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The article describes design of a solar dryer with a heat pump, which is used to increase heat output of the unit twice to solve the problem of using environmentally clean sources of thermal energy for fruit drying. The authors of the research have developed methodology of substantiation of the solar dryer parameters, which is applied to design and justify the optimal technological modes and parameters of the heat carrier in the unit, to describe the heat transfer characteristics of the unit operation, to assess the impact of physical environmental parameters on technological indicators of the process. The novelty described in the article is developed design of a solar dryer with a heat pump and to substantiate its constructive and technological structure. The work supplies scientifically substantiated methodic recommendations on composing and forecasting a parametric series of solar dryers for the conditions of private households and farms, and grounds their design parameters. Designed solar dryer with a heat pump affects solving environmental problems of power engineering due to substitution of the electric and thermal energy by the one obtained from solar energy, and mitigation of social problems by creating new job places needed when producing, installing and exploiting such units. The obtained results can be used for designing and improving technical aspects of fruit drying, to increase technological and energy efficiency of the process. [ABSTRACT FROM AUTHOR]

Jordan is currently facing an energy crisis characterized by a heavy dependence on imported fossil fuels, prompting the nation to target a 50% share of renewable energy by 2030. This study introduces a novel approach by simulating hybrid solar-geothermal heat pump systems tailored to various Jordanian locations, assessing both their energy efficiency and economic feasibility. Unlike previous studies that focused solely on geothermal or solar technologies, this research uniquely combines these two renewable sources, offering a comprehensive evaluation across multiple climates. Key findings include the superior performance factors of vertical (4.0) and horizontal geothermal heat pumps (4.2) in Amman, compared to the air-to-water heat pump (3.5). Additionally, Aqaba station demonstrated an exceptional solar contribution, meeting 99.34% of heating demand, while Amman achieved 77.93%. Notably, Maan station provided the highest solar contribution for space heating at 6,902 kWh/year, and Amman airport station led in CO2 emission avoidance at 2,120.29 kg/year. The economic analysis revealed that while vertical heat pump systems were economically unviable with a negative NPV of -4,987.51 JD, horizontal and air-to-water systems showed promising NPVs of 5,734.27 JD and 8,428.46 JD, respectively, with payback periods of 9.44 and 6.5 years. Additionally, this study is the first to employ both the fuzzy Best–Worst Method (BWM) and Analytic Hierarchy Process (AHP) techniques to rank station suitability, identifying Maan station as the most optimal and Ghor El-Safi as the least. The results underscore the potential of hybrid solar-geothermal systems to significantly reduce energy consumption and CO2 emissions, despite initial financial barriers, and highlight the importance of further investment in geothermal technologies to enhance Jordan's energy security and reduce fossil fuel dependency. [ABSTRACT FROM AUTHOR]

A modified single-adsorber cycle for a gas-fired adsorption heat pump (GAHP) is described and analyzed through dynamic simulation with Modelica. The adsorption modules are based on the SAPO-34 / water working pair with parameters taken from a recent R&D project. A stratified storage integrated into the primary heat pump loop is employed for heat recovery of the adsorber as well as the EC heat exchanger (functioning both as an evaporator and condenser). A heating system of a stock multifamily residential building in Germany is assumed as the load to be covered by the heat pump. Representative load points according to VDI 4650-2 and DIN EN 12309-6 rules are considered. The hydraulic system design and implications of the storage integration on degrees of freedom during operation are discussed. The results show that, for a well-stratified storage, similar COP values to a dual-adsorber heat pump cycle based on the same adsorption module type are achievable. Possible additional benefits of the storage are discussed. [ABSTRACT FROM AUTHOR]

Background: The implementation of the EU climate and energy policy, along with changes in the legal environment, has led to a significant increase in energy prices in Poland. Consequently, energy expenditures are now a larger part of household budgets. These rising energy costs and the evolving legal landscape are compelling households to invest in energy-saving solutions and modify their energy consumption habits. This article aims to identify the activities of households in Poland regarding the rationalization of energy expenditures. It formulates the following research hypothesis: households invest in energy-saving appliances to rationalize energy expenditures and/or change their behaviors to reduce energy consumption. Methods: The paper is based on primary research conducted using an online questionnaire survey on a sample of 331 respondents in Poland in March and April 2023. Results: A classification tree algorithm was used to identify the level of investment activities and behavioral changes made by households to reduce energy expenditures. The authors found that low-income households and people who fear further energy price increases are the first of all to change their behaviors for more energy-efficient ones. Medium- and high-income households take investment measures. They replace household appliances with more energy-efficient ones and install heat pumps and photovoltaic panels. These investments are motivated by responsible consumption, environmental protection, cleanliness, and the ease of use of the appliances. [ABSTRACT FROM AUTHOR]

The electrification of residential heating systems, crucial for achieving net-zero emissions, poses significant challenges for low-voltage distribution networks. This study develops a simulation model to explore the integration of heat pumps within active building systems for community heating decarbonisation. The model optimises heat pump operations in conjunction with thermal energy storage units to reduce peak demand on low-voltage networks by using real-time measured electricity demand data and modelled heat demand data for 76 houses. The study employs an algorithm that adjusts thermal storage charging and discharging cycles to align with off-peak periods. Three scenarios were simulated: a baseline with unoptimised heat pumps, a fixed threshold model, and an active building model with daily optimised thresholds. The results demonstrate that the active building model achieves a 21% reduction in peak demand on the low-voltage substation compared to the baseline scenario; it also reduces the total electrical energy consumption by 12% and carbon emissions by 17%. The fixed threshold scenario shows a 16% improvement in peak demand reduction, but it also shows an increase in energy consumption and emissions. These findings highlight the potential of active buildings to enhance the efficiency and sustainability of residential energy systems, marking a significant step toward decarbonising residential heating while maintaining grid stability. [ABSTRACT FROM AUTHOR]

Vapor compression heat pump technology is a widely utilized method for energy conversion. Lubricating oil plays a crucial role in the heat pump system cycle by effectively reducing wear on the compressor's moving parts and preventing refrigerant leakage. However, it can also create an oil film in the heat exchange equipment, which increases thermal resistance and diminishes heat transfer efficiency. This study utilizes a vapor compression heat pump system test bench to investigate factors influencing the system's oil circulation rate, the two-phase flow patterns of refrigerant and lubricating oil, and the impact of oil circulation on system performance. The findings reveal that as the compressor speed increases, the oil circulation rate initially decreases before increasing again. Additionally, a decrease in the evaporator's heat load leads to a reduction in oil circulation at high temperatures, while it increases at low temperatures. Furthermore, increasing the opening of the electronic expansion valve results in a gradual decrease in the oil circulation rate, whereas an increase in the refrigerant charge correlates with a rise in the oil circulation rate. The oil return flow pattern can primarily be categorized into three states: slow oil return, oil film flow, and high-speed oil return. These patterns are closely related to the degree of superheat, with lower superheat levels intensifying oil return. [ABSTRACT FROM AUTHOR]

Heat pumping through thermoelectric devices has many advantages over traditional cooling. However, their current efficiency is a limiting factor in their implementation. In this paper, we approach the non-convex topology optimization of thermoelectrical elements for cooling applications through the method of moving asymptotes (MMA) to improve their cooling capabilities per watt usage. The optimization problem is defined for a given power budget, aiming for the minimum temperature with a known heat pumping need. The introduction of power as a constraint justifies the introduction of the voltage gradient across the thermocouple as a design variable to maintain the thermoelectrical device in its optimum power-to-heat extraction ratio. To better understand the convergence of this non-convex problem, we present a two-variable analytical thermoelectric optimization model. This example provides information on how to select the penalty parameters used to scale the three material coefficients involved in the problem to obtain lower objective values and better convergence using MMA. The analytical model shows the non-convexity of the problem and provides the recommendation to use penalization coefficients of the form p k = p σ > p α = 1 for the thermal conductivity, electrical conductivity, and Seebeck coefficients. We tested these penalization coefficients through optimizations of a model based on the 1MC10-031 commercial thermoelectric-cooler (TEC) using the finite element method (FEM). These penalization coefficients provided local minima without the need for volume constraints. With this procedure, we found designs that provided temperatures close to 10 degrees lower using 60% less semiconductor material volume compared to the initial design. [ABSTRACT FROM AUTHOR]

Electrocaloric (EC) cooling presents a promising approach to efficient and compact solid-state heat pumps. However, reported EC coolers have complex architectures and limited cooling temperature lift. In this work, we introduce a self-regenerative heat pump (SRHP) using a cascade of EC polymer film stacks, which have electrostrictive actuations in response to an electric field that are directed to realize efficient heat transfer, eliminating the need for additional transportive or regenerative mechanisms. The SRHP demonstrates a cooling of 8.8 kelvin below ambient temperature in 30 seconds and delivers a maximum specific cooling power of 1.52 watts per gram. The temperature lift of the SRHP is 14.2 kelvin. These results underscore the potential of the compact solid-state cooling mechanism to address the increasing need for localized thermal management. [ABSTRACT FROM AUTHOR]

CO2 is an environmentally friendly heat transfer fluid and has many advantages in thermal energy and power systems due to its peculiar thermal transport and physical properties. Supercritical CO2 (S-CO2) thermal energy conversion systems are promising for innovative technology in domestic and industrial applications including heat pump, air-conditioning, power generation, renewable energy systems, energy storage, thermal management, waste heat recovery and others. Both S-CO2 and transcritical CO2 thermodynamic cycles have been extensively investigated in order to improve the efficiencies of thermal and power systems and achieve net zero carbon emissions. This paper focuses on the progress and prospects for current research and technology development of S-CO2 thermal energy conversion systems and their applications including power generation, energy storage and waste heat recovery. First, the CO2 thermal transport and physical properties and benefits using CO2 as a heat transfer fluid in thermal energy and power systems are discussed. Then, classification of CO2 thermodynamic systems is presented. Next, S-CO2 for power generation, energy storage and waste heat recovery systems are presented. Finally, research needs of subcritical and supercritical CO2 heat transfer, fluid flow and heat exchangers for the development of various thermal energy and power systems are discussed. [ABSTRACT FROM AUTHOR]

• Installed demonstrator: high-temperature heat pump with mine thermal energy storage. • Proof of concept for a 2-stage 500 kW ammonia-butane heat pump that delivers 120°C. • Tests proved that the flooded mine is suitable for heated seasonal storage facility. • Heat pump factory tests with 70 K temperature lift showed high performance. • CO 2 emission reduction by means of a solar and geothermal integrated energy system. The research aims to prove that renewable energy sources in the heating sector can enable the energy transition towards European and German CO 2 reduction targets. To do so, at the premises of the Fraunhofer IEG Institute in Bochum a demonstrator for high-temperature heat pumps (HTHPs), coupled with seasonal high-temperature mine thermal energy storage (MTES), was developed. The goal is achieved by demonstrating the feasibility of the technology by connecting mine water present in a small flooded coal colliery (MTES) to solar parabolic trough collectors (SPTCs) and also to a HTHP system that serves the local district heating (DH) grid of Bochum south. The MTES, with an estimated water volume of approximately 20000 m3 is employed as seasonal storage for a 500 kW HTHP system that can reach a supply temperature of 120°C, as needed by the existing DH grid when the ambient temperature is lower or equal to -10°C. During the summer operation, the heat is injected into the MTES from the SPTCs to obtain a mine water temperature of 60°C; and in the winter operation, the heat is extracted through the HTHP until the mine water reaches the unheated temperature of 12°C at the end of the heating season. A literature review of the main components of the plant, the description of the installed system parts and performed tests are reported, along with the results of the successfully executed tests. [ABSTRACT FROM AUTHOR]

• Three parallel compressors more efficient than two variable speed compressors. • R452B versus R410A led to better efficiencies and compatibility at high ambient. • Reliable oil return of three parallel compressors having multiple capacity levels. • Three parallel centrifugal blowers led to improved air flow distribution. This study delineates a meticulous exploration of technologies to enhance the energy efficiency of rooftop air conditioning units, employing the DOE/ORNL heat pump design model for comprehensive engineering design and optimization. A baseline rooftop air conditioning unit, featuring a 13 ton (45.7 kW) cooling capacity and a 17.9 integrated energy efficiency ratio, served as the point of departure for substantive efficiency enhancements. Key modifications included the consolidation of two refrigerant circuits into one, integrating three parallel 2-stage (dual-speed) compressors, fan replacements with high-efficiency substitutes. Notably, a lower global warming potential refrigerant, R452B, was evaluated as a substitute for R-410A, demonstrating better performance in the lab prototype. The achieved measured integrated energy efficiency ratio of 21.4 in the lab prototype surpassed the baseline integrated energy efficiency ratio. Comparative evaluations between R410A and R452B indicated heightened efficiency with the latter, showcasing a lab-demonstrated integrated energy efficiency ratio of 22.4 at the rated capacity of 13.8 ton (48.5 kW) and 23.9 integrated energy efficiency ratio at the rated capacity of 10 ton (35.2 kW). This research underscores the successful development of a rigorous, energy efficient rooftop air conditioning unit prototype with noteworthy environmental and economic implications. [ABSTRACT FROM AUTHOR]

• The operating performances of a CASHP in LTS and HTS were tested. • Compressor speed plays opposite roles in LTS and HTS to affect the pressure ratio and COP. • Changes of the compressor speed in LTS failed to improve the COP of a CASHP unit. • Empirical models predicting COP in LTS and HTS were established. Previous studies on cascade air source heat pumps (CASHPs) mainly focused on overall performances, while impacts of the low temperature stage (LTS) and high temperature stage (HTS) on overall performances were paid less attention to. Therefore, operating performances of a CASHP in LTS and HTS were investigated in this paper, to provide a solution for the optimization of the CASHP. A CASHP unit with a variable speed compressor in LTS and a constant speed compressor in HTS was adopted, and its operating performances were investigated under 26 cases. Results showed that the pressure ratio and COP in LTS and HTS were affected differently by the compressor speed. Specifically, as the speed of the compressor in LTS increased from 30 rps to 90 rps, P rL increased by 151 % ∼ 178 %, and P rH reduced by 38 % ∼ 54 %. Meanwhile, COP in LTS reduced by 21 % ∼ 52 %, but the COP in HTS rose by 54 % ∼ 96 %. Besides, it was found that adjustments of the compressor speed in LTS could improve heating performances of the CASHP. However, when the ambient air temperature and the supply water temperature were consistent, COP changes of the CASHP were limited, only by 0.3 % ∼ 9 %. Furthermore, empirical models of the COP in LTS and HTS were established to predict the COP of the CASHP on different operating conditions. Results of this study were helpful in promoting the configurations and operation control optimization of CASHPs. [ABSTRACT FROM AUTHOR]

We study the adoption of air-source heat pumps for home heating. We estimate that 5% of already-built homes converted to heat pumps during 2010–20, while 22% of new homes built during this period chose heat pumps. New adoptions concentrate among rural households in the South. Conversions are more diffuse, covering urban and rural households in every region. Conversions are more prevalent in areas with mild winters and cheap electricity relative to other fuels but are less strongly associated with energy costs than adoptions in new homes. To better understand the distributional implications going forward, we calculate the annual energy-cost savings from switching to a heat pump for a large sample of US households based on their current heating fuels, climate, and local energy prices. We find massive variation, with low-income households in the Northeast and Appalachians benefiting the most. [ABSTRACT FROM AUTHOR]

The focus of this study is to optimize the exploration of biomass-driven multi-energy systems, which include combined heat, power, and gas generation. The objective is to enhance the thermal, environmental, and economic performance indicators of the system. The optimization objectives encompass the quantities of internal combustion engines and air source heat pumps, as well as the dimensions of tanks utilized for anaerobic fermentation. A mathematical model was developed to optimize multiple objectives for combined heat, power, and gas generation systems by employing multi-objective intelligent optimization algorithms. The validation and analysis were conducted using rural residences in Lanzhou, Gansu Province, China, as a case study. The sensitivity analysis of biomass gasification combined heat and power systems was conducted from both technical and cost perspectives, examining the dynamic impact characteristics on the outcomes of multi-objective optimization. The findings indicate that the annual energy-saving rate of the optimized combined generation system decreased from 3.62% to -6.78%, while the growth in carbon emissions reduction rate increased from 76.05 to 81.38%, and the annual cost-saving rate grew from 0.97 to 14.96%. The power generation efficiency of the cogeneration station and hydraulic retention time were found to have a significant impact on the multi-objective optimization results of the combined generation system among the technical parameters. The unit cost of anaerobic fermentation tanks had a more significant impact on the multi-objective optimization results in terms of cost parameters, compared to the price of biogas residue. [ABSTRACT FROM AUTHOR]

Combining mine exhaust waste heat with existing heat pump technology is a promising technical route to realise the efficient extraction and scientific use of low-grade waste heat resources in mines and to solve the problem of insufficient heat supply in remote mining areas. This study proposes a new type of mine-exhaust-air heat exchange coupled with heat-pump waste-heat-utilisation system based on deep enthalpy heat extraction. Using a mining area in Northwest China as a representative case, this study establishes a systematic exergy analytical model and a thermo-economic model. Through an in-depth analysis of the different evaporation temperatures and condensing temperatures, the system's energy efficiency ratio (COP) reaches its optimal performance, with the total exergy efficiency surpassing 90%. The minimum efficiency of the subsystem return air heat exchanger is 35%. The unit thermal costs of the mine exhaust air waste heat utilisation system and a conventional coal-fired boiler system are 0.1291 and 0.1573 million RMB/kW·h, respectively. This is a thermal economics cost saving of 21%. The studied system demonstrates great economic viability and the potential for energy saving throughout its life cycle. [ABSTRACT FROM AUTHOR]

Carbon capture and storage can reduce the carbon emission directly and effectively. Absorption carbon capture (ACC) is currently the most promising way to remove CO2 from coal-fired power plant, yet the main drawback is the excessive thermal energy consumption for the regeneration process. In this study, a new ACC system that utilizing the low-grade waste heat to generate steam has been proposed, in which system the steam is compressed to increase the saturation temperature to satisfy the thermal energy grade demand of the absorbent regeneration. Heat pump is introduced to increase the inlet pressure and enhance the energy and economic effect of vapor compression and R245fa is found suitable for the system. The vapor generating work can be controlled below 200 kWh t−1 when Twh is higher than 60°C, and COPvg can be higher than 3.5 for situations of Ttag,sat not exceeding 130°C. The energy performance and economic analysis of the proposed ACC system driven by the new vapor generation method is analyzed. Off-peak operation by ASS shows good economic effect, the operating cost for the regeneration process of carbon capture is only 69.70 CNY t−1 CO2 under the worst condition and far below the traditional heating method. The new heat supply method for carbon capture presents reasonable energy and economic performance, which is shown suitable for peak shifting of the power grid. [ABSTRACT FROM AUTHOR]

Passive ultra-low energy buildings represent an effective strategy for energy conservation and emission reduction within the global building industry. The prolonged and cold winters in severely cold regions of China necessitate substantial heating energy consumption. The study utilized a combination of overall surveys and long-term tracking surveys to evaluate the indoor environment and energy consumption in a passive office building situated in severely cold region under different heating modes over 2 years. The results show that the average temperature and indoor air quality (IAQ) can meet the standards at most moments. However, the average relative humidity tends to fall below the specified lower limit. Nevertheless, the Predicted Mean Vote (PMV) index suggests that the indoor environment provides a comfortable thermal experience for humans. The heat pump air conditioning (HPAC) system operation revealed that when the outdoor air temperature fell below −7°C, the coefficient of performance (COP) of the air source heat pump units would deteriorate. Implementing intermittent heating during the second year can reduce heating energy consumption by 13.4 kWh/(m2·a), resulting in 38.9% energy savings. These findings will serve as a valuable reference for the design and operation of heating systems in passive buildings in severely cold regions. [ABSTRACT FROM AUTHOR]

Atmospheric freeze drying (AFD) is a promising alternative to conventional vacuum freeze-drying (VFD), operating under atmospheric conditions with lower energy consumption, continuous processing, and cost-effectiveness, especially in cold climates. However, AFD faces challenges such as prolonged drying time, product shrinkage, and ice thawing. These issues are addressed through hybrid techniques incorporating thermal or mechanical energy to enhance drying efficiency. This review paper presentes recent advancements in AFD by examining its fundamental principles underlying the process and innovative approaches designed to improve its efficiency. The application of differential scanning calorimetry (DSC) and the development of state diagrams have been discussed as tools for analyzing thermal characteristics and designing efficient drying regimes. The review also explores the influence of process parameters such as drying temperature, air velocity, and sample characteristics on drying kinetics and product attributes, offering insights into optimal conditions. Hybrid approaches, including heat pumps, vortex tubes, expanders, ultrasonic and microwave assistance, adsorbent usage, and fluidization, have shown significant energy savings and product quality improvements. Finally, the predominant modeling approaches employed in AFD have been explored to provide a comprehensive understanding of drying kinetics. Despite advancements, ongoing research is needed to overcome technical barriers and extend AFD’s applicability across various industries. [ABSTRACT FROM AUTHOR]

A novel methanol steam reforming system is proposed to enhance the utilization efficiency of waste heat in hydrogen production from methanol. The system is integrated with a monoethanolamine carbon capture system and a two-stage compression heat pump system. In this integrated system, the high-temperature products of the methanol steam reforming system exchange heat with the feedstock and undergo gas-liquid separation. The low-temperature gas produced is pre-compressed and utilized for heating the feedstock. Furthermore, a two-stage heat pump uses the low-temperature lean solution from the carbon capture system as a heat source for feedstock heating. The analysis is conducted based on a hydrogen production capacity of 200 kg/h, revealing an enhanced energy and exergy efficiency of 5.4% and 3.5%, respectively, compared to the reference system. Additionally, waste heat utilization efficiency increases from 62.1% to 92.0%. The cost of hydrogen production is reduced from 3.089 $/kg to 2.054 $/kg, which is very close to the cost of hydrogen production without carbon capture. The exergoeconomic analysis indicates that the introduction of energy levels enhances the value of high-temperature steams, and the hydrogen production unit exergy of cost rate is elevated from 3.443 $/kWh to 4.411 $/kWh. The proposed system can readily harness low-grade waste heat and exhibits high thermodynamic efficiency, presenting a promising approach for low-energy-consumption methanol-hydrogen production. • A low-energy, low-carbon methanol-based hydrogen production system is introduced. • Waste heat utilization of the integrated system is enhanced from 62.1% to 92.0%. • The overall energy and exergy efficiencies of the system reach 86.7% and 77.3%, respectively. • Hydrogen production cost is reduced from 3.089 $/kg to 2.054 $/kg by recovering waste heat. [ABSTRACT FROM AUTHOR]

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We have designed a separation process of isobutyl alcohol (52.0 mol%) and isobutyl acetate (48.0 mol%) mixture using conventional extractive distillation (ED) and extractive dividing‐wall column (E‐DWC) with the solvent dimethyl sulfoxide (DMSO). The binary mixture exhibits a minimum boiling azeotrope that is sensitive to pressure. Thermodynamic analyses have shown that the vacuum pressures work better compared to the atmospheric pressure when DMSO is the solvent. Based on the separation with a purity of 99.9 mol%, the E‐DWC process has resulted in 9.6 % and 4.8 % reductions in the total annual cost and CO2 emission rates, respectively, in comparison to the conventional method. After further intensification using the heat pump technique, the E‐DWC process with the solvent DMSO has provided more than 40.0 % reduction in energy consumption compared to the ED systems studied in the literature using the solvents butyl propionate and dimethylformamide. [ABSTRACT FROM AUTHOR]

Introduction: In Switzerland, heating accounts for 70% of a building’s energy consumption, mostly fueled by fossil sources. Recently, cantonal regulations have mandated the use of renewable energy in heating, making heat pumps more significant. This study examines how public and private actors can create or transform a business ecosystem to facilitate heat pump adoption in multifamily houses and which business models, resources, and activities are most effective to support this transformation. Methods: We conducted a literature review and 13 semi-structured interviews with experts in heat pumps and contracting business models. The interviews were analyzed using an ecosystem framework. Results: Our findings revealed three primary barriers to the adoption of heat pumps in MFHs: technical challenges, lack of expertise, and regulatory issues. In terms of contracting business models, high transaction costs and customer acceptance are significant obstacles. Additionally, we discovered that in Switzerland, contracting is predominantly offered by public-oriented organizations with ready access to capital. Discussion: The study emphasizes the necessity for collaboration among various actors to facilitate the implementation of contracting solutions with the goal of accelerating the adoption of heat pumps in multifamily housing. Key activities include generating the necessary expertise and standardizing large heat pumps in MFHs, central government efforts to harmonize and facilitate HP regulations across cantons, as well as active communication and sensitization of building owners and users. [ABSTRACT FROM AUTHOR]

According to extant Italian legislation implementing the Renewable Energy Directive, the mandatory renewable quota for a new building is 60% referring to a single service (e.g., heating during winter) or to multiple services (e.g., heating during winter and air conditioning during summer), depending on which services are actually present. The obligation to satisfy this minimum value often leads heating and ventilation plant designers to provide heat pump systems in industrial buildings, typically air/water or direct expansion type coupled with air terminals (air heaters or ventilation units) or radiant floors. The question is: Is this always the most advantageous option for industrial buildings? A typical industrial building was modeled by Trnsys® in two different climates. Based on the calculated thermal heating loads, the condensing radiant tubes and heat pump coupled with the air heaters systems were analyzed through dynamic simulation, evaluating their performance from an energy, environmental impact, and economic point of view. The analysis carried out revealed that a heat pump system is not always the most advantageous solution depending on the climate, the characteristics of the building (less or more thermal insulation, which corresponds to existing buildings rather than new ones), and the size of the photovoltaics system eventually installed on the roof. [ABSTRACT FROM AUTHOR]

Waste incineration has become the main treatment method for urban household waste, and it can produce a large amount of electricity. The efficiency of waste incineration plants is reduced due to the large amount of waste heat carried away by the flue gas. Recycling and utilizing the waste heat from flue gas are important in improving the economic benefits of waste incineration, which is necessary for energy conservation and emission reduction. Based on the principle of cascade waste heat recovery from waste incineration flue gas whilst considering system safety and efficiency, this study proposed a new combination cascade waste heat recovery system consisting of a Rankine cycle, an organic Rankine cycle and a heat pump cycle. Thermodynamic and economic analyses of the combined system were conducted in detail. The results indicated that the energy efficiency of the combined system could reach up to 73%. The maximum net present value of the system was million USD 1.59 million, and the dynamic investment payback period was about 6.5 years. The isentropic efficiency of the combined system's pumps and turbines had a significant impact on the system's performance. A higher isentropic efficiency resulted in better system performance. The exergy analysis showed that the evaporator of the heat pump system had the highest irreversible loss. [ABSTRACT FROM AUTHOR]

PV technology has become widespread in the Netherlands, reaching a cumulative installed capacity of 22.4 GWp in 2023 and ranking second in the world for solar PV per capita at 1268 W/capita. Despite this growth, there is an inherent discrepancy between energy supply and demand during the day. While the netting system in the Netherlands can currently negate the economic drawbacks of this discrepancy, grid congestion and imbalanced electricity prices show that improvements are highly desirable for the sustainability of electricity grids. This research analyzes the effectiveness of a Power-to-Domestic-Hot-Water (P2DHW) system at improving the utilization of excess PV electricity in Dutch households and compares it to similar technologies. The results show that the example P2DHW system, the WaterAccu, compares favorably as a low cost and flexible solution. In particular, for twelve different households differing in size (1–6 occupants), PV capacity (2.4–8 kWp), and size of hot water storage boiler (50–300 L), it is shown that the total economic benefits for the period 2024–2032 vary from −€13 to €3055, assuming the current net metering scheme is abolished in 2027. Only for large households with low PV capacity are the benefits a little negative. Based on a multi-criteria analysis, it is found that the WaterAccu is the cheapest option compared to other storage options, such as a home battery, a heat pump boiler, and a solar boiler. A sensitivity study demonstrated that these results are overall robust. Furthermore, the WaterAccu has a positive societal impact owing to its peak shaving potential. Further research should focus on the potential of the technology to decrease grid congestion when implemented on a neighborhood scale. [ABSTRACT FROM AUTHOR]

This article presents an example of the joint use of a compressor heat pump that uses propane as a natural, ecological thermodynamic medium and a phase heat accumulator that uses paraffin as a medium. Special attention has been paid to the solidification process of the phase change material, and a simple theoretical model of the solidification of this material has been proposed. Thermodynamic balance calculations were carried out for the compressor heat pump and the phase heat accumulator. This paper presents a theoretical analysis of two examples of heating using a compressor heat pump, implementing the Linde cycle for the refrigerant R290 (propane): high-temperature heating at a temperature of 80 °C and low-temperature (surface) heating at a temperature of 60 °C, with the same unit heat output of 0.376 kW taken from the lower-temperature heat source of each evaporator. This heat is generated by the solidification of the PCM. The compressor power is 77 W in the first case and 40 W in the second. The energy efficiency coefficients of the compressor heat pump for the proposed combination of a phase heat accumulator and compressor heat pump are 5.98 and 10.40. The joint use of a heat accumulator and a heat pump presented in this paper can be used in applications for the heating of domestic water or water for space heating. [ABSTRACT FROM AUTHOR]

Large scale heat pumps (LSHP) have seen a rapid proliferation in recent years, with projects and initiatives aimed at integrating electrically driven LSHP into existing district heating networks (DHN). The financial advantages have driven most LSHP installations to be powered by electricity generated by on-site cogeneration (CHP), given CHP's dominant role in DHN. This LSHP + CHP combination poses the question, to what extent ecological improvements, measured as a reduction in specific CO2 emissions through LSHP operation can be achieved, contingent on the source of electricity and heat source employed. In this paper, the LSHP + CHP combination was generally analysed under usage of exergy analysis and a 2nd law derived method is presented. This method allows to evaluate the magnitude of CO2 reduction through LSHP operation across all common heat sources in 1st to 4th generation DHNs in conjunction with CHP. Results show, that in LSHP + CHP combination, heat from LSHP using either of the 2 heat sources ambient air or surfaced water, inevitably comes with higher specific CO2 emissions over the CHP heat. Only when using a sufficiently hot and emissions-free heat source, the LSHP heat from a LSHP + CHP combination can yield to an annual best case of half the CO2 emissions of the CHP. Importantly, the choice of power source has a far more significant impact, as LSHP powered by electricity from renewable energy sources achieve more than an eight-fold reduction in emissions compared to the LSHP + CHP combination. Therefore, power consumption with sufficiently low specific CO2 emissions out of external source is imperative to fully realize the ecological benefit of LSHP in DHN, underlining that the successful heat transition through LSHP relies heavily on the transformation of the electricity supply. Highlights: Based on the 2nd law a methodology is derived around exergy analysis, that enables a universal assessment of the ecological benefit of LSHP powered by CHP (Chapter 3). Graphs to determine every possible combination are presented (Chapter 4). Results are drawn for the most common CHP & LSHP including the most common types of heat source to grasp the scope of the discussed problematic. Ecological impact of LSHP in DHN are shown for comparison for most common types of CHP and LSHP- heat sources. [ABSTRACT FROM AUTHOR]

Aiming at the problem of excessive energy consumption in the thermal regeneration system of a rectisol process in a certain petrochemical engineering company, process improvement is carried out. A closed heat pump distillation model was proposed, using NRTL thermodynamic model with annual total cost and thermodynamic efficiency as objective functions. Process parameters were optimized and their economic and environmental benefits were analyzed under different compression ratios. The research results show that closed heat pump distillation can effectively reduce the use of superheated steam and condensate when the compression ratio is 1.8, and the total energy consumption is reduced by 62.71% . When the investment payback period are 5 years and 8 years, annual total cost is reduced by 15.64% and 32.79%, respectively. The thermodynamic efficiency has been improved from the original 8.78% to 20.96%, which has excellent economic and environ-mental benefits, and the results of the study are expected to provide guidance for the development and design of advanced heat pump distillation technology. [ABSTRACT FROM AUTHOR]

Methods and instrumentation for measuring grout quality in heat pump boreholes, including the measurement of groundwater flow through boreholes outside partly grouted borehole exchanger pipes, have been developed in the Czech Republic. A Semtex charge has also been developed to repair rock massifs, which reliably disconnects borehole exchanger pipes without severely harming the surrounding rock environment or buildings. The resulting hole can then be used for regrouting, thus preventing undesirable vertical water flow through the borehole. [ABSTRACT FROM AUTHOR]

Nowadays, the use of hybrid systems has become very common all over the world. In this study, the aim is to minimize the use of grid energy to provide heating and cooling energy with the help of a hybrid heat pump equipped with a flat solar collector, phase change material (PCM), and photovoltaic (PV) panels. To achieve the best results, a numerical dynamic model consisting of different solar PV panels in three models, batteries, inverters, and hybrid heat pump along with collector and PCM has been modeled by solving Engineering Equation Solver (EES) and TRNSYS software. According to the proposed scenarios, multi‐objective optimization has been done to simultaneously improve the study answers in several sections by multi‐objective particle swarm optimization algorithm with MATLAB software. Also, economic and environmental optimization is also presented separately for comparing and reviewing solutions. The results of multi‐objective optimization show that the amount of lifecycle cost (LCC) when using polycrystalline panel is 21.26% lower than monocrystalline panel and 38.71% higher than thin film panel. As a result, according to the specific conditions and attitude, you can choose the desired system. Also, in the economic optimization, it was found that the best system is related to the polycrystalline panel, the volume of PCM used in the system is equal to 1 m3 , the number of panels used is 18, and the minimum amount of LCC is $3929.08. [ABSTRACT FROM AUTHOR]

Drying has been widely used to provide a longer shelf life for various agricultural products. The moisture content can be reduced to prevent the spoilage of harvested agricultural products, in order to inhibit the growth of bacteria, yeasts, and molds. Among them, the drying system of solar-assisted air source heat pumps has drawn much attention in recent years, due to excellent energy saving and high dried quality of products. However, solar energy can be badly wasted, when the water tank temperature cannot meet the drying requirement, because of the high drying temperature during the middle and last drying stage. In this study, a solar-assisted multi-heat source heat pump (SMSHP) drying system was proposed to incorporate a watersource evaporator into the existing solar-assisted air source heat pump drying system, in order to improve the economic, and environmental benefit and the utilization rate. The fuzzy analytic hierarchy process was used to develop the optimization model of the SMSHP drying system. The optimization variables were selected as the collector inclination Angle, collector area, water tank volume, heat pump power, water pump flow rate, and airflow rate. The economy, system performance, and energy efficiency were chosen as the optimization objectives of the model. After that, the multi-objective optimization function of the SMSHP drying system was established to obtain a total of 25 groups of optimal combinations after the orthogonal test. Moreover, the simulation model of the SMSHP drying system was developed using the TRNSYS software. The accuracy of the model was verified, according to the experimental platform. Then the 25 groups of optimal combination parameters were introduced into the TRNSYS simulation model of the SMSHP drying system. The optimal parameter group was obtained with the highest system performance. Finally, the optimal and original parameter sets were compared and analyzed to verify the practicability and reliability of the model. The results showed that only 20 groups of 25 optimization parameters met the requirements of the drying process. The relative humidity of the air in the drying room was too high to meet the system requirements in the rest 5 groups. The economy, system performance, and energy efficiency were compared on the 25 groups' optimization. The optimization objective function of the 10th group was the lowest, indicating the optimal objective function. In addition, the TRNSYS simulation also showed that the optimal combination of parameters met the requirement of the drying process. The optimization parameter group 10 was the optimal one. The optimal parameters were obtained: the collector inclination angle was 35 °, the collector area was 40 m², the water tank volume was 1.5 m³, the heat pump power was 10 kW, the water pump flow rate was 2700 kg/h, and the airflow rate was 3500 m³ /h. Compared with the TRNSYS simulation of the original and the optimal parameters, the cost of the SMSHP drying system was reduced by 4.78%, whereas, the system performance and energy saving were improved by 17.08%, and 9.41%, respectively. All indicators were comprehensively improved by 6.27%. The multi-objective optimization of the solar multi-heat source heat pump drying system was carried out using a fuzzy analytic hierarchy process and TRNSYS simulation analysis. The finding has an important guiding significance to improve the performance of solar combined heat pump drying systems. [ABSTRACT FROM AUTHOR]

Ground heat pump systems (GHPSs) are esteemed for their high efficiency within renewable energy technologies, providing effective solutions for heating and cooling requirements. These GHPSs operate by utilizing the relatively constant temperature of the Earth's subsurface as a thermal source or sink. This feature allows them to perform greater energy transfer than traditional heating and cooling systems (i.e., heating, ventilation, and air conditioning (HVAC)). The GHPSs represent a sustainable and cost-effective temperature-regulating solution in diverse applications. The ground heat exchanger (GHE) technology is well known, with extensive research and development conducted in recent decades significantly advancing its applications. Improving GHE performance factors is vital for enhancing heat transfer efficiency and overall GHPS performance. Therefore, this paper provides a comprehensive review of research on various factors affecting GHE performance, such as soil thermal properties, backfill material properties, borehole depth, spacing, U-tube pipe properties, and heat carrier fluid type and velocity. It also discusses their impact on heat transfer efficiency and proposes optimal solutions for improving GHE performance. [ABSTRACT FROM AUTHOR]

It is now widely confirmed by scientific evidence that greenhouse gas emissions must be reduced to counteract the effects of global warming. The production of heat for industrial purposes is responsible for 36.8% of world energy-related emissions due to the widespread use of fossil fuels. Heat pumps are a key technology in the transition towards more sustainable industrial processes. In this paper, a systematic review of the literature produced in the last 5 years in international journals regarding the integration of heat pumps in industrial processes is presented. Firstly, papers presenting innovative configurations for high temperature heat pumps (HTHP), i.e., heat pumps delivering temperatures in the range between 100 °C and 200 °C, suitable for many industrial processes but still under development, are reviewed. Then, papers reporting innovative solutions for the integration of heat pumps in specific industrial processes and sectors (e.g., distillation, drying, desalination, etc.) are analyzed. Finally, the literature about alternative low-GWP refrigerants for industrial heat pumps, both pure compounds and mixtures, is described. It is concluded that many progresses have been realized in the last 5 years (2020–2024) regarding the identification of innovative heat pumps for industrial applications, but further research is certainly required. [ABSTRACT FROM AUTHOR]

The uptake of low-carbon domestic heating systems is a significant strategy towards global targets of reducing greenhouse emissions and mitigating climate change. Pre-1900 hard-to-treat houses will still be existing in the next 25 years, and they have the greatest potential for improved energy-efficiency. This study investigates the potential of fabric retrofit to prepare an older, hard-to-treat house type for heat pump use. The house type was modelled in DesignBuilder and validated using the Ulster University test house. The wall, loft and floor insulation, as well as glazing upgrades can yield up to 50% reduction in heating demand for a hard-to-treat house type, thereby preparing it for heat pump installation. Additionally, upgrading insulation and glazing in line with the current building standards was cost-effective, with a net present value of approximately GBP 12,000. [ABSTRACT FROM AUTHOR]

A photovoltaic thermal panel (PV/T) is an integrated module that harnesses both photovoltaic and solar thermal technologies to convert solar energy into electricity and heat, thereby enhancing overall energy efficiency. This paper aims to explore the suitability of PV/T solar heat pump systems across various climate zones and assess their potential for widespread application. By analyzing the operating principles of an indirect expansion PV/T solar heat pump system in conjunction with the climate characteristics of different regions, MATLAB R2019b/Simulink software was employed to evaluate the photoelectric performance of PV and PV/T systems in representative cities across five distinct climate zones in China during typical winter days. Key metrics, such as power generation, hot water storage tank temperature, indoor temperature, and system COP, were chosen to assess the heating performance of the PV/T solar heat pump system. The findings indicate that the winter ambient temperature significantly affects the photoelectric efficiency of both the PV and PV/T systems. While higher latitudes with lower ambient temperatures yield greater photoelectric efficiency, the southern regions exhibit higher power generation during winter. The winter heating effectiveness of the PV/T solar heat pump system is mainly influenced by indoor and water tank temperatures, with Harbin's system performing the poorest and failing to meet heating demands, whereas Nanjing's system shows the best results. [ABSTRACT FROM AUTHOR]

The accurate optimisation of absorption chillers is often impeded by idealised models that overlook system interactions and machine complexities. This study introduces a validated mathematical description for predicting the primary indicators of non-idealised absorption chillers, accounting for factors such as the electrical work of the Solution Circulation Pump, entropy changes within the refrigerant cycle, and exergy losses. Validation against 13 years of data (2008–2021) from the University of Debrecen's absorption chiller indicated close agreement, with deviations within acceptable limits. The use of a solution heat exchanger shifted cooling indicators towards their minima. Sensitivity analyses indicated that a 2.5% reduction in condenser temperature increased COP by 41.3% and Cooling Exergetic Efficiency by 15.5%, while a 2.5% reduction in the Heat Fraction Factor improved both by 34%. Adjusting absorber temperature and Heat Fraction Factor down by 2.5%, alongside a 2.5% rise in generator temperature, resulted in a 100.8% increase in COP and a 52.8% boost in Cooling Exergetic Efficiency. These insights provide a solid foundation for future optimisation strategies in real-life absorption chiller systems. [ABSTRACT FROM AUTHOR]

The performance of heat pump systems for heating and cooling heavily relies on the thermal conditions of their reservoirs. This study introduces a novel thermal reservoir, detailing a 2017 project where the Municipality of Stavanger installed a heat exchanger system on the wall of a main wastewater tunnel beneath the city center. It provides a comprehensive account of the system's design, installation, and performance, and presents an Artificial Neural Network (ANN) model that predicts heat pump capacity, electricity consumption, and outlet temperature across seasonal variations in wastewater temperatures. By integrating domain knowledge with the ANN, this study demonstrates the model's capability to detect anomalies in heat pump operations effectively. The network also confirms the consistent performance of the heat exchangers from 2020 to 2024, indicating minimal fouling impacts. This study establishes wastewater heat exchangers as a safe, effective, and virtually maintenance-free solution for heat extraction and rejection. [ABSTRACT FROM AUTHOR]

Integration of heat pumps combined with thermal energy storage provides a key pathway to decarbonizing the energy supply in the industry when the processes are not operated continuously. Yet, this integration of such novel systems introduces control challenges due to added dependencies between different process streams. This work investigates the control problem of heat pumps coupled to stratified thermal energy storage that is integrated into non-continuous industrial processes. A two-layer control strategy is proposed, where, in the higher level, a model predictive controller is developed for energy management using a linear model of the non-linear process. The resulting optimization problem is a mixed integer quadratic program. The low-level control layer is defined with standard industry controllers. The overall system is tested using a dynamic simulation model for the entire process, demonstrating its performance in three different cases. The control strategy optimizes heat recovery while ensuring system operability. The study demonstrates successful disturbance rejection and cold starts, wherein 100% of the targeted heat recovery can be confirmed under nominal conditions. Further evaluation in laboratory or field trials is recommended, and alternative, yet-to-be-defined, control concepts may be compared to the proposed approach. [ABSTRACT FROM AUTHOR]

The energy sector in Poland is primarily based on fossil fuels, mainly coal. Hard coal mining is one of the most important industries in Poland. Hard coal deposits in Poland are found in three basins, but mining is currently carried out in the Upper Silesian Coal Basin (USCB) and the Lublin Coal Basin (LCB). The Upper Silesian Coal Basin is Poland's central hard coal basin, with the most significant coal production extending across Poland and the Czech Republic. Approximately 80% of proven hard coal resources in Poland are found in the Upper Silesian Coal Basin (USCB). There is a tremendous amount of water in active and abandoned hard coal mines, which must be drained daily. Relatively high temperatures characterize mine water. This study analyzed the geological and hydrogeological conditions of the Upper Silesian Coal Basin and determined the potential for the use of mine waters for energy purposes. Depending on the location of the mine, the volume of mine water inflow ranges from 1 to 60 m3/min. The temperature of the pumped water is between 13 and 25 °C. In Poland, several such pilot installations have already been created; it is worth taking a closer look at the following examples. Heat recovery from mine drainage water can significantly reduce atmospheric emissions, which is particularly important in mining areas affected by low emissions. Therefore, Poland must raise the issue of using mined water for energy purposes, especially when making decisions related to decommissioning mines and developing post-mining areas. [ABSTRACT FROM AUTHOR]

BACKGROUND: Goji berries, renowned for their nutritional benefits, are traditionally dried to extend shelf life and preserve quality. However, conventional drying methods often result in uneven drying, color loss and reduced rehydration capacity. This study investigates an innovative hybrid strategy combining ultrasonic–ethyl oleate (US+AEEO) pretreatment with heat pump drying (HPD) to enhance the drying process of Goji berries. RESULTS: Fresh Goji berries underwent US+AEEO pretreatment, which significantly disrupted the waxy layer, enhancing drying efficiency and water infiltration during rehydration. Compared to freeze drying (FD), HPD combined with US+AEEO pretreatment resulted in higher retention of total polyphenol content (TPC) and total flavonoid content (TFC) in the Goji soaking soup. Specifically, the HPD‐US+AEEO samples exhibited the highest TPC and TFC levels, significantly outperforming FD samples. Additionally, the DPPH and ABTS antioxidant assays demonstrated higher scavenging activities in HPD‐US+AEEO samples. The rehydration kinetics revealed that HPD samples had a superior rehydration rate and final moisture content compared to FD samples. Low‐field nuclear magnetic resonance and magnetic resonance imaging analyses confirmed enhanced water distribution and higher mobility in HPD‐US+AEEO samples. Scanning electron microscopy indicated a more porous structure in US+AEEO‐treated samples, facilitating better water absorption and functional component retention. CONCLUSION: The combination of US+AEEO pretreatment with HPD significantly improves the drying process of Goji berries, enhancing nutrient retention, color preservation and rehydration properties. This innovative drying method offers a promising solution for producing high‐quality dried Goji berries, benefiting both the food industry and health‐conscious consumers. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Confluent, a company based in Scottsdale, Arizona, has announced a partnership with ATI to invest over $50 million in expanding ATI's Nitinol melt and materials conversion infrastructure. This investment aims to meet the growing demand for medical Nitinol in various device markets. Furukawa Electric in Japan has announced the reorganization of its metal wire business to maximize synergy effects and increase corporate value. Liebherr-Aerospace in Germany has inaugurated a new building for surface treatment, equipped with state-of-the-art technology for coating processes. NEOTech, a leading provider of electronic manufacturing services, has acquired advanced 3D Computed Tomography equipment to enhance its process validation and failure analysis capabilities. Finally, Oerlikon has established an advanced coating technology center in New York to accelerate the development of high-temperature materials and coatings for the aerospace and gas turbine industries. [Extracted from the article]

Although water heating accounts for 14% of residential electricity usage, the impacts of different water-heating technologies on greenhouse gas emissions are poorly quantified. This article compares carbon emissions from three water-heating technologies—including electric-resistance water heaters (ERWHs), heat-pump water heaters (HPWHs), and gas-fired boilers—by combining high-frequency measurements with physically based models. Models based on heat transfer principles are forced with measured hot-water demands from multi-unit residential buildings and then paired with spatially explicit marginal emissions data to compute carbon intensities. A technology warming potential analysis is then conducted to assess impacts over a 100-year period accounting for both site and source emissions. The use of real-world data at high temporal resolution reveals variations in emissions that are overlooked by studies that use precomputed factors. While, on average, ERWHs emit 1.9–2.2 times and 3.8–4.1 times more than gas-fired boilers and HPWHs, respectively, relative performance varies by season. Estimates of carbon emissions obtained using high-frequency data are found to be 8.9–9.6% higher than those obtained using average emissions factors, owing to alignment between marginal emissions and water demand peaks. These observations are discussed in the context of recent policy changes affecting water-heating technologies. [ABSTRACT FROM AUTHOR]

Refrigerants are a critical component of air conditioning and heat pump systems, but their high global warming potential has led to increasing concerns about their environmental impact. This research quantifies leakage from Schrader valves commonly used in air conditioning equipment. These valves serve as access points for refrigerant circuits and are often cited by service technicians as a source of leaks, contributing to greenhouse gas emissions. The study conducted laboratory testing of Schrader valves using an innovative experimental apparatus that tracked pressure and temperature of nitrogen gas contained by the valve over a 64-h test. The study found that 8 out of 61 used Schrader valves tested leaked at rates that would result in substantial refrigerant loss (M = 1,280 g/yr, SD = 3,168 g/yr, range = 9.4 to 9,117 g/yr). Gasketed caps were found to prevent refrigerant loss. Combining a Schrader valve with a gasketed cap significantly reduces the risk of leaks, and their use should be encouraged in air conditioning systems. The methodology developed for estimating leak rates from Schrader valves could be applied to other components in refrigeration systems, contributing to more comprehensive efforts to reduce refrigerant emissions. [ABSTRACT FROM AUTHOR]

• A novel parameter is introduced to refine the refrigerant leakage theory. • The refrigerant leakage process carries a higher oil content is confirmed. • The effect of leakage mass flow rate on oil content is investigated. • The oil content is highest when refrigerant leaks from the high-pressure pipe. Refrigerant leakage is a situation that often occurs in refrigeration equipment such as heat pumps. However, certain alternative refrigerants, while exhibiting superior environmental performance, possess varying levels of flammability. The leakage of flammable refrigerants into confined spaces can pose a significant risk of explosion. The amount of lubricant in the leaking refrigerant will undoubtedly affect the flammability characteristics of the refrigerant. In this paper, the content of PVE32 oil in the leaking refrigerant during the operation of a heat pump was investigated. The results showed that, under the five leakage rate scenarios set up in the experiment, the oil concentration was highest when the leakage occurred at the condenser inlet and lowest when the leakage was at the evaporator outlet. During the leakage process of the experiment, as the mass flow rate of the leakage increased, the oil content in the early stage of the leakage increased, but the oil content in the late stage of the leakage decreased. The reasons for the change in oil content were analyzed by the oil circulation rate and the degree of phase separation. The decrease of the oil circulation rate and the change of the degree of phase separation were the key factors affecting the magnitude of the oil content as the leakage proceeded. The results of the study reveal the leakage characteristics of lubricating oil with refrigerant leakage. [ABSTRACT FROM AUTHOR]

• The solubility of R1234ze(E) and R1336mzz(E) in two lubricants was tested and compared. • Experimental solubility data were correlated by the NTRL activity coefficient model. • The Henry's constants of R1234ze(E) and R1336mzz(E) in PAG and POE were obtained. Trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) and trans-1,1,1,4,4,4-hexafluorobut-2-ene (R1336mzz(E)) are environmentally friendly working fluids with low global warming potential (GWP) that can be used in compression refrigeration and heat pump systems. In this study, a solubility measurement system was established to assess the solubility of R1234ze(E) and R1336mzz(E) in polyalkylene glycol ether (PAG) and polyol ester (POE) at temperatures (283.15–323.15 K). The Henry's constants for four binary systems R1234ze(E)/PAG, R1336mzz(E)/PAG, R1234ze(E)/POE, and R1336mzz(E)/POE were analyzed and compared. Additionally, The non-random two liquid (NRTL) activity coefficient model was applied to correlate the solubility data in this study. The results indicate that R1234ze(E) exhibits higher solubility in PAG lubricant, while R1336mzz(E) is more easily dissolved in POE lubricant. Moreover, the solubility of R1336mzz(E) in both PAG and POE lubricants shows greater sensitivity to pressure and temperature changes compared to R1234ze(E). The results reported in this study can serve as a valuable guide for the choice of suitable lubricants for R1234ze(E) and R1336mzz(E) in different applications. [ABSTRACT FROM AUTHOR]

• Condensation of zeotropic mixtures in horizontal tube were experimentally studied. • The processes of temperature glide and composition shift were demonstrated quantitatively. • The heat and mass transfer resistances were discussed. • Effects of vapor quality, mass flux and saturation temperature on heat transfer were presented. Zeotropic refrigerant blends have attracted wide interest due to their promises to reduce global warming potential as well as their potential ability to improve the performance of heat pumps and air conditioners. The complex phenomenon of non-isothermal phase change complicates condensation of zeotropic refrigerant mixtures and merits extensive investigation to better understand their performance profiles. The present work experimentally studied condensation heat transfer of R407C and R448A – two R134a-based zeotropic refrigerant mixtures – in a horizontal smooth tube, condensed by counter-current water cooling. Measurements for mass flux were in the range of 120 to 320 kg m −2 s −1 and saturation temperature in the range of 42 to 64 °C. Variation in refrigerant temperature and composition shift during condensation were quantitatively presented. The experimental data showed the effects of mass flux and saturation temperature on the heat transfer coefficients of R407C and R448A in different vapor quality regions. The analysis of heat and mass transfer resistances related to the flow regimes and refrigerant thermophysical properties provides a deep understanding of the condensation heat transfer of zeotropic refrigerant mixtures. The experimental data presented in this work are of value for the design of condensers. [ABSTRACT FROM AUTHOR]

The electrification of heating and cooling resources such as Heat Pumps has increased its share in the electricity consumption throughout the world. Furthermore, the utilization of domestic HPs is increasing within the Europe especially in Italy; however, the increased use of heat pumps along with other domestic loads can have a significant impact on the low voltage distribution network in terms of its harmonics injection to the network. This problem needs to be addressed properly by means of suitable models. This paper presents an aggregated load modelling approach to address the harmonic injections of heat pumps into low voltage distribution networks. For this study simulations are conducted in cosimulation environment of OpenDSS and MATLAB implementing the Iterative Harmonic Analysis considering a simple scenario of three independent houses connected to the distribution system. The results are presented in the form of generated harmonic currents, voltages, and percentage errors between considered models for the study. Frequency domain modelling approach appeared to be the best performing model in terms of tradeoff between accuracy and computational time. [ABSTRACT FROM AUTHOR]

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Heat pumps (HPs) have become pivotal for heating and cooling applications, serving as sustainable energy solutions. Coupled with renewable energy sources (RES) to run the compressor, which is the major energy-consuming component, they contribute to eco-conscious practices. Notably, their adaptability to be supplied by either alternating (AC) or direct (DC) currents, facilitated through converters, makes them more flexible for versatile renewable energy (RE) applications. This paper presents a comprehensive review of converter topologies employed in various HP applications. The review begins by exploring previous applied photovoltaic (PV)-HP projects, focusing on the gaps in the literature concerning the employed converter topologies. Additionally, the review extends to include a broader examination of the converter topologies that could be employed on the source and load sides of a system powered by a mix of renewable energy sources, such as photovoltaics (PV), wind turbines (WTs), and energy storage systems (ESS), and analyzes their strengths and weaknesses. Special emphasis is given to understanding the various topologies of the power electronics converters in the context of HP applications. Finally, the paper concludes with a summary of the literature gaps, challenges, and directions for future research. [ABSTRACT FROM AUTHOR]