ARPA-E Sponsored Free Piston Controller for Natural Gas Compressor

UT Austin is developing an at-home natural gas refueling system that compresses natural gas using a single piston. Typically, at-home refueling stations use reciprocating compressor technology, in which an electric motor rotates a crankshaft tied to several pistons in a multi-stage compressor. These compressor systems can be inefficient and their complex components make them expensive to manufacture, difficult to maintain, and short-lived. The UT Austin design uses a single piston compressor driven by a directly coupled linear motor. This would eliminate many of the moving components associated with typical reciprocating compressors, reducing efficiency losses from friction, increasing reliability and durability, and decreasing manufacturing and maintenance costs.

The Texas Electric Vehicle (EV) Program

hydrogen bus

The University of Texas at Center for Electromechanics (UT-CEM), the Texas Energy Conservation Office, and the Texas Department of Commerce have jointly organized an electric and hybrid-electric vehicle program in Texas. The program capitalized on the advanced technical position in four key dual-use technologies that has been established by UT-CEM and focuses on technology development and transfer to firms capable of production. The program also involves innovative linkages with users and customers during the development process to simultaneously develop initial market interest, attract investment, and identify user test platforms. The program is intended to serve as a beginning, with an expanding number of participants and technologies in future years. Funds are being provided by Federal Agencies, State Agencies, utility companies, industrial project partners, a metropolitan transportation authority, and commercial investors.

The Texas Electric Vehicle Program consists of four interdependent projects to develop: efficient low-cost homopolar EV traction motors; small flywheel batteries for vehicle power management; large flywheel batteries for utility power management (such as would be required for practical electric vehicle recharge stations) and hybrid electric railroad locomotives; and improved electromechanical active vehicle suspensions. The breadth and scope of the principal organizations (over a dozen) participating in the projects provide the strength of the program — the interaction of the manufacturers, the developers, and the users during the development process. Similarly, the program’s complexity and the diverse requirements of the 10 different organizations that are providing funds has heightened the dependencies of the projects. For example, the Texas Office of State-Federal Relations is primarily interested in job creation in Texas. The Advanced Research Projects Agency (ARPA), on the other hand, is primarily interested in electric vehicle technology development for both military and commercial applications. Technical inter-dependencies also exist. For example, the utility flywheel battery program relies on the vehicular flywheel battery project to solve flywheel battery manufacturing cost issues and flywheel battery containment and safety problems.


Small Flywheel Battery Systems For Vehicle Power Management

UT-CEM is exploiting its high performance composite rotor technology, developed with over $20M of DoD funding, to develop a stand alone flywheel battery system, complete with power electronics, for vehicular applications. The flywheel will store 2 kW-hr of energy, and produce 100 to 150 kW of power. Other members of the team, AVCON and Allied Signal Aerospace Company are providing complementing magnetic bearing and motor/generator expertise respectively.

The primary objective of the project is to develop dual-use stand alone flywheel battery systems, for military and commercial applications. Future military requirements for power averaging are more demanding than commercial applications, and will demand the advanced rotor technology being applied in this project. This becomes even more critical with the next generation of combat vehicles, employing EM guns, EM suspensions and EM countermeasures. Until now, flywheel battery systems have either been low risk and low performance devices or expensive, high risk, moderate performance designs. Under this ARPA program, UT-CEM is providing the advanced composite rotor technology, developed in DoD programs, for the most demanding high performance flywheels. Additionally UT-CEM is developing techniques to reduce costs for the high performance rotor to be as low as or lower than conventional wet wound filament technology. With conservative operating stresses UT-CEM’s predicted power density is in excess of 1,600 W/kg, and energy density over 30 W-hr/kg. These are appropriate and attractive performance parameters for this load leveling application where power averaging and reliability are the objectives.

This project, to fabricate a moderate-cost high-performance composite flywheel battery system, capitalizes on an alliance of mass transit providers, university technology developers, and commercial manufacturing entities. For this reason, the program structure encompasses the elements necessary to develop the required production technology, formulate component manufacturing plans which are guided by customer-driven system designs, and introduce the technology to the marketplace. Each member of the alliance has a vested interest in producing these systems in large numbers and is investing considerable resources to insure the success of the program with the ultimate goal of producing a commercially viable unit. Commercial viability will also be enhanced by the composite rotor manufacturing tasks to reduce fabrication costs in the project.

Partner Organizations
ARPA-E, Texas Office of State and Federal Relations, Texas Energy Coordinating Council, Texas Advanced Technology Program, The University of Texas, Houston MTA, Central and Southwest Services, Allied Signal, AVCON, and Motor Dynamics, Inc.


Mr. Mike Lewis

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