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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.

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.

In this technical note, the electrolysis of a synthetic alkaline electrolyte was carried out at different temperatures varying between 10°C and 80°C and the effect of temperature on the rate of hydrogen production was studied. It was found that at a higher temperature of the electrolyte the rate of production of hydrogen was higher. However, the rise in the efficiency of the production of hydrogen was not significant at higher temperatures.

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Abstract In order to produce process heat for drying of agricultural, textile, marine products, heating of buildings and re-generating dehumidify agent, solar energy is one of the promising heat sources for meeting energy demand without putting adverse impact of environment. Hence it plays a key role for sustainable development. Solar energy is intermittent in nature and time dependent energy source. Owing to this nature, PCMs based thermal energy storage system can achieve the more popularity for solar energy based heating systems. The recent researches focused on the phase change materials (PCMs), as latent heat storage is more efficient than sensible heat storage. In this paper an attempt has been made to present holistic view of available solar air heater for different applications and their performance.

Fossil fuels are sharing a large portion of energy demand. Conventional energy sources emit a huge amount of greenhouse gas into the atmosphere, which creates energy and environmental challenges for the ecosystem. To fulfill the world energy demand and to support environmental as well as economic development in a sustainable way, with the utilization of technological advancement of renewable energy resources, algae are presently believed as most adaptable feedstock materials for bioenergy production. Algae has a high fixation rate of atmospheric carbon dioxide which supports to fast growth rate with high productivity per unit area in the form of renewable algal biomass. The present article aims to elaborate on the three generations of biofuels, sustainable microalgae biomass production, cultivation systems, and a wide range of growth parameters. The microalgae harvesting methods and their challenges are also discussed, with a special focus on lipid extraction methods and future r recommendations. The upstream and downstream processes of microalgae could help to harness the microalgae energy in an eco-friendly manner and will help in achieving overall sustainable development.