Concentrator Photovoltaic Research Articles

High-efficiency InAs/GaAs quantum dot intermediate band solar cell achieved through current constraint engineering

In this work, a novel device concept for improving the efficiency and field operation of conventional InAs/GaAs quantum dot (QD) based intermediate band solar cell (IBSC) with the feature of current constraint (CC-QD-IBSC) was proposed and evaluated from both theoretical simulations and experimental demonstrations. The advantages of the proposed device concept including increasing efficiency, obtaining higher suitability for operation under concentrated photovoltaic (CPV) condition and more robust efficiency stability against intermediate band fluctuation were rigorously identified using the detailed balance theorem by comparing with conventional InAs/GaAs QD-IBSC. Furthermore, a hybrid molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) shuttle growth of the proposed CC-QD-IBSC were adopted in this work for better preserving QD induced intermediate band feature and overcoming practical growth difficulties. By introducing a InGaP top cell for constraining the current of InAs/GaAs QD-IBSC, the short circuit current density of CC-QD-IBSC decreased to 13.0mA/cm2 under 1 sun illumination, a near 50 % reduction compared to the conventional InAs/GaAs QD-IBSC. On the contrary, by well adjusting the regrowth interface between MBE and MOCVD, we managed to reach the highest conversion efficiency of 22.8 % measured at an UL certified laboratory under light concentration ratio of 93 suns for the proposed CC-QD-IBSC with well-functioning QD and IB feature. It is our belief that our results pave the road for developing techniques geared towards higher efficiency and more practical field applications.

New hybrid concentrated photovoltaic/membrane distillation unit for simultaneous freshwater and electricity production

Traditional photovoltaic-thermal desalination systems often rely on electricity to power pumps which can reduce the amount of electricity available for other practices. The current work presents an integrated system combining a concentrator photovoltaic (CPV) with a direct contact membrane distillation (DCMD) in a single unit. Hence, it is possible to use the thermal energy generated by the CPV unit to power the DCMD unit and produce both fresh water and electricity simultaneously. A comprehensive numerical model of the proposed system is developed and validated to investigate the effects of different operating conditions on the system's performance, such as the solar concentration ratio (CR), feed Reynolds number, and feed channel aspect ratio (AR), on the system's productivity. Furthermore, a modified design is introduced in which the length of the DCMD is enlarged beyond the CPV to benefit from the excess energy within the feed water. The predicted produced flux reached ∼33.2 kg/m2 h at CR = 300, Re = 175, and AR = 2400. The modified method produced a higher flux than the original design within the same CR values. The optimum length ratio values were calculated, which were found to be 1.7, while the counter configuration was nearly 1.5.

Energy Consumption Monitoring System Based on IoT for Residential Rooftops

This work aims to create a web-based real-time monitoring system for electrical energy consumption inside a specific residence. This electrical energy is generated from a micro-CPV system lying on the roof of this residence. The micro-CPV is composed of a Fresnel lens as the main optical element, a spherical lens as the secondary optical element, and a multi-junction solar cell. A tiny photovoltaic concentrator system with a geometric concentration ratio of 100× is analyzed in the first part of this study, while the second part is designed to monitor the electricity generated by the micro-CPV system. An ESP8266 controller chipset is used to build the sensing peripheral node, which controls a relay and a PZEM-004T current sensor. As a result, the optical element used has approximately 83% optical efficiency, with an acceptance angle of 1.5°. Regarding the monitoring system, the architecture demonstrates the ability of the system to monitor current and energy consumption in real time using a computer or smartphone and a web server specially designed to continuously update the power consumption profile in a specific smart home environment. The whole electric power consumption monitoring system generally worked well. The monitoring system is configured to provide excellent accuracy for a 0.6% hit.

Life Cycle Assessment of the UK Space Energy Initiative Technology Roadmap

This paper aims to provide an overview of the environmental footprint of the UK Space Energy Initiative (SEI) technology roadmap based on the CASSIOPeiA solar power satellite (SPS) system using the life cycle assessment (LCA) methodology. The information covers the time period from 2022 to 2080 and is relevant for five stratospheric SPS prototypes, five low Earth orbit (LEO) SPS prototypes and twenty-five full-scale CASSIOPeiA systems which are capable of generating 2 gigawatts (GW) of power each and delivering this directly to the grid. Each CASSIOPeiA system has been modelled on the assumption that it will operate at 2.45 gigahertz (GHz) with 4-sun Concentrated Photo-Voltaic (CPV) variant in geostationary Earth orbit (GEO) for an average lifetime of thirty years. Primary data was collected from the SEI Technical Working Group and is considered to be representative of the current SEI technology roadmap. This information was collected using a simple Excel Spreadsheet titled ‘SEI LCA 1.0’. The file contains relevant information pertinent to the content of this paper but was considered too large to attach as an annex. Despite this, it should be noted that whilst the majority of the collected data was considered to be robust and of a sufficiently high data quality, the manufacturing & production of the rectenna was mainly based on well-judged estimations and data extrapolations. The results indicate that the manufacturing & production of the offshore rectennas is a particular hotspot, drawing similarities to the findings of Wilson et al. (2020). Keywords: Space Solar Power, Energy Systems, Life Cycle Assessment, Environmental Footprint, Ecodesign

Techno-economic and GHG mitigation assessment of concentrated solar thermal and PV systems for different climate zones

In this study, energy production by two solar energy technologies, namely concentrated solar power (CSP) and photovoltaic (PV) power, is compared from a technical, economic and environmental perspective. Initially, a 50 MW CSP plant is modeled and simulated at four selected sites in Pakistan. Then, the most feasible location of the CSP plant is compared with the solar PV plant of the same capacity. The effect of the solar thermal storage size and cooling system of the CSP system is investigated, while the photovoltaic tracking system is investigated to evaluate the technical and economic performance of the power plants. Technical performance is evaluated based on energy generation and capacity factors metrics, while economic performance is evaluated with respect to levelized cost, payback period and net present value. In addition, environmental criteria such as reducing greenhouse gas emissions (GHG), saving fossil fuels, and life-cycle water consumption are evaluated. From the results, it was concluded that the CSP plant located in Quetta is technically and economically viable. The capacity factor of the CSP plant is 36.6% compared to 19.8% for the PV plant, while the solar-to-electrical efficiency of the CSP plant is 14.2% compared to 20.8% for the PV plant. The required land area is 2.77 acres/GWh for the CSP plant and 2.33 acres/GWh for the PV plant, while the net capital cost of the CSP plant is five times higher than that of the PV plant. Various design parameters are optimized to obtain the minimum levelized cost of energy (LCOE) for both CSP and PV plants. The results of CSP and PV plants indicate that the LCOE can be reduced to 11.57 cents/kWh and 4.69 cents/kWh, respectively. Thus, the CSP plant performs better from the technical point of view while the PV plant performs better from the economic perspective.

Development and indoor characterization of a concentrator photovoltaic assembly for tracking-integrated systems

Tracking-integrated Concentrator Photovoltaics (CPV) represents an alternative to conventional CPV. The elimination of expensive and heavy solar trackers contributes to reduce the cost of conventional CPV, and open new market segments. This technology, still under development, needs further investigation. In this work, two tracking-integrated focusing systems with two different concentration levels, consisting of a fixed bi-convex aspheric lens and a movable triple-junction solar cell, are analysed. Initially, by means of detailed optical modelling, the concentrator elements are optimized. After that, they are experimentally investigated at Concentration Standard Test Conditions (CSTC) by varying the angle of incidence ± 50°. The results show an optical efficiency > 80% and > 60% for a geometric concentration of 10.0x and 82.5x, respectively, within the whole angular range. These systems could contribute to novel CPV applications such as agrivoltaics or building integrated.

Improvements of PV receiver in laser wireless power transmission by non-imaging optics

Laser Wireless Power Transmission (LWPT) systems have an extensive prospect in the field of wireless energy transmissions such as the space control on-orbit, spacecraft sensor networks, satellites to satellite communication and power transmission, ground to ground, ground to air, ground to Unmanned Aerial Vehicle (UAV), etc. Previously, Concentrated Photovoltaics(CPV) has been used in solar energy as a solution to lower the size of the photovoltaics and yet increase efficiency. As is known laser beam spot normally presents a Gaussian distribution and laser somehow must match the size of the PV cell or array, that is how lens and concentrators are important to reshape and guide the laser beam towards the photovoltaics and in case of misalignment. The current research aims at improve the output performance of LWPT receiver by typical non-imaging optical device-Cross Compound Parabolic Concentrator (CCPC), which helps to improve the transmission of laser beam from different incident directions. Multi-field characteristics of the CPV module under laser power would be solved based on parameters from non-linear regression and experimental study. The multi-field performances of CPV module and single solar cell as the LWPT receivers have been compared. We have found that transmission distance d, divergence half-angle β, rotation angle θ and misalignment distance dmis are most important parameters for multi-field performances and LWPT conversion. The current research provides important references for LWPT system design and optimizations.

Temperature-Dependent Reversal of Phase Segregation in Mixed-Halide Perovskites.

Understanding the mechanism of light-induced halide segregation in mixed-halide perovskites is essential for their application in multijunction solar cells. Here, photoluminescence spectroscopy is used to uncover how both increases in temperature and light intensity can counteract the halide segregation process. It is observed that, with increasing temperature, halide segregation in CH3 NH3 Pb(Br0.4 I0.6 )3 first accelerates toward ≈290K, before slowing down again toward higher temperatures. Such reversal is attributed to the trade-off between the temperature activation of segregation, for example through enhanced ionic migration, and its inhibition by entropic factors. High light intensities meanwhile can also reverse halide segregation; however, this is found to be only a transient process that abates on the time scale of minutes. Overall, these observations pave the way for a more complete model of halide segregation and aid the development of highly efficient and stable perovskite multijunction and concentratorphotovoltaics.

Cooling of Concentrated Photovoltaic Cells—A Review and the Perspective of Pulsating Flow Cooling

This article presents a review to provide up-to-date research findings on concentrated photovoltaic (CPV) cooling, explore the key challenges and opportunities, and discuss the limitations. In addition, it provides a vision of a possible future trend and a glimpse of a promising novel approach to CPV cooling based on pulsating flow, in contrast to existing cooling methods. Non-concentrated photovoltaics (PV) have modest efficiency of up to around 20% because they utilise only a narrow spectrum of solar irradiation for electricity conversion. Therefore, recent advances employed multi-junction PV or CPV to widen the irradiation spectrum for conversion. CPV systems concentrate solar irradiation on the cell’s surface, producing high solar flux and temperature. The efficient cooling of CPV cells is critical to avoid thermal degradation and ensure optimal performance. Studies have shown that pulsating flow can enhance heat transfer in various engineering applications. The advantage of pulsating flow over steady flow is that it can create additional turbulence and mixing in the fluid, resulting in a higher heat transfer coefficient. Simulation results with experimental validation demonstrate the enhancement of this new cooling approach for future CPV systems. The use of pulsating flow in CPV cooling has shown promising results in improving heat transfer and reducing temperature gradients.

An artificial neural network-based performance model of triple-junction InGaP/InGaAs/Ge cells for the production estimation of concentrated photovoltaic systems

Analytical and empirical models analyze complex and non-linear interactions between the input–output parameters of the system. This is very important in the case of photovoltaic systems to understand their real performance potential. On the other hand, manufacturers of photovoltaic panels rate the maximum performance of the system under fixed lab conditions as per standard testing conditions (STCs) or nominal operating cell temperature (NOCT) standards of IEC. These ratings do not provide the actual production potential of the system in a field with fluctuating conditions of irradiance and temperature. For the case of a concentrated photovoltaic (CPV) system, utilizing multi-junction solar cells (MJCs), there is no commercial tool available to analyze the performance and production, despite some recent empirical models that also require post-processing of experimental data to be used in conventional models. In this study, an artificial neural network (ANN)-based performance model is presented for a multi-junction solar cell, which is not only convenient to apply but can also be easily expanded to predict the real-field performance of the CPV system of any designed size. In addition, the ANN-based model showed a high accuracy of 99.9% in predicting the performance output of MJCs as compared to diode-based empirical models available in the literature. The irradiance concentration at the cell area and the cell temperature are taken as inputs for the neural network. If both of these parameters are known, then the cell efficiency as an output can accurately predict the CPV performance for a field operation.

Translation of outdoor tandem PV module I–V measurements to a STC power rating

AbstractThe procedures for the power rating of tandem‐cell‐based concentrator photovoltaic (CPV) modules defined in the international standard IEC 62670‐3 are adapted to the requirements of tandem‐cell‐based flat plate PV modules. The adjusted procedure describes how to translate outdoor measured PV current–voltage characteristics to standard test conditions (STC): 1000 W/m, 25°C cell temperature, AM1.5g spectral conditions. In this work, we describe how to obtain all required input parameters: thermal transient measurements to determine the module temperature coefficients, categorizing and filtering the prevailing spectral irradiance conditions using spectral matching ratios, and determining the 25°C module open‐circuit voltage from dark current–voltage curves. Three specimen PV modules (triple‐junction, III‐V on Silicon and III‐V on Germanium) have been measured for several months outdoors on a dual axis tracking unit at Fraunhofer ISE in Freiburg. In this work, we demonstrate that the CPV module power rating procedures in IEC 62670‐3 are also—in a modified form—to be recommended for the outdoor rating of tandem‐cell‐based flat plate PV modules.

Technological advancements and research prospects of innovative concentrating agrivoltaics

Agrivoltaic is a strategic and innovative approach that combines photovoltaic (PV) energy conversion with agricultural production, enabling synergies in the production of food, energy, and water, as well as the preservation of the ecological landscape. Shading management, intensity adjustment, and spectral distribution allow innovative PV systems to generate significant amounts of electricity without affecting agricultural production. Demonstration projects have already been developed around the world and there is a wealth of experience with various design solutions for commercial use. One of these new technologies is concentrator photovoltaics (CPV). The CPV has excellent spectral processing capabilities and highly concentrated power generation efficiency, which makes it a perfect solution for integrating with photosynthesis. This study aims to present the working principle of CPV modules considering agricultural applications and discuss the recent advancements in concentrating agrivoltaics. In this method, the problem of shading is mitigated by two main strategies: (i) parabolic glasses covered with a multilayer dichroic polymer film that reflects near-infrared (NIR) radiation onto the solar cells installed at the focal area and transmits photons in the range of photosynthetically active radiation (PAR), and (ii) highly transparent sun-tracking louvers or Fresnel lenses that concentrate direct sunlight onto the solar cells to generate electricity. In the latter solution, the remaining diffuse sunlight is directed to the ground for use by growing plants. Although the CPV development trend has been slow due to the lower cost of crystalline silicon, the development of CPV for agriculture with accurate spectral separation could revitalize this industry. In this regard, more research and development are needed to evaluate the suitability of materials that split solar radiation and their impacts on the electrical performance of CPV modules, taking into account the physiology of plants.

Certified high-efficiency “large-area” perovskite solar module for Fresnel lens-based concentrated photovoltaics

The future of energy generation is well in tune with the critical needs of the global economy, leading to more green innovations and emissions-abatement technologies. Introducing concentrated photovoltaics (CPVs) is one of the most promising technologies owing to its high photo-conversion efficiency. Although most researchers use silicon and cadmium telluride for CPV, we investigate the potential in nascent technologies, such as perovskite solar cell (PSC). This work constitutes a preliminary investigation into a "large-area" PSC module under a Fresnel lens (FL) with a "refractive optical concentrator-silicon-on-glass" base to minimize the PV performance and scalability trade-off concerning the PSCs. The FL-PSC system measured the solar current-voltage characteristics in variable lens-to-cell distances and illuminations. The PSC module temperature was systematically studied using the COMSOL transient heat transfer mechanism. The FL-based technique for "large-area" PSC architectures is a promising technology that further facilitates the potential for commercialization.

Performance of a Heat-Pipe Cooled Concentrated Photovoltaic/Thermoelectric Hybrid System

Compared to traditional one-sun solar cells, multijunction concentrator cells operating under concentrated solar radiation are advantageous because of their high output and low cooling costs. Such a concentrator PV requires a cooling technique to maintain its performance and efficiency. The performance of a multi-junction concentrator photovoltaic cell of efficiency around 33%, operating under concentrated solar radiation (160–250 sun), has been tested. Heat pipes were used in this study as a fast and efficient way of rejecting heat accumulated in the cells. In this work, the evaporator side of the heat pipe was set in thermal contact with the back side of the solar cell such that the excess heat was transferred efficiently to the other side (condenser side). To positively utilize such excessive heat, two thermoelectric generators were thermally attached to either side of the condenser of the heat pipe, and each was attached to a fin-shaped heat sink. Four different cooling configurations were tested and compared. The net power obtained by this concentrator solar cell employing two types of TEG with different lengths as a cooling alongside two thermoelectric generators for heat-to-electricity conversion was 20% and 17%, corresponding to the long and short heat pipe configurations, respectively, compared to traditional a heat sink only configured at an optical concentration of 230 suns.

Nonimaging High Concentrating Photovoltaic System Using Trough

Solar energy is a long-established technology, which has zero CO2 emissions, and provides low-cost energy for a given area of land. The concentrator photovoltaic (CPV) has been given preference over the photovoltaic due to its high efficiency. In a CPV system, most of the solar cell area has been replaced with an optical concentrator. Various parabolic trough based CPV systems have been presented where a concentration of <300 is achieved. In the current research, a design is presented to achieve a high concentration of 622×. The design consists of two stages of concentration including parabolic trough as a main concentrator and nonimaging reflective grooves as a secondary concentrator. The trough reflects the incident light towards the secondary reflector where the light is redirected over the solar cell. Design of the two-stage concentrator, ray-tracing simulation, and results are presented. The system achieved an optical efficiency of 79%. The system would also be highly acceptable in solar thermal applications owing to its high concentration.

Liquid spherical lens as an effective auxiliary optical unit for CPV/T system with remarkable hydrogen production efficiency

How to efficiently convert solar radiation into energy sources for easy storage and consumption is an urgent issue. Although concentrated photovoltaics can achieve high efficiency, it places higher demands on the optical system and heat management. Herein, a new design is presented where a liquid spherical lens acts as a secondary optical element of the concentrating solar system, refracting the light beam while participating in spectral beam splitting. The radiation energy unavailable for solar cells is harvested by the liquid spherical lens through spectral beam splitting which serves to raise the temperature of the electrolyte. Compared with the conventional concentrated photovoltaic coupled electrolytic hydrogen production system, the addition of a liquid spherical lens improves the solar cell heat dissipation while increasing the operating temperature of the electrolyzer, achieving higher solar-to-hydrogen efficiency. The system with this design obtains a solar-to-electricity efficiency of 31.7% as verified by indoor experiments. The solar-to-hydrogen efficiency of the system achieved an average value of 22.1% and a benchmark maximum value of 22.7% during 7 h of continuous operation. The solar-to-hydrogen efficiency is improved by at least 10% compared to the design that separates the secondary optics from the spectral beam-splitting filter. Compared with existing systems employing commercial CPV modules, the efficiency is improved by at least 6% benefiting from the rational distribution of the spectrum by the liquid spherical lens.

Performance analysis of concentrated photovoltaic systems using thermoelectric module with phase change material

A photovoltaic (PV) module integrated with a cooling system can generate higher electrical energy in comparison to a conventional PV module that is without a cooling system. Phase change materials (PCMs) and/or thermoelectric generators (TEGs) are some of the several passive cooling methods used in enhancing the energy output of PVs. Herein, a comprehensive numerical study of highly concentrated standalone photovoltaic (CPV), CPV-PCM, CPV-TE, CPV-PCM-TE, and CPV-TE-PCM systems is conducted in COMSOL Multiphysics environment. In addition to analysing the energy output of the systems, the study explores the effect of using different PCMs as well as PCM containers with different internal configurations on the energy output of the systems. The results revealed that the energy conversion efficiencies of the CPV-PCM, CPV-TE, CPV-PCM-TE, and CPV-TE-PCM are respectively 34.8 %, 97.3 %, 106.5 %, and 111.4 % higher than that of the standalone CPV system. These results also indicated that the CPV-TE-PCM configuration is superior to the other configurations, this is due to the creation of a large temperature gradient which enhances the performance of the TEG. Moreover, it was determined that the ideal melting temperature of a PCM should be a few degrees above the ambient temperature; in this study, RT28HC PCM is found to be the most suitable PCM for cooling the systems. Finally, it was revealed that changing the fin configurations inside a PCM container has an insignificant influence on the energy efficiencies of highly concentrated PV models.

Determination of individual I(V) characteristics of each sub-cell of a triple junction device

Very high conversion efficiency is reached with triple junction solar devices integrated in concentrator photovoltaic (CPV) modules. However, reduction of the active area for micro-CPV applications increases the perimeter/area ratio, enhancing losses linked to the edges. It is therefore important to characterize the perimeter influence on the final conversion efficiency. For this purpose, I(V) characterization under dark and/or light could be used as a test of the sidewalls influence. We have designed an experiment to perform I(V) curves using the light of three lasers with adjustable powers at 405, 785, and 980 nm, preferentially absorbed by the top, middle or bottom junction of the device, respectively. This experiment was applied to commercial devices made from a stack of GaInP/GaAs/Ge. In parallel we have developed a numerical calculation modeling the device to reproduce the behaviors observed during I(V) experiments. Junction parameters and influence of leakage resistances are deduced from the fit of experimental results with the numerical calculation. The I(V) experiment as well as the numerical calculation are presented in details. It is also underlined that, combining both experiment and calculation, the I(V) characteristic of each junction as if it was isolated can be determined.

English

Studies on concentrated light influence do not take into account the effect of the heating and this proves to be harmful on photovoltaic parameters. The main purpose of this work is to study the effects of light concentration and the heating caused by this concentration on intrinsic properties and carrier density profile. A thermal model of the PV cell is proposed. By applying the power balance at the steady-state, the PV cell thermal equation is determined. The resolution of this equation leads to temperature profile which shows a rapid increase with light concentration. The mobility  and diffusion  coefficients of electrons increase to reach their maxima, respectively  at C=6,77 Suns where temperature is T=430,92 K and  at C= 12,59 Suns where temperature is T=508,24; before decreasing. However, for the holes these parameters decrease slowly with concentration increase. Silicon gap energy decreases while electrons intrinsic density increases with increasing concentration. The variations of these parameters are explained on one hand by their dependence on temperature but also by temperature profile with concentration. An electrical model of the PV cell under variable concentration is also proposed and from which the carrier’s density is determined. It emerges that the carrier density increases significantly with concentration ratio. This fact is explained by the photo-generation increase with concentration. And also, by thermal generation increase linked to temperature increases with concentration increase. Results also show that carriers density is greater in the rear side compared to the zone near the junction in opposite to authors who did not take into account temperature effect and who showed that carriers density is greater at the illuminated face. Key words: Temperature profile, concentrated light PV cell, intrinsic density, gap energy, carriers density profile.

A Graphene Quantum Dot Film with a Nanoengineered Crack-Like Surface via Bubble-Induced Self-Assembly for High-Power Thermal Energy Management Applications

Films with micro/nanostructures that show high wicking performance are promising in water desalination, atmospheric water harvesting, and thermal energy management systems. Here, we use a facile bubble-induced self-assembly method to directly generate films with a nanoengineered crack-like surface on the substrate during bubble growth when self-dispersible graphene quantum dot (GQD) nanofluid is used as the working medium. The crack-like micro/nanostructure, which is generated due to the thermal stress, enables the GQD film to not only have superior capillary wicking performance but also provide many additional nucleation sites. The film demonstrates enhanced phase change-based heat transfer performance, with a simultaneous enhancement of the critical heat flux and heat transfer coefficient up to 169% and 135% over a smooth substrate, respectively. Additionally, the GQD film with high stability enables a performance improvement in the concentration ratio and electrical efficiency of concentrated photovoltaics in an analytical study, which is promising for high-power thermal energy management applications.