Looking for a chinese PhD student on PV aging
PhD offer for chinese student on PV Aging test bench and application
School - Location: CentraleSupélec
Web site: www.lgep.fr
Name of the supervisor: Phulpin Tanguy
Title: Photovoltaic cell reliability in generator mode
Scientific field :
Engineering & Technology: Electrical, Electronic and Telecommunication Engineering
Free Key words: Photovoltaïc cell, reliability, generator mode, solar reluctance machine, aging, solar water pumping
Details for the subject:
A solar-powered switch reluctance motor drive using photovoltaic transistors (PVT) has been proposed in “A switched reluctance motor drive using photo-voltaic transistors: principle, prototype, experimental and numerical results” in 2017 . Such systems are suitable for off-grid applications with high-reliability requirements, like water pumping in remote areas. His control is achieved using a shutter driver by the motor rotor over the PVT. This system could be more affordable and reliable than conventional ones and results show that the PVT inverter-fed switched reluctance motor is operating as expected and provided useful power. The reliability is however crucial for this kind of application and the photovoltaic cells should resist a harsh environment.
The PVT reliability has to be evaluated to guarantee a longer life to the installation. The solar cells are not designed with a specific technology but they are used differently than usual. Instead of being a generator, another quadrant is required. The failure mechanisms are hence different because the solar cell doesn’t have the same constraints. We will have to design several tests to verify the cell reliability, to compare the failures with a standard solar cell, and to understand the different failure mechanisms link to its new utilization.
The issue of this project is the validation of the solar cell failure mechanism with our application. A new way for solar cell utilization can be proposed, encouraging new applications. The solar energy is crucial for Africa and should be exploited as much as possible.
Description of the work:
Solar energy has to be encouraged in Africa and this project based for example on a water pumping application is really promising . The reliability is a fundamental step to create a clean installation, working for a long time. An ethical application with unmaintainable devices, creating pollution and being inefficient, is not suitable. That’s why it is necessary to understand the failure mechanism of the PVT and to propose solutions to avoid them.
We are proposing to determine the difference between a new range of possibilities for solar panels and their classical use. The failure mechanism has to be compared to guarantee the best efficiency of the PVT. We planned in this work to use classical mono-crystalline silicon solar cells but our experiment can serve all kinds of solar panel technology. As soon as the test bench will be set, several devices could be evaluated and progress could be realized in the solar cell failure mechanism. This work would be a precursor for developing solar energy with another range of applications.
Classically three stresses are used to evaluate solar cell reliability . First, the aging with temperature cycling from low (-40°C) to high (110°C) is applied to the cell. It can be operated for a long time as 500 cycles before a failure appears. It hence takes a long time but this test is the most common for evaluating the reliability. The second stress corresponds to the UV exposition. Specific wavelength (visible and UV) with high incident power is necessary to stress the cells because their energy is high enough to create failures. The stress takes also a long time and is planned for 333h. Regulation of the temperature becomes mandatory to observe only the UV impact. Then the third stress is the Damp Heat (DH) where the cell has to be characterized in a climate chamber with modification of pressure, humidity, and temperature. We will not realize the third one because the failure is localized more in the encapsulation design with corrosion for example. Failures shouldn't be different for our application than usual.
As the two stress desired are running for a long period, we would like to create a system able to stress several cells at the same time, to obtain statistical results, representing the main failure mechanism observed in reality on the solar cells. This is possible to numerically control the two experiments composed of sensors, suppliers, source meters, etc (temperature cycling and UV exposition).
For the first one, each cell is polarized in quadrant 1, just before the fatal current increase and the temperature is cycling. Every ten minutes, a standard I-V characterization is realized to ensure the cell is not broken. The controller will control the cycles and will manage every device. It also stops the supply voltage during characterization. All the devices are localized on the climate chamber with a light switch on for electrical characterization. Because of the temperature cycling, the light will be composed of LED devices to guarantee the efficiency of the characterization.
For the second stress, the UV exposition, the temperature has to be controlled and a regulation system is recommended to evaluate only the UV effect. The UV light heats the device under test. This temperature regulation can be done by several Peltier modules and sensors. The equipment provides by the GeePs laboratory, specialized in solar cell energy permits to the evaluation of the wavelength applied for several power levels. Finally, the GeePs tools will be really helpful to understand the failure mechanism as optical spectroscopy, luminescence and Raman study, atomic force microscopy, etc. 
 L. Quéval, A. Coty, L. Vido, R. Gottkehaskamp, and B. Multon, “A Switched Reluctance Motor Drive Using Photovoltaic Transistors: Principle, Prototype, Experimental, and Numerical Results“, in IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 53, NO. 5, SEPTEMBER/OCTOBER 2017.
 S. Meunier, M. Heinrich, L. Quéval, J. Cherni, L. Vido, et al. “A validated model of a photovoltaic water pumping system for off-grid rural communities“, in Applied Energy, Elsevier 241, pp.580-591, in 2019.
 V. GUIHENEUF, “Approche multi-physique du vieillissement des matériaux pour application photovoltaïque“, Thèse. Matériaux. Université Paris-Est, 229 pages, 2017 .
 T. Phulpin, A. Jaffre, J. Alvares, M. Lazar, “Development of SiC reliability study tool“, in Solid State Electronics Letters, Volume 1, Issue 2, Pages 131-139, July 2019.