Waste to energy conversion for a sustainable future

Energy and environmental analysis of a condensate recovery thermal energy storage for the building cooling system

In the pursuit of sustainability and reduced environmental impact, waste-to-energy conversion methods are gaining importance. This study investigates the untapped potential of air-conditioning (AC) condensate as a source of chilled energy in AC systems of varying cooling capacities expressed in tons of refrigeration (TR) including 10 TR, 25 TR, and 50 TR. Field assessments revealed daily condensate generation of 37-148 L at 15 ± 1 °C, indicating significant cooling potential for energy recovery. Waste coconut oil (WCO) is proposed as a phase change material (PCM) for this purpose, aiming to examine its thermal characteristics and effectiveness for energy storage. Characterization of WCO reveals a latent heat of 101 J/g and a phase transition temperature of 22.1 °C. Thermal degradation occurs between 346 and 462 °C, while stability is maintained below 60 °C. WCO exhibits solid thermal conductivity of 0.181 W/mK at 10 °C and liquid conductivity of 0.175 W/mK at 30 °C, with specific heat capacities of 1.19 J/g K (solid) and 2.43 J/g K (liquid), ensuring efficient heat transfer during phase change. A pilot experiment examines the charging and discharging dynamics of WCO. It achieves complete solidification in 160 min at a freezing temperature of 21.3 °C, with 1.1 °C supercooling. During melting at ambient conditions (32 ± 1 °C), it takes 92 min, with a melting temperature of 21.9 °C. The study extends to evaluate the reduction in environmental impact through life cycle assessment (LCA). The significant impact values such as acidification, eutrophication, ozone depletion, fossil depletion, climate change, and metal depletion are calculated using the ecoinvent database. Overall, our study underscores the promise of WCO-based energy recovery systems in advancing sustainability efforts within the realm of air conditioning.

Recent progress and new insights on semiconductor heterojunctions powered photocatalytic desulphurization: A review

Desulphurization of fossil fuels is a critical process in reducing the sulphur content from environment, which is a major contributor to atmospheric pollution. Traditional desulphurization techniques, while effective, often involve high energy consumption and the use of harsh chemicals. Recently, photocatalytic desulphurization has emerged as a promising, eco-friendly alternative, leveraging the potential of photocatalysts especially semiconductor heterojunctions to enhance photocatalytic efficiency. This review comprehensively discusses the significance and mechanism of photocatalytic desulphurization reactions, designing of various heterojunctions such as conventional, p-n, Z-scheme and S-scheme, their charge transfer mechanism and properties and their contribution to the photocatalytic desulphurization activity. Heterojunctions, formed by combining different semiconductor materials, facilitate efficient charge separation and broaden the light absorption range, thereby improving the photocatalytic performance under visible light. Furthermore, the recent advancements in the heterojunction systems in the field of photocatalytic desulphurization activity have been discussed in detail and summarized. The current limitations and challenges in this particular field are also explored. The paper concludes with an outlook on future research directions and the potential industrial applications of heterojunction-powered photocatalytic desulphurization, emphasizing its role in achieving cleaner energy production and environmental sustainability.

Principles and Methods for Improving the Thermoelectric Performance of SiC: A Potential High-Temperature Thermoelectric Material

Thermoelectric materials that can convert thermal energy to electrical energy are stable and long-lasting and do not emit greenhouse gases; these properties render them useful in novel power generation devices that can conserve and utilize lost heat. SiC exhibits good mechanical properties, excellent corrosion resistance, high-temperature stability, non-toxicity, and environmental friendliness. It can withstand elevated temperatures and thermal shock and is well suited for thermoelectric conversions in high-temperature and harsh environments, such as supersonic vehicles and rockets. This paper reviews the potential of SiC as a high-temperature thermoelectric and third-generation wide-bandgap semiconductor material. Recent research on SiC thermoelectric materials is reviewed, and the principles and methods for optimizing the thermoelectric properties of SiC are discussed. Thus, this paper may contribute to increasing the application potential of SiC for thermoelectric energy conversion at high temperatures.

Get the win-win: Sustainable circular model of 'generation-value-technology' of industrial solid waste management

The management of industrial solid waste (ISW) and promoting sustainable circular development of the industrial economy is an urgent priority today. Therefore, this article constructs a sustainable circular model of 'generation-value-technology' of ISW management through the lens of industrial added value (IAV) and technology level. Also, the importance of the role of government is considered in the model. Based on actual data of China, this article simulates the future trend of the model using a system dynamics approach. The chief findings of the study are as follows: (1) under the current policy, China's future industrialization is increasing and the technological level of industrial enterprises is rising, but this is accompanied by a climb in ISW generation. (2) The win-win situation of ISW decrease and IAV increase can be achieved through enhanced information disclosure, technology innovation and government incentives. (3) Government subsidy should be oriented towards supporting technology innovation in industrial enterprises while reducing the proportion of incentives for ISW management results. Based on the results, this study proposes targeted policy implications for government and industrial enterprises.

Impact of ZnO nanoparticles as additive on performance and emission characteristics of a diesel engine fueled with waste plastic oil

Neat waste plastic oil (WPO) application as a fuel in engines reduces BTE and increases deleterious emissions of CO, UHC, NOx, and smoke due to the presence of insufficient oxygen and unbreakable hydrocarbon chains in WPO. Present investigation was performed to evaluate the impact of ZnO nanoparticles on the performance and emission characteristics of a diesel engine operated with the waste plastic oil (WPO20) blend. The objective of doping ZnO nanoparticles with WPO20 was to enhance the oxidation reaction and heat transfer rate between fuel droplets during combustion, which aids in completing the combustion. The sol-gel technique was adopted to successfully synthesize the ZnO nanoparticles using zinc acetate (Zn(CH₃CO₂)₂.2H₂O) and sodium hydroxide (NaOH) precursors. The structure and morphology of resulted particles were studied by XRD and FESEM tests. Both results indicate the stable formation of ZnO, and exhibit the crystallinity nature, spherical surface, and size consistency. The synthesized ZnO nanoparticles were infused in WPO20 blend in the amounts of 50, 100, and 150 ppm with the aid of the ultrasonication technique. Engine test was conducted with diesel fuel, WPO20 blend, and nano-infused fuels at a constant speed of 1500 rpm under various loads. The disparities in performance and emission characteristics were examined and compared with pure diesel fuel. The findings demonstrated that adding nanoparticles to WPO20 significantly lowers the smoke, CO, UHC, and NOx emissions and simultaneously improves the BTE and decreases the BSFC of the diesel engine. Optimum results were obtained for 100 ppm concentration of ZnO nanoparticles. Reduction of smoke by 11.86%, CO by 5.7%, UHC by 28%, and NOx by 14.93%, along with the enhancement of BTE by 2.47%, were noticed at maximum load with 100 ppm particles. Based on the test results, it is concluded that ZnO nanoparticles can be used as a suitable additive in WPO blends to improve the overall engine characteristics. Further scope of the present work is to study the effect of organic nanoparticles with WPO on engine behaviour, the detailed combustion of nanoparticles infused WPO, and the nanoparticles doped WPO on engine wear and corrosion.

Biochar and bio-oil fuel properties from nickel nanoparticles assisted pyrolysis of cassava peel

Direct biomass usage as a renewable fuel source and substitute for fossil fuels is discouraging due to high moisture, low energy density and low bulk density. Herein, thermogravimetric analysis (TGA) was conducted at various heating rates to determine peak decomposition temperatures for the dried cassava peels (DCP). The influence of pyrolysis temperature (300, 400, 500 and 600 °C) and heating rates (10, 20 and 30 °C/min) on the nickel nanoparticles catalyzed decomposition of DCP to produce biochar, bio-oil and biogas was investigated and characterized. The results revealed higher biochar (CBC) yield of 68.59 wt%, 62.55 wt% and 56.92 wt% at lower pyrolysis temperature of 300 °C for the different heating rates of 10, 20 and 30 °C/min. The higher carbon content of 52.39, 53.30 and 55.44 wt% was obtained at elevated temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, respectively. At the pyrolysis temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, the optimum yield of bio-oil (24.35, 17.69 and 18.16 wt%) and biogas (31.35, 42.03 and 46.12 wt%) were attained. A high heating value (HHV) of 28.70 MJ/kg was obtained for the biochar at 600 °C. Through the TGA, FTIR and HRSEM results, the thermal stability, hydrophobicity and structural changes of DCP and CBC samples were established. Similarly, the thermal stability of CBC samples increased with increasing pyrolysis temperature. Biochar with optimum fuel properties was produced at 600 °C due to the highest carbon content and high heating value (HHV). Improved kinematic viscosity (3.87 mm²/s) and density (0.850 g/cm³) were reported at the temperature of 300 °C and heating rate of 30 °C/min, while a higher pH (4.96), HHV (42.68 MJ/kg) and flash point (53.85 min) were presented by the bio-oil at the temperature of 600 °C and heating rate of 30 °C/min. Hence, DCP produced value-added biochar and bio-oil as renewable energy.

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Nickel nanoparticles successfully catalyzed the pyrolysis of CP biomass.

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Temperature and heating rates affected the yield of pyrolysis products.

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Fixed carbon content increased rapidly with temperature increase.

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The HHV of both biochar and bio-oil was higher than the DCP biomass.

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The fuel properties of biochar and bio-oil improved rapidly through NiNPs catalyzed pyrolysis.