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Applying oxy-fuel combustion requires more advanced combustion control methods to avoid inadmissible high flam temperature. In fluidized beds and pulverized unites, enhanced heat transfer and recirculation flue gas are used. On other hand, higher oxygen concentration has pluses viz. better heat transfer, higher efficiency, compact setup and lower installation and operating costs. In pulverized power unites, pure oxy-fuel combustion is used with 100% O2 in the oxidant. In contrast, the highest experimental O2 % in oxy-fuel circulating fluidized bed (CFB) combustor is 70%. To the best of authors’ knowledge, there is no single CFB power plant operating under pure oxygen condition. In this work, we are aiming to use pure oxygen for oxy-CFB combustion, with new temperature controlling method for CFBs depending on combustion staging by fuel staging rather than using RFG. Fuel staging allows controlling combustion and varying SR. At the first stage, the used oxidant is 100% O2, and fuel is fed to achieve over SR (λ>1), where the excess oxidant absorbs heat and does not take a part in the reaction. The products of the first stage are reach of O2 and subsequently it is used as an oxidant for the second stage. For validation, a series of experiments are conducted using mini-CFB, and an oxidant of 100% O2 concentration is used with three SR ratios λ=1.25, 2.0, and 3.0. The resulted average temperatures along the riser for biomass are 1031°C, 950°C, and 798°C; and for coal 1129 °C, 1051 °C, and 961 °C respectively. The controlling of AFT with pure oxy-fuel combustion eliminates the recycled flue gas (RFG) in oxy-fuel CFB combustion and flue gas recirculation section; this simplifies the power plants’ design, fabrication and its installing-operating costs. Familiarising this concept can accelerate adapting oxy-fuel combustion in CFB power plant for Carbon Capturing and Sequestration (CCS). This contribution can commence and commercialise the third generation of oxy-fuel CFB combustion with zero recycled flue gas. Finally, the concept of controlling AFT by SR (λ) is validated experimentally.

Anaerobic digestion of lignocellulosic biomass has gained attention in recent years due to its increase availability and productivity. In this study, anaerobic mono- and co-digestion of three lignocellulosic biomass, viz. duckweed, switchgrass, and rice straw, were performed in 1 litre laboratory-scale batch reactors. The initial biochemical methane potential (BMP) test was performed at three different total solids concentrations (10%, 15%, 20%) and cattle dung: feedstock ratios (1:1, 1:1.5, 1:2) under mesophilic conditions (28–32 °C) for 36 days. Co-digestion of feedstocks at 1:1 ratio yielded better results than other cattle dung: feedstock ratios. Optimized physical parameters were further implemented for a scale-up co-digestion study of biogas potential from 4 m3 community-size biogas digesters. The investigation was performed for 60 days maintaining a hydraulic retention time (HRT) of 40 days, and a comparative analysis with mono digestion of cattle dung was also analyzed. Average daily biogas production for digester containing rice straw and cattle dung was 0.36 m3/kg-VS, whereas it was 0.34 m3/kg-VS and 0.32 m3/kg-VS for switchgrass and duckweed, respectively. An overall comparative analysis of the biogas production and its composition for both BMP tests and continuous processes are discussed in this work.

The present study focuses on enhancing fluidization capacity and optimizing a lab-scale gas-solid vortex reactor (GSVR) without-slit numerically. This reactor has been developed without-slit, and the air-inlets of the rectangular cross-section are used instead of circular cross-section. The numerical investigation has been carried out to analyze two fluids (gas-solid) flow patterns and heat transfer phenomena in GSVR without-slit, using a commercial software ANSYS FLUENT 14.5 by implementing Eulerian-Eulerian approach for gas-solid phases. In the present study, numerical simulations have been carried out for distinct length to diameter ratios (L/D) of 0.2, 0.8, 1.0, and 1.2, assuming the same chamber diameter of 240 mm. In contrast, the chamber diameter is fixed to 240 mm. Hence, the reactor capacity of lab scale GSVR reactor is enhanced from 500 g to 3370 g by increasing L/D of 0.2 to 1.2.

The rise in mean atmospheric temperature resulting from the emissions of greenhouse gases, especially CO 2 , has become a widespread concern in the recent years. This awareness of increase in greenhouse gas emissions has resulted in the development of new technologies which would lower emissions of CO 2 from flue gases. The purpose of this study is to investigate the performance of bubbling fluidized bed for CO 2 adsorption to mitigate CO 2 from flue gas. Adsorption of CO 2 had been carried out onto zeolite 4A, zeolite 5A, zeolite 13X and activated carbon at a pressure up to 4 bars. The effects of adsorbent mass on breakthrough time, gas velocity, adsorption isotherm, thermodynamics and heat transfer characteristics were also investigated during the continuous operation of the bubbling fluidized bed. As flow rate increased, the breakthrough curves become steeper and reached the breakthrough quickly due to the residence time of the adsorbate in the column, which was long enough for adsorption equilibrium to be reached at high flow rate. The experimental data were fitted with isotherm models like Langmuir and Freundlich isotherm model. It was found that the Langmuir model fit well with the zeolites based adsorbent and Freundlich model fit well with activated carbon. The experimental results permitted the determination of adsorption capacities of the adsorbents and showed that there is an improvement in the adsorption capacity using fluidized bed due to a better gas solid contact as compared to conventional fixed bed.

A critical review and analysis of co-gasification of coal/biomass blends is presented. Initially, the chemistry of gasification of coal and biomass has been described along with different models for pyrolysis of cellulose/biomass. The mechanistic issues of catalytic effect of alkali metals on coal char gasification have been reviewed. This is followed by literature review on gasification of coal/biomass blends in two parts, viz. thermogravimetric and fluidized bed gasification. First part deals with effects of operational parameters on char reactivity. Second part analyzes influence of these parameters on gasification chemistry and producer gas. Factors governing tar content in producer gas have been discussed. Finally, the literature on kinetic modeling of coal/biomass blends has been analyzed. Some new approaches in kinetic modeling of solid-state reactions have been discussed.

The absorber plate and outlet water temperature of a solar flat plate collector with straight riser and header arrangement is investigated. The effect of different operating parameters, viz., inlet water temperature, solar insolation, ambient temperature, and mass flow rate on the outlet water temperature and thermal efficiency were studied. Both the closed as well as open loop solar water heating system is considered for the present investigation. It is observed that the thermal efficiency of the solar water heating system increases with ambient temperature, solar insolation, and mass flow rate of water. However, thermal efficiency decreases as inlet water temperature increases. Numerical simulations were carried out using a 3-dimensional computational fluid dynamics (CFD) to predict the outlet water and absorber plate temperatures using the experimental values of solar insolation, ambient temperature and inlet water temperature within one hour interval. The CFD results were validated with the experimental results. It was found that the developed model could predict the outlet water and absorber plate temperature of the heating system with reasonable accuracy.

We report here the characterization of five biomass samples ( Impereta cylindrica, Eragrostis airoides, Typha angustifolia L., Arundinella khasiana Nees ex Steud, and Echinochloa stagnina (Retz.) P. Beauv) based on the proximate, ultimate and compositional analysis. The biomasses were examined physico-chemically and characterized to understand their compositional and structural properties. The moisture content was found to be highest in Typha angustifolia (13.951%) and lowest in Eragrostis airoides (8.275%). Ash content was seen to be maximum in Arundinella khasiana (8.12%) and minimum in Eragrostis airoides (3.660%). Derivative Thermogravimetric (DTG) peak was observed below 120 °C indicating the loss of water molecules from the biomass. Cellulose degradation occured between 350 °C to 500 °C. The maximum carbon content was visible in Typha angustifolia (52.895%) and minimum in Eragrostis airoides (41.024%). The FTIR spectra showed a range of peaks such as 3450 cm −1 , 2860 cm −1 , 1668 cm −1 , 1175 cm −1 , 1097 cm −1 , 7872 cm −1 , 625 cm −1 , 554 cm −1 etc. The cellulose content was found maximum in Eragrostis airoides (43.17%) and minimum in Echinochloa stagnina (24.90%). The results demonstrate that the collected lignocellulosic biomass could be potential candidate for bioethanol production.

Due to the complicated structure of lignocellulosic plant cell wall, their utilization for biogas production via anaerobic digestion has not been widely adopted. Alternative to this is to use aquatic plant materials as feedstock for biogas production. In this context, duckweed, an aquatic plant may prove to be a promising new energy source for bioenergy as well efficient CO 2 sequestration. This study entails a detailed characterization of duckweed to evaluate their potential as an alternate feedstock to cattle dung for biogas production. The duckweed was characterized for volatile matter, moisture content, ash content and carbon, hydrogen, and nitrogen (CHN) content. Property analysis of duckweed was also done by Fourier transform spectroscopy and thermogravimetric analysis. The volatile matter of duckweed was found to be 84.24± 0.2% with a lignin content of 12.2%, which is very encouraging for biogas production. Co-digestion of duckweed (DW) with cattle dung (CD) in varying ratios (DW:CD = 90:10, 75:25, and 50:50 respectively) in batch type anaerobic digesters was performed at 37 °C temperature for 55 days. The cumulative biogas production for CD (100%), DW/CD (90:10), (75:25) and (50:50) was found to be 11,620, 305, 11,695, and 12,070 mL, respectively, which indicated that duckweed can be a potential lignocellulosic feedstock when co-digested with cattle dung at an optimum ratio of 1:1. Methane content of the biogas from co-digested feedstock is comparable to the biogas from cattle dung alone.

In the present investigation a single cylinder, four-stroke, water-cooled, spark ignition (SI) engine was modified to operate as a raw biogas fueled SI engine. The engine was operated at wide-open throttle condition and at three deferent compression ratios (CR 8:1–CR 10:1) over a speed range of 1400–1700 rpm. The spark timing of the engine was set to MBT timing. The effect of CRs on the performance, combustion and emission characteristics of the engine was investigated and presented in this paper. It was observed that with increasing CR, the brake torque (BT), brake power (BP) and brake thermal efficiency (BTE) of the engine were increased. The maximum BT, BP and BTE of the engine were found to be 19.96 N-m, 2.92 kW and 28.68%, respectively, at CR 10:1. With increasing CR, the peak cylinder pressure increased and shifted toward the TDC. The maximum peak cylinder pressure at CR 10 was found to be 23.66 bar. With increasing CR, the rate of flame front propagation became faster and was higher at CR 10 for the biogas fueled SI engine. With increasing CR, the UHC emission was reduced, whereas the CO and NOx concentration were increased.

Power generation from solar photovoltaic (PV) plants depends on multiple factors such as solar radiance and ambient temperature. Effective monitoring and control of the energy generated with the solar PV plants may augment the complete performance of the system. The local controllers regulate switching between solar PV, local battery, community battery, and grid according to the availability of power in each system. The sensor data and user information are stored in the cloud that can be accessed with the Internet of Things (IoT) device for further computation. A Web-based graphical user interface (GUI) has been developed for appropriate monitoring and control of energy flow and also to enable the power pooling. The app gets information from the cloud on which various sensor’s data regarding energy pooling are stored by the local/community controllers, and it displays the information that is stored in the cloud. The primary task is to design and develop a Web-based application with sufficient data security. To secure the user data in the cloud, multi-factor authentication and symmetric key encryption are used for authorized access and data encryption. The basic model of the Web-based application is presented in this paper.

Owing to the non-uniform availability of solar radiation, designing of a latent heat storage found necessary so as to bridge the supply and demand gap. In the current investigation, the charging and discharging characteristics of a 10 MJ capacity, paraffin wax-based latent heat storage are analyzed numerically. Validations with experimental results showed reasonably good agreement following which parametric studies are conducted and detailed discussion on results are presented.

The exhaustive nature of fossil fuels and environmental concerns associated with greenhouse gases are the major causes of the paradigm shift from conventional vehicles to electric vehicles (EVs). The electrification of the transportation sector and the increasing popularity of the EVs have driven scientists and researchers to delve into charging stations. Underdeveloped charging infrastructure, optimal placement of charging stations, and charge scheduling in the charging stations are the major concerns for the large-scale deployment of EVs. Even few questions related to EVs, such as the vehicle price and driving range, can be partially solved with a well-developed charging infrastructure. Existing old infrastructure may bring severe limitations in the realization of the optimal placement of charging stations as EVs have not existed when the road and grid infrastructure have been developed. For the past few years, the studies associated with the optimal placement and sizing of EV charging stations have drawn the consideration of the researchers. The researchers have used different approaches, objective functions, and applied different optimization algorithms while dealing with the problem of charging station placement. The complex and dynamic nature of the problem has led researchers to apply different optimization algorithms for the solution of the problem. In this particular review study, the research works bearing on the charging infrastructure planning for the EVs are considered. Thus, this review work will endow the research community with the latest developments and research findings in the paradigm of charging infrastructure planning for EVs. This article is categorized under: Energy Infrastructure > Systems and Infrastructure Energy and Urban Design > Systems and Infrastructure Energy and Transport > Science and Materials Energy Systems Analysis > Science and Materials

The austenitic stainless steels are widely used in chemical, metallurgical, conventional, nuclear power plants and industrial applications due to their excellent corrosion resistance and formability. For welding plates of higher thickness, the submerged arc welding is a suitable technique, as it offers higher deposition rate, good bead shape and deeper penetration. To get a sound welded joint without defects, suitable welding parameters should be carefully chosen to weld austenitic stainless steel as they are sensitive to heat input. In this study, austenitic stainless steel plates were joined using double-sided submerged arc welding, and key welding parameters such as voltage, current and welding speed were established to get a defect-free joint. The effectiveness of double-sided welding is evaluated from microstructural and mechanical characterization. From the macroscopic examination, the two weld seams, i.e. initial run and second run intersect at the middle, which is an indication of the defect-free weld. The microstructure of the fusion zone consists of dendritic grains and coarse columnar grains. The microhardness tends to increase in the weld zone for initial weld run followed by second weld run and lowest in the middle of the weld seam. The result of the tensile test indicates that elongation of the welded joint surpasses that of parent metal elongation, and fracture occurs at base zone. The field emission scanning microscopy examination of the broken surfaces of the tensile sample reveals the nature of fracture mode is ductile. In this paper, heat input controlling method was successfully introduced for welding of austenitic stainless steels of higher thickness with a simple double-sided submerged arc welding (DSSAW).

This study has been performed to enhance the performance of the solar air heater (SAH) using copper tubes to the absorber plate. Thermodynamic analysis of the SAH with and without copper tubes attached to the absorber plate has been performed. The improvement potential, sustainability index, and waste energy ratio have also been studied. From the results, it has been found that the thermal and exergy efficiency of the absorber with copper tubes is higher as compared to the absorber without copper tubes for the same climatic conditions. The energy efficiency of the SAH with and without copper tubes absorber was ranged from 14.53 to 20.36% and 12.45–17.53% with an average of 18.26% and 16.29%, respectively in the natural convection mode. The exergetic efficiency was ranged from 1.2 to 1.939% and 0.95–1.53% with an average of 1.69% and 1.41%, respectively. Energy and exergy analysis of the SAH with copper tubes attached absorber have also been performed for the forced convection mode at varying air flowrate from 0.0166 to 0.058 kg/s. The maximum value of energy and exergy efficiency of the SAH was obtained as 62.8% and 5.848%, respectively at the airflow rate of 0.05 kg/s.

Pressurized circulating fluidized beds (PCFB) are subjected to various fluctuating conditions due to fluctuations in load demands owing to its vast utilization as a combination of heat and power generating unit. As such, analysis of transient heat transfers and hydrodynamics during these fluctuations in PCFB is very important. The present work includes experimental investigation on the transient behaviour of a PCFB unit during abrupt changes in operating pressure. The experiments are performed on a laboratory scale PCFB set up consisting of a stainless-steel riser of height 2 m and an inner diameter of 54 mm. The operating pressure is regulated by a pressure regulator and is measured using a piezo resistive pressure sensor attached to the inlet of the riser. Static pressures and temperatures are also measured along the riser column at various heights. Experiments are performed with 500 g sand as bed inventory at two operating pressure of 2 and 3 bar. Drastic changes in voidage values were observed mostly in the upper region of the riser column for transient conditions in the operating parameters. The experiments showed that with a sudden drop in operating pressure, the heat transfer coefficient momentarily increase and subsequently decrease steadily. The reverse is observed for a sudden increase in operating pressure.

The coupling of renewable energy systems has proven to be advantageous in achieving sustainable and reliable energy generation. In this study, the techno-economic and environmental assessment of a hybrid 1 kW solar photovoltaic (PV) plant (having battery backup) and a 3.5 kVA biogas fueled (BF) generator was investigated. The hybrid system was subjected to constant load conditions from 20% to 80% of the rated power conditioning unit (PCU), and energy shared by the combined systems was investigated. At lower loads, the photovoltaic system was sufficient to meet the demand. Whereas at higher loads, energy share from the biogas system was required for meeting the load demand. Economic analysis over a project lifetime of 25 years revealed a high positive net present value of $1562.15 with a Levelized cost of the energy value of $0.21/kWh for the hybrid system. A comparative financial analysis for the standalone solar photovoltaic system was also performed using the system advisor model (SAM). System advisor model analysis resulted in a positive net present value of $306.45 and a Levelized cost of the energy value of $0.15/kWh. The environmental analysis revealed net CO2 mitigation of 104.59 Tons, equivalent to an earned carbon credit of $2090.31 from the hybrid system.

The use of porous burner in combustion appliances finds widespread attention due to its inherent nature of low emission and high efficiency. This paper presents a finding on the effects of the porous medium (PM) configuration and operating parameters on the performance of a kerosene pressure stove equipped with Silicon Carbide (SiC) and Alumina (Al2O3) operating in the submerged combustion mode. The study covers three different diameter burners: 60 mm, 70 mm and 80 mm, and their thermal performances are assessed through thermal efficiency, emissions and radial temperatures at different air and fuel flow rates. The best performance is observed in the case of 70 mm diameter burner with a minimum of 44 ppm CO (carbon monoxide) and NOx (oxides of nitrogen) ∼1.5 ppm. An air flow rate range of 120–130 lpm is found optimum.

The intensification of interfacial mass, heat, and momentum transfer makes vortex chambers potentially interesting for the efficient drying of paddy, allowing shorter drying times and/or more compact equipment. The presence of a shell introduces particular challenges. Intraparticle diffusion limitations are strong and may reduce the advantage from intensified interfacial mass and heat transfer and the efficiency of air usage. Furthermore, high shear and normal stresses in the fast rotating particle bed may cause damage to the paddy shell, posing problems for transport and storage. With these specific aspects in mind, the use of vortex chambers for paddy drying is experimentally evaluated.

Porous media combustion (PMC) is relatively a new concept, and due to its inherent characteristics of high efficiency and low emissions, it has found wide applications in many practical systems like internal combustion engine (IC engine), water heater, LPG (Liquefied Petroleum Gas) stoves, etc. In this study, the concept of PMC has been employed in a kerosene pressure stove, and the usefulness of the media consisting of alumina (Al2O3) and silicon carbide (SiC) in terms of efficiency and emissions is investigated. Further, the conditions for optimum efficiency and emission are brought out through a systematic analysis with different burner geometry and exergy calculation. The major highlight of this study is that the highest efficiency of the stove with porous media is found to be ∼10% higher than the average thermal efficiencies of the stoves available in the Indian market.

The present study's main objective is to develop a best-performing gas-solid vortex reactor (GSVR) dryer observing at the effect of spiral versus conical chimney outlet in capacity enhancement. Three-dimensional computational fluid dynamics study of the GSVR model with spiral and the conical chimney has been conducted using a commercial software ANSYS FLUENT 14.5, applying an Eulerian-Eulerian approach for gas-solid. The fluidization capacity of the SL-GSVR drying chamber with a spiral chimney is enhanced by increasing chamber-length. In contrast, in the case of SL-GSVR with a conical chimney outlet, the fluidization capacity is increased by improving the diameter of the reactor, considering various operating parameters, such as air velocity, pressure, bed-thickness, temperature, and heat transfer coefficient. For the same input parameters, the solid loading capacity of the SL-GSVR with a spiral drying chamber is found to be 27% higher than the SL-GSVR with a conical-chimney outlet. Also, the capacity enhancement seems simpler and easy by using a spiral-chimney outlet due to its symmetric nature of construction.

Decentralized energy generation at community level is the need of the hour for meeting the increasing load demands. A pilot-scale 1 kW photovoltaic (PV) system was installed at Auniati Satra near IIT Guwahati for studying the effects of its operating parameters at different loading conditions corresponding to the environmental conditions prevalent in Guwahati, Assam (India). The PV system was subjected to constant electrical load both in standalone mode and grid-connected mode during the daytime at eight different loading conditions viz. 20%, 30%, 40%, 45%, 50%, 60%, 70% and 80% and half-hourly data of different parameters like solar insolation, PV energy, PV charge, temperature, and battery capacity were analysed. Optimum loading condition in standalone mode was found to be at 45% − 50% load under normal solar insolation without much burden on the battery bank and can be extended to a maximum load of 70% during the daytime at high solar insolation. In grid-connected mode, load application upto 45% was economically beneficial as less power was utilized from local grid. Though it can be subjected to almost its full rated capacity with input from the ac supply.

This study presents a numerical performance evaluation of shell and tube type of latent heat storage (LHS) with multiple finned tubes. Erythritol (C4H10O4) as energy storage media and cooking waste oil as HTF are employed in the proposed study. Nineteen finned heat transferring fluid (HTF) tubes are embedded inside the phase change material (PCM) to enhance melting. Numerical thermal performance study of LHS is performed using parameters such as charging time, liquid fraction, transient temperature and stored energy. For the melting process, the inlet working fluid flow rate and temperature are 75 LPM and 138 °C. For the discharging process, the flow rate is kept the same as the melting progresses, whereas, the inlet temperature is set to be 87 °C. The PCM in LHS gets melted completely within 175 min. during the charging process and it consumes 156 min. for the whole solidification process. The impact of operating parameters variations on the melting progress of the PCM is thoroughly studied. Increasing the working fluid inlet temperature and flow rate enhances the melting progress. The numerical results are validated with the experimental data to showcase the reliability of the proposed LHS system. The numerical results indicate reasonable similarity with the practical results with a maximum deviation of about 6.0%. It is observed that the during melting and solidification process, the overall stored and released energies are 27 MJ and 21.6 MJ, respectively.

The latent heat storage (LHS) system is an essential component required to harness renewable energy systems. For this purpose, thermal energy storage media commonly known as phase-change martials (PCM) are utilized. However, their low thermal conductivity is the main challenge to be addressed in the LHS systems applications. Therefore, a shell and tube kind of LHS with multiple finned heat transferring fluid (HTF) tubes is designed and fabricated. Erythritol (C4H10O4) as an energy storage media and cooking waste oil as HTF are utilized. Experimental and numerical thermal performance study of LHS is performed using various parameters such as stored energy, charging time, transient liquid fraction and temperature. The impact of the HTF mass flow rate and temperature variation on the melting behavior of the storage unit is studied. It is observed that the increase in inlet flow rate and temperature enhances melting performance. The experimental results are validated with the outcome of numerical analysis with CFD software (ANSYS-Fluent), which indicates acceptable accuracy of experimental results with a maximum discrepancy of 6.0%. The total simulation time of the whole melting analysis of the PCM inside LHS is 175 min. The sensible, latent heat and the overall stored energy of PCM are found as 9,429 kJ, 17,735 kJ and 27,164 kJ respectively.

In the present work, thermodynamic analysis of a natural convection dryer with and without sensible heat storage material (pebbles) has been studied. The purpose of this study is to enhance the performance of the dryer by using pebbles as a sensible heat storage medium. Energy and exergy analysis has been done to investigate the magnitude of losses whether the pebbles will be appropriate to use as a sensible heat storage material. The experiments were performed under different experimental conditions, without pebbles (case-I), pebbles filled up to the furnace height (case-II), pebbles filled up to the paraffin wax tray (case-III). In the case-IV, pebbles filled up to the paraffin wax tray but hot air is not allowed to flow from the rectangular chamber to the drying chamber. From the 1st three cases (I to III), it was observed that the energy losses and exergy destruction in the rectangular chamber are lower in the case-III. From the result, it can be seen that the use of sensible heat storage material and restricting the hot air in the rectangular chamber is promising in contributing to the performance of the dryer.

In the present study, a three-dimensional computational fluid dynamics (CFD) simulation is carried out to investigate the gas-solid fluidization behavior and heat transfer characteristics in a rotating solid-bed with static geometry (RFB-SG) without slits. With a static geometry adit as the research objective, this paper makes use of the Eulerian–Eulerian approach to carry out numerical simulations in ANSYS FLUENT 14.5 software. The prediction of particle fluidization capacity and its behavior in the developed reactor has been analyzed, using appropriate parameters and simulation analysis. The results illustrated that the main factors, such as air inlet velocity, inlet pressure, temperature, and heat transfer coefficient, affected the reactor capacity. It is observed that for a solid inventory of 300 g, a well-stabled solid-bed has been obtained at an air velocity of 22 m s−1. On enhancing the inlet air velocity up to 33 m s-1, not only the fluidization capacity of the reactor is increased by 500 g but also the drying efficiency is found to be increased. On validating numerical results with experimental findings, the maximum error of temperature is found to be 6.98%.

When there is a mismatch between time of energy generation and utilization latent heat energy storage systems (LHESS) are potential technology that can be used as a back-up. This paper presents a numerical study of a shell and tube type of thermal energy storage (TES) unit for solar cooking using a binary salt group phase change material (PCM) type known as potassium sodium nitrate salts (KNO3−NaNO3). The melting point temperature of the selected PCM is 222°C. The internal diameter and length of theTES is 240 mm and 960mm respectively. Using optimization method 19 heat transfer fluid (HTF) tubes are selected with external and internal diameter of 18 mm and 15.6 mm respectively. To improve heat transferring rate of the PCM storage each tube will be integrated with four longitudinal fins.COMSOL Multiphysics has been selected to model LHESS that enables testing of a multiple of configurations and optimization of the geometry used. Effective heat capacity method is employed to incorporate sensible and latent heat required for melting the PCM. To integrate the buoyancy effect of the molten layer of PCM, Boussinesq approximation has been included in the model and the governing equations taken in account the model are solved using the COMSOL Multiphysics software. And the circular configuration of tubes and fins embedded with PCM has been found best option. To evaluate the performance of energy storage unit three parameters have been selected: melt fraction, charging time and Energy stored. A finer mesh with 55428 elementssize is considered for the entire simulation of the LHS models. The inlet temperature of the HTF is set to be 235°C and the outside walls are thermally insulated. At time of 60 minutes the PCM becomes fully charged, at this moment the amount of stored latent, sensible and total energy during charging process in the LHS system is 5.88 MJ, 4.29 MJ, and 10.17 MJ respectively.

The submerged arc welding (SAW) is an automated process that is capable to weld thick and thin plates of steel and non-ferrous materials due to its ease of operation, less spatter and high deposition rates. SAW is extensively used to fabricate bridges, pipe lines, pressure vessel construction, ship building and surface cladding. In present study numerical simulation on effect of welding speed on residual stresses for SAW with square butt geometry of austenitic stainless steel is explored. A moving heat source model considering heat generation is used in this present study. The element birth and death technique is used to incorporate the effects of filler metal deposition. The peak temperatures observed in experimentation were correlated with that of numerical results and the variation was observed to be 4.77%. At higher welding speeds the low peak temperatures were observed which is due to less heat penetrating into the joint. It was observed in the present study at higher welding speeds the residual stress and von Mises stress were in increasing trend whereas normal and transverse stresses are negligible along the weld line.

The increasing global concerns about reduction of carbon footprint, climate change, and energy crisis have led researchers to delve into an alternative of fossil fuel reliant transportation. As a result of which 21st century has witnessed a renaissance of electric vehicle (EV) as a means of sustainable, environmental-friendly alternative. The electrification of the transportation sector has initiated the development of charging infrastructure for hassle-free operation of EVs. The development of charging infrastructure is accompanied by increase in load of the distribution network. The relatively high charging load of EVs is indeed a challenge for the power system engineers globally. It is essential to investigate the impact of EV charging load on distribution network for apposite placement of charging stations in the distribution network. Thus, this chapter aims to investigate the impact of EV charging station load on different operational parameters of the distribution network. Furthermore, an attempt will be made to optimally place the EV charging stations in the distribution network taking into account different operating parameters of the network. The entire analysis will be carried out on IEEE 69-bus test system which is a standard radial distribution network.

Conversion of woody biomass, animal waste such as cattle dung, chicken litters, pig manure, municipal solid, and agricultural wastes to methane gas under oxygen-free environment and favorable temperature range is called anaerobic digestion. But achieving the required temperature range under normal condition is difficult which necessitates the development of a heating system for better digestion process. The endeavor of the present investigation was developing 1.8 m2 solar collectors intended to heat biogas digester and investigating its performance. The solar collector was tested experimentally and numerically for heating water before implementing in actual model. A three-dimensional computational fluid dynamics model was developed by taking a single straight tube attached with an absorber plate at the bottom to predict outlet water and absorber plate temperature. The developed model predicted the outlet water temperature and absorber plate temperature with a reasonable accuracy. Moreover, 53 °C of outlet water temperature and 44% daily average efficiency were achieved at a flow rate of 0.021 kg/s. As the obtained temperature was found to be good enough for anaerobic digestion, the developed solar collector could be regarded as an alternate option.

Thermal degradation of bamboo waste is studied using thermogravimetric analyzer at four different heating rates (10, 15, 20 and 30 oC/min) in the temperatures range from 30 to 900°C. Two model-free (isoconversional) methods, Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) are used to determine the activation energy. The activation energies determined from the isoconversional methods are found to be increased with increasing the pyrolysis conversion. The average value of activation energies are 183.113 kJ/mol and 181.973 kJ /mol for KAS and FWO method respectively for the conversion range of 0.1 − 0.9. The frequency factor is determined using Kissinger method and found to be in the range of 1011− 1016S−1. The higher heating value of bamboo waste is found to be 18.83 MJ/kg, considered as potential feedstock for the production of bio-energy.

Recent strategies on fuel-development to reduce oil dependency to mitigate greenhouse gas emissions and to utilize domestic resources have generated interest in the search for alternative sources of fuel supplies. In this context, the industrial waste may be regarded as potential alternatives for biogas production. This study entails a detailed characterization of tea waste and food waste to evaluate their potential as an alternate feedstock to cattle dung for biogas production. The samples were characterized for volatile matter, moisture content, ash content and carbon hydrogen nitrogen (CHN). Property analysis of the biomass was also done by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The volatile matter content in tea and food waste was found to be 64.17% and 36.05% respectively, which is quite encouraging. The carbon-to-nitrogen (C:N) ratio, chemical oxygen demand and total solids of the sample also attributed its suitability for biogas production. The thermal behavior and heating values interpreted higher lignin content in tea waste. The lab scale study was conducted with combination of food waste/cattle dung and tea waste/cattle dung that showed higher biogas production in comparison to cattle dung alone implying their potential as biogas feedstock. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1247–1253, 2016

Removal of $$\hbox {CO}_{2}$$ from flue gases has become an effective way to mitigate the greenhouse gases, and adsorption is considered to be one of the methods. Adsorption of $$\hbox {CO}_{2}$$ on locally available coconut fibre-based activated carbon has been investigated and compared with adsorbents like zeolite 13X, zeolite 5A, and zeolite 4A at a temperature ranging from 298 to 333 K and pressure up to 100 kPa. The adsorption process was simulated by considering a linear driving force for the overall mass transfer and diffusivity factor. It was observed that the simulated curves acceptably reproduce the experimental data for the different temperatures studied. The adsorption isotherms for the three adsorbents were obtained and equilibrium characters about both adsorbate and adsorbent were analysed based on Toth isotherm model.

This study reports pyrolysis kinetics of biomass blends using isoconversional methods, viz. Friedman, FWO and KAS. Blends of three biomasses, viz. saw dust, bamboo dust and rice husk, were used. Extractives and volatiles in biomass and minerals in ash had marked influence on enhancement of reaction kinetics during co-pyrolysis, as indicated by reduction in activation energy and increase in decomposition intensity. Pyrolysis kinetics of saw dust and rice husk accelerated (positive synergy), while that of bamboo dust decelerated after blending (negative synergy). Predominant reaction mechanism of all biomass blends was 3-D diffusion in lower conversion range (α ≤ 0.5), while for α ≥ 0.5 pyrolysis followed random nucleation (or nucleation and growth mechanism). Higher reaction order for pyrolysis of blends of rice husk with saw dust and bamboo dust was attributed to catalytic effect of minerals in ash. Positive ΔH and ΔG was obtained for pyrolysis of all biomass blends.

In the present work, quality drying characteristics of sliced ginger were studied utilizing the concept of waste heat recovery in a biomass operated natural convection dryer with sensible heat storage material (SHSM) and phase change material (PCM). Ginger slices (2 and 4 mm thick) were dried from initial moisture content (MC) 88-90% (w.b.) to final moisture content 11-12% (w.b.) with hot air maintained at temperature 60 0 C, air velocity 0.2 m/sec, atmospheric average relative humidity 74% and ambient temperature 25 0 C. It was observed that the biomass consumption and melting time of PCM were significantly reduced due to the use of waste heat. The optimum drying time was found to be 5.5 h for 2 mm thick ginger slices. Color, texture and aroma were found better in treated sample.

Electricity generation through coal–thermal route is one of the highest contributors to environment pollution through greenhouse gas emission, which has given rise to issue of climate change risk. Among different alternatives of renewable energy, an important source is biomass-based energy. Utilization of biomass for energy production in coal-fired power plants is essentially in terms of partial substitution of coal feed with biomass. Major challenge in this route is fluctuating supply and varying compositions of biomass. It can be overcome by adopting co-gasification technology (using mixed feed of biomass and low-grade coal) for power generation. In this chapter, we have presented a critical review and analysis of the literature in the area of co-gasification of biomass and coal. Analysis in this paper touches upon several facets of co-gasification process such as effect of biomass/coal ratio, the composition (proximate/ultimate analyses of biomass/coal), gasification media, temperature and heating rates on the gasification kinetics, producer gas composition, and yield. The synergistic effects between gasification of coal and biomass have been reviewed. The alkali/alkaline earth metal content in the ash of biomass catalyzes the kinetics of the gasification of coal char. However, if coal has high silica content, adverse reaction between silica and potassium oxides can deactivate the catalytic effect. Actual chemical mechanisms related to this synergy have also been described and discussed. Finally, a brief review of the literature on gasification of coal/biomass blends in bubbling/circulating fluidized bed gasifiers has also been presented.

Biomass gasifiers with capacities exceeding 1 MW have large biomass consumption, and mixture of biomasses need to be used as feedstock in these gasifiers. In this chapter, we have presented a review of our studies in gasification of biomass blends using approaches of non-stoichiometric equilibrium, semi-equilibrium, and kinetic models. Initially, gasification of biomass mixtures has been assessed using thermodynamic equilibrium and semi-equilibrium (with limited carbon conversion) model employing Gibbs energy minimization. Influence of operating parameters such as equivalence ratio, temperature of gasification, and composition of the biomass mixture has been evaluated using two criteria, viz net yield and LHV of the producer gas. Interestingly, optimum operating conditions for all biomass mixtures have been established as equivalence ratio ~0.3 and gasification temperature ~800 °C. The kinetic model analysis of gasification of biomass based on a circulating fluidized bed gasifier. A series of chemical reactions was considered for obtaining complete mass balance. Although the profiles of molar composition, net yield and LHV of the producer gas predicted by kinetic model matched with equilibrium models qualitatively, significant quantitative difference was evident. The processes of char gasification and tar oxidation have slow kinetics that adversely affects the carbon conversion in the riser of the circulating fluidized bed gasifier.

With the rising level of greenhouse gas emissions and fuel prices, the hydrokinetic turbines have become increasingly popular for electricity generation in rural and remote areas teemed with small river streams. Such lift-based helical-bladed hydrokinetic turbines were invented over a decade ago, however, they could not find their wide application in commercial power generation. The present investigation deals with the in-situ experiments of a double-step three-bladed helical hydrokinetic turbine for possible electricity generation. Further, its performance is compared with that of a conventional single-step helical-bladed turbine. The main parameters that influence the performance of a helical-bladed hydro turbine are solidity ratio, blade wrap ratio, helix angle, blade profile and number of blades. In the present work, the helical NACA 0022 bladed turbines with solidity ratio of 0.20 and blade wrap ratio of 1.0 have been developed. The developed single and double-step configurations have been field-tested in the Brahmaputra river and their performance characteristics are estimated at different mechanical loading conditions using mechanical dynamometer.

Before the mining of fossil fuels, biomass was the main source of energy for heating and cooking including hot fuel gas production. With rapid industrialization and use of fossil fuels with high calorific values, use of biomass decreased rapidly. However, in the present context of both climate change and energy security, importance of biomass is regaining as a sustainable energy solution. Life cycle of CO2 emission during the secondary energy production from biomass is lesser than that of the fossil fuels. It is even negative, say for bioenergy with carbon capture. Biomass with good calorific value is abundantly available in countries with rapidly increasing energy demands like India, China, Brazil. Utilization of biomass may increase energy access in rural areas and long-term energy security in India. However, proper selection of biomass, their logistics, and conversion pathways will play an important role. Sustainability of the biomass-based energy system should be assessed for its future feasibility. In this chapter, role of biomass for sustainable energy is assessed specifically for India. Present challenges of energy generation are reviewed. Availability of different types of biomass and logistics are explored. Then, various possible conversion technologies for the conversion of biomass for fuels, electricity are discussed. Possible energy system design for biomass inputs including direct firing, co-firing, gasification and polygeneration are discussed in this chapter. Sustainability assessment of these energy systems is discussed in this chapter. Finally, challenges and prospects related to biomass-based distributed energy solution are presented.

Rural electrification is an important measure for prompt and sustainable growth of the developing nations. Providing electricity access to extreme remote localities is a challenging task for distribution utilities. Microgrids with renewable energy based distributed generation using locally available energy resources may be one of the effective solutions. This paper presents a study on recent developments in microgrid with the Hybrid Renewable Energy System (HRES). A brief discussion and analysis of modeling, control, reliability and energy management of microgrid with HRES is presented. A brief survey and examination of the potential of power generation with HRES in South-Asian nations is also undertaken in this research.

An important aspect of the commercialization of biomass gasifiers is feedstock flexibility. The present study has dealt with performance assessment of a circulating fluidized bed gasifier (50 kWth) with binary blends of three biomasses, sawdust (SD), rice husk (RH) and bamboo dust (BD), as feedstock. The performance of gasification was assessed in respect of the specific yield of producer gas, its LHV, and tar content in addition to gasification efficiencies. Experiments were conducted with varying equivalence ratio (ER) from 0.19 to 0.35, and temperatures of 800°–900 °C. The blending of biomasses resulted in the enhancement of gasification performance due to synergistic effects. Minerals in the ash of RH catalyzed char and tar conversion leading to higher efficiencies. At ER = 0.35, maximum CGE = 62% and CCE = 98% were obtained for RH + BD blend. With increasing temperature, H2, CO content and net yield of producer gas increased with concurrent decreasing in tar. The highest LHV of producer gas (5.05 MJ/Nm3) was obtained for the RH + BD blend at ER = 0.19 and 800 °C. Maximum gas yield (1.72 Nm3/kg dry biomass) and minimum tar content (2.01 g/kg dry biomass) were obtained for SD + BD and RH + BD blends, respectively, at 800 °C and ER = 0.35.

Gasification is the thermochemical conversion of solid fuel into the gas which contains mainly hydrogen, carbon monoxide, carbon dioxide, methane and nitrogen. In gasification, fluidized bed technology is widely used due to its various advantageous features which include high heat transfer, uniform and controllable temperature and favorable gas–solid contacting. Modeling and simulation of fluidized bed gasification is useful for optimizing the gasifier design and operation with minimal temporal and financial cost. The present work investigates the different modeling approaches applied to the fluidized bed gasification systems. These models are broadly classified as the equilibrium model and the rate based or kinetic model. On the other hand, depending on the description of the hydrodynamic of the bed, fluidized bed models may also be classified as the two-phase flow model, the Euler–Euler model and the Euler–Lagrange model. Mathematical formulation of each of the model mentioned above and their merits and demerits are discussed. Detail reviews of different model used by different researchers with major results obtained by them are presented while the special focus is given on Euler–Euler and Euler–Lagrange CFD models.

In the present investigation, bed-to-wall heat transfer coefficient was studied at the upper splash region of a pressurized circulating fluidized bed (PCFB) riser of internal diameter 54 mm and height of 2000 mm. The experiments were carried out at three different temperatures. At each temperature, experiments were performed at three different operating pressures viz. 1, 3 and 5 bar to investigate the influence of operating pressure. At each pressure condition, bed temperature distributions along the height of the riser were investigated. The superficial velocity was maintained constant throughout the experiment at 7 m/s. The effect of twisted tape inserts on heat transfer at the upper splash region of the riser was studied at three different solid inventories of 400, 600 and 800 g and the results obtained are compared without twisted tape inserts. The average particle size of sand used in the experiment was of 307 μm. The overall uncertainty in calculating the heat transfer coefficient was found to be ±12.3%.

In this study the effects of temperature on anaerobic co-digestion of saw dust with cattle dung is investigated. It also simulates the biogas production from saw dust with cattle dung at various temperatures. Results showed that high temperature could improve the anaerobic digestion and hence increase the biogas production rates. The operating temperatures used in this study were 35°C, 45°C, and 55°C. Modelling study revealed that exponential plot simulated better in both ascending and descending limb at all the three temperatures. However in ascending limb exponential plot was better for biogas production at 55°C and 35°C whereas in descending limb exponential plot was better for biogas production at 45°C. Gaussian plot had higher correlation at 35°C compared to other temperatures. Logistic growth model and modified Gompertz plot showed better correlation of cumulative biogas production than exponential rise to maximum plot for all the temperatures.