Unmanned Undersea Vehicles (UUVs). As we have reported, API’s technology played a key role in the execution of a U.S. Navy R&D contract for a novel new UUV power source, through our portable power partner and prime contractor, Ingenium Technologies of Rockford, Illinois. Following that effort, the Navy has embarked on a major new multi-million dollar program start for a Long Endurance UUV, seeking power sources other than batteries, which cannot meet the required mission duration or safety requirements. Ingenium, as prime contractor, has submitted a proposal to the Navy, and awards are expected in the mid-August time frame, with anticipated program start around October 1, 2011, the beginning of the new federal fiscal year. The Ingenium team, with AlumiFuel as the fuel source, includes one of the
top three defense contractors and a major fuel cell company. A second major new UUV program start in 2011 (for a Large Displacement UUV) is expected to open for proposals shortly, and the same Ingenium-led team also plans to respond to this solicitation. Simply put, API is in a favorable position to be an integral part of a new power system for UUVs; enabling the Navy to use these vehicles for important war fighting and anti-terrorist missions for the first time.
A fuel cell is an electrochemical device which combines a fuel and an oxidant, typically oxygen from air, to deliver power. Unlike a battery, which is closed, a fuel cell is open on at least one side, the air side being invariably open. Like a battery, individual cells can be combined together to form a stack and hence delivering whatever power is needed for the given application. The fuel at point of use is commonly hydrogen, but can be a hydrocarbon or other hydrogen containing fuel, decomposed by heat, catalytically, or simply stored at pressure. The fuel cell stack combines fuel and air to form water and potentially CO2, cleanly and efficiently. While similar to a battery, a fuel cell system is far more complex, involving pumps, blowers, condensers, etc., (collectively denoted as the balance of plant) which impact on cost and reliability.
Fuel cells can both complement and compete with batteries for portable power systems. At the very small scale (AAA-D cell), batteries are hard to beat, especially for short times as the requirement for the electrochemical converter and associated balance of plant takes up a large share of the power source inventory. As the power level and time requirement increases, the decoupling of fuel and electrochemical converter becomes increasingly advantageous, and is manifest in lightweight power sources with reduced recharge times compared to batteries. The ability to instantly swap out the fuel rather than wait for recharge is particularly advantageous for most portable applications.
While fuel cells offer advantages over batteries, they also bring issues, at least at the present state of development. Some are intrinsic (such as the need to breathe air) and others are being continuously improved (such as start-up from sub-zero temperatures, stack and component lifetimes, cost), while yet more are specific only to certain stack types (such as intolerance of atmospheric CO2 by alkaline fuel cell stacks, or orientation dependence for direct methanol fuel cells).
As they improve, fuel cells will certainly replace batteries in some applications but sealed cells will continue to be needed for start-up, for rapid load following and for short term peaks, where the battery is cheaper than a larger stack. For companies like ABSL, fuel cells offer new opportunities, the PPS Programme being one example of an exploitation path, for soldier power and beyond.More
The primary goal of this technology assessment is to provide an initial evaluation and technology screening for the application of a Fuel Cell Energy/Power System (FCEPS) to the propulsion of an Unmanned Underwater Vehicle (UUV). The impetus for this technology assessment is the expectation that an FCEPS has the potential to significantly increase the energy storage in an UUV, when compared to other refuelable Air-Independent Propulsion (AIP) energy/power systems, e.g., such as those based on rechargeable (“secondary”) batteries. If increased energy availability is feasible, the FCEPS will enable greater mission duration (range) and/or higher performance capabilities within a given mission. A secondary goal of this report is to propose a design process for an FCEPS within the UUV application.
This executive summary is an overview of the findings in the attached main report body (“UUV FCEPS Technology Assessment and Design Process”) which provides a complete technology assessment and design process report on available UUV FCEPS technology, design methodology, and concepts. The report is limited to the Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) operating on hydrogen and oxygen.More
This paper provides a technology assessment for an Unmanned Underwater Vehicle (UUV) fuel cell energy/power system, including design methodology and design concepts. The design concepts are based on the polymer electrolyte membrane fuel cell operating on hydrogen and oxygen. The technology assessment method presented is a holistic approach which combines alternative hydrogen and oxygen storage (and fuel cell system) options to provide the highest specific energy and energy density – within the constraints of the UUV application. Using this method, some surprising combinations appear as the theoretical “winners” for maximum energy storage within the application
constraints of the UUV.
The efficiency and quietness of fuel cells make them attractive power sources for the autonomous underwater vehicles of the future. However, several technical issues must be addressed before fuel cells can surpass the performance characteristics of batteries, including efficiency, reliability, durability, standby operation and storage, changes to orientation, and high shock loads. Improvements to the storage of the fuel (hydrogen or hydrogen sources) and oxidizer (oxygen) make the biggest impact on the size, weight, and utilization of fuel cell systems. Proton-exchange membrane fuel cells (PEMFCs) are the most attractive fuel cell system and already have been successfully demonstrated for use in Autonomous Underwater Vehicles (AUVs). AUVs of the future may utilize direct methanol fuel cells (DMFCs) or solid-oxide fuel cells (SOFCs) which can use liquid methanol or diesel fuel instead of hydrogen.More