Showing papers on "Energy conversion efficiency published in 1974"
Patent•
24 Jun 1974TL;DR: In this article, a light transmitting layer containing fluorescent material, the fluorescent local maximum wave length of which lies within the effective sensitivity spectrum of solar cells, is adhered on the light receiving surface of a heat collecting plate and solar cells are provided at the sides of said light transmission layer.
Abstract: PURPOSE:To improve the electric energy conversion efficiency of the converter by a structure wherein a light transmitting layer containing fluorescent material, the fluorescent local maximum wave length of which lies within the effective sensitivity spectrum of solar cells, is adhered on the light receiving surface of a heat collecting plate and solar cells are provided at the sides of said light transmitting layer CONSTITUTION:The light transmitting layer 3 containing fluorescent material, the fluorescent local maximum wave length of which lies within the effective sensitivity spectrum of the solar cells 5, is adhered on the light receiving surface of the heat collecting plate 2 and as well as the solar cells 5 are provided at the sides of said light transmitting layer 3 in the solar energy converter comprising heat transfer medium conduits 6, a heat transfer medium pipe 1, the heat collecting plate 2, which is connected with the pipe 1 to be conductive of heat, and the solar cells 5 Concretely, the light, the wave length of which the sensitivity of the solar cells 5 is low, in the solar spectra is absorbed by the fluorescent material in the light transmitting layer 3 and converted into the light, to the wave length of which the solar cells 5 are strikingly sensitive, and said fluorescent light falls on the light receiving surface of the cells 5, resulting in converting said incident light into electric energy with high efficiency As a matter of course, the light having the wave lengths of about 055-06mum, which is originally contained in the sun light itself, is efficiently collected by the cells 5
265 citations
01 Nov 1974
TL;DR: In this article, the spacing between the hot solar absorber and successive glass covers should be in the range 4 to 8 cm to assure minimum gap conductance, based on the theory and some experimental measurements.
Abstract: A useful solar-thermal converter requires effective control of heat losses from the hot absorber to the cooler surroundings. Based upon the theory and some experimental measurements it is shown that the spacing between the tilted hot solar absorber and successive glass covers should be in the range 4 to 8 cm to assure minimum gap conductance. Poor choice of spacing can significantly affect thermal conversion efficiency, particularly when the efficiency is low or when selective black absorbers are used. Recommended data for gap Nusselt number are presented as a function of the Rayleigh number for the high aspect ratios of interest in solar collector designs. It is also shown that a rectangular cell structure placed over a solar absorber is an effective device to suppress natural convection, if designed with the proper cell spacing d, height to spacing ratio L/d and width to spacing ratio W/d needed to give a cell Rayleigh number less than the critical value.
172 citations
TL;DR: In this paper, high-power microwave emission is generated when a pulsed relativistic electron beam propagates down the axis of a corrugated-wall wave guide, at a frequency such that the phase velocities of the negative-energy space charge wave on the beam and a low-order TM mode in the wave guide are equal.
Abstract: Extremely high-power microwave emission is generated when a pulsed relativistic electron beam propagates down the axis of a corrugated-wall wave guide. The radiation occurs at a frequency such that the phase velocities of the negative-energy space charge wave on the beam and a low-order TM mode in the wave guide are equal. Power levels of 500 MW are generated. The conversion efficiency of electron energy into electromagnetic energy radiation is 17%.
153 citations
TL;DR: In this paper, the properties of two-source vacuum evaporation of CdS onto single-crystal CdTe cells were investigated and shown to have a quantum efficiency as high as 0.85.
Abstract: Several different II‐VI heterojunctions show possible promise for photovoltaic conversion of solar energy. Two of these are p‐CdTe/n‐CdS and p‐CdTe/n‐Zn0.35Cd0.65S, which have a maximum solar efficiency of 17 and 23%, respectively. We report here specifically on the properties of p‐CdTe/n‐CdS cells prepared (a) by close‐spaced vapor transport of CdTe onto single‐crystal CdS, and (b) by two‐source vacuum evaporation of CdS onto single‐crystal CdTe. Cells with efficiency of 4.0% have been produced without detailed attention to optimization of cell design; these cells have quantum efficiencies as high as 0.85.
85 citations
TL;DR: In this paper, the authors reported an up-conversion of low-level ir radiation near 10 μ to the near ultraviolet using resonant two-photon pumping of the nonallowed 3s-3d transition in Na.
Abstract: We report efficient up‐conversion of low‐level ir radiation near 10 μ to the near ultraviolet. Radiation at 9.26 μ is converted to 3305 A with a photon conversion efficiency of 58% and a corresponding power gain of 16.2. The process employs resonant two‐photon pumping of the nonallowed 3s‐3d transition in Na.
79 citations
TL;DR: In this article, a study was made of the efficiency of E-V transfer from O(1 D) to CO using a molecular resonance fluorescence technique, which utilizes optical pumping from the v = 1 level of the ground state of CO by A 1 Pi-X 1 Sigma radiation.
Abstract: With the aid of a molecular resonance fluorescence technique, which utilizes optical pumping from the v = 1 level of the ground state of CO by A 1 Pi-X 1 Sigma radiation, a study is made of the efficiency of E-V transfer from O(1 D) to CO. O(1 D) is generated at a known rate by O2 photodissociation at 1470 A in an intermittent mode, and the small modulation of the fluorescent signal associated with CO (v = 1) above the normal thermal background is interpreted in terms of E-V transfer efficiency. The CO (v = 1) lifetime in this system is determined mainly by resonance trapping of the IR fundamental band, and is found to be up to ten times longer than the natural radiative lifetime. For CO, (40 plus or minus 8)% of the O(1 D) energy is converted into vibrational energy. By observing the effect of N2 on the CO (v = 1) fluorescent intensity and lifetime, it is possible to obtain the E-V transfer efficiency for the system O(1 D)-N2 relative to that for O(1 D)-CO. The results indicate that the efficiency for N2 is (83 plus or minus 10)% of that for CO.
76 citations
TL;DR: In this paper, the authors obtained fifteen percent average internal power conversion efficiency for second harmonic generation in CdGeAs2 of radiation from a TEA CO2 laser operating at 10.6 μm.
54 citations
TL;DR: In this paper, a high gain angle-tuned singly resonant LiNbO3 parametric oscillator was operated directly at 1.06 μm by a Q-switched Nd:YAG laser.
Abstract: We have operated a high‐gain angle‐tuned singly resonant LiNbO3 parametric oscillator pumped directly at 1.06 μm by a Q ‐switched Nd:YAG laser. The oscillator angle tunes from degeneracy and operates over the entire 1.4–4.4‐μm range. Output energies of greater than 1 mJ/pulse at 5 pps have been observed with a 15% energy conversion efficiency. The key to this device is the large LiNbO3 crystals fabricated from new [01.4] grown boules. Crystals up to 15 mm in diameter and 5 cm in length have been cut at the nominal 47° orientation. These crystals will potentially handle over 2 J of optical energy at 1.06 μm.
44 citations
TL;DR: In this article, a nonhydrodynamic model is developed to describe x-ray emission from laser-heated plasmas on a subnanosecond time scale, and the model is first correlated with the experiment and then is used to study the conversion efficiency of laser energy to K-line x rays in carbon, fluorine, and aluminum plamas as a function of incident laser intensity, and it is found that these conversion efficiencies peak at well defined values of input energy per area for laser pulse widths smaller than the pumping times for K−line emission.
Abstract: A nonhydrodynamic model is developed to describe x‐ray emission from laser‐heated plasmas on a subnanosecond time scale. The model is first correlated with the experiment and then is used to study the conversion efficiency of laser energy to K‐line x rays in carbon, fluorine, and aluminum plasmas as a function of incident laser intensity. It is found that these conversion efficiencies peak at well‐defined values of input energy per area for laser pulse widths smaller than the pumping times for K‐line emission. In this case, the degree and not the rate of plasma heating is important in determining the peak conversion efficiency. It is also found that peak conversion to K radiation in excess of roughly 10 or 20% occurs only when the C, F, and Al plasmas are optically thick to the Ka lines.
35 citations
TL;DR: In this article, the authors investigated the efficiency of vacuum ultraviolet generation for solid Ar, Kr and Xe excited by 10-30 kV electrons. And they found that the presence of trace amounts of O2was found to cause energy transfer from the excimer bands to longer wavelengths.
31 citations
TL;DR: A series of p-type IMPATT diodes (p+pn+) have been fabricated from epitaxially grown silicon for operation as oscillators at K a -band frequencies as mentioned in this paper.
Abstract: A series of p-type IMPATT diodes (p+pn+) have been fabricated from epitaxially grown silicon for operation as oscillators at K a -band frequencies. A maximum CW output power level of 700 mW at 29.6 GHz, a maximum conversion efficiency of 10.9 percent, and a minimum FM noise parameter, M, of 25 dB have been measured on this series of p-type diodes. A diode oscillating in a variable height radial disk cavity was frequency tuned from 27.5 to 40 GHz, covering the entire K a -band, with a 1.4 dB power variation over the tuning range. The minimum CW output power of this tunable oscillator was 360 mW at 6.5 percent efficiency.
TL;DR: In this paper, various aspects of the procedure for estimating the energy characteristics of a laser with unstable resonators are discussed, and some results of calculations are given for the general case of an inhomogeneously excited medium.
Abstract: Various aspects of the procedure for estimating the energy characteristics of lasers with unstable resonators are discussed. Some results of calculations are given for the general case of an inhomogeneously excited medium.
TL;DR: In this paper, a new method to achieve periodic reversals of magnetization, necessary to attain high mode conversion efficiencies in magneto-optic waveguides, is described by means of a periodic Permalloy structure overlaying the optical propagation path.
Abstract: A new method to achieve periodic reversals of magnetization, necessary to attain high mode conversion efficiencies in magneto‐optic waveguides, is described. It is acomplished by means of a periodic Permalloy structure overlaying the optical propagation path. With proper bias fields, we have observed an optimum dc conversion efficiency of 80±2% at 1.15 μm in a Gd0.5Ga1 iron garnet film guide.
Patent•
27 Dec 1974TL;DR: In this paper, a decomposition chamber is used to decompose NH3 into hydrogen and nitrogen by absorbing heat of decomposition from a low temperature, e.g., 300° C energy source.
Abstract: One embodiment of a low to high temperature energy conversion system includes a decomposition chamber in which ammonia (NH3) is decomposed into hydrogen and nitrogen by absorbing heat of decomposition from a low temperature, e.g., 300° C energy source. The separated hydrogen and nitrogen are then supplied to a recombination chamber wherein they recombine to produce ammonia. The recombination process is associated with a significant increase in temperature, used to increase the temperature of a fluid to temperatures on the order of 500° C.
TL;DR: In this article, an over-all peak power conversion efficiency of 21% was obtained for the experimental conditions described, thus demonstrating the attractiveness of RDP for frequency conversion applications, which is achieved in rubidium dihydrogen phosphate (RDP) through frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser.
Abstract: The efficient generation of uv radiation at 3547 A has been achieved in rubidium dihydrogen phosphate (RDP) through frequency mixing of the fundamental and second harmonic radiation of a Nd:YAG laser. An over‐all peak power conversion efficiency of 21% was obtained for the experimental conditions described, thus demonstrating the attractiveness of RDP for frequency conversion applications.
01 Jan 1974
TL;DR: In this article, the physical principles underlying the photovoltaic energy conversion are briefly outlined and the performance characteristics of solar cells like conversion efficiency are derived from material data, and the necessary power loss factors are presented.
Abstract: Conversion of sunlight into electrical energy by the use of solar cells is by far the most important method of power supply for satellites. The physical principles underlying the photovoltaic energy conversion are briefly outlined. Performance characteristics of solar cells like conversion efficiency are derived from material data. Principle and technological necessary power loss factors are presented. The state-of-the-art of the present solar cell technology and recent developments are elucidated. Economical aspects are discussed especially concerning a possible application of photovoltaic energy conversion for terrestrial power supply.
TL;DR: In this article, the maximum theoretical solar conversion efficiency was calculated for an organic photovoltaic energy conversion system based on PVK-TNF, where charge separation was assumed to take place at a Schottky barrier.
Abstract: The maximum theoretical solar conversion efficiency is calculated for an organic photovoltaic energy conversion system based on PVK‐TNF. Charge separation is assumed to take place at a Schottky barrier. At high fields (108 V m−1) the theoretical energy conversion efficiency approaches a maximum value of 2% with a 2‐eV barrier. Lower efficiencies are found for barriers greater than or lower than 2.0 eV and at lower fields.
TL;DR: Stimulated spin-flip Raman scattering in InAs has been achieved using an HF laser pump near the band-gap resonance in this paper, where thresholds were determined to be less than 20 W and conversion efficiency was estimated to be in excess of 20%.
Abstract: Stimulated spin‐flip Raman scattering in InAs has been achieved using an HF laser pump near the band‐gap resonance. Thresholds were determined to be less than 20 W and conversion efficiency is estimated to be in excess of 20%.
TL;DR: In this article, the efficiency of metal converters is investigated and a simple method for the evaluation of conversion efficiency is given, and the optimal thickness of converter plate is found experimentally.
TL;DR: In this paper, the same GaAs-Ga1−xAlxAs heterostructure material was used to make both optically excited and junction lasers and compared the performance of the two classes of lasers under pulsed room-temperature operation.
Abstract: By using the same GaAs–Ga1−xAlxAs heterostructure material to make both optically excited and junction lasers we have compared the performance of the two classes of lasers under pulsed room‐temperature operation. We find that junction lasers have higher differential quantum efficiencies for reasons which are probably inherent in the excitation technique. However, the power efficiencies are higher for the optically pumped samples; by optical excitation of a single heterostructure, we have obtained 20% power conversion efficiency, a factor of 2 better than previous results.
TL;DR: In this paper, the reliable generation of ruby second-harmonic radiation in phase-matched rubidium dihydrogen phosphate (RDP) at incident intensities of ∼ 180 MW/cm2 was reported.
01 Jan 1974
TL;DR: In this paper, mixing experiments on niobium point contacts are reported for conversion from 95 GHz to 140 MHz, and the conversion efficiency is less than predicted by the highly damped weak link model, presumably due to mixing with higher harmonics of the local oscillator.
Abstract: : Mixing experiments on niobium point contacts are reported for conversion from 95 GHz to 140 MHz. The conversion efficiency is less than predicted by the highly damped weak link model. The discrepancy is presumably due to mixing with higher harmonics of the local oscillator. The lowest noise temperature measured was T approximately equal to 100K which is of the same order as recently reported for cooled Schottky-barrier diodes. (Author)
TL;DR: A correlation between the presence of growth twins and the conversion efficiencies of solar cells made from silicon ribbons grown by the edge-defined, film-fed growth (EFG) technique has been observed as mentioned in this paper.
Proceedings Article•
01 Jan 1974
TL;DR: In this paper, a proustite crystal pumped by a krypton ion laser was used to convert infrared radiation (λ = 106 μ) to visible radiation (γ = 0689 μ) in a crystal pumped with a KI laser, and the conversion efficiency was determined for two interaction configurations, collinear and perpendicular.
Abstract: Infrared radiation (λ = 106 μ) was converted to visible radiation (λ = 0689 μ) in a proustite crystal pumped by a krypton ion laser (λ = 0647 μ) The conversion efficiency was determined for two interaction configurations, one of which was collinear and the other perpendicular In the collinear interaction the power conversion efficiency was 210–6 for focused pump and signal radiations
01 Jul 1974
TL;DR: In this article, the authors report results of research at Harwell on thermal energy conversion, which has led to the successful development of an efficient heat engine/alternator system 1 capable of delivering several tens of watts of alternating current.
Abstract: This paper reports results of research at Harwell on thermal energy conversion, which has led to the successful development of an efficient heat engine/alternator system 1 capable of delivering several tens of watts of alternating current. It has no rotating or sliding surfaces, so requires no lubrication, and is believed to be capable of operating continuously for many years without wear or need for attention. It is capable of using heat from a variety of sources and is self starting on application of heat. An electrically heated laboratory model is delivering 25 W a.c. with an overall conversion efficiency of 13%
TL;DR: In this paper, the relative effectiveness of two important neutron-induced reactions employed in track-etch imaging is analyzed, based on the formulation of a physically plausible model of radiation conversion and nuclear track formation.
TL;DR: In this article, a longitudinal pumping configuration is described whereby diffraction limited pulses of 15 nsec duration are obtained from a dye oscillator pumped by a giant-pulse single gaussian mode, ruby laser system.
TL;DR: In this article, a high/low doping profile for GaAs Schottky-barrier Read-type IMPATT diodes was combined with ion-implantation techniques.
Abstract: Epitaxial and ion-implantation techniques have been combined to form a high/low doping profile for GaAs Schottky-barrier Read-type IMPATT diodes. A c.w. output power of 1.1 W with 25% conversion efficiency was obtained at 11 GHz.