Total Conversion Efficiency Research Articles

Performance analysis of a novel solar Linear Fresnel concentrator system based on spectral beam splitting

Photothermal and photovoltaic are the most common and commercialized ways of utilizing solar energy. However, they cannot use solar energy efficiently. SBS (spectral beam splitting) technology is an efficient solar energy utilization technology that can realize the full spectrum utilization of solar energy. The current work involved: (1) Proposing a SBS-LFCs (linear Fresnel concentrator system) based on spectral beam splitting. In this system, the SBS photovoltaic panel replaces the conventional linear Fresnel concentrator lens, which can realize photovoltaic and photothermal utilization at the same time; (2) Developing a spectral splitting thin films configuration using the Needle method whose transmittance is higher than 90% against 380 nm-1100 nm band range; (3) Designing the SBS photovoltaic panel structure. The cover glass surface is covered with a SBS thin film. The SBS photovoltaic panel replaces the concentrator lens of LFCs; (4) Taking four typical days as examples, the annual power generation of a SBS linear Fresnel focusing system was predicted. The outcome indicates that the total conversion efficiency of solar thermal power in the system is 23.8%, 23.5%, 23.5%, and 23.6% on the spring equinox, summer solstice, autumn equinox, and winter solstice, respectively. Compared to conventional monocrystalline silicon cells, the photoelectric conversion efficiency has been improved by 14.6%, 12.8%, 12.5%, and 14.1%, respectively.

Advances in the development of few-cycle gigawatt-peak-power mid-IR optical parametric amplifiers pumped by Cr:Forsterite laser using non-oxide nonlinear crystals

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics.

Low complexity on-board vector calibration network for optimal microwave wireless power transmission and enhanced RF-to-DC conversion efficiency

A low complexity on-board vector calibration network for optimal microwave wireless power transmission (MWPT) efficiency is proposed in this work. The proposed technique is based on sequentially tracking the minimum power level of two antenna elements in an array for both phase and amplitude error discrimination. Unlike conventional vector calibration networks based on a down-conversion topology, the proposed architecture can perform vector calibration by only monitoring the magnitude of each antenna element. Thus, high system efficiency can be achieved by reducing hardware costs and eliminating any unnecessary power consumption by extra active devices. Further, phase and amplitude imbalances between antenna elements in an array can be accurately captured with higher precision compared to the conventional rotating-element electric-field vector (REV) method. The proposed technique achieved higher resolutions for both amplitude and phase error detection than REV, which suffers from low resolution near the maximum or minimum field crests. To verify the MWPT efficiency improvement based on the proposed calibration network, a 1 × 4 phased array MWPT system was fabricated and tested at 5.8 GHz with a reference rectenna. With the calibrated power transmission, the total RF-DC conversion efficiencies at ± 45° beamforming angles were improved by up to a maximum of 138.79%.

A novel energy recovery and storage approach based on turbo-pump for a natural gas pressure reduction station

In this research, a direct energy harvesting and storage strategy was proposed for the recovered energy from the natural gas pressure reduction station. For this purpose, a novel turbo-pump system is proposed, which consists of a turbo-expander and a water pump. The proposed plan was integrated into a gas pressure reduction station with a capacity of 300,000 Nm3/hr. In gas pressure reduction stations, a regulator reduces gas pressure, which wastes natural gas energy in the depressurization process. To recover this wasted energy, a turbo-expander has been used instead of the regulator. The designed turbo-expander shaft is connected to the pump shaft. By receiving mechanical energy from the turbo-expander, the pump transfers the water into the water towers and thus stores the energy. For this purpose, water towers with different sizes were designed and their energy storage capacity and efficiency was calculated. The obtained results showed that 15.3 GWh energy can be recovered annually, which this amount of energy is currently wasted. While harvesting this significant amount of energy from a gas pressure reduction station, emissions are also prevented. The analysis results of the designed energy storage system also showed that the total energy conversion efficiency of recovered energy from natural gas in the pressure reduction process to electrical energy in the discharge stage of the energy storage system is about 52%. Also, the average daily electrical power generated during peak consumption hours is between 0.7 and 17.9 MW. By recovering and storing wasted energy from just one gas pressure reduction station, in addition to generating electrical energy during peak hours, the emission of 4620 tons of carbon dioxide can be prevented annually. The designed energy storage system can be installed as discrete packs of energy storage in different capacities, which have high installation and flexibility.

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis

AbstractPhotocatalytic oxygen reductive H2O2 production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O2 feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC−H‐bond) through multi‐component Radziszewski reaction in an imidazole poly‐ionic‐liquid composite (SI‐PIL‐TiO2) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H2O2 production. It is found that the IC−H‐bond formed by spaced imino (−NH−) group of SI‐PIL‐TiO2 and carbonyl (−C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N2 in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI‐PIL‐TiO2 surface to establish competitive active sites for selectivity O2 chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e− oxygen reduction ensures the rapid reduction of O2. Therefore, the IC−H‐bond enables a total O2 utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H2O2 production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly‐ionic‐liquid composite without spaced imino groups (PIL‐TiO2) and TiO2, respectively.

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis.

Photocatalytic oxygen reductive H2O2 production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O2 feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC-H-bond) through multi-component Radziszewski reaction in an imidazole poly-ionic-liquid composite (SI-PIL-TiO2) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H2O2 production. It is found that the IC-H-bond formed by spaced imino (-NH-) group of SI-PIL-TiO2 and carbonyl (-C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N2 in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI-PIL-TiO2 surface to establish competitive active sites for selectivity O2 chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e- oxygen reduction ensures the rapid reduction of O2. Therefore, the IC-H-bond enables a total O2 utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H2O2 production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly-ionic-liquid composite without spaced imino groups (PIL-TiO2) and TiO2, respectively.

Energy scaling of a narrowband, periodically poled LiNbO3, nanosecond, nonresonant optical parametric oscillator

We demonstrate that 3-mm-thick, periodically poled LiNbO3 enables energy scaling of a nonresonant optical parametric oscillator operated in the narrowband mode with a volume Bragg grating at the signal wavelength. Utilizing the full available pump power at 1064 nm, we obtained maximum average powers of 2.25 and 2.08 W for the signal (1.922 µm) and idler (2.383 µm) pulses at 10 kHz, at a total conversion efficiency of 32.8%, which represents a fourfold increase in terms of peak powers over our previous work. The signal and idler spectral linewidths were ∼1nm, with pulse lengths of ∼6ns and an idler beam propagation factor of ∼5.

Cascaded Second Harmonic Generation for Deep‐UV Radiations with a 2D Nonlinear Photonic Quartz Crystal

AbstractHarmonic generation can broaden the laser wavelength in a great scope and is rich in physics, but the efficient cascaded second harmonic generation especially those directly deep into deep‐ultraviolet (DUV) with one single crystal seems to be impossible, due to the extremely strict phase‐matching conditions and relative narrow bandgap of present nonlinear optical crystals. Here, this work designs a nonlinear photonic quartz crystal where the phase difference of interacted light waves is manipulated in two dimensions and realizes an unprecedented cascaded phase‐matched 2nd–5th harmonic generation simultaneously with the photon energy up to 6 eV, representing the shortest wavelength by cascaded second harmonic generation in the solid‐state nonlinear medium. The generated light is located in the visible‐DUV region with a total conversion efficiency of 2.7%. The present nonlinear photonic quartz scheme not only provides a multi‐wavelength solid‐state laser source applied in modern devices but also develops a new route for studying the light‐matter nonlinear interaction in the DUV region.

Nano-Confined Effect and Heterojunction Promoted Exciton Separation for Light-Boosted Osmotic Energy Conversion.

The osmotic energy conversion properties of biomimetic light-stimulated nanochannels have aroused great interest. However, the power output performance is limited by the low light-induced current and energy conversion efficiency. Here, nanochannel arrays with simultaneous modification of ZnO and di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,20-bipyridyl-4,40-dicarboxylato) ruthenium (II) (N719) onto anodic aluminum oxide (AAO) to combine the nano-confined effect and heterojunction is designed, which demonstrate rectified ion transport behavior due to the asymmetric composition, structure and charge. High cation selectivity and ion flux contribute to the high power density of ≈7.33Wm-2 by mixing artificial seawater and river water. Under light irradiation, heterojunction promoted the production and separation of exciton, enhanced cation selectivity, and improved the utilization efficiency of osmotic energy, providing a remarkable power density of ≈18.49Wm-2 with an increase of 252% and total energy conversion efficiency of 30.43%. The work opens new insights into the biomimetic nanochannels for high-performance energy conversion.

The investigation of V-shaped arrays with non-uniform diameter cylinders for high performance hydrokinetic energy conversion

Harnessing hydrokinetic energy through vortex-induced vibration (VIV) is of great significance. The energy capture efficiency of VIV cylindrical arrays still has great potentials for making further progress. This paper investigates the energy conversion performance of cylinder cluster arrays with non-uniform diameter positioned at the upstream, midstream, and downstream locations, utilizing the downstream VIV enhancement effect. The cylinder arrays consist of five cylinders with non-uniform diameters of 2, 3, and 4 cm, resulting in a total of eight different V-shaped configuration scenarios. Through numerical simulation, it is found that the optimal flow velocity for maximizing the cylinder vibration amplitude is 0.8 m/s. In the condition of 0.8 m/s flow velocity, this study investigates the impact of cylinder diameter and the array arrangement on lift force, amplitude response, vortex shedding frequency, converted power, and efficiency. If the diameter of a cylinder is smaller than that of its upstream cylinder, cylinder experiences an enhanced amplitude, and the magnitude of this enhancement increases with the difference in diameters between the two cylinders. The blocking effect in the cylinder array occurs at a distance of two times the diameter. It has been observed that the small diameter cylinder demonstrates exceptional performance, achieving the highest converted power of 6.58 W (88% higher than the single cylinder) and the highest conversion efficiency of 68 % (75% higher than the single cylinder) in the convergent V-shaped array. The divergent V-shaped array achieves a maximum total converted power of 17.12 W (14% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders), while the convergent V-shaped array achieves a maximum total conversion efficiency of 44% (24% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders). This study presents an innovative perspective on the VIV enhancement effect in energy conversion, specifically focusing on multi-cylinder arrays with non-uniform diameters.

SRS conversion efficiency assessment of a single cell Raman gas mixture for DIAL ozone lidar.

A single Raman cell configuration useful for DIAL ozone lidar is designed and optimized. The conversion efficiency and flexibility of using a single Raman cell filled with a mixture of high pressure Raman active gases hydrogen (H 2) and methane (C H 4) have been examined and reported. The stimulated Raman scattering (SRS) conversion efficiency of Raman active gases with different total cell pressures and the volume mixing ratio excited with a focused, frequency quadrupled Nd:YAG laser with a maximum pulse energy of 25mJ and a pulse duration of 10ns at 100Hz repetition rate are examined in detail. The gas combination of H 2:C H 4 emits a coaxial beam of two wavelengths, 288.4nm (C H 4) and 299.1nm (H 2), with a maximum total conversion efficiency of about 45%. The optimum volume mixing ratio for generating the required wavelength pair with almost equal energies is found to be 2:1 (H 2:C H 4) at a total cell pressure of 18bar. The contribution of cascade Raman scattering (CRS) and four-wave mixing (FWM) to the higher order Stokes lines is examined. The laser attenuation due to soot formation under various mixing ratios in the cell is also presented.

Spectrally Selective Ultra‐Broadband Solar Absorber Based on Pyramidal Structure

Here, a spectrally selective solar absorber is explored and an ultra‐broadband solar absorber is proposed based on pyramidal structure. The finite‐difference in time domain (FDTD) software is used to model the spectral characteristics and magnetic absorption patterns of this absorber. The emissivity of the absorber is less than 20% in the far‐infrared band over 6000 nm, showing good selectivity, and the total solar thermal conversion efficiency is very close to that of an ideal truncated selective solar absorber by analyzing the performance of our proposed absorber‐related indexes. By studying the high absorption band of the absorber, the selectivity can be better investigated in depth. Here, 200–4000 nm is chosed as the depth study band. The absorber possesses an ultra‐wide bandwidth of 3554 nm and an average absorption of over 97.4%, and in the 200–3754 nm band, the absorber has an ultra‐high absorption rate of more than 98.3%, and its thermal emitter has a high emission efficiency of 94% at a temperature of 1000 K. Notably, the weighted average absorption in the 280–4000 nm band at AM1.5 is as high as 98.86%, with a loss of only 1.14%. The ultra‐broadband absorption property of this solar absorber is mainly a joint effect of surface plasmon resonance coupling.

Luminescence coupling in 28.4%-efficient tandem solar cell utilizing 20.8%-efficient perovskite minimodule stacked on silicon cell

The total power conversion efficiency (PCE) of 28.4% with an aperture area of 64 cm2 on a four-terminal (4T) tandem solar cell with a 20.8% efficiency-semitransparent perovskite module (SPM) with a series interconnection structure and a conventional passivated emitter and rear cell type crystalline silicon solar cell is independently confirmed. This is the independently confirmed record PCE of a 4T perovskite and crystalline silicon tandem solar cell with a structure having the same active area for both top and bottom cells. The impact of the luminescence coupling monitored by the silicon solar cell in the 4T tandem solar cell was investigated based on electrical properties of the top SPM analyzed by a simple one-diode equivalent circuit model.

Theoretical and conceptual framework to design D-π-A type organic dyes for application dye-sensitized solar cells

The optimized structures and absorption spectra of five D-A-type organic dyes (M1, M2, M3, M4, and M5) were investigated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). These dyes contain the same electron acceptors and -spacers but distinct 3,6- and 2,7-carbazole electron-donating groups. The results showed coplanar geometries for the dyes, which implied strong conjugation. When intramolecular charge transfer was investigated, it was discovered that 3,6-carbazole had a better capacity to give electrons than 2,7-carbazole. These dyes' projected orbital energy levels indicate that excited dyes might successfully decrease by electrolyte while oxidized dyes could successfully inject electrons into semiconductor conduction bands. The study investigated the suitability of different dyes for use in dye-sensitized solar cells (DSSCs) and found that the M2 dye, which contains a thio group as the terminal electron donor, exhibited the most promising optoelectronic properties. In particular, M2 had a narrow energy gap, superior optical qualities, optimal FMO energy levels, the lowest total value, and greater GInject and GReg values compared to the other dyes tested. These factors contributed to M2's superior photosensitizing performance, suggesting that using M2 in DSSCs may lead to higher optoelectronic characteristics and total energy conversion efficiency compared to using other dyes.

Sustainable hydrogen production through coupling isopropanol-butanol-ethanol with enhanced heat recirculation

The utilization of isopropanol-butanol-ethanol (IBE) to clean energy effectively mitigated the problems of environmental pollution and sustainable energy regeneration. In order to improve the utilization efficiency of ethanol and isopropanol in IBE, a liquid double-layer porous media burner was designed. And the combustion characteristics with different porous pellets and isopropanol ratios were studied. The results indicated that the mole fraction of hydrogen decreased with the increasing pellet diameter, and the lower heating value of syngas reached the highest value of 82.0 MJ/Nm3 when the pellets possessed two holes. Meanwhile, the peak temperature reached the maximum of 1009 K when the water content was 20% due to the sufficient combustion. And the isopropanol was conducive to the improvement of the total energy conversion efficiency. In addition, the yields of hydrogen and carbon monoxide were improved by 23.7% and 30.5% when the velocity increased from 10 to 12 cm/s. These results showed that the combustion of ethanol and isopropanol in porous media burners achieved the sustainable production of hydrogen and efficient utilization of IBE biofuels.

A high-energy Ho: YLF MOPA system pumped by Tm: YAP lasers

This paper introduces a high-energy Q-switched Ho: YLF master oscillator power amplifier (MOPA) system pumped using linearly polarized Tm: YAP lasers. In this system, the pulse repetition frequency was 100 Hz, and an 84.7 mJ Ho laser was generated with a total pump power of 102.3 W, corresponding to a total optical conversion efficiency of 8.3%. The oscillator yielded a maximum output energy of 20.0 mJ and pulse width of 19.0 ns, corresponding to a peak power of 1.05 MW. Moreover, the amplifier delivered a maximum output energy of 84.7 mJ and pulse width of 18.0 ns, corresponding to a peak power of 4.70 MW. In addition, the system exhibited an excellent beam quality in both directions, with the M2 factors better than 1.1 and 1.3 at the oscillator and amplifier, respectively.

Enhanced high-temperature thermal stability of the novel MoAlSiN-based solar selective absorbing coatings by optimizing the multilayer structure

Solar selective absorbing coating (SSAC) plays an important role in the high-temperature concentrated solar power system. The high thermal stability of SSAC above 600 °C has been a big open question for molten salt concentrated solar power projects. In our work, the TiN/Mo/MoAlSiN/MoAlSiON/SiO2 and the TiN/Mo/MoAlSiN/Si3N4/SiO2 SSACs are developed for getting high-temperature thermal stability, besides excellent spectral selectivity. The solar spectral absorptivities of the MoAlSiN/MoAlSiON and MoAlSiN/Si3N4 SSACs are 95.2% and 93.2%, respectively. While the infrared emissivities of the MoAlSiN/MoAlSiON and MoAlSiN/Si3N4 SSACs are controlled below 10.6% and 10.5% at 400 °C, respectively. The novel MoAlSiN/Si3N4 SSAC deposited on quartz can maintain thermal stability even after heat treatment at 800 °C for 200 h in vacuum, which is one of the best results in the research field for high-temperature SSACs. It is found that the choice of suitable materials without oxygen and the elimination of interfacial thermal stress are very important for improving thermal stability. Furthermore, the practical total energy conversion efficiencies of the MoAlSiN/Si3N4 SSAC at 600 °C–800 °C are always above 57%. When the activation energy is assumed as 180 kJ/mol, the estimated service life of the MoAlSiN/Si3N4 SSAC at 600 °C is more than 25 years.

Highly transient stimulated Raman scattering in SrMoO4 under ultrafast laser pumping with a controllable chirp.

For the first time, to the best of our knowledge, we demonstrate highly transient, multiwavelength, single-pass Raman generation with combined frequency shifts on two Raman modes of an SrMoO4 crystal with high total Raman conversion efficiency of up to 48% in conditions of competition with self-phase modulation (SPM). A 58-mm-long SrMoO4 crystal was used as the active medium under pumping by the 1030-nm, 40-µJ laser pulses with controllable dispersive stretching in a range of 0.25-6 ps at negative and positive chirping. The pump pulse chirping was optimized for both high- and low-frequency Raman shifts on the primary (888 cm-1) and secondary (327 cm-1) Raman modes of the crystal. At the optimal conditions, four Stokes components of stimulated Raman scattering (SRS) radiation with high- and low-frequency Raman shifts at the wavelengths of 1066, 1134, 1177, and 1261 nm were efficiently generated.

Analysis of optimal expansion dynamics in a reciprocating drive for a micro-CAES production system

This paper presents the unique design and processing conditions of a micro-CAES device that generates, stores and delivers electrical energy with highly efficient total energy conversion. The micro-CAES installation is divided into six parts, where air, the energy carrier, is compressed, stored, heated and expanded in appropriate sections. We focus mainly on the post-preparation section, where the air mass flow is pulse heated and controlled by Pulse Width Modulation (PWM), and the expansion section, where multiple piston drives are used to achieve maximum energy conversion efficiency or the required amount of electricity to be fed into the grid. We discover that the controllability of expansion process performance is improved by exploiting the inertia of the following elements in multiple reciprocating engines: piston, piston rod, connecting rod, crank, and crankshaft, connected with air injection dynamics and pulse heating by Thermal Energy Storage (TES). Furthermore, we investigate the efficiency using our own zero-dimensional mathematical model illustrating the complex dynamics of air processing. The mathematical model was compared with experimental data for the single-drive air expander, showing qualitatively and quantitatively satisfying model reliability. Moreover, we performed a sensitivity analysis to determine the best number of reciprocating drives involved in the expansion section and the best operating conditions. The use of the PWM function of mass flow of air supplied the expander with an index of 0.5 together with pulsating air heating in the expander installation, including three- reciprocating drives, allows a maximum total energy conversion efficiency of 81%. The presented piston drive expander seems to be a promising solution for micro-CAES in residential and industrial applications, especially where additional low-temperature waste heat is available, and an intermittent control strategy is implemented.

Overall evaluation of a multi-stage reverse electrodialysis reactor series system for organic wastewater treatment and power generation

A multi-stage reverse electrodialysis reactor (REDR) series system for organic wastewater treatment and power generation is proposed in this paper. An energy evaluation method is developed for the first time by analyzing the electrical energy and oxidative degradation energy conversion efficiencies of the system. The influences of the current and feed solution velocity on the overall performances of the system are investigated by experiments. Results demonstrate that a high current can enhance the gross output power but reduce the net output power and total energy conversion efficiency. A peak value of the total COD removal can be obtained at an appropriate current. A low feed solution velocity can improve the performance of the system except for the lower net output power. Although the electrical energy conversion efficiency reduces as the serial number of REDR increases, the oxidative degradation energy conversion efficiency increases significantly, which results in the total energy conversion efficiency enhancement. Under the given experimental conditions, the maximal values of the net output power, total COD removal and total energy conversion efficiency are 1.05 W, 450.98 mg·L−1, and 11.41%, respectively.