Microtubular Solid Oxide Fuel Cell Power System development and integration into a Mini-UAV
Key Objectives of the project
SUAV aims to design, optimise and build a 100-200W mSOFC stack, and to integrate it into a hybrid power system comprising the mSOFC stack and a battery. Additional components of the system are fuel processors to generate reformate gas from propane and other equipment for the electrical, mechanical and control balance of plant. All these components will be integrated into a mini Unmanned Aerial Vehicle platform like the CopterCity of SurveyCopter. The project intends to optimise mission duration, while efficiency is of less concern. It will open opportunities for exploitation in other weight-limited man-portable applications. All these components will be constituents of an entire fuel cell power generator, which will first be tested in the lab and, after further optimisation and miniaturisation, in a mini UAV platform. Achievement of these objectives will result in an improvement in mini-UAV endurance by a factor of 3 over conventional battery power.
The main issues/challenges are mainly related to the mSOFC stack. The SOFC stacks in general are subject to performance degradations in terms of cycling and carbon deposition. mSOFC stacks are thermally and electrochemically cycled (start-up/shut-down procedures, temperature swings, different power output demands) causing micro-cracks and extending existing micro-cracks. Degradation by cycling may be reduced if the stack is not operated at the highest current densities and if the temperature of the stack is kept quite constant. Carbon deposition problems will be reduced if pre-reforming of the propane is used for the preparation of the stack fuel, although mSOFC can be operated directly with hydrocarbons. Development of catalysts tackling this issue is part of the project as well as the design and development of a suitable pre-reformer taking size/weight constraints and fast start-up/shut-down procedures into account.
Another challenge is the load-following capability of the SOFC stack. As SOFC are generally operated at steady-state, the SUAV stack has to follow dynamic load changes due to the flight characteristics of a mini-UAV. Load-following is also a reason for the degradation related to cycling, in this case electrochemical cycling (combined possibly with thermal cycling). This issue will be addressed by development of advanced system controls. Finally, size/weight constraints will be tackled by smart packaging, proper reactor and stack insulation and heat recovery of energy streams to pre-heat feeds as propane and more important the stack cathode air to maintain the optimal stack operating temperature.
The Top Level Requirements for the mSOFC system will be defined in the early stages of the project. Based on these requirements the SOFC stack development and the system modelling will start in the first year as well as the development of the fuel processor including the catalyst for the SOFC fuel supply. In the second year the development of the fuel cell power generator consisting of the SOFC stack and the fuel processor will be finished, integrated and tested. In the last year the fuel cell power generator is packaged and integrated into the mini-UAV. The project will be finalized by testing the mini-UAV in so-called flight missions.
Modeling of the SOFC stack but also the balance-of-plant components accompanies the development of the single components of the power generator. This deep and detailed interaction will result in advanced system models to be used for future development of SOFC-powered mini-UAVs.
Testing of the cells will be carried out in order to quantify performance, transient output, and durability. Testing of mSOFC sub-stack will be carried out to gain knowledge and characteristic data for the layout of the system. Development of the electrical balance-of-plant component includes also some electronic control mechanisms for successful flight missions of the mini-UAV. All the components (stack, reactors, heat exchangers and electronics) will be first tested before the final power generator is integrated into a mini-UAV.
Expected socio and economic impact
This project aims to produce fuel cell components of longer cycling lifetime at an economic price, thereby allowing SOFCs to be used in portable and other applications. Widespread adoption of SOFC technologies will give the environmental benefits of reduced fossil fuel usage (via increased efficiency) and reduced emissions. Because of the improved efficiency of SOFC microgeneration, the consumption of fuel will decrease. This represents a large saving of fuel cost, which in future will be a saving of imported fuel. Two other economic benefits follow from this; first, there is an export market in Europe and overseas which will reward the first successful introduction of this technology; second, the reduction in pollution will lead to significant health improvements and a drop in medical costs.