How do You Power the Navy’s Next Generation of Unmanned Undersea Vehicles (UUVs)? The Answer is in the Water

How do You Power the Navy’s Next Generation of Unmanned Undersea Vehicles (UUVs)? The Answer is in the Water

By: Dan Wise, Director, Federal Marine Programs, Siemens Government Technologies, Captain, U.S. Navy (Retired)


  • Siemens Government Technologies (SGT) is providing a power solution for U.S. Navy unmanned undersea vehicles (UUVs)
  • SGT will feature a replica of the technology at the Naval Submarine League’s Annual Symposium.

Since the very first undersea vehicles were designed for military operations more than three centuries ago, the greatest challenge has always been how to sustain power – absent air – while under the sea. The earliest vehicles were of course human powered. Thanks to the advent of the combustion engine, batteries, and of course nuclear power, the ocean deep is not the mysterious place it once was.


But as the U.S. Navy pursues a new fleet of unmanned undersea vehicles (UUVs), the power required to perform such critical missions remains elusive for lithium ion battery solutions in use today.


Enter into the picture polymer electrolyte membrane (PEM) fuel cells.


People can be a bit skeptical when I tell them there’s a submarine propulsion technology deployed at sea today comprised of the very molecules that constitute water – namely hydrogen and oxygen. But it’s not the stuff of science fiction, it’s reality.


PEM fuel cells use stored hydrogen and oxygen to initiate an electro-chemical process that produces electricity, along with some residual gas and water as byproducts. Siemens PEM fuel cells have been delivering air-independent power (AIP) generation across allied navy submarine fleets for well over a decade. Yet it’s a technology that remains untapped here in the U.S.



Submarines with PEM fuel cell AIP systems in service today include the German designed Type U209, Type U212, and Type U214 as well as the Israeli Dolphin. This established, mature, and well understood technology can be directly incorporated for other applications of interest to the Navy, notably UUVs.


The fundamental advantage of energy stored as a consumable fuel is energy density. State of the art lithium batteries have an energy storage density of approximately 0.23 kWh/kg. But hydrogen, with associated stored oxygen, has a net stored energy of approximately 3.73 kWh/kg, which makes it a far better fit for larger, extended duration UUVs.


This helps advance two key interests for the Navy. The first is to operate more efficiently and effectively – always a top priority. And the second is to leverage technology to perform missions that, until recently, were too complex or dangerous for manned vessels.


In August, Siemens collaborated with Colorado State University Engines and Energy Institute for an independent third party evaluation of a land-based PEM fuel cell, with a testing regiment representative of energy loads required by a large UUV. The test results and analysis detailed the suitability of the PEM fuel cell to meet the expected mission profiles of the Navy’s proposed larger UUVs of the future.


This week, at the Naval Submarine League’s Annual Symposium, Siemens Government Technologies will have a three-quarter scale replica model on hand to engage Navy leadership and industry partners on the merits of adopting a proven power solution – deployed today – to help meet the new mission needs of tomorrow.


Published On: November 7th, 2018