Exergy Efficiency Values Research Articles

Thermal management enhancement of building-integrated photovoltaic systems using coupled heat pipe and evaporative porous clay cooler

The building-integrated photovoltaic (BIPV) panel systems often lead to a notable decline in PV panels efficiency and lifetime due to their temperature rise because of inadequate cooling. This study investigates the performance of innovative cooling strategy of using a coupled heat pipes and porous clay cooler and compare it with other related three BIPV cooling systems configurations including a conventional BIPV cooling with and without air gap and a pure evaporative porous clay cooling. The aim is to improve the PV panel cooling, ultimately reduce the PV temperature and enhance the overall performance of the BIPV system as well as reducing the building indoor temperature and boosting energy efficiency within the building. The system model, comprising sets of transient equations for the different system configurations, was solved using MATLAB and confirmed with previous experimental findings. The results indicate that comparing with the traditional BIPV system, using BIPV/Clay cooling systems and the hybrid BIPV/Clay-heat pipe cooling systems achieved peak PV temperature reductions of up to 14 °C and 14.7 °C, respectively. Additionally, these cooling methods led to a maximum interior room temperature reduction of approximately 14 °C and an average decrease of 8 °C. Moreover, the hybrid BIPV/Clay-heat pipe cooling system demonstrates superior performance compared to traditional BIPV system, achieving the highest improvements in PV electrical efficiency, output power, and exergy efficiency, with gains of 7.8 %, 6.4 %, and 8.4 %, respectively. Further, when the hybrid BIPV/Clay-heat pipe cooling system was employed, the clay cooling efficiency and clay exergy efficiency values improved on average by 30.2 % and 29.7 %, respectively, compared to the BIPV/Clay cooling system in addition to the increase of the lifetime of the PV panels due to isolating it from the contact with the water/water vapor of the clay cooling system. However, this hybrid approach resulted in a rise in electricity production costs from 0.077 $/kWh to roughly 0.138 $/kWh and extended the payback time from 7.38 years to 13.6 years. But, despite its initial economic drawbacks, the hybrid BIPV/Clay-HP cooling system demonstrates considerable effectiveness and long lifetime compared to other cooling configurations.

The thermodynamic and environmental analysis of a variable speed R404A refrigeration system using R455A

The suitability of drop-in application of low-GWP refrigerant R455A in a R404A refrigeration system is experimentally investigated in this paper comparing energy performance and environmental impacts (i.e., CO2 emissions) of the system. The evaporation temperatures are −5, 0 and + 5 °C while condensation temperatures are 30, 40 and 50 °C in the test conditions. Besides, the compressor speed is adjusted for three cases as 40, 45 and 50 Hz. The behaviours of COP, exergy efficiency and total equivalent warming impact (TEWI) are determined depending on evaporation and condensation temperatures as well as compressor speed. The results demonstrate that although cooling capacity of R404A is higher, COP of R455A is computed to be better than R404A about by 4.3 % (on average) for all covered cases. The exergy efficiency of R455A is also found to be higher compared to R404A. The COP and exergy efficiency values are reduced, TEWI enhances as compressor speed increases for both R404A and R455A. Additionally, an empirical expression (valid within about ± 5 % and independent of variable parameters such as refrigerant type, compressor speed as well as evaporation and condensation temperatures) is proposed for the relationship between nondimensional parameters COP and compression ratio. Furthermore, the amount of TEWI is verified to be lower for R455A than R404A, hence the studied alternative blend can be preferred due to the environmentally friendly characteristic. It can be suggested referring to the obtained results that R455A can be directly used in a R404A refrigeration system due to improved thermodynamic performance and diminished CO2 emissions.

Exploiting the Ocean Thermal Energy Conversion (OTEC) technology for green hydrogen production and storage: Exergo-economic analysis

This study presents and analyses three plant configurations of the Ocean Thermal Energy Conversion (OTEC) technology. All the solutions are based on using the OTEC system to obtain hydrogen through an electrolyzer. The hydrogen is then compressed and stored. In the first and second layouts, a Rankine cycle with ammonia and a mixture of water and ethanol is utilised respectively; in the third layout, a Kalina cycle is considered. In each configuration, the OTEC cycle is coupled with a polymer electrolyte membrane (PEM) electrolyzer and the compression and storage system. The water entering the electrolyzer is pre-heated to 80 °C by a solar collector. Energy, exergy, and exergo-economic studies were conducted to evaluate the cost of producing, compressing, and storing hydrogen. A parametric analysis examining the main design constraints was performed based on the temperature range of the condenser, the mass flow ratio of hot and cold resource flows, and the mass fraction. The maximum value of the overall exergy efficiency calculated is equal to 93.5% for the Kalina cycle, and 0.524 €/kWh is the minimum cost of hydrogen production achieved. The results were compared with typical data from other hydrogen production systems.

Performance analysis of triple basin solar still with energy-exergy analysis approach

An experimental investigation was conducted on novel design of triple basin solar still with different modification in the climatic conditions of India. The triple basin solar still was modified with attachments of evacuated tubes (ETCs), heat pipes (HP), corrugated surfaces and energy storage materials called modified triple basin solar still (MTBSS). To get the more water in distillate output and higher water temperature solar still was designed with three basin area. From experimental results it was found that the total distillate output obtained by MTBSS during day and night was 16.46 l/m2 and 7.40 l/m2, respectively. The performance of MTBSS was also check by 4E (Energy, Exergy, Exergo-Economic, Exergo-Environmental) analysis for economical and environmental point of view. The generation of exergy for evaporation (Exe,bw-ig) and convection (Exc,bw-ig) for MTBSS (Modified triple basin solar still) were 24.03 & 1.30 (joule) respectively. The values of energy efficiency (ƞenergy) and exergy efficiency (ƞexergy) obtained for MTBSS were 31.89% & 3.04% respectively. An economic point of view, the CPL of water remains higher in MTBSS. The NPBT for MTBSS was 2.5 months. For environmental assessment, the CO2 mitigation for MTBSS was 0.48 t/year, based on the exergy approach. The additions of ETCs, H.P, corrugated surface, and ESMs with MTBSS are effective from an exergo-economic and carbon credit point of view.

Thermodynamic and economic analysis of a novel compressed air energy storage system coupled with solar energy and liquid piston energy storage and release

Compressed air energy storage (CAES) is one of the important means to solve the instability of power generation in renewable energy systems. To further improve the output power of the CAES system and the stability of the double-chamber liquid piston expansion module (LPEM) a new CAES coupled with liquid piston energy storage and release (LPSR-CAES) is proposed. The coupled LPEM conducts suction stage B at the end of the expansion stage, ensuring stable exhaust pressure and temperature for the module. By establishing the thermodynamic and economic models of LPSR-CAES, the effect laws of key node parameters on the system performance are investigated. The results show that the heat transfer between liquid droplets and air dominates the heat transfer in LPEM. The proposed LPEM exhibits excellent isothermal performance and stability, with a maximum temperature difference of about 20 K during the cycle, and stable exhaust temperature changes within 10 K. Under the design conditions, the converted electrical efficiency, round-trip efficiency, exergy efficiency and net present value of the system are 68.31 %, 58.86 %, 66.99 % and 12.25 M$ respectively. The higher the solar supplement temperature, the more outstanding the thermal and economic performance of the system. The short-term energy storage system performance of the proposed system is more prominent. Based on the actual light data, the system can achieve 72.09 % and 69.41 % of converted electrical efficiency and exergy efficiency, respectively, at the 219th day. The results of this study provide theoretical support for the engineering application of the proposed system.

Exergoeconomic optimization of a proposed novel combined solar powered electricity and high-capacity cooling load production system for economical and potent generation via utilization of low-grade waste heat source

A novel system for combined electricity and cooling generation was introduced, integrating Flat Plate Solar Collectors (FPSC), Absorptional Heat Transformer (AHT), Organic Rankine Cycle (ORC), and Absorption Cooling Cycle (ACC) systems to utilize low-grade solar energy. The ability to use low-grade waste heat sources (70 °C–90 °C) via FPSC system for high-capacity integrated cooling and electricity generation in a more economical way, a feature not commonly addressed in conventional systems and previous literature studies, was a key advancement. The need for additional generators, boilers, and high-temperature heat sources was eliminated, resulting in substantial cost savings and a simplified system design. The FPSC-AHT integration, identified as having significant advantages over separate electricity and cooling load production, was comprehensively evaluated for its combined exergoeconomic and environmental benefits in multigeneration system design. The modeling was performed using Engineering Equation Solver (EES) and Transient System Simulation Software (TRNSYS) in Izmir, Turkey, with the aim of achieving the heightened economic efficiency and superior Coefficient of Performance (COP) values without high-temperature waste heat sources. Three configurations were examined, with the third demonstrating superior technoeconomic performance due to the increased thermal efficiency of solar hybrid photovoltaic-thermal (PV-T) systems. The higher cost per unit area in the PV-T system was effectively offset by the substantial electricity consumption, contributing to energy savings. Economic indicators for the third configuration included an initial investment of US$9.91 million, annual operational costs of US$1.29 million, a payback period of 4.2 years, an annual energy cost gain of US$9.25 million, a levelized cost of cooling (LCC) of US$0.014/kWh, and an electricity cost (LCE) of US$0.015/kWh. Through exergy analysis, toluene was identified as the optimal working fluid, revealing a total exergy destruction rate of 13245.46 kW. The performance of the proposed system was tested under different operation conditions, and based on these results, a sensitivity analysis and a comparison with the real-word studies were performed. In comparison to real-world data, the proposed system exhibits superior performance metrics, especially in terms of COP and exergy efficiency values. The optimal configuration, established using single and multiobjective optimization approaches based on exergoeconomic parameters, indicated annual electricity and cooling load production of 40000 MWh and 300 GWh, respectively. The system’s efficiency in producing 1000 kW of electricity power and 4000 kW of cooling load at a comparable cost to systems generating only one output was highlighted. To determine the technoeconomic performance improvement of the proposed integrated system, the optimal configuration of the novel integrated system was compared to a reference plant for similar-scaled integrated power and cooling generation (UCI Trigeneration Plant). Compared to the UCI Trigeneration Plant, the proposed system demonstrated significant improvements in technoeconomic performance. Specifically, the proposed system achieved a 164.13 % increase in annual electricity production, a 97.38 % increase in annual cooling duty, a 60.36 % reduction in initial investment, a 57 % reduction in annual operational costs, and a 47.5 % reduction in payback period. Additionally, the levelized costs of electricity and cooling were 40 % and 22.22 % lower, respectively. Significantly higher electricity and cooling output highlights the system’s ability to meet demanding energy needs. Lower initial investment and operational costs, coupled with a reduced payback period, make the system financially attractive. Lower levelized costs for electricity and cooling increase the system’s competitiveness and affordability. The innovative integration of technologies provides new insights into the design of multigeneration systems, setting a new benchmark for sustainable energy solutions.

Thermo-economic optimization on a combined heat and power system with supercritical Rankine cycle for power-to-heat batteries

The global energy structure is transforming to low-carbon, and it is urgent to construct a sustainable energy system mainly based on renewables. The power-to-heat batteries (P2HBs) show great potential for large-scale energy storage by converting low-cost renewable power to heat. This paper aims to study the thermodynamic and economic advantages of the P2HB integrated with a supercritical steam Rankine cycle (RC) to achieve combined heat and power (CHP) generation. Firstly, a system model of P2HB-CHP consuming grid valley power is developed. The system includes three sub-systems: P2HB, steam generator, and CHP. Thermodynamic and economic analysis models are developed, and the average exergy efficiency (ηav) and net present value (NPV) are formulated as performance evaluation targets, respectively. The genetic algorithm is used to perform multi-parameter optimization of the system. The thermodynamic optimization results show that the maximum ηav of supercritical P2HB-CHP is 0.47 %, 1.16 %, and 1.44 % higher than that of subcritical P2HB-CHP when the high working temperature of the molten salt reaches 505 °C, 570 °C, and 640 °C, respectively. The largest proportion of anergy is generated by electric heaters, over 72 %. The next largest proportion is heat exchangers, which is related to the heat transfer temperature differences. The results of the economic analysis show that the maximum NPV of supercritical P2HB-CHP is lower by 158 M$, lower by 74 M$, and higher by 55 M$ than that of subcritical P2HB-CHP when the high working temperature of the molten salt is reached 505 °C, 570 °C, and 640 °C, respectively. The high efficiency of supercritical RC reduces the costs of electric heaters and molten salts, but sets high demands on the heat exchangers. Although high-temperature molten salt results in high energy efficiency, the increased cost of molten salt reduces the profitability of the system.

Effect of channel depth ratio and absorber plate configuration on performance of a solar air heater

An experimental evaluation of the effect of channel depth ratio and absorber plate configuration on the performance of a baffled counter flow double-pass solar air heater (BCDSAH) is main objective of current work. The BCDSAH was constructed so as to permit adjustments of channel depth ratio (CDR) to 2, 3 and 4. During experimentation, the lower channel depth was kept at 50 mm while the upper channel depth was adjusted to 100 mm, 150 mm and 200 mm, yielding various channel depth ratios. The assessments were conducted for three configurations of absorber plate: (i) flat absorber plate, (ii) baffled absorber plate and (iii) baffled absorber plate with phase change material (PCM). The performance of the BCDSAH was evaluated at an air mass flow rate of 0.07 kg/s for temperature rise, useful heat gain (UHG), energy efficiency, and exergy efficiency. For CDR = 2 and a baffled absorber plate with PCM, the obtained average values of temperature rise, UHG, energy efficiency and exergy efficiency were 15.3 °C, 1075.2 W, 76.2 % and 2.7 % respectively. For the baffled absorber plate with PCM, increases of 8.5 %, 9.4 %, 10.1 % and 10.9 % were obtained in temperature rise, UHG, energy efficiency and exergy efficiency respectively for CDR = 2 compared to CDR = 4. Finally, a value of CDR = 2 and a baffled absorber plate with PCM are suitable for applications like drying of agricultural products and space heating.

Optimization of a combined gas turbine and steam Rankine cycle utilizing the chemical looping combustion (CLC) reactor for CO2 capture and Storage: Towards enhanced efficiency and Cost-Effectiveness

In recent years, CO2 released by fossil fuel power plants, through the process of capture and storage, has been tried to be separated from other combustion products and directed to the underground to prevent it from entering the environment. While various methods exist for this purpose, they are typically expensive and consume a significant amount of power. In this research, a proposed solution to study and optimize the capture and storage process involves a combined cycle power plant with two gas turbines and four steam turbines, equipped with a carbon dioxide capture and storage system using the chemical looping combustion (CLC) method. The storage of released CO2 is facilitated by four compressors operating in four stages. To begin, the developed model is validated in terms of energy, exergy, and economic factors. Subsequently, the system is optimized using an NSGA genetic algorithm, with two objective functions: exergy efficiency and total cost rate. Sensitivity analysis is conducted to define the decision variables. The results demonstrate that the optimization process has led to a 4.37 % increase in the system’s power output, from 379.75 MW to 396.37 MW. Moreover, the optimization has improved both the exergy and energy efficiency values, with these parameters rising from 51.97 % and 54.23 % to 54.24 % and 56.61 %, respectively. Furthermore, the total cost rate has slightly decreased from 46,267 to 46,020 $/hr as a result of system optimization.

Thermodynamic analysis of a multiple energy production system based on geothermal energy for commissioning in Canada and optimization by response surface method (RSM)

The thermodynamic analysis of a geothermal-based integrated energy system to produce liquid hydrogen, cooling, hot water, and power was presented in this study. The investigated system consists geothermal subsystems, a modified organic Rankine cycle (ORC), a PEM electrolyzer, and a liquid hydrogen storage source. Different organic fluids including refrigerants R113, R123, and R134a were investigated to increase the system performance. Analysis of organic fluids showed that the best organic fluid is R123 because it helps to increase the performance of the system. The authors employed the Design-Expert software and RSM for optimum results purposes, and the objective functions were chosen to be exergy efficiency (EE) and cost rate (CR). Following introduction of design variables, the mass flow rate of input to the evaporator, the temperature of input to heat recovery vapor generator, turbine efficiency, turbine input temperature, evaporator pinch point temperature, and pump efficiency, their impact on the system's performance were investigated. The optimal values for EE and CR were ultimately found to be 43.91 % and 45.12 $/h, respectively. Also, in this research, seven regions within Canada were investigated for the launch of the proposed system. The studied cities were Victoria, Vancouver, Regina, St. John's, Dawson Creek, Whitehorse, and Port Alberni. Finally, Regina was chosen because of the system's superior performance in electricity production at a reasonable cost in that area. The environmental results showed that the presented energy system in Regina city could help to expand 5 ha of green space by producing electricity at the rate of 4993.03 MWh in one year. The findings indicated that implementing the suggested system in Regina would help prevent 1018.6 tons of CO2/MWh from being emitted into the environment yearly, only by chipping in 24445.9 $/ton of CO2 per year.

Comparative analysis of water cooler for different working fluids: Energy and exergy approach

Enhancing the performance of traditional vapor compression cooling cycles is an important aspect in the quest to minimize global energy consumption, to own sustainable energy systems soon, and to preserve the environment. This study performed a comparative analysis of the performance of a water cooler with different working fluids to replace R143a and improve system performance. A mathematical model derived from energy and exergy analysis is developed for the evaluation of the effect of operating conditions on the system COP, exergetic losses, and exergetic efficiency. The evaluation has been conducted for evaporation and condensation temperatures ranging between -30°C to 15°C and 25°C to 55°C, respectively. Results showed that the cycle with R510A has the maximum COP. The average system COP with R510A, RE170, and R152a are 19.54%, 13.53%, and 9.36 % higher than that with R134a, respectively. The highest value of exergy loss takes place in the compressor. At different working fluids, exergy losses decrease as evaporation temperatures increase and condensation temperatures decrease. The system with R510A has the minimum exergy losses. The average exergy losses for systems with R510A, RE170, and R152a are 34.62%, 28.33%, and 18.64% lower than that of R134a, respectively. The system with R510A has higher exergy efficiency and R134a has the minimum values of exergy efficiency. Generally, the water cooler provided better performance with R510A and RE170 than with R152a and R134a. Therefore, R510A can be considered as the best replacement for R134a and R152a.

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.

A bibliometric and performance evaluation of nano-PCM-integrated photovoltaic panels: Energy, exergy, environmental and sustainability perspectives

One of the major problems regarding PV panels is the decline in power output and efficiency whilst exposed to temperatures surpassing their operating temperature. In order to preclude such undesirable situation, it is imperative to cool PV panels and provide a uniform distribution of surface temperatures during the implementation of the cooling method. Thermal management can be achieved at the surface temperatures of PV panels by utilizing phase change materials (PCMs). In this study, along with PCM, the potential of enhancing output parameters by decreasing the surface temperature of PV panels with the addition of nanoparticles (Al2O3) at different concentrations (0.05%, 0.1%, and 0.15% w/v) to PCM (RT35) is examined. The study compared five systems: a reference PV panel (PV), PV panel cooled with PCM without nanoparticles (PVPCM-0), and PV panels with PCM containing different concentrations of nanoparticles (PVPCM-0.05, PVPCM-0.1, and PVPCM-0.15). Among the five different systems, the PV panel containing 0.15% w/v nanoparticles (referred to as PVPCM-0.15) demonstrated the most effective cooling capability. Moreover, the PVPCM-0.15 system provided the highest performance with a 19.49% increase in panel power output. PV systems have average energy and exergy efficiency values of 9.06% and 3.79% for PV panel, 9.60% and 5.15% for PVPCM-0, 9.70% and 5.12% for PVPCM-0.05, 10.28% and 6.01% for PVPCM-0.1, and 10.44% and 7.29% for PVPCM-0.15. Upon analyzing the sustainability metrics, it was determined that the PVPCM-0.15 system was more energy and environmentally sustainable than the others.

Comparative analysis of different heat transfer models, energy and exergy analysis for hydrogen-enriched internal combustion engine under different operation conditions

The implementation of hydrogen as a fuel in internal combustion engines is widely considered a favorable optimal due to its zero-carbon emissions and high energy content. Heat transfer from engine cylinder walls has a major role on engine combustion, performance and emission characteristics. In this study, heat transfer analysis conducted by different heat transfer models and identify the best model to analyse the energy and exergy analysis of hydrogen enriched internal combustion engine. A series of experiments were conducted on a compressed natural gas internal combustion engine across varying hydrogen fractions, EGR ratios, engine speeds and load conditions to capture in-cylinder pressure data and heat transfer rate. The authors compared six distinct models for heat transfer based on absolute percentage errors of maximum pressure and indicated mean effective pressure. These models systematically incorporated into a quasi-dimensional combustion model (QDCM) on MATLAB for hydrogen-compressed natural gas engine, accounting for diverse operating conditions. Convective heat transfer models, including Woschni, Nusselt, Hohenberg, Han, Eichelberg, and Assanis correlations were employed. Comparative analyses were undertaken to identify the most precise correlation for predicting engine in-cylinder pressure and heat transfer rates with experimental results across a broad spectrum of operational conditions. The Woschni model, as presented, is most suitable for the QDCM of the hydrogen-compressed natural gas fuel blend. This suitability is indicated by the close alignment of Taylor length and turbulent intensity coefficients to 1, as well as the minimal absolute percentage error observed for indicated mean effective pressure. It is also observed that heat transfer rate is increased by increasing the engine load 25 %, 50 %, 75 % and 100 % as 49.57 J/deg, 129.26 J/deg, 245.35 J/deg and 250.62 J/deg respectively and heat transfer rate is decreased by increasing the speed of engine 1100 rpm, 1200 rpm, 1500 rpm and 1700 rpm as 137.34 J/deg, 134.21 J/deg, 95.33 J/deg and 48.57 J/deg respectively. The energy and exergy analyses revealed that elevating the engine load corresponds to a reduction in exergy destruction. Brake energy increased 15 % by increasing the load conditions from 25 % to 100 % and decreased 7 % by increasing the speed from 1100 rpm to 1700 rpm. Another significant finding from this study is that the values of both energy and exergy efficiencies were 38.42 % and 40.12 % respectively obtained by thermodynamic analyses.

Analytical study of exergetic efficiency of a solar air heater with C-shape roughness element

This study analytically evaluates the exergetic efficiency of solar air heaters incorporating C-shaped rib roughened absorber plates. Compared to flat plate designs, the proposed geometry significantly enhances energy performance. Optimal roughness parameters for maximizing exergy efficiency are identified, providing design guidelines for improved solar air heater systems. The maximum value of exergy efficiency of the Solar air heater, with C-shaped ribs was obtained as 5.9%.

Estudio comparativo de un ciclo transcrítico de dióxido de carbono alimentado por un único ciclo geotérmico flash en los modos de funcionamiento con/sin economizador

Renewable energy, particularly geothermal energy, is on the rise globally. It has been demonstrated that recovering heat lost during geothermal cycles is essential due to the inefficiency of these cycles. This paper pproposes a combined power generation cycle using EES software to model a single-flash geothermal cycle, and a trans-critical carbon dioxide cycle. The study compares the system's performance during its "Without Economizer" and "With Economizer" operational stages. The impact of the economizer on the system's output metrics, including the net power output, energy efficiency, and exergy efficiency, was examined. The results show that the "With Economizer" system's net power output increased from 451.3 kW to 454 kW. The energy efficiency difference between the two systems is based on the first law of thermodynamics, where the value ofthe "Without Economizer" system is 6.036%, and the "With Economizer" system is 6.075%. The system without an economizer had an exergy efficiency value of 26.26%, whereas the system with an economizer reached 26.43%, based on the second law of thermodynamics. Installing the economizer increased the total economic cost rate of the system from 0.225M$/Year to 0.2294M$/Year, which increased the product cost rate from 15.82$/GJ to 16.02$/GJ.

Análisis detallado de un motor diésel alimentado con mezclas de combustible diésel, aceite de linaza, biodiésel y etanol en el contexto termodinámico, económico y medioambiental

The growing demand for energy, coupled with volatile oil prices and the environmental damage caused by the harmful gases produced when it is used, has prompted countries to explore alternative energy sources. The transportation sector, an important end-user of petroleum, must adapt to the changing energy landscape and opt for new technologies to remain competitive. The study conducted a thorough thermodynamic analysis to assess the economic and environmental impact of using biodiesel (BD) made from cold-pressed linseed crude oil, commercial diesel fuel (DF), and ethanol in a compression-ignition (CI) engine. The study conducted a detailed thermodynamic analysis of performance and emission data recorded from a single-cylinder diesel engine. The analysis included energy, exergy, sustainability, exergoeconomic, exergoenvironmental, and exergoenviroeconomic parameters. The results pointed out that the fuel energy increases with the load, with B20E5 fuel reaching 6.887 kW at 25% load and 18.908 kW at 75% load. BD and blended fuels were found to have a higher fuel energy compared to DF. At 50% load, DF and B20 fuels have fuel energies of 10.765 kW and 10.888 kW, respectively. The analysis clearly demonstrates that commercial DF outperforms both DF-BD binary fuel blends and DF-BD-ethanol blends in terms of thermal and exergy efficiency values. Furthermore, DF exhibits lower entropy generation and exergy destruction than other binary and ternary blends. At maximum load, the exergy efficiencies of DF, B20, and B20E10 fuels were 28.5%, 25.8%, and 24.7%, respectively. The exergy losses were determined to be 10.495 kW, 12.317 kW, and 13.134 kW, respectively, under the same conditions. Binary and ternary fuel blends have a higher cost of power from the engine shaft due to the expensive market prices of ethanol and linseed oil-based BD compared to DF. However, B20 and B20E10 fuels have a lower environmental cost than DF, with B20 and B20E10 fuels estimated to be 2.8% and 5.3% lower than DF, respectively, at full load. These findings demonstrate the clear advantages of using B20 and B20E10 fuels over DF, both in terms of cost and environmental impact. Additionally, the infusion of ethanol into ternary blends reduces the environmental damage. This study provides a unique perspective on sustainable energy research and serves as a valuable reference for future studies.

Investigating New Environmentally Friendly Zeotropic Refrigerants as Possible Replacements for Carbon Dioxide (CO2) in Car Air Conditioners

The widespread use of automobiles and the increased duration spent within automobiles equipped with air conditioning systems have prompted various countries to enforce regulations that advocate for eco-friendly cooling substances (refrigerants) characterized by a slight global warming potential (GWP) and the absence of an ozone depletion potential (ODP). The imperative for automobiles to possess air conditioning systems that are both high-performing and eco-conscious has emerged as a means to mitigate their ecological impact, reduce fuel usage, and minimize carbon emissions. Zeotropic refrigerants, with a lower GWP than traditional alternatives, contribute to sustainability in car air conditioning by reducing the environmental impact and enhancing the energy efficiency, aligning with global regulations and fostering innovation in the automotive industry. This shift signifies a commitment to mitigating climate change and adopting environmentally conscious practices. The objective of the present study is to introduce blends of zeotropic refrigerants based on CO2 (R-744), namely R455A (a blend of R-744, R-32, and R-1234yf), R469A (a blend of R-744, R-32, and R-125), and R472A (a blend of R-744, R-32, and R-134a), to enhance the thermodynamic performance of pure CO2 refrigerant. Through the utilization of the Aspen HYSYS V11 software, an investigation is carried out involving thermodynamic energy and exergy analyses, as well as system optimization for an automotive air conditioning (AAC) system utilizing these novel zeotropic refrigerant blends, in comparison with the use of R-744 as the refrigerant. The study delves into the impact of parameters such as average evaporator temperature, condenser/cooler pressure, refrigerant flow rate, and condenser/cooler outlet temperature on AACs’ output parameters and subsequently presents the findings. The outcomes reveal that, under equivalent operational circumstances, the adoption of R455A, R469A, and R472A offers improvements in coefficient of performance (COP) by 35.4%, 18.75%, and 2%, respectively, when compared to R744. This shift is advantageous as it mitigates leakage-related issues stemming from the elevated operational pressure of R744 and eliminates the need for cumbersome equipment. R455A and R469A obtain the greatest COP and exergy efficiency (ηex) values, measuring 4.44 and 4.55, respectively, at the identical operating conditions with optimal condenser/cooler pressures of the examined blends. Furthermore, eco-friendly refrigerants R455A and R472A are recommended for integration into AAC systems in vehicles, as they help combat global warming and protect natural surroundings and leakage issues.

Optimizing solar-driven multi-generation systems: A cascade heat recovery approach for power, cooling, and freshwater production

The pursuit of an optimal solution for performance is essential in ensuring that a solar-driven multi-generation system functions efficiently. Due to the vast amount of solar power received by such systems, the production of significant waste heat ensues. Therefore, this study aims to propose and optimize a new cascade heat recovery method for a solar system that generates power, cooling, and freshwater. The designed configuration encompasses a parabolic trough solar collector to supply the required input energy of integration of a dual-pressure organic Rankine cycle with an ejector refrigeration cycle and an integration of a steam power cycle with a thermal vapor compression- multi-effect desalination. Employing both thermodynamic and economic assessments leads to attaining the performance indexes, which are involved in the optimization procedure. The outcomes of the simulation reveal that the net power, cooling, and freshwater productions are attainted at about 12.56 MW, 2.01 MW, and 138.3 kg/s. Also, the mass fraction 0.5–0.5 is an ideal composition for the highest values of net power and exergy efficiency, and these indexes are highly sensitive to changes in the temperature of vapor generator 3. The optimal operation mode provides an exergy efficiency of 14.76 % and a payback period of 5.49 years. In conclusion, the proposed cascade heat recovery method not only enhances the overall efficiency of the solar-driven multi-generation system but also demonstrates economic viability with a reasonable payback period.

Experimental investigation of a desalination system using porous carbon tube as a humidification media with swirl flow

Humidification-dehumidification (HDH) technology is a technique for small-scale water desalination applications based on carrier gas humidification motivated by thermal energy. The present work introduces an experimental investigation of a desalination unit based on HDH method. The main objective of this study is to evaluate the heat and mass transport properties of porous carbon tubes (PCT) as a humidification medium with swirl flow for HDH unit. Processes for transferring heat and mass are investigated at varied the temperatures of water and air, water-to-air mass ratios (MR), and helical flow channel pitch (HCP). The performance analysis is investigated based on some of performance metrics such as gained output ratio (GOR), humidification efficiency (ηH), exergy efficiency (ηex), sustainability indicator (SI), and water cost (WC). Results indicate that the increase in MR and HCP increases all of performance parameters. High values of MR based on low air flow rate decrease the entropy generation and enhance the exergy efficiency. The humidity efficiency and GOR improve with the rise in the MR based on the water flow rate. The study of sustainability indicator shows that the proposed system has possibilities of doing business. It still has room for energy improvement and losses, though. The system's usability will increase after these modifications are made. When the process temperature associated with heating the feed water or/and input air rises, more freshwater is produced. The proposed system's maximum hourly yield reaches about 0.225 L with cost 0.078 cent. The best value of GOR, exergy efficiency, humidification efficiency and suitability indicator performed by the current system are about 3, 51.67 %, 48.72 % and 2.07 respectively.