomly packed particle beds (RPPB) are widely used in industry, and their internal flow and heat transfer characteristics have a significant impact on the energy efficiency of the overall system. Based on the second law of thermodynamics theory, the correlation equation to predict the exergy transfer coefficient (ETC), exergy transfer Nusselt number (Nuex) within the RPPB is developed, which can reflect temperature and pressure exergy transfer. It effectively reveals the relationship between the role of heat transfer and pressure loss. The experiments are then carried out using stainless-steel particles packed bed with an electric induction heating system to provide a uniform internal heat source. The ambient air is used as the test fluid to cool the heated particles. The pressure drops and forced convection heat transfer characteristics of air-cooled high-temperature particles are investigated. The experiments are performed for flows with modified Reynolds number Redh in the range of 811–6810. The effects of cooling air inlet velocity (ua,in) and electromagnetic induction heating power (Qe) on the experimental results are investigated under different particle sizes (dp = 6 and 8 mm). The results show that when dp and Qe are constant, the overall Nuex decreases exponentially with increasing Redh, and even becomes negative. It means that the heat gain of the air through the RPPB is lower than the pressure loss. The critical Redh are 2650 and 5300 when dp = 6 and 8 mm, respectively. At fixed dp and ua,in, Nuex,T decrease linearly with the increase of Redh. In the case of low Qe, the exergy transfer between the particles and air is mainly based on pressure exergy transfer. As the Qe increases, the temperature exergy transfer gradually increases and dominates, and Nuex shifts from negative to positive. This study delves deeper into the forced convective heat transfer process in RPPB, comprehensively considering the effects of heat transfer and pressure loss.

Mission aborting and system rescue for multi-state systems with arbitrary structure

Rescue procedures (RP), triggered either by the occurrence of the mission failure or by a certain undesired system state, are usually applied to survive a life-critical or safety-critical system mitigating or avoiding costly consequences. Existing works model either the mission failure-triggered RP or the system state-triggered RP, but not both. This paper makes contributions by co-modeling both types of RPs in the reliability analysis of multi-state systems with arbitrary structure and heterogeneous system elements. The system performs a primary mission (PM) with the specified time duration. System configuration (i.e., required subset of working elements and system functioning criteria) and reliability characteristics of system elements are different during PM and RP. A probabilistic modeling method is proposed to analyze reliability metrics of the considered system in forms of mission success probability (MSP) and system survival probability (SSP). Based on the MSP and SSP evaluation, two types of mission abort rules (performance constraint-based and system state subset-based) are investigated and compared. An example of an electrical heating system is provided to illustrate the proposed method and solutions to the optimal mission aborting policy that maximizes MSP subject to meeting a certain level of SSP.

Collaborative scheduling of source-network-load-storage considering thermal inertia of the integrated electricity and district heating systems

ABSTRACT With the strengthening of carbon emission control, the development of clean renewable energy has become a unanimous choice for many countries. However, in the integrated electricity and district heating system (IEDHS), the tightly coupled relationship between heat and electricity will make the system lack the flexibility for wind power integration. A source-network-load-storage scheduling scheme considering thermal inertia (TI-based SNLS scheduling) is proposed to realize the coordinated operation of source, network, load, and storage in IEDHS. The simplified thermal inertia model of district heating network (DHN) and building, and the charging-discharging model of a solid regenerative electric boiler (SREB), are also introduced. Four comparative cases are conducted based on wind power data of Jilin Province for a day-ahead dispatch problem. The results indicate that the scheme achieves a 9.19% improvement on the regulation flexibility of the combined heat and power (CHP) units, and the wind curtailment rate is reduced by 16.14%. The research also finds that using thermal inertia can alleviate the contradiction between heat load and wind power curve, but the contribution from DHN is limited compared with buildings. SREB can directly absorb wind power to compensate for heating, which has considerable potential in promoting wind power utilization. Furthermore, the indicative calculation of financial payback time considering carbon trading income elucidates the economic feasibility of the case system.

Snow-melting pavement design strategy with electric cable heating system balancing snow melting, energy conservation, and mechanical performance

Electric cable heating (ECH) system is a promising pavement snow-melting technology. However, the long-term operation of such systems entails considerable energy consumption, and results in energy waste and high economic cost. Relevant studies lack design strategies that simultaneously ensure optimal energy conservation, snow-melting performance, and mechanical performance of ECH systems. Moreover, the long-term performance of this pavement remains to be verified. Therefore, this study investigated comprehensive energy conservation design strategies for ECH systems. The effects of various parameters on an ECH system's snow-melting, energy consumption, and mechanical response were investigated using the finite element method. On the basis of the simulation results, a recommended design strategy was proposed which can conserve energy and ensure the system's snow-melting function and long-term structural safety. With this strategy, an ECH system was designed and constructed. The calculation results demonstrate that this strategy can reduce energy waste significantly while ensuring the snow-melting function. Moreover, in a field experiment, a one-third scale model mobile load simulator was adopted. After continuous loading 400,000 times, the average rutting depths of all test sections were less than 3 mm, which verified the long-term mechanical performance of the ECH system designed using the developed strategy.

Influence of CMC on the electrical and heating performance of carbon papers planar heating elements under low power

Carbon-based planar heating elements, such as carbon papers (CP), are advantageous over conventional metal-based heating systems because of their performance in terms of conductivity, thermal and mechanical properties, and cost. In this study, we optimized manufacturing of CP, to ensure uniform dispersion, according to the carboxymethylcellulose (CMC) concentration using a wet-laid process for an electric heating system with 6 mm length chopped polyacrylonitrile (PAN)-based carbon fibers (CF), polyvinyl alcohol (PVA) fibers, and CMC, and examined the electrical, thermal, and mechanical properties of the CP.

Coordinated energy management strategy in scheme of flexible grid-connected hubs participating in energy and reserve markets

This paper uses the coordinated energy management strategy for different sources and storages in the framework of flexible grid-connected energy hubs that participate in the day-ahead (DA) energy and reserve markets. In the base problem, this method maximizes the difference between the expected revenue of hubs gained by selling energy and reserve power in the proposed markets and the expected cost of lost flexibility (COLF). Also, it is subject to linearized optimal power flow (LOPF) equations in the electricity, gas and district heating systems, as well as hub constraints including different sources, storages and reserve models. This problem contains uncertainties of load, market price, reserve requirement, renewable power and hub mobile storages parameters. Therefore, the hybrid stochastic/robust optimization (HSRO) is suitable to model these uncertain parameters and obtain robust capability for the hub to improve the system flexibility. Accordingly, the bounded uncertainty-based robust optimization (BURO) is used in this paper to model the uncertainty of hub mobile storages to achieve the hub robust potential in improving the system flexibility, and other uncertain parameters are modeled according to scenario-based stochastic programming (SBSP). Finally, the proposed strategy is implemented on a standard test system. The obtained numerical results confirm the capability of the suggested scheme in improving the economic status of sources and storages using the coordinated energy management strategy in the form of an energy hub, as well as enhancing economic conditions, operation, and flexibility of energy networks thanks to hubs for having access to optimal scheduling.