Photovoltaic-thermoelectric Hybrid Research Articles

Structural optimization of thermoelectric modules in a concentration photovoltaic–thermoelectric hybrid system

Concentration photovoltaic (CPV) cells can only partially convert solar energy into electricity. The remaining energy is converted into thermal energy. This not only causes the temperature of the photovoltaic cell to rise, but also reduces the generation efficiency of the cell. The excess CPV heat can be recovered using a thermoelectric generator (TEG). The design of the structure of the TEG is important for a CPV-TEG hybrid system because it affects the heat dissipation of the CPV and thus its efficiency. In this study, a mathematical model of a hybrid system was established. The focus was to examine the effect of the structural parameters of the TEG on the system efficiency. The results showed that an optimal structural parameter (the ratio of the cross-sectional ratio to the height) with the value of 0.36 mm−1 existed for the TEG, enabling the system efficiency to reach a maximum of 41.73% under simulated conditions. In addition, the relationship between the optimal structural parameter, CPV temperature coefficient, concentration ratio, and cooling heat transfer coefficient was analyzed. The results can provide guidance for the efficient design of a hybrid system.

Design and Implementation of Hybrid Photovoltaic-thermoelectric System with Intelligent Power Supply Management

A photovoltaic thermoelectric hybrid (PV-TEH) system with intelligent power supply management is proposed in this paper. Combining the advantages of the thermoelectric generator (TEG) and the thermoelectric cooler (TEC), the TE intelligent switching circuit and the water speed regulation circuit are presented in this system. Due to the energy harvesting of the TE devices, the high conversion efficiency can be realized in the PV-TEG mode. The experimental results show that the output power of the PV cell in our work is increased by 14.4% on average compared with that in a PV system without TE. Since the proposed system overcomes the disadvantage of power consumption for TEC throughout the whole process, the electrical energy generated by the TEG is effectively harvested, achieving 57.9% improvement of the overall energy conversion efficiency over the PV-TEC system. This intelligent energy harvesting and thermal management by employing TE as generator and cooller with the multiplexed technique can provide a reference for self-power electronic equipment.

Photovoltaic-thermoelectric (PV-TE) hybrid system for thermal energy harvesting in low-power sensors

Nowadays, population growth and increasing urbanization imply a growing demand for energy, which must be achieved while limiting polluting emissions. To meet this dual challenge, the use of renewable energy resources and energy generators is essential. Thermoelectric generators (TEGs) have demonstrated their ability to directly transform thermal energy into electrical energy through the Seebeck effect. Due to their unique advantages, thermoelectric systems have emerged in the last decade as a promising alternative among other green energy generation technologies. In this regard, the study focuses on a design of a Photovoltaic-Thermo-Electric (PV-TE) Hybrid System for thermal energy harvesting in low power collectors. The power harvested by TEG increases with the temperature and an interesting value close to 7mW is achieved with a maximum temperature of 52 °C of the hot face the thermoelectric system.

Device performance matching and optimization of photovoltaic-thermoelectric hybrid system

• The effects of various factors on the device selection of the hybrid system are studied. • A device selection method of the hybrid system with broad suitability is established. • A multi-objective genetic algorithm is adopted to optimize the coupling efficiency and efficiency difference. • The two optimization objectives are proved to be negatively correlated. This paper focuses on the two critical issues of device selection and performance optimization for the photovoltaic-thermoelectric hybrid system. Theoretical models of concentrating photovoltaic-thermoelectric hybrid system and concentrating photovoltaic system are established. The impacts of varying factors on system device selection are investigated. The device performance matching mechanism of the coupling system is revealed, and a device selection method of broad suitability is proposed. The optimization of the hybrid system is conducted by adopting a multi-objective genetic algorithm with the highest coupling efficiency and the maximum efficiency difference relative to a single photovoltaic system as the optimization objectives. The results show that the minimum thermoelectric figure of merit of the hybrid system is determined only by the concentration ratio and the photovoltaic device capability when the cooling condition is fine, the thermal contact resistance is low, and the thermoelectric structure is appropriate. The proposed device selection method on the basis of these results can be well employed to select coupling devices and evaluate the system feasibility. The multi-objective optimization results reveal that the two optimization objectives are negatively correlated. Further consideration of the system economy is required to determine the compromise between the highest coupling efficiency and the maximum efficiency difference for the optimum design of the coupling system.

A wearable organic photovoltaic-thermoelectric (OPV-TE) hybrid generator to minimize the open-circuit voltage losses of OPV module

This work presents a hybrid generator, composed of an organic photovoltaic (OPV) module and a thermoelectric generator (TEG), to improve power generation performance mainly by minimizing the open-circuit voltage (VOC) losses of OPV modules. Thanks to the TEG, which utilizes heat energy, the proposed device can be used to harvest electrical energy even after the sun goes down. After hybridization, the external quantum efficiency and photon absorption of the OPV module increased remarkably, especially in the long wavelength region. The VOC of the hybrid generator increased more than the arithmetic sum of the VOCs of the TEG and OPV module, thanks to the reduction in nonradiative recombination. The hybrid generator also had a longer charge recombination lifetime, despite the much larger number of excess charge carriers compared to the OPV module alone. This allows the hybrid generator to have a higher short-circuit current than the OPV module alone has. As a result, the hybrid generator can harvest up to 46.3% more electrical energy than an OPV module alone throughout the day. Wearing the wearable hybrid generator on the forearm for 30 min outdoors could harvest up to 34 mWh during the day, and up to 5.9 mWh at night.

Parabolic trough photovoltaic thermoelectric hybrid system: Thermal modeling, case studies and economic and environmental analyses

In this work, a hybrid solar system, which consists of parabolic trough collector equipped with photovoltaic (PV) module and thermoelectric generators (TEGs), is studied. The aim of this work is to develop a new thermal modeling for parabolic trough photovoltaic thermoelectric (PTPVT-TE) system using thermal resistance analogy. The thermal modeling is simulated using MATLAB software, compared and validated against previous works from the literature. Case studies have been conducted on three countries of different climates: Lebanon (moderate), France (mild) and UAE (warm) to investigate the system performance. It is observed that the total annual energy generated by PV module and TEGs are 44.7 MW h and 1.8 MWh in Lebanon, 26.5 MW h and 0.8 MW h in France, 49.2 MW h and 1.9 MW h in UAE respectively. Also, the results reveal that the integration of TEGs to the PTPVT system leads to increase the average annual generated total electrical power by the system by about 1.8% and decrease the average annual heat rate delivered to the fluid by 1.9%. Furthermore, it was obtained that the PV layer increases the average total efficiency of the system by approximately 44.4%. Besides, economic and environmental analyses have been performed to expose the significant importance of this system. It is shown that the payback period of the system is 2.1 years, 2.4 years and 2.5 years and the annual amount of mitigated CO2 emissions is 81.4 tons, 5.7 tons and 79.5 tons for Lebanon, France and UAE respectively.

Improving the Energy-Conversion Efficiency of a PV–TE System With an Intelligent Power-Track Switching Technique and Efficient Thermal-Management Scheme

A photovoltaic-thermoelectric (PV-TE) hybrid system can be used for efficient thermal energy utilization from the generated waste heat in PV devices. In this article, an efficient PV-TE hybrid system with intelligent power-track switching technique and thermal management based on energy conversion is proposed. To make the output power of PV-TE system stable and normalized, an incorporated stable voltage circuit is designed based on energy conversion. In addition, a control-and-monitoring strategy is launched in the system to realize the normal collecting for the output power of PV-TE system. Finally, a battery protection circuit is performed to ensure that the energy converted by the entire system is effectively stored. The experimental results show that more electrical energy about 84 034 J was obtained with our energy harvesting system than that of a single photovoltaic (PV) cell. Besides, the thermal gradient of PV cells is indirectly reduced the operation of the whole system, which is automatically monitored due to the proposed intelligent power-track switching technique.

Multi-objective optimization of concentrated Photovoltaic-Thermoelectric hybrid system via non-dominated sorting genetic algorithm (NSGA II)

Thermoelectric generators harvest additional electrical power when used in combination with concentrated photovoltaic cells given rise to a hybrid system. Overall cost of the system is high; therefore, the parameters of the system need to be optimized to obtain high output performance. This study determines the output performances of four sets of equations (models) used in the hybrid system, using the performance of recently developed nanostructured thermoelectric materials. Seven parameters of the system were optimized through these models using non-dominated genetic algorithm. Models 1 and 2 have the highest performance chosen by TOPSIS decision-making method. The power output and conversion efficiencies of the hybrid system in models 1 and 2 are 426.5 W, 11.45% and 461.12 W, 10.77%, respectively. Likewise, the highest TOPSIS solution for power output of one TEG module operating in the hybrid system and its corresponding efficiency is obtained in model 4 and are 1.97 W and 0.078%, respectively. This validates the fact that TEG operating in a hybrid system has optimum performance at a point when the load resistance is less than its internal resistance.

Correction: Comparing different geometries for photovoltaic-thermoelectric hybrid devices based on organics

Correction for ‘Comparing different geometries for photovoltaic-thermoelectric hybrid devices based on organics’ by José P. Jurado et al., J. Mater. Chem. C, 2021, 9, 2123–2132, DOI: 10.1039/D0TC05067A.

Comparing different geometries for photovoltaic-thermoelectric hybrid devices based on organics

The preferred geometry for hybrid organic photovoltaic-thermoelectric hybrid devices is a transmission, contact geometry. Besides the extra energy afforded by the thermoelectric, for organics, the photovoltaic efficiency improves when hot (cf. inorganics).

Feasibility analysis of a tandem photovoltaic-thermoelectric hybrid system under solar concentration

Abstract This paper aims to provide a comprehensive feasibility analysis of the tandem concentration photovoltaic-thermoelectric (CPV-TE) hybrid system to guide practical hybrid system design. Theoretical models and experimental equipment of the concentration photovoltaic (CPV) system and the CPV-TE hybrid system are both established. The working temperature and output power of the two systems at different solar concentration ratios are first measured and compared. Then, the effects of different device performance and system operating parameters, including PV reference efficiency, PV temperature coefficient, TE figure of merit, concentration ratio, thermal contact resistance, cooling performance, coolant temperature, and TE thermal resistance, on the feasibility of coupling utilization are theoretically investigated. Finally, some design principles of the tandem hybrid system are provided based on the research results. The experimental results demonstrate the superiority of hybrid utilization when using a single-junction gallium arsenide PV cell, and a maximum output power improvement of 8.7% (from 1.38W to 1.5W) can be achieved when the concentration ratio is 255. The theoretical results illustrate that device performance parameters are the main factors that determine the feasibility of hybrid utilization. Choosing appropriate system operating parameters is also important to ensure the superiority of the hybrid system.

Unsteady-state performance comparison of tandem photovoltaic-thermoelectric hybrid system and conventional photovoltaic system

This paper provides a comprehensive unsteady-state performance comparison between the tandem photovoltaic-thermoelectric (PV-TE) hybrid system and the conventional photovoltaic (PV) system. The three-dimensional unsteady-state models of the two systems are established. The effects of weather and season conditions on the superiority of coupling utilization are studied. The annual performance difference between the two systems is analyzed, and the optimal external working conditions of coupling utilization is revealed. The results demonstrate that compared with the conventional PV system, the tandem PV-TE coupling system can achieve higher electrical efficiency in any weather or season. The tandem hybrid system achieves the highest average efficiency of 27.43% in February, while that of the conventional PV system is only 26.46% in December. However, the efficiency enhancement of hybrid utilization is at the expense of reducing the system security and stability. The photovoltaic cell in the tandem hybrid system works at a higher temperature, and the change in direct solar irradiance has a more significant impact on hybrid system temperature and efficiency. When working in the cloudy day, the stability of the hybrid system will be diminished, and the superiority of hybrid utilization will be weakened. Moreover, the tandem hybrid system is proved to be more suitable for use in areas or times with high direct solar irradiance and low ambient temperature. The results can be employed to guide the application and design of the practical PV-TE hybrid system.

A Self-powered Wearable Wireless Sensor System Powered by a Hybrid Energy Harvester for Healthcare Applications

In this paper, a wearable medical sensor system is designed for long-term healthcare applications. This system is used for monitoring temperature, heartbeat, blood oxygen saturation (SpO2), and the acceleration of a human body in real-time. This system consists of a temperature sensor, a pulse oximeter sensor, an accelerometer sensor, a microcontroller unit, and a Bluetooth low energy module. Batteries are needed for supplying energy to this sensor system, but batteries have a limited lifetime. Therefore, a photovoltaic–thermoelectric hybrid energy harvester is developed to power a wearable medical sensor system. This harvester provides sufficient energy and increases the lifetime of the sensor system. The proposed hybrid energy harvester is composed of a flexible photovoltaic panel, a thermoelectric generator module, a DC–DC boost converter, and two super-capacitors. Experimentally, in active-sleep mode, the sensor system consumes an average power of 2.13 mW over 1 h and works without the energy harvester for 46 h. Finally, the experimental results illustrate the sustainable and long-term monitoring operation for the medical sensor system.

Experimental investigation of novel integrated photovoltaic-thermoelectric hybrid devices with enhanced performance

A combined photovoltaic (PV) cell and thermoelectric (TE) device can effectively expand the utilization of the solar spectrum, and it has been confirmed that effective heat transfer can improve the performance of PV-TE hybrid devices. In this study, a series of novel integrated PV-TE hybrid devices with enhanced heat transfer capabilities have been manufactured by removing the upper ceramic plate of conventional TE devices. An insulating layer was deposited on the back of the PV cell to avoid an electrical connection between the PV cell and the TE device. An exhaustive experimental study has been conducted on the integrated PV-TE hybrid device, using a system that includes a solar simulator and cooling equipment. Experimental results indicate that the integrated hybrid design can improve the electrical output of the PV cell. In addition, thermal greases with different thermal conductivities are used to decrease the thermal resistance between the PV cell and TE device. The use of the thermal lubricant significantly improves the performance of the integrated PV-TE hybrid device by enhancing the heat dissipation of the PV cell, and the heat absorption of the hot side of TE device. The thickness of the insulating layer may be controlled with the use of different application times, and this has been demonstrated. Experimental results show that a thinner insulating layer can increase heat transfer significantly and improve the performance of the integrated PV-TE hybrid device. Consequently, the design utilizes a more compatible and efficient integrated couple involving a PV cell and TE device.

Performance evaluation and lifetime prediction of a segmented photovoltaic-thermoelectric hybrid system

Combining the photovoltaic (PV) and thermoelectric (TE) technologies to form a hybrid PV-TE system is considered as a promising way to utilize the unwanted heat accumulated in the solar cell. This paper comprehensively analyzes and optimizes the performance and fatigue failure of a concentrated PV-TE system with the segmented TE model. The results demonstrate that the power output and efficiency of the hybrid PV-TE systems with segmented TE model can be greatly enhanced compared to those of the hybrid PV-TE systems with the uniform TE model. For the solar cell with bigger efficiency correction coefficient, a larger combined heat loss results in a higher power output and efficiency. Conversely, the power output and efficiency decrease with the combined heat loss. The optimized height of TE model corresponding to the highest performance decreases with the height ratio of the upper to lower TE leg. The length of the TE leg has little influence on the optimized height of the TE module. The combined heat loss by radiation and convection can improve the fatigue life of the hybrid system. A balance between the enhancement of fatigue life and decrease in the total efficiency can be obtained by adjusting the solar concentration ratio of the solar cell for different wind velocities.

Defining indispensability of storage for raised renewable penetration in conventional and thermoelectric coupled microgrid: Modeling, analysis and validation

The inflation of clean, efficient, sustainable, effective, secure, and reliable electricity demand have been triggered much interest for Microgrid (MG) at a miraculous and quickened pace. The necessity of reliability enhancement, diversity of fuel, cutback of greenhouse gases, severe weather fluctuation etc. has stimulated the inclusion of MG concept not only in utility level but also in customer and community level. Incorporation of solar photovoltaic (SPV) and thermoelectric (TE), termed as Solar photovoltaic-thermoelectric (SPV-TE) hybrid system is found be a very promising technique to broadening the utilization of solar spectrum and enhancing the power output effectively-cum-efficiently. This hybrid architecture caters electrical energy with additional thermal energy that signifies upon harnessing of solar insolation in an exceptional way. But in order to retain the voltage profile in the permissible level, MG needs storage mechanism for smoothening of renewable based power inconstancy, catering high active power significantly and dodging the long term reactive power rising. This paper illustrates the comparative analysis of three systems such as Conventional MG;TE coupled Conventional MG, and only TE coupled solar PV based MG defining the necessity of employment of energy storage system (ESS). The superiority of third system has been outlined in terms of lesser complexity in source integration, mitigating the detriment of Wind energy system (WES) and Fuel Cell Systems (FCT) integration in real life application, delivery of higher active power, and lesser reactive power absorbance over the two other systems. The studied system is modeled in MATLAB/Simulink environment and the results are presented to support, verify, and validate the analysis.

Optimization and performance analysis of a solar concentrated photovoltaic-thermoelectric (CPV-TE) hybrid system

This work presents, for the first time, a statistical model to forecast the electrical efficiency of concentrated photovoltaic-thermoelectric system (CPV-TE). The main objective of this work is to analyze the impact of the input factors (product of solar radiation and optical concentration, external load resistance, leg height of TE and ambient temperature) most affecting the electrical efficiency of CPV-TE system. An innovative and integrated approach based on a multi-physics numerical model coupling radiative, conductive and convective heat transfers Seebeck and photoelectrical conversion physical phenomena inside the CPV-TE collector and a response surface methodology (RSM) model was developed. COMSOL 5.4 Multiphysics software is used to perform the three-dimensional numerical study based on finite element method. Furthermore, results from the numerical model is then analysed using the statistical tool, response surface methodology. The analysis of variance (ANOVA) is conducted to develop the quadratic regression model and examine the statistical significance of each input factor. The results reveal that the obtained determination coefficient (R2) for electrical efficiency is 0.9945. An excellent fitting is achieved between forecast values obtained from the statistical model and the numerical data provided by the three-dimensional numerical model. The influence of the parameters in order of importance on the electrical efficiency are respectively: product of solar radiation and optical concentration, the height legs of TE, external electrical resistance load, and ambient temperature. A simple polynomial statistical model is created in this work to predict and maximize the electrical efficiency from the solar CPV-TE system based on the four investigated input parameters. The maximum electrical efficiency of the proposed CPVTE (17.448%) is obtained for optimum operating parameters at 229.698 W/m2 value of product of solar radiation and optical concentration, 303.353 K value of ambient temperature, 2.681Ω value of resistance electrical load and at 3.083 mm value of height of TE module.

Solar energy harvesting potential of a photovoltaic-thermoelectric cooling and power generation system: Bidirectional modeling and performance optimization

In the present work, a comprehensive thermodynamic and exergoeconomic comparison between concentrated photovoltaic-thermoelectric cooling (CPV-TEC) and concentrated photovoltaic-thermoelectric generation (CPV-TEG) systems was introduced and explored, aiming to actively investigate the energy harvesting potential of the photoelectric-thermoelectric cooling and power generation processes. Transitional characteristics of thermoelectric conversion in concentrated photovoltaic-thermoelectric hybrid (CPV-TEH) system have been outlined through multiple evaluation indicators, including output electricity, cell temperature, thermodynamic efficiency, exergy destruction and unit exergy cost under various decision parameters. Furthermore, operating mode and conversion conditions of thermoelectric device in CPV-TEH system have been sensitively identified to obtain the dual action mechanism of cooling and power generation sequentially. Theoretical models have been compared and validated well with former published results. Results indicate that the operating mode of thermoelectric device could be fully converted from TEG to TEC when the operating current is around 0.27 A; the minimum unit exergy costs are respectively found to be 0.263 $/kwh, 0.148 $/kwh and 0.113 $/kwh for CPV-TEG system and 0.266 $/kwh, 0.152 $/kwh and 0.118 $/kwh for CPV-TEC system at CG = 1, 2, and 3 kW/m2. Present research may be helpful for the design and optimization of the CPV-TEH system to harvest the thermal and electric energy from the sunlight, thus enhancing its energy conversion efficiency.

Mathematical modelling and performance evaluation of a hybrid photovoltaic-thermoelectric system

A combination of photovoltaic (PV) and thermoelectric (TE), named as the photovoltaic-thermoelectric (PV-TE) hybrid system, is a promising method to effectively broaden the use of solar spectrum and increase the total power output. In this study, a mathematical model of the hybrid PV-TE system is developed based on thermal resistance theory for PV panel, heat sink, and thermoelectric generator (TEG). The electric and thermal performance of the hybrid system is then obtained by iterative calculating temperature, which is a link of electricity and heat coupling generation of the system. Meanwhile, various heat losses and weather conditions are taken into account during the numerical simulation, and the PV alone is taken as a reference for comparison. For the hybrid system, the effects of concentration ratio and temperature coefficient on system performance are also investigated. Results indicate that higher concentration ratio and smaller temperature coefficient of PV cells are ideal for designing the PV-TE hybrid system. Moreover, a sensitivity analysis is carried out on the thermal resistance of each part in the hybrid system and relevant performance parameters are studied. It is found that the cooling system, i.e. heat sink, dominates thermal resistance of the hybrid system, indicating that reducing thermal resistance of the cooling system is the most effective way to improve the efficiency of the hybrid system. Through employing optimum parameters, operation performance of the hybrid system has been evaluated under two typical weather conditions, and results show that the PV-TE still produces 1.24–2.85% higher electricity than PV alone although the cell temperature in PV-TE is higher. If the material’s physical property is improved, the electrical benefits of the combining PV and TE will be enhanced and it will be promising for application in the future.

Compound nanostructure capable of realizing full-spectrum utilization of solar energy for PV-TE hybrid systems.

The photovoltaic-thermoelectric (PV-TE) hybrid system can achieve full-spectrum utilization of the solar spectrum, but surface reflection has always been an important reason to suppress its power conversion efficiency. Therefore, a novel composite nanostructure (CN) is proposed by the finite-difference time-domain (FDTD) simulation method to reduce the surface reflection in the spectral range of 0.3-2.5μm, which consists of a pyramid and grating structure. For the sake of generality, this paper studies the spectral reflectance of the CN under multiple parameters. The results show that the CN integrated pyramid and grating correspond to excellent anti-reflection performance in the short wavelength range and long wavelength range, respectively, compared to a unitary structure, achieving anti-reflection in the full spectral range. In addition, the CN expresses the insensitivity to the structural parameters, and has lower reflectivity compared with a commercial battery. The mechanism for achieving this full-spectrum anti-reflection is mainly to enhance the path of light in the medium to enhance absorption and achieve high transmission under the action of the waveguide. This paper implements ultra-broadband anti-reflection of a compound nanostructure for full-spectrum utilization of solar energy, and provides a solution to improve the power conversion efficiency of PV-TE hybrid systems.