Higher COP Research Articles

Optimizing cascade refrigeration systems with low GWP refrigerants for Low-Temperature Applications: A thermodynamic analysis

This study offers a comprehensive thermodynamic analysis of a cascade refrigeration system conducted for low-temperature applications, focusing on the use of low-GWP and zero-ODP refrigerants to improve efficiency and sustainability. The target of this study is to explore the performance of the system using a combination of refrigerants: low-temperature cycle refrigerants such as R744, while high-temperature cycle refrigerants such as R717, R1234yf, R1234ze(E), R1336mzz(E), and R1336mzz(Z), respectively. The ECS model incorporating in REFPROP 10.0a tool was utilized to extract the data through coding for analysis. The assessment of this system involves the examination of various parameters such as its coefficient of performance, total compressor workload, total exergy, and exergy efficiency across various operational conditions. The results are compared with and without superheated and subcooled conditions to understand the impact of these parameters on the system performance. The system with R744 in the low-temperature cycle and R717, R1234yf, R1234ze(E), R1336mzz(E), and R1336mzz(Z) in the high-temperature cycle provides a higher COP and lower total compressor work compared to the conventional cascade refrigeration system. In optimal CRS, the R744-R717 pair attains the highest COP of 2.05 at the lowest possible compressor work from 9.53 to 4.87 kW than other refrigerants pair while evaporator temperature shifting from −55 °C to −20 °C. The exergy efficiency of R744/R717 is found at 26.47 % at an evaporator temperature of −55 °C, but it extends to a peak of 51.73 % at −20 °C. The study also shows that the superheating and sub-cooling of the refrigerants have a significant impact on the performance of the cascade refrigeration system. Superheating and sub-cooling at 10 °C, improves the COP of the system by reducing the compressor work and increasing the heat transfer efficiency. The research offers valuable insights into the system’s thermodynamic performance when employing low GWP refrigerants in low-temperature applications. These findings have the potential to guide the design and optimization of cascade refrigeration systems over the range of low-temperature applications.

Experimental investigation of ground-source heat pump system coupled to vertical and horizontal ground loops: A case study

This study presents an experimental investigation of the performance of the ground-source heat pump (GSHP) system coupled to both vertical and horizontal ground loops under four different scenarios in cold climate. The first two tests evaluated the performance of the two vertical ground loops coupled to the GSHP in both heating and cooling modes. The results showed that the COP of the GSHP ranged from 2.7 to 3.15 during the heating mode, while in cooling mode, the COP ranged from 3.75 to 5.4. The GSHP demonstrated a relatively constant performance during both tests, which could be attributed to a relatively stable ground temperature. The last two tests aimed to compare the performance of horizontal and vertical ground loops in cooling mode. In the first case, the ground loop flowrate was divided equally between the vertical and horizontal loops, resulting in an overall GSHP COP of 5.42. In the second case, equal Reynolds number was maintained in both loops, resulting in an overall COP of 5.36. The high COP observed in the last two cases was attributed to the constant low fluid temperature supplied by the ground loops.

A Novel solar-assisted air source heat pump system for urban renewal: Experimental test and numerical simulation

Old residential communities require novel heating solutions to meet heating demands sustainably. In Southern China, current heating systems in old communities have high energy costs and lack sustainability. A potential solution, air source heat pumps (ASHP), have evaporators susceptible to frost accumulation and poor heating performance at low ambient temperatures. This study proposes a hybrid design that uses additional solar thermal energy to improve energy gains from the air source; the innovative serial coupling design increases the air-source temperature by engineering the evaporator of the ASHP as the load-side of the heat exchanger. The novel hybrid design aims to be efficient, cost-effective, and sustainable, satisfying urban redevelopment needs. A prototype of the novel hybrid solar-assisted ASHP system was constructed; various performance parameters were evaluated, and system operation in extreme climates was simulated in TRNSYS. Results indicated that the novel hybrid system had significantly superior heating performance, delivering a 70.1% improvement in heating rate compared to single-source ASHP under lower ambient temperatures (13C). The novel hybrid system also had a high COP value between 5.7 and 6.3, significantly exceeding values of 2.3-3.5 for most air-conditioning units. It demonstrates consistent performance in all simulated climates. It is estimated that the novel hybrid system can save 1000 RMB in annual energy costs for an average Shanghai family and reduce Shanghais CO2 emissions by 4.7 million tons. The novel system addressed limitations of ASHP, optimizing performance while maintaining sustainability, offering a promising solution for urban renewal projects in China.

Energy and exergo-environmental analysis of a refrigerator-Stirling/Photovoltaic system for cold production

The Stirling refrigerator is a device capable of using green energies such as solar power. In this work, a refrigerator-Stirling/photovoltaic system is proposed to harness solar energy for cold production. The system consists of photovoltaic (PV) panels that capture solar energy and convert it into electricity, and a transmission belt linking the motor to the Stirling beta refrigerator to use the electricity for cooling purposes. The system is modeled on the basis of finite-dimensional thermodynamics, taking into account the refrigerator's internal and external irreversibilities. In addition, the wiring loss, dust coverage and shading of the photovoltaic system and the mechanical power loss of the Stirling refrigerator are taken into account in this model. Power equality has been considered as a system constraint. Finally, the effects of operational and design parameters on system performance are investigated. A numerical code is written in Matlab. The effects of PV module efficiency, Stirling regenerator efficiency and PV derating factor on system performance are quantified, also the optimum operating parameters obtained. The refrigerator-Stirling/photovoltaic has a high COP and a low cooling capacity, in contrast to the refrigerator-Stirling/Dish-Stirling. The optimum solar electric COP and maximum cooling rate are 0.7063 and 1413 W respectively at an optimum panel area of 2 m2. Optimum exergy efficiency is 38.5 % at fv = 0.1, ecological coefficient of performance (ECOP) is 20.3 % at N = 48 rot.s−1, optimum exergy destroyed is 33.31 W at K1 = 21.5 W.K−1. This system can be used to preserve vaccines in hospitals.

Experimental investigation of two-stage NH3–H2O resorption heat storage system with solution concentration difference

Widespread application of solar energy is severely restricted to its instability in time and space. Heat storage system is considered to be one of the most effective pathways to achieve long-term heat supply. Among all the heat storage technologies, solution concentration difference storage technologies stand out for low heat loss and high energy density. By substituting condenser and evaporator in conventional absorption cycle with a high-pressure absorber and low-pressure generator, a resorption cycle could be established. Compared with absorption heat storage cycle, working pressure of resorption heat cycle is lower, making it possible to utilize low-pressure heat source. Two-stage heat source cycle is further proposed to lower working pressure and upgrading supply water temperature. Resorption energy storage cycle with solution concentration difference is established and studied. A prototype based on two-stage ammonia-water resorption heat storage cycle was set up and tested. The result shows that the constraint relation between ambient temperature and heat source temperature of the proposed system. In single-stage mode, the lowest working ambient temperature is 5 °C when heat source temperature is 90 °C. The lowest working ambient temperature could be declined to 0 °C when heat source temperature rises to 120 °C. In two-stage mode, the lowest working ambient temperature is 0 °C when heat source temperature is only 110 °C, which proves the adaptability of two-stage cycle. The highest ESCOP appears in the 15 °C–120 °C single-stage mode, which is 0.742. The highest COP is 1.324 under the same condition. The highest energy density occurs in two-stage mode, which is 467.07 kJ/kg when ambient and heat source is set as 15 °C, 120 °C. The advantage that two-stage mode could enlarge solution concentration difference is verified.

Modelling and evaluating different multi-carrier energy system configurations for a Dutch house

The urge to reduce the dependence on natural gas for heating at the residential level has led to the deployment of different fossil fuel-free alternatives. In the Netherlands, two technologies are leading the transition: heat pumps, due to their high COP, and photovoltaic–thermal systems, due to their dual electric-thermal output. However, both represent a challenge for users and grid operators, aside from their stochastic behavior. Heat pumps alone can surpass a typical Dutch house’s total energy and power consumption. Photovoltaic–thermal systems, as their only electric homologs, usually have a mismatch between generation and demand, causing energy injections to the grid. From the electric perspective, storage systems are a proven solution to reduce the energy exchange with the distribution network. This paper proposes four multi-carrier energy system configurations for a Dutch household, comprising different combinations of a photovoltaic–thermal system, a battery energy storage, a heat pump, and an underground water tank thermal energy system, providing analytical models for every component (including the thermal losses from the thermal storage to the ground), and the space heating and electrical demands. We determined the components’ compatibility and evaluated the combinations considering their thermal performance, electrical performance, and equivalent CO2 emissions. The results suggest that using a heat pump combined with a photovoltaic system and a battery provides the best trade-off. The photovoltaic–thermal system alone could not supply the thermal demand required for comfortable space heating nor reach temperatures high enough to charge the thermal storage. Combining the thermal storage with the heat pump allows a certain degree of flexibility for the heat pump activation at the cost of COPs between 0.8 and 1.38 when used to charge the thermal storage, thus increasing energy consumption and equivalent emissions considerably.

Investigation of environmentally friendly new generation refrigerant R471A instead of R404A in low and medium temperature commercial refrigeration system

Hydrofluorocarbon (HFC) refrigerants (such as R134a and R404A), which are widely used in commercial refrigeration systems, contribute greatly to global warming. Because the global warming potential (GWP) values of HFC refrigerants are high. With increasing concerns about the environment (global warming, climate change, etc.) various legal regulations have been made to limit or phase out the use of refrigerants with high GWP values. To use the R471A refrigerant developed by Honeywell in 2022 as an environmentally friendly new-generation refrigerant in the commercial refrigeration system, the performance of the R471A refrigerant should be comprehensively evaluated. In this study, energy, exergy, and environmental analyses of using R471A refrigerant instead of R404A in low and medium-temperature commercial refrigeration systems were carried out and presented. Evaporator temperatures of − 30 °C, − 25 °C, − 20 °C, − 15 °C and − 10 °C and condenser temperatures of 30 °C, 40 °C, and 50 °C were selected to represent low and medium cooling temperatures and hot and cold country seasons. It was seen that R471A presents a lower mass flow rate (between 67 and 71%) and cooling capacity (between 61 and 68%) than R404A however has higher COP (between 6% and 14%) and R404A has exergy efficiency value of 6–14% lower than R471A. Also, from an environmental point of view, R471A has better environmental results than R404A.

Working Fluid Selection for High-Temperature Heat Pumps: A Comprehensive Evaluation

Heat pumps have the potential for several applications across various industrial sectors, showcasing significant promise, especially in sectors such as pulp and paper, food and beverage, chemical, non-metallic minerals, and machinery. Envisioning the near future, there is confidence that heat pumps can achieve temperatures above 200 °C, offering substantial potential for utilization in these sectors. Nevertheless, a crucial aspect for the advancement of high-temperature heat pumps is the selection of the fluid. Fluid selection involves considerations of both thermodynamic efficiency and environmental impact, requiring fluids with zero ODP, negligible GWP, and no PFAS. Moreover, it is essential to consider the risks to human health associated with a specific fluid. Despite extensive research, particularly in the realm of vapour compression heat pumps, choosing the most suitable working fluid for these applications is a complex undertaking. Therefore, this paper conducts a theoretical analysis to evaluate potential fluids with suitable thermodynamic properties for high-temperature heat pumps (HTHPs). The comparative results gleaned from this study provide valuable insights for the comprehensive analysis of fluids, showing promise within temperature ranges dictated by specific applications. The metrics employed in the comparison emphasise the merits of fluids in terms of the overall performance, dimensions, and operating ranges of applicable compressor, heat exchange capacity, transport properties, and safety. One noteworthy finding from the analysis is that maintaining a constant HTHP lift (at 40 K) results in having the highest COP across all fluids when the condensing temperature ranges between 85% and 90% of their respective critical temperatures. According to the results of the analysis, natural fluids, including water and alcohols like ethanol or methanol, emerge as particularly compelling candidates.

Theoretical comparison analysis of R134a, R1234yf, R452A and R454C refrigerants used in automobile, trailer and commercial and industrial cooling systems

The increasing environmental disasters in recent years are caused by the release of artificial substances into the environment. The majority of artificial-containing emissions originate from petrochemical products. It also contributes to artificially containing refrigerants used in cooling systems. Artificial refrigerants have contributed greatly to the depletion of the ozone layer and subsequently to global warming. Research on new refrigerants as an alternative to refrigerants that contribute to every environmental disaster is of great importance. In this study, theoretical performance comparisons were made between R1234yf, which is an alternative to R134a refrigerant used in automobile air conditioning systems, and R452A, R454C refrigerants, which are used as alternative refrigerants in industrial, commercial and trailer cooling systems. Performance analyses were carried out according to different condenser and evaporator temperatures. Analysis results are given depending on condenser/evaporator pressure ratio, mass flow rate, compressor power, cooling effect coefficient (COP) and compressor outlet temperature. According to the study results, it was observed that the COP value increased with the increase in evaporator temperature, while the compressor inlet-outlet pressure ratio, refrigerant flow rate, compressor power and refrigerant compressor outlet temperature decreased. It was observed that the refrigerant with the highest compressor power and mass flow rate was R452A, followed by R1234yf, R454C and R134a, respectively. R134a was found to have an average of approximately 5.4%, 8.6% and 0.6% higher COP than R1234yf, R452A and R454C, respectively.

Impact of the Regulation Strategy on the Transient Behavior of a Brayton Heat Pump

High-temperature heat pumps are a key technology for enabling the complete integration of renewables into the power grid. Although these systems may come with several variants, Brayton heat pumps are gaining more and more interest because of the higher heat sink temperatures and the potential to leverage already existing components in the industry. Because these systems utilize renewable electricity to supply high-temperature heat, they are particularly suited for industry or energy storage applications, thus prompting the development of various demonstration plants to evaluate their performance and flexibility. Adapting to varying load conditions and swiftly responding to load adjustments represent crucial aspects for advancing such systems. In this context, this study delves into assessing the transient capabilities of Brayton heat pumps during thermal load management. A transient model of an emerging prototype is presented, comprising thermal and volume dynamics of the components. Furthermore, two reference scenarios are examined to assess the transient performance of the system, namely a thermal load alteration due to an abrupt change in the desired heat sink temperature and, secondly, to a sudden variation in the sink mass flow rate. Finally, two control methodologies—motor/compressor speed variation and fluid inventory control—are analyzed in the latter scenario, and a comparative analysis of their effectiveness is discussed. Results indicate that varying the compressor speed allows for a response time in the 8–20 min range for heat sink temperature regulation (first scenario). However, the regulation time is conditioned by the maximum thermal stress sustained by the heat exchangers. In the latter scenario, regulating the compressor speed shows a faster response time than the inventory control (2–5 min vs. 15 min). However, the inventory approach provides higher COPs in part-load conditions and better stability during the transient phase.

Evaluations of heat pump water heater with liquid-separation condensation from perspectives of performance enhancement and heat exchange area reduction

Heat pump water heater (HPWH) offers great potential to reduce energy consumption in water heating applications. But its performance enhancement and/or initial cost deduction are the main challenges to promote market penetration. In this paper, a heat transfer improvement technology, i.e., liquid-separation condensation (LSC), is implemented to HPWH and screen to achieve the maximized COP (E-HPWH) or reduced condenser area (R-HPWH). A model of HPWH with LSC is developed and validated, and its predictions are in good agreements with tested results from the baseline (B-HPWH) with an average deviation of 4.92 % at most. By using this validated model, E-HPWH and R-HPWH are obtained by adjusting the path arrangement and separation efficiencies. With the same heat transfer area, the COP of E-HPWH reaches 4.48, which is 7.43 % higher than that of B-HPWH, and the heating time is shortened by 13.1 %. With the same COP of B-HPWH being 4.17, the heat transfer area of R-HPWH is reduced by 22.2 % and heating time is shortened by 4.1 %. Then transient heating-up process of three HPWHs are comparatively investigated. Results indicate that E-HPWH has the highest compressor power as well as pressures and temperatures at the inlets of condenser and evaporator, followed by R-HPWH and B-HPWH. E-HPWH and R-HPWH overperform B-HPWH in terms of heat capacity before 4220s, due to the increased mass flowrate. Compared to B-HPWH, E-HPWH and R-HPWH have averagely 15.02 % and 7.29 % higher COP before 2790s and 1860s, respectively. Their states are less differentiated as the water temperature increases.

EN Improving the energy efficiency of refrigeration equipment with a direct sales function

The increased use of refrigerants with low global warming potential GWP over the past decade indicates that manufacturers are already making gradual replacements with refrigerants with reduced environmental impact. Thus, in addition to HFC gas phase-out requirements, most EU countries are pursuing a trend to reduce the energy consumption of refrigeration appliances. Such countries restrict the import of equipment that does not meet the energy efficiency requirements. This paper presents the ecodesign of refrigeration equipment in relation to the requirements of the sales market using the Regulation on Conformity Assessment Procedure. HVAC&R equipment contributes to GHG emissions in two ways: directly through refrigerant leakage or venting, and indirectly through electricity use, the latter accounting for up to two-thirds of GHG emissions. The paper compares the energy and environmental characteristics of refrigerants R404a and R290 in freezer M200V. The experimental results show that the highest COP va­lues in the system for R404a and R290 are 3.02 and 3.19, respectively. Possibilities of complete transition from F-gases to natural analogues with GWP ≈ 0 are shown. At application of R290 its advantages on energy efficiency are obvious - reduction of electric power consumption of freezing chests on 8,9 %, influence on environment R404A – GWP=3260, R290 – GWP=3. The calculation of energy efficiency class for freezing chest was made. To improve energy efficiency, a number of design modifications were made: the density of the thermal insulation material and the compressor were changed. The energy consumption of the modified version at the second climatic class was measured at 1.23 kW/24h, and the energy efficiency coefficient according to the calculation EEI =34.904, which corresponds to the energy efficiency class «C».

Thermochemical storage networks for integration of renewable energy sources through seasonal load shifting

Thermochemical networks are a rather new subject in research and support our goal to lower winter electricity demand and foster the integration of renewable energy sources. This paper takes a first step towards a performance analysis of thermochemical networks and a comparison to a classical district heating network for a virtually defined network of 1.3 km length, assuming a space heating load of 204.7 MWh represented by 33 residential buildings. The performance comparison is done for winter operation when space heating demand is present. The simulation results clearly revealed that for the classical district heating system, thermal and pressure losses lead to a significant increase in the loads, further increasing the electricity demand for the heat pump and the circulation pump. Conversely, for the thermochemical network, no compressor is needed to extract the heat from the boreholes and the circulation of the sorbent solution was found to be minute, leading to a negligible electricity demand for space heating supply. This resulted in a very high electric COP as well as a high exergy efficiency compared to a classical district heating system. Further, the volumetric energy storage density was compared, recording a 2 to 22.3 times higher value for the thermochemical network.

MOF-derived CoP nanoparticles anchored on P, N co-doped carbon nanoframework as robust electrocatalyst for rechargeable Li-O2 batteries

Currently, transition-metal phosphides (TMPs) coupled with heteroatom-doped carbon materials have attracted promising prospects in lithium‑oxygen (Li-O2) batteries. The CoP electrocatalysts have been extensively studied as popular electrode materials because of their efficient catalytic activity. However, numerous obstacles remain in optimizing synthetic techniques and exploring electrocatalytic mechanisms for CoP-based electrocatalysts. Herein, metal-organic frameworks (MOFs)-derived CoP nanoparticles anchored on P, N co-doped carbon nanoframeworks (CoP@PNCFs) are successfully designed at different phosphorization temperatures. The effects of the concentration of CoP active species, and the amount of P and N doping on the electrochemical performances are comparatively investigated and compared for different catalysts. The optimal catalyst, CoP@PNCF-700, displays high CoP active component, pyridinic-N and graphitic-N content, and abundant defect structures to enhance the electrochemical activity. More importantly, the CoP@PNCF-700 catalytic Li-O2 batteries deliver a high discharge specific capacity of 9630.5 mAh g−1 at 100 mA g−1 and a prominent long cycling stability of 187 cycles with a fixed capacity of 500 mAh g−1 at 200 mA g−1. This effort provides a facile strategy for designing cost-effective electrocatalysts for other energy-storage systems.

Energy and exergy analysis of an ejector-compression refrigeration cycle with double IHX

This paper shows an energy and exergy analysis of an ejector-compression refrigeration cycle, in which two heat exchangers are included to the system: 1) between the condenser and liquid separator (IHX-1) and 2) between the condenser and the evaporator (IHX-2), which is an alternative configuration proposed and this configuration is defined as ERC+IHX-1+IHX-2. The effect of evaporation temperature and the heat exchanger effectiveness on the energy and exergy efficiencies and the irreversibilities of each component of the cycle have been analyzed for refrigeration and air conditioning applications. The results show that for the alternative configuration and an effectiveness of IHX-1=80%, it results slightly with a higher COP than when the configurations work with an effectiveness of IHX-2=80%. However, the exergy efficiency increases when the evaporation temperature decreases. The components that show the highest contribution to the irreversibilities in the ERC+IHX-1+IHX-2 configuration are: the condenser, the compressor and the evaporator; whereas that the lowest contribution is due to the expansion valve and IHX-1. In addition, the alternative configuration proposed presents a higher exergetic efficiency and lower irreversibilities than the configurations ERC+IHX-1 y ERC+IHX-2 reported in the literature.

An ejector-assisted integrated thermal management of electric vehicles switchable between heating and cooling (reversible AC/HP)

Electric vehicles have become increasingly widespread in recent years due to environmental issues and limited natural resources, and the related thermal management strategies are receiving growing notice. A heat pump air conditioning system for cabin and battery pack thermal regulation (both heating and cooling) is proposed and studied under different operating conditions. The attention of the present study is more directed towards the heating mode of operation; cabin air conditioning in winter and electric aircraft application. Due to environmental considerations and restrictive laws, environmentally friendly refrigerants are also considered as alternatives for R134a. To improve the system's performance, an ejector is placed before the compressor and the refrigerant temperatures in the evaporator and chiller are set to be different. The performance of the proposed system is studied for both heating and cooling modes to compare with the basic system (without ejector). An exergy analysis is also carried out to further analyze the thermodynamic characteristics of the system. The results indicate that the proposed system's COP is improved for both cooling and heating modes under all operating conditions. For the heating mode, the highest COP was equal to 4.36 for R600a, and the COP improvement was between 8 and 47 % based on the different operating conditions. For the cooling mode, the highest COPs were equal to 5.20 and 5.17 for R600a and R1234ze(E) atTevap=Tchil=5°C respectively. The COP improvement for R600a was equal to 14 % atTevap=Tchil=−25°C, and it increases as the chiller temperature is raised. The exergy analysis also indicate that the highest exergy destruction occurs in the compressor and throttling valves. Moreover, R600a and R1234ze(E) show a better overall performance compared to other refrigerants. R600a and R1234ze(E) resulted in the least total exergy destruction of approximately 41 kW for the cooling mode and 51 kW for the heating mode. The exergy efficiency for R600a and R1234ze(E) was equal to 64 and 63 % respectively for both the cooling and heating modes.

The influence of the incoming air velocity with the fan on the inlet side of an air-water generator on the freshwater mass

The air-water generator is a promising device to provide freshwater in the future. However, the machine still produces less freshwater; hence, a study of the effect of air velocity with a fan installed at the entrance of a simple air-water generator on the freshwater mass was conducted under environmental conditions. The air velocities varied were 4 m/s, 5 m/s, and 6 m/s. The air-water generator was made from a refrigeration machine system using R134a refrigerant as the working fluid. The compressor specification was 1 PK rotary type. The results show that the highest average freshwater mass obtained is 1241 g for 7 hours, the highest COP was 4.72, and the highest total heat transfer rate is 208.21 J/s.

A fuel cell range extender integrating with heat pump for cabin heat and power generation

Batteries, Heat Pumps (HPs), and fuel cells (FCs) are critical for transport decarbonization and a net zero future. However, cabin heating in extreme conditions leads to severe driving range reduction in current Electric Vehicles (EVs). The performance of the heat pump (HP) in EVs and its performance enhancement technologies are widely investigated but cannot, simultaneously, provide sufficient heat and high COP. The source and amount of the waste heat within a vehicle for the heat pump integrated system is a crucial challenge to improve performance. The structure becomes increasingly complicated, but the benefits are not significant. Therefore, in this study, a small Fuel Cell, battery and heat pump integrated energy management system for range extended EVs (FCBEEV) is designed. The cogeneration characteristic of the fuel cell and waste heat from battery pack are utilised by the heat pump to ensure a high-level of cabin comfort in extremely cold temperatures and an extension of the driving range. A numerical model was established in MATLAB and the results were analysed from energy, exergy, environment, and economic (4E) perspectives. In this study, we show that the highest COPsys of the proposed system is 5.8 and can improve the driving range (DR) by 65% to 110% compared to the reference systems. The exergy efficiency of the suggested system is 75% at −10 °C and the fuel cell and internal condenser are the primary causes of the exergy destruction. The environmental impact decreases by 13 kg/year per car compared to current EVs with a Positive Temperature Coefficient (PTC) and Air Source Heat Pump (ASHP) system, and the reduction is primarily sourced from the indirect emissions. The operating cost which includes driving and heating is 28.9% higher than cited for an ASHP and PTC system and 41% higher than the PTC baseline system. The payback duration is 300,000 km at current market prices, and it is predicted to be shorter to 100,000 km, if the cost of the fuel cell stack is estimated at £4000 and the H2 price is the same as electricity. We anticipate that the proposed system can significantly improve cabin comfort and driving range anxieties, as well as promote the decarbonization of transport.

The Effect of Condenser Type and Refrigerant Type on the Two-Stage Vapour Compression Refrigeration System: An Experimental Study

In this study, the effects of refrigerants and condenser type on the coefficient (COP) of performance value in a two-stage intercooled vapour compression refrigeration system have been investigated experimentally with the designed device. There is a total of eight configurations designed for experiments, and these are compared with each other. During the experiments, a copper tube condenser, a micro-channel condenser, and R404A and R449A refrigerants were used in the designed device. The main focus of this study is to investigate the effect of condenser type, refrigerants, and the number of compressors on the COP in a vapor compression refrigeration system. In this study, it was concluded that designs using a micro-channel condenser have a higher COP than designs using a copper tube condenser, and the most efficient design for the system is the one using the micro-channel condenser and working with R449A refrigerant.

Thermodynamic performance assessment and application feasibility analysis of small heat pump water heater using CO2/R41 azeotropy mixture as refrigerant for sustainable development

In order to improve the application possibility of CO2/R41 azeotropy mixture in the refrigeration industry, the optimum mass ratio of composition is defined and determined according to the thermodynamic properties and safety. On the basis of the first and second laws of thermodynamics, a model is proposed to evaluate the performance of CO2/R41 single-stage transcritical cycle (CO2/R41 cycle) in which a throttling valve is integrated and CO2/R41 azeotropy refrigerant is adopted. The performance of CO2/R41 cycle at the optimum mass ratio of CO2/R41 azeotropy mixture is then compared with that of a CO2 two-stage transcritical cycle with throttling valve (CO2 two-stage cycle) and that of a CO2 single-stage transcritical cycle with expander (CO2 expander cycle). The results show that the optimum mass ratio of CO2/R41 azeotropy mixture is 0.583/0.417. Compared with CO2 two-stage cycle and CO2 expander cycle, CO2/R41 cycle has the advantages of a simpler structure, lower optimum high pressure, appropriate discharge temperature of the compressor, and higher COP. Therefore, the CO2/R41 azeotropy mixture with the mass ratio of 0.583/0.417 is eco-friendly and can be considered as a good alternative refrigerant for application in the refrigeration industry. The simple CO2/R41 cycle shows great feasibility to replace the complex CO2 two-stage cycle and CO2 expander cycle.