Design of a Solar Cell Emulator

Problem Definition:


Solar panels have known a steep rise in the past few years and will play an important role in the search for an efficient, green, reusable energy source. The efficiency of the commonly used polycrystalline silicon solar cells is about to reach its theoretical maximum. However, a lot of improvement can still be made when looking at how the generated energy is extracted from the solar panel.

One of the main problems that can pull the total efficiency down is caused by partial shading. Partial shading is the effect where only a small part of the total panel is shaded. The problem arises because the individual solar cells in a solar panel are serially connected: the current through every cell must be the same. If one cell for whatever reason (e.g. a shade) generates a lower current, the total output current is reduced, which is detrimental for the efficiency. At the moment we deal with this problem by grouping several cells in so-called substrings and placing a bypass diode in parallel. This way, the substrings containing current limiting cells can be bypassed. It is clear that this is not ideal: the power that is still available in that substring is lost and on top of that extra power is dissipated in the bypass diode. One of the current projects aims to create a more intelligent solar panel. It consists of 'intelligent bypasses' to reduce the power loss caused by the bypass diodes. A more complicated design tries to create series/parallel connections between the substrings in order to optimize the power output, depending on the exact lighting conditions..

Objectives:


Ideally, these design should be tested using a large number of solar cells with different characteristics and under different lighting conditions. It is clear that for a test set-up, this is not realistic.

The goal of this master thesis is to create a test set-up allowing us to test the several deisgns as realistically as possible. In short, this means that a current source needs to be deisgned that is (digitally) adjustable (e.g. 50mA - 10A) and electrically behaves as a solar cell or a series of solar cells (also adjustabe). On top of that, several such current sources could be placed in seris or parallel, so it has to have a modular design.

The student has the freedom to go as far as he or she wants in this. There are probably simple solutions with limited functionality. Adjusting the characteristics of the system can be done through custom software. The test set-up itself can be partially automated, etc. We leave this to the motivation and creativity of the student.

Keywords:

solar energy, green energy, photovoltaic systems, analog design, digital design, software design

Location:

Ardoyen CMST + at home.