Summary
In this study, the simultaneous use of nanofluid and phase changing material as a coolant for photovoltaic fluid collector system and its effects are investigated experimentally. Two types of ...nanofluid are taken for the consideration, that is, ZnO and CuO, which are water‐based fluid. The experiments are performed in five different types of photovoltaic thermal system conventional: PT, PVT (ZnO), PVT (CuO), PCM medium (PVT/PCM/ZnO), and PCM medium (PVT/PCM/CuO). The results are obtained for surface temperature, energy, and thermal efficiency, and it is compared with each other. Further, the effect of the nanofluid as the effective alternative for pure deionized water is measured. From the results, it is evident that the PVT/PCM/CuO system minted 15% high electric output compared with convention module. Furthermore, the addition of the CuO nanofluid increases the thermal output significantly up to 8% for PVT and 12% for PCM without energy consumption. It also found that the nanofluid increases the overall energy efficiency of the system compared with convention PV.
The use of nanofluid ZnO and CuO with PCM was proposed. It is identified that the nanofluid not only enhances the power output but also contributes to reducing the surface temperature to appreciable levels. Furthermore, PCM medium with nanofluid can be an appropriate selection to improve the cooling in the PVT system without any extra energy consumption.
Highlights
Simplified PVT‐PCM system has been developed with nanofluids.
Novel method has been proposed to incorporate the ZnO and CuO on PCM/PVT.
The nanofluid (ZnO and CuO) in PCM reduces the surface temperature by 43% and 47%.
Incorporation of PCM and nanofluid improved the electrical efficiency by 16% and electrical output by 15%.
The cumulative thermal output for PCM is increased by 46% compared with the PV module.
Nanofluid CuO shows a profound effect comparing to ZnO
•Analyzing the recent developments in pyrolysis processes of microalgae.•Mechanism of the various types of pyrolysis was summarized.•Biochemical composition was discussed in detail.•Microwave ...assisted pyrolysis has achieved more significance than other process.•Quality of the bio-oil in catalytic pyrolysis was higher than thermal pyrolysis.
Algae become reasonable feedstock in recent times for biofuel production as they are environmentally benign, sustainable and renewable biomass. Biofuels are produced from algal biomass by chemical, biochemical, and thermochemical methods. Among the thermochemical techniques, pyrolysis is a well-known method involving high temperature and high pressure to produce biochar and bio-oil from numerous algal biomasses. Therefore, this review was undertaken to collate and discuss different pyrolytic processes employed for the conversion of algal biomass into biochar and bio-oil production. At the outset, different pyrolysis methods slow pyrolysis, fast/flash pyrolysis, catalytic pyrolysis, microwave assisted pyrolysis and hydropyrolysis operated for the conversion of various microalgae and cyanobacteria into biochar and bio-oil were reviewed using copious literature. Further, challenges arisen out of using above-said pyrolysis methods were critically highlighted to pave the way to choose an appropriate pyrolysis method for obtaining desirable quantity and quality of bio-oil from algae.
Summary
Hybrid photovoltaic thermal system is an effective method to convert solar energy into electrical and thermal energy. However, its effectiveness is widely affected due to the high temperature ...of photovoltaic panel, and it can be minimized by employing nanofluids to the PV/T systems. In this research, the effect of various nanoparticles on the PV/T systems was studied experimentally. The nanofluids Al2O3, CuO, and multiwall carbon nanotube (MWCNT) were dispersed with water at different volume fractions of 0, 0.5, 1, 2.5, and 5 (vol%) using ultrasonication process. The effect of nanomaterials on viscosity and density was classified. All tests were carried out in an outdoor laboratory setup for calibrating the PV temperatures, thermal conductivity, electrical power, electrical efficiency, and overall efficiency. In addition, the energy analyses were also made to estimate the loss of heat owing to the nanofluids. Results show that use of the nanofluid increased the electric power and electrical efficiency of PV/T compared with water. Furthermore, MWCNT and CuO reduced the cell temperature by 19%. Consequently, the nanofluids MWCNT, Al2O3, and CuO produced the impressive values of 60%, 55%, and 52% increase in an average electrical efficiency than conventional PV. Particularly, the MWCNT produced superior results compared with other materials. It is evidently clear from the result that the introduction of the nanofluid increases the thermal efficiency without adding any extra energy to the system. Moreover, insertion of Al2O3, CuO, and MWCNT on PV/T system increases the exergy efficiency more than conventional PV module.
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Thermochemical methods namely pyrolysis, gasification/hydrothermal gasification, combustion, hydrothermal liquefaction and hydrothermal carbonization are widely practiced to convert ...algal biomass into fuels. Among the methods, pyrolysis, and hydrothermal liquefaction are most commonly practised to convert numerous algal biomasses into bio-oil and/or biochar to substitute crude oil in petroleum refinery. In this regard, this review is focused on the conversion of various microalgal; and cyanobacterial biomasses into bio-oil, and solid char products through pyrolysis and hydrothermal liquefaction. Initially, pyrolysis and hydrothermal liquefaction of algal biomass on bio-oil and biochar yield have been reviewed. As the composition and yield of bio-oil from algae depends on the reaction temperature, detailed account of the impact of temperature on the quantity and quality of bio-oil and solid char obtained from pyrolysis and hydrothermal liquefaction were comprehensively presented in the review. Eventually, this article provides opportunities and scope in the pyrolysis and hydrothermal liquefaction of algae for further research.
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Considering the present energy demand and industrial growth, finding a potential sustainable energy source is crucial. Among renewable fuels, hydrogen is considered to be the primary ...choice as it offers substantial benefits over other conventional fuels. Hydrogen can be generated from waste substrates, is cleaner, and has the highest energy density when compared to conventional fuels. Hydrogen production, particularly biological hydrogen production, is believed to be cost-efficient as it can be successfully performed in ambient conditions with easy operational techniques in an environmental-friendly manner. This review summarizes the different routes of biological hydrogen production including biophotolysis, indirect photolysis, dark fermentation, photofermentation, and microbial electrolysis. Further, leading microorganisms involved in biohydrogen production, such as Clostridium spp., Enterobacter spp., Bacillus spp., Escherichia coli, thermophilic lactic acid bacteria, and Klebsiella spp., along with the molecular approaches employed for the enhancement of biohydrogen production are discussed. In addition, a thorough techno-economic analysis of factors involved in the scale-up of hydrogen production is carried out.
Turbojet engines play a crucial role in air transportation, providing superior thrust-to-weight ratios and lower NOx emissions compared to gas turbine engines, particularly at high speeds. Although ...they are efficient, environmental concerns and rising fuel costs have led to the exploration of alternative fuels. This study examines the use of green gaseous fuels, specifically hydrogen, in the SR-30 turbojet engine. Engine performance, combustion characteristics, and emissions were measured across a range of speeds from 40,000 to 75,000 rpm, without altering the combustion chamber. Hydrogen was injected into the engine air inlet manifold at a constant volume. The hydrogen used in the study was a mixture of 75% biogas and 25% hydrogen by volume. Due to hydrogen's high flammability, a flashback arrestor was employed to prevent backfire. The introduction of gaseous fuel increased maximum thrust by 4.5% and reduced fuel consumption by 2.2%. The addition of hydrogen improved thrust and combustion efficiency while lowering specific fuel consumption and unburned fuel. However, the presence of nitrogen and hydrogen may lead to increased NOx emissions. By optimizing fuel injection strategies, it is possible to mitigate NOx emissions, thereby improving engine efficiency and minimizing environmental impact. The study concludes that gaseous fuels like hydrogen provide a promising alternative for enhancing turbojet engine performance and reducing emissions.
•Hydrogen was tested in the SR-30 turbojet engine without modifications with gaseous fuel.•Inclusion of gaseous fuel increases maximum thrust by 4.5% along with 2.2% reduction in fuel flow rate.•Hydrogen increases NOx emissions due to high combustion temperatures.•Injecting hydrogen via air intake is not effective.
Biofuel is an attractive alternative to fossil fuels since it is renewable and biodegradable—it is mainly made from edible and non-edible sources. Globally, the usage of renewable biofuels is ...expected to rise quickly. The rising production and use of biofuel has prompted an examination of its environmental impact. Biodiesel is a fatty acid methyl ester generated from sustainable lipid feedstock that substitutes petroleum-based diesel fuel. Non-food oils, such as Jatropha, waste cooking oil, and by-products of vegetable oil from refineries provide inexpensive feedstock for biodiesel manufacturing. Due to its increased oil yield, adequate fatty acid content, tolerance to various agro-climatic conditions, and short gestation period, Jatropha may be one of the most promoted oilseed crops worldwide. Furthermore, Jatropha can provide several economic and agronomic advantages because it is a biodegradable, renewable plant. This study examines whether Jatropha can be considered as the most preferable biofuel in the future. The study begins with an overview of current fuels, including their classifications, dynamic changes in consumption, advantages, and cross-examining the limitations to identify the significance of bringing an alternate fuel. Then we elaborate on the outlook of the Jatropha crop, followed by evaluating its availability, opportunity, and advantages over other biofuels. Subsequently, the extraction methods, including the transesterification process and integration methods for improving the efficiency of Jatropha fuel, are also reviewed in the paper. We also assess the current stage of Jatropha cultivation in different countries with its challenges. The review concludes with future perspectives and directions for research.
•A gas composition, including Hydrogen, Methane, and EGR, has been investigated in diesel engines.•All gasses reported superior combustion, thermal efficiency, and output brake power due to the heavy ...influence of hydrogen.•gasses with higher nitrogen levels lead to poor thermal efficiency and increased NOx emission.•Gasses reduced the formation of CO, CO2, and NOx when they operate at the optimized flow conditions.
Hydrogen and methane as secondary fuels in diesel engines can be promising solutions to meet energy demand. The current study investigated the effect of the specialty gases of different compositions on diesel engine performance and exhaust gases. Four gases with various compositions of exhaust gas recirculation (Carbon monoxide, Carbon dioxide, and Nitrogen) and fuels (Hydrogen and Methane) were used at various mass flow rates of 10, 20, and 25 LPM (liter per minute), and various engine speeds of 2000, 2500, 3000, and 3500 rpm (revolutions per minute). The procured results revealed that adding specialty gases improved brake thermal efficiency and power. Similarly, the brake-specific fuel consumption was also massively retarded compared to diesel due to the influence of the hydrogen and methane composition. However, the fuel with the higher nitrogen reported less BTE (brake thermal efficiency) and comparatively higher exhaust gas temperature owing to the higher presence of nitrogen in their composition. Regarding emissions, including exhaust gas recirculation dropped the formation of pollutants efficiently compared to diesel. Among various fuels, Case 1 (30 % H2, 5 % CH4, 5 CO2, and 60 % CO) reported the lowest emission of NOx, and Case 2 (25 % H2, 5 % CH4, 5 CO2, 30 % CO, and 35 % N2) of CO and CO2 emissions. Generally, specialty gases with a variable composition of exhaust gas recirculation gases can be a promising sustainable replacement for existing fossil fuels.
Polycyclic aromatic hydrocarbons (PAHs) are widely present in the atmosphere and primarily originate from the incomplete burning of fossil fuels and biofuels. Exposure to PAHs leads to harmful ...effects on human health and the environment. Diesel engines are a major source of PAH production in the transportation sector. Various approaches have been employed to reduce PAH emissions from diesel engines, including the use of biodiesel, green gaseous fuels, exhaust gas recirculation, exhaust after-treatment, and genetically modifying biodiesel with nanoparticles. This review focuses on PAH emissions from different generations of fuels and examines the remedial control actions taken to mitigate PAH formation. The study underscores the necessity for effective regulation of emissions from diesel engines, especially in developing countries where the reliance on fossil fuels is significant. Biodiesel has shown promise in reducing PAHs and carcinogenic pollutants, with higher biodiesel concentrations resulting in lower PAH formation. Replacing diesel with biodiesel and optimizing engine operating conditions are feasible methods to reduce PAH levels in the atmosphere. The use of nanoparticles in fuel blends and higher oxygen content in combustion chambers are also considered potential strategies for pollutant reduction. Additionally, the utilization of hydrogen and ammonia as secondary fuels has been explored as promising alternatives to fossil fuels. The study highlights the importance of further research on the presence of residual PAHs in the atmosphere and the implementation of strategies to curtail vehicular emissions.
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•PAHs emissions from several generation of the fuels and its remedial control action to reduce the formation of PAHs were discussed.•The need for proper regulation of emissions from diesel engines was discussed.•Utilization of the hydrogen and ammonia as the secondary fuel also reported as the promising replacement for the fossil fuels.•Introduction of the nanoparticles to the blends enhances the combustion quality, which reduces the pollutants.
