• Energy Research

This project’s mission was to achieve significant advances in the practical application of bulk high-temperature superconductor (HTS) materials to energy-storage systems. The ultimate product was planned as an operational prototype of a flywheel system on an HTS suspension. While the final prototype flywheel did not complete the final offsite demonstration phase of the program, invaluable lessons learned were captured on the laboratory demonstration units that will lead to the successful deployment of a future HTS-stabilized, composite-flywheel energy-storage system (FESS).

Research progress on the development of composite flywheels for use in a heat-engine/flywheel hybrid vehicle is reported. A design concept was generated for the instrumented containment assembly. Analytical results indicate that both the ''dead-weight-loaded bandwrap'' flywheel and the ''prestressed-rim bandwrap'' flywheel should significantly outperform Union Carbide Corporation-Nuclear Division's FY 1976/76T ''bandwrap composite'' flywheel. Analytical results to date indicate that the use of a hybrid rim with two or more materials of different elastic moduli, such as Kevlar-29/epoxy overwrapped with Kevlar-49/epoxy, should improve the flywheel performance. Additional transverse tensile characterization of Kevlar-49/epoxy, using three different room-temperature-curing epoxy resin formulations, resulted in no significant improvement over the approximately 1-ksi strength level previously attained in the FY 1976/76T flywheel.

The following paper presents a modular system for active power support in wind generators. It works on the base of a Flywheel Energy Storage System (FESS) coupled to the DC link of a medium voltage back-to-back multilevel converter. Two ANPC-5L compose a full-scale converter interface and a third converter tied to the DC link drives a flywheel through an induction machine. All converters have predictive controllers (FCS-MPC) and the charge-discharge management is decoupled from the wind conversion system. It is fully decentralized and does not need any communication with the rest of the system, which provides modular storage capability.

A report is given summarizing Union Carbide Corporation-Nuclear Division's (UCC-ND's) composite flywheel program objectives and accomplishments for the period from May 1 through June 30, 1976. The necessity and urgency of national energy conservation is a well-recognized fact. Mechanical-energy storage, using rotating flywheels, is one of the few known methods for energy storage, and flywheels probably have the highest potential effectiveness for energy storage of any method now available. Initial application selected for the development of the composite flywheel is the heat engine/flywheel hybrid propulsion system for a vehicle, because of its high potential for the conservation of petroleum fuel in both the near and long-range time frames. Efforts have focused into key areas consistent with its experience base: state-of-the-art flywheel development, spin testing, and containment development. An operating performance goal of 20 watt-hr/lb (20 Wh/lb) energy density at an energy level of 0.56 kWh has been set by UCC-ND. The 20 Wh/lb goal encompasses both the composite flywheel and the hub that connects it to the shaft. It does not include the shaft. The goal exceeds the present performance of isotropic flywheels, and is also at the upper limit of current laboratory technology reported in the literature for compositemore » flywheels. The thick rim with radial overwrap bands was selected as the initial design concept. Kevlar-49/epoxy was selected as the construction material, and the end of the design phase is near. A process for fabricating full-scale Kevlar-49/epoxy thick rims was developed, and full-scale rims were successfully wound. More detailed information is presented on the development plan for this budgetary period, and the present accomplishments with respect to: (1) flywheel design, analysis, and fabrication and (2) spin testing are discussed.« less

The program to design, fabricate, and performance test a prototype, vehicular-sized, composite flywheel is described. The overall program scope encompasses development of both the flywheel and its containment; however, the FY 1976-1976T objective was directed toward development of the flywheel and testing it in existing facilities. The development effort was successful, leading to successful testing of a flywheel design which demonstrated an energy density performance of 10.1 Wh/lb during spin testing. The initial application selected for development of the composite flywheel was the heat engine/flywheel hybrid propulsion system for a vehicle. This application was selected by the ERDA Advanced Physical Methods Branch staff because of its high potential for conservation of petroleum fuel in both the near and far-term time frames. Other applications, such as utility load leveling, represent potential areas for significant energy savings but require more extensive development programs and funding resources. Successful development of a high-performance, composite, vehicular flywheel represents one step along the development path leading toward larger, higher-energy storage flywheel applications.

Vehicle propulsion concepts utilizing flywheel energy are described. Analyses are presented for sizing an inductor motor/alternator/flywheel for application to a 3000 pound vehicle. Component tradeoffs are included for the inductor motor/alternator drive, the solid state inverter/rectifier, the control circuit, and a composite flywheel. Design specifications for the machine are established and a test plan defined.

Plug-in electrical vehicles will play a critical role in future smart grid and sudden connection of electrical vehicles chargers may cause huge power-peaks with high slew-rates on grid. In order to cope with this issue, this paper applies a distributed cooperative control for fast charging station with dedicated paralleled flywheel-based energy storage system. The distributed DC-bus signaling method is employed in the power coordination of grid and flywheel converters, and a distributed secondary controller generates DC voltage correction term to adjust the local voltage set-point through a dynamic consensus based voltage observer by communicating with its neighbors. The control system can realize the power balancing and DC voltage regulation with low reliance on communications. Finally, real-time hardware-in-the-loop results have been reported in order to verify the feasibility of proposed approach.

This report documents a high-level analysis of the benefit and cost for flywheel energy storage used to provide area regulation for the electricity supply and transmission system in California. Area regulation is an 'ancillary service' needed for a reliable and stable regional electricity grid. The analysis was based on results from a demonstration, in California, of flywheel energy storage developed by Beacon Power Corporation (the system's manufacturer). Demonstrated was flywheel storage systems ability to provide 'rapid-response' regulation. Flywheel storage output can be varied much more rapidly than the output from conventional regulation sources, making flywheels more attractive than conventional regulation resources. The performance of the flywheel storage system demonstrated was generally consistent with requirements for a possible new class of regulation resources - 'rapid-response' energy-storage-based regulation - in California. In short, it was demonstrated that Beacon Power Corporation's flywheel system follows a rapidly changing control signal (the ACE, which changes every four seconds). Based on the results and on expected plant cost and performance, the Beacon Power flywheel storage system has a good chance of being a financially viable regulation resource. Results indicate a benefit/cost ratio of 1.5 to 1.8 using what may be somewhat conservative assumptions. A benefit/cost ratiomore » of one indicates that, based on the financial assumptions used, the investment's financial returns just meet the investors target.« less

The results of tests performed to evaluate the performance of selected high-speed flywheel bearings and shaft seals are reported, and work performed on the development of a high-speed composite flywheel rotor is described. The overall program objective is to develop a composite flywheel system for primary energy storage in a flywheel powered vehicle. These initial tests were intended to evaluate the performance of full-size composite rotor elements, high-speed bearings and shaft seals for that system under conditions simulating as closely as possible those anticipated in a finished vehicle. Performance of the angular contact ball bearings is reported to be satisfactory at all speeds; a simplified lubrication system is recommended for second generation hardware. Performance of the ferrofluidic shaft seals is reported to be marginal, as they failed to hold a hard vacuum at the maximum design speed. Several concepts for improved seals are offered for second generation hardware. The test objectives for the high-speed composite flywheel rotor were not achieved due to dynamic instability problems with the test hardware. Recommendations are offered for the design of second generation hardware, and a scope of activities is proposed for the second phase of this program.