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Current study deals with performance evaluation of the solar power tower driven recompression with main compressor intercooling (RMCIC) supercritical CO2 cycle incorporating the parallel double evaporator organic Rankine cycle (PDORC) as bottoming cycle using low global warming potential fluids to reduce the global warming and ozone depletion. Using the PDORC instead of the basic organic Rankine cycle, waste heat from the intercooler and cycle exhaust were recovered simultaneously to enhance performance of the standalone RMCIC cycle. Exergy, thermal efficiency, efficiency improvement and waste recovery ratio were considered as performance parameters. A computer program was made in engineering equation solver to simulate the model. It was concluded that by the incorporation of the PDORC thermal efficiency was improved by 7–8% at reference conditions. Maximum combined cycle's thermal and exergy efficiency were found 54.42% and 80.39% respectively of 0.95 kW/m2 of solar irradiation based on R1243zf working fluid. Among the results it was also found that maximum waste heat was recovered by the R1243zf about 54.22 % at 0.95 effectiveness of low temperature recuperator.

The main purpose of the current research work is to suggest a novel integrated multi-generation energy system and scrutinize 4E evaluation. This system consists of a solid oxide fuel cell, a PEM electrolyzer for hydrogen production, and an ejector-based absorption chiller for the coefficient of performance improvement. All parts of this system are verified with existing reports and papers. Effect of fuel cell current density, SOFC fuel cell temperature, absorption chiller evaporator temperature, and condenser temperature, and outlet turbine pressure has been investigated and reported. The effect of mentioned parameters on the exergy and cost rate has been considered. Data illustrate that the maximum exergy destruction rate belongs to the SOFC contributing 60% of the total exergy destruction rate of the system. Under the given condition of the system, the net produced power is about 200 kW with an exergy efficiency of 30.2% and thermal efficiency of 60.4%. At the considered condition the total cost rate of the system is estimated about 22.29 $/hr. The results of the present work provide a scientific base for designing poly-generation systems with high efficiency and reasonable cost rate.

Modern gas turbine engines operate at high temperatures to improve thermal efficiency and power output. Increased rotor inlet temperatures increase the rate of heat transfer to the turbine blades, which requires sophisticated cooling schemes to keep the blade temperature at acceptable levels. This work is a numerical investigation of film cooling techniques as applied to gas turbines. The cooling performance of two differently shaped holes, namely, Ginkgo Forward and Ginkgo Reverse, were investigated in terms of centerline and local lateral cooling effectiveness, and a comprehensive comparison was made with the cooling performance of a cylindrical hole. The investigations were performed at a constant density ratio (DR = 2.0) and three different blowing ratios (BR = 1.0, 1.5, and 2.0). Under all of the operating conditions, the results demonstrated significant augmentation in centerline and lateral cooling effectiveness when the Ginkgo Reverse shaped hole was used, followed by the Ginkgo Forward and cylindrical cooling holes. For the shaped cooling holes, the low velocity gradient through the film alleviated the jet lift-off and turbulence, resulting in decreased entrainment of hot gas to the bottom surface. To conclude, the prominent lateral dispersal of the coolant due to the shaped cooling holes significantly enhanced thermal protection and the overall cooling performance.

This paper takes an industrial extraction heating unit as the research object, introduces a heat storage device into the steam bypass and proposes two schemes for discharging, one for electricity users and the other for heat users. The unit’s original peak shaving plan, bypass peak shaving plan, and bypass heat storage combined peak shaving plan were analyzed in this paper by building a unit analysis model in Ebsilon software. The results show that the bypass heat storage combined peak shaving scheme for power users has the largest peak shaving range, it has increased by 163.87MW compared with the original unit when the heat supply get to the largest. In one storage and discharge cycle, the scheme of bypass heat storage combined peak shaving discharging to electricity users has the highest cycle thermal efficiency and the highest operating profit, compared with the bypass peak shaving scheme, the operating revenue of the scheme has increased by 16.85%.

Climate change has a huge challenge to 2050. Some renewable energies can be installed to reduce CO2 production. Unfortunately, the photovoltaic systems, wind energy, and ocean energy devices do not have direct thermal applications. These systems are useful for people’s electricity consumption. Absorption heat pumps (AHP) are thermal devices for increasing the temperature level from an energy source at medium temperature level, such as plane solar collectors, to another energy sink. The main problem with design, power calculations and device construction is a lack of education about this technology, which is more complex than compression heat pumps but with 90 % less electric energy consumption that would be supplied by photovoltaic cells. This paper shows an approximation for future engineers designing several absorption heat pumps to avoid global warming beyond the Paris Agreement. Future engineers should be encouraged to analyze this technology with this first and basic approach.

Distributed aircraft propulsion has renewed the interest in power-dense, high-efficiency power packs. Ceramic turbomachinery could be a major enabler, although no successful design has been achieve...

Refrigeration and power are the most desirable requirements in commercial places and offices. Goswami cycle is one of the solutions to generate power and refrigeration simultaneously with less pollution. In the Goswami cycle, the power and refrigeration streams are connected in series, the refrigeration output is limited in a series arrangement. In the present study, parallel streams are proposed to improve the performance of the cycle. In the Goswami cycle, the saturated vapour is enriched for power and refrigeration. In the present study, the saturated vapour is used for the power generation, the saturated liquid is flashed to the intermediate pressure, and the generated wet vapours are enriched for refrigeration processes. It is observed that power generation is increasing with an increase in dryness fraction and the fall in basic solution concentration, whereas the refrigeration effect is growing with the fall in dryness fraction and increase in basic solution concentration. The modified cycle is consistently generating higher output than the conventional cycle. The thermal efficiency of the Kalina flash cycle is 29.05% higher and the exergy efficiency is 5.61% lesser than the Goswami cycle.

Chemical energy is not effectively converted into mechanical energy by an internal combustion engine. Major portion of heat energy get dissipated with exhaust and coolant. Use of thermoelectric generator (TEG) technology is regarded as an environment friendly technique for recovering the waste heat, with which heat energy directly converts into electrical energy. In this study, an experiment is conducted in which TEG technology has been used to recover waste heat going out through exhaust gas from the diesel engine. Thermoelectric modules were fixed on the surface of stainless steel made pipe having square cross-section. It has been found that the power output of thermoelectric generator enhances with the increase in engine load. The maximum electrical power output of TEG has been obtained as 37 W at maximum load of 6 kg. Overall thermal efficiency of diesel engine has also been improved with the use of TEG type of waste heat recovery system.

In the present research work, effect of hydrogen (H₂) flow rate, on the performance of modified dual fuel (DF) engine powered with two biodiesels is studied. Biodiesels derived from Jack fruit seed (JKFSDOB) and Nigella Sativa oils (NLSTVAOB) and their B20 blends are used as pilot injected fuels while H₂ is used as the manifold inducted fuel in the modified DF engine. Further influence of H₂ gas flow rate on the modified DF engine by using conventional mechanical fuel injection (CMFIS) for optimal performance of engine is investigated. Increasing the hydrogen gas flow rates reduces brake thermal efficiency (BTE), smoke, CO (Carbon monoxide) and HC (Hydrocarbon) emissions while NOx (Nitric oxide) emissions from DF engine increased. The engine operated by renewable fuel combinations of biodiesels and H₂ in DF mode engine can facilitate partial as well as complete substitution for fossil fuels and reduce the greenhouse gas emissions.

An ancient B.T.M. with P.C.M. was controlled through the issues of high inflexibility of phase change material, leakage problems and very low conductivity in thermal energy. This research paper reports a facile batter thermal management and creativity along with induced non-rigid phase change material composites. This battery model can be determined by the flexible phase change material composites along with an intervention due to the recovery in shape and non-rigidity of flexible phase change components. This assemble was modelled to be efficient and compact without any requirement for grease. A constant state reveals various stages of phase change material which has various properties in thermal efficiency. A unified state was linked with the recovery shape of flexible phase change components, which can cause a low resistance in FCPCM and battery. Battery thermal management demonstrates the perfect process of thermal control power. If the battery was discharged from 90 to 10% of charge, then the temperature of flexible phase change components depends upon battery thermal management. It was 44.5 °C during the 3.5 °C rate, which was 29.8 °C lower than no phase change material. It also reveals low-temperature oscillation inside the long-time process and range of heat of recovered phase change material. The performance of battery thermal management and its flexibility will give perceptions of passive battery thermal management systems.

Indian jujube (Ziziphus mauritiana) and Date palm (Phoenix dactylifera L.) the most important fruit crops that can grow in India's hot arid regions. The perishable nature of Indian jujube and date fruits leads to post-harvest loss. Both of these fruits are highly perishable, containing more than 80% moisture. Moisture needs to be reduced to less than 20% for storing it for a longer period of time. A phase change material (PCM) based hybrid solar dryer was developed, which consisted of the collector of area 1.06 m2 and two drying trays made of SS (0.50 m2) and that two half trays (0.24 m2). The performance of the developed PCM dryer was evaluated by drying fresh Indian jujube and date palm fruits having an initial moisture content of 65–80% (wet basis) and compared with the developed dryer without PCM. The drying system works so that phase-change material stores the thermal energy during sunshine hours and releases it at night. Therefore, the dryer is effectively operative for the next 5–6 h. The temperature of the drying chamber was observed as 6 °C higher than the ambient temperature in July 2020 during date palm drying after sunshine hours till midnight and it falls gradually, and temperature in the drying chamber was observed as 5°Celsius higher than the ambient temperature in January 2021 during Indian jujube drying. The variations in moisture content (wet basis) of the Indian jujube fruit are reduced from 80% to 22% within seven days by using the dryer with PCM and in 9 days dryer without PCM. In date palm fruit, MC reduced from 65 to 20% in 6 days in the dryer with PCM and eight days without PCM. The thermal efficiency (η) of PCM based hybrid photovoltaic thermal (PV/T) solar dryer (η = 18.0%) was found better than that of natural convection mode without PCM based hybrid solar dryer (η = 15.8%). The developed solar dryer provides a promising alternative for drying other arid food produced after sunshine hours with a real-time data acquisition system. It is also found to be superior in retaining quality.

In present scenario fossil fuels are getting depleted, in addition to this dependency and price is increasing. A time may come in future there might fuel crises. Hence, in order to make a better future. Renewable fuels from different and large number of sources can be typically used as fuel to generate electricity and for transportation in replacement of fossil fuels. This background view describes the of injection timing (IT) effect on engine performance, combustion and characteristics of Emission using waste cooking oil methyl ester (WCOME) and induction of producer gas with pilot injection of diesel on dual fuel mode of working. Thus, experiment shows the optimization of different injection timing (IT) (19–31° in step of 4°) to improve the dual fuel engine performance. Investigation of WCOME with producer gas operation at 27° bTDC showed reduced emission levels with increased brake thermal efficiency.

A novel cycle model of the capacitive salinity/heat engine mainly consisting of nano-porous super-capacitors is established for harvesting mixed free energy caused by salinity difference between the river water and the seawater, and the thermal energy due to the temperature difference. The heat engine is charged and discharged in the cycle of a low temperature brine and a high temperature fresh water, respectively. The analytical expressions of the cyclic work output and efficiency are given. General performance characteristics of the capacitive salinity/heat engine are analyzed. The temperature of the heat reservoir and salt concentration of seawater are optimized to improve the efficiency of the capacitive salinity/heat engine. The optimal selection ranges of several main parameters are provided. When the Stern distance is equal to 1 nm and the charging voltage is equal to 3.5V, the energy conversion efficiency of the capacitive salinity/heat engine is about 40%, while the pure thermal efficiency in the cycle is about 16.9%. The energy conversion efficiency of the capacitive salinity/heat engine is significantly larger than that of the capacitive heat engine. The results obtained can facilitate the application of this technology to real life, which can reduce the consumption of fossil fuels.

In the present work, effect injection timing (IT) on the modified dual fuel (DF) engine performance with effective utilization of biodiesel and gaseous fuel combinations is reported. Biodiesel prepared Ceiba Pentandra oil called Ceiba Pentandra oil methyl ester (CPNTOME) and its B20 blend (CPNTOME B20) are used as pilot injected fuels while the biogas (raw and purified) is used as the inducted fuel in the modified DF engine. Hence, the present research focus on the study of DF engine performance fuelled with liquid and gaseous fuel combinations. Meanwhile, the effect of IT on modified DF engine performance is investigated. Brake thermal efficiency (BTE), carbon monoxide (CO), hydrocarbon (HC) and smoke emissions were found to be less besides higher emissions of NOx were observed. Combustion parameters such as ignition delay (ID), and peak pressure (PP) are analysed. The DF engine operated on renewable fuel combinations in DF mode can cover the way for partial substitution of fossil fuel along with reduction in greenhouse gas emissions. Advancing the IT improves the DF engine performance and reduces the smoke, CO and NOx emissions.

A novel solid oxide fuel cell (SOFC) multigeneration system fueled by biogas derived from agricultural waste (maize silage) is designed and analyzed from the view point of energy and exergy analysis. The system is proposed in order to limit the greenhouse gas emissions as it uses a renewable energy source as a fuel. Electricity, domestic hot water, hydrogen and cooling load are produced simultaneously by the system. The system includes a solid oxide fuel cell; which is the primary mover, a biogas digester subsystem, a cascaded closed loop organic Rankine cycle, a single effect LiBr-water absorption refrigeration cycle, and a proton exchange membrane electrolyzer subsystem. The proposed cascaded closed-loop ORC cycle is considered as one of the advanced heat recovery technologies that significantly improve thermal efficiency of integrated systems. The thermal performance of the proposed system is observed to be higher in comparison to the simple ORC and the recuperated ORC cycles. The integration of a splitter to govern the flue gas separation ratio is also introduced in this study to cater for particular needs/demands. The separation ratio can be used to vary the cooling load or the additional power supplied by the ORC to the system. It is deduced that net electrical power, cooling load, heating capacity of the domestic hot water and total energy and exergy efficiency are 789.7 kW, 317.3 kW, 65.75 kW, 69.86% and 47.4% respectively under integral design conditions. Using a parametric approach, the effects of main parameters on the output of the device are analyzed. Current density is an important parameter for system performance. Increasing the current density leads to increased power produced by the system, decreased exergy efficiency in the system and increased energy efficiency. After-burner, air and fuel heat exchangers are observed to have the highest exergy destruction rates. Lower current density values are desirable for better exergy-based sustainability from the exergetic environmental impact assessment. Higher current density values have negative effect on the environment.

This article presents a numerical analysis on the thermohydraulic and thermodynamic performance of a parabolic trough solar collector (PTSC) receiver's tube equipped with wavy promoters. A computational fluid dynamics (CFD) with the aid of finite volume method (FVM) is adopted to examine the flow and thermal features of the PTSC's tube receiver. The Reynolds number in the range of 5000–100000 with four fluid inlet temperatures in the range of 400–650 K are utilised. Three different advanced hybrid nanofluids (Fe2O3-GO, Fe2O3–SiC and Fe2O3–TiO2) dispersed in Syltherm oil 800 are employed inside the PTSC's receiver tube. The numerical outcomes are verified with the available correlations and with other numerical and experimental data available in the open literature. The numerical results reveal that the utilisation of wavy promoters inside the PTSC's receiver tube can significantly augment the thermal performance, where the average Nusselt number is improved by 150.4% when utilising Fe2O3-GO/Syltherm oil hybrid nanofluids at 2.0% concentration instead of Syltherm oil. Furthermore, the maximum reduction in the absorber's average outlet temperature is in the range of 7–31 °C. The overall thermal evaluation criterion (PEC) is found to be in the range of 1.24–2.46 using bricks-shaped nanoparticles. The results show that the thermal efficiency increased by 18.51% and the exergetic efficiency increased by 16.21%. The maximum reduction in the entropy generation rate and the entropy generation ratio are about 48.27% and 52.6% respectively. New correlations for Nusselt number, friction factor and thermal efficiency for PTSC tube having wavy promoters using hybrid nanofluids are developed.

Publisher Summary This chapter presents an analysis of the efficiencies and inefficiencies of a system, which can be used to identify where the greatest opportunity for gains can be derived. It can also be used to benchmark the performance of one system against another. The thermal efficiency of any furnace system is defined as the useful energy derived from the system relative to the energy input. However, it is not necessary to measure the energy that is lost through the walls of the furnace, etc. to calculate the efficiency. It is only necessary to know the useful energy out, which is usually relatively easy to determine, as it will be directly related to the production rate. The efficiency of a furnace system depends on each step by which the energy is transferred from the chemical fuel energy and the electrical energy to the process energy contained in the end product. The total efficiency is dependent on the efficiency of each operation in the process, such as pump, preheater, furnace, and cooler. Examination of furnace performance data can help to usefully identify the relative contributions of thermal quantities. If the production rate is plotted against thermal input then, allowing for a reasonable degree of scatter owing to other influences, a straight line relationship is usually observed.

The operation of an integrated CPVT/ORC unit is investigated to identify the possibility of combining efficiently an ORC engine with a CPVT collectors’ field. The combined system is designed to operate so that the heat provided by the CPV field is at a temperature level in the range of 70–90 °C. The performance of the ORC engine is assessed towards comprehending its behavior under varying thermal loads and, as a result, maximizing the overall system electricity production. The analysis reveals that the electricity production from the ORC engine may be in the order of approximately 17 % of the total output of the combined system and that the implementation of the examined technological solution could increase the solar energy conversion efficiency of the CPV field, provided that the ORC engine operates at its maximum thermal efficiency. Finally, the preliminary economic analysis highlighted the potential of the integrated unit, which could be competitive even for small-scale systems.

Photovoltaic-thermal (PVT) collectors can be applied in order to concurrently generation of electrical and thermal energy. In the present study, a vertical hybrid PVT solar dryer has been developed and analyzed by utilizing numerical and experimental approaches. ANSYS Fluent software has been employed to visualize both flow and thermal behavior inside the vertical PVTs. The main aim of using vertical structure of PVT dryer is its space-saving potential. For enhancing heat transfer, fins have been integrated over the absorber plate and PV panel. The obtained experimental findings showed that thermal efficiency values of the finless and finned vertical PVT collectors were in the ranges of 47.46-54.86% and 50.25-58.16%, respectively. Moreover, sustainability index values of finless and finned drying systems were achieved between 2.16-2.75 and 2.38-3.25, respectively. The obtained results showed that applying high air flow rate in finned vertical dryer notably improved the drying performance. In addition, the deviation between numerical and experimental findings obtained in the range of 4.2-8.7%. (c) 2021 Elsevier Ltd. All rights reserved.

Photovoltaic system is one of the promising electricity generation devices due to its direct solar energy conversion, safe power transmission and practicability. However, its performance is very sensitive to higher temperatures. Photovoltaic/Thermal systems were presented for enhancing the electrical efficiency and making use of the lost thermal energy. In this research, a combined usage of Paraffin as a phase change material and a stainless-steel porous media was used to decrease its temperature and make use of it. Two different systems were used for comparison. One contains Stainless steel wool with paraffin, and the other with only Paraffin. Three flow rates of 0.2, 0.3, and 0.4 LPM were used of water as a circulating and cooling fluid. It was found that, for all the flow rates, the system with a porous metallic media achieved lower surface temperature, higher electrical efficiency, and higher overall efficiency. The temperature of the PV cell decreased by from 5 to 25⁰ C. The enhancement achieved was from 10% to 28% in the overall efficiency, and 1% to 4% in the electrical efficiency. This proves the importance of the porous metallic media in enhancing properties of the phase change materials when using with the Photovoltaic modules cooling.

This paper investigates the effect of slits within the arc-plug insert of the solar parabolic trough receiver (PTR). In order to predict the performance of the parabolic trough collector (PTC) with arc-plug slits within the absorber tube; two different variants of slits of 2 mm and 1 mm thicknesses are considered. Then, each of the variants of slits with different thicknesses are varied in terms of numbers of their occurrence in the arc-plug. The 2 mm thickness slits are varied in 5, 7, and 9 numbers with uniform space of separation between them in the arc-plug. While 1 mm thickness slits are varied from 11 to 13 in numbers and also maintaining uniform space of separation between them like in 2 mm thickness slits. The objective is to determine the effects of viscous dissipation within the slits of the arc-plug of PTR; and also, the optimized version of the slit with its numbers. It is found that 2 mm slits with 9 in numbers showed the highest value of thermal efficiency as compared to all other cases. The thermal efficiency (η) of the PTC with arc-plug slits are seen to be about 1.642 times of conventional PTC; whereas, 1.309 times of arc-plug without slits. Therefore, it is always beneficial to use slits within inserts of PTCs for its performance enhancement; but, the selection of slit’s thickness and its numbers plays a vital role in its application.

Water scarcity is a big challenge in many countries including Saudi Arabia, for which solar water desalination is a strategic goal due to the high solar intensities and the long sunshine duration. The main objective of this study is to develop a low cost and high efficiency solar water desalination device for small communities and remote areas in Saudi Arabia. The study is conducted in December 7th, 2020 (winter season) under the climatic conditions of Ha'il city (27.66 oN, 41.72 oE), Saudi Arabia. An inclined solar still was designed with a black cotton wick and a continuous saline water circulation flow via a small pump. Results showed high device performance with low freshwater production cost. The device is able to produce 3.21 L/m2day with 50.55% thermal efficiency and $0.0118/L cost of freshwater yield. Also, the device productivity is expected to be higher in the summer season. The proposed device has a significant low cost of $76.5/m2 which can be very attractive in the solar desalination market. The developed device increases the efficiency and productivity by 139.12% and 21.13%, respectively, and lowered the freshwater production cost by 57.86% compared with the device without the wick.

Membrane distillation seawater desalination technology has received widespread attention. However, this technology has problems such as high energy consumption and high initial temperature requirements. A membrane distillation seawater desalination system integrated with low-concentrating photovoltaic/thermal (LCPV/T-MD) modules was designed. With the help of concentrating photovoltaic panels and solar collectors, the working fluid required for membrane distillation is cascaded heating to obtain distilled fresh water. The integrated LCPV/T-MD mathematical model the hybrid experimental system were established, and the thermal, electrical performance, and water yield were analyzed. The results show that the greater Δ P , the lower of the salinity c, and the higher the inlet water temperature Tin, the greater the water yield. The LCPV/T-STC heating subsystem can heat the water temperature above 60 °C, and then auxiliary heating by heating rod can meet the requirements of MD system for inlet water temperature. In the experiment, the thermal efficiency and the electrical efficiency of the system can reach 56.2% and 15.9%, respectively. The GOR of the total LCPV/T-MD system can reach 0.69, and the MD subsystem water yield can reach 0.579 L/(h·m2). The findings can provide guidance for the further study of membrane distillation.

The receiver is crucial in converting concentrated solar radiation to thermal energy in a solar parabolic dish collector. The most popular type of receiver is a cavity receiver, which reduces heat loss from the body. In this paper, an experimental investigation of the energy, exergy, and optical performance of two cavity-type receivers for a solar parabolic dish concentrator was carried out. The cylindrical and conical cavity tube receivers were designed and tested in the temperature range of 35 °C–190 °C, with water as the working fluid and a flow rate of 0.83 L per minute. The results showed that the conical cavity tube receiver is the optimum design, while the cylindrical shape is the second choice. The conical cavity tube design achieved 62% average thermal efficiency, 11% exergy efficiency, while the maximum optical efficiency was 82% under average solar irradiation of 865 W/m2. The overall heat loss coefficients of cylindrical and conical cavity receivers from the stagnation measure were 137 W/m2 and 125 W/m2, respectively. The maximum and average surface temperatures for both cylindrical and conical cavity tube receivers were reached at 140 °C, 115 °C and 155 °C, 125 °C, respectively. The simulation study was conducted using COMSOL Multiphysics software to investigate the temperature distribution of the receivers. The proposed lightweight conical cavity tube receiver was found to have a high capacity to be used with a solar parabolic dish-style concentrating device to operate heating water applications.

Waste production is an important problem for the developing world and globalization. The waste materials can be reused through recycling process and its environmental effects can be minimized. Utilizing renewable energy sources at the maximum level is also an important issue for a sustainable development in future as well as waste management. In this study, small-scale solar air heating systems were produced from waste materials to analyze the usability of waste material in renewable energy systems. Scrap metal elbows were used in the production of heaters. The first solar heater is hollow (SH) and the second one was modified by filling it with aluminum wool (SHAW). Both heaters were tested simultaneously at different flow rates (0.014, 0.010 and 0.006 kg/s). According to the experimental results, the thermal efficiency values for SH and SHAW were found in the range of 33.63-42.90% and 42.69-56.98%, respectively. In addition, it was observed that a low cost modification such as using aluminum wool can significantly increase thermal performance of the solar heating system.

Increasing the aperture of the parabolic trough concentrator (PTC) can effectively reduce costs and help promote. This paper proposed a circle and semicircle absorber tubes (AT) with a flat reflector (FR) in it for the large-aperture PTC system and the size of the AT was determined for the PTC with 8 m aperture width and 80° half rim-angle. The result shown the PTC system using a semi-circular AT with a diameter of 100 mm has the highest average thermal efficiency of 71.6% with DNI 400–1000 W/m2 at about 500 °Cand has best uniformity of 38.8%. However, its deformation is highest and 1.7 and 1.6 times other two ATs. Therefore, how to reduce the deflection has become a research direction in the future. Currently, the circular AT with a diameter of 80 mm is the most practical with an average thermal efficiency of 69.1% and a minimum deflection.

The solar collectors’ shape is an essential parameter in the thermal performance of solar water heaters, and absorption of maximum radiation at different hours, regardless of the angle of the collector, is an important issue. A spherical solar water heater is experimentally investigated in practical dimensions. This solar water heater is a fixed, symmetrical collector with the ability to track the sun independent of the optimal placement angle. The heat transfer surface is also increased by designing the fluid passage bed as a spherical absorber coil. When the flow rate intensifies, the temperature difference between the input and output currents reduces. The maximum instantaneous and average daily thermal efficiencies are 87% and 69.7%, respectively, for a flow rate of 1.6 lit/min. In this case, the hot water required by 6.35 people is provided, then at higher flow rates, the thermal efficiency is reduced. At solar noon, the upper and lower semi-spheres absorb the maximum and minimum radiations, respectively. In general, the trend of changes in the absorption of the solar radiation has no absolute extremes, meaning proper tracking of the sun and stable performance during the day. This solar heater can be easily used in the facade of buildings.

An energy conservative air-conditioning system is critical to promoting energy conservation and emission reduction. One promising alternative is liquid desiccant cooling system (LDCS), which can be driven by low-grade heat and has superior dehumidification performance. However, energy waste from traditional regeneration process restricts its application from widespread use. To overcome this disadvantage, a wood-based heat localization regenerator is presented: it localizes the thermal energy on the regeneration surface avoiding the unnecessary heating of bulk solution. The real performance of this new regenerator has been investigated theoretically and experimentally in this paper. The regeneration process of desiccant solution has been analyzed and a regeneration performance prediction model has been developed. Some performance indexes have been derived from experimental data. A regeneration performance comparison has been conducted between the heat localization method and the traditional heating method. The results show that the new method improves regeneration thermal efficiency by above 50% and the maximum value can achieve 43.6%. Besides higher performance, the reduction of energy consumption, initial cost and complexity has achieved with the heat localization regenerator. The overall improvement makes LDCS such a competitive alternative to the current air-conditioning system.

The solar energy produced by Scheffler parabola (10 m2) is not fully exploited by the solar distillation system of aromatic and medicinal plants. In this work, the optical losses in the primary and secondary reflectors, and the thermal losses at each part of this system (solar still, steam line, condenser) were determined. A thermal energetic and exergetic analysis were also performed for a solar distillation system of rosemary leaves. For average intensity radiation of 849.1W/m2 and 6 Kg of rosemary leaves during 4 h of distillation, exergy and optical efficiencies of the system achieved up to 26.62% and 50.97%, respectively. The thermal efficiency of the solar still, steam line, and condenser is about 94.80%, 94.30%, and 87.76%, respectively. The essential oil yield per unit of consumed energy and the total efficiency of the solar distillation system, taking into account the heat losses in the solar still, steam line, and condenser, as well as the optical losses in the two reflectors, is 6.18 mL/ kWh and 40.00%, respectively. The efficiency can be as high as 42.42 % if the steam line is insulated. Moreover, the comparison between the solar steam distillation and conventional steam distillation shows that solar distillation is much more efficient since it gives better results and especially it avoids the emission of 12.10 kg of CO2 during extraction.

In this paper, design and development of an energy-efficient oil-fired tilting furnace with an innovative recuperator are reported. During the melting of metals, it is reported that around 50% of the total energy is lost in flue gases. Therefore, there is always a need to improve upon the efficiency of the furnaces. The design of the recuperator is based upon the application of all the three basic modes of heat transfer to preheat the incoming air. Financial and environmental aspects were also evaluated after upgradation with the recuperator. The internal hollow pipe of the proposed recuperator is so designed that at its exterior cylindrical surface, multiple turns of a guide way are welded in a spiral fashion. This increases the heat transfer between the flue gas and ambient air to the burner. The study shows that the efficiency of the oil-fired tilting furnace got enhanced by 50% after implementing the proposed recuperator. Specific fuel consumption without the recuperator was 0.166 kg/kWh, which was reduced to 0.138 kg /kWh with the recuperator. The principle of increasing thermal efficiency and limiting fuel consumption was based on heat recovery from the combustion products to preheat the cold incoming fuel mixture. Therefore, this study focuses on the relations between combustion and heat exchanges on a large scale. The exergy evaluation technique was used constructively to estimate the furnace’s efficiency since the exergy efficiency is an additional sustainable appraisal in real situations. A channel for flue gases is provided in the developed furnace, which helps to divert hazardous gases away from the working environment.

Solar energy is a most promising resource of non-conventional energy to utilize for heating. Based on the application there are two kinds of utilization one is water heating and the second one is air heating. This is generally done by flat plate solar collector but due to its limitations to use in higher temperature ranges (i.e., 70–95 °C) and poor performance led to introduce the application of evacuated tube and parabolic trough collector. To fabricate the solar air heater, one ended evacuated tube is used as a receiver of the parabolic trough and U-tube copper pipe is inserted within the evacuated tube. The air heating process is done at various mass flow rates and it was found that the average outlet temperature was more at the minimum mass flow rate, but the average efficiency was less. At maximum mass flow rate, the average outlet temperature was minimum, and the average thermal efficiency was maximum. The maximum thermal efficiency obtained was 24.1% at the 0.0082 kg/s mass flow rate and the maximum temperature that was obtained was 151 °C at 0.0062 kg/s mass flow rate. Hot air being used for different application in space heating, food processing, fruits and vegetable drying and in regeneration of desiccant.

Nexus water/energy security is one of the main global challenges for the future generation. Solar distillation (thermal process) represents a sustainable solution to water shortages and energy crisis in the world especially in the Middle East and North Africa region. The technique is based on a evaporation–condensation process via heat delivery through a cylindrical parabolic collector to a thermal energy storage, in the form of sand integrated into the solar still, to maximize water production efficiencies. It is a technically feasible and operational method. Results suggest that the additional solar collector flux has a direct impact on the increase in average sand and seawater temperature particularly over the period between 12 p.m. and 4 p.m. Seawater temperature increases by >26.6%. The energy stored quantity delivered for the distiller basin grows proportionality with the sand temperature, which is depending directly for the solar collector absorber temperature. The difference between the both temperatures defines a decreasing rate of −19%. The daily water production by the hybrid solar distiller is 6.5 l/day, it represents an increase of +91% compared to the traditional concrete solar still production (3.4 l/day), for the same geometry and meteorological conditions. HIGHLIGHTS Renewable energies integration in the seawater distillation process.; Improvement of the water evaporation phenomenon using a parabolic trough solar concentrator.; Solar still efficiency optimization by the thermal energy storage integration.; New design of the greenhouse still flow control principle, materials.; Proved the efficiency of the hybrid still compared to the concrete still in a Mediterranean climate.

In this research, a solar cooker was manufacture from the scrap of an elliptical satellite dish, the dish was covered with reflective layer of aluminum that reflects up to up to 85% of solar radiation. This solar cooker has the ability to move horizontally in 360 degrees and vertically in 90 degrees, which makes it easier to follow the movement of the sun. Experimental investigation was carried out on this solar cooker in January, March, June, September between the hours of 9:00 AM. to 3:00 PM local time in Baghdad city in year 2020, by heating 1 L of water at every experiment, the results showed the best month for testing is June, due to the increase in the intensity of solar radiation and the reduced influence of weather factors, wind speed and cloud cover. this changing environmental conditions led to an instability in energy efficiency. The results also showed that the thermal efficiency is correlated inversely with solar radiation. This means that whenever the quantity of solar radiation was high we needed less energy to raise the temperature of the water, because the thermal efficiency is the ratio of the sensible energy required to heat the mass of water in the pot when the solar energy falls on the dish at the same time, and is correlated inversely with temperature and wind speed.

Solar energy reaching Earth can be used as promising renewable energy to overcome the challenges of steam generation processes. Solar concentrators suffer from fine adjustment of solar radiation concentration and high investment cost. Therefore, multi-configuration receivers named the cylindrical cavity receiver, helical receiver, and the absorber-evaporator-tank have been manufactured from the coiled copper tube and brass plates, respectively. Then, they are tested and compared to improve the performance of steam generators. The performance of the absorber-evaporator-tank receiver has been compared with the cylindrical cavity receiver and helical receiver for a period from 10 am to 12 pm. The present investigation shows that the boiling point of water increasing when the pressure of generated steam increases particularly inside the coiled tube, which affects the dryness fraction of the generated steam. The present results show that the efficiency of the absorber-evaporator-tank is greater than the cylindrical cavity and helical receivers for the tested period. It is found that the thermal efficiency for the absorber-evaporator-tank doubles at noon, which indicates an effective solar receiver for generating steam.

Non admixed Natural gas-fuelled diesel engines are usually associated with harsh engine emissions as well as low performances at moderate to high engine loads. However, the use of Moringa biodiesel as additive in hydrogen-compressed natural gas (HCNG) is a viable novel strategy for reducing toxic emissions such as hydrocarbons and nitrogen oxides in CI engines. In this study, five hybrid HCNG–Moringa biodiesel (MB) oil samples labelled A–E were analysed for their abilities to improve the overall performance of a CI engine (Petter PH1W diesel engine). The fuels had a fixed volume by volume hydrogen : carbon ratio of 87:13% respectively, and the HCNG–MB hybrid samples consisted of 0, 5, 7, 10 and 13 %v/v MB for samples A, B, C, D and E, respectively. At higher engine loads (i.e. 58%–100%), the engine performance improved thus giving higher BTEs in the range of 19–33.9% for all the fuel blends relative to the BTE (15.1%–19%) of the unblended HCNG fuel; this confirms the suitability of MB as an additive for improving the brake thermal efficiency of CI engines; there were also reductions in HC, O2, CO2, CO and NOx emissions for all the MB–HCNG fuels relative to the case of the unblended HCNG fuel. At optimum condition, the fuel that gave the best results in terms of the aforementioned engine characteristics is the MB–HCNG fuel blend having 10% MB.

One feasible solution to reduce the cost of concentrated solar power is to employ a higher temperature and efficiency supercritical carbon dioxide Brayton power cycle. An alternative heat transfer medium and thermal energy storage (TES) system therefore needs to be explored. This work considered a variety of phase change materials (PCMs) and graphite as the storage media in four indirect shell-and-tube storage configurations, including a 3-PCM and 5-PCM cascade storage, a PCM-graphite-PCM hybrid storage and a single graphite storage. The sizing and design of the TES systems were performed by using a dynamic cycling methodology based on a transient 2D numerical model. The cost of those designs were then determined by using an economic model developed inhouse. This work also investigates the impact of some geometric parameters and cost assumptions on the techno-economic performance of the TES system. The analysis suggests a scenario exists whereby a low thermal efficiency storage system which therefore utilises less tube or storage material could be more cost-effective. Overall, the cost of hybrid TES is the lowest among all studied systems, at $26.96/kWht and $21.49/kWht for charging temperature of 720 °C and 750 °C, respectively, followed by the 5-PCM storage at $28.06/kWht and $21.82/kWht, respectively Refereed/Peer-reviewed

Natural gas furnaces are the major source of heat for Heating, Ventilation, and Air Conditioning (HVAC) applications. The usage of partially premixed type burners in gas furnaces are significant from past few years. The use of Computational Fluid Dynamics (CFD) on solving and understanding flame and heat transfer characteristics in these devices are limited. The accurate modelling of turbulence chemistry interactions in any combustion device has always been a great challenge to the CFD engineers. Especially, gas heat furnaces uses a lot of components with turbulent flow making the modelling more challenging. Since CFD must be able to predict the combustion flame behavior such as flame structure, flame length, flame temperature etc. over a region of fast chemical reactions zone, it is important to understand the different combustion modelling methods. In this paper an attempt has been made to compare two different modelling techniques, one using a simple global reaction mechanism Eddy Dissipation Method (EDM) and a detailed chemistry model Flamelet Generated Manifold (FGM). Most industries have been using these modelling methods based on the required application. The effect of air to fuel ratios on flame temperatures, conjugate heat transfer, mass fractions of CO2 and the furnace efficiency has been analyzed for both models. The study shows a better correlation of results with test using the FGM model as compared with EDM, in terms of air rise temperature, flue gas temperature and thermal efficiency.

The roller kiln is characterized by significant heat losses mainly caused by flue gas and cooling gas accounting for 70%. In this study, four novel power cycles including a basic organic Rankine cycle (BORC), a regenerative organic Rankine cycle (RORC), a Kalina cycle11 (KC11) and a Kalina cycle 34 (KC34) with the parallel double-evaporator (PD) configuration are proposed for dual-level waste heat recovery for a roller kiln. To identify the superiority system, the recommended power cycles are assessed and compared from an integrated thermodynamic and economic perspective. The impacts of the basic operating parameters on net power output, exergy efficiency, electricity production cost and savings to investment ratio are discussed. Meanwhile, the single-, bi- and three-objective optimizations are conducted and the optimal solutions are compared. The results indicated that for the considered optimization models, PDKC34 achieved the highest net power output of 211.06–224.45​ kW and thermal efficiency of 20.02–21.20%, PDBORC had the best economic performance on electricity production cost of 0.0875–0.0932 $/kWh, payback period of 5.709–6.210 year and savings to investment ratio of 2.191–2.335 while PDRORC with R-141b possessed the best exergy efficiency of 45.11–49.17%. On the whole, the four thermodynamic cycles contributed to the best thermodynamic performance in the maximizing net power output model while these had the best economic performance in the minimum EPC model. Besides, the evaporation unit had the highest impact on exergy destruction and total investment cost among all components for the studied optimization models.

Gas Turbine (GT) power plants have been represented as essential assets of energy units because of their numerous advantages compared to conventional coal power plants. However, their low thermal efficiency may make the continuous baseload operations a lossmaking alternative and threaten to continue. This fact is raising the importance of performing thermodynamic investigation according to the current operations’ conditions. This paper aims to conduct a thermodynamic investigation for two Siemens V94.2 gas turbine (GT) units based on current operations’ conditions. The reason for selecting these units is because they are operating at a much lower thermal efficiency than the designed thermal efficiency, and due to the age factor, the GTs are not suitable for major retrofitting due to poor return on investments. A numerical model is designed to simulate the overall thermodynamic process in the gas turbine using MATLAB SIMULINK. The obtained numerical results are validated by comparing them with the operational data collected from the stations. The thermal efficiency is increased by 30%, with a maximum output power equal to 140MW. The power output had decreased by 0.2% when the ambient temperature was increased by about 6.0 o C. A graphical optimization, where various conditions are plotted as graphs, is also carried out to achieve the maximum thermal efficiency and power output. Finally, a number of recommendations are made to address decreased thermal efficiency and output power.

In recent years, attentions are focused on the application of cutting-edge reactors to utilize the remarkable virtues such as safety and also higher thermal efficiency. Sodium-cooled fast reactors (SFRs) are midst the promising types of fourth generation reactors for their non-reacting behavior and packed configurations, which are considered as heat source of various thermodynamic systems. Accordingly, nitrogen Brayton cycle could be devised as power conversion system (PCS) of the mentioned sodium cooled reactors, due to its simple arrangement. In present study, proposing the topping system of nitrogen Brayton cycle as a power generation system which is driven by the sodium reactor system, Kalina and heat pump cycles, as bottoming cycles, were designed to increase the performance of the overall system by integration with topping system. Subsequently, energy, exergy and exergoeconomic analyses were carried out to examine the reliability of the proposed system. The results displayed that under operating conditions, thermal efficiency, exergetic efficiency of the proposed system are 34% and 62%, respectively. Furthermore, using the exergy point of view, it was revealed that steam generator heat exchanger, SGHX, is the foremost cause of exergy destruction. Also, in order to attain an inclusive insight over the system, a parametric analysis was conducted. Therefore, investigating the influence of alterations in key features of the overall cycle, several optimum working conditions, such as optimal basic concentration of ammonia in Kalina cycle, optimal turbines (I&II) expansion ratio and low-pressure compressor pressure ratio etc., were derived.

Cascade solar thermal systems provide a new direction for solar power generation. This paper focuses on the configuration optimization of a cascade solar system in which a Stirling engine array is applied. The array has multiple configurations. To find out the influence of the configuration on the performance of the engine array, five basic connection types were proposed. A Stirling engine model considering various losses and irreversibilities was developed. The model was evaluated by considering the prototype GPU-3 Stirling engine as a case study. Stirling engine array models were developed based on the Stirling engine model. Global efficiency and power of different connection types of Stirling engine arrays with the same hot and cold flows were evaluated. The effects of different factors on the performance of the Stirling engine arrays were considered. The result shows that flow order, the co-current flow or the counter-current flow, has little influence on the engine array performance. The maximum differences of thermal efficiency and output power of different flow orders are 0.39% and 0.70%, respectively. Serial flow connection type is the best for a Stirling engine array to obtain the best performance and adaptability for given heating and cooling fluids.

The depletion of fossil fuel and their impact on the environment due to continual usage for our ever-increasing power needs has forced us to look pro-actively towards other renewable forms of clean energy like wind, solar, ocean energy, etc. Amongst all renewable sources of energy, solar energy is abundantly available throughout the world and can meet the energy needs of our planet if appropriately harnessed. Solar thermal collectors are used to collect solar thermal energy, and then it is transferred to the fluid. The fluid may be air, water, oil, etc. depending on the application. Many researchers are working towards performance enhancement of solar thermal collectors. This article concentrates on solar air collectors and different types of modifications made in the recent past to improve its efficiency. This study is an attempt to summarize and present solar air heaters and various modifications for performance enhancement. The effect of modifications on the Nusselt number, friction factor, and thermohydraulic performance of the solar thermal collector is reported. The present article also discusses the effect of impingement of air on the device thermal efficiency and the geometric modifications. This paper will enable researchers working in this field to get a summary of important work done related to solar thermal collectors.

In the present study, the countermeasures are proposed to minimize the problem on torque and power output performance and exhaust gas emissions of natural gas engine with use of lower calorific gas. An experiment was conducted to identify thermal efficiency and harmful exhaust gas emission characteristics under partial load conditions in order to improve efficient fuel use in engines affected by the introduction of low calorific gases. A countermeasure for coping with emission gas regulations and preventing thermal efficiency deterioration under rated power operating conditions was then presented. An 11 L six-cylinder turbo-charged engine for city buses compliant with the EURO 6 regulation was used in the experiment, and the results obtained using the reference natural gas fuel were compared with those obtained using simulated low calorific gases. Pure methane (CH 4) was also used to investigate the effects of gas composition changes on thermal efficiency and exhaust gas emissions. When N 2 is added or pure CH 4 is used under partial load operating conditions, the combustion rate decreases; consequently, the optimum ignition timing is additionally advanced relative to that obtained when the reference natural gas fuel is used. If the N 2 mixing ratio is increased to a minimum of 4.7% under rated power operating conditions, combustion becomes unstable. Stable operation can be secured by increasing the set base fuel amount, 2.35% and 9.41% for pure CH 4 and 8% N 2 , respectively; however, torque decreases in proportion to the combustion speed of the gas fuel. The strategy of boost pressure control for the torque compensation can minimize the decrease in thermal efficiency.

Distillation efficiency can be improved by columns with multiple phase divisions, also known as parastillation (vapor division) and metastillation (liquid division). Although, previous studies demo...

Due to the growing trend of energy consumption in the world, the use of various renewable energy sources, including biomass, along with methods to increase the efficiency of energy systems has been considered. The presence of nitrogen in natural gas reduces the heating value of the fuel, increases the size of transmission lines and the capacity of gas pressure boosting stations. As a result, nitrogen is removed from natural gas with a concentration of more than 4 mol% at high current intensities. In the present study, a novel combined system for liquefied natural gas (LNG) production using nitrogen separation unit (ASU), absorption-compression refrigeration cycle, power generation plant, and biomass gasification process is developed. A cascade unit including the compression-absorption refrigeration and the mixed refrigerant systems is used to provide cryogenic energy in the proposed process. The specific power consumption of the liquefaction process is achieved as 0.7673 kWh/kg LNG. The total thermal efficiency of the integrated system is obtained by 54.29%. Pinch assessment is utilized to investigate the multi-stream heat exchangers and extracting relative heat exchanger networks. The pinch analysis results illustrate that the MHX1, MHX2, and MHX3 multi-stream heat exchangers have 3, 6, and 18 separate heat exchangers, respectively. Parametric analysis indicates on the system parameters indicated that the total thermal efficiency can be increased up to 58.80% by maximizing the generated LNG (as much as possible) and not injecting nitrogen into the gas turbine combustor.

The thermal performance of a flat plate solar water collector (FPSWC) depends on the amount of solar energy absorbed by the absorber, the quantity of heat transferred to the heat transfer fluid (HTF), and the fluid residence time in the collector. In this real-time experimental study, the thermal efficiency of the serpentine flow channeled FPSWC is compared with that of a conventional collector. The heat transfer coefficients (HTC) and heat loss coefficients of both configurations are evaluated at three different water mass flow rates (0.0083 kg/s, 0.0167 kg/s, and 0.025 kg/s). The results show that the serpentine flow channeled collector offers higher energy and exergy efficiencies of 78.9% and 6.47%, respectively, at a mass flow rate of 0.025 kg/s due to the continuous surface contact of the HTF with the absorber plate. The conventional collector yields energy and exergy efficiencies of 66.28% and 4.58%, respectively, at similar operating conditions. The peak HTC of the serpentine flow collector is 210 W/m2K, which is 27.3% higher than that of the conventional collector at a maximum flow rate. The maximum HTC is observed at a higher mass flow rate and lower absorber temperature. The heat loss increases when solar radiation intensity increases; the HTC reaches its peak value at the maximum solar radiation intensity. The proposed collector shows a cleaner production of hot water with a lower payback period when compared to a conventional collector, as evident from the enviroeconomic analysis. The findings can contribute to more successful deployments of solar thermal systems.

Dual Fuel (DF) combustion can help to reduce the environmental impact of internal combustion engines, since it may provide excellent Brake Thermal Efficiency (BTE) combined with ultra-low emissions. This technique is particularly attractive when using biofuels, or fuels with a low Carbon content, such as Natural Gas (NG). Unfortunately, as engine load decreases and the homogeneous NG-air mixture tends to become very lean, the high chemical stability of NG can be a serious obstacle to the completion of combustion. As a result, BTE drops and UHC and CO emissions become very high. A possible way to address this problem could be the addition of hydrogen (H2) to the NG-air mixture. In this paper, a numerical study has been carried out on an automotive Diesel engine, modified by the authors in order to operate in both conventional Diesel combustion and DF NG-diesel mode. A previous experimental characterization of the engine is the basis for the CFD-3D modeling and calibration of the DF combustion process, using a commercial software. The effects on combustion stability and emissions of different NG-H2 mixtures (six blends with 5%, 10%, 15%, 20%, 25%, and 30% by volume of hydrogen) are numerically investigated at a low load (BMEP = 2 bar, engine speed 3000 rpm). The results of the CFD-3D simulations demonstrate that NG-H2 blends are able to decrease strongly CO, UHC, and CO2 emissions at low loads. Advantages are also found in terms of thermal efficiency and NOx emissions.