Showing papers on "Energy conversion efficiency published in 1988"
TL;DR: An analysis of published yield data reveals that nearly complete assimilation can occur during growth on substrates with a high energy content and it will be shown that utilization of the auxiliary energy source may lead to extreme changes in the efficiency of dissimilatory processes.
Abstract: A theoretical analysis has been made of carbon conversion efficiency during heterotrophic microbial growth. The expectation was that the maximal growth yield occurs when all the substrate is assimilated and the net flow of carbon through dissimilation is zero. This, however, is not identical to a 100% carbon conversion, since assimilatory pathways lead to a net production of CO2. It can be shown that the amount of CO2 produced by way of assimilatory processes is dependent upon the nature of the carbon source, but independent of its degree of reduction and varies between 12 and 29% of the substrate carbon. An analysis of published yield data reveals that nearly complete assimilation can occur during growth on substrates with a high energy content. This holds for substrates with a heat of combustion of ca. 550 kJ/mol C, or a degree of reduction higher than 5 (e.g. ethane, ethanol, and methanol). Complete assimilation can also be achieved on substrates with a lower energy content, provided that an auxiliary energy source is present that cannot be used as a carbon source. This is evident from the cell yields reported for Candida utilis grown on glucose plus formate and for Thiobacillus versutus grown on acetate plus thiosulfate. This evaluation of the carbon conversion efficiency during assimilation also made it possible to compare the energy content of the auxiliary energy substrate added with the quantity of the carbon source it had replaced. It will be shown that utilization of the auxiliary energy source may lead to extreme changes in the efficiency of dissimilatory processes.
133 citations
TL;DR: In this paper, photo-electrodes have been grown via a vapour transport technique, employing SeCl4 as transporter photoelectrochemical (PEC) solar cells with n-WSe2/I-, I2/Pt have been fabricated.
Abstract: WSe2 crystals (photo-electrodes) have been grown via a vapour transport technique, employing SeCl4 as transporter photo-electrochemical (PEC) solar cells with n-WSe2/I-, I2/Pt have been fabricated. In order to improve upon the efficiency, the effective WSe2 crystal surfaces have been etched in aqua-regia. The authors have obtained a high PEC conversion efficiency, up to 17.1%. This corresponds to the most efficient WSe2-based PEC solar cell reported so far. Evidence and arguments have been presented to show that the high efficiency ( approximately 17.1%) is achieved due to the combined effect of improved crystal quality, obtained through a SeCl4 transporter, and a decrease in the density of surface steps consequent to photo-etching.
128 citations
TL;DR: In this paper, a visible BaB2O4 optical parametric oscillator (OPO) pumped by a single-axial-mode 355-nm source has been demonstrated.
Abstract: A visible BaB2O4 optical parametric oscillator (OPO) pumped by a single-axial-mode 355-nm source has been demonstrated. An average output power of 140 mW with a signal wave conversion efficiency of 13 percent and an idler conversion efficiency of 11 percent for a total conversion efficiency of 24 percent has been achieved. The oscillator has continuously tuned from 412 nm to 2.55 microns limited by the infrared transmission range of the crystal. Through injection seeding, single-axial-mode OPO operation with a corresponding OPO linewidth of less than 3 GHz was obtained.
127 citations
Patent•
03 Aug 1988
TL;DR: In this article, a switching network for improving the conversion efficiency of a photovoltaic power supply comprises a variable coupling circuit for coupling an array of PV cells to a load resistance.
Abstract: A switching network for improving the conversion efficiency of a photovoltaic power supply comprises a variable coupling circuit for coupling an array of photovoltaic cells to a load resistance. The combined effective impedance of the network and load is varied to match the value required for maximum output power. A switching transistor (22) which connects the source module (20) to the load (30) is pulse-width modulated with a variable duty cycle determined by the control signal from the sensor circuit. A photovoltaic cell (32) similar to those comprising the photovoltaic power module (20) is used to track variations in the ambient light intensity. The open-circuit voltage of a sensor cell (32) is used to determine the proper value of duty cycle required for maximum power transfer. The output voltage of the module (20) is sampled and compared with the proper value to produce a control signal.
118 citations
TL;DR: In this paper, the progress in the field of solar energy conversion for the production of electricity and storable chemical fuels during the last decade is reviewed and the current-potential behavior of regenerative photovoltaic cells are derived and related to charge transfer processes at the solid/liquid interface.
Abstract: In the present paper the progress in the field of solar energy conversion for the production of electricity and storable chemical fuels during the last decade is reviewed. The current-potential behavior of regenerative photovoltaic cells are derived and related to charge transfer processes at the solid/liquid interface. Various cells are critically analyzed in view of their stability and conversion efficiency. A number of factors limiting the photovoltage are discussed in terms of a stabilization mechanism, trapping of minority carriers at the interface and the forward dark current. Concerning the production of chemical fuels the photocleavage of water and hydrogen sulfide, the reduction of carbon dioxide and the formation of ammonia is evaluated. The main emphasis is laid here on catalytic processes at semiconductor electrodes and particles. The principle function of catalysts being deposited on extended electrodes and particles are discussed in detail.
105 citations
18 Jul 1988
TL;DR: In this article, a phase-matching third-harmonic light generation in a β-BaB2O4 crystal was studied experimentally using a passively mode-locked Nd: phosphate glass laser as a pump source.
Abstract: The type-II phase-matched third-harmonic light generation in a β-BaB2O4 crystal is studied experimentally. A passively mode-locked Nd: phosphate glass laser is used as a pump source. At a pump pulse peak intensity ofI10=5×1010W/cm2 a third-harmonic conversion efficiency of a percent is obtained. A theoretical discussion of phase-matched third-harmonic generation in crystals of the symmetry group of β-BaB2O4 (trigonal class 3) is given. The effective nonlinear susceptibility ϰeff for type-II phase-matching is determined.
84 citations
TL;DR: In this article, symmetric and matched resonators for the fundamental wave are studied. And the authors show that with a matched resonator of 40mm length, a conversion efficiency of 10−3 is achieved with 100-μW fundamental power.
Abstract: Second-harmonic generation in Ti:LiNbO3 channel waveguide resonators is investigated both theoretically and experimentally as a means of enhancing the conversion efficiency. In particular, symmetric and matched resonators for the fundamental wave are studied. Matched resonators are shown to maximize the efficiency, which can surpass that of nonresonant guides by as many as several orders of magnitude. Experimentally, the theoretical predictions are confirmed by using a single-frequency argon-ion laser of λ = 1.09 μm emission wavelength as the fundamental source. With a matched resonator of 40-mm length a conversion efficiency of 10−3 is achieved with 100-μW fundamental power.
61 citations
TL;DR: In this paper, a fundamental study of the formation of negative hydrogen ions via surface conversion is presented, where a novel type of converter is employed, namely a pure barium metal surface.
Abstract: A fundamental study of the formation of negative hydrogen ions via surface conversion is presented. Employed is a novel type of converter, namely a pure barium metal surface. In spite of the high work function of barium compared to more conventional cesiated converters, considerable yields of negative ions were produced. Conversion efficiencies up of 4% are obtained, which is of the same order as for cesiated converters. The high negative‐ion yield is probably related to the electron density of barium, which is almost twice that of cesiuim. This is confirmed by model calculations and by UHV scattering experiments under well‐defined conditions. Furthermore, calculations showed that the hydrogen coverage of the converter increases with increasing flux of positive hydrogen ions to the surface. This behavior is confirmed experimentally. Seeding the hydrogen plasma with argon has no significant effect on the conversion efficiency. This is believed to be related to the competition between the lowering of the su...
59 citations
TL;DR: In this article, the second-harmonic generation (SHG) in channel waveguides fabricated by titanium diffusion into MgO-doped lithium niobate was studied, and a conversion efficiency of 2.4% was obtained for a 16mm-long waveguide by using a Nd:YAG laser as pump source.
Abstract: Second-harmonic generation (SHG) in channel waveguides fabricated by titanium diffusion into MgO-doped lithium niobate is studied. A conversion efficiency for SHG of 2.4%/W has been obtained for a 16-mm-long waveguide by using a Nd:YAG laser as pump source. The conversion efficiency is lower than the theoretical prediction. This difference is attributed to inhomogeneities along the waveguide. The channel waveguides used carried several modes at the second-harmonic wavelength; those modes, phase matched above room temperature (~80°C), showed substantially lower sensitivity for photorefractive damage than others phase matched at room temperature.
44 citations
TL;DR: In this paper, the performance of silicon solar cells based on a novel, laser grooved, buried contact approach is described, achieving energy conversion efficiency as high as 19.8% for cells of 12 cm2 area.
Abstract: Improvements in the performance of silicon solar cells based on a novel, laser grooved, buried contact approach are described. Independently confirmed energy conversion efficiencies as high as 19.8% are reported for cells of 12 cm2 area, as are the resistivity dependence of efficiency, spectral response data, and the results of laser beam induced current scans. The potential for further improvement is also discussed.
43 citations
TL;DR: In this paper, a mathematical model of a hybrid photovoltaic/thermal (PV/T) solar concentrating system with SSBS is presented, and the model performs computer simulations for parametric analyses to assess the performance of PV/T concentrating systems when exposed to a variety of conditions.
TL;DR: In this paper, a p-type microcrystalline SiC:H films have been prepared by ECR (electron cyclotron resonance) plasma CVD, which exhibits a dark conductivity as high as 10 S cm-1.
TL;DR: In this article, an all-solid-state pulser for the excitation of repetitively pulsed gas lasers is described, which uses thyristor switching followed by a ferrite core pulse transformer and a four-stage pulse compression system using DC biased ferrite magnetic switches.
Abstract: An all-solid-state pulser for the excitation of repetitively pulsed gas lasers is described which uses thyristor switching followed by a ferrite core pulse transformer and a four-stage pulse compression system using DC biased ferrite magnetic switches. An analysis of energy losses in the complex high voltage circuit is made, and an energy conversion efficiency of 73% overall is shown to be obtained, using commercially available ferrite materials. Interfacing of the circuit to the TEA CO2 laser is discussed.
TL;DR: In this paper, the use of resonant-tunneling diodes as varistors for harmonic multiplication was demonstrated and it was shown that even harmonics do not appear because of the antisymmetry of the current-voltage (I-V) curve.
Abstract: This paper demonstrates the use of resonant-tunneling diodes as varistors for harmonic multiplication. It is shown that efficient odd-harmonic conversion is possible and that even harmonics do not appear because of the antisymmetry of the current-voltage (I-V) curve. It is also shown that, with the proper choice of resonant-tunneling structure and pump amplitude, most of the harmonic output power can be confined to a single odd-harmonic frequency. Fifth-harmonic multiplication was demonstrated with an output at 21.75 GHz and a power conversion efficiency of 0.5 percent, and a fifth-harmonic efficiency of 2.7 percent was achieved in a circuit simulation using an improved I-V curve.
TL;DR: In this paper, a planar acoustooptic TM-TE mode converter with an efficiency of up to 90 percent was proposed and a combined acoustical/optical strip waveguide structure was developed as a mode converter, leading to strongly reduced power requirements.
Abstract: Collinear acoustooptic TM-TE mode conversion is experimentally investigated in proton exchanged Ti:LiNbO/sub 3/ optical waveguides. Their birefringence is adjusted by an appropriate annealing to allow phase matching at surface acoustic wave frequencies of about 90 MHz and 180 MHz, respectively. A planar mode converter with an efficiency of up to 90 percent is presented (87 MHz, 175 MHz). Furthermore, a combined acoustical/optical strip waveguide structure is developed as mode converter, leading to strongly reduced power requirements; only 0.3-mW acoustic power is sufficient to achieve a conversion efficiency of 50 percent. >
TL;DR: In this paper, a two-point boundary value problem has been formulated that describes the conversion between ordinary (O) and extraordinary (X) wave modes in a cold inhomogeneous plasma, and numerical solutions to this problem have been obtained for various values of the WKB parameter k0L; where k0 is the vacuum wavenumber and L the density-gradient scale length.
Abstract: A two-point boundary-value problem has been formulated that describes the conversion between ordinary (O) and extraordinary (X) wave modes in a cold inhomogeneous plasma. Numerical solutions to this problem have been obtained for various values of the WKB parameter k0L; where k0 is the vacuum wavenumber and L the density-gradient scale length. The results are compared with three different theoretical expressions for the O-X mode conversion efficiency derived by others in the WKB limit of k0 L ≫ l. Most of the results presented in this paper are obtained for a collisionless plasma with finite density near the plasma cut-off density. However, some examples are also given of wave propagation from vacuum. In these examples, collision effects are added to the equations in order to remove the singularity otherwise present at the position of the upper hybrid resonance layer.
TL;DR: Coherent vacuum-ultraviolet pulses with energy of 1.1 mJ, 2.2-nsec pulse length, and measured bandwidth ≤0.1 cm−1 have been achieved at 130 nm from four-wave mixing in Hg vapor, and conversion efficiencies of 5% have been demonstrated.
Abstract: Coherent vacuum-ultraviolet (VUV) pulses with energy of 1.1 mJ, 2.2-nsec pulse length (2 MW cm−2 unfocused), and measured bandwidth ≤0.1 cm−1 have been achieved at 130 nm from four-wave mixing in Hg vapor. Conversion efficiencies of 5% have been demonstrated in a collimated beam geometry over 1-m interaction lengths. These high efficiencies are made possible by using two-photon-resonant sum-frequency mixing through the Hg 71S level. The experimental facility assembled to produce this efficient VUV source is described, and a comparison between experimental measurements and theory is provided.
Patent•
08 Jul 1988TL;DR: In this paper, a photo-electric converting device has a plurality of emitters with a non-circular or non-dot shape in order to improve the photoelectric converting efficiency, and the distance between the adjacent emitters has a predetermined relation to the average diffusion length of the minority carriers in a base layer.
Abstract: A photo-electric converting device has a plurality of emitters with a non-circular or non-dot shape in order to improve the photo-electric converting efficiency. The distance between the adjacent emitters has a predetermined relation to the average diffusion length of the minority carriers in a base layer in order to further improve the photo-electric conversion efficiency. The device is formed to have groove structures to restrain the photo-electric conversion loss due to reflected light.
TL;DR: In this article, a rippled-wall mode converter was designed to transform the TE06 output mode of a 140 GHz gyrotron into the fundamental circular symmetric TE01 mode for low-loss propagation and further conversion to the perfectly linearly polarized quasi-optical HE11 hybrid mode.
Abstract: Oversized high-power mode converters were designed to transform the TE06 output mode of a 140 GHz gyrotron into the fundamental circular symmetric TE01 mode for low-loss propagation and further conversion to the perfectly linearly polarized quasi-optical HE11hybrid mode. The improved perturbation structures of the rippled-wall mode converters (with input- and output diameter D = 27.8 mm) were optimized by numerically integrating the proper coupled-wave differential equations. Three types of mode transformation schemes have been investigated: (a) step-by-step TE06 → TE05 → TE04 → TE03 → TE02 → TE01 conversion, (b) direct TE06 → TE01 conversion, and (c) two-step TE06 → TE04 → TE01 conversion. In all three cases the predicted conversion efficiency is approximately 98%. The type (a) transducer exhibits a relatively broad bandwidth but is very long (total length L = 4.2 m) whereas the type (b) transformer is short (L = 1.8 m) but has an extremely narrow bandwidth. The two-step converter (c) realizes a compromi...
TL;DR: Rainbow trout were sprint-trained once or twice on alternate days for a period of 6 weeks for food consumption, growth rate, conversion efficiency, and maintenance rations.
Abstract: Rainbow trout were sprint-trained (30 s duration) once or twice on alternate days for a period of 6 weeks. Swim speed for the first 10 s of a training bout averaged 11.4 bls for group 2 (trained once) and 10.2 bl s −1 for group 3 (trained twice). Food consumption, growth rate and conversion efficiency were measured over 2-week periods. Food consumption was 31-38% less for the trained groups than for the control group (group 1). The growth rates of control and trained fish increased gradually over the training period. The growth rate of trained fish was always significantly less (48-81%) than that of control fish. Although conversion efficiency was significantly less for group 3 at the beginning of training, no other significant differences in conversion efficiency were recorded. Maintenance rations were high in the initial period for all groups, but were lower than the initial values in the second and third periods. While condition factor was significantly lower for the trained groups, there were no differences in percent tissue protein, lipid, or moisture.
TL;DR: In this article, a plasma x-ray source for lithography is generated by focusing ≊30 J, 30 ns KrF laser pulses onto Cu targets at irradiances up to 2×1014 W/cm2.
Abstract: A plasma x‐ray source for lithography is generated by focusing ≊30 J, 30 ns KrF laser pulses onto Cu targets at irradiances up to 2×1014 W/cm2. Energy conversion efficiency from 249 nm laser light to x rays at 1.0 keV≤hν≤1.4 keV is measured as a function of target irradiance and the maximum efficiency is ≊2.5%. The full width half‐maximum duration of the plasma x‐ray pulse is ≊5 ns which corresponds to a peak power x‐ray conversion efficiency ≊7.5%.
02 Jun 1988
TL;DR: In this paper, a compact, blue light source using a GaAlAs laser diode and a guided-wave frequency doubler was demonstrated at room temperature, achieving a maximum harmonic output power of 1.05mW at 0.42pm.
Abstract: A compact, blue light source using a GaAlAs laser diode and a guided-wave frequency doubler is demonstrated at room temperature. The 0.84pm wave from the laser diode is frequency doubled using the Cherenkov radiation scheme in a proton-exchanged LiNbO3 waveguide. The conversion efficiency of the frequency doubler is 1.6%. Maximum harmonic output power of 1.05mW at 0.42pm was achieved for diode laser output power of 120mW, for a total conversion efficiency of 0.9%. -
TL;DR: In this article, an an rf plasma decomposition of SiH4 under a magnetic field was investigated and it was confirmed by the optical emission spectra that a high-electron-density plasma can be produced under magnetic field.
Abstract: An rf plasma decomposition of SiH4 under a magnetic field was investigated. It was confirmed by the optical emission spectra that a high-electron-density plasma can be produced under a magnetic field. High-quality a-Si films with a photosensitivity of σph/σd of 7×105 were obtained at a high deposition rate of 10 A/s under the magnetic field. The a-Si solar cells with i-layers deposited at a high deposition rate under a magnetic field have a higher open-circuit voltage and a higher conversion efficiency than those without the magnetic field; a conversion efficiency of 10.1% under AM1(100mW/cm2) illumination was obtained at a deposition rate of 10 A/s. The rf plasma decomposition of SiH4 under a magnetic field is thought to be very suitable for fabricating a-Si solar cells with a high conversion efficiency at a high deposition rate.
TL;DR: In this paper, an XeCl laser beam was used to investigate stimulated Raman scattering in H2 and in various H2-foreign gas mixtures, including Helium, neon, argon, and nitrogen.
Abstract: An XeCl laser beam has been used to investigate stimulated Raman scattering in H2 and in various H2-foreign gas mixtures. Helium, neon, argon, and nitrogen have been tested as foreign gases. In all the investigated mixtures with 50% of H2, the energy conversion efficiency to the first Stokes (353 nm) was more than 70% higher than that obtained in H2 at the same total pressure (40 bar) and pump energy (60 mJ). The dependence of the energy conversion efficiency on pump beam divergence has also been investigated.
TL;DR: In this article, the p-CdTe film was deposited by co-evaporation in high vacuum using effusion cells, which achieved an open circuit voltage Voc between 0.48 V and 0.53 V, short circuit current density Jsc = 12.5 mAcm−2, and an electrical conversion efficiency better than 3.7%.
TL;DR: A new method for frequency conversion in optical waveguides using rotationally twinned domains is proposed, and high coupling efficiency is achieved for higher-order modes.
Abstract: A new method for frequency conversion in optical waveguides using rotationally twinned domains is proposed. High coupling efficiency is achieved for higher-order modes. The index step requirements are significantly reduced. The calculated conversion efficiency in a ZnSe–ZnS0.6Se0.4 structure is 4% for 1 mW of input power over a 3-mm phase-matched length.
TL;DR: In this paper, high efficiency MIS inversion layer (MIS/IL) silicon solar cells have been fabricated by using silicon oxynitride as ultra-thin tunneling film.
TL;DR: In this article, an efficient and tunable coherent ultraviolet (360-390 nm) generation in beta-BaB(2)O(4) crystals using type-I phase matching at room temperature is presented.
Abstract: Efficient and tunable coherent ultraviolet (360-390 nm) generation in beta-BaB(2)O(4) crystals using type-I phase matching at room temperature is presented. The phase-matching angle is characterized with an alexandrite laser with a wavelength tuning range of 725-785 nm. The crystal angular bandwidth of 0.9 mrad-cm and spectralbandwidth of 1.15 nm-cm are also measured. UV output pulse energy of 105 mJ at 378 nm with 31% energy conversion efficiency is achieved.
TL;DR: In this article, mass-transported p-substrate GaInAsP/InP buried-heterostructure lasers have been evaluated with series resistances as low as 3 Omega, in good agreement with the psubstrate spreading resistance calculated using conformal mapping, and simple formulas of thermal resistances of heat generated both in the active region and in the p-InP.
Abstract: Studies have been carried out to evaluate mass-transported p-substrate GaInAsP/InP buried-heterostructure lasers, which have a number of potential advantages over the more conventional n-substrate lasers. Devices have been fabricated with series resistances as low as 3 Omega , in good agreement with the p-substrate spreading resistance calculated using conformal mapping. A further development of this theory yields simple formulas of thermal resistances of heat generated both in the active region and in the p-InP. The presently fabricated p-substrate lasers also showed CW threshold currents as low as 4.5 mA, differential quantum efficiencies as high as 34% per facet, output powers as high as 33 mW per facet, and a maximum total electrical-to-optical power conversion efficiency of 36%. >
TL;DR: In this article, a detailed thermodynamic analysis of absorption heat pumps and heat transformers is presented, where first and second law thermodynamic methods are both applied to calculate the respective energy efficiency (COP) and the energy efficiency n for the systems as well as the individual components.
Abstract: This paper presents a detailed thermodynamic analysis of absorption heat pumps and heat transformers. First and second law thermodynamic methods are both applied to calculate the respective energy efficiency (COP) and the energy efficiency (n) for the systems as well as the individual components. Using LiBr/H2O as an example, two three-dimensional T-S-X diagrams for an absorption heat pump and a heat transformer are constructed by calculating the thermodynamic properties and the chemical potentials. From the calculated COP and n values, it is concluded that AHP for heating has better thermodynamic performance than both AHP for cooling and heat transformer.