Integrating a Photovoltaic Panel and a Battery Pack in One Module

From concept to prototype

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Abstract

Photovoltaic (PV) solar energy is variable and not completely predictable; therefore, different energy storage devices have been researched. Among the variety of options, electrochemical cells (commonly called batteries) are technically feasible because of their maturity and stability. However, PV-battery systems face multiple challenges such as high cost and complexity of installation. Cost is the main concern when trying to enable new solutions for the solar market, especially when competing with other renewable technologies, but most importantly, with fossil fuels to reduce the effects of climate change. As a consequence, a new concept that integrates all the components of a PVbattery system in a single device is introduced. By integrating a power electronics unit and a battery pack at the back of a PV panel, referred as PV-battery Integrated Module (PBIM), the cost of the total system can decrease and become a viable alternative for the solar market. Because the concept is relatively new and not all the challenges have been previously addressed, this dissertation strives to prove the feasibility of the concept and to fill the gaps that have been identified in the literature review. Firstly, an off-grid PV-battery system was selected, and a sizing methodology was proposed to investigate the limitations and boundaries of the integrated device. Having sized the system, the thesis explored the implementation of an energy management system in order to control smartly the direction and magnitude of the power delivery. Then, a thermal model was developed to characterize the thermal response of the PBIM and to recommend a thermal management system to decrease the temperature of operation of the battery pack and power electronics. Finally, by testing a PBIM prototype and developing an integrated model that reproduces the temperature and power flows expected, a battery testing methodology was developed for finding a suitable battery technology that can comply with the requirements set by the expected operating conditions of the device. Therefore, the research carried out in this dissertation proves that the integration of PV-battery system in one device is technically feasible.