A team of engineers led by UConn engineering professors Yang Cao and Ali Bazzi is conducting groundbreaking research on electric propulsion, moving the U.S. Navy closer to a shift in how submarines are powered.<\/p>\n
With funding from the U.S. Department of Defense and Department of Energy, the researchers are developing electrical insulation for use in the manufacture of Next Generation Integrated Propulsion System (NGIPS) motors for military electric propulsion that will provide 50 percent higher power density.<\/p>\n
The U.S. Navy is currently shifting from mechanical drive to electric drive in many propulsion systems\u202ffor\u202fcombat\u202fships, just as plug-in electric vehicles\u202frun on electrical motors.\u00a0The first modern electric drive submarine will be the Columbia class submarine, which replaces the Ohio class. The Columbia class is scheduled to begin construction in 2021 and enter service in 2031.<\/p>\n
\u201cOn a nuclear submarine, space is tight,\u201d says Cao, associate professor of electrical and computer engineering.\u202f\u201cIn order to fit electric drive systems in [the next generation attack class submarine], electric drive components will all need to be smaller.\u201d<\/p>\n
The improved insulation material enables the motor to be much smaller. Without it, says Cao, it would be almost impossible to fit electric drive propulsion systems on these future attack class submarines.<\/p>\n
Since the cost\u202fis roughly in proportion to the volume of the\u202felectric\u202fmachine, reducing the\u202fsize can also save money.\u00a0As one of the world\u2019s\u202flargest\u202fsingle energy consumers, the U.S. Department of Defense uses about 30,000 GWh of electricity annually, at a cost of nearly $2.2 billion.<\/p>\n
Electric motors are easier to control than internal-combustion engines, while also saving energy.<\/p>\n
But while integrated electric-propulsion drive systems operate at high power and high frequency, the performance and reliability of these systems depends on their ability to efficiently dissipate thermal energy from the electronics and machines during operation.<\/p>\n
Conventional insulative materials used in these systems to withstand high voltages are also good thermal insulators that prevent such heat dissipation.<\/p>\n
The UConn team has developed a new 2-D, nanostructured dielectric material with highly improved electrical and thermal characteristics. This material has demonstrated, without redesign, a 15 percent improvement\u202fin torque density\u202fof the motor on a\u202fDDG1000, the first\u202fall-electric battleship.<\/p>\n
General Dynamics Electric Boat considers the program “revolutionary,\u201d wrote James R. Moody, director of business development, payloads and sensors at Electric Boat, in a 2015 letter supporting UConn\u2019s application for a grant from the Office of Naval Research.<\/p>\n
Electric Boat\u2019s in-kind support has involved evaluating the impact of thermal performance improvement on motor power density, and assessing the technology\u2019s readiness for Naval shipboard applications.\u00a0The team will be working for two more years on this program to fully demonstrate\u202fthat the materials they\u2019re developing will produce similar savings in the real world.<\/p>\n
The goal is to further\u202foptimize the system to generate 20 percent more torque, and complete the accelerated aging test to ensure high service reliability. \u201cThis\u202fcould be game-changing,\u201d says Cao.<\/p>\n
The new technology also has advantages for national security, according to Bazzi, UTC assistant professor of engineering innovation in electrical and computer engineering at UConn.<\/p>\n
Typically, the U.S. imports strong magnets that contain rare-earth elements, but induction machines are independent of these elements and are easier to control, Bazzi says. One downside is that they have slightly lower efficiency and lower power density than their permanent magnet machine counterparts.<\/p>\n
\u201cImproving the power and torque densities of induction machines would make them more competitive in terms of size, ease of control, and supply chain from a national security perspective,\u201d he says.<\/p>\n
Electric propulsion also has the potential for commercial applications beyond electric cars and buses.<\/p>\n
\u201cThis is just the first application,\u201d Cao says, noting that the military is very interested in dual-purpose research. \u201cIf this research can be used by industry, this would help expand the supplier base, provide jobs, and potentially lower the cost for the Department of Defense. If this could be further extended to much broader, civilian applications, the impact could be huge.\u201d<\/p>\n