Boeing Explores Fuel Cell Flight
By EV World
Boeing Research & Technology Europe, along with Intelligent Energy and Aerlyper have joined forces to explore the boundaries of flight using hydrogen and PEM fuel cell technology. The platform for their research project is a sleek, Austrian-built Diamond Dimona motor glider. EV World had hoped to do a telephone interview, but it worked out better to have them respond by email to our questions, though it obviously limits the depth at which we were able to probe the topic. The following are Thomas J. Koehler's responses on behalf of Boeing Research & Technology Europe in Madrid, Spain.
EVW: Boeing is the pre-eminent builder of large commercial aircraft powered by fossil fuels, so what's the objective of building the fuel cell aircraft demonstrator ?
BR&TE: Our objective in integrating this fuel cell aircraft demonstrator is to improve our knowledge on this technology for potential applications in aviation. Because of the tremendous strides made by the industry, it is getting harder and harder to reduce aircraft noise and emissions. The use of fuel cells to replace turbine powered auxiliary power units (APUs) would definitely be an important contribution to the environment. It would also help us maintain our history of making our airplanes ever-more fuel-efficient due to the application of new technology.
EVW: Take a moment and describe the demonstrator and the Diamond Dimona motor glider on which it's based.
BR&TE: In this project, a PEM fuel cell/Li battery hybrid system will provide electricity to power an electric motor which is coupled to a conventional propeller to propel the airplane. The fuel cell will provide the entire power for the cruise but the system will draw on the help of lightweight Li ion batteries during take-off and climb, the segment of flight that requires the most energy. The fuel cell is a Proton Exchange Membrane (PEM) type because of its relatively high power density as compared to other current fuel cells. The PEM fuel cell uses hydrogen and air as the fuel source. This was found to offer one of the highest power outputs for the least amount of weight.
EVW: Why Madrid? Why is Boeing working on this project in Spain?
BR&TE: Boeing opened the Boeing Research & Technology Europe (BR&TE) center in Madrid in 2002 as a center of excellence within Boeing's network in environmental technologies, air traffic management and safety, and therefore it is logical that BR&TE is leading this project since its inception.
EVW: What are the biggest engineering and material sciences challenges of building a hydrogen fuel-cell electric plane?
BR&TE: The biggest challenge is adopting a system designed for stationary or automotive use into the weight and volume available in a small aircraft. Fuel cells require what is called “balance of plant”, that is the pumps, heat exchangers, air blowers, etc. necessary to run the fuel cell stacks. These components are neither light nor small. The ultimate challenge is to package all of these components in a way consistent with aircraft practice.
We also have the challenge of using hydrogen in this demonstrator. Safety in aviation is a paramount concern. Hydrogen is an energy carrier with similar characteristics to the fossil fuels used today. Using appropriate design and operating procedures with hydrogen could be even safer than working with many fuels commonly used today. In this particular project, there are many safety redundancies in the design, which of course have the penalty of adding weight to the overall system. We have scheduled external safety reviews to validate the design of the on-board fuel system taking into account the surrounding electrical equipment and environment. Once we get experienced in working with hydrogen future designs might be easier.
EVW: How are you storing hydrogen and how much do you have on board and at what pressure? What's the anticipated "fuel consumption" rate?
BR&TE: The hydrogen gas is compressed at 5000 psi and stored in a lightweight composite tank from Dynetek. For the typical mission of this demonstrator, the fuel consumption is 9,187 standard liters of Hydrogen (0.7695 kg).
EVW: When do you expect to make the first flight and what are your performance goals? Have you run the "engine" yet?
BR&TE: We prefer not to commit to a definitive date. The integration of the different components in the airframe is progressing well, but the whole project is very challenging. The first flight will take place when we have the certainty that the integration is satisfactory and once the experimental aircraft has completed the certification process
EVW: How applicable is what you're learning from the project to Boeing commercial or military products?
BR&TE: Given the rate of progress in reducing the fuel cell’s weight and volume, as well as the projected capability to use common fuels, it is anticipated that fuel cells could reach a high enough maturity level within the next 10-15 years to be considered for use in a commercial airplane applications. The fuel cells will still be heavier than current turbine-powered APUs, but the cruise fuel savings and weight savings from potentially capturing water will help offset this weight penalty. When the technology is ready, we want to know exactly how to use it.
EVW: Any chance we'll someday be able to order a light aircraft powered by a hydrogen fuel cell propulsion system? How far into the future?
BR&TE: Although the technology is very promising, fuel cells are still heavier and less reliable than the conventional technology. The technology has to mature before we can even imagine a time frame for such applications.
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