| Regenerative
Power and Motion |
Background & Perspective
RPM's cleantech DC electric power motor, generator, and flywheel electric power storage technologies could enable products to solve global energy, pollution, and transportation problems. Able to share a common DC power bus, they are uniquely compatible with each other, and with solar power. They introduce a new integration of brushless coreless motor technology and advanced high-frequency switch-mode power electronics.
Our motor and generator technology has been proven by working prototypes. RPM's generator is the easiest to implement, compared to our motor and flywheel. Our flywheel is the most challenging, and a complete flywheel system in an evacuated self-balanced enclosure not yet completed, although we have built and tested 2 flywheel battery prototypes.
Our brushless coreless regenerative DC motor affords practical advantages over all others for: High power/weight high-speed drive, where it's now produced in high volumes to propel unmanned drone aircraft, powered by photovoltaics on top facing aircraft surfaces; high-efficiency servomechanisms that can be sealed with no overheating, for use in deep ocean submarine robotics; factory automation; and countless varied applications.
It is scalable: Its stacked rotor and stator disk configuration can accommodate a wide power and speed range, by the number of disks selected. So it does not require a large parts inventory for different power ratings as do conventional motors.
Its motor assembly is interchangeable with our generator assembly -- only its electronics is different.
A version in which the motor's 8 conductors are connected to its DC power interface through a non-rotating tubular shaft, to enable a motor-wheel for advanced practical low-cost electric vehicles (EVs). These EVs would have no fuel tank, no fuel-burning engine, no clutch, no drive shaft, no differential gears, no universal joint, etc. Instead they would have motor-wheels that can provide up to maximum torque at all speeds, regenerative braking that charges onboard batteries, an electronic differential in its signal processing costing only a few cents, etc. This EV does not have costly and heavy mechanisms needing too much maintenance, that it could replace with a safer, low-cost cleantech option. For more details, please see
http://flywheel.esmartbiz.com/humpwr.htm
RPM's proven advanced motor technology can also afford substantial advantages over conventional motors, to countless motion control applications. They include robotics, food processing automation, general production automation, etc.
Our proven broad-speed-range generator can, with adequate resources, be mass produced and profitably marketed within a few months. Its power electronics is the only part of it that differs from our motors. can efficiently convert mechanical input power to DC electric power, producing regulated current and voltage, and harvesting maximum wind turbine power, over a speed range exceeding 10-to-1. This unique feature can more than double the yield from all existing wind turbines, compared to conventional generators now widely used. Vast wind power growth would be facilitated by it.
RPM's webpage
http://flywheel.esmartbiz.com/RPMpower.htm
has a detailed description that explains how our generator can provide over 2x the yield from any wind turbine, compared to others that are now widely used.
By using different signal processing in its electronics, our generator can produce maximum power at variable shaft speed, with selectable torque, like exercise equipment in a health club. That version would extend "fitness EV" range.
RPM's flywheel batteries can be a very important growth-enabling component of building-integral solar and wind power systems, where superior power storage capability (near-zero-loss, high reliability, safe, no maintenance) could help to create a $200 billion yearly global renewable-power/UPS market. Our flywheel batteries can also enable solar/wind powered electric highways for safe, low-cost, high-performance electric vehicles.
RPM plans to produce and market power storage systems, to meet dependable and environmentally responsible building power demands of a US construction industry that exceeds $750 billion yearly and global construction that could amount to far more. We especially want to serve pioneers at the forefront of emerging high-growth distributed on-site renewable power systems, who share our vision.
Most existing UPS options have lead-acid batteries and diesel generators. They are not viable, for most building owners and tenants, because: Site, maintenance, noise, fumes, and fuel supply needs of fuel-burning engines, that drive power generators, is a costly nuisance. Troublesome lead-acid batteries, a charger, switchgear, and 60-Hz inverter are also usually needed. Existing flywheel batteries can't provide long-term power. Most of those developed globally, by 50 or so promoters, provide only short-term power (10-60 seconds) to start diesel generators. They sustain unacceptably high internal idling losses (up to 3-kw); with self-discharge (30 minutes for most, possibly 60 hours for only one) far worse than lead-acid batteries. Their reliability, maintenance and safety are problematic.
RPM's Flywheel Battery Prototype Development
A prototype version affords a practical way to demonstrate key performance features of planned RPM flywheel battery production versions. It is a minimum system without a vacuum enclosure, with its design based upon parts like Neodymium-Iron-Boron magnets and spiral-strand Litz wire, that were purchased even before CAD/CAE work could be finalized; and drawings for custom machined parts completed. Nevertheless, it affords tangible proof of key performance features, without the substantial expenses for molds and manufacturing equipment needed for production versions.
The image below shows basic prototype flywheel assembly physical
features. System electronics is constructed and tested, but not yet integrated
with this assembly. Not shown here are circuit 
boards
for its magnetic bearings, screwed to the top and bottom decks; nor their signal input connections to axial and radial
position and velocity sensors; nor leads to axial and radial servo coils; nor
its stator windings; nor the power interface
electronics in its EMI-shield box, its system status display monitors, and its cable to this assembly.
A photo of this flywheel is shown in RPM's webpage
http://flywheel.esmartbiz.com/RPMgenerator.htm
Production versions of the flywheel battery will be fabricated using some different processes and materials; and will have a flywheel
assembly resembling this prototype, with minor basic differences, within
a vacuum enclosure.
A space satellite version, to provide both power storage and spacecraft
attitude control, would require a minimum of 2 systems resembling this image. No
vacuum enclosure would be needed. However, its magnetic bearing axial magnets
would need to be larger, to facilitate larger pole gaps, because the rotor needs
to settle at a slightly higher axial position relative to the stator for ground
tests, compared to its weightless relative axial position during space
operation. And precision radial force transducers would be needed, for accurate
precession torque control, in addition to their rotor centering function.
Radial pole gaps also need to be larger than their terrestrial counterpart, to
allow for slight axis tilt during precession maneuvers. More
comprehensive explanations of space version RPM flywheels can be found in
Fradella's US Patent 6794777 and his UPS+CMG webpage. It offers extraordinary advantages over existing
and very troublesome chemical
battery UPS, plus jet thrusters and/or momentum wheels for attitude control.
A lower cost flywheel is shown in the image below. Some of its parts are rendered semi-transparent, to reveal main components otherwise hidden by them. Its rotor is levitated by axially magnetized ring magnets, shown in red near the bottom. One is fixed to a stator support. It repels a like magnet fixed to the rotor, thus providing a stable lift force. The rotor is centered by top and bottom ceramic ball bearings.
This flywheel is described in Fradella's patent pending for a "Low-cost
minimal-loss flywheel battery". A photo of a prototype we built is shown in
RPM's webpage
http://flywheel.esmartbiz.com/RPMgenerator.htm
Our experience with these 2 prototypes indicates that the 2nd version, shown at left, has far fewer parts than the 1st version, does not need the 1st versions' critical magnetic bearing 10 position sensors and 10 rate sensors and their servo loop requirement, and does not need startup power to position the rotor.
However, its ball bearings impose rotor spin speed and size limits. And rotor dynamic balance is critical to bearing service lifetime. Consequently, its ball bearings impose a maximum practical energy storage limit of 1 to 3 kilo-watt-hours for this lower cost version flywheel battery.
Its ball bearings also would limit lifetime of this flywheel battery.
To avoid need for paralleling a very large number of flywheel batteries, to afford 50 or so times its energy storage and power limits, RPM is developing a 3rd version flywheel battery, that does not need ball bearings, and is not as expensive to produce as the 1st version. With only 1 position sensor and 1 axial servo loop that does not need to overcome such large and very unstable magnetic forces as the 1st version, it's startup power for its top and bottom axial electromagnets, to axially position the servo to a height where only a few watts is needed by all its electronics to maintain correct rotor height, is a small fraction of the 1st version's. Clearly, the 2 prototypes we built and tested provided a great learning experience for us.
Market research, based mainly on potential customer inquiries, indicates that most future applications will be as better alternatives to existing power storage for distributed building-integral solar and wind power.
Safe flywheel installations will be a very important component of RPM's business. Underground flywheel placement is shown here, with the flywheel in its vacuum enclosure hanging from 2-axis gimbals (for long term self-leveling), within a permeable housing cylinder surrounded by sand, shredded tires or carpets, or soil. An electric signal and power cable, between the flywheel assembly and a floor level electronics enclosure, is not shown here.
Note that underground placement would not be practical without the zero maintenance expected for the RPM flywheel. Zero maintenance is a critical requirement for remote locations, such as off-grid solar/wind powered cell phone towers, and is crucial for spacecraft UPS+CMG.
RPM's Brushless Regenerative Motor
Although Fradella got purchase orders for this proprietary (covered by his US Patents 4085355 and 4520300) regenerative motion control system, from clients who saw its prototype's unique performance, he was unable to finance manufacturing operations. The demonstration motor prototype is shown in the photos below.
The first photo shows: (left) a 48vdc battery pack; (above) a 115vac wall outlet to a battery charger in the electronics enclosure; (center) the electronics enclosure, mostly housing pulse-width-modulation motor control similar to the RPM flywheel power interface, rear connectors to the motor and battery, and front battery voltage and current meters; (right) the motor, mounted in a frame for demo portability; and (front) the system's speed, braking, forward/reverse control box.
The second photo shows the motor's disassembled axial-field rotor and stator disks, frame, shaft in ball bearings, and connector cable. Its main advantages over conventional iron-core motors are: No hysteresis and eddy losses, so it has far higher drive and regeneration efficiencies (up to 99%); no cogging torque; no brushes; can be assembled with varying number of disks, to get flexible power rating with same parts (for lower manufacturing cost); provides inherent position and speed signals for servo use; does not need air vents for cooling; etc.
RPM's Broad-speed-range Generator
This generator can produce regulated DC current and voltage with 2x to 10x the electric power energy yield, with far better power quality, than most existing generators used in "wind farms" that augment grid power or small generators for charging batteries. RPM's generator is intended mainly for distributed on-site sustainable solar/wind installations with flywheel battery backup. All elements of these systems are uniquely compatible with each other. By adding a 3-phase power inverter, the RPM generator offers a far better option for augmenting grid power.
The photo below shows our lab test setup for a vertical axis generator now coupled to vertical axis wind turbines in field tests.
RPM's "fitness-EV"
Special versions of the RPM motor (regenerative motor-in-wheel) and generator (user selectable effort level) would enable a very unique ultra-light-weight electric vehicle (EV) powered by onboard chemical batteries, photo-voltaics (PV), and optional recumbent cycle human pedal power. PV and pedal power enable long range driving without discharging onboard batteries. The batteries can be charged by an onboard charger from garage power outlets during off-peak hours. They enable high speed and acceleration, and regenerative braking from RPM's unique motor-in-wheel. An image from our 3D CAD model is shown below.
RPM’s startup team
Markets we won't pursue
Onboard flywheel batteries for electric vehicles: Explosion hazard of flywheels involved in EV collisions is unacceptable, with any practical flywheel enclosures, gimbals, shock mounts, etc. Moreover, frequent onboard vehicle shaking would cause unacceptably high losses in the flywheel battery's magnetic bearings.
However, we would be especially well positioned to manufacture and market ultra-efficient, regenerative propulsion systems, for hybrid EVs, or (far better) EVs that are provided in-transit power on electric highways. Technical obstacles to providing such an infrastructure are minimal; with all EV costs substantially lower than fuel-engine vehicles, and profitable infrastructure operation. Environmental benefits would be profound. But such projects are capital-intensive, and susceptible to bureaucratic road-blocks. At some future date, we may consider a joint use proposal to a toll-highway operator or public transit authority operating an ultra light electric rail system.
Vacuum pumps, disk drives, or any other applications that would divert our early capital resources: However, our m/g and magnetic bearing technologies could be very successful for such applications. At this point, marketing our m/g and magnetic bearing is a fall-back strategy we don't intend to pursue, except in the event of unlikely circumstances. Customers in those fields may want to explore license agreements, or may want RPM to develop products for them, based upon our proprietary technology.
Current RPM assets & resources
If you have questions, comments or suggestions, email me: fradella@earthlink.net
RPM Overview
RPM Resources
Comparisons of
RPM's Technology vs. Other Flywheels
Flywheel Tutorial
Dual-mode Electric Vehicles
On-site Solar & Wind
Power
Flywheel Facts and
Fallacies
Urban EV with Onboard
Batteries, Charger, PV, Regenerative Motor, Pedals
Future options for
clean and sustainable electric power
Technology: Public/business
policy
Solar and Wind
Power Benefit/Cost Estimates
Satellite UPS+CMG
and UPS for space missions: Launch/orbit dynamics and RPM's advantages
RPM broad-speed-range generator