Contents:
Summary
Overview & Organization
This report details findings about technology and technology transfer opportunities at the Wright Laboratories that might be of strategic interest to electric utilities. It is based on a visit to the lab in June 1997 and subsequent contacts, as part of the UFTO multiclient project.
Background
Noting the tremendous scope of research underway in the research facilities of the U.S. government, and a very strong impetus on the government's part to foster commercial partnering with industry and applications of the technology it has developed, the UFTO program has been established as a multi-client study of the opportunities thus afforded energy utilities and their many subsidiaries.
Air Force Research Laboratory
In a major reorganization just put into effect in mid 1997, all the Air Force R&D activities were brought together into one single entity called the Air Force Research Laboratory.
From the AFRL website: http://www.afrl.af.mil/
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The mission of the Air Force Research Lab is to lead the discovery, development, and transition of affordable, integrated technologies for our air and space forces -- to keep our Air Force "the best in the world." Our mission is executed by our nine technology directorates, located throughout the United States; the Air Force Office of Scientific Research; and our central staff. Our partners include universities and industry, with whom we invest almost 80% of our budget, and our customers include the Air Force major commands, who operate and maintain the full spectrum of Air Force weapon systems. We are a full-spectrum laboratory, responsible for planning and executing the Air Force's entire science and technology budget: basic research , applied research, and advanced technology development. The work is done at facilities all across the country (Wright-Patt, Kirtland, Brooks, Edwards, Eglin, Tyndall, Bolling, Hanscom, Rome).
The AFRL is made up of more than 6400 government people, which includes over 1500 military and over 4800 civilian personnel. We have about 3500 scientists and engineers, of which over 800 have PhDs.
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Budgets and staffing of research groups and facilities are relatively stable over time, as the Air Force regards its research capability as vital to the conduct of its overall mission, and takes a long view of its future technological needs.
Technology Transfer
The Air Force, like all of DOD, has a strong commitment to Tech Transfer, and like DOE and other agencies,has a wide latititude of contracting mechansims and ways of working together with private industry and academia. One of the primary motivations for working with the commercial sector is to enhance the capabilities of private industry so as to lower costs to the Air Force of the high-value manufactured items they need.
The AFRL operates Tech Connect, the main point of contact for tech transfer for the entire Air Force. It provides search and contact services and facilitation.
In addition, each operating location (not just labs) have their local point of contact or ORTA (Office for Research and Technology Application).
To contact TECH CONNECT
937-656-2530 Toll Free 1-800-203-6451 FAX (937) 656-2138
Web site -- http://tto.wpafb.af.mil/tto/techconn/index.htm
Wright Labs Overview
Wright Laboratories, located at Wright Patterson Air Force Base, Dayton OH, is oldest and largest of the Air Force research laboratories, with a history stretching back to 1917.
Wright Labs is headquarters for a number of Directorates (e.g. armament, avionics, flight dynamics, etc.).
Propulsion Directorate http://www.pr.wpafb.af.mil/
One of these, the Propulsion Directorate, has the highest relevance for utilities.
The Propulsion Directorate's work has many potential non-aerospace and commercial uses in:
- Materials and Materials Application
- Measurement and Sensing
- Modeling and Visualization
- Energy and Power
With an annual budget of about $150 Million, and about 300 mostly technical and scientific personnel, its technical divisions are:
Division - Office Symbol (Primary Site/Secondary Site)
- Power Division - AFRL/PRP (WP)
- Propulsion Sciences and Advanced Concepts Division - AFRL/PRS (Edwards/WP)
- Turbine Engine Division - AFRL/PRT (WP)
- Rocket Propulsion Division - AFRL/PRR (Edwards)
- Integration and Operations - AFRL/PRO (WPAFB/Edwards)
UFTO Principal Point of Contact:
Kristen Schario, 937-255-2131, mailto: scharika@wl.wpafb.af.mil
Power Division http://www.pr.wpafb.af.mil/divisions/prp/prp.html
The Power Division plans, formulates, manages and executes research,
exploratory and advanced development programs in energy conversion and
storage, and power generation, transmission, conversion, and thermal management.
This includes electrical, mechanical, thermal, and fluid power for aircraft,
missile, terrestrial, and special Air Force applications.
Covered in this report:
More Electric Aircraft (MEA)
- Power generation
- Power systems and distribution components
- Passive components - Capacitors
- Power electronics/motor drives
Ground Power
- Remote Small Scale (10-120 watts)
- Cryogenic Lightweight Deployable (1-4 MW)
Turbine Compressor Research Facility
Mechanical Testing of Electrical Machinery
Silicon Carbide High Power Electronics
Superconductors, Cryogenic Power Electronics
More Electric Aircraft (MEA)
Contact: Maj. Michael Marciniak, 937-255-6226, marcinma@wl.wpafb.af.mil
The Air Force has a major effort on the "More Electric Aircraft" (MEA), from which many "dual-use" applications arise. As with the more electric ship and tank, the PNGV hybrid/electric vehicle efforts share many common requirements and opportunities.
The goal of MEA is to replace hydraulic and pneumatic systems, which account for more than 1/2 of all downtime and failres of fighter aircraft, with electrical ones. A wide range of technologies are involved, including actuators, electronics cooling, motor/alternators, supercapacitors, batteries, power system controllers, and high power semiconductor devices.
The MEA will require a highly reliable, fault tolerant, autonomously controlled electrical power system to deliver high quality power to the aircraft's loads. Also, reliable high power density motors and motor drives ranging from a few horsepower to hundreds of horsepower will be required
Military aircraft have numerous subsystems powered by one or more sources of secondary power: hydraulic, pneumatic, electrical and mechanical. Secondary power is typically extracted from the main engines mechanically by a driven shaft and pneumatically by bleeding the compressor. Mechanical power is distributed to a gearbox to drive lubrication pumps, fuel pumps, hydraulic pumps and electrical generators. Pneumatic power typically drives air turbine motors for engine start systems and environmental control systems. Electrical power and hydraulic power are distributed throughout the aircraft for driving subsystems such as flight control actuators, landing gear brakes, utility actuators, avionics, and weapon systems.
Recent and projected advancements in aircraft electrical power system and component technologies have resulted in renewed interest in the MEA. For example, hydraulically driven actuators would be replaced by electric motor driven actuators, gearbox driven fuel and lubrication pumps would be replaced by electric motor driven pumps, and a pneumatically driven compressor for environmental control would be replaced by an electric motor driven compressor. Studies on two different military fighter aircraft have shown that the MEA concept provides significant reliability, maintainability and supportability payoff.
There are four major technical thrusts in the roadmap: (1) power generation,
(2) power systems and distribution components, (3) passive components,
and (4) power electronics/motor drives.
Power Generators -- Independent Power Units (IPU)
A High Reliability Generator was developed from a conventional 400 Hz Variable Speed Constant Frequency (VSCF) system to a dual output (270 VDC and 400 Hz) system capable of supporting the near-term MEA.
The Switched Reluctance Starter/Generator program developed the preliminary design for a 375 KW, 270 VDC switched reluctance starter/generator in which the electrical machine is integrated internally with an advanced gas turbine engine.
A smaller 250 KW unit was built and tested to demonstrate the critical technologies. The switched reluctance starter/generator system offers a robust, high temperature, fault tolerant solution for the environmental demands of the turbine engine and the performance demands for the MEA.
Feasibility is based upon recent advancements in power electronic component technologies, high temperature wire insulation, and high temperature, high strength magnetic materials. The power electronic inverter is essential to the system since it provides the means to excite and process power to and from the unit. An Electro-Magnetic Interference (EMI) filter will reduce unwanted frequency components.
These systems are directly applicable to ground applications. In fact, Allied Signal is the contractor, which no doubt contributes to their civilian microturbine program.
In another development, an internally integrated 375 KW Starter/Generator for large aircraft enginees will include the critical step of eliminating the engine gearbox and aircraft mounted accessory drive. Integration into the gas turbine engine is enabled by high strength, high
temperature permanent magnet materials (cobalt-iron) and reliable high temperature wire insulation.
Power Systems and Distribution Components
The MEA will need a highly reliable, fault tolerant, autonomously controlled electrical power system to deliver high quality power from the sources to the load.
There are several challenges in designing an electrical power system for a MEA. Total onboard power requirements will be much greater, ranging as high as 1-10 MW per aircraft. It adds substantial amount of high power dynamic motor loads which could impact power quality. Most of these loads will have a low input impedance "capacitive" EMI filter which could present an in-rush current problem. Some MEA loads such as flight control actuators could provide regenerative energy back to the power distribution system.
Most important, these loads are flight critical, and loss of power to these loads could result in the loss of the aircraft. Thus, the performance and integrity of the power distribution system becomes a critical network which links sources to loads.
Presently, the Air Force has two programs for power systems and distribution components for the MEA.
- Power Management and Distribution for More Electric Aircraft (MADMEL) program
- Remote Terminal utilizing 270 VDC Solid State Power Controller program.
Future programs include development of: (a) high current (>50 ampere) intelligent power controllers and contactors that provide control, protection, and status feedback. (b) smart, overcurrent, differential current, and ground fault protection systems, (c) arc detection circuits to trigger protection devices in the event of an arc. (d) highly reliable and rugged connectors and interconnect components.
Passive Components - Capacitors
-- Contact: Sandra Fries-Carr, 937-255-6016, carrsj@wl.wpafb.af.mil
State-of-the-art aircraft capacitors are considered to be the weakest link in power electronic systems. They are also large, heavy and lossy. This is a real concern for the MEA since 100s to 1000s of capacitors will be required for filtering and energy storage. The Air Force is pursuing several organic and inorganic capacitor technologies under contract that promise improvements in reliability, size, weight, and electrical and thermal performance.
Foster-Miller Corp. was awarded an SBIR contract to examine the application of PBZT polymer film for capacitors. This film demonstrated dielectric strengths as high as 100,000 Volts/Mil and low dissipation factor at high temperatures (up to 300*C). A follow-on SBIR contract to Foster-Miller further developed the PBZT film to make highly reliable, high energy density capacitors with operating temperatures to 300*C.
Westinghouse Science and Technology Center was under contract to develop and demonstrate high temperature (>200*C) AC and DC filter capacitors using a FPE polymer film from 3M Corporation. The capacitors were tested with a Variable Speed Constant Frequency (VSCF) generator system and demonstrated over 2000 hours of trouble free operation at 225*C.
Olean Advanced Products, Division of AVX Corporation is under contract to develop multilayer ceramic capacitors with increased operating temperature (up to 300*C) and reduced dissipation factor over a wide frequency and temperature range. Ceramic capacitors offer tremendous volumetric density compared to other capacitor technologies.
Wright Labs, in-house, is using low temperature RF sputtering to make very thin film ceramics (600 angstroms) which can be put directly on a circuit board.
Ultra high energy density pseudo capacitors have been developed, demonstrating energy densities over 11 Joules/gram and possibly as high as 30 J/g. An inexpensive device about the size of a quarter, weighing 6 grams, is rated at 5 farads at 5 volts. These are use in burst power and other aircraft and civilian applications, and can be stacked to the 1 KV level.
Diamond Thin Film Capacitors
The Air Force is conducting an in-house research program to investigate the possibility of using diamond-like carbon and polycrystalline diamond films as dielectric materials for capacitors. Diamond has the highest thermal conductivity of any material known and a very high dielectric strength, electrical resistivity and operating temperature capability. Wright Labs has made thin films using microwave plasma-enhanced chemical vapor deposition that have very stable performance over a wide temperature range. Capacitors continue to work well at 600 deg C, with a power density of 7 Joule/gram.
The Air Force has recently awarded several contracts to investigate other promising dielectric materials and construction techniques for capacitors. This includes silicon carbide, barium titanate, and multi-layer diamond capacitors.
Power Electronics and Motor Drives
-- Contact: Clarence Severt, 937-255-6235
Advancements in power semiconductor devices, capacitors, and integrated circuits for control has enabled high density, reliable power electronic and motor drive systems that are essential for the MEA. These include generators, battery chargers, DC to AC inverters, and DC to DC converters, and motor drives, which provide the interface between the electrical power system and the motor.
To date, the Air Force has focused on MOS Controlled Thyristor (MCT) switching device and the MCT driver. Future work will center on Application Specific Integrated Circuit (ASIC) technology for motor drive controls and the development of advanced drives for induction, permanent magnet, and switched reluctance motors.
In September 1986, the Air Force awarded a contract to the General Electric Corporate Research and Development Center to develop a high power MCT device. At that time, GE had only demonstrated a small MCT device capable of a few Amps and a 200 Volts. The objective of this contract was to develop and demonstrate a high power device (with several orders of magnitude increase in power handling capability) that would be applicable to aircraft power conditioning. The goal was to develop a 150 Ampere 900 Volt device capable of high speed operation (200 nanosecond turn-on and 1 microsecond turn-off capability), low forward voltage drop (1 Volt) and high temperature capability (>200*C junction temperature).
Later in the contract, an integrated circuit driver chip was developed that provides an interface between logic control signals and the gate of the MCT. This program was successful in meeting its goals, and several hundred first generation MCT devices and driver circuits were produced, with significant performance improvements as well as size and weight reductions when compared to bipolar junction transistor technology available at that time.
A second contract was awarded to GE to make the MCT an acceptable and preferred device for military weapon systems such as the MEA. This contract is focused on advanced hermetic packaging, radiation hardening, and symmetrical voltage blocking for AC applications. Also improvements to the MCT are being investigated which offer improvements in peak current turn-off capability and current density.
Remote Small Scale (10-120 watts)
-- Contact: Tom Lamp, 937-255-6235, xxxx@wl.wpafb.af.mil
The Air Force has over 80 remote sites in Alaska that need ultra high reliability power sources in the 10-30 watt range, for sensor systems, to 120 watts. Most are equipped with thermoelectric generators (TEG) that operate on propane, with some photovoltaic. The transportation costs run to $30-40 per pound of fuel, so the low efficiency of TEG, typically about 5%, is obviously a concern. Requirements are unattended operation, low health and safety risk to local population and Air Force personnel, and low environmental risk. Installation must be quick, by heliocopter drop-in. Weather conditions are very extreme.
But for the social outcry that would result, RTG's are the obvious best choice (radionuclear thermal generators--as used on space missions). Other mature technologies include batteries, fuel cells, wind and engines, none of which meet the objectives.
Other choices are Stirling, Thermionic, Thermophotovoltaic, and AMTEC, all of which are small scale heat-to-electricity conversion devices with higher efficiency than TEG.
Stirling is under development by NASA for slightly larger systems (350 watts), and DARPA is funding some work on TPV and AMTEC ( a 500 watt compact system for the Army).
For the Alaska sites, the conclusions are that AMTEC and Stirling are the best candidates. Work is underway to develop prototype systems, building on the work done for space power systems. Commercial applications could include gas metering, navigation stations, weather monitors, and cathodic protection.
Cryogenic Lightweight Deployable (1-4 MW)
-- Contact Jerry Beam, 937-255-6226
The Air Force needs lightweight deployable power plants to support,
as one example, ground based radar (GBR) systems. Conventional technology
and it's supporting infrastructure is larger and heavier than wanted, and
one of the Air Force's key goal is to reduce the "logistics tail" whenever
possible. A study showed that the conventional GBR plant with 5 semi-trailers
and 140 cubic meters in volume, could be reduced to 2 trailers by the use
of a superconducting cryogenic power generator. Since the radars already
need cryogenic support, this is not an additional requirement, and the
size and efficiency gains are significant. A prototype system will be tested
in 2000, and could be in the field by 2005.
-- Contact: Mark Reitz, 937-255-6802
The CRF is a major facility for conducting tests and evaluations of full scale multi stage and single shaft fans and compressors for gas turbine engines. Extending over four buildings, it is capable of 30,000 hp at speeds to 16,000 rpm, and 15,000 hp from 16 to 30,000 rpm. It can create steady-state and transient phenomena on full size test articles under conditions that are similar to those of actual operation. It has been used for many advanced turbine development programs to evaluate fans and core compressors.
Solar Turbines, Inc. is developing gas fired turbine engines for cogeneration
and industrial drive applications in industry, under a CRADA with DOE's
advanced turbine program. The compressor for this engine is now under test
at the CRF to identify any possible design deficiencies. This is the first
major commercial use of the CRF.
-- Contact John Leland, 937-255-2922
Cooling of power electronics is particularly important as systems become more compact and powerful. Anticipating cooling requirements up to 600 W/sq cm, a number of initiatives at the Lab include:
-- testing performance of heat pipes in aircraft-type environments, e.g. under acceleration and vibration. Contact Kirk Yerkes, 937-255-6241
-- integration of direct spray cooling into a 270 V 400 A single phase inverter, leading to a reduction in size of 10X. Direct immersion, jet impingement and flow boiling are also receiving attention. Contact Brian Donovan, 937-255-6241
-- Venturi flow cooling is another technique under consideration
-- Contact Tim Young
-- Characterization of soft magnetic materials at higher speeds and temperatures encountered in IPU's
-- Windage in generators can become a significant power loss (as much
as 30-40%) at high RPM due to viscous air losses.
Silicon Carbide High Power Electronics
-- Contact: Clarence Severt, 937-255-6235
Compared with silicon, Silicon Carbide semiconductors have 3 times the band gap, and a operating temperature range reaching 4-600 deg. C, compared with 125 deg. C for silicon. It also has higher breakdown strength, which can mean thinner devices. Also, increased circuit efficiencies can reduce heat loads as much as 5X.
The main obstacle to using SiC in power electronics is the difficulty in making it without defects. "Micropipes" form too easily as the material is built up by vapor deposition.
The Air Force program has focused on development of high quality semiconductor grade material, improving on both wafer size and defect rates, for an aggressive development effort for power electronic devices. They have set a goal to demonstrate a 100-amp 600-V 572 deg F SiC switch by the year 2002.
For the power industry, discussions were well along with EPRI last year on possible cofunding of several device programs, but EPRI backed out. No new initiatives have come forward since.
------press release by CREE Research, one of the key developers in this program--------
Cree Unveils New Product Offerings for Silicon Carbide Wafers 40% Reduction in Micropipe Densities on Silicon Carbide Material
(Durham, NC May 27, 1997) Cree Research Inc. [NASDAQ: CREE] today announced that it has made tremendous progress in its efforts to reduce micropipes within its silicon carbide (SiC) material. Cree will now offer its 4HN type SiC wafers with reduced micropipe densities (MPD) and graded to three categories. The low grade will have a maximum of 30 micropipes/cm2, which represents a reduction in MPD of 40%. A new select grade will be added, which will have a range of 31 to 100 micropipes/cm2. In addition to Cree's low and select grades, the standard grade will have a range of 101 to 200 micropipes/cm2. This represents a reduction in MPD of 50%.
Christer Ovren, Director of Silicon Carbide Device Development at Asea Brown Bovari (ABB), commented that "Cree continues to lead the world in making lower micropipe substrates available for the research and development of next generation devices. This latest advance is another step forward in maturing the manufacturing process for silicon carbide technology." ABB has purchased SiC wafers from Cree for a number of years.
These reduced micropipe densities are a result of Cree's continuous commercialization of its SiC material technology. Cree expects this technology breakthrough to enable SiC material for more applications and improve device performance of existing applications. North Carolina based Cree Research, Inc. is the world leader in the development of silicon carbide-based semiconductors which have potential advantages in certain optoelectronic, RF and microwave, power, and high temperature applications. Cree owns outright or licenses exclusively 40 patents related to its process and device technology.
Superconductors, Cryogenic Power Electronics
-- Contact: Charles Oberly, 937-255-4814
As noted above, cryogenic systems can have dramatically improved efficiency, size reduction, and performance as compared with standard counterparts. Power conversion efficiency of an alternator/motor, for example, can reach 99%, including the refrigeration needed, compared with 92% for conventional copper based components. Wright Lab is developing both the high temperature SC materials and designs for generators, motors, actuators and power transmission lines.
Perhaps less well recognized, cryogenic cooling (i.e. to liquid Nitrogen
temperatures) dramatically improve the performance of standard commercial
solid state electronic components. Devices such as MOSFETS exhibit significantly
reduced heating and faster switching. Ceramic capacitors have lower losses
and higher capacitance when cooled.
-- Contact Steve Vukson 937-255-7770, Dick Marsh
Aircraft battery systems are a major concern, particularly in regard to weight, reliability and maintenance. For example, vented NiCd battery maintenance costs are $3000/yr for each battery, amounting to $1/2 billion over a 20 year period. Wright Labs has developed a maintenance-free sealed NiCd cell technology, which uses low cost separator materials and which they've married with a microprocessor-based smart charger. These new systems will eliminate all scheduled maintenance costs, and also to save another $1/2 billion by reducing flight mission interruptions.
The bulk of the Lab's battery program budget is devoted to advanced lithium polymer technology, doing work in molecular engineering in cooperations with Cornell, Berkeley and other academic institutions. The program has demonstrated prototype rechargeable lithium batteries with energy densities above 80 W-Hr/kg.
Thermal batteries are a special class of one-shot primary batteries
used in weapons systems to deliver a large burst of power, very reliably,
after waiting as long as one or two decades. Sandia National Lab is also
well versed in this technology. ( --Would this have a useful role to play
in nuclear power plant emergency systems?)
-- Contact Bob Wright, 937-255-4230, wrightrl@wl.wpafb.af.mil
This separate branch provides field support, development and advanced technology research. Their services to the Air Force include comprehensive testing facilities, bearing systems development, lubricant testing, magnetic bearings, etc.
For lubricants, increasing operating temperatures and longevity of lubricants are ever present goals. Some state-of-the-art compounds (polyphenyl ethers) have higher temperature capability but cannot be used below 40 deg. F, an obvious limitation for tactical systems. Others (perfluoro ethers) perform extremely well over a wide temperature range, but degrade quickly leading to corrosion. The overall paradigm is shifting from use of bulk oils to vapor phase lubricants, soft magnetic materials, and expendable coatings, although conventional ester lubricants are still foreseen to be the mainstay of aviation lubrication for some time to come. Meanwhile, integration of on-engine (on-line) oil condition diagnostics is an important theme. Off-line diagnostics are effective, but not optimal. This is a vital issue, as lubricant systems are implicated in 1.5 aircraft losses per year.
Magnetic Bearings -- The Lab has a major development program, foreseeing big opportunities in engines to do active rotor dynamics control, increase temperature, do active control of compressor stability and blade tip clearance, and to have less logistics and better real time diagnostics.
On-line spectrometer -- The Lab is sponsoring development of a very small infrared spectrometer for on-line oil analysis. The device measures the condition of the basestock and additives, and can detect the presence of unwanted contaminants, such as water, fuel, glycol, or wrong oil type.
"RULER" -- Remaining Useful Life Evaluation Routine -- off-line test system measures antioxidant levels in lubricants quickly and accurately by "voltammetric analysis". Results enable operators to determine remaining useful life of lubricants in less that a minute. RULER System consists of an "RULER" -- Remaining Useful Life Evaluation Routine -- off-line test system measures antioxidant levels in lubricants quickly and accurately by "voltammetric analysis". Results enable operators to determine remaining useful life of lubricants in less that a minute. RULER System consists of an instrument with probe, R-DAS (RULER Data Acquistion Software) pre-installed on a desktop or laptop computer. RULER System cost about $15,000. Proprietary solvents are used in the tests.
The RULER was originally developed at the University of Dayton Research Institute for Wright-Patterson Labs, for quick tests on aircraft oils between missions. It is manufactured by Fluitec Ltd., based in Dayton, OH with operations in Brussels. RULER customers cover a large range of industries world wide in oil, additive, manufacturing plants, power generation, aerospace and fleets. It's applied to turbine, hydraulic, synthetic, working fluid, IC engine, and even biodegradable oils.
Contact: Lawrence Contreras, Fluitec, 937-223-8602, lcontrerasjr@juno.com