Faculty Publications
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Item Solar Distillation and Water Heating Systems Integration with Photovoltaic Technology(Springer, 2024) Dev, R.; Kashyap, Y.; Tewari, K.; Pal, P.Solar energy is a renewable source with three major applications: photovoltaics (PV), thermal, and daylight. A photovoltaic cell has a conversion efficiency of around 16–35%, depending upon its fabrication technology. Hence, it is observed that ~65–84% of incident solar radiation is lost as thermal energy to the surroundings. At the same time, solar thermal has vast applications, e.g., solar water heating, solar greenhouse drying, solar greenhouse crop cultivation, solar distillation, solar aquaculture, etc. Solar thermal applications have a thermal efficiency of around 20–45% depending upon fabrication materials, design, operating, and weather conditions. Integrating photovoltaic and thermal applications proved advantageous over their application with better overall efficiency. Over the years, many researchers have developed various concepts integrating these technologies to get more output, cost, and land use benefits. This chapter elaborates on different ‘PV-integrated solar distillation systems’ and ‘PV-integrated solar water heating systems’ with working principles and performances. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Molecular Engineering and Theoretical Investigation of Novel Metal-Free Organic Chromophores for Dye-Sensitized Solar Cells(Elsevier Ltd, 2015) Babu, D.D.; Cheema, H.; Elsherbiny, D.; El-Shafei, A.; Vasudeva Adhikari, A.V.In this work we report design and synthesis of three new metal free D-D-A-?-A type dyes (E1-3) with different acceptor/anchoring groups, as effective sensitizers for nanocrystalline titanium dioxide based dye sensitized solar cells. All the three dyes carry electron donating methoxy group as an auxiliary and indole as a principal donor, cyanovinylene as an auxiliary acceptor and thiophene as a ?-spacer. Whereas, cyanoacetic acid, rhodanine-3-acetic acid and 4-aminobenzoic acid perform as acceptor/anchoring moieties, respectively in the dyes E1-3. Though the dye containing 4-aminobenzoic acid unit (E3) exhibits comparatively lower ?max, it shows the highest power conversion efficiency arising from the higher electron life time and good light-harvesting capability. The DFT studies reveal a better charge separation between the HOMO and LUMO levels of E3, further substantiating the experimental results. Among the three dyes, E3 shows the best photovoltaic performance with short-circuit current density (Jsc) of 9.35 mA cm-2, open-circuit voltage (Voc) of 620 mV and fill factor (FF) of 0.71, corresponding to an overall conversion efficiency of 4.12% under standard global AM 1.5G. © 2015 Elsevier Ltd. All rights reserved.Item From Molecular Design to Co-sensitization; High performance indole based photosensitizers for dye-sensitized solar cells(Elsevier Ltd, 2016) Babu, D.D.; Su, R.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report the molecular design and synthesis of two novel organic co-adsorbers DBA-1((Z)-2-cyano-3-(5-(4-(cyclohexa-1,5-dien-3-ynyl(phenyl)amino)phenyl)-1-hexyl-1H-indol-3-yl)acrylic acid) and (DBA-2) 5-((5-(4-(diphenylamino)phenyl)-1-hexyl-1H-indol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione with D-D-A (donor-donor-acceptor) architecture. We have combined the strong electron donating triphenylamine group with indole moiety attached to different acceptors/anchoring groups, as co-adsorbers for dye-sensitized solar cells and we present for the first time, the role of anchoring/acceptor unit on their co-adsorption properties. In this study, cyanoacetic acid and barbituric acid are employed as anchoring groups in the co-sensitizers DBA-1 and DBA-2, respectively. Their electrochemical and photo-physical properties along with molecular geometries, obtained from Density Functional Theory (DFT) are employed to vindicate the effect of co-sensitizer structures on photovoltaic properties of DSSCs. We have demonstrated that the co-sensitization effect is profoundly dependent upon the anchoring/acceptor unit in the co-adsorber molecule. Devices co-sensitized using DBA-1 and DBA-2 along with HD-2 (Ru-complex of 4, 4?-bis-(1,4-benzodioxan-5-yl-vinyl)-[2,2?]bipyridine), displayed higher power conversion efficiencies (PCEs) than the device sensitized using only HD-2. In the present work, ruthenium based sensitizer, HD-2, has been chosen due to its better solar-to-power conversion efficiency and impressively higher photocurrent densities than that of standard N719. Among them, co-adsorber DBA-2, containing barbituric acid as the acceptor/anchoring group displays promising photovoltaic results and exhibited an enhanced efficiency of 8.06%. Further, good agreement between the calculated and experimental results showcase the precision of the energy functional and basis set utilized in this study. All these findings provide a deeper insight and better understanding into the intricacies involved in the design of superior co-sensitizers for development of highly efficient DSSCs. © 2016 Elsevier Ltd. All rights reserved.Item Measurement of high temperature emissivity and photothermal conversion efficiency of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO spectrally selective coating(Elsevier B.V., 2017) Jyothi, J.; Soum-Glaude, A.; Nagaraja, H.S.; Barshilia, H.C.A spectrally selective TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO coating was deposited on stainless steel substrate by unbalanced magnetron sputtering system. Each individual layer of the tandem absorber was optimized by varying the reactive gas flow rates (C2H2, N2 and O2) and target power densities (Ti, Al and Si). The optimized tandem absorber shows a solar absorptance of 0.960 and an emittance of 0.15 at 82 °C, measured using solar spectrum reflectometer and emissometer, respectively. In order to study the optical properties of the deposited tandem absorber at high operating temperatures the reflectance spectra of the tandem absorber were measured at temperatures ranging from 80 °C to 500 °C by UV–Vis–NIR spectrophotometer and FTIR spectrometers. The reflectance spectra of the as-deposited sample and after high temperature reflectance measurements did not show any significant changes. The thermal emittance of the tandem absorber at high temperatures (80–500 °C) was studied in detail. At the temperature of 200 °C, 300 °C, 400 °C and 500 °C the tandem absorber shows the emittance of 0.152–0.157, 0.181–0.19, 0.214–0.246 and 0.251–0.275, respectively with an absorptance of ~0.930. These results show the good selectivity of the tandem absorber even at high operating temperatures (e.g., 500 °C) with a photothermal conversion efficiency of 88%, thus demonstrating that the tandem absorber is suitable for solar thermal power generation applications. Reflectance and roughness data of the absorber coating post annealing in air up to 600 °C for 2 h, carried out independently, corroborated the present results. © 2017 Elsevier B.V.Item Power Quality Enhancement Using Current Injection Technique in a Zigzag Configured Autotransformer-Based 12-Pulse Rectifier(Institute of Electrical and Electronics Engineers Inc., 2018) Kalpana, R.; Chethana, K.S.; P, P.; Singh, B.This paper proposes a DC-side circuit configuration that improves the harmonic suppression ability of a 12-pulse diode bridge rectifier (DBR) using a zigzag configured autotransformer. The DC-side circuit uses a single-phase DBR along with interphase transformer which generates the required circulating current thereby modifies the DC currents at the DBR output, in turn shapes the input line current near to a sine wave. The proposed single-phase DBR is connected in parallel with the load which enables to reuse the harmonic energy thus improving the energy conversion efficiency. The zigzag configured autotransformer used for 12-pulse DBR possesses the inbuilt ability to hinder the zero-sequence components, which expel the need of zero sequence blocking transformer. The proposed configuration is analyzed, simulated in MATLAB Simulink and the simulation results are presented, which confirm the reduction of total harmonic distortion (THD) in the input line current thereby improving the power quality under large load variations. Furthermore, the viability of the proposed configuration is verified by experimental results, which confirm the suitability of the proposed configuration in industrial applications. © 1972-2012 IEEE.Item Application of voltage multiplier in 12-pulse rectifier for sinusoidal input current(Institution of Engineering and Technology journals@theiet.org, 2018) P, P.; Kalpana, R.; Singh, B.; Bhuvaneswari, G.A DC current injection circuit of a trifurcated autotransformer (TAT)-based 12-pulse diode bridge rectifier (DBR) is proposed which can help reduction of harmonics in the AC mains. The circuit at the DC side employs a voltage multiplier (VM) circuits namely voltage doubler, voltage tripler and voltage quadrupler and an interphase transformer which provides the required circulating current. This induced circulating current shapes the input AC line current near to a sine wave. The output of VM circuits is connected across the load and thereby reuses the harmonic energy absorbed by the system. Thus, improves the energy conversion efficiency of the proposed system. The TAT-based 12-pulse DBR has the implicit ability to prevent the zero sequence components thus expels the necessity of zero sequence blocking transformer. The proposed configuration is analysed, simulated in MATLAB Simulink and the simulation results are presented, which confirms the improvement in power quality parameters in the input AC line current. Further, the viability of the proposed configuration is verified by experimental results which confirm the suitability of the proposed configuration in AC-DC applications. © 2018 Springer Verlag. All rights reserved.Item Simple diphenylamine based D-?-A type sensitizers/co-sensitizers for DSSCs: A comprehensive study on the impact of anchoring groups(Royal Society of Chemistry, 2019) Kesavan, R.; Abdellah, I.M.; Singh, S.P.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein, we report the design, synthesis and characterization of a new series of simple donor-? spacer-acceptor/anchor (D-?-A) type diphenylamine based metal-free organic dyes possessing three different anchoring groups, viz. 4-aminobenzoic acid (DTP), 2-(4-nitrophenyl)acetonitrile (DTN), and barbituric acid (DTB), connected with 2-(thiophene-2-yl)-acetonitrile, as effective sensitizers and co-sensitizers in Dye Sensitized Solar Cells (DSSCs). They were subjected to photophysical, electrochemical and theoretical studies. The dyes exhibited characteristic ?abs and ?emi in the range of 445-485 and 545-570 nm, respectively. Both optical and electrochemical band gaps were found to be in the range of 2.2 to 2.35 eV. The driving forces for injection (?Ginj), recombination (?Grec) and regeneration (?Greg) processes were evaluated to understand their feasibility. Finally, the DSSC devices were fabricated employing the new dyes as sensitizers as well as co-sensitizers along with the Ru(ii) based N3 dye. Interestingly, DTP carrying 4-aminobenzoic acid as the anchoring group shows the best photoelectrochemical performance, viz. photovoltaic conversion efficiency (PCE) = 4.4%, open circuit potential (VOC) = 0.577 V, and short-circuit current density (JSC) = 9.06 mA cm-2 with a broad incident photon conversion efficiency (IPCE) spectrum. Co-sensitization of the dyes brought about enhanced VOC values, compared to the N3 dye alone. Finally, different interface resistance values obtained from the electrochemical impedance spectroscopy (EIS) circuit fitting were used to study the fundamental processes of energy conversion. © 2019 the Owner Societies.Item Evaluation of photothermal properties for absorption of solar energy by Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans(Elsevier Ltd, 2020) Vijayanandan, A.S.; Kandath Valappil, R.S.; Mohan Balakrishnan, R.M.An attempt has been made to compare the optical properties of cobalt oxide (Co3O4) nanoparticles using experimental values and theoretical predictions. Optical transmittance of the nanoparticles obtained was higher than 65% in 550–850 nm containing visible spectrum and the experimental results were in accordance with the predictive datum. The absorption coefficient peak observed is close to the predictive value and is present in the visible region of the light. In addition, there was an excellent agreement between theoretical and experimental results in extinction coefficient and refractive index. Besides, this work proposes and validates a novel idea of using Co3O4 nanofluids to enhance solar thermal conversion efficiency. Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans isolated from a medicinal plant, Nothapodytes foetida has been used to illustrate the energy storage capacity of nanofluids. Experimental results reveal that Co3O4 nanofluids have good specific absorption rate (SAR) and better photo-thermal conversion efficiency than water. Nanofluid exhibited a greater temperature gradient than pure water, which is desired. Thus the good absorption ability of Co3O4 nanofluids for solar energy indicated that it is suitable for direct absorption solar thermal energy systems. © 2019Item Effect of polarization switching on piezoelectric and dielectric performance of electrospun nanofabrics of poly(vinylidene fluoride)/Ca–Al LDH nanocomposite(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Shamitha, C.; Mahendran, A.R.; Anandhan, S.At present, highly flexible, durable, and lightweight piezoelectric nanogenerators with high-power density and energy conversion efficiency are of great interest. The present study reports a new synthetic route for Ca–Al layered double hydroxide (LDH) nanosheets and incorporation of these two-dimensional nanosheets as filler material into poly(vinylidene fluoride) (PVDF) to produce composite nanofabrics by electrospinning. The polymorphism, crystallinity, and the interaction between PVDF and LDH were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry techniques. The synergetic effect of PVDF–LDH interaction and in situ stretching due to electrospinning facilitates the nucleation of electroactive ? phase up to 82.79%, which makes it a suitable material for piezoelectric-based nanogenerators. The piezoelectric performance of PVDF/Ca–Al LDH composite nanofabrics was demonstrated by hand slapping and frequency-dependent mechanical vibration mode, which delivered a maximum open circuit output voltage of 4.1 and 5.72 V, respectively. Moreover, the composite nanofabrics exhibited a high dielectric constant and low dielectric loss due to superior interfacial polarization at low-frequency region with LDH loading, promising its potential applications in electronic devices. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48697. © 2019 Wiley Periodicals, Inc.Item A simple D-A-?-A configured carbazole based dye as an active photo-sensitizer: A comparative investigation on different parameters of cell(Elsevier B.V., 2020) Babu, D.D.; Naik, P.; Keremane, K.S.An organic photosensitizer (DP-1) with D-A-?-A architecture was systematically analyzed along with our previously reported dye N1. In the design, the dyes carry carbazole as donor, thiophene acetonitrile as ?-spacer connected to varied acceptor/anchoring unit i.e., cyanoacrylic acid (N1) and 4-aminobenzoic acid (DP-1). Generally, cyanoacrylic acid and carboxyl groups have been investigated extensively as effective electron acceptor/anchoring unit for the design of the sensitizer for dye-sensitized solar cells (DSSC) application and displayed superior photon conversion efficiency. In the present work, both the dyes were taken up for various studies focusing on photophysical, electrochemical, theoretical and photovoltaic investigation in the corresponding solar cells. From the photophysical and electrochemical studies it was established that, the both dyes show upright thermodynamic feasibility for electrochemical processes in the cell i.e., both electron and dye regeneration. Also, the DFT studies appends the existence of feasible HOMO-LUMO charge distribution. Finally, the devices fabricated by employing these dyes as sensitizer with 10 mM DCA as co-adsorbent. The device based on N1 displayed improved photon conversion efficiency compared to the cell sensitized using DP-1. This work may provide a new strategy for designing efficient photosensitizers to further ameliorate the DSSCs performance. © 2020 Elsevier B.V.