Abstract
Energy autonomy for the connected devices around us is becoming an important issue today. Various sources of ambient energy can be used to supply them with power. However, depending on the type of environment in which they are set up, the ambient energy sources available may vary. Besides, the amount of energy from the available sources can be uneven and inconsistent. The company Bureaux A Partager (BAP), the initiator of this thesis, intends to apply this approach to smart tablet displays used for the shared areas of its offices to reduce the constraints and costs of their installation and use. Yet, the amount of energy consumed by this digital tablet is between one hundred and one thousand times greater than that of devices generally made autonomous by this method of power supply. Therefore, making the tablet autonomous is a major challenge that requires precise knowledge of the energy sources available in its environment and the amount of energy harvestable from them.This industrial thesis first explains how the light seems to be the ambient energy most likely to make a device that consumes on average more than 10 mW of power autonomous in an office environment. The necessity to know the energy available in practice in a specific environment to develop energy harvesting systems adapted to it led to developing a calculation method. It is based on measurements of a photovoltaic converter's electrical and optical characteristics and the ambient light spectrum. The calculations are validated by comparing them with the energy harvesting measurements of a prototype energy harvesting systems. A low-cost analysis system with a low spectral resolution is developed to overcome the constraints associated with the costly and complex instruments required to acquire the light spectrum. Using light source classification and spectral reconstruction methods, the system can perform recoverable energy evaluations equivalent in accuracy to those obtained with high-resolution instruments. Finally, the results of the observations obtained made it possible to establish that, to make the BAP display tablets autonomous, an energy harvesting device with a surface area of approximately 250 cm² of gallium arsenide cells would be suitable.