Control Design for Micro Tubular Solid Oxide Fuel Cells, Demonstrating Lifetime and Performance Efficiency

Abstract

Emerging techniques are being researched to introduce new environmentally friendly devices such as fuel cells to reshape the world into net zero carbon emissions. Currently there are different categories of fuel cells available, each category has its benefits, for this project a micro tubular solid oxide fuel cell (μSOFC) provided by the industrial partner Adelan Ltd. was used. The Adelan specific tubular design offers faster warm up, higher thermal flexibility and better sealing capabilities. However, Adelan Ltd wants a more robust control technique in the three core stages of the fuel cell which are start-up, warmup and shutdown. Cycling through these stages it is believed to damage the fuel cell significantly as thermal conditions inside the fuel cell core fluctuate the most. In this research a novel electronic control unit (ECU) is designed to improve efficiency and lifetime of the μSOFC. Furthermore, the controller is complying to the safety concerns arisen from using a high temperature device, for the product to be commercialised. The proposed controller KJ101 is designed using a four-layer PCB to reduce electrical noises and comply with CE (or UKCA for United Kingdom). This board was able to carry over the existing Adelan control technique and make further improvement and innovation. The controller is programmed in a low-level language (AVR-C using the GCC compiler) to ensure a critical oversight of the functionality while also being able to find and eliminate critical bugs early on. This method allows to have full control to the microcontroller’s functionalities and configuring them to the way that it is required for this project. A fuel cell is currently an expensive device and highly nonlinear device therefore a mathematical model was created to understand thermal responses of a fuel cell. The firmware for the ECU was calibrated and verified using an experimental μSOFC unit, this board showed that the system was able to have flexible smooth and well controlled start up and shut down processes. The proposed controller was able to improve operation by stabilizing the fuel cell at a target setpoint (such as 700°C) while also offering a flexible option of setpoints when being under operation. The temperature variation was another equivalent important topic that was improved by a proposed firmware technique. Finally, this controller was to offer multi-input multi-output control, where the fuel input was adjusted to reach the required power all while the temperature remained at a specific given setpoint by the manipulation of the cooling fans.