The considerable increase in the number of devices needing connectivity, such as mobile phones and Internet of Things (IoT) devices, has led to an exponential rise in data volumes during the last years, that will surely continue over the next decade. Therefore, it will be increasingly challenging to provide sufficient RF resources. A novel alternative to RF communications is Visible Light Communication (VLC). VLC is a communication technology that uses visible light as an information carrier. The use of VLC for indoor applications has been rapidly growing during the last years – Light Fidelity (LiFi) technology is an example of VLC application – with photodiodes being the most widely used receiving devices. However, looking at both indoor and outdoor communication, photovoltaic (PV) cells represent a relevant alternative for detecting the information. One of the advantages of using a PV cell as receiver is the huge sensitive area for detection of the information that simplifies alignment between transmitter and receiver.

Different light sources can be used in VLC. Typically, either LEDs or LASERs are considered, depending on the characteristics of the link (such as distance, type of receiver, indoor/outdoor application). These light sources differ in terms of spectrum, directionality, optical power density and bandwidth. The performance of the whole VLC link strongly depends on the characteristics of the light source, since it affects the ability of the receiver, such as a PV-device, to detect the information when it overlaps with the ambient light, that can reach very high values, especially in outdoor applications where the ambient light is the sunlight. Therefore, the modelling and analysis of the performance of different light sources in a PV-based VLC link will pave the way towards the realisation of a PV-based communication system of the future; and it is the focus of this thesis project.

The project goals were achieved by first reviewing the characteristics of light sources, to understand their advantages and drawbacks in (PV-based) VLC. This was followed by the development of models of the VLC data-link, with a focus on the light source, which took into account various factors such as the type of light source, its location relative to the receiver, and its dynamic behaviour. This was followed by the realisation of a test setup, to characterise different light sources, and the models were then used to simulate the light distribution from the actual light sources. Finally, the framework was used to simulate a LED-based solar simulator and an outdoor VLC data-link.

Increasing concerns surrounding the influence of urban climate on the livability of cities and the health of citizens lead to a need for environmental data on a more localized scale. Self-powered weather stations that use the many WiFi networks spanning the city to transmit their data are a promising solution to increase the amount of data on localized urban climate. Conventional weather stations often measure wind, rain and sun radiance, phenomena that are heavily influenced by the many objects present in an urban environment, which is why they are usually placed outside of the city or on top of buildings. Self-powered weather stations placed on street level can be used to gather data on temperature, humidity, air pollution and noise pollution. If a good trade-off is made between the sensing capacities, the battery capacity and the solar panel size, a weather station like this can do frequent measurements throughout the year, surviving the winter months of low solar panel power generation due to reduced irradiation. In the simulations done for this project, it was found that a simple algorithm that linearly varies the relative measuring frequency of the most power-hungry sensors with the available battery charge greatly improved the average measuring frequency and lifetime of the weather station. Thanks to the increased power budget, additional sensors can be added, such as gas sensors. Furthermore, the weather station can be made more compact and affordable by reducing the size of the solar panel and/or the battery capacity of the weather station.

Due to the current trend of urbanization more people will come and live in cities than ever before. This increases the need to monitor the urban environment, to be able to improve the living conditions of the urban dwellers. Our project combines the need to monitor the local environment, with a portable, self-powered and wireless weather station. The final design consists of a solar powered and WiFi-connected weather station with autonomous functionality for one year. For our research, the focus was on the Netherlands. Part of such a project is the power management which will be dealt with in this thesis.
In the thesis, different maximum power point tracking algorithms will be discussed and compared. Furthermore, some more research is done in the hardware design, the use of different evaluation boards and battery configurations. Finally, a prototype using the incremental conductance algorithm is constructed and tested. Simulations lead to an efficiency of around 80%, which means autonomous functionality for a minimum of one year. The physical system had a lower efficiency, but autonomous functionality for one year was still achieved.