Mechanical engineering Department

This paper investigates the capability of running a system which uses hot fluid from solar evacuated tube collectors to boost the temperature and overall heat storage of the solar pond. The system is circulated by a solar powered pump, producing heat energy entirely from the incoming solar radiation from the sun. Solar evacuated tube collectors use a renewable source of power directly from the sun to heat the working fluid to very high temperatures. Solar ponds are emerging on the renewable energy scene with the capacity to provide a simple and inexpensive thermal storage for the production of heat on a large scale. The results of the performance of the system show a significant heat energy increase into the solar ponds lower convective region, increasing the overall performance of the solar pond.

This study aims at generating fundamental knowledge of the interaction of hydrated protons (hydronium) with layered graphene materials. The adsorption mechanism is determined utilising Density Functional Theory (DFT) and ab initio Molecular Dynamics (MD) simulations. The initial results show dissociation of the hydronium ion to produce a proton bound to the graphene without significant structural change at 300 K. The remaining water molecule stays attracted to the chemisorbed hydrogen atom. Further simulations are required to determine the full hydrogen storage capacity of this system.

A solid carbon-based composite electrode made from charcoal powder and nafion binder has been developed with potential application of storage of hydrogen electrochemically that could be utilised in fuel cells for remote area power supply. The developed electrode could be employed to store energy generated by inherently variable renewable sources and hence could act as a continuous power supply source. Such potential candidate electrode, particularly for fuel cell applications, should be both proton and electron conductive. Proton conductivity of the composite electrode was calculated from the measured proton resistance towards the flow of current using electrochemical impedance spectroscopy. Electron conductivity was calculated from the separately measured electron resistance using a standard ohm-meter or multi-meter. The effect of change in humidity on proton and electron conductivity of the composite electrode was examined. The carbon used was a common form of charcoal powder. Perfluorosulfonic acid or Nafion 117 was used as a proton conducting medium within the composite electrode. Proton conductivities in the range of 0.015 -0.043 S/cm were recorded, while the electron conductivities were in the range of 5.79 -6.45 S/cm. It was found that the increased level of hydration lead to increase in the proton conductivity, while electron conductivity falls down.

— Emissions from automobiles running on conventional hydrocarbon-based fossil fuels have lead to increase in concentration of greenhouse gases (GHGs) that further have contributed in global warming to a great extent. For past few decades hydrogen has emerged as a potential alternative of conventional fossil fuels that could be stored on board and produced domestically and therefore, is globally considered as a future fuel. But, efficient and safe storage and few challenged to be addressed by the researchers. One solution to the problem is electrochemical storage of hydrogen in a porous medium and its utilisation in fuel cell to generate electricity to power the automobile. The presented paper therefore, focuses on determining the electrochemical hydrogen storage capacity of a commercial activated carbon (aC) electrode soaked in acid with potential application in hydrogen fuel cell. The method of fabrication of solid activated carbon electrode is explained in detail. The proton conductivity, double-layer capacitance and electrochemical hydrogen storage capacity of the sample electrode was measured at different levels of hydration. All the testing procedures are discussed and obtained results are used to reach conclusion and recommend future work. The proton conductivity of a fully hydrated commercial aC electrode soaked in 1 mol. sulphuric acid was found to be 0.0110 S/cm, double-layer capacitance as 41.0 F/g, and electrochemical hydrogen capacity as 1.08 wt%. The measured hydrogen capacity is comparable with commercially available metal-hydride based hydrogen storage canisters, lithium-ion and lithium-polymer batteries. The work demonstrates the flow of hydrogen to-and-fro activated carbon electrode soaked in acid that could be used in PEM fuel cell as an integrated hydrogen storage medium and has a potential application in automobiles.

A metal hydride-nafion composite electrode with dual proton and electron conductivity has been fabricated that may have applications for electrochemical storage of hydrogen. The proton conductivity of the composite electrode was measured using electrochemical impedance spectroscopy. Its electron conductivity was calculated from measurements of dc resistance. Ambient conditions were varied to study the effect of humidification and hence degree of hydration of the electrode on proton and electron conductivity of the composite electrode. The metal hydride used was a common form of AB5 alloy made from rare earth and transition element metals. Nafion-117 solution was employed as the source of nafion within the composite. Proton conductivities in the range 0.0074 to 0.0209 S/cm were obtained, while the electron conductivities were higher, in the range 13.9 to 34.7 S/cm. It was found that the proton conductivity of the composite electrode rose with increased hydration, while electron conductivity fell.

Continuously diminishing fossil fuel reservoirs and limited land area for energy harnessing has compelled researchers to shift their focus towards renewable energy. Though these resources are available in abundance but, even the best available energy harnessing technologies are not mature enough to yield the best efficiencies in terms of energy harnessing/m2 of the land deployed. The present paper focuses on the innovative design of a hybrid Solar-Wind system to exploit the better energy harnessing per sq. m. of land where both the solar and wind energy resources are available in abundance. A theoretical study on implication of the hybrid design is carried out at the selected locations of Umrala and Haripar in India. The solar irradiance and wind velocity data for the last three decades for these sites are collected using PVsyst software. The yielded results would definitely result in effective utilization of land, and increase in energy density.

Inherently variable nature of renewable sources of energy such as solar and wind, are incapable of meeting continuous supply demand. Combining solar photovoltaic (PV) and wind power could offer a feasible solution to the problem of continuous power supply, particularly in those geographical locations where both resources are available in abundance. The present paper investigates the solar and wind energy potential in Indian sub-continent. The feasibility of harnessing renewable energy per sq. meter of land (i.e. energy density) from a combined solar PV-Wind hybrid system in the selected location-Jaisalmer in Rajasthan, is reported. The solar irradiance and wind velocity data for the last three decades for the selected site is collected using PVsyst software. A novel design of PV-wind hybrid system is proposed to gauge the better utilization of the existing space, productivity enhancement, and energy/m2 harnessed from the utilized land. The proposed system would pave a way forward towards developing a more sustainable, effective and rugged hybrid renewable energy systems that could cater the energy needs of the Indian sub-continent and similar geographical locations. Keyword-solar energy, wind energy, renewable energy harnessing, hybrid system. I. INTRODUCTION Most of the human activities are energy dependent and therefore, it is worthwhile mentioning that energy is an inherent and the most essential part required for survival of mankind [1]. Contradictory to this, one of the most crucial challenges facing the mankind is the energy crisis [2]. Moreover, for energy needs people are still relying on continuously depleting conventional fossil fuels which emit harmful green house gases, when burnt [3]. In lieu to this, the researchers are bound to explore alternate sources of energy that are capable of meeting the continuous power supply demand, are environmental friendly, and could contribute to a sustainable society. One of the solutions to the mentioned problem is shifting to renewable sources of energy [4-6]. Most of the renewable sources of energy are inherently variable in nature and hence, is incapable of meeting the continuous power supply demand. Therefore, all renewable energy power generation/conversion systems are backed by energy storage devices such as batteries [7-9]. However, combination of more than one available renewable energy source could yield better results in terms of energy harnessing efficiency and energy production per unit space occupied. In this context, a novel design of Solar PV-wind hybrid system is proposed in which an array of solar PV is installed around the periphery of the stem of a horizontal-axis wind turbine. To investigate the feasibility of the proposed system a detailed theoretical study is conducted and simulation is carried out in PVsyst software by implementing the system on a selected site viz. Jaisalmer, Rajasthan in India. The fixed input parameters of the selected site are inserted to obtain the results in terms of power generation and its variance throughout the year.

The inherently variable nature of renewable energy sources makes them storage-dependent when providing a reliable and continuous energy supply. One feasible energy-storage option that could meet this challenge is storing surplus renewable energy in the form of hydrogen. In this context, storage of hydrogen electrochemically in porous carbon-based electrodes is investigated. Measurements of hydrogen storage capacity, proton conductivity, and capacitance due to electrical double layer of several porous activated carbon electrodes are reported. The hydrogen storage capacity of the tested electrodes is found in the range of 0.61−1.05 wt.%, which compares favorably with commercially available metal hydride-based hydrogen storage, lithium polymer batteries, and lithium ion batteries in terms of gravimetric energy density. The highest obtained proton conductivity was 0.0965 S/cm, which is near to that of the commercial polymer-based proton conductor, nafion 117, under fully hydrated condit...

Inherently variable nature of renewable sources of energy such as solar and wind, are incapable of meeting continuous supply demand. Combining solar photovoltaic (PV) and fuel cell could offer a feasible solution to the challenge of continuous power supply, particularly in those geographical locations where renewable resources are available in abundance. The present paper investigates a solar PV and fuel cell-based hybrid system in-context to a selected site in Indian sub-continent. The feasibility of harnessing renewable energy per sq. meter of land (i.e. energy density) from a combined solar PV-fuel cell based hybrid system employed in Jodhpur location in Rajasthan is reported. The solar irradiance data for the last three decades corresponding to the longitudinal and latitudinal coordinates of Jodhpur is collected using PVsyst software. A novel design of PV-fuel cell hybrid system is proposed to gauge the enhanced utilization of the existing space, productivity enhancement, and en...

The extensive use of fossil fuels have resulted in the extinction of the world fossil reservoirs, and brought tremendous change in earth’s environment. One such activity is powering marine ships from conventional fossil fuels that contribute towards pollution. Solar energy has potential to address this concern. However, solar energy being intermittent in nature is storage dependant. Presently, lithium-based batteries are fulfilling the global need of energy storage which is self-discharging, highly expensive to recycle and emit fumes. To overcome such challenges, a novel proton-battery which works on the principle of unitized regenerative fuel cell is proposed in this paper along with conventional photovoltaic system suitable for marine ship power supply. The fabrication of an experimental set-up is disclosed. The obtained experimental results revealed the technical feasibility of the proposed system. The proposed system for marine ships could play a vital role catering this industr...

Hydrogen has already been identified as a potential candidate capable of replacing fossil fuels because of its immense energy content compared to conventional fuels. However, finding the safe, efficient generation and storage of hydrogen is a challenge. The present paper reports on hydrogen generation and its subsequent adsorption-desorption process in a proton battery with varied catalyst loading. The method of porous carbon electrode fabrication and experimentation is disclosed. The scanning electron microscopy (SEM) is employed to determine morphology characteristics of the fabricated electrodes that are integrated in a proton battery to study the process of hydrogen adsorption and desorption under the influence of varied catalytic loading. The comparison between catalytic loading of 1 mg/cm2 and 2 mg/cm2 is analysed and reported. The hydrogen storage capacity of activated carbon electrode employed in a proton battery is obtained to be in the range of 0.4 to 0.5 wt. %. The obtain...

Thermoelectric generators (TEGs) convert heat energy into electricity. Currently, these devices are attached to heat exchangers by means of mechanical devices such as clamps or fixtures with nuts and bolts. These mechanical devices are not suitable for use in harsh environments due to problems with rusting and maintenance. To eliminate the need for such mechanical devices, various kinds of adhesives used to attach thermoelectric generators to heat exchangers are investigated experimentally in this work. These adhesives have been selected based on their thermal properties and also their stability to work in harsh environments to avoid damage to the integrity of the attachment over long periods of time. Stainless-steel plates were attached to a thermoelectric generator using the adhesives. The introduction of the adhesive as a means of attachment for thermoelectric generators contributes to increase the thermal resistance to heat transfer across the TEG. The adhesive layers increased the thermal resistance of the thermoelectric generator by 16% to 109%. This work examines the effect of the adhesives on the thermal performance and power output of a single thermoelectric generator for various heat inputs.

Salinity gradient solar ponds act as an integrated thermal solar energy collector and storage system. The temperature difference between the upper convective zone and the lower convective zone of a salinity gradient solar pond can be in the range of 40-60°C. The temperature at the bottom of the pond can reach up to 90°C. Low-grade heat (<100°C) from solar ponds is currently converted into electricity by organic Rankine cycle engines. Thermoelectric generators can operate at very low temperature differences and can be a good candidate to replace organic Rankine cycle engines for power generation from salinity gradient solar ponds. The temperature difference in a solar pond can be used to power thermoelectric generators for electricity production. This paper presents an experimental investigation of a thermoelectric generators heat exchanger system designed to be powered by the hot water from the lower convective zone of a solar pond, and cold water from the upper convective zone of a solar pond. The results obtained have indicated significant prospects of such a system to generate power from low-grade heat for remote area power supply systems.

For sustainable and incremental growth, mankind is adopting renewable sources of energy along with storage systems. Storing surplus renewable energy in the form of hydrogen is a viable solution to meet continuous energy demands. In this paper the concept of electrochemical hydrogen storage in a solid multi-walled carbon nanotube (MWCNT) electrode integrated in a modified unitized regenerative fuel cell (URFC) is investigated. The method of solid electrode fabrication from MWCNT powder and egg white as an organic binder is disclosed. The electrochemical testing of a modified URFC with an integrated MWCNT-based hydrogen storage electrode is performed and reported. Galvanostatic charging and discharging was carried out and results analyzed to ascertain the electrochemical hydrogen storage capacity of the fabricated electrode. The electrochemical hydrogen storage capacity of the porous MWCNT electrode is found to be 2.47 wt%, which is comparable with commercially available AB5-based hyd...

Renewable energy has become popular alternative to fossil fuels as it can avoid environmental pollution such as air pollution. With the increase of human population and the demand of the power, power generation from renewable energy are greatly welcomed to be used for the future generation. One of the renewable energies that can be harnessed to meet our energy needs is solar energy. Salinity gradient solar pond is a low-cost solar collector and it can be used for a long term of heat storage. The storage of heat is useful for the generation of power during cloudy day and at night, in addition being very useful compared to other solar system. In this research, the solar pond was filled with saline water with increasing of density from top to the bottom as solar radiation was being absorb at the bottom of the pond. This project mainly focused on the construction of the salinity gradient solar pond and the methods to maintain the condition of solar pond. The parameters, such as temperature, density and pH value of water in solar pond was obtained as part of the maintenance and stability of the pond.

Solar pond is an integrated solar collector and storage. An experimental salinity gradient solar pond was constructed to analyse the thermal storage capability. The solar pond consist of 2.4 m², 1.4 m deep with sodium chloride (NaCl) as the salt solution. For the development of salinity gradient, a diffuser was used to develop the salinity gradient. The salinity gradient solar pond consists lower convective zone (LCZ) with a height of 0.5 m with 1200 kg/m 3 density, non-convective zone (NCZ) with a height 0.8 m and upper convective zone (UCZ) with a height 10 cm. The temperature of (LCZ) as heat storage was recorded and analysed weekly. Maximum temperature of (LCZ) storage zone was recorded to be at 36.5 °C after four weeks and it showed and upward trend. The heat energy stored in (LCZ) can be used for power generation.

Heat engine converts chemical engine available in fuel to useful mechanical energy. One of the most famous heat engines is internal combustion (IC) engine. IC engine plays a pivotal role in transportation and other industrial applications. A lot of waste heat is rejected from a typical IC engine as the conversion efficiency of this type of engine is only about 35-40 %. The waste heat has the potential to be tapped and converted into useful energy. This can help to increase the performance of the IC engine system. This work focused on the conversion of the waste heat energy of the IC engine into electricity by using thermoelectric generator (TEG). The aim of the project was to demonstrate the applicability of TEG to convert waste heat from exhaust to useful electrical energy. Two TEGs were individually tested to attain the electrical characterization and also tested on series and parallel connections. The study showed that the series connection of TEGs has improved and increased volt...

A metal hydride-nafion composite electrode with dual proton and electron conductivity has been fabricated that may have applications for electrochemical storage of hydrogen. The proton conductivity of the composite electrode was measured using electrochemical impedance spectroscopy. Its electron conductivity was calculated from measurements of dc resistance. Ambient conditions were varied to study the effect of humidification and hence degree of hydration of the electrode on proton and electron conductivity of the composite electrode. The metal hydride used was a common form of AB5 alloy made from rare earth and transition element metals. Nafion-117 solution was employed as the source of nafion within the composite. Proton conductivities in the range 0.0074 to 0.0209 S/cm were obtained, while the electron conductivities were higher, in the range 13.9 to 34.7 S/cm. It was found that the proton conductivity of the composite electrode rose with increased hydration, while electron conductivity fell.

The origin of the unique geometry for nitric oxide ͑NO͒ adsorption on Pd͑111͒ and Pt͑111͒ surfaces as well as the effect of temperature were studied by density functional theory calculations and ab initio molecular dynamics at finite temperature. We found that at low coverage, the adsorption geometry is determined by electronic interactions, depending sensitively on the adsorption sites and coverages, and the effect of temperature on geometries is significant. At coverage of 0.25 monolayer ͑ML͒, adsorbed NO at hollow sites prefer an upright configuration, while NO adsorbed at top sites prefer a tilting configuration. With increase in the coverage up to 0.50 ML, the enhanced steric repulsion lead to the tilting of hollow NO. We found that the tilting was enhanced by the thermal effects. At coverage of 0.75 ML with p͑2 ϫ 2͒-3NO͑fcc+ hcp+ top͒ structure, we found that there was no preferential orientation for tilted top NO. The interplay of the orbital hybridization, thermal effects, steric repulsion, and their effects on the adsorption geometries were highlighted at the end.

This manuscript presents a thorough review of unitized regenerative fuel cells (URFCs) and their importance in Remote Area Power Supply (RAPS). In RAPS systems that utilize solar and hydrogen power, which typically include photovoltaic modules, a proton exchange membrane (PEM) electrolyzer, hydrogen gas storage, and PEM fuel cells, the cost of these systems is currently higher compared to conventional RAPS systems that employ diesel generators or batteries. URFCs offer a potential solution to reduce the expenses of solar hydrogen renewable energy systems in RAPS by combining the functionalities of the electrolyzer and fuel cell into a single unit, thereby eliminating the need to purchase separate and costly electrolyzer and fuel cell units. URFCs are particularly well-suited for RAPS applications because the electrolyzer and fuel cell do not need to operate simultaneously. In electrolyzer mode, URFCs function similarly to stand-alone electrolyzers. However, in fuel cell mode, the pe...