Showing papers on "Energy conversion efficiency published in 1985"

Pyroelectric conversion cycles

Abstract: The effect of the type of power cycle upon the amount of output electrical work for a pyroelectric converter has been measured. Output electrical energy densities are reported for ceramic lead zirconate modified with Sn4+ and Ti4+ in the execution of a variety of thermal‐electrical cycles. The effect upon the energy density due to changes in the voltage cycle limits and changes in the load resistance were also studied. A conversion cycle which is an electric analog of the Ericsson cycle is shown to yield the largest output energy density (100 mJ/cm3 for a 12.6 K temperature excursion and a 28‐kV/cm electric field excursion).

Highly efficient neodymium:yttrium aluminum garnet laser end pumped by a semiconductor laser array

Abstract: In recent experiments, 80-mW CW power in a single mode has been achieved from a neodymium:yttrium aluminum garnet (Nd:YAG) laser with only 1 W of electrical power input to a single semiconductor laser array pump. This corresponds to an overall efficiency of 8 percent, the highest reported CW efficiency for a Nd:YAG laser. A tightly focused semiconductor laser end pump configuration is used to achieve high pumping intensities (on the order of 1 kW/sq cm), which in turn causes the photon to photon conversion efficiency to approach the quantum efficiency (76 percent for Nd:YAG at 1.06 microns pumped at 0.810 micron). This is achieved despite the dual-lobed nature of the pump. Through the use of simple beam-combining schemes (e.g., polarization coupling and multireflection point pumping), output powers over 1 W and overall electrical to optical efficiencies as high as 10 percent are expected.

Efficient second harmonic generation of 10‐μm radiation in AgGaSe2

Abstract: AgGaSe2 crystals for nonlinear infrared applications are being grown reproducibly. Using high‐quality, 2‐cm‐long crystals, 14% energy and 60% peak intensity conversion efficiency have been demonstrated for second harmonic generation of the pulsed output of a CO2 miniature transversely excited atmospheric laser.

Intracavity nearly degenerate four‐wave mixing in a (GaAl)As semiconductor laser

Abstract: Intracavity nearly degenerate four‐wave mixing has been demonstrated by injecting a low intensity probe beam of frequency ω−δω inside a (GaAl)As semiconductor laser operating above threshold at the pump frequency ω. Conjugated reflectivities as high as 5000 together with a 25% energy conversion efficiency are reported with only a few milliwatt pump power. Additional peaks related to the ac stark effect have been observed at a detuning which depended on the pump power. This process could be useful for the study of instabilities occurring in lasers as well as for optical amplification in laser diodes.

Improvements in silicon solar cell efficiency

Abstract: Abstract The passivated emitter solar cell (PESC) structure has been responsible for recent improvements in silicon solar cell performance. The effect of substrate resistivity upon PESC cell performance is described. Also described is the performance of cells on both 0.5 ω cm Czochralski and float zone substrates. Finally recent results are described which have resulted in 19.8% energy conversion efficiencies measured relative to NASA calibrated reference cells.

Amorphous silicon solar battery

Abstract: A flexible amorphous silicon solar battery comprising a metal foil as the substrate thereof, an insulating layer integrally formed on the metal foil, and at least one amorphous silicon photoelectric conversion portion formed on the insulating layer. The amorphous silicon photoelectric conversion portion thereof comprises an a-Si thin film having a potential barrier therein, an upper electrode and a lower electrode. The a-Si thin film is sandwiched between the upper and lower electrodes. The upper electrodes may be formed of a transparent conductive film. The transparent conductive film may be also in two layers composed of a relatively thin tin dioxide film and a relatively thick ITO film thereby to lower the resistance of transparent conductive film and to obtain a superior a-Si thin film having no impurity particles therein. A plurality of a-Si photoelectric conversion portions may be formed on the same substrate, and are connected in series with one another, to increase the output voltage thereof. The a-Si photoelectric conversion portions may be formed as forward junction and/or reverse junction types. The a-Si solar battery of this invention is flexible because of use of a metal foil with thickness of 10 to 250 μm such as stainless steel, aluminum or iron as the substrate thereof, so that it can be easily attached to a product having a curved surface thereon, such as an automobile or the like. Further, there are no problems or disadvantages, such as spallings and cracks of the a-Si thin film, or deterioration of the physical properties thereof, so that the a-Si solar battery of this invention can provide excellent conversion efficiency.

A two‐level system as a model for a photovoltaic solar cell

Abstract: The operation of a photovoltaic solar cell is discussed with a quantum two‐level system as a model. A detailed‐balance calculation is carried out, from which the parameters of the converter, illuminated by radiation from a black body, are exactly obtained in different geometries, taking into account radiative recombination processes. It is shown that in a 4π geometry (source fully surrounding the converter) with total radiative recombination, the thermodynamic efficiency is equal to the Carnot efficiency at zero current (open circuit): the converter behaves as an ideal thermal engine, fully reversible when delivering no power (the practical efficiency is evidently zero). The reversibility is ensured by the complete exchange of photons between the source and the converter. The current‐voltage relation is obtained in all cases, and it is shown that the two‐level system follows the ideal diode equation. The calculation of the thermodynamic efficiency is generalized to an energy band system (real semiconductor) with radiative recombination and is shown to be maximum at open circuit, but lower than the Carnot efficiency because of irreversibilities induced by the thermalization of carriers. The effective source temperature concept is discussed. It is shown to be valid for a two‐level system, but has less physical meaning for a two‐band system.

Combustion augmentation of extremely low calorific gases. Application of the effective energy conversion method from gas enthalpy to thermal radiation.

Abstract: 多孔性固体を使用し.ガス顕熱のふく射エネルギヘの効果的変換を行い,さらに多孔性固体下流側で燃焼用空気を排ガスにて予熱することにより断熱材を使用しない小形の燃焼器を可能にした.都市ガスを使用して希薄混合気の燃焼実験を行った結果,空気過剰率m=9.9(相当発熱量114Kcal/Nm3)というきわめて低い発熱量のガスの燃焼が可能になり,工業的にも非常に有用であることがわかった.

Phase conjugation in an optical fibre

Abstract: We report experimental studies of phase conjugation by stimulated Mandelstam Brillouin scattering in multimode fibres. A dramatic decrease in the threshold power as compared to that (104 to 105 W) typically observed in conventional media was achieved. A ruby pulsed pump with ∼ 500-ns pulses was used. For the 7-m-long fibre, the threshold power was ≈ 50 W, the degree of phase conjugation was almost one, the pump-to-Stokes conversion efficiency was about 80%. For the 130-m-long fibre, the threshold power decreased to ≈ 10 W and the pump-to-Stokes conversion efficiency reached 100%. Polarization scrambling was observed in the 130-m-long fibre, but the Stokes wave with polarization coinciding with that of the pump wave was a phase-conjugate replica of the pump, as before.

Alkali Metal Thermoelectric Conversion (AMTEC) for space nuclear power systems

Abstract: Performance parameters of the Alkali Metal Thermoelectric Converter (AMTEC) for a 100 kW electric power system have been calculated at four technological levels assuming a heat pipe-cooled nuclear reactor heat source. The most advanced level considered would operate between 1180 K converter temperature and 711 K radiator temperature at 16 percent efficiency, and would weigh 1850 kg with a radiator area of 43 sq m. In addition, electrode research studies for the AMTEC systems have been conducted utilizing an experimental test cell of Bankston et al. (1983) and Mo and several Mo-Ti electrodes. It was found that the Mo-Ti electrodes offered no improvement in lifetime characteristics over the pure Mo electrodes, however, oxygen treatment of a degraded Mo electrode restored its specific power output to 90 percent of its original specific power and maintained this level for 60 hr, thus offering a potential for lifetime stability.

High efficiency homojunction InP solar cells

Abstract: Homojunction InP solar cells with a high conversion efficiency of 18.0% have been fabricated using thermal diffusion of sulphur into p‐type InP. An open‐circuit voltage Voc as high as 0.837 V which resulted from a reduction in leakage current was attained by employing mesa etching as a method for sectioning cells on a diffused wafer. Fill factor was also increased to 82.9% owing to both a small diode ideality factor (≲1.3) and a low cell series resistance (≲0.5 Ω cm2). As a result of the improvement in these factors, a conversion efficiency as high as 18.0% (an active‐area conversion efficiency of 20.1%) under AM1.5 illumination was obtained. A phenomenon whereby shunt resistance in a mesa‐etched cell is reduced by illumination is discussed. This is due to the additional current flowing from the peripheral p‐InP region bared by the mesa etching.

Room-temperature operation of a para-H2 rotational Raman laser

Abstract: We have successfully demonstrated high‐power operation of a para‐H2 rotational Raman laser at room temperature. A photon conversion efficiency of 60% was obtained with a 10.6‐μm CO2 pump energy of 4.3 J, giving 0.85 J in the first Stokes pulse at 17.0 μm. Transient effects observed under room‐temperature conditions are also reported.

Analysis Of Spectrally Selective Liquid Absorption Filters For Hybrid Solar Energy Conversion

Abstract: Various techniques have been proposed to convert solar energy to both electric power and heat in hybrid systems. Many of these approaches are designed to utilize spectral selectivity to improve the overall conversion efficiency. Examples include spectrally selective beamsplitters and arrangements of long-wave or short-wave-pass glass filters that divide the spectrum so that photon energies are roughly matched to the energies corresponding to the solar-cell bandgaps or to efficient photothermal convertors. This paper describes the analysis of liquid optical filters that have high transmittance in the visible spectrum and high absorptance in the infrared. These qualities make it possible to capture that portion of the spectrum useful to a quantum convertor, such as a photovoltaic cell, while channeling the "excess heat" of the photons with energies below the bandgap to a thermal convertor, thereby enhancing the overall conversion efficiency of the system. The preliminary studies show that spectral responses of the tested solutions (salts in water) are primarily influenced by the cation component of the salt solution. By changing the solutions and concentrations, a variety of spectrally selective filters can be tailored to match system requirements.

Experiment and theory of ‘transparent’ metal films

Abstract: We report here the optical properties of near-transparent porous platinum films supported on p-type indium phosphide (InP). The deposition of small quantities of catalytically active metals on p-InP increases photoelectrochemical solar-to-hydrogen conversion efficiency by providing a pathway for photogenerated electrons to reduce efficiently protons in solution1. Surprisingly, efficiencies increase slowly even after fairly thick metallic layers have been deposited. These results imply that in certain conditions the metal overlayer is effectively transparent to the incident light, or even promotes the coupling of incident radiation into the bulk of the semiconductor2. We present here both experimental and theoretical evidence to show that these effects can be understood in terms of microstructure: when the metal films are sufficiently porous and built up from particles smaller than the wavelength of the transmitted light, the photon fields are screened out of the metal phase and are forced into the void structure. This increases the effective refractive index of the layer over that of the ambient and provides a better match with the substrate, while incurring negligible absorption loss.

Photoelectrochemical cell using SiC for water splitting

Abstract: Photoelectrochemical cell using silicon carbide and Pt electrodes can split water into H2 and O2 without any external bias. Maximum photovoltage was ca. 0.45 V for a photocell and 2.2V for a photocell. Energy conversion efficiency to H2 was ca. 0.4% for irradiation with a 500 W Xe lamp.

Effect of solar-cell junction geometry on open-circuit voltage

Abstract: Simple analytical models have been found that adequately describe the voltage behavior of both the stripe junction and dot junction grating cells as a function of junction area. While the voltage in the former case is found to be insensitive to junction area reduction, significant voltage increases are shown to be possible for the dot junction cell. With regard to cells in which the junction area has been increased in a quest for better performance, it was found that (1) texturation does not affect the average saturation current density J0, indicating that the texturation process is equivalent to a simple extension of junction area by a factor of square root of 3 and (2) the vertical junction cell geometry produces a sizable decrease in J0 that, unfortunately, is more than offset by the effects of attendant areal increases.

Inertial confinement fusion reaction chamber and power conversion system study. Final report

Abstract: This report summarizes the results of the second year of a two-year study on the design and evaluation of the Cascade concept as a commercial inertial confinement fusion (ICF) reactor. We developed a reactor design based on the Cascade reaction chamber concept that would be competitive in terms of both capital and operating costs, safe and environmentally acceptable in terms of hazard to the public, occupational exposure and radioactive waste production, and highly efficient. The Cascade reaction chamber is a double-cone-shaped rotating drum. The granulated solid blanket materials inside the rotating chamber are held against the walls by centrifugal force. The fusion energy is captured in a blanket of solid carbon, BeO, and LiAlO/sub 2/ granules. These granules are circulated to the primary side of a ceramic heat exchanger. Primary-side granule temperatures range from 1285 K at the LiAlO/sub 2/ granule heat exchanger outlet to 1600 K at the carbon granule heat exchanger inlet. The secondary side consists of a closed-cycle gas turbine power conversion system with helium working fluid, operating at 1300 K peak outlet temperature and achieving a thermal power conversion efficiency of 55%. The net plant efficiency is 49%. The reference design is a plant producing 1500more » MW of D-T fusion power and delivering 815 MW of electrical power for sale to the utility grid. 88 refs., 44 figs., 47 tabs.« less

High‐energy conversion efficiency amorphous silicon solar cells by photochemical vapor deposition

Abstract: Hydrogenated amorphous silicon solar cells were fabricated by photochemical vapor deposition. A three‐separate‐chamber system was newly developed to reduce the contamination of the dopant elements as well as oxygen or water originated by the loading and unloading procedure. Wide optical band‐gap hydrogenated amorphous silicon carbide was prepared using acetylene (C2H2) for the p layer. The deposition conditions for each layer were optimized and the highest‐energy conversion efficiency of 9.64% was obtained. This high conversion efficiency was mainly attributed to the large short‐circuit current which indicated that the quality of the i layer is reasonably good.

High-Energy Electric-Discharge CO 2 Laser with Easily Ionizable Substances Added to the Mixture

Abstract: Optimization of the pumping regime and of the resonator parameters, as well as the correct choice of easily ionizable additives to the active mixture of a CO2 laser excited by an SSVD ensured a specific output energy of 51 J/l and a conversion efficiency of electrical into optical energy of 22 % in an active medium volume of 16 l.

Simplified particle simulation of millimeter-wave IMPATT devices

Abstract: A simplified microscopic model for investigating energy relaxation effects in millimeter-wave IMPATT devices is presented. A statistical process is used to describe electron-hole multiplication by impact ionization from knowledge of the ionization coefficients. These coefficients are assumed to be functions of the individual energy of carriers (holes and electrons). A relaxation time formulation is used to calculate the energy of each carrier. Drift in the electric field and diffusion are modeled using the diffusive model proposed by Hockney. Simulations are carried out for silicon diodes. It is found that inclusion of the energy relaxation mechanisms modifies mainly the avalanche process for such material. The implications of these mechanisms on device performances are then discussed by calculating the large signal level dependence of the conversion efficiency and admittance for a typical double-drift structure at 100 GHz. The resulting calculations show good agreement with existing experimental data on these structures.

Optically pumped NO (A 2Σ+→X 2π) ultraviolet laser

Abstract: Lasing action on the (0,1) and (0,2) γ bands of NO at 237 and 248 nm, respectively, has been obtained by longitudinal pumping of 0.5 Torr of NO on the (0,0) γ‐band transition at 227 nm. Typical output pulse energies were 13 μJ at an intrinsic energy conversion efficiency of approximately 15%.

Improved performance of a closed-cycle self-sustained discharge-excited cw CO laser

Abstract: Detailed performance characteristics of a closed‐cycle subsonic cw CO laser excited by a transverse self‐sustained dc glow discharge are described. Using an electrode configuration which consists of a hollow‐type cathode and a planar anode, the discharge characteristics have been measured under various gas conditions. The measurements show that the discharge instability, and hence the available discharge input, are strongly influenced not only by gas temperature and total static pressure but also by gas composition. From a discharge volume of about 480 cm3, a laser output power of 406 W is extracted with an electrical conversion efficiency of 11.6% for a mixture of CO/N2/He/O2=6/16/78/0.19 at an entrance gas temperature of 156 K. Furthermore, by applying an additional cathode array, the discharge uniformity and the specific input energy have been enhanced. As a result, the maximum extracted laser output reaches as high as 729 W or 1820 W per m of discharge length, with the corresponding conversion efficiency and specific output energy of 16.3% and 125 J/g, respectively. This performance is comparable to or higher than that which has been obtained with an electron‐beam controlled discharge, a pulser‐sustained discharge, etc.

Photovoltaic device having long term energy conversion stability and method of producing same

Abstract: A photoresponsive device characterized by the capability of having photoinduced defects annealed out of the photoactive region thereof in a low temperature process. Low temperature annealability is provided by including small amounts of dopant material in the photoactive region of the semiconductor material of the device. More particularly, the incorporation of small amounts of a p-dopant, such as boron, into the intrinsic region of a p-i-n photovoltaic device lowers the annealing temperature thereof. Such low temperature annealable photovoltaic devices may be incorporated into modules designed to operate at temperatures sufficient to remove said light induced defects, thereby providing a photovoltaic module exhibiting long term stability in its energy conversion efficiency.

High Performance A–Si Solar Cells and Narrow Bandgap Materials

Abstract: High performance a-Si solar cells were developed A conversion efficiency of 115% was achieved for a textured TCO/p-SiC/in/Ag structure with a size of 1 cm 2 using the high quality i-layer fabricated by a new consecutive, separated reaction chamber apparatus A conversion efficiency of 90% was obtained with a size of 10cm × 10cm A high quality a-SiGe:H:F, which is a new narrow bandgap material for a-Si solar cells, was fabricated by a glow discharge decomposition of SiF 4 + GeF 4 + H 2 A photo-CVD method was investigated in order to improve the interface properties of a–Si solar cells A conversion efficiency of 110% was obtained with a solar cell in which the p-layer is fabricated by the photo-CVD method a-SiGe:H films were fabricated by the photo-CVD method for the first time as a narrow bandgap material for multi-bandgap a-Si solar cells

A high-power 140 GHz ammonia laser

Abstract: -Power levels of 17 kW in 0.7 μs pulses have been obtained from the 2.14 mm transition of NH 3 when optically pumped by a 65 J CO 2 TEA laser. Photon conversion efficiencies of 11 percent have been achieved. This is the first high-power laser line observed to work in the 140 GHz atmospheric window.