Electrical Energy Conversion Efficiency Research Articles

Green synthesis of CuO nanoparticles with leaf extract of Calotropis gigantea and its dye-sensitized solar cells applications

Green synthesized copper oxide (CuO) nanoparticles (NPs) were employed as electrocatalytic materials for the fabrication of counter electrode in dye sensitized solar cells (DSSCs). Uniform CuO NPs were synthesized by the leaves extract of Calotropis gigantea plant in aqueous medium through green synthesis. The synthesized CuO NPs were extensively characterized in terms of morphology, crystalline nature, structural, electrochemical and photovoltaic properties using various experimental tools. The synthesized CuO NPs possessed a well crystalline nature which was perfectly matched to monoclinic structure of bulk CuO. For DSSC application, a thin film of synthesized CuO NPs was prepared by the paste of CuO NPs and coated onto FTO glass using glass rod. The cyclovoltametry measurement revealed that CuO NPs based thin film showed reasonably good surface for the reduction of triiodide ions in redox electrolyte, suggesting its good electrocatalytic activity toward the iodide ions. Moderately high solar to electrical energy conversion efficiency of ∼3.4% along with high short circuit current density (JSC) of ∼8.13mA/cm2, open circuit voltage (VOC) of ∼0.676V and fill factor (FF) of 0.62 was recorded in the DSSC fabricated with synthesized CuO NPs based counter electrode.

Electrolysis of Carbon Dioxide in a Solid Oxide Electrolyzer with Silver-Gadolinium-Doped Ceria Cathode

Splitting CO2 into CO and pure O2 at high temperature through solid oxide electrolyzers (SOEs) could provide an efficient way for energy storage and CO2 utilization. Tubular solid oxide electrolysis cells, with yttrium-stabilized-zirconia (YSZ) as electrolyte, strontium-doped lanthanate (LSM) as anode, cermet of Ag-GDC (gadolinium-doped-ceria) as cathode, is fabricated and operated as SOEs for electrolysis of pure CO2. Such an SOE shows a minimum electrolyzing voltage of 0.70 V and a current density of 1359 mA cm−2 at 2 V. Its CO production rates are 3.1, 6.6 and 10.0 mL min−1 at electrical currents of 0.5, 1.0 and 1.5 A, respectively, at 800°C. The corresponding Faraday efficiencies are 88.6%, 94.3%, and 95.2%, and the electrical energy conversion efficiencies are 75.4%, 65.2%, and 56.5%, respectively. An SOE with Ag-GDC electrode is steadily operated at 1.59 V for pure CO2 electrolysis at 800°C for 18 h, suggesting that Ag-GDC is a promising cathode material for SOEs of CO2 electrolysis.

Benzodithiophene-based polymers containing novel electron accepting selenophene-incorporated pyrrolo[3,4-c]pyrrole-1,3-dione units for highly efficient thin film transistors and polymer solar cells

A new electron deficient monomer, 4,6-bis(5-bromoselenophen-2-yl)-2,5-dioctylpyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (SDPPDS), was prepared and co-polymerized with an electron rich distannyl derivative of 4,8-bis(2-ethylhexyloxy) benzo[1,2-b:4,5-b′]dithiophene (BDT) and 4,8-bis(5-(2-ethylhexyl) thiophen-2-yl) benzo[1,2-b:4,5-b′]dithiophene (BDTT) to afford polymers P(BDT-SDPPDS) and P(BDTT-SDPPDS), respectively. The optical band gaps of P(BDT-SDPPDS) and P(BDTT-SDPPDS) were estimated to be 2.03eV and 1.97eV, respectively. The estimated HOMO/LUMO energy levels of P(BDT-SDPPDS) and P(BDTT-SDPPDS) were –5.43eV/–3.43eV and–5.49eV/–3.53eV, respectively. The organic thin film transistor made from the polymers P(BDT-SDPPDS) and P(BDTT-SDPPDS) displayed an impressive hole mobility of 2×10−4cm2/Vs and 1.2×10−3cm2/Vs, respectively. The polymer solar cells (PSC) made with a device structure of ITO/PEDOT:PSS/P(BDT-SDPPDS) or P(BDTT-SDPPDS):PC70BM+3vol% DIO/Ca/Al showed a solar to electrical energy conversion efficiency of 2.26% and 4.45%, respectively.

Poly(3-hexylthiophene)/hexamine modified ZnO hybrid nanocomposite: structural, optical, thermal and electrical transport studies

This paper reports the synthesis of poly(3-hexylthiophene) (P3HT)/HA@ZnO nanocomposite by in situ polymerization and demonstrates their thermal, morphological and optoelectronic properties. Zinc oxide (ZnO) nanoparticles were prepared by the simple approach of co- precipitation method using zinc acetate dihydrate as precursor modified by hexamine (HA) acting as a capping agent. Structural and photo physical studies shows that conjugated polymer chains intimately contact with the inorganic semiconductor. ZnO has wurtzite structure with average crystallite size of 40 nm. The emission spectra indicate that modified ZnO nanoparticles results in more efficient photo induced charge transfer than that of the simple nanocomposite of P3HT/ZnO. The morphological studies revealed that the transformation of granular morphology of P3HT to the clusters in P3HT/HA@ZnO hybrid nanocomposites. Cyclic voltammeter elucidates the electrochemical behavior and the HOMO–LUMO energy levels of the nanocomposites. The results indicate that the P3HT/HA@ZnO nanocomposite has energy gap of 0.72 eV, indicating this composite has potential for the fabricating hybrid organic–inorganic solid state solar cells. A solar to electric energy conversion efficiency of 0.1238 % was attained with the system.

Material and Energy Balance of Methanol Feed 1 kW SOFC Power System

High chemical to electric energy conversion efficiency and ease capture of carbon dioxide makes solid oxide fuel cell (SOFC) very attractive for distributed power generation using natural gas, syngas, biofuel, and methanol as the fuel. A 1 kW prototype power unit was built by ITRI/Hephase using methanol as the fuel. Fig.1 is the flow chart of 1 kW SOFC power unit. The methanol is converted into hydrogen by a reformer. Electric pre-heater is used to maintain the fuel stream temperature for reformer inlet and for SOFC anode inlet. Residue hydrogen in fuel cell exhaust is combusted in an afterburner. Heat produced from the afterburner is used to heat up the inlet air stream of SOFC. Photo of this unit is depicted on Fig. 2. “HotBox” is located at up-left portion. This unit contains afterburner, electric heater, and heat exchanger. Up-right portion is the SOFC stack. Bottom portion is the electric controller/monitor. This power unit was transferred to Taiwan Power company for long-term operation and testing.A steady state material and energy balance was carried out throughout the entire SOFC system. The polarization curve and operating point used in the model calculation is depicted on Fig. 3. This curve was calculated from equation (1). The Vr, DVact, DVohm, DVconcare equilibrium cell voltage, voltage loss due to electrochemical reaction, voltage loss due to internal resistance, voltage loss due to concentration polarization.Major heat fluxes among each components and temperature of each streams were calculated. Major efficiency losses were also identified. Typical result is given on Fig. 4. Experimental data were collected. This model and parameters used in the calculation will be adjusted to fit the measured result.Authors wish to thank the financial support from BOE/MOEA (Bureau of Energy, Ministry of Economic Affairs) and NSC (National Science Council). This work was carried out by researchers under the collaboration among Hephas Energy, Industrial Technology Research Institute/Green Energy and Environment Research Laboratory, National United University, Dept. Energy Engineering, and Taiwan Power Company.

In-situ electrochemically deposited polypyrrole nanoparticles incorporated reduced graphene oxide as an efficient counter electrode for platinum-free dye-sensitized solar cells.

This paper reports a rapid and in-situ electrochemical polymerization method for the fabrication of polypyrrole nanoparticles incorporated reduced graphene oxide (rGO@PPy) nanocomposites on a ITO conducting glass and its application as a counter electrode for platinum-free dye-sensitized solar cell (DSSC). The scanning electron microscopic images show the uniform distribution of PPy nanoparticles with diameter ranges between 20 and 30 nm on the rGO sheets. The electrochemical studies reveal that the rGO@PPy has smaller charge transfer resistance and similar electrocatalytic activity as that of the standard Pt counter electrode for the I3−/I− redox reaction. The overall solar to electrical energy conversion efficiency of the DSSC with the rGO@PPy counter electrode is 2.21%, which is merely equal to the efficiency of DSSC with sputtered Pt counter electrode (2.19%). The excellent photovoltaic performance, rapid and simple fabrication method and low-cost of the rGO@PPy can be potentially exploited as a alternative counter electrode to the expensive Pt in DSSCs.

Photovoltaic Performance Improvement of Dye-Sensitized Solar Cells (DSSCs) Based on Y-Doped TiO<sub>2</sub>Thin Films

Dye-sensitized solar cells based on Y-doped TiO2thin film prepared by the hydrothermal method show a photovoltaic efficiency of 5.11%, which is higher than that of the undoped TiO2thin film (4.72%). The Y-doped films exhibit an elevated electron Fermi level,which may enhance band bending to lower the density of empty trap states.Because of this Y-doping, the Dsscs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction.

Highly efficient functional GexPb1-xTe based thermoelectric alloys.

Methods for enhancement of the direct thermal to electrical energy conversion efficiency, upon development of advanced thermoelectric materials, are constantly investigated mainly for efficient implementation of thermoelectric devices in automotive vehicles, for converting the waste heat generated in such engines into useful electrical power and thereby reduction of the fuel consumption and CO2 emission levels. It was recently shown that GeTe based compounds and specifically GeTe-PbTe rich alloys are efficient p-type thermoelectric compositions. In the current research, Bi2Te3 doping and PbTe alloying effects in GexPb1-xTe alloys, subjected to phase separation reactions, were investigated for identifying the phase separation potential for enhancement of the thermoelectric properties beyond a pure alloying effect. All of the investigated compositions exhibit maximal dimensionless figure of merit, ZT, values beyond 1, with the extraordinary value of 2.1 found for the 5% Bi2Te3 doped-Ge0.87Pb0.13Te composition, considered as among the highest ever reported.

Structural optimization of thiophene-(N-aryl)pyrrole-thiophene-based metal-free organic sensitizer for the enhanced dye-sensitized solar cell performance

In this study, we prepared thiophene-(N-aryl)pyrrole-thiophene (TPT)-based two new metal-free organic sensitizers (TPTDYE 2 and TPTDYE 3) with the aim of improving the dye-sensitized solar cell (DSSC) performance of recently reported TPT-based organic sensitizer (TPTDYE 1). The molecular structure of TPTDYE 1 was tuned by decreasing the distance between the donor and acceptor groups (TPTDYE 2) or by introducing a fluoride atom on the phenyl ring near to the electron accepting cyanoacrylic acid group (TPTDYE 3). The photophysical and electrochemical studies of the newly synthesized sensitizers revealed that their absorption and energy levels were significantly altered compared to those of TPTDYE 1. The DSSC performance of each of sensitizers TPTDYE 2 and TPTDYE 3 was investigated with and without coadsorbent and compared with those of TPTDYE 1 and standard N719. Between the two DSSCs, the one sensitized by TPTDYE 2 offered greatly improved solar to electrical energy conversion efficiency of 6.85% without coadsorbent and 7.06% with coadsorbent. The overall conversion efficiency of the DSSC sensitized by TPTDYE 2 without and with coadsorbent was found to be improved by 32% and 20%, respectively, compared with that of the DSSC sensitized by TPTDYE 1 and almost equal (98.7%) to that of the standard cell prepared from N719 under an identical condition.

Piezo-electrochemical effect in lithium-intercalated carbon fibres

In this paper we have conducted experiments to investigate the coupling between electrochemical and mechanical properties of lithium (Li)-intercalating carbon fibres (CFs). The results show promising potential for new functionalities of CFs for electrochemical actuation, sensing and energy harvesting. Li-intercalation at 1C-rate in CFs subjected to a constant tensile extension induced a free reversible longitudinal expansion strain of approximately 0.30% which can be used as mechanical actuation. Varying the tensile extension of lithiated CFs resulted in a piezoelectric response of the open-circuit potential, in the range of several mV, enabling strain sensing. If the electrical potential is kept constant during a tensile extension a piezo-electrochemical current response is found with about 50% mechanical to electrical energy conversion efficiency, enabling energy harvesting.

TiO2-Au nanocomposite materials modified photoanode with dual sensitizer for solid-state dye-sensitized solar cell

The dual-photosensitizer consisting of cadmium sulphide quantum dots (CdS QDs) and basic blue-3 (BB-3) was employed in a solid-state dye-sensitized solar cell (DSSC) composed of aminosilicate sol-gel functionalized titanium dioxide-gold nanocomposite material (EDAS/(P25-Au)nps) photoanode and degussa-TiO2 (P25) nanoparticles incorporated poly(ethylene oxide) polymer electrolyte (PEO-P25-KI-I2). The UV-vis spectral analysis revealed that a large part of visible light is absorbed by the dual-photosensitizer (BB-3 + CdS QDs), particularly in the red region of the solar spectrum, and as a result the DSSC showed improved solar to electrical energy conversion efficiency of 0.37% under simulated AM 1.5G at 100 mW cm−2 solar irradiation. The photovoltaic performance of (BB-3 + CdS QDs) sensitized solid-state DSSC was compared to the BB-3 sensitized solar cell, in which the former exhibited around ∼3-fold increase in the overall solar to electrical energy conversion efficiency than that of the later. The solar to electrical energy conversion efficiency of the standard N719 dye sensitized DSSC was found to be higher than the dual sensitizer (BB-3 + CdS QDs) employed solid-state DSSC.

Novel ruthenium sensitizer with multiple butadiene equivalent thienyls as conjugation on ancillary ligand for dye-sensitized solar cells

A heteroleptic polypyridyl ruthenium complex ‘cis-Ru(4,4′-bis(3,5-bis(5-hexylthiophen-2-yl)phenyl)-2,2′-bipyridine)(4,4′-dicarboxyl-2,2′-bipyridine) (NCS)2, MC102′, with a high molar extinction coefficient was synthesized and characterized with IR, 1H NMR, Mass, UV–Vis spectroscopy. The test cell DSSC devices constructed with 0.23cm2 active area photo-electrode in combination with an electrolyte composed of 0.6M dimethylpropyl-imidazolium iodide (DMPII), 0.05M I2, and 0.1M LiI in acetonitrile yielded solar to electric energy conversion efficiency (η) of 4.42% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell fabricated and evaluated under similar conditions exhibited η-value of 5.84%.

Energy harvesting using a PZT ceramic multilayer stack

In this paper, the interdisciplinary energy harvesting issues on piezoelectric energy harvesting were investigated using a ‘33’ mode (mechanical stress and/or electric field are in parallel to the polarization direction) lead zirconate titanate multilayer piezoelectric stack (PZT-Stack). Key energy harvesting characteristics including the generated electrical energy/power in the PZT-Stack, the mechanical to electrical energy conversion efficiency, the power delivered from the PZT-Stack to a resistive load, the electrical charge/energy transferred from the PZT-Stack to a super-capacitor were systematically addressed. Theoretical models for power generation and delivery to a resistive load were proposed and experimentally affirmed. In a quasi-static regime, 70% generated electrical powers were delivered to matched resistive loads. A 35% mechanical to electrical energy conversion efficiency, which is more than 4 times higher than other reports, for the PZT-Stack had been obtained. The generated electrical power and power density were significantly higher than those from a similar weight and size cantilever-type piezoelectric harvester in both resonance and off-resonance modes. In addition, our study indicated that the capacitance and piezoelectric coefficient of the PZT-Stack were strongly dependent on the dynamic stress.

Controllable Alternating Magnetic Technology Research for Inducing Plants Breeding on Ground

Controllable alternating induction magnetic field generation technology which induces plant seeds to breed on floor space has been developed. The incentive ferrite induction coil is used in the device to produce induced magnetic field. The common AC-DC-AC topology was adopted for the variable frequency power supply, realizing the VF. AC-DC-AC AC power inverter circuit adopts SPWM inverter frequency modulation and voltage regulation mode, realizing the effect of sinusoidal variable. In order to improve the conversion efficiency of the system electrical energy to magnetic energy, the RLC series resonant circuit is chosen in the circuit of output magnetic field. The induction magnetic field in the air gap is the work area for seeds experiment. Its adjustable frequency range: 20~200Hz, adjustable field range: 0~500Gs. The experimental study of rice seeds shows that different magnetic environment has a significant impact on the biological characteristics of rice seeds. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2326

Research on the Measurement and Control Technology of Controllable Alternating Magnetic Field Generator to Magnetized Breed

Controlled and alternating induction magnetic field generation device which induces plant seeds to breed on floor space has been developed. The incentive ferrite induction coil is used in the device to produce induced magnetic field. The common AC-DC-AC topology was adopted for the variable frequency power supply, and AC power inverter circuit adopts SPWM inverter frequency modulation and voltage regulation mode, realizing the sinusoidal VVF. In order to improve the conversion efficiency of system electrical energy to magnetic energy, the RLC series resonant circuit is chosen in the circuit of output magnetic field. Measurement and control system using DSP microcomputer measurement and control technology and digital PID control method. The frequency and intensity of inductive magnetic field in the air gap changes as the changes of current intensity in coils. The experimental study of rice seeds shows that test result is obviously better than traditional biological magnetization induced breeding technique of fixed magnetic poles.

Study on the Control Technology Device of Alternating Magnetic Field Inducing the Plants to Breed

Controlled and alternating induction magnetic field generation device which induces plant seeds to breed on floor space has been developed. The incentive ferrite induction coil is used in the device to produce induced magnetic field. In order to improve the conversion efficiency of the system electrical energy to magnetic energy, the RLC series resonant circuit is chosen in the circuit of output magnetic field. The induction magnetic field in the air gap is the work area for seeds experiment. The frequency and intensity of inductive magnetic field in the air gap changes as the current changes in coils. Its adjustable frequency range: 20~200Hz, adjustable field range: 0~500Gs. Changing the magnetic field frequency, magnetic field intensity and duration, can provide different growth environment for the seeds in order to increase production. The experimental study of rice seeds shows that the test result is obviously better than traditional biological magnetization induced breeding technique of fixed magnetic poles.

Improvement of dye-sensitized solar cells toward the broader light harvesting of the solar spectrum

Dye-sensitized solar cells (DSSCs) have been extensively evolved for the past two decades in order to improve their cell performance. From the commercialization point of view, the overall solar to electrical energy conversion efficiency should compete with other solar cells. But, due to structural restrictions of DSSC using the liquid electrolyte and a space requirement between two electrodes, the direct tandem construction of DSSCs by stacking of repeating units is highly limited. In this feature article, important research trials to overcome these barriers and a recent research trend to improve the light harvesting strategies mainly panchromatic engineering, various tandem approaches such as parallel tandem, series tandem, p-n tandem etc., have been briefly reviewed.

Influences of the electron donor groups on the properties of thiophene-(N-aryl)pyrrole-thiophene-based organic sensitizers

In this study, 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole-based metal-free organic dyes containing three different non planar electron donor groups such as methoxy or hexyloxy substituted triphenylamine and difluorenephenylamine were prepared in order to see the effect of electron donor groups on the opto-electrical properties and applied in dye-sensitized solar cells (DSSC). All three dyes showed broad absorption band in visible part of the solar spectrum (∼300nm–600nm). The dye (TPTDYE-3) containing sterically less hindered methoxy substituted triphenylamine was found to show relatively red shifted absorption compared to that of the dye (TPTDYE-4) containing hexyloxy substituted triphenylamine or the dye (TPTDYE-5) containing difluorenephenylamine. The optical band gaps of the three dyes were calculated to be 2.19eV, 2.22eV and 2.24eV, respectively, and the highest occupied molecular orbital (HOMO) energy levels of the three dyes were found to be located at 0.65V, 0.68V and 0.75V, respectively. The DSSC performance of each dye was investigated with and without coadsorbent. The maximum solar to electrical energy conversion efficiencies (η) of the DSSCs made from only sensitizer were 4.18%, 5.28% and 5.42% while those of the DSSCs made from sensitizer with coadsorbent were 5.47%, 5.58% and 5.63%, respectively.

Preparation of semiconducting copolymer and its application in nanocrystalline TiO2 solar cells

The past decade has witnessed increasing attention in the nanocrystalline TiO2 solar cells (TSSCs). In this work, we have studied a novel TiO2/PCBM/PPy solar cell based on blends of the semiconducting copolymer polypyrrole (PPy) and [6,6]-phenyl C61 butyric acid methyl (PCBM) coated titanium dioxide (TiO2) nanocrystal film to substitute the I3−/I− redox electrolyte and the dye using in DSSCs. The research by incident photon to current efficiency spectra shows that the TiO2 films had a stronger absorption in 300–500 nm light range. The performance of the resulting photovoltaic devices was investigated, and the effects of the PCBM/PPy ratio by photocurrent–voltage characteristics were researched. By the optimised PCBM/PPy ratio was 3∶1, The TSSC exhibited a short circuit current of 1·28 mA cm−2, an open circuit voltage of 0·788 V, a fill factor of 0·654 and a light to electric energy conversion efficiency of 0·622% under a simulated solar light irradiation of 100 mW cm−2.

Energy Harvesting of Thermoacoustic-Piezo Systems With a Dynamic Magnifier

This study presents a novel approach for enhancing the performance of one of the promising systems in the field of energy harvesting, namely the standing wave thermoacoustic engine. Currently, conventional thermoacoustic engines have been integrated with piezoelectric membranes to harness the acoustic energy associated with this class of engines. In these thermoacoustic-piezoelectric (TAP) harvesters, the acoustic to electric energy conversion efficiency vary typically from 10% to 15%. In this paper, an attempt is made to magnify the electric energy harnessed from the piezo membranes by providing the harvester with a dynamic magnifier. The proposed system will be referred to as a dynamically magnified thermoacoustic-piezo system (DMTAP). The main purpose of the dynamic magnifier, as implied by the name, is to magnify the strain experienced by the piezo-element. With proper selection of the design parameters of such a magnifier, the output power can be significantly increased. The theory as well as the equations governing the operation of the system before and after the addition of the dynamic magnification is presented. Numerical examples are provided to illustrate the performance characteristics and merits of the improved (DMTAP) system as compared with those of a conventional TAP.