8.1 Evaluation of Solar-based Energy Harvesting for Indoor IoT Applications

Abstract

Internet-of-Things (IoT) devices and other embedded devices are more and more used to measure different conditions inside of buildings and industrial facilities as well as to monitoring machines or industrial processes. IoT sensors communicate wirelessly and are typically supplied by batteries. Energy harvesting can be used to extend their operational time or enable self-sufficient supply of them. Energy from the environment is converted into electrical energy by energy harvesting devices (EHDs), for example solar cells or thermo-generators. However, the available output power of the EHDs is highly dependent on the mounting location as well as on environmental conditions and may vary greatly over time. Therefore, it is meaningful to evaluate the EHDs at the location of use over a certain period of time in order to characterize them in real world scenarios. This paper presents the evaluation setup and the results of the characterization of four different solar cells at different locations in an office building and at different weather conditions. Furthermore, a method is presented to estimate the possibility to supply embedded device using energy harvesting. The results can be used to simplify the selection of a suitable EHD and the design process of an energy management system. The method is applied on two different use cases to estimate the needed size of the solar cells to enable a continuous supply.