Auxiliary power units (APUs) are used in trucking, aviation, and other applications to provide power for essential services other than propulsion. APUs reduce the idling time of the main engine by providing electrical, climate control, and other necessary power when the vehicle is not moving. Doing so reduces wear and tear on the main engine and more importantly, saves fuel and reduces emissions. While the main engines are designed to efficiently operate at the high power demanded during propulsion, APUs are designed to more efficiently provide the lower power needs of auxiliary services.
The two main types of APUs currently in use are diesel and all-electric, each with its own benefits and drawbacks. Diesel APUs can provide power whenever diesel fuel is available. However, these systems are noisy and emit pollutants and greenhouse gases. All-electric APUs are quiet but the batteries have a set, limited charge and runtime. Additionally, these all-electric APUs are recharged from the main, diesel motor. Because of this, all-electric APUs reduce localized emissions but are not able to mitigate all emissions associated with providing auxiliary power.
Fuel cells have begun to enter the APU market and offer the benefits of both diesel and all-electric APUs while mitigating many of the drawbacks. Fuel cells provide quiet, environmentally friendly power as long as a fuel source is available.
FCHEA member General Motors (GM) has teamed up with Liebherr-Aerospace to develop a fuel cell APU for aircrafts. GM fuel cells are able to provide quiet and efficient power during flight or on the ground with performance, runtimes, and fueling time comparable to current, fossil-fuel powered APUs. Additionally, the water emitted from the fuel cell can supply water for the aircraft. Combined, these factors create an opportunity for fuel cells to expand into and benefit a new market.
Fuel-cell powered APUs can benefit transport refrigeration units (TRU), which are attached to semi-trailer trucks to ensure cold food is transported safely in a climate-controlled environment. FCHEA members Nuvera Fuel Cells and Plug Power partnered with Pacific Northwest National Laboratory (PNNL) and the heavy-duty trucking industry to develop hydrogen-powered fuel cell TRUs for refrigerator trucks. Regulation of idling, noise, and emissions, as well as incentives have increased interest in alternatives to fossil fuel-powered TRUs and APUs for heavy-duty trucking. Pairing APUs and or TRUs with distribution facilities operating fuel cell powered material handling equipment improve the economics for both applications.
As discussed in the Port Power In Transitions blog, fuel cells and hydrogen energy are being used to provide auxiliary services on-board and at ports.For all of these applications, fuel cells and hydrogen energy provide a solution to reduce emissions in industries dependent upon fossil fuels while providing the reliability, runtime, and efficiency needed to meet the desired performance and costs targets.