The U.S. Navy plans to conduct a series of tests on its hybrid-electric propulsion system for destroyers in order to assess its potential for future application on one of the ships’ two propellers, service officials said.

The technology, now in use on the USS Makin Island and being engineered into the next-generation America-class, big-deck Amphibious Assault Ships; the USS America (LHA-6) and the USS Tripoli (LHA-7) are engineered with a hybrid-drive propulsion system, meaning the ships can use both diesel electric propulsion as well as gas-turbine engines.

“We’re beginning to explore the possibility on some other surface combatants such as DDGs (destroyers) and we’ll be looking to do more of those tests over the next few years. If those prove out as they have aboard the amphibs, that is something that we’ll look to take out to more and more DDGs during their upgrade cycle,” said Tom Hicks, Deputy Assistant Secretary of the Navy, Energy. “Based on the success of the Makin Island, we’ll look to begin to identify ships that are in their mid-life upgrade where we could bring that type of technology aboard.”

When it comes to ship propulsion, hybrid-electric propulsion involves a gas turbine engine as well as an electric motor and diesel generator. The electric motors can help propel the ship at speeds up to around 12 knots, and the generator can generate electricity for the ship.

When traveling at speeds greater than 12 knots, the ship can then rely upon its gas turbine engine. At the same time, the generators can also provide on-board power for many of the ships systems such as sensors, weapons and other electronics, according to Navy officials.

Much like their amphibious counterparts, the DDGs are equipped for missions likely to require moving at slower speeds, potentially closer to shore, Hicks explained.

“We’d be looking to potentially put hybrid-electric drive aboard one of the two propellers on a DDG. We think that is all that is going to be necessary to get the maximized impact. Those types of surface combatants do spend a fair amount of time not operating at high speeds, so that seems to be a perfect sweet spot for hybrid electric drive,” Hicks said.

Another energy-efficiency technique being utilized by the Navy is the addition of what’s called a “stern flap,” essentially an additional piece of the ship which changes the flow characteristics under the boat, impacting how water flows under and around the hull, Navy engineers explained.

Hicks also talked about anti-corrosion hull coatings and paints which make the surface of the hull more slippery and therefore able to more smoothly glide through the water.

“Hull coatings or propeller coatings are things which make the ship more resistant to the turbulent effects of the water,” Hicks said.

Each of these innovations wind up reducing the amount of fuel needed to propel the ship, Hicks added.

Another energy-efficiency increasing innovation is something called “Smart Voyage Planning Software,” a software program able to maximize route efficiency by calculating and integrating a wide swath of weather conditions and environmental factors likely to impact ship propulsion.

“We’re getting more fidelity in terms of the data that exists out in the ocean. All of the conditions that exist such as water conditions, current, temperature and wind all really have an impact on a ship’s ability to reach certain points. The idea is to look at all the environmental factors that impact the ship’s ability to get from one point to another,” Hicks explained.