ABSTRACT. The growth of the photovoltaic industry has been impressive over the last decade or so. In recent times there have been many reports that the systems do not perform as expected. This contribution discusses the underlying reasons.

There are two possibilities why expectations would not be met: unrealistic expectations or systems underperformance. Both options are equally valid as is discussed.

The presentation explores why sometimes unrealistic expectations are set. The cases discussed include inappropriate input data for devices and operating environment, ‘commercial overrule’, ignorance and lack of understanding of what was actually predicted. The latter is largely an issue of cash-flow as people do not consider normal variations in the operating environment. The discussion of inappropriate input data evaluates how accurate performance relevant parameters can be measured at the moment and how this will affect the yield prediction. Key points elaborated here are that unrealistic performance prediction is normally not due to inaccurate models or technology differences.

There are also many cases where for one reason or another the system does not perform as it expected. The reasons are often related to ongoing O&M (operation and management) of the plant or more serious issues such as planning or built issues or indeed component issues. It is shown that durability is the key unknown for system performance. This is concluded with a quick review of the status of evaluating durability at the moment and avenues for future improvements.

ABSTRACT. The environmental influence of plants within buildings cannot at present be adequately represented using typical building simulation models as they do not include the ability to simulate the potentially significant heat and mass transfer between plants and the internal air. On the other hand, models developed for the simulation of climate-controlled greenhouses do not allow complex interactions with existing buildings and infrastructure. We present the development of a building integrated greenhouse model, with the ability to simulate the response of the indoor climate to crop growth. We validate the model against data from an urban farm 50 m underground.  We show that the simulation allows us to optimise the environment and energy benefits of growing plants within enclosed environments.

ABSTRACT. The role and importance of Renewable Energy is increasingly felt with the looming fears of increase in global temperature rise of the planet, increase of the Green House Gas (GHG) emission causing climate change readily visible to us more clearly than ever. Renewable Energy technologies contributed a record estimated 161 Gigawatts (GW) of capacity in 2016. Solar PV contributed record 47%, whilst wind 34% and hydropower 15.5%, with the investment in Renewables reaching $242 billion. However, the intermittency of Renewable Energy generation leading to low capacity factors and fluctuating base load, imposes a significant challenge for the sustainability of the supply of electricity in the developing nations, which in turn demand a sustained electricity generation through coal fired plants causing emissions or nuclear plants which require huge first time investments.

The developing countries suffer from non-sustained or absence of power supplies scenarios, due to lack of infrastructure investments. Renewable electricity may be a solution for urban cities but will require sustained storage solutions, whilst for the rural areas and villages the stand-alone photovoltaic generation at affordable costs viz. easily deployable on the roof with flexible, lightweight CIGS or Perovskite solar cells with a proven stability will be an option.

ABSTRACT. Effect of Bi adatoms on Pt nanoparticles for the anodic reaction of direct ethanol fuel cell i.e., electrochemical oxidation of ethanol was studied in alkaline medium by depositing partial monolayer of Bi on Pt nanopartilces. Initially, full monolayer of Bi shell was deposited on Pt nanoparticles by kinetically controlled autocatalytic deposition method using adsorbed monolayer H as the mediator followed by etching of some of the surface Bi atoms to obtain partial monolayer. Core@shell structure of Bi@Pt nanoparticles was confirmed by both electrochemical and STEM characterizations. By using XPS analysis, shell thickness of core(Pt)@shell(Bi)/C nanoparticles was determined. After adding Bi monolayer to Pt, its electrochemical activity for ethanol oxidation was increased by 4 times. Furthermore, rate constant of the ethanol electro oxidation reaction at different applied potentials and the average number of electrons transferred during the ethanol electro oxidation reaction were measured from chronocoulometry data obtained for electrochemical oxidation of ethanol.

ABSTRACT. Composite-cross linked membranes based on highly sulfonated poly(ether ether ketone), Poly Ethylene Glycol (PEG) as cross linker and TiO2 as inorganic additive were synthesized. Two different percentage of TiO2 (2.5% and 5%) were used. The electrochemical and mechanical properties of the membranes were investigated from room temperature (27ºC) to elevated temperature (60C) for their application in fuel cell. The conductivity of membranes increased linearly with increasing temperature and the membrane blended with lower percentage of TiO2 (SPEEK-PEG-2.5%TiO2) showed higher conductivity than the higher percentage. The conductivity increased from 0.1 S cm-1 to 0.17 S cm-1 with increasing temperature from 30°C to 60°C for SPEEK-PEG-2.5%TiO2 membrane whereas the conductivity increased from 0.08 S cm-1 to 0.14 S cm-1 for SPEEK-PEG-5%TiO2. Mechanical properties of both the membranes were good i.e., the tensile strength in the range of 15 to 20 MPa and the percentage elongation in the range of 150 to 180%. Studies were carried out to evaluate the performance of SPEEK-PEG-2.5%TiO2 membrane in H2/O2 fuel cell up to 60°C and at 60C, maximum power density of 264.88 mW cm-2 at 616 mA cm-2 and 0.43 V was obtained. Therefore, these membranes can be considered a potential candidate for fuel cells application.

ABSTRACT. In this paper we deal with the strategic considerations to design the stack of vanadium redox flow battery. A short stack of 4 cells is prepared by electrically connecting in series and electrochemical study is performed including pressure drop measurements. The maximum power can be obtained with this stack is about 20 W at discharging voltage of 1 V and at current density of 50 mA/cm2. As energy and capacity are decoupled in flow batteries and as power depends on the number of cells, it is essential to connect individual cells electrically in series to form stacks, which may be further connected in series/ parallel to constitute a kW to MW scale module. Such stack designs gives complications in terms on number and size of the cells, shunt current losses, system efficiency, operating conditions and many other factors. It is briefly discussed about the requirement of number and active area of the cells.

ABSTRACT. Metal alloy nanoparticles (NP) are important to a number of renewable energy application, such as fuel cells. Mixing behavior and segregation of the metal species in the nanoparticle is crucial in determining the performance of the nanoparticles. Segregation, mixing, and catalytic activity are strongly influenced by the nanoparticle size, composition and temperature. Quantifying these effects within the nanoparticle requires thermodynamic understanding of species distribution within the NP. In this work, we show that these relations can be captured using a thermodynamic model based on the distribution coefficients for ternary alloy NP. These NPs are more complicated than bimetallic and monometallic NPs. We investigate whether the thermodynamic model can be applied for gaining fundamental understanding of NP segregation behaviour in ternary systems AuPtPd and AuPtNi.

ABSTRACT. Under operating conditions relevant to polymer electrolyte membrane fuel cell (PEMFC) NixPt1-x is known to exhibit oscillations in Pt compositions with the layer position, which is crucial to the catalytic activity of the alloy material. For example, the outermost and third layers of NiPt3 are Pt-rich whereas as the sub-surface layer is Ni-rich. Using Monte Carlo simulations we show that the surface segregation behavior in the presence of solvent can be remarkable. An inversion in the segregation behavior can be observed as Ni content is increased, such that the surface become Ni-rich when x≥0.6 compared to the bulk layer composition. A thermodynamic framework based on distribution coefficients is employed to elucidate this effect. The distribution coefficients have a value less than 1, which indicates Pt-enrichment at the surface for small x, increases to a value beyond 1 when x is large causing Ni atoms to populate the surface layer.

ABSTRACT. A large number of ionic configurations can be encountered in the long-time dynamics of yttria-stabilized zirconia (YSZ). We introduce a new theoretical framework to capture the effect of these configurations on oxygen ion movement in a coarse-grained sense, which we term as ensemble-averaged structure-kinetics relations. Ionic diffusion in bulk YSZ is probed using microsecond long classical molecular dynamics (MD) calculations performed for 8 mol% YSZ at temperatures 800-1200 K. We find that YSZ structure is comprised of many types of local environments. Low Y3+-content environments occur with a higher probability. We show that the free energy of finding O2--vacancy (O2--vac) pairs in a local environment is crucial to the hopping transitions. Higher probability of O2--vac pairs can result in more transitions. The time spent by an oxygen ion in a local environment is used to estimate the corresponding kinetic rates and their Arrhenius parameters averaged over an ensemble of configurations. The average rates and Arrhenius parameters are found to be sensitive to Y3+ content in the local environment. Comparisons with previous studies employing single configuration instead of an ensemble are made. The concepts can be straightforwardly extended to other materials as well.

ABSTRACT. The fossil fuel based power plants are one of the major contributors towards environmental pollution. Therefore, it is necessary that renewable sources such as solar energy should be utilized extensively to reduce environmental degradation. Solar energy has the potential to fulfill all of the world’s energy demands, but because of intermittency of sunlight, dispatchability, and availability issues associated with stand-alone solar energy systems only a small portion of available solar energy is being harnessed. A possible alternative for such systems is a hybrid system (an integration of concentrating solar power (CSP) technology and fossil fuel based power plants), referred as solar thermal hybrid technologies (STHT).The present investigation proposes integration of existing coal-fired power plant with solar energy. In this study the steam extracted to high pressure feed water heater is supplied by solar; thereby reducing amount of heat input from the boiler considerably. This hybridization of existing coal-fired power plant with solar energy reduces coal consumption and CO2 emissions. An algorithm based upon this STHT plant is developed in MATLAB. Based upon this algorithm useful heat input and thermal losses that occur in the tubes of the solar collector have also been discussed in this paper

ABSTRACT. In recent times, there is an upsurge in research on Combined Cooling, Heating and Power (CCHP) using supercritical CO2 as working fluid, assisted by solar energy. Supercritical Carbon Dioxide (S-CO2), when compared to other working fluids, has unique properties like low critical temperature, non-toxic, non-inflammable (Tc=31.10C, Pc=7.39 MPa). This paper presents a comparative study between two solar assisted CCHP systems, one operating with an expansion valve, and other operating with an expansion work output device. Based on the comparison, it is observed that the cooling user output and electrical power output improves by using an expansion work output device while the heating user output remains the same for both the configurations.

ABSTRACT. Vitality and water are need of humanity that impacts the advancement of any country. Drinking water lack is relied upon to end up noticeably one of the most concerning issues confronted by world. Solar still is a device which is used to convert brackish water into distilled water with the help of solar energy but it has limited productivity. In this work, comparative study of productivity of single basin solar still having nano fluid Al2o3 + water inside basin with same depth of water and absorber plate inside water basin as copper and aluminum has been examined. Water basin was black painted inside to absorb maximum solar radiation. Due to high thermal conductivity of copper plate and addition of energy absorbing nano fluid Al2o3, rate of evaporation of water from basin to glass surface got increase and maximum productivity of distilled water of 4.77 liters was achieved for copper based absorber plate as compared to 4.41 liters for aluminum based absorber plate. Energy absorbing medium such as metallic plate and nano fluid helped in maintaining a fair productivity when solar radiation value reduced and they helped to enhance productivity of solar still.

ABSTRACT. In this study, design, development and testing of an indirect solar dryer for rural domestic use is demonstrated. Qualitative and quantitative methods have been deployed to derive the appropriate design for the solar dryer, based on the local expectation and drying requirements. Local material and resources were used to construct the dryer, making it portable, affordable and locally accessible, thus, promoting a do-it-yourself (‘DIY’) model. Bitter gourd (Momordica charantia), okra (Abelmoschus esculentus), raw mango (Mangifera indica) and hirda (Terminalia chebula) were tested for the performance evaluation, as these items are typically open sun-dried in the studied villages for using in later seasons or for selling in market. Results show that using this solar dryer, moisture content of one kg of bitter gourd was bought down to 7.6% from 89% (wet basis) in eight hours, while retaining the color. The fabricated solar dryer was taken to the tribal village for demonstration and for feedback and also to encourage the local people on using this technology to substitute or supplement open-sun drying.

ABSTRACT. Accessibility to clean water is one of the most important challenges currently being faced by humanity. More than 780 million people in the world do not have access to clean water. Though earth has plenty of water, 97% of it is salt water in oceans which needs appropriate treatment technologies to convert this to potable water. Current technologies of water desalination such as reverse osmosis consume a significant amount of energy, leading to the water-energy conundrum. To overcome this limitation, recently several technologies based on nano-particle enhanced steam generation have been explored demonstrating extremely high conversion efficiencies (>40%) in the lab scale. These methods effectively utilize the plasmonic resonances of nano particles to increase the absorption cross-section for the sunlight. However, they typically need to be operated under high concentration (>10X) requiring continuous tracking which results in increased system cost and complexity. Here, a novel solar powered desalination system is proposed using CPC based concentrator (with concentration ratio 2) combined with a low-cost absorber. The system showed demonstrates huge potential with an efficiency of 39% achieved at 2X concentration.

ABSTRACT. Production of steam using renewable resources have drawn in a great deal of interest in recent times. Photo thermal systems of various designs and applications have thus been developed with considerable success. Nevertheless, it is impervious to develop a system which is low cost and scalable to fit real world applications. We have developed a system of carbon fabric and wood which provides an excellent solar steam generation with thermal efficiencies up to 60% under 1 sun illumination. The addition of the carbon fabric system above water increases the evaporation rate of water by 1.8 times. Solar steam can be got almost instantly upon illumination. The high thermal stability of carbon fabric makes it beneficial in large scale applications with very high incident intensities. It is envisioned that this system can be readily scaled in practical solar steam generation applications due to its simplicity, low cost, and high thermal stability.

ABSTRACT. India has substantial reserves of low sulphur, low grade (high ash) coal, which provides a reliable, cheap baseload power and hence, is expected to continue to be a major energy source for the next few decades. But, combustion of coal emits emits huge amount of carbon dioxide (CO2), the most prominent greenhouse gas (GHG) which is responsible for climate change. Various CO2 mitigation techniques including Carbon Capture and Sequestration (CCS) may be required in future to reduce the greenhouse gas emission to the atmosphere. The quality of coal used in power plants could play an important role in the overall performance of CCS. The focus of this study is to investigate the impact of coal quality while implementing carbon capture (CC) system in the new supercritical coal fired power plants in India. Supercritical pulverized coal (PC) plants with and without carbon capture (CC) and with different coal characteristics were simulated using IECM (Integrated Environmental Control Model). The impact of variation in the cost of coal and capacity factor has also been assessed along with different policy strategies required towards implementation of CCS in the country.

ABSTRACT. In the present study, experimental CO2 solubility in aqueous solution of 1-2-(aminoethyl)piperazine (AEP) was investigated at concentration of 30 wt % .The solubility was measured in a high pressure solubility cell at temperatures 303.15,313.15 and 323.15 K, over a CO2 pressure range of (2-200 kPa). The effect of equilibrium CO2 pressure, temperature and AEP concentration on CO2 loading were examined. The equilibrium solubility data were further correlated by semi-empirical model. In addition to this a parametric study was also conducted in Aspen Plus platform to investigate the performance of AEP over conventional solvent MEA in terms of % CO2 removal

ABSTRACT. The effect of both physical and chemical modification of zeolite 4A on CO2 adsorption characteristics was critically investigated. The physical modification was done by milling using planetary ball mill and chemical modification was done by amine impregnation technique. The physicochemical property of zeolite 4A was changed after modification. There was a decrease in surface area after milling about 53% which leads to 28% drop in CO2 adsorption capacity in Zeo-12 (milled zeolite 4A). Whereas, after chemical modification via isopropylamine impregnation on Zeo-00 (un-milled zeolite 4A) and Zeo-12, there was an increase in CO2 adsorption capacity by 10.45% and 46.23% respectively. Further, Henry’s constant was calculated from CO2 isotherm data which was enhanced by 5.82% and 451% in Zeo-00 and Zeo-12-IPA respectively. Such significant augmentation in adsorption capacity and Henry’s constant indicated that the chemical modification via amine impregnation is an efficient route for bulk CO2 adsorption as compared to physical modification.

ABSTRACT. Reactive absorption technique plays a vital role for CO2 capture from industrial flue gases. To improve CO2 capture, a quaternary mixture of 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), ethylene glycol monoethyl ether (EGMEE) and water is used. This mixture combines the higher loading capacity of AMP, high reactivity of PZ and lower heat ability of EGMEE. In the present study, kinetic aspects of the CO2 reaction with mixture of AMP and PZ were investigated using co-solvent EGMEE+water (hereafter noted as AAPE solution). Kinetic data were experimentally obtained in a stirred cell at 308-318 K. The concentrations of AMP and PZ in the mixtures were changed in the 2-3 and 0.1-0.5 M range whereas EGMEE concentration was changed between 1.11-3.45 M. Pseudo-first order rate constants were measured. Knowing the absorption rates in the aforesaid mixtures, the second-order rate constant and activation energy for the CO2-PZ system in AAPE solution was found to be 57460 M-1s-1 and 55.5 kJ mol-1 respectively at 308 K.

ABSTRACT. Desalination is one of the most promising technology to produce potable water. Clathrate hydrate based process has been proposed as a potential desalination technology to alleviate shortage of potable water in many parts of the World. Clathrate hydrate excludes salts and other impurities present in seawater and brackish water. After separating formed hydrate crystals from left over brine, we can potentially get pure water. However, efficient separation of hydrate from brine plays a major role in clathrate hydrate based desalination process. In general, salts present in seawater act as thermodynamic inhibitor for gas hydrate formation. Hence, an innovative approach has been employed by using Propane/ Nitrogen gas mixture in fixed bed by employing silica sand bed. Natural separation of hydrate from brine has been reported in an earlier work which helps in minimizing hydrate contamination by salts present in left over brine. In this work, water recovery from 1.5 wt% NaCl solution and 3 wt% NaCl solution has been studied and comparison has been made with kinetics of hydrate formation in deionized pure water. In this study, salt was found to act as kinetic inhibitor for hydrate formation.

ABSTRACT. The objective of the present study is to measure the adsorption isotherms of CO2 on activated carbon at different temperatures from 273 to 358 K and pressure up to the saturation pressure of assorted temperature using a Sievert’s type experimental setup. Extracts of experimental data of CO2 uptake are correlated to the Langmuir and Tóth adsorption isotherm models. The Tóth adsorption isotherm model is well suited to the experimental data of CO2 uptake. The essential thermodynamic properties are evaluated using an experimental data of CO2 uptake. In this work, the CO2 uptake and isosteric heat of adsorption of CO2 on the activated carbon are obtained and compared with other available activated carbons and it is found that the results are a good agreement of present measured result. These thermodynamic parameters are useful for designing of any adsorption based gas storage and cooling systems.

ABSTRACT. High temperature thermal storage in a packed bed is considered for air based concentrated solar power plants .In this work, the performance of a high temperature sensible heat system has been analysed using mathematical simulation. Heat transfer and fluid flow equations for a one dimensional two phase model has been discretized using explicit center difference scheme in space and Euler forward difference scheme in time. Discretized equations were solved to determine temperatures of different elements of bed, and corresponding temperature of air as a function of space and time coordinates. Temperature distribution of bed elements were utilized to obtain mean bed temperature and energy stored in the bed. These values were used to determine charging efficiency as a function of system parameters namely void fraction, equivalent diameter. The extensive investigation of parametric effects of important bed parameters namely element size, void fraction has been done in this work.

ABSTRACT. In this paper, unrestricted melting of erythritol phase change material is studied in a spherical reservoir to describe sinking effects on heat storage and heat transfer rate with nano-enhancement in medium temperature range (100 ̊C-150 ̊C) applications like solar energy storage, waste heat recovery etc. The unrestricted melting leads to strong stratified thermal zones in the reservoir and further nanoparticles presence modifies base fluid thermophysical properties. This will highly influence the heat transfer and the phase change patterns. The detailed analysis of nano-enhancement with unrestricted melting is performed. A macroscopic one-domain continuum model for the unrestricted melting of erythritol is presented in which the complete set of conservative governing equations (mass, momentum, energy) are solved using Pressure Poisson Equation (PPE) based finite volume method using an in-house code. The unrestricted melting behavior of Phase Change Material (PCM) and Nano-Enhanced Phase Change Material (NEPCM) is compared. The influence of thermal stratified zones with and without nano-enhancement is described on the coupled heat transfer and fluid flow behavior. Further performance indicators of PCM based Thermal Energy Storage Systems (TES), like sensible energy and latent energy storage, are studied in both cases to explore its potential to design erythritol based TES with nano-enhancement.

ABSTRACT. Recently, renewable sources of energy, particularly, solar thermal energy has gained significant attention for developing heating and cooling mechanisms for buildings. Present work aims at developing a theoretical model for space heating based on phase change material (PCM) using solar energy in winter conditions for Northern region of India. The system has PCM container placed inside the room near the wall, which receives heat from concentrating solar system during the daytime. After achieving the temperature of PCM above its melting point using the solar system, the stored heat of PCM is released to the room ambient during the night time when the room ambient is at lower temperature. OM-37, having melting temperature of 37C has been used as a PCM for the current research work. The numerical investigation of the system shows that temperature of room reaches to 23℃ - 24℃ from 15C in 4-6 hours of operation due to high latent heat capacity of the PCM and thus ensuring thermal comfort of occupants.

ABSTRACT. Solar crop drying is most effective and efficient to direct application of solar thermal energy. Thermal energy storage in solar crop dryers can naturally regulate fluctuation of the temperature in the drying chamber from peak and lean solar radiation. A solar dryer with provision of phase change material energy storage was designed as that it had flat plate collector area of 1.5 m2, six crop trays with an effective area of 0.50 x 0.75 m2, could hold 18 - 20 kg of cut fruits and vegetables. The temperature in drying chamber was observed 6 oC higher than the ambient temperature after sunshine hours till the mid night during the month of June and November at Jodhpur. The dryer was experimented with drying of desert fruits (ber and date palm) and vegetables (cluster bean and carrot) for 28 hours and reduced moisture from 82.5 to 11.4 % wet basis. The simple economic analysis of solar dryer to dry 30 batch of each 18 kg of these fruits and vegetables in different season with their prevailing raw material cost and product cost can give annual profit Rs. 1,25,000 and payback period of 9 ½ month.

ABSTRACT. This paper focuses on the storage of solar thermal energy in a shell and tube type latent heat storage system.Paraffin wax was used as phase change material to store heat and water as the heat transfer fluid in the experimental study. Firstly, the performance of the simple shell and tube system has been analyzed on the basis of parameters, such as the charging time, cumulative energy stored, charging and system efficiency of the heat storage unit. Influence of factors such as the inlet temperature and mass flow rate of the heat transfer fluid on the performance of the system has been studied. A better performance was observed at higher inlet temperature and mass flow rate. In the second part of the experimentation, longitudinal fins were used to enhance the heat transfer rate and a comparative study on the performance of the system has been carried out. Results show a drastic reduction in the charging time and an increase in charging efficiency by about 20%, by the use of fins. Total energy stored is higher with the use of fins especially at higher inlet temperature of the HTF and higher system efficiency was obtained with the use of fins.

ABSTRACT. In this paper, reduced order model of latent heat thermal energy storage (LHTES) is presented with thermal conductivity enhancer (TCE) in the form of spherical capsules filled with phase change material (PCM). The numerical method is based on the two temperature non-equilibrium energy equations for heat transfer fluid (HTF) and PCM coupled with the enthalpy method to account for phase change in PCM. The effects of porosity, capsule diameter, and capsule thickness on the temperature of HTF at the outlet of LHTES for charging period are studied. It is found that the stabilization time can be increased with low porosity and low mass flow rate, whereas the capsule shell thickness negligibly influence the heat transfer process from HTF to PCM.

ABSTRACT. Implementing and sustaining clean energy systems in rural India is a development challenge that lies at the crossroads of environmental, energy, livelihood, and social issues.  It is a complex challenge that transcends clean energy technologies.   The failure of clean energy interventions stem from a misunderstanding of household decision-making processes around adoption, implementation, and maintenance of new technologies. Household decisions to take solar and other clean energy technologies must be understood within the context of livelihoods of the rural poor: the social, political, cultural, economic, and ecological dimensions of energy security, as well as access to alternative sources of energy and household strategies to meet fluctuating energy supply and demand.  We need substantial advancement in our understanding of energy transition, behavioral drivers of decisions to shift to new energy systems, and prevailing social and cultural norms that impact adoption and implementation of alternative energy technologies.  A central message of this talk is that the uptake of clean energy technologies is more complex than just utility maximization; that attributes and knowledge of an innovation and the social cultural system in which it diffuses, and the advantage of a new technology over other options are all important for sustained use of new technologies.  Therefore, the need for transdisciplinary and translational approaches in our universities is key to advancing sustained uptake and maintenance of clean energy systems such as solar and other renewables.  The talk will present ongoing transdisciplinary and translational collaborations in promoting clean energy for the poor.