Search

High energy consumption and operating costs have affected the development of green and efficient granary warehouses. In order to promote energy saving and emission reduction in the reconstruction of granaries, this paper proposes a special solar photovoltaic-ground source heat pump cooling system for grain warehouses. The study investigates the feasibility and energy-saving effects of this combined system in grain warehouses, aiming to achieve "zero energy consumption" and "zero emissions" for green storage. Bungalow warehouses are typically single-story buildings widely used in grain reservoir, characterised by large roof area and spacious room between building rows. These features facilitate installing both underground heat exchangers and solar photovoltaic panels. Compared with residential buildings, adquate space can enable the solar photovoltaic-ground source heat pump system to integrate more well with warehouse buildings, and provide more cooling and power capacity. In summer, the electricity generated by photovoltaic panels is primarily consumed by the ground source heat pume for grain warehouse cooling. Then, the electricity is transmitted to living and office buildings in the grain reservoir, meeting the lighting requirements. Finally, excess power is sold to the State Grid. During other seasons when cooling is not required, the generated electricity first supplies the living and office buildings, and extra power is sold to the State Grid, too. Therefore, operating costs can be reduced through the surplus electricity sale. To maximize the combined advantages of solar and geothermal energy technologies in low-temperature grain storage, it is essential to conduct thorough research and design focused on the function and structure characteristics of warehouse buildings. This study aims to achieve deeper energy savings in storage application with current technologies. Simulation software was used to analyze the operation characteristics of the proposed system. Firstly, according to the actual size and working conditions of a grain warehouse, a simulation model for an air source heat pump system was established using TRNSYS software, which was verified with test data, and the the temperature response mechanism used in later simulation was obtained. Then, a TRNSYS simulation model for the solar photovoltaic-ground source heat pump cooling system was developed, considering the temperature and humidity requirements for low-temperature grain storage. System performance was simulated by this model over short and long-term periods, computing its operational characteristics. Finally, the cooling system was evaluated according to operational performance, such as photovoltaic adaptability, economic efficiency, energy savings, and environmental benefits. The results show that after oneyear operation, the system maximum COP is 4.76 and the minimum value is 3.3; after ten-year running, the maximum COP is 3.96 and the minimum is 3.07. In one-year operation, the soil temperature around underground heat exchangers increased by 0.65℃, and after ten years, it increased by 5.4 ℃. Underground thermal balance is an important factor for long time working performance. To avoid continuous soil temperature rise, the system should include a cooling tower into the equipment or use the ground source heat pump for space heating in the office and living buildings during winter. The ratio of system annual power generation to consumption is 192% to 270% for the warehouse and the investment payback period is 7.8 years. With ground source heat pump system, the standard coal consumption for cooling grain is 1.2 kgce/(t·a), compared to 2.93 kgce/(t·a) for the air source heat pump system, resulting in an energy saving rate of 59%. Additionally, harmful emissions are reduced by 3,841 t/a annually. These findings indicate that the solar photovoltaic-ground source heat pump cooling system is more suitable for warehouses than traditional grain cooling methods. This research can be expected to provide theoretical support and design references for developing more efficient granary cooling systems. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid technique for optimizing Combined Cooling, Heating, and Power (CCHP) systems integrating a diverse set of components including geothermal heat pumps, gas turbines, absorption chillers/heaters, and photovoltaic/thermal collectors, along with storage units like batteries and water tanks. The innovation lies in combining the Capuchin Search Algorithm (CapSA) with the Wild Horse Optimizer (WHO) to concurrently optimize primary energy savings, cost reductions, and carbon dioxide emissions. Parametric distributions are used in probabilistic strategies to resolve uncertainty in solar radiation and building load. CapSA optimizes the CCHP system’s design, while WHO enhances its performance. The effectiveness of the proposed strategy is demonstrated through implementation in MATLAB, where it achieves an average ACSR (Average Comprehensive Saving Rate) enhancement of 5.48%. This numerical result highlights a substantial improvement over existing methodologies, showcasing the superior performance of the hybrid optimization approach in enhancing energy efficiency and environmental sustainability of CCHP systems. [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.)

In this study, five drying methods (hot air drying [HD], light wave drying [LD], far infrared drying [FID], freeze drying [FD], and heat pump drying [HPD]) were applied to dry Sargassum fusiforme. The color, rehydration rate (RR), and volatile flavor substances of dried S. fusiforme were compared and analyzed, and the content, molecular weight (Mw), monosaccharide composition, and antioxidant activity of dried S. fusiforme crude polysaccharides (SFCPs) were analyzed. The results showed that S. fusiforme dried by different drying methods showed different colors. FD produced S. fusiforme with better RR (p < 0.05). The Mw of the SFCPs were 624.06, 534.86, 683.00, 1077.13, and 981.91 kDa, respectively, for HD, LD, FID, FD, and HPD. The Mw and DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical scavenging rates of SFCP‐FD were greater than those of the remaining four drying methods; however, the ABTS (2,2 ′‐azobis‐3‐ethylbenzothiazoline‐6‐sulfonic acid) and OH (hydroxyl) radical scavenging rates were highest in the SFCP‐HPD. GC‐IMS analysis showed that the drying method affected the content and composition of volatile flavor compounds. Principal component analysis (PCA) analysis indicated that the flavors of dried S. fusiforme were quite different from that of fresh S. fusiforme, and the flavors of HD, LD, and FID were similar, while the flavors of FD and HPD were similar. [ABSTRACT FROM AUTHOR]

This study investigates the usage of photovoltaic (PV) and thermal collectors separately to assist a heat pump for supplying domestic hot water (DHW). Usage of PV and thermal collectors together to assist a heat pump and experimentally validated simulation of an air source heat pump can be considered as novelty of this study. Firstly, experimental tests were performed in a climatic room to validate the developed simulation model. Four experimental parameters, namely the coefficient of performance of the air source heat pump, average tank temperature, and heat pump inlet and outlet temperatures have been used for the validation and the highest obtained deviation was 4.5%. Simulations were carried out by adding thermal collectors and photovoltaic panels in different combinations, with a maximum of three collectors to assist the heat pump that provides DHW. For scenarios with one and two solar components (PV or thermal), applying only thermal collectors was more efficient and economical for both with a payback of 3.9 years and 4.3 years, respectively. For the scenario with three solar components, although the system supported by one thermal and two photovoltaic collectors was the most efficient option, the system supported by three photovoltaic collectors was the most economical scenario with a payback period of 4.6 years. The study found that combining thermal and photovoltaic collectors can significantly reduce energy consumption for DHW. [ABSTRACT FROM AUTHOR]

This review aims to analyze recent advancements in heat pump dryers (HPDs) with a focus on improving energy efficiency and conservation in drying processes. The objective is to evaluate the components, structures, and refrigerants used in HPDs, examining their environmental impacts and system performance. The methodology includes a comprehensive comparison of various assisted HPD systems, such as infrared-, ultrasound-, and solar-assisted technologies, to assess their experimental benefits and limitations. By using key performance metrics, the paper evaluates the energy efficiencies of HPDs in comparison with traditional drying methods, discussing their applications across different industries. The study also explores the significance of integrating alternative energy sources to enhance the efficiency and economic viability of HPDs. Future research directions are proposed to further develop the technology for commercial use, emphasizing HPDs' potential to provide energy-efficient and high-quality drying solutions. In quantitative terms, the review notes that the coefficient of performance (COP) for HPDs ranges between 3.5 and 4.5, indicating a significant improvement over traditional drying methods. Specific moisture extraction rate (SMER) values for HPDs are reported to be between 0.8 and 1.2 kg kW−1 h−1, demonstrating superior efficiency in moisture removal. Additionally, specific energy consumption (SEC) for HPDs is found to be 0.5–0.7 kW h kg−1 of evaporated moisture, which is substantially lower compared to conventional dryers. These metrics underscore the energy-saving potential and enhanced performance of HPD technology. [ABSTRACT FROM AUTHOR]

Peltier cells are commonly used in low-power cooling applications, such as automotive refrigerators and electronics temperature regulation systems. These applications are typically low-energy in nature. There is currently a growing emphasis on energy conservation and waste heat utilization in the energy industry. This paper explores the possibility of improving the heating or cooling coefficient of performance (COP) of Peltier cells through intelligent serial and parallel connections. The purpose of this work is to raise the question of whether it would be possible to reconsider the concept of harnessing the "energy" potential of Peltier cells. The utilized model is in line with the current state of the art, and the case study is based on parameters measured on a commercially available Peltier cell. The resulting COP, when considering current materials, remains inferior to the COP of compressor-based heat pumps. For low-power devices, it can represent a technically and economically comparable solution. [ABSTRACT FROM AUTHOR]

The escalating utilisation of second homes has led to an extension in heating periods and, to a certain degree, renovations to elevate the standard, resulting in augmented energy and resource consumption. A comprehensive survey was conducted in Sweden, examining user patterns across different seasons, heating systems, and implemented energy efficiency measures. The results indicate that second homes are occupied for extended periods during the summer season and intermittently throughout the year. Over half of the second homes are heated even when unoccupied, with 12% maintaining a temperature above 16 °C. The predominant heating method is direct electricity (32.2%), followed by heat pumps (29.5%) and stoves (17.5%). A variety of renovations are undertaken, primarily to enhance the standard and technical performance, but also to implement energy efficiency measures such as window replacement, additional insulation, or heat pump installation. Based on the reported user and heating patterns, and the energy renovations carried out, the potential energy savings with different energy renovation strategies were estimated for the Swedish second home stock. The results show that though lowering the temperature when a second home is unoccupied emerges as the most efficient measure, both in terms of cost-effectiveness and climate impact, it needs to be complemented with intermittent heating or dehumidification to ensure that the relative humidity is below critical levels, to avoid the risk of damages caused by, for example, mould growth. Installing a heat pump is the second most energy- and cost-effective measure and has the advantage that the indoor temperature can be maintained at rather high levels. [ABSTRACT FROM AUTHOR]

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]

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]

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 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.)

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.)

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]

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]

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 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 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 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]

The integration of the active heat storage system utilizing multiple heat storage and release media for prefabricated solar greenhouses with flexible material wall (PGFMW) can solve the problem of "good thermal insulation and weak heat storage" in PGFMW. However, it is still unclear on the heat storage and exothermic properties of the multiple media in the combined heat storage system. This study aims to perform on a PGFMW that equipped with a combined "air source ground heat exchange-back wall water circulation (AGHE-WWC)" heat storage system. A systematic investigation was also made on the individual and combined heat storage and release properties. A series of experimental tests were conducted to calculate the energy transfer. The results indicated that the minimum temperature of indoor air at night time was maintained above 10℃, and the maximum difference in temperature between indoors and outdoors was 26.5 °C in winter. The primary heat storage medium was identified as the 0-50 cm soil layer of the cultivation area in the PGFMW. Furthermore, the heat storage capacity of the soil layer reached 706.30 MJ on sunny days, accounting for 63.5% of the total heat storage. The difference in temperature between the inlet and outlet of the underground heat exchange was up to 10.8 °C, which increased by 54.4% in the heat storage capacity of the soil layer. The water circulation was used to store the heat energy of 424.04 MJ on the day, which accounted for up to 45.1% of the total heat storage. Specifically, after cloudy days, the temperature of 8 m3 of water in the storage tank increased from 11 to 35℃ by water circulation over two sunny days. In order to evaluate the rate of heat storage and release for the system in combination and individually, an evaluation index called the heat storage and release efficiency ratio (HRE) was inducted to assess system performance. It was found that the maximum absolute value of the HRE for water circulation system was 1.62, which was 1.8 times than the soil HRE on the same day. It proved that the water circulation system releases heat more rapidly compared to the soil on cloudy days. In terms of the total heat, the soil was remained the primary source of indoor heat release on the consecutive cloudy days. In addition, the "AGHE-WWC" heat storage system was realized to sustain the heat demand for a total of three consecutive cloudy days. Meanwhile, the average heating coefficient of performance (COP) and the uderground heat exchange COP were 9.16 and 6.82, respectively. The combined COP of the "AGHE-WWC" heat storage system was 8.85, while the energy saving rate was as high as 60.26%, compared with the heat pump. The finding can provide a strong reference for heat storage and release in combined heat storage systems. [ABSTRACT FROM AUTHOR]

The study aims at investigating the impact of ultrasound enhancement on the water change and quality characteristics of dried carrots by heat pump drying (HPD). The results showed that ultrasound had obvious strengthening effect on the drying and dehydration process of HPD, but there was an attenuation effect of ultrasound in the propagation process of materials, and the magnetic resonance imaging results could visually demonstrate the change and migration of moisture inside carrot slices. Higher drying temperature and ultrasonic power could cause more micropores and higher content of polyphenols, flavonoids and niacin of carrot slices. Conversely, the elevated drying temperature reduced rehydration ratio. β-carotene content showed a trend of increasing first and then decreasing due to excessive temperature and ultrasonic power. Based on AHP-CRTITC method, the highest comprehensive score was attained at drying temperature of 60 °C and ultrasonic power of 80 W. Therefore, the reinforcement effect of ultrasound on HPD process could significantly enhance dehydration rate and improve product quality. [ABSTRACT FROM AUTHOR]

This research investigates a polyvalent heat pump that simultaneously produces hot and cold water and uses natural refrigerants. The novelty of using a 48 V direct current compressor driven by solar photovoltaic (PV) energy and the staged retrofitting improvements to this heat pump are discussed. Empirical testing has indicated that using a suction line heat exchanger yields a 30% improvement in the heating Coefficient of Performance (COP). Rising ambient temperatures could positively and negatively impact its heating and cooling performance, respectively. In addition, an average COP of 3.8 was obtained after a one-hour simultaneous mode operation, with the average hot tank temperature rising from 32.7 to 58.9°C and the average cold tank temperature dropping from 18 to 14.4°C. Being capable of operating the polyvalent heat pump under renewable energy sources and utilizing all its generated heating and cooling energy contributes further to the electrification and decarbonization of residential buildings. [ABSTRACT FROM AUTHOR]

The radiant systems come to the fore due to energy saving potential and good integration. The effect of different forms of cold surfaces on human thermal comfort is focused on its application. A novel natural convection-radiant evaporator for heat pumps was developed and its influence on thermal comfort was investigated. A numerical model of the chamber with the evaporator was established and verified with experimental results. Thermal comfort experiments were conducted in a climate chamber and the influence of its asymmetric and uneven cold radiation on the thermal comfort was investigated. Due to the limitation of PMV in uneven radiation situations, the revised predicted mean vote (RPMV) was proposed to assess the thermal comfort in asymmetric and uneven radiation environments based on experimental results. Based on RPMV, the influence of the surface area and temperature of the evaporator on thermal comfort was numerically analyzed. The results indicate that indoor air temperature and relative humidity, RPMV increase with the increase of plate temperature, but decrease with an increase in plate area. The most favourable indoor thermal comfort environment was obtained at an indoor air temperature of 28°C and relative humidity of 50%, which is 2°C higher than traditional air conditioning system. [ABSTRACT FROM AUTHOR]

Thermoacoustic air-to-water air source heat pumps (TAWASHP) are the eco-friendly, simple, compressor less, low cost and likely looking future substitute for the existing compressor-based heat pumps. In this work, the design optimization of the 1-kW TAWASHP with helium for the temperature difference of 15 to 70 K for pumping heat from the atmospheric air to water using the linear thermoacoustic concepts was discussed. The optimized design can fit for both cooling and water heating applications without wasting the heat rejection to the surrounding atmosphere, rather supplied to the insulated hot water tank. The optimized one-fourth wavelength resonator TAWASHP shows the coefficient of performance of 1.1 to 2.34. The theoretical results are validated with the DeltaEC software results, and the results are in concurrence with each other. The DeltaEC predicts the TAWASHP can supply 1.55 to 3.35 kW of heat to water, which is equivalent to 37.3 to 80.3 kWh of heat energy per day. [ABSTRACT FROM AUTHOR]

This article presents the performance estimation of a single-stage vapor adsorption system employing various carbon-based adsorbents with ethanol refrigerant, coupled with a small-scale biomass-based heating unit for space cooling, refrigeration, and heat-pumping applications. A detailed parametric investigation highlights the effects of operating temperatures, and heat exchanger to adsorbent mass ratio on specific cooling energy (SCE), coefficient of performance (COP), uptake efficiency (ηu), and mass of adsorbent to combustion fuel (mad/mcf) to identify the suitable adsorbent and sorption bed designs for each application. The numerical findings reveal that the flat-finned tube (FFT) adsorber outperforms traditional-finned tube (TFT) and tube & shell-type (T&S) adsorbers, achieving 19% and 30% higher COP, respectively, with biomass carbon-ethanol pair. The H2-treated Maxsorb-III shows the greatest optimal cooling COP (0.73), followed by the biomass-carbon (0.72) for refrigeration and space cooling. For heat pumping applications, biomass carbon-ethanol achieves the highest heat pumping COP (1.84) at a desorption temperature of 90°C, surpassing H2-treated Maxsorb-III. Further, the biomass-derived activated carbon requires the lowest amount of adsorbent per unit mass of combustion fuel in the biomass heating unit. The present thermodynamic analysis is a precursor for optimization of the potential heat-exchanger geometries and operating parameters, with the high-performance carbon adsorbents. [ABSTRACT FROM AUTHOR]

The present study investigates the incorporation of renewable rooftop photovoltaic systems in fully electrified residential buildings and estimates the zero-energy demand building potential in relation to the climatic data of Greece. Specifically, the aim of the analysis is to calculate the maximum possible number of stories and therefore the total building height for a complete transformation to zero-net-energy building. The energy analysis, which is conducted using the DesignBuilder software, focuses on single-floor up to seven-story buildings. The importance of the present work lies in the acknowledgment of the diversity of the Greek residential sector, the adherence to national energy policies, and the European goal of fully electrified buildings. The examined case studies are equipped with electrically driven air-to-air heat pumps serving the space heating and cooling demands and with an air-to-water heat pump covering the domestic hot water requirements. The investigated locations are the four main cities of Greece, Athens, Thessaloniki, Chania, and Kastoria, which represent the country's four climatic categories. The conducted analysis allows for the mapping of the zero-energy building potential for the climatic data of Greece, demonstrating the possibility of striking a positive building energy balance through the integration of on-site renewable energy sources and the production of necessary electrical energy. The novelty of the present work lies in the identification of a key factor, namely, the building height, which determines the feasibility of transforming multifamily buildings into zero-energy buildings. According to the analysis results, the critical number of stories is calculated at six for Chania, five for Athens, four for Thessaloniki, and two for Kastoria. Regarding a three-story residential building, the incorporation of a renewable photovoltaic system can result in an annual surplus electricity production of 13,741 kWh (Chania), 10,424 kWh (Athens), and 6931 kWh (Thessaloniki), and a corresponding coverage of 100% (Chania), 69.0% (Athens), 38.9% (Thessaloniki) and 0% (Kastoria). [ABSTRACT FROM AUTHOR]

Elastocaloric cooling technology has the prospect of becoming a commercialized green alternative to current vapor-compression technology, and the systematic characterization of the elastocaloric effect and microstructure has become increasingly significant for the optimization of elastocaloric coolers and heat pumps. In this work, a comprehensive elastocaloric effect characterization for a dog-bone shaped NiTi sheet with a thickness of 0.5 mm was performed for the application in a compact continuous rotating bending elastocaloric cooler. The elastocaloric effect was found to be nearly identical under Brayton-like and sinusoidal force-controlled cyclic tensile loadings. The maximum adiabatic temperature change values of 31 and 23 K were recorded in Brayton-like cyclic loadings under maximum applied stress of 600 and 400 MPa, respectively, with an applied strain rate of 0.1 s−1. During fatigue tests, large applied stress (>600 MPa) and high applied strain rates (>0.1 s−1) tended to result in premature failure of the NiTi sheet samples. In the continuous rotating bending elastocaloric cooler, the sheets generated a temperature span of 6 K between the copper heat sink and heat source. The results of this work provide a set of thermophysical property data for the elastocaloric solid refrigerant and insights for the optimization of structural and operational parameters in elastocaloric coolers and heat pumps. [ABSTRACT FROM AUTHOR]

The deteriorating thermal environment of tunnels and the increase in energy consumption of environmental control systems has become highlights in the subway field. In existing research related to analysis of subway tunnel thermal environments and thermal accumulation; there is no predictive law that accounts for thermal accumulation or the long-term change in subway tunnel thermal environments. In this study, a combination of simulations and experiments is used. First, the long-term evolution of tunnel thermal environments with and without thermal interference are predicted and analyzed. Then, the changes in the tunnel thermal environment after the use of capillary heat exchangers are explored. The research results indicate that the model of the system has high accuracy and reliability. When there is a capillary heat exchanger installed in the subway tunnel, the anti-seasonal heat storage characteristics of the system result in the tunnel temperature increasing significantly in summer and decreasing significantly in winter, with a small decrease in the average annual temperature. This study provides a theoretical reference for environment-based subway tunnel construction and the comprehensive utilization of tunnel waste heat. [ABSTRACT FROM AUTHOR]

There is an increasingly rich literature on the decarbonisation of heat and the evolution of heat networks. This paper investigates whether a novel fifth Generation District Heating and Cooling Network (5GDHC) could be retrofitted to an existing National Health Service (NHS) hospital campus for the purpose of heating and cooling. The building load was simulated and input into a custom-written script to carry out a series of parametric studies and optimise design options. The model was calibrated against site data available from hospital facilities management. The research found that it is feasible to use a 5GDHC consisting of a large single mass of water to utilise inter-seasonal thermal storage. A natural water resource such as an aquifer was not required. The model tested sizing options and found that larger thermal storage, heat pumps and chillers reduce operating costs and improve flexibility. The paper closes with a discussion of the practical factors in retrofitting 5GDHC networks to a densely occupied and highly constrained campus environment. The findings are novel in further describing the circumstances for which 5GDHC networks are suitable. [ABSTRACT FROM AUTHOR]

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system's power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day. [ABSTRACT FROM AUTHOR]

The forthcoming implementation of national policies towards hydrogen blending into the natural gas grid will affect the technical and economic parameters that must be taken into account in the design of building heating systems. This study evaluates the implications of using hydrogen-enriched natural gas (H2NG) blends in condensing boilers and Gas Adsorption Heat Pumps (GAHPs) in a residential building in Rome, Italy. The analysis considers several parameters, including non-renewable primary energy consumption, CO2 emissions, Levelized Cost of Heat (LCOH), and Carbon Abatement Cost (CAC). The results show that a 30% hydrogen blend achieves a primary energy consumption reduction of 12.05% and 11.19% in boilers and GAHPs, respectively. The presence of hydrogen in the mixture exerts a more pronounced influence on the reduction in fossil primary energy and CO2 emissions in condensing boilers, as it enhances combustion efficiency. The GAHP system turns out to be more cost-effective due to its higher efficiency. At current hydrogen costs, the LCOH of both technologies increases as the volume fraction of hydrogen increases. The forthcoming cost reduction in hydrogen will reduce the LCOH and the decarbonization cost for both technologies. At low hydrogen prices, the CAC for boilers is lower than for GAHPs; therefore, replacing boilers with other gas technologies rather than electric heat pumps increases the risk of creating stranded assets. In conclusion, blending hydrogen into the gas grid can be a useful policy to reduce emissions from the overall natural gas consumption during the process of end-use electrification, while stimulating the development of a hydrogen economy. [ABSTRACT FROM AUTHOR]

Achieving a zero-emission building heating sector requires numerous strategies and detailed energy planning, in order to identify the optimal decarbonisation pathway. This work aims to assess the impact of district heating expansion and the implementation of energy-saving measures on the decarbonisation of the Italian building stock by 2050, analysing their combined impact, reciprocal effects, and technical–economic implications on the entire national energy system. The scenarios have been implemented and simulated with the H2RES software, a long-term energy planning optimisation model, built for the Italian national energy system. Results indicate that it is possible to decarbonise the heating system in an efficient and cost-effective manner by the year 2040. Heat pumps represent the optimal technology at both centralised and decentralised levels. District heating expansion is a priority for the decarbonisation of the building stock, allowing us to reduce costs, exploit thermal storage systems and provide system flexibility. In the best scenario, 40% of the Italian heat demand can be supplied by fourth-generation district heating. Energy-saving measures can reduce heat demand and primary energy but at higher annual costs and with a significant increase in investment. The combined simulation of the strategies within an optimisation model of the entire energy system enables the accurate assessment of the real impact of the various measures, considering their reciprocal effects and technical–economic implications. [ABSTRACT FROM AUTHOR]

Thermoacoustic heat pumps are a promising heating technology that utilizes medium/low-grade heat to reduce reliance on electricity. This study proposes a single direct-coupled configuration for a thermoacoustic heat pump, aimed at minimizing system complexity and making it suitable for domestic applications. Numerical investigations were conducted under typical household heating conditions, including performance analysis, exergy loss evaluation, and axial distribution of key parameters. Results show that the proposed thermoacoustic heat pump achieves a heating capacity of 5.7 kW and a coefficient of performance of 1.4, with a heating temperature of 300 °C and a heat-sink temperature of 55 °C. A comparison with existing absorption heat pumps reveals favorable adaptability for large temperature lift applications. A case study conducted in Finland over an annual cycle analyzes the economic and environmental performance of the system, identifying two distinct modes based on the driving heat source: medium temperature (= 250 °C) and low temperature (< 250 °C), both of which exhibit favorable heating performance. When the thermoacoustic heat pump is driven by waste heat, energy savings of 20.1 MWh/year, emission reductions of 4143 kgCO2/year, and total environmental cost savings of 1629 €/year are obtained. These results demonstrate the potential of the proposed thermoacoustic heat pump as a cost-effective and environmentally friendly option for domestic building heating using medium/low-grade heat sources. [ABSTRACT FROM AUTHOR]

The traditional evaporator of water source heat pump system is easy to freeze when the water source temperature is too low in winter. A novel ice source heat pump system is proposed, which can use low temperature surface water to supply heat to buildings. One of the key problems for safe transportation is velocity range of ice slurry in ice outlet pipeline. In order to study the critical flow velocity of ice slurry in the pipe, an Euler model of horizontal straight pipe and 90° elbow pipe were established by Fluent software. The influence of five factors on the critical flow velocity of two kinds of pipes, including initial ice packing fraction, ice particle size, pipe diameter, length of straight pipe and radius curvature of elbow was studied. It found that the initial ice content should be controlled from 10% to 15%. The inlet flow rate was 20% higher than the critical flow rate under the most unfavorable condition. Ice particle size was less than 0.2 mm. The total length of ice discharge pipeline was less than 50 m. Curvature radius of the bend should be met the minimum requirements of the specification of the pipe used. [ABSTRACT FROM AUTHOR]