Peter M. Winn

10 MW Class Superconductor Wind Turbine Generators

High temperature superconductor (HTS) technology enables generators with one third the weight and one half the losses of conventional machines. These technologies enable a significant reduction in the size and weight of 10 MW-class generators for direct-drive wind turbine systems and reduce the cost of clean energy relative to conventional copper and permanent-magnet-based generators and gearboxes. With compact and light-weight 10 MW-class HTS generators, installation and low maintenance operation of high power wind turbine systems becomes practical and enable cost-effective access to wind resources. Under a program funded by the NIST-Advanced Technology Program, key generator technologies for a 10 MW class generator have been developed. This paper summarizes work under the NIST and internal programs.

Development of a Pressure Box to Evaluate Reusable-Launch-Vehicle Cryogenic-Tank Panels

A cryogenic pressure-box test machine has been designed and is being developed to test full-scale reusable launch vehicle cryogenic-tank panels. This machine is equipped with an internal pressurization system, a cryogenic cooling system, and a heating system to simulate the mechanical and thermal loading conditions that are representative of a reusable launch vehicle mission profile. The cryogenic cooling system uses liquid helium and liquid nitrogen to simulate liquid hydrogen and liquid oxygen tank internal temperatures. A quartz lamp heating system is used for heating the external surface of the test panels to simulate cryogenic-tank external surface temperatures during re-entry of the launch vehicle. The pressurization system uses gaseous helium and is designed to be controlled independently of the cooling system. The tensile loads in the axial direction of the test panel are simulated by means of hydraulic actuators and a load control system. The hoop loads in the test panel are reacted by load-calibrated turnbuckles attached to the skin and frame elements of the test panel. The load distribution in the skin and frames can be adjusted to correspond to the tank structure by using these turnbuckles. The seal between the test panel and the cryogenic pressure box is made from a reinforced Teflon material which can withstand pressures greater than 52 psig at cryogenic temperatures. Analytical results and tests on prototype test components indicate that most of the cryogenic-tank loading conditions that occur in flight can be simulated in the cryogenic pressure-box test machine.

Design, Development, and Testing of a Cryogenic Reciprocating Expansion Device

A lightweight, easily maintained helium expander system has been developed to provide reliable, low cost refrigeration in the 20 K to 40 K temperature range. The expander consists of a 2 inch diameter piston controlled by a combined hydraulic/pneumatic system. During the expansion process some of the energy released from the helium gas is stored in the hydraulic system. The stored energy is used to return the piston to its lower position. The expander assembly is built as a self- sealed removable pod that can be replaced with a new pod without warming or contaminating the main system. The expansion engine is controlled by a processor, which reads an LVDT signal and opens and closes valves in a timed sequence. The LVDT rod moves up and down with the piston giving a signal to the processor which controls the valve timing logic. This design is unique in the sense that the pressure of the gas after expansion can be easily adjusted by the valve timing. The hydraulic nature of the drive mechanism also allows us to compensate for the high back-pressure during the resetting of the piston. A typical reverse Brayton cycle operates with a compressor discharge of 1.7 MPa and a suction pressure of.1 to.138 MPa. This system is designed with the option of a higher suction pressure, allowing for higher throughput at similar power input. An adiabatic efficiency of 60% was demonstrated during testing.

Design and Fabrication of a Zero Gravity Liquid Cryogen Cooler Using Surface Tension Confinement Technology

AET, Ltd. was contracted by NASA GSFC to design and fabricate a zero gravity liquid cryogen cooler for use in NASA’s Hitchhiker Program. The cooler was designed to fit inside a standard Get Away Special (GAS) canister located in the cargo bay of the space shuttle. The main function of the cooler is to provide an inexpensive way for commercial customers and the research community to perform cold temperature testing in a zero gravity environment. Surface Tension Confinement Technology used in the design of the cooler, allows a liquid cryogen to be used as the cooling media without the traditional problems associated with the use of fluids in zero gravity. The paper discusses the design of the cooler, the testing results, and the epoxy joint design criteria that was developed during the contract, for a specific epoxy joint used in the design of the cooler.