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This paper introduces a novel a CO2 mechanical subcooling heat pump water heater (MSHPWH) to improve the heating performance in low temperatures. By utilizing a mechanical subcooling (MS) cycle, additional heat is supplied to cooling water, improving system efficiency. The study evaluates the heating COP (COPh), power consumption and temperature of hot water under various steady-state operating conditions. Results indicate that the COPh of the MSHPWH increases by 44% to 57% compared to conventional HPWH as ambient temperatures range from -25 ℃ to -5 ℃. The MS cycle proves beneficial, with a subcooling range of 4 ℃ to 20 ℃. Adjusting the refrigerant mass flow rate ratio enhances heating output and hot water temperature. Changes in the mass flow rate ratio impact COPh and the temperature of hot water concurrently. This research highlights the innovative MS cycle's significant role in enhancing CO2 heat pump water heater performance in cold climates, showcasing its potential as an eco-friendly and efficient heating solution. [ABSTRACT FROM AUTHOR]

• Non-invasive composition determination from six different measurements experimentally verified. • Composition determination from density data most accurate and robust. • Data from system level heat pump testing sufficient for rapid mixture model evaluation. • REFPROP mixture models for R-1234yf/1233zd(E), R-1234yf /1336mzz(Z), R32/1224yd(Z) and several ternary mixtures thereof proven useful for system level design. Refrigerant mixtures are frequently used in air-conditioners and heat pumps. However, mixtures with high glides of 30 K and more during evaporation are rare, partially because there is an increased concern about composition shifts within the system. An easy and reliable inline composition measurement could alleviate these concerns and simplify the handling of systems with high-glide mixtures. This study investigates six composition determination methods, which are all non-invasive, five of which can be conducted during system operation. All methods were applied to all available mixtures in a dataset of 380 data points. The binary and ternary mixtures tested consist of the refrigerants R-1233zd(E), R-1336mzz(Z), R-1234yf, R-1224yd(Z), and R-32. Each method was applied to all datapoints collected with a certain refrigerant mixture at varying operating conditions. The average of the calculated mass fraction was then compared to the manually charged mass fraction. For the density method, this difference of the calculated and measured mass fraction was always less than 0.03 and usually smaller than 0.01 across all tested mixtures. Most other methods performed well with deviations typically less than 0.05. Some of the methods require only low-cost sensors like thermocouples and pressure transducers. Property data of ternary mixtures is also discussed in the study but a composition determination, theoretically possible combining any two of the six methods, is not attempted in this study. [ABSTRACT FROM AUTHOR]

• COP improvements of up to 16 % experimentally shown for high-glide mixtures compared to pure refrigerants. • COP of mixtures more robust against changes of operating conditions than pure fluids. Climate change necessitates the reduction of primary energy consumption. Industrial heat pumps can contribute by replacing oil and gas fired boilers in various applications. To cater the application, heat pumps must often impose temperature differences of 25 K or more to the heat source and heat sink, causing great irreversibility if evaporation and condensation occur at constant temperatures. Many theoretical studies suggest that high-glide refrigerant mixtures designed to match the temperature differences have a superior COP for such applications. In contrast to the numerous theoretical studies, systematic experimental studies are missing. This study tests high-glide mixtures at varying compositions at constant operating conditions. COP improvements of 16 % are shown comparing the best mixture against the best pure fluid. The improvement was established despite a significant degradation in the heat transfer coefficient, which could presumably be alleviated with larger heat exchangers. Additional parametric studies are conducted on the temperature differences of heat sink and source as well as the temperature level. The results show that mixtures not only outperform pure fluids at certain operating conditions but can maintain a higher COP across varying operating conditions. The binary and ternary mixtures in this study have glides between 10 and 40 K and consist of R1336mzz(Z), R1233zd(E), R1224yd(Z), R1234yf and R32. [ABSTRACT FROM AUTHOR]

• Screening non-fluorinated refrigerants with low GWP and reduced flammability. • Performance criterion characterizing heating capacity for low-charge heat pumps. • The most attractive refrigerants were identified through decision-making techniques. • DME-CO 2 mixtures resulted in improvements in efficiency and levelized cost of heat. • Further investigations were recommended on mixtures with DME, Propylene and CO 2. The study investigated the characteristics of different natural refrigerants and their mixtures in a residential heat pump with low refrigerant charge. Three main evaluation criteria were utilized for comparing different mixtures: Coefficient of Performance (COP), Volumetric Heating Capacity (VHC), and a newly proposed indicator, the heating capacity at charge limit. Propane was used as a reference refrigerant. It was found that some mixtures significantly improved both COP and the heating capacity at charge limit while maintaining similar volumetric heating capacity and operating conditions. Alternative multi-criteria decision-making techniques were adopted to rank the best refrigerant mixtures. Mixtures rich in Dimethyl Ether (DME), such as DME-CO 2 [0.96-0.04] and DME-Propylene [0.75-0.25] were found consistently among the best options. Those were followed by Propylene-rich mixtures such as Propylene-CO 2 , Propylene-Isobutane and Propylene-Butane. The levelized cost of heat (LCOH) could be improved by up to 12 %. To accelerate the transition to natural refrigerants, without compromises on efficiency and costs, further research and certification activities on non-fluorinated refrigerants based on Dimethyl Ether (R-E170), CO 2 (R-744) and Propylene (R-1270) are recommended. [ABSTRACT FROM AUTHOR]

The paper explores the performance of a sub-slab ground heat exchanger, coupled to a heat pump, and the ability of the system to provide space conditioning and domestic hot water (DHW) for a multi-unit residential building (MURB) located in Ottawa, Ontario. The parametric analysis conducted to optimize the design of the building, as well as the sensitivity analysis performed to optimize the configuration of the sub-slab ground heat exchanger is also presented. According to the simulated results, the ground layer can store some of the rejected energy over medium term, without reducing the long-term performance of the heat pump. The annual energy consumption per dwelling unit (including heat pump, all auxiliary equipment, appliances, and lights) was estimated to be 28.4 GJ, significantly lower than the average annual energy consumption for a low-rise apartment in Canada (46.7 GJ per apartment). To assess the sensitivity of the system to environmental conditions, the simulation was conducted using the weather files for other five locations in Canada. [ABSTRACT FROM AUTHOR]

Modeling underground temperatures provides a practical application of the one-dimensional heat equation. In this work, the one-dimensional heat equation in surface soil is extended to include heat carried by the vertical flow of rainwater through the soil. Analytical solutions, with and without water flow, illustrate the influence of rainwater circulation on the sub-surface propagation of seasonal temperature variations, an important effect that is generally neglected in textbooks. The surface temperature variations are damped by the soil, and this effect was used by the Troglodytae in Egypt or the Petra in South Jordan to insulate against extreme temperatures. For a realistic case of horizontally layered geology, a finite volume Python code was developed for the same purpose. Subsurface temperatures were also measured over a full year at depths up to 1.8 m and used to estimate the thermal skin depth and thermal wavelength. This study provides students with a practical example of how a textbook physics problem can be modified to extract information of contemporary importance in geophysics and global warming. Editor's Note: Frequently, modeling the three-dimensional world is too challenging for a class exercise, and we instead teach students using unrealistic one-dimensional problems. So it is wonderful when a one-dimensional model turns out not only to be fairly accurate, but also to have real world implications. That is the case with heat flow through the soil, which can be treated with a one-dimensional model, and which is important to energy-efficient solutions such as underground housing and ground-source heat pumps. This paper finds the underground temperature as a function of depth through measurements, analytical solutions, and computational solutions. These solutions can form the basis for a very interesting class assignment. In addition to considering heat transport through conduction, the model also includes heat transport through the flow of rain water. [ABSTRACT FROM AUTHOR]

CO2 refrigeration and heat pump systems have gained widespread attention due to their environmentally friendly features. However, their application is limited by high operating pressure and limited refrigeration performance. To address this, the technology of adding other refrigerants to CO2 to form a CO2-based mixture has emerged as an effective solution, as it reduces operating pressure and improves energy efficiency. Although CO2-based mixtures can be mixed in any ratio, there is an optimal composition ratio that maximizes performance under given working conditions. However, as working conditions change, the optimal composition ratio also changes, and fixed compositions cannot achieve the best energy efficiency throughout the year. Therefore, this paper studies four types of CO2-based mixtures, namely CO2/R32, CO2/R290, CO2/R1270, and CO2/R1234yf， and proposes a CO2-based mixture refrigeration and heat pump systems composition adjustment scheme that adjusts the system's composition according to different working conditions. The paper designs two composition adjustment strategies, studies the limits of composition adjustment using different methods, and evaluates the energy-saving performance of different adjustment methods. The results show that the maximum range of composition adjustment is between.25 and.97， and the energy-saving of up to 27.2% can be achieved through composition adjustment in some areas. [ABSTRACT FROM AUTHOR]

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes, for the first time, the research concept of comparing energy and economy between transcritical cycle high-temperature heat pumps and subcritical cycle high-temperature heat pumps with new refrigerants. Experiments and simulations are conducted to compare the system performance and economy of two heat pumps, and the effects of different factors on the performance of two heat pumps are analyzed. The results show that R744/R1234yf (90/10) and R515-1 are the preferred refrigerants for transcritical cycle heat pumps and subcritical cycle heat pumps, respectively. The COP of the R744/R1234yf (90/10) transcritical heat pump is generally higher than that of the R515B-1 subcritical heat pump, and compared to the R515B-1 subcritical heat pump, the cost recovery period of the R744/R1234yf (90/10) transcritical heat pump is about 9–15 years. Therefore, it is recommended that users who use heat pumps for a long time choose transcritical cycle heat pumps. Meanwhile, with the change of evaporation temperature, the system COP of the R515B-1 subcritical heat pump and R744/R1234yf (90/10) transcritical heat pump increases by 61.11% and 65.91%, respectively. In addition, the optimal charge amount for the R515B-1 subcritical heat pump is 81.8% of that of the R744/R1234yf (90/10) transcritical heat pump. [ABSTRACT FROM AUTHOR]

The present work represents a continuation of our research in the field of evaluating the thermal efficiency (coefficient of performance) of a heat pump, research started and published in 2019 [1]. In the previous work it was considered the refrigerating machine, this time we will refer exclusively to the mechanical vapor compression heat pump. The evaluation of the COP for a heat pump is absolutely mandatory in the calculation procedure of contribution of the renewable resources of energy, offered by the implementation of a heat pump in the thermal utility supply systems in buildings (space heating and/or hot water preparation). [ABSTRACT FROM AUTHOR]

Currently, approximately 40% of the energy demand in the European Union (EU) is used in buildings and the energy demand for cooling and heating is increasing every year, so the energy efficiency of buildings represents a problem of increased interest and of extreme relevance. The article proposes, through the case study, the installation of a photovoltaic system for the production of electricity on the roofs of the buildings and the cooling and heating of the building using a water-to-water heat pump. Having the advantage of the location of the studied buildings on the banks of the river Bega in the town of Timisoara, the case study proposes the cooling of the spaces in the buildings in two variants, namely in the spring and autumn when the outside temperature is not very high using the river water directly ("free cooling"), and in the summer for the hot months, a water-to-water heat pump to cool the cooling agent to the parameters necessary to achieve a proper air conditioning. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyses the solutions for the heating and domestic hot water supply system for a modernized hotel in the city of Chisinau for the climatic conditions of the Republic of Moldova. In the paper, the implemented solutions were analyses, the investment recovery term was determined. The Republic of Moldova does not have its own energy sources, and the need to implement alternative sources is obvious. In this sense, the use of heat pumps, photovoltaic panels form an energy efficient, economical and more ecological system than any thermal energy generating installation [ABSTRACT FROM AUTHOR]

The paper presents the study conducted to determine the impact of HVAC geothermal systems with heat pumps units on the ground and groundwater. Due its very complexity the HVAC geothermal system with heat pumps units that equips the ELI-NP research infrastructure could be a suitable tool to determining the long-term impact of shallow geothermal systems on the environment. The system has been continuously operating and monitored for 5 years. [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Civil Engineering / Revista Română de Inginerie Civilă is the property of Matrix Rom and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study focused on optimizing a model house for different locations and types of thermal systems to understand better how heating system type affects thermal envelope design, operational greenhouse gas emissions, and life-cycle cost. The study investigated six different thermal system configurations in separate optimizations for five locations. Optimization implies reducing energy consumption, minimizing greenhouse gas emissions (GHG), lowering operational costs, ensuring regulatory compliance, enhancing resilience, and improving occupant comfort and health. The Pareto front, multi-objective optimization, is used to identify a set of optimal solutions, considering multiple goals that may conflict with each other. In determining the least-cost building design envelope, the design balances costs with other goals, such as energy efficiency and environmental impact. The optimizations determine the life-cycle cost versus operational GHG emissions for a single-detached house in Canadian locations with varying climates, emissions factors, and energy costs. Besides natural gas, the study evaluated four electricity-heated options: (a) an air-source heat pump, (b) a ductless mini-split heat pump, (c) a ground-source heat pump, and (d) an electric baseboard. A net-zero-carbon design with grid-tied photovoltaics was also optimized. Results indicate that the heating system type influences the optimal enclosure design. In each location, at least one all-electric kind of design has a lower life-cycle cost than the optimized gas-heated model, and such designs can mitigate the majority of operational GHG emissions from new housing in locations with a low carbon electricity supply. [ABSTRACT FROM AUTHOR]

As the application of renewable energy becomes increasingly extensive, heat pump technology with renewable energy as the heat source is achieving good results. Air-source heat pumps and water-source heat pumps can be widely used in cold areas. In this work, an integrated combined storage and supply system of an air-source heat pump and a water-source heat pump was studied, and the heating characteristics of the system at the beginning, middle, and end of the heating period were examined. It was found that, when the outdoor temperature of the system was very low, the efficiency of the combined storage and supply system reached the highest value of 2.57 when the source-side water tank was kept at 30 °C, and the performance of the combined storage and supply system was better than that of the air-source heat pump and the water-source heat pump in cold regions. Meanwhile, the independent storage of the air-source heat pump and the combined storage and supply system can be used for heating at the beginning and end of the heating period. [ABSTRACT FROM AUTHOR]

A cooling tower-assisted ground source heat pump system is proposed to solve the problem of soil heat accumulation in areas with hot summers and mild winters. TRNSYS is used to establish the simulation model of the ground source heat pump system. Taking the ground source heat pump demonstration project in Nanchang City as the research object, the operation effect of the ground source heat pump is simulated and analyzed. The key parameters of the optimization system are proposed, and the operation time of the cooling tower is controlled. The optimization results show that the cooling tower can not only improve the system performance in a short time but also enable long-term stable and efficient operation of the refrigeration system, the compound ground source heat pump system optimized by the cooling tower has almost no soil heat accumulation, and the system performance has been improved. The optimal running time of the cooling tower is 3216~4344 h and 5424~6696 h, and the system running effect is the best at this time. The research results can provide a theoretical basis for the optimal design of the cooling tower auxiliary ground source heat pump system. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In extremely cold environments, when battery electric vehicles (BEVs) are navigating urban roads at low speeds, the limited heating capacity of the on-board heat pump system and positive temperature coefficient (PTC) device can lead to an inevitable decline in battery temperature, potentially falling below its permissible operating range. This situation can subsequently result in vehicle malfunctions and, in severe cases, traffic accidents. Henceforth, a novel battery self-heating method during driving is proposed to maintain battery temperature. This approach is ingeniously embedded within the heating mechanism within the motor driving system without any necessity to alter or modify the existing driving circuitry. In the meantime, the battery voltage can be regulated to prevent it from surpassing the limit, thereby ensuring the battery's safety. This method introduces the dead zone into the space vector pulse width modulation (SVPWM) algorithm to form the newly proposed dSVPWM algorithm, which successfully changes the direction of the bus current in a PWM period and forms AC, and the amplitude of the battery alternating current (AC) can also be controlled by adjusting the heating intensity defined by the ratio of the dead zone and the compensation vector to the original zero vector. Through the Simulink model of the motor driving system, the temperature hysteresis locking strategy, grounded in the field-oriented control (FOC) method and employing the dSVPWM algorithm, has been confirmed to provide controllable and sufficiently stable motor speed regulation. During the low-speed phase of the China Light Vehicle Test Cycle (CLTC), the battery temperature fluctuation is meticulously maintained within a range of ±0.2 °C. The battery's minimum temperature has been successfully locked at around −10 °C. In contrast, the battery temperature would decrease by a significant 1.44 °C per minute without the implementation of the temperature-locking strategy. The voltage of the battery pack is always regulated within the range of 255~378 V. It remains within the specified upper and lower thresholds. The battery voltage overrun can be effectively avoided. [ABSTRACT FROM AUTHOR]

Industrial buildings have numerous kinds of energy-losing equipment, such as engines, ovens, boilers and heat exchangers. Energy losses are related to inefficient energy use and lousy work conditions for the people inside the buildings. This work is devoted to the recovery of lost energy from industrial buildings. Firstly, the residual energy of the building is extracted to be used to warm water. Consequently, the work conditions of the people inside industrial buildings can be improved by maintaining the adequate temperature. The recovery of the energy is performed by a multipurpose heat pump system (HP system). The working fluid used in the HP system is R134a, which is a traditional and cheap working fluid. The thermophysical properties of R134a are obtained through the PC-SAFT equation of state. This work presents a performance mapping based on the intercepted areas framework to evaluate which working conditions are the optimal operating variables. The latter depends on several key parameters, such as compressor work, heat delivery, heat absorbed and exergetic efficiency. The results show that the optimal work conditions are found at different condenser and evaporator temperatures, and these may be limited by what the designer considers a sound performance of the heat pump system. [ABSTRACT FROM AUTHOR]

A smart city (SC) includes different systems that are highly interconnected. Transportation and energy systems are two of the most important ones that must be operated and planned in a coordinated framework. In this paper, with the complete implementation of the SC, the performance of each of the network elements has been fully analyzed; hence, a nonlinear model has been presented to solve the operation and planning of the SC model. In the literature, water treatment issues, as well as energy hubs, subway systems (SWSs), and transportation systems have been investigated independently and separately. A new method of subway and electric vehicle (EV) interaction has resulted from stored energy obtained from subway braking and EV parking. Hence, considering an SC that simultaneously includes renewable energy, transportation systems such as the subway and EVs, as well as the energy required for water purification and energy hubs, is a new and unsolved challenge. In order to solve the problem, in this paper, by presenting a new system of the SC, the necessary planning to minimize the cost of the system is presented. This model includes an SWS along with plug-in EVs (PEVs) and different distributed energy resources (DERs) such as Photovoltaics (PVs), Heat Pumps (HPs), and stationary batteries. An improved grey wolf optimizer has been utilized to solve the nonlinear optimization problem. Moreover, four scenarios have been evaluated to assess the impact of the interconnection between SWSs and PEVs and the presence of DER technologies in the system. Finally, results were obtained and analyzed to determine the benefits of the proposed model and the solution algorithm. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study is dedicated to an experimental investigation of a passive two-phase ejector used as an expander in a transcritical CO2 heat pump. The investigation focused on the impact of the evaporating temperature (Tevap) and the CO2 gas cooler outlet temperature (Tgc-out) on the ejector and the overall cycle performance. The basic cycle without an ejector was also tested as a baseline for comparison. Two ejectors designed with different modeling approaches were tested and compared. The ejector with an enlarged mixing section diameter was selected for subsequent testing due to its improved pressure lift. The optimum primary nozzle position was found to be 4 times the mixing section diameter (Dmix). Although the ejector was designed for specific conditions, the results demonstrate its ability to remain operational under varying conditions with some changes in performance. The ejector's performance was observed to be dependent on the Tevap, and particularly on the Tgc-out. The pressure lift recorded was in the range of 3.7-6.5 bar, and the lowest value was obtained with the low Tgc-out value (29 °C). Under the tested conditions, the integration of the ejector enhances the performance and the capacity of the heat pump. The ejector cycle improvement is primarily based on improved mass flow rates due to increased compressor suction pressure, reduced compression ratio, and consequently, improved compressor operating conditions. Improvements of up to 18% in heating COP and 20.5% in heating capacity were observed. The study provides valuable insights into enhancing the performance of transcritical CO2 heat pump system by refining ejector design. It explores the behavior of the system across varying conditions, highlighting the significant impact of the ejector-compressor interaction on overall performance. [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Civil Engineering / Revista Română de Inginerie Civilă is the property of Matrix Rom and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thermotronics has attracted much attention driven by the promising potentials offered by devices such as thermal diodes, thermal transistors, and thermal memristors. Heat shuttling (or heat ratcheting, or heat pumping) is a phenomenon exhibited by nonlinear materials presenting temperature-dependent thermal conductivity which, when sandwiched between two thermal baths with one bath subjected to a time-varying temperature, show nonvanishing net heat flow, although the baths share the same average temperature. Phase-change materials (PCMs) like VO 2 were recently taken for illustration due to a strong change in conductivity over a small temperature range; energy extraction from the thermal variations of the environment was envisioned thereupon. However, up to now, the impact of PCM hysteresis has been either overlooked or roughly approximated. On the basis of a thermal model simulating partial hysteresis loops and nonhysteretic branches, we demonstrate that the presence of hysteresis profoundly modifies the appearance of the heat-shuttling effect and can constitute a hindrance to its manifestation. Operating configurations to improve its observation have been proposed. [ABSTRACT FROM AUTHOR]

Thermotronics has attracted much attention driven by the promising potentials offered by devices such as thermal diodes, thermal transistors, and thermal memristors. Heat shuttling (or heat ratcheting, or heat pumping) is a phenomenon exhibited by nonlinear materials presenting temperature-dependent thermal conductivity which, when sandwiched between two thermal baths with one bath subjected to a time-varying temperature, show nonvanishing net heat flow, although the baths share the same average temperature. Phase-change materials (PCMs) like VO 2 were recently taken for illustration due to a strong change in conductivity over a small temperature range; energy extraction from the thermal variations of the environment was envisioned thereupon. However, up to now, the impact of PCM hysteresis has been either overlooked or roughly approximated. On the basis of a thermal model simulating partial hysteresis loops and nonhysteretic branches, we demonstrate that the presence of hysteresis profoundly modifies the appearance of the heat-shuttling effect and can constitute a hindrance to its manifestation. Operating configurations to improve its observation have been proposed. [ABSTRACT FROM AUTHOR]

The aim of this work is the utilization of the secondary steam energy through its thermal transformation in electrodynamic dehydrators developed by the authors. To achieve this goal, the use of heat pumps is proposed. A hypothesis is formulated that the use of electromagnetic energy sources in the process of removing moisture from food solutions, followed by the transformation of secondary steam energy, will allow for the formation of reverse energy flows. A method for calculating energy efficiency in the presence of direct and reverse flows is presented. Multistage dehydrators, where electrodynamic systems are used at the final stage and heat pumps at the previous stages, are analyzed. It is shown that the formation of reverse flows significantly increases the overall energy efficiency. The use of an electrodynamic apparatus at the final stage solves the problems of obtaining a highly concentrated quality solution. The application of heat pumps at the remaining stages allows for the efficient use of secondary steam energy. The most significant result is the matching schemes of heat pumps with the dehydrator and the environment. The importance of the work lies in the substantiation and confirmation of the high energy efficiency of organizing reverse energy flows, and the proposed installation with combined systems — electrodynamic and heat pump. By calculation, the modes have been established in which the overall efficiency for two-stage apparatuses with heat pumps can be increased from 0.4 to 0.6, and for four-stage dehydrators from 0.4 to 0.8.

This paper describes a two-year high-fidelity dataset for an ultra-low energy office building and living laboratory called HouseZero®. The building integrates multiple low-energy technologies, such as natural ventilation with automatic windows, ground source heat pump, and thermally activated building systems. The building's performance is continuously monitored with an extensive sensor network. The dataset consists of breakdown energy end uses, photovoltaic (PV) production, zone-level indoor environment including indoor air temperature, CO2 concentration, and relative humidity, micro-climatical conditions, building façade temperature, and detailed system operations including zone-level BTU meter, valve status, slab temperature, window/skylight opening status, heat pump, and geothermal well operations. The data can be used to support data analytics of ultra-low-energy building operations, and data-driven modeling of low-energy building systems. [ABSTRACT FROM AUTHOR]

The incorporation of ejectors into heat pump and refrigeration cycles has been the subject of growing interest, largely due to their simple structure, high reliability, and cost-effectiveness. This paper investigates the recent advancements in novel design concepts of ejector-enhanced vapor compression heat pump and refrigeration cycles. An overview of novel single-stage and two-stage compression cycles utilizing a single or multiple ejectors is provided. First, the system setup, operational principles, description, and figures of the existing schemes are provided. Second, the main results, such as the coefficient of performance (COP), volumetric heating capacity and exergy destruction, are discussed. In conclusion, the paper presents a coherent summary of the current developments, future prospects, and the current knowledge gap. A plethora of research is present in developing theoretical systems with high efficiency. However, experimental tests for real-life implementations are limited. This review aims to provide the reader with an overview of recent theoretical and experimental studies. [ABSTRACT FROM AUTHOR]

The ternary transition metal boride Fe2AlB2 is a unique ferromagnetic "MAB" phase that demonstrates a sizable magnetocaloric effect near room temperature—a feature that renders this material suitable for magnetic heat pump devices (MHP), a promising alternative to conventional vapor compression technology. Here, we provide a comprehensive review of the material properties of Fe2AlB2 (magnetofunctional response, transport properties, and mechanical stability) and discuss alloy synthesis from the perspective of shaping these materials as porous active magnetic regenerators in MHPs. Salient aspects of the coupled magnetic and structural phase transitions are critically assessed to elucidate the fundamental origin of the functional response. The goal is to provide insight into strategies to tune the magnetofunctional response via elemental substitution and microstructure optimization. Finally, outstanding challenges that reduce the commercial viability of Fe2AlB2 are discussed, and opportunities for further developments in this field are identified. [ABSTRACT FROM AUTHOR]

The decarburization of heat and transport using electric vehicles (EVs) and heat pumps (HPs) needs an important investment in low-voltage (LV) networks. This article proposes an optimization approach to estimate the availability of headroom for domestic EV charging and optimization on LV networks under various penetrations of heat pumps. The proposed optimization approach is called dynamic differential annealed optimization (DDAO). The objective of the proposed approach is to maximize the hosting capability of low-voltage networks for EVs and HPs by optimizing the flexibility of EV charging. The DDAO is used to optimize different aspects of EV charging and LV networks. The DDAO approach is implemented in three steps: (a) HP headroom assessment, (b) EV optimization, and (c) validation. The performance of the proposed method is validated on a MATLAB platform and compared with the existing Binary Spring Search Algorithm (BSSA), Manta Ray Foraging Optimization Algorithm (MRFO), and Chaos Game Optimization methods. In comparison to the total prices of 3.5£ in BSSA, 4.5£ in MRFO, and 5.5£ in CGO, the proposed DDAO method achieves a lower total price of 3.2£. This suggests that the DDAO method is more cost-effective than the existing techniques. [ABSTRACT FROM AUTHOR]

The study was carried out to evaluate theoretically and in laboratory conditions the capacity of a hybrid heating and cooling system that sustainably uses thermal energy extracted from surface waters in order to decarbonize buildings located near water sources. The novelty of the research consists in the realization of two experimental systems, one for the rapid evaluation of the performance of the water–water heat pump heating system and one for the evaluation of the operating behavior of a cooling system with fan coil units. Starting with the heating and cooling demand, and the climatic and hydrological local characteristics, a hybrid system model for the heating and cooling of the analyzed building was established and implemented. The forecasted energy consumption and CO2 emissions for the operation of the new equipment were compared with the historical values of the old systems with which the building was equipped (thermal energy supply from the district heating and cooling system with an air conditioning unit). Also, the results were extrapolated for forecasting the energy potential of the surface waters. The study highlights a percentage reduction in annual energy consumption of 67.71% and CO2 emissions of 80.13% through the implementation of the hybrid system. [ABSTRACT FROM AUTHOR]

This feasibility study investigates extracting thermal energy from the Bedretto tunnel in the Swiss Alps, which benefits from subsurface heat flux and rock overburden insulation. Using the simulation software COMSOL Multiphysics, we created a numerical model of the tunnel environment to evaluate which medium between rock, air, and water serves as the most effective heat source. Our findings indicate that flowing water is the most effective heat source. Potential applications include distributing the water to nearby villages and storing remaining heat in the subsurface. Estimates indicate that the total extractable thermal energy ranges between 0.8 MWth and 1.5 MWth after reducing the water temperature to 4 °C via a heat pump. The study identifies the most suitable energy sourcing locations based on efficiency and investment costs. Circulating water to individual heat pumps in Bedretto, with the natural elevation difference, enables water transport without a pump. Cost analyses reveal that the investment in piping and heat pumps can be amortized within the equipment's lifespan with appropriate economic models. With the same initial investments, district heating systems are viable in villages with over 30 connections. The payback periods are 10 years for 60 connections, 4.5 years for 90 connections, and immediate for 200 connections. [ABSTRACT FROM AUTHOR]

Performance of available air-source heat pumps (ASHP) for buildings is extremely influenced by the outdoor air temperature (OAT). When OAT falls below –20 °C, especially in subarctic climate, most commercially available ASHPs lose their defined functionality. To address this issue, a novel cascade heat pump (CHP) is proposed that utilizes two natural (with zero global warming index) refrigerants: ammonia, aka R717, as the low stage (LS) refrigerant, and water, aka R718, as the high stage (HS) working fluid. The proposed system is equipped with two rotary vane compressors for LS and HS. To desuperheat the compressor discharge temperatures and increase the HS heating capacity, liquid refrigerant is injected into the chamber of both LS and HS compressors. The wet compression is thermodynamically modeled and validated against experimental data available in the literature. Optimum design parameters such as the maximum allowable temperatures during compression and the minimum vapor quality after injection are obtained where the COP is maximized. Total exergy destruction, number/location of injectors and the injected amounts are also investigated. The proposed CHP can deliver 6.35 kW heating load at 50 °C with a COP of 1.985 when OAT is –40 °C. From a broader perspective, the proposed CHP not only proves its efficacy in extremely cold subarctic climates but also emerges as a pivotal player in addressing the global warming issue. This is accomplished through a dual approach to decarbonization—firstly, by electrifying heating processes and secondly, by substituting phased-out refrigerants with environmentally friendly natural alternatives. [ABSTRACT FROM AUTHOR]

• A review dedicated to the state on compression high-temperature heat pump steam systems. • The refrigerant and compressor that can be used in compression high-temperature heat pump steam systems are reviewed. • Research trend and the main technical problems of compression high-temperature heat pump steam systems to be solved are proposed. • The progress in developing, manufacturing, and optimizing high-temperature, high-pressure ratio compressors is summarized. • The primary technique for lowering discharge temperature in water vapor compressors is indicated. Compression high-temperature heat pump steam system (HTHPSS) has higher energy efficiency than electric, coal-fired and gas boilers for steam production. The system efficiently recovers waste heat from the factory and the CO 2 emissions can be reduced depending on the driving electricity mix, which is in line with the carbon neutral energy saving and environmental protection development strategy. However, there are few reviews published in the existing literature that specifically address the status of research on HTHPSS. This work not only reviews the status of research on compression HTHPSS in two directions: increasing the efficiency of high-temperature heat pump (HTHP) and increasing the steam temperature, respectively, but also indicates the future development trend of HTHPSS. The key to the research of HTHP is the development of high-temperature refrigerant and high compression ratio compressors. In this work, the refrigerants that can be used in HTHP are reviewed. Natural refrigerants R718 show promise as HTHP refrigerants because they have zero ozone depletion potential (ODP), zero global warming potential (GWP) and a high critical temperature. In addition, the research status of high-temperature and high-pressure compressor with a focus on their design and strategies for reducing the discharge temperature of scroll, piston, and screw compressors. The future focus of research is to develop a high compression ratio for the compressor. Moreover, the three main water vapor compressors, centrifugal, Roots and screw compressors, are introduced respectively. Finally, according to the operational requirements of the compression HTHPSS, research trend and the technical problems to be solved are proposed. [ABSTRACT FROM AUTHOR]

• Two comparable high-temperature heat pumps at different scales are investigated. • Both heat pumps show similar COP trend lines depending on the temperature lift. • Differences in heat losses and heat transfer are related to volume-to-surface ratios. • Experimental data for a water-cooled compressor show promising results. • Analysis of over 200 data points shows the possibility of upscaling laboratory results. High-temperature heat pumps (HTHP) are crucial for decarbonizing district heating and industry. Hence, a reliable performance estimation considering effects of scaling is of interest for cost-efficient system integration. This study compares two laboratory HTHPs with the same refrigerant R1233zd(E). These systems have a similar plant design but a capacity scale factor of 3.2. The aim is to evaluate scale effects and make general valid statements about the challenges of upscaling laboratory test results. The analyses show that it is essential to distinguish between design effects like temperature differences at the pinch point or different heat exchanger surfaces and scale effects like relative heat losses and efficiencies of components and the system. At the component level, large surface reserves in the heat exchangers lead to 3–5 K smaller approach temperature differences in the lower capacity HTHP. At the system level, the relative heat losses are about 15 % higher than in the system with a larger capacity. The coefficient of performance of both HTHPs shows a similar trend as a function of the temperature lift from the heat source to the sink. Cross-referencing these performance results with over 200 data points from the literature, validated the possibility of upscaling. [ABSTRACT FROM AUTHOR]

A novel CO 2 air-source heat pump system (ASHPs) with a secondary throttling based on a single-stage compression was proposed to further improve the heating energy efficiency of electric vehicles (EVs) for heating in cold climates. The heating characteristics of the secondary throttling system (STS) and conventional throttling system (CTS) at different indoor air supply temperatures were compared. The STS performance characteristics were investigated under varying ambient temperature, outdoor air velocity, and exergy analysis was performed on the system and its components. A fitting correlation equation for optimal discharge pressure was obtained based on experimental data. The results demonstrate that implementing STS significantly reduces CO 2 ASHPs energy consumption (W com), enhances the coefficient of performance (COP), and reduces exergy destruction. When the indoor air supply temperature reaches 45 °C, using STS can result in an 8.1 % reduction in W com , a 9.4 % increase in COP, and a 6.1 % improvement in the exergy efficiency (Ex η) compared to that of CTS. Furthermore, the advantages of STS become more pronounced with higher indoor target air supply temperatures. As the ambient temperature decreases, the exergy efficiency of the STS reaching the target air supply temperature decreases. The velocity of outdoor air significantly affects the STS performance, and increasing outdoor air velocity can effectively enhance the Ex η of STS. The optimal discharge pressure fitting equation for the STS was obtained through multiple linear regression analysis. These findings can provide ideas for architectural optimization and design of CO 2 ASHPs for EVs, which are important for further improving system performance. [ABSTRACT FROM AUTHOR]

The performance of a magnetocaloric heat pump (MCHP) consisting of active magnetocaloric regenerators (AMR) of 12 layers of MnFePSi magnetocaloric materials (MCM) with a linear distribution of Curie temperatures was investigated using a 1D numerical model. The model predicted the heating power and coefficient of performance (COP) of the AMR for a fixed temperature span of 27 K, between 281 K and 308 K, and variable flow rate and AMR cycle frequency. A maximum applied magnetic field strength of 1.4 T was used. A well-insulated house with a maximum heating power demand of 3 kW (under quasi steady state conditions) was considered. Ambient temperature in The Netherlands was taken as a reference for the estimation of the seasonal heating power demand. Without optimizing the design of the AMR, the model predicts a maximum single-AMR heating power equal to 43.5 W when the AMR operates at 3 Hz and 3 L min-1, and a maximum COP equal to 5.8 when it operates at 1.5 Hz and 1 L min-1 Considering the maximum heating power of a single AMR, approximately 69 AMRs are needed to provide the design heating power demand of the house. It was found that it is possible to achieve an AMR seasonal COP of 5.6 by continuously adjusting the flow rate and frequency of operation of the MCHP along with the ON/OFF switching of some groups of AMRs in order to adjust the heating power of the MCHP to the heating power demand of the house. • MnFePSi is used for the setup of a 12-layer active magnetocaloric regenerator (AMR). • AMR heating power and COP are mapped against flow rate and frequency using a 1D model. • A part-load operating strategy is proposed for residential magnetocaloric heat pumps. • ON/OFF switching of AMR groups is used along with flow rate and frequency modulation. • A heating AMR seasonal COP of 5.6 is obtained under Dutch climate conditions. [ABSTRACT FROM AUTHOR]

This article introduces a modular simulation platform for assessing thermal energy storage (TES) integrated with air source heat pumps (ASHP). The Python platform is an open-source library that includes classes for modeling air-air and air-water heat pumps, TES devices, and the heating load of residential buildings. To validate the ASHP model, the study utilized experimental data obtained from a commercial heat pump evaluated at the National Renewable Energy Laboratory (NREL). The results indicate a mean deviation of 0.7% for COP across the operating range, with a maximum relative deviation of 12.6%. In terms of system heating capacity, the model had an average deviation of 4.3% compared to experimental results, with a maximum deviation of 8.2%. Three classes were implemented for modeling distinct types of TES devices: a generic TES based on energy balances, a sensible isothermal water tank, and a stratified water tank. Details of the mathematical models are provided, along with their respective strengths and limitations. An example is provided showcasing the integration of a residential 10 kWh thermal storage unit with an ASHP operating in Denver, CO. The comparison of two different discharge criteria for the TES unit highlights the importance of control strategies in the system performance. [ABSTRACT FROM AUTHOR]

Compared to heat pumps established in the building sector, high‐temperature heat pumps (HTHPs) suitable for industrial use still face challenges, not only from a mechanical engineering point of view but also regarding integration into existing processes. They need to supply larger amounts of heat at higher temperatures. The mere replacement of a gas boiler by an HTHP will rarely deliver an energy‐efficient solution. Instead, these units must often be tailored to the application and vice versa, making specifications a complex task. This paper intends to link thermodynamic and economic basics of HTHPs to the process engineering of the actual production process. It also ventures an outlook on the economic and regulatory boundary conditions in the EU as corner stones for a sustainable investment decision. [ABSTRACT FROM AUTHOR]