Photovoltaic Thermoelectric Devices Research Articles

Is it possible for a photovoltaic-thermoelectric device to generate electricity at night?

Photovoltaic-thermoelectric (PV-TE) conversion is a promising method for power generation, which converts solar power into electricity using the photovoltaic (PV) effect of solar cells and simultaneously generates electricity by the Seebeck effect of the thermoelectric (TE) device based on the waste heat of solar cells. Here, the power generation of the PV-TE device at night is experimentally demonstrated using radiative cooling that harnesses the cold of the universe directly. The PV-TE device is constructed by attaching a TE device on the bottom of the glass-covered PV module, with a heat sink stuck on the opposite side of the TE device. The open-circuit voltage of the TE device integrated into the PV-TE device was measured to be approximately 9 mV, indicating that the PV-TE device can definitely generate electricity from the darkness. Moreover, a new configuration of the PV-TE device for continuous power generation in the day and night is conceptually proposed for further consideration. In summary, this work proves the possibility of the PV-TE device for nighttime power generation, which could provide an alternative pathway for a wide range of nighttime and all-day power-consumed applications, such as lower power sensors and monitors. • Nighttime power generation of the PV-TE device was experimentally demonstrated. • An average output voltage of the PV-TE device was measured as 9 mV in night. • A new configuration of the PV-TE device for continuous power generation is proposed. • This work provides an alternative pathway for nighttime and all-day applications.

Comparative analysis of thermoelectric elements optimum geometry between photovoltaic-thermoelectric and solar thermoelectric

The optimization of the thermoelectric (TE) device geometry is one of the significant ways to improve its efficiency and power output. However, the complex relationship between the Photovoltaic and the thermoelectric device necessitates the need for the study of the optimum geometry of the thermoelectric device in a hybrid Photovoltaic-thermoelectric device. Therefore, this study investigates the optimum thermoelectric geometry for optimum performance of a Photovoltaic-thermoelectric (PV-TE) device and a solar thermoelectric generator (STEG). A three-dimensional finite element method is used to model the PV-TE and the STEG with different thermoelectric leg geometries. The performance of the PV-TE with two different PV cells and different TE leg geometries is investigated and compared with that of the STEG, and the optimum leg geometry for each device is identified. In addition, the effects of solar radiation and concentration ratio on the optimized device geometry performance are presented. Results obtained showed that the optimum thermoelectric geometry in a hybrid PV-TE device is dependent on the PV cell type and this is different from that of the STEG under the same conditions. The PV-TE device with cell 1 has an improved overall efficiency when a symmetrical (rectangular) thermoelectric leg is used however, this is different when the PV cell type is changed. In fact, the PV-TE device with cell 2 has an improved overall efficiency when a trapezoidal thermoelectric leg is used instead of a rectangular leg and this is the same as is the same trend observed in the case of the STEG. Therefore, the optimum geometry for a stand-alone solar thermoelectric generator cannot be directly used as a reference for the PV-TE device as the characteristics of the PV cell affects the PV-TE optimum geometry. Results from this study will indicate the different optimum geometries of STEG and PV-TE, and also provide a solid basis for optimization efforts in hybrid PV-TE devices.

Multi-scale investigation on the absorbed irradiance distribution of the nanostructured front surface of the concentrated PV-TE device by a MC-FDTD coupled method

Photovoltaic-thermoelectric (PV-TE) hybrid device is one of the most representative ways for the full-spectrum solar energy utilization. The concentrator and nanostructured front surface have become important approaches to improve the conversion efficiency of the PV-TE device by enhancing the solar energy absorption. However, the concentrator causes badly non-uniform absorbed irradiance distribution of the PV-TE device surface, which has a great influence on the conversion efficiency of the PV-TE device. In addition, due to the multi-scale problem, it is hard to study the combined effects of the concentrator and nanostructured surface on the absorbed irradiance distribution of the PV-TE hybrid device surface. In this paper, a 3D model for a concentrated PV-TE hybrid system that employs the PV-TE hybrid device with moth-eye nanostructures and a linear Fresnel reflective solar concentrator is established. For the multi-scale problem, a Monte Carlo-Finite Difference Time Domain (MC-FDTD) coupled method is presented. At first, three parameters including duty ratio, height, and diameter are used to analyze the influences of the moth-eye nanostructure dimension on the reflectance. Then, taking the effects of the sun shape, the slope error, and the polarization of incident electromagnetic wave into considerations, the comparison and analysis on the absorbed irradiance distributions of PV-TE surface under four different conditions (with plane surface, with nanostructured front surface, with concentrator and plane surface, with concentrator and nanostructured front surface) were conducted by the MC-FDTD coupled method. Eventually, based on the precious investigation, a novel way of using different dimensional nanostructures is proposed to improve the uniformity of the absorbed irradiance distribution. As a result, this approach not only improve the uniformity of absorbed irradiance distribution very well, but also can let the mean absorbed irradiance be raised 1.6 times to reach 7644.14W/m2 compared to plane surface.

Challenges and Perspectives in Tandem Thermoelectric–Photovoltaic Solar Energy Conversion

This paper discusses enhancements of solar energy conversion by photovoltaic (PV) cells using thermoelectric (TE) generators harvesting the heat released by the PV cell. To optimize the TE–PV coupling, PV efficiency losses are analyzed by decoupling source- and absorber-dependent losses. This shows that the implementation of a tandem PV–TE device leads to a substantial increase of available power densities depending on the PV material. We further show that a major increase of the conversion efficiency can be achieved by adding an intermediate layer between the PV and the TE stage capable of absorbing the under-the-gap fraction of the solar spectrum. This increase of efficiency is discussed and commented upon also in view of the constraints PV–TE coupling imposes to the TE generator layout and to its material characteristics. The critical importance of effective heat dissipation will also be addressed. The conclusion is reached that not only could tandem PV–TE cells improve the conversion rate of existing solar cells but also that they could enable the use of lower cost PV materials, currently not considered because of their marginal PV efficiency.