• Energy Research

Rapid growth in industrialization has led to high dependency of reliable electric power source for its operation. On the contrary, thermal power plants expel pollutants consisting of hazardous gases that result in degradation of environment and ecosystem. Thus, utmost importance is to generate clean and efficient energy from power plant. This current article resolves the problem of sustainable power production using coal-based thermal power plants, by integrating gasification technologies to the system. The performance of thermal power plant in terms of emission is numerically analyzed with varying gasifier pressure, air-fuel ratio, steam-fuel ratio and flue gas-fuel ratio. Numerical simulation of the gasification cycle with varying parameters is carried out using MATLAB. Optimum performance at gasifier pressure of 2 bar and the steam-fuel ratio of 0.25 was observed with relative air-fuel of 0.075. With increasing flue gas-fuel ratio from 0.25 to 1.00, although the mole fractions of components of syngas don’t differ much, the heating value and cold-gas efficiency of syngas produced decreases for each fuel. Considering the emissions, simulated results present co-gasification as better option over conventional systems. A reduction of two-third in kg of CO2 released per kg of fuel was observed with almost three-fourth decrement in kg of CO2 per kWh of power produced. Also, zero SOx and NOx emissions were observed compared to coal based thermal power plants. It is noted that optimum performance of gasification system at gasifier pressure of 2 bar, air-fuel ratio of 0.1, steam-fuel ratio of 0.25 and flue gas-fuel ratio of 1.00. The proposed cycle presents itself suitable for further research and its application to coal based thermal power plants, providing potential towards supplementary power generation and cleaner exhaust. This research would also significantly contribute to achieve sustainable development goals.

Abstract Dry anaerobic digestion (DAD) is an attractive method for the stabilization of solid organic waste with high solid concentration (22–40%). This article provides different aspects for bio-energy production through dry anaerobic digestion suggested by different researchers. Basic fundamental aspects like reactions occurring in the process, microbial species involved in the process, effect of feedstocks and operational parameters like pH, temperature, C/N ratio, VFA concentration, etc. with types of reactors are summarized. A number of scenarios and the effect of changing individual parameters of the environmental impacts of dry anaerobic digestion process for biogas production are considered. Mobility of mass nutrient and energy flow in the above said process are also parts of this review article. We conclude that long term research and development for improvement and optimization of operational parameters in dry anaerobic digestion is necessary.

Abstract Phase change materials (PCMs) utilized for thermal energy storage applications are verified to be a promising technology due to their larger benefits over other heat storage techniques. Apart from the advantageous thermophysical properties of PCM, the effective utilization of PCM depends on its life span. Moreover, PCMs which are utilized for different solar thermal energy storage applications are required longer thermal and chemical stability for the extended performance of a system. This review shows the in-depth details on thermal stability and reliability of different PCMs such as organic, inorganic, eutectics, and composites materials for heat storage applications. Different methods for measuring the thermophysical properties along with the classification of PCMs based on applications and temperature ranges have been discussed. This paper also covers the selection criteria and commercial viability of PCMs for different domestic and industrial applications. In addition to this, the effect of thermal cycle testing on the properties of different organic, inorganic, eutectic, and composite PCMs has been summarized. The present article can be highly useful for researchers and practice engineers in the areas related to thermal energy storage applications.

Water hyacinth is a rapidly growing troublesome aquatic weed plant, which causes eutrophication in water bodies and irreversible damage to the ecological system. In this work, we have investigated the water hyacinth biomass (WHB) hydrolysis efficacy of dilute alkaline (DA) pretreatment followed by biological pretreatment with white-rot fungus Alternaria alternata strain AKJK-2. The effectiveness of the dilute alkaline (DA) and biological pretreatment process on WHB was confirmed by using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectrophotometer (FTIR), and was further visualized by Scanning Electron Microscope (SEM) and Confocal Laser Scanning Microscopy (CLSM). XRD spectra showed the increase in the crystallinity of pretreated samples, attributed to the elimination of amorphous components as lignin and hemicellulose. FTIR peak analysis of pre-treated WHB showed substantial changes in the absorption of cellulose functional groups and the elimination of lignin signals. Scanning electron microscopy (SEM) images showed firm, compact, highly ordered, and rigid fibril structures without degradation in the untreated WHB sample, while the pretreated samples exhibited loose, dispersed, and distorted structures. XRD indices (Segal, Landis, and Faneite), and FTIR indices [Hydrogen bond intensity (HBI); Total crystallinity index (TCI); and Lateral order crystallinity (LOI)] results were similar to the aforementioned results, and also showed an increase in the crystallinity both in alkaline and biological pretreatments. Alkaline pretreated WHB, with these indices, also showed the highest crystallinity and a crystalline allomorphs mixture of cellulose I (native) and cellulose II. These results were further validated by the CLSM, wherein fluorescent signals were lost after the pretreatment of WHB over control. Overall, these findings showed the significant potential of integrated assessment tools with chemical and biological pretreatment for large-scale utilization and bioconversion of this potential aquatic weed for bioenergy production.

An experimental study was performed to evaluate the comparative efficiency of bio-flocculant (waste egg shell), laboratory available calcium carbonate (LACC) and alum (Al2 (SO4)3) for harvesting of unicellular microalga, Chlorella pyrenoidosa. The influence of pH on zeta potential (ζ) was also studied to explain the chemistry of flocculation process. The maximum harvesting efficiency (99%) was obtained with alum with deformities in algal cell surfaces. Waste egg-shell material is developed as a low-cost bio-flocculant for harvesting of Chlorella pyrenoidosa using 100 mg egg-shell bio-flocculant/L and 100 mg LACC/L, zeta potential analysis was completed to further understand the chemistry of harvesting efficiency over the different ranges of pH (2.0, 4.0, 6.0, 8.0, and 10.0). The optimized range for harvesting efficiency (HE) of pH is 4.0-8.0 for both flocculants. Maximal harvesting efficiency was achieved at pH 4.0 (99%) and pH 8.0 (95%) with bio-flocculant and LACC respectively. Hence, bio-flocculant based harvesting method is found as the best way to dewatering the algal biomass from aqueous medium with entire and intact algal cell surface with environment friendly and cost-effective approach.

Most of the Indian rural area is electrified now, but the gap between supply and demand is much greater and increasing due to rapid industrial growth and increase in rural as well as urban living standards. That cause the extra burden on power grid. In order to reduce the burden on the national grid, India is moving fast towards distributed generation, and various studies show that renewable-based micro-grid is a preeminent alternative for decentralized energy generation. Most of the Indian population live in rural areas with access to wide varieties of alternative energy sources (wind, solar, hydro, biomass, etc.). Therefore, to reduce the dependency on heavily loaded power grid, a hybrid renewable energy system is required by utilizing the locally available sources, which incorporates more than one source of energy by combining the benefits and strength of one source to complement each other. This paper proposed a PV-Biomass-Grid-based optimal micro-grid system, based on locally available resources in Kashmir region of Jammu and Kashmir, India. In the proposed micro-grid, load is served on the basis of priorities to employ minimum burden on the grid and increase the use of renewable resources. The overall goal of the study is to minimize the cost of energy and maximize the energy output from hybrid renewable energy system. Extra electricity generated beyond the load demand would be supplied to grid. In this way, system energy cost is reduced with improvement in electrical system and reducing the environmental impact.

This article offers a trend of inventions and implementations of photocatalysis process, desalination technologies and solar disinfection techniques adapted particularly for treatment of industrial and domestic wastewater. Photocatalysis treatment of wastewater using solar energy is a promising renewable solution to reduce stresses on global water crisis. Rendering to the United Nation Environment Programme, 1/3 of world population live in water-stressed countries, while by 2025 about 2/3 of world population will face water scarcity. Major pollutants exhibited from numerous sources are critically discussed with focus on potential environmental impacts & hazards. Treatment of wastewater by photocatalysis technique, solar thermal electrochemical process, solar desalination of brackish water and solar advanced oxidation process have been presented and systematically analysed with challenges. Both heterogenous and homogenous photocatalysis techniques employed for wastewater treatment are critically reviewed. For treating domestic wastewater, solar desalination technologies adopted for purifying brackish water into potable water is presented along with key challenges and remedies. Advanced oxidation process using solar energy for degradation of organic pollutant is an important technique to be reviewed due to their effectiveness in wastewater treatment process. Present article focused on three key issues i.e. major pollutants, wastewater treatment techniques and environmental benefits of using solar power for removal of pollutants. The review also provides close ideas on further research needs and major concerns. Drawbacks associated with conventional wastewater treatment options and direct solar energy-based wastewater treatment with energy storage systems to make it convenient during day and night both listed. Although, energy storage systems increase the overall cost of the wastewater treatment plant it also increases the overall efficiency of the system on environmental cost. Cost-efficient wastewater treatment methods using solar power would significantly ensure effective water source utilization, thereby contributing towards sustainable development goals.

Lignocellulosic biomass generated from different sectors (agriculture, forestry, industrial) act as biorefinery precursor for production of second-generation (2G) bioethanol and other biochemicals. The integration of various conversion techniques on a single platform under biorefinery approach for production of biofuel and industrially important chemicals from LCB is gaining interest worldwide. The waste generated on utilization of bio-resources is almost negligible or zero in a biorefinery along with reduced greenhouse gas emissions, which supports the circular bioeconomy concept. The economic viability of a lignocellulosic biorefinery depends upon the efficient utilization of three major components of LCB-cellulose, hemicellulose and lignin. The heterogeneous structure and recalcitrant nature of LCB is main obstacle in its valorization into bioethanol and other value-added products. The success of bioconversion process depends upon methods used during pre-treatment, hydrolysis and fermentation processes. The cost involved in each step of the bioconversion process affects the viability of cellulosic ethanol. The lignocellulose biorefinery has ample scope, but much-focused research is required to fully utilize major parts of lignocellulosic biomass with zero wastage. The present review entails lignocellulosic biomass valorization for ethanol production, along with different steps involved in its production. Various value-added products produced from LCB components were also discussed. Recent technological advances and significant challenges in bioethanol production are also highlighted in addition to future perspectives.