Solar Spectrum Splitting Research Articles

Performance investigation of a building-integrated collector based on spectrum splitting technology

Based on solar spectrum splitting technology, a novel concentrating photovoltaic/thermal (CPV/T) solar collector is proposed, which primarily composed of six Fresnel collector units with separate photovoltaic and photothermal modules. The compact overall structure is optimally designed that can be effectively integrated with ordinary buildings while supply both electrical and thermal energy. The proposed collector achieves the maximum annual average optical efficiency when installed north–south axially with a tilt angle approximately equal to the installation latitude, as a 64.97 % in Nanjing (32°N). Simulation analysis shows that the main influencing factors of the system performance are direct solar irradiance, working medium mass flow, and optical efficiency, the theoretical outlet working medium temperature can reach 150 °C while the photovoltaic and photothermal efficiencies are 12.37 % and 39.74 % when the normalized temperature difference T* is 0.06. Further, to verify the theoretical/simulation analysis results, the outdoor experimental tests are conducted and show that the optimal inlet working medium mass flow is 10.8 kg/h, while the efficiencies are 5.99 % and 27.59 %, respectively, that is, the proposed system comprehensive thermal efficiency can reach 43.35 %. The comparative analysis of theoretical research and experimental tests shows that the proposed system has rationality and practical value, which can provide guidance for practical engineering.

Experimental study of a concentrating solar spectrum splitting system for hybrid solar energy conversion

Spectral beam-splitting represents a potential approach to enhance energy conversion in solar concentrating systems. This study introduces a novel hybrid solar concentrator system, comprising a dish reflector with a two-axis tracking system and an affordable optical linear system that divides the concentrated solar beam into distinct visible spectral bands. Experimental investigations were conducted, encompassing an optical analysis of the splitter system and an assessment of photovoltaic and thermal power generation from the prototype throughout a day with solar tracking. Results indicate that the splitter system achieved a transmissivity of 76 % within the 400–800 nm range with clear separation between spectral bands, demonstrating system reliability. Spectral band dimensions remained relatively constant throughout the day, with widths of 0.460 cm, 0.550 cm, and 0.700 cm for red, blue, and yellow bands, respectively. The photovoltaic cell exposed to the yellow band exhibited the highest power and current intensities, with power densities of 15 mW/cm2 at noon, compared to 12 mW/cm2 for the blue and 5 mW/cm2 for the red bands. The system also recovered thermal power, reaching a maximum of 190 W around noon. The paper discusses suitable photovoltaic cell types for each band color and explores opportunities for improved efficiency and large-scale implementation.

Photothermal conversion potential of full-band solar spectrum based on beam splitting technology in concentrated solar thermal utilization

It is still a great challenge for the concentrated solar thermal (CST) technology to promote the utmost out of solar energy further because the CST's receiver generally discards the longer wavelength spectra to prevent radiative heat loss due to high temperatures. Spectrum splitting is a well-known technology generally used in multi-energy cogeneration devices, such as Photovoltaic/thermal (PV/T) systems, aiming to improve photoelectrical efficiency. In this study, the solar spectrum splitting technology is employed in the CST system to take full advantage of solar radiation through enhanced absorptions and conversions of piecewise solar radiation. The exergy efficiency of a beam-splitting photothermal (BSPT) system is used to evaluate its effectiveness. Here, the mechanisms of beam splitting under different splitting wavelengths (λsp) and concentration ratios (Cr) are investigated. Furthermore, the influence of the split number is evaluated, and the performance of the dual-segment BSPT system is compared with traditional photothermal systems with real and assumed coatings. It shows that beam splitting can play an excellent role in improving exergy performance. The exergy efficiency improvement ratio of the BSPT stabilizes at around 9% when λsp is 1300 nm, and the proposed dual-segment BSPT system can maintain an excellent performance even under off-design working conditions.

Optimal design and performance assessment for a solar powered electricity, heating and hydrogen integrated energy system

Incorporating solar energy technologies into integrated energy systems (IES) plays an increasingly important role to mitigate energy supply shortages and climate challenges. However, the low efficiency of solar energy utilization and land limitation for system deployment greatly restrict the development of the solar powered IESs. In this paper, a solar powered electricity, heating and hydrogen IES based on photovoltaic (PV), photothermal (PT) and photocatalysis of hydrogen production (PH) is proposed and investigated. The system comprises solar radiation spectrum splitting technology, PV, PT, PH, electric heating device, compressive heat pump, solid oxide fuel cell, absorption heat pump and energy storage components. A component sizing method based on a region contraction algorithm is employed to find the system optimal design with minimizing the cost of energy. Two scenarios of the solar powered IES based on solar spectrum splitting unit and independent energy supply unit are analyzed and compared. The results show that the solar powered IES can completely meet the electricity, heating and hydrogen energy demands and achieve cost savings for consumers. Compared to independent energy supply unit-based IES, the use of solar spectrum splitting unit can significantly improve the total energy efficiency by 21.74% and reduce the land area for solar capture by 52.5%, but increase the cost of energy by 27.3%.

A concentrated solar spectrum splitting photovoltaic cell-thermoelectric refrigerators combined system: Definition, combined system properties and performance evaluation

Currently, a concentrated solar spectrum splitting photovoltaic cell driven semiconductor thermoelectric refrigerator has no relevant report. In this work, a new style model of the concentrated solar spectrum splitting photovoltaic cell-thermoelectric refrigerators (CSSPV-TERs) combined system is established. On the basis of numerical calculation and theoretical study in detail, the influences of the critical parameters on the property of the CSSPV-TERs combined system are analyzed and evaluated. The total efficiency of the CSSPV-TERs combined system is 23.4%. Meanwhile, the current density J, structural factor c and numbers of thermoelectric devices N has been optimally selected to obtain the best COP. The three critical optimal parameters, N = 7, J = 11.7 A/cm2, and c = 0.000125 cm−1, of the CSSPV-TERs combined system can be obtained, which cause the maximum COP, i.e., COPmax = 0.078. The maximum COP and total efficiency of the CSSPV-TERs combined system are superior to other thermoelectric refrigeration combined systems. The research results and new model not only can provide a valuable reference and theoretical support for the optimal design of the novel solar cell driven thermoelectric refrigeration system, but also improve the conversion efficiency of the combined system by efficiently utilizing full-spectrum solar energy.

Effective bandwidth approach for the spectral splitting of solar spectrum using diffractive optical elements.

Spectral splitting of the sunlight using diffractive optical elements (DOEs) is an effective method to increase the efficiency of solar panels. Here, we design phase-only DOEs by using an iterative optimization algorithm to spectrally split and simultaneously concentrate solar spectrum. In our calculations, we take material dispersion into account as well as the normalized blackbody spectrum of the sunlight. The algorithm consists of the local search optimization and is strengthened with an outperforming logic operation called MEAN optimization. Using the MEAN optimization algorithm, we demonstrate spectral splitting of a dichromatic light source at 700 nm and 1100 nm with spectral splitting efficiencies of 92% and 94%, respectively. In this manuscript, we introduce an effective bandwidth approach, which reduces the computational time of DOEs from 89 days to 8 days, while preserving the spectral splitting efficiency. Using our effective bandwidth method, we manage to spectrally split light into two separate bands between 400 nm - 700 nm and 701 nm - 1100 nm, with splitting efficiencies of 56% and 63%, respectively. Our outperforming and effective bandwidth design approach can be applied to DOE designs in color holography, spectroscopy, and imaging applications.

Dispersive Optical Systems for Highly-Concentrated Solar Spectrum Splitting: Concept, Design, and Performance Analyses

We present a concept design of a solar spectrum splitting system that enables highly-concentrated solar energy harvesting over the entire AM1.5 spectral range. After passing through an array of the dispersive optical system (DOS) module composed of a grating structure and dispersive prisms below a concentrating lens, incident sunlight can be separated into two wavelength bands of visible (VIS) and infrared (IR) ranges, which can then be focused onto corresponding solar receivers. Based on the spectral response of typical crystalline silicon solar cells, the VIS wavelength band is selected from 0.4 μm to 1.2 μm to contribute to photovoltaic (PV) conversion to generate electricity. Meanwhile, the IR band in longer wavelength ranges (1.2 μm ≤ λ ≤ 2.5 μm), which does not contribute to PV conversion, can be simultaneously used for solar thermal applications such as water heating and thermoelectricity. In this paper, various design parameters (e.g., focal length of a concentrating lens, groove density of a grating, geometry of dispersive prisms, material combination of optical components, etc.) have been investigated to determine an optimum set of system configurations, using optical design software (Zemax OpticStudio 14.2). Our simulation studies validate that the DOS is able to split incident AM1.5 solar irradiance into the two wavelength bands of the VIS and IR ranges and focus each wavelength band with concentration factors as high as 798× and 755× on the same focal plane, respectively. Such high concentration factors for both wavelength bands can be actualized due to the additional optical components used—a grating structure and dispersive prisms, which allow to minimize optical aberrations through both diffraction and refraction. The proposed DOS, designed with commercially available optical components, has the potential to widen the use of the sun’s spectrum by allowing effective PV conversion of solar cells under high concentration with tolerable optical system losses and concurrently converting the remaining solar irradiation into useful energy for a broad range of thermal applications.

Optimization and maximum efficiency of concentrating photovoltaic cell‐gas turbine system with spectrum splitting

AbstractThe spectrum splitting system (SSS) is an efficient approach to relieve the energy losses in the solar cell and boost the efficiency of solar energy utilization. A model of the concentrated solar spectrum splitting photovoltaic (PV) cell‐gas turbine (GT) hybrid system is established to evaluate the performance of the system and predict the maximum efficiency. The numerical calculations show that the area ratio of the solar collector to the PV cell significantly affects the maximum efficiency of the spectrum system, but most of the previous studies are not considered. The maximum efficiency of the system is 50.6% when the parameters including the cell voltage, collector temperature, and band gap energy of the PV cell are optimized at the same areas of the collector and PV cell. The proposed SSS can achieve the maximum efficiency of 52.3% when the area ratio of the collector to the PV cell is further optimized. The results obtained are compared with those of a single concentrating PV cell or solar‐powered GT, and consequently, the advantages of a concentrating spectrum splitting PV cell‐GT hybrid system are revealed.

Sensitivity analysis of the theoretical performance of semiconductor upconversion nanostructures

Detailed balance models of the performance of upconverter-backed single-junction solar cells show significantly improved solar cell efficiency of over 47% under 1-sun and 63% under concentration. Realizing these predicted gains, however, requires finding or engineering materials that can realize the upconversion performance needed. Semiconductor upconversion heterostructures show the greatest potential in this respect, with over 39% solar cell efficiency predicted using a kinetic rate model to describe the upconverter photophysics. Although the kinetic rate model used was based on realistic material parameters, material design and engineering requires trade-offs that should be informed by a sensitivity analysis of the upconverter kinetic rate model assumptions. Here, we analyze the robustness of the kinetic rate model by considering how the internal upconversion quantum efficiency is affected by variations in the solar spectrum splitting (i.e., photon absorption energy ranges), upconverter absorption cross section, carrier relaxation and recombination rates, and solar concentration. We further analyze the upconverter-backed solar cell performance as a function of these variations using detailed balance methods. The results show that the theoretical performance of this upconversion paradigm under concentrated sunlight agrees with previous models and exceeds 60% solar energy conversion efficiency. More importantly, the results show that the predicted performance is relatively insensitive to the assumptions made in the model, suggesting that practical realization of such a semiconductor upconverter heterostructure paradigm is possible.

Deep Defect States in Wide-Band-Gap ABX3 Halide Perovskites

Lead bromide-based halide perovskites are of interest for wide-band-gap (>1.75 eV) absorbers for low-cost solar spectrum splitting to boost solar-to-electrical energy conversion efficiency/area by ...

Theoretical and experimental performance of a two-stage (50X) hybrid spectrum splitting solar collector tested to 600 °C

A hybrid concentrating photovoltaic/concentrating solar power spectrum splitting collector has been designed, developed, and experimentally tested. The two-stage optical system pairs a parabolic trough with a compound parabolic concentrating secondary, generating 50X geometric concentration on the thermal absorber. Double-junction indium gallium phosphide/gallium arsenide solar cells integrated into the secondary reflector generate electricity from photons with energy greater than ∼1.4 eV and reflect the remaining lower energy infrared photons to the thermal absorber for optimal spectral utilization. Simulations predict an optical efficiency of 64%, thermal efficiency of 52% at 600 °C, and efficiency of the back-reflecting concentrating photovoltaic subsystem of 6%. The collector has been developed into a working prototype and tested on-sun up to 600 °C using suspended solid particulate (alumina based) heat transfer fluid. The prototype demonstrates an optical efficiency of 63% and a net solar-to-electric efficiency of the concentrating photovoltaic subsystem of 4%. Thermal efficiency is much lower in the prototype collector and the potential causes have been examined. Overall, this work demonstrates a two-stage collector design, the ability of back-reflecting solar cells to operate as spectrum splitting devices, and the feasibility of an internally circulated solid particulate heat transfer fluid which enables high temperature operation beyond what is currently achievable with existing heat transfer fluids.

Maximum efficiency and parametric optimum selection of a concentrated solar spectrum splitting photovoltaic cell-thermoelectric generator system

An updated model of the solar spectrum splitting photovoltaic cell-thermoelectric generator system is used to derive the analytical expression of the systemic efficiency. The cutoff energy of the system, cell voltage, and dimensionless current of the thermoelectric generator are optimized. Particularly, the influences of the area ratio of the collector to photovoltaic cell on the performance of the spectrum splitting system are discussed in detail. The maximum efficiencies of the spectrum splitting system are calculated for given solar concentration factors. The results obtained are compared with those of the single photovoltaic cell with the same solar concentration factor. It is found that the maximum efficiency of the system can be further improved when the area ratio is optimized. The expressions of the upper and lower bounds of the optimized area ratio are derived. The spectrum splitting system can more efficiently harvest the full solar spectrum than the single photovoltaic cell, especially at low solar concentration factors. For example, when solar concentration factors are, respectively, equal to 30 and 100, the maximum efficiencies of the spectrum splitting system attain 39.5% and 40.2% and increase approximately 2.67% and 2.19%, compared to those of the single photovoltaic cell.

Efficient and stable tandem luminescent solar concentrators based on carbon dots and perovskite quantum dots

Luminescent solar concentrator (LSC) can serve as large-area sunlight collectors, suitable for applications in building-integrated high-efficiency and low-cost photovoltaics. Inorganic perovskite quantum dots (QDs) are promising candidates as absorbers/emitters in LSCs, due to their high quantum yields (close to 100%), possibility of tuning size and chemical composition and broad absorption spectrum and high absorption coefficient. However, despite their great potential for technological development, LSCs fabricated using colloidal perovskite QDs still face major challenges such as low optical efficiency and limited long-term stability. Here we report a large-area (~ 100 cm2) tandem LSC based on nearly reabsorption-free carbon dots (C-dots) and inorganic mixed-halide perovskite QDs spectrally-tuned for optimal solar-spectrum splitting. The as-fabricated semi-transparent device, without involving any complicated processes, exhibits an external optical efficiency of ~ 3% under sunlight illumination (100 mW/cm2), which represents a 27% enhancement in efficiency over single layer LSCs based on CsPb(BrxI1-x)3 QDs and 117% over CsPb(ClxBr1-x)3 QDs. Our work shows that the addition of C-dots can dramatically enhance the long-term durability of LSC devices based on perovskite QDs due to their excellent photostability and simultaneous absorption of ultraviolet light.

Tandem luminescent solar concentrators based on engineered quantum dots

Luminescent solar concentrators (LSCs) can serve as large-area sunlight collectors for terrestrial and space-based photovoltaics. Due to their high emission efficiencies and readily tunable emission and absorption spectra, colloidal quantum dots have emerged as a new and promising type of LSC fluorophore. Spectral tunability of the quantum dots also facilitates the realization of stacked multilayered LSCs, where enhanced performance is obtained through spectral splitting of incident sunlight, as in multijunction photovoltaics. Here, we demonstrate a large-area (>230 cm2) tandem LSC based on two types of nearly reabsorption-free quantum dots spectrally tuned for optimal solar-spectrum splitting. This prototype device exhibits a high optical quantum efficiency of 6.4% for sunlight illumination and solar-to-electrical power conversion efficiency of 3.1%. The efficiency gains due to the tandem architecture over single-layer devices quickly increase with increasing LSC size and can reach more than 100% in structures with window sizes of more than 2,500 cm2. Multijunctions have long been used to enhance photovoltaic solar cell efficiency. Here, a large-area tandem luminescent solar concentrator is demonstrated using two types of quantum dot with low reabsorption.

Concurrent hydrogen and water production from brine water based on solar spectrum splitting: Process design and thermoeconomic analysis

This paper presents a novel process for high efficiency production of hydrogen and desalination of brine water based on the concept of solar spectrum splitting. The advantage of this system is concurrent production of hydrogen and distilled water using a sustainable process at large scale. The harvested energy from the separated solar spectral bands is used to supply the required energy for high temperature steam electrolysis and a double-stage flash distillation system. The integrated solar system is designed to reduce the energy conversion deficiencies, considerably. In order to investigate the performance of this system, a process simulation code is developed. An exergy analysis is conducted and the economic feasibility of the plant is evaluated. The sensitivity of the integrated cycle performance on solar insolation, electrolyzer temperature, and pressure is analyzed, and the results indicate that utilization of concentrator cells, with a multi-band gap mirror can increase the productivity of the cycle, drastically. It is observed that hydrogen and distilled water production rate can be increased by more than 1.6 times, when the harvested solar power increases from 28 MW to 55 MW. It is concluded that the maximum energy and exergy efficiencies of the integrated solar cycle is about 45%.

Amorphous solar cell on multilayer of SnO2/ZnO TCO substrate for full spectrum splitting solar cell application

To increase the performance of thin film solar cells, the solar spectrum splitting technique has been considered and studied. It was found from the simulation that the total efficiency of nearly 25% can be obtained at the splitting wavelength of 614 nm with the top cell using higher band gap material. The experiment has been carried out to verify the simulation results. Up to now a total efficiency of about 22.0% has been obtained using hydrogenated amorphous silicon (a-Si:H) and Cu(In1–x,Gax) as the top and bottom cells, respectively, at a splitting wavelength of 620 nm. In this study, we have developed a multilayer of transparent and conductive oxide (TCO) substrate of a-Si:H solar cell with better electrical properties especially improved fill factor and better electrical compatibility. This multilayer TCO is suitable for the splitting technique to enhance the performance at the short-wavelength of the top cell.

Development of thin-film solar cells using solar spectrum splitting technique

To increase the performance of thin-film solar cells, the solar spectrum splitting technique has been considered and studied. It was found from simulations that the total efficiency of nearly 25% can be obtained at the splitting wavelength of 600 nm with the top cell using higher band gap material. Experiments have been carried out to verify the simulation results. Up to now the total efficiency of about 22.0% has been obtained using a-Si:H and Cu(In1−x,Gax)Se2 as the top and bottom cells, respectively, at the splitting wavelength of 614 nm which is similar to the simulation results. This result shows that our developed splitting technique is promising for high-performance thin-film solar cells.

Concentrating PV/T Hybrid System for Simultaneous Electricity and Usable Heat Generation: A Review

Photovoltaic (PV) power generation is one of the attractive choices for efficient utilization of solar energy. Considering that the efficiency and cost of PV cells cannot be significantly improved in near future, a relatively cheap concentrator to replace part of the expensive solar cells could be used. The photovoltaic thermal hybrid system (PV/T), combining active cooling with thermal electricity and providing both electricity and usable heat, can enhance the total efficiency of the system with reduced cell area. The effect of nonuniform light distribution and the heat dissipation on the performance of concentrating PV/T was discussed. Total utilization of solar light by spectral beam splitting technology was also introduced. In the last part, we proposed an integrated compound parabolic collector (CPC) plate with low precision solar tracking, ensuring effective collection of solar light with a significantly lowered cost. With the combination of beam splitting of solar spectrum, use of film solar cell, and active liquid cooling, efficient and full spectrum conversion of solar light to electricity and heat, in a low cost way, might be realized. The paper may offer a general guide to those who are interested in the development of low cost concentrating PV/T hybrid system.

A two junction, four terminal photovoltaic device for enhanced light to electric power conversion using a low-cost dichroic mirror

A low-cost dichroic mirror can be used successfully for solar spectrum splitting to enhance solar to electrical energy conversion. The mirror is optimized for use with a polycrystalline silicon photovoltaic cell (pc-Si). With the dichroic mirror simultaneous excitation of a medium-efficient (11.1%) commercial pc-Si and a custom-made high band gap GaInP cell (12.3%), yields 16.8% efficiency, with both cells operating at maximum power. Our results clearly show that what is missing for this simple low-cost enhancement of Si solar cell efficiency are low-cost high band gap cells.