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                                           Technical Overview

System Overview
Active Power’s CleanSource2 is a flywheel energy storage system that stores energy in the form of a rotating
mass. This energy is immediately convertible to useful power when needed.

The CleanSource2 is configured as a two terminal DC power storage system and is a functional replacement or
supplement for a bank of chemical batteries used with 3 phase UPS systems. Like a chemical battery bank, it
receives recharge and float power from the two terminal UPS DC bus and returns power to the same DC bus
whenever the bus voltage droops below a programmable threshold level.

The heart of the CleanSource2 is an 14” high, 32” in diameter integrated motor/generator/flywheel system that
is capable of storing and delivering up to 250kW of DC power to the DC bus of a UPS. The flywheel stores
energy as angular momentum in a single piece forged 4340 steel rotor rotating in a rough vacuum. The motor,
generator and storage functions are all performed by the same stator and rotor structure. There are no
permanent magnets used, nor are there coils or magnets on the rotor. No brushes are employed. A magnetic
bearing that is integral with the motor/generator field coil structure supports most of the rotor weight. This
enables the mechanical bearings to be optimally loaded and greatly extends bearing life. An auxiliary AC
protected service connection is required.

When the UPS battery charger is connected and turned on, the controller begins to draw power from the
charger to accelerate the rotor. When the flywheel reaches its "fully charged" speed, it enters a mode
comparable to a chemical battery's "float" state, in which a small amount of power is drawn from the UPS
battery charger to maintain a constant RPM.

Once the flywheel is above its minimum discharge speed (about 1/2 of its "fully charged" speed), it is capable
of supporting the DC bus in case of a main power interruption. Whenever the controller (using an isolated
CVR) senses that the DC bus voltage has fallen below a preset minimum, motoring is disabled and closed loop
field control is used to raise the generator output voltage so that the bi-directional converter maintains the DC
bus at a constant voltage, independent of rotor speed. When the power to the UPS input rectifier is restored
either by a engine generator or utility power the UPS rectifier brings the DC bus back to its normal value and
the flywheel automatically resumes charging.

Site Selection and Preparation
Each CleanSource2 system has dimensions of 42”w x 34”d x 78”h, or a footprint of 10 square feet. The site
selected must also provide at least 36” of open floor space in front of the CleanSource2. No side or rear access
is required. Because concrete anchors are required to secure the unit to the floor, the corners of the frame must
be at least 12” away from the edge of the concrete slab. It is desirable to provide additional clearance when
practical. Access must be adequate to allow the unit to be handled with a forklift, pallet jack or overhead crane.
Ceiling height should be at least 8 ft. The site should be clean, dry and reasonably dust-free. Ambient
temperature must be between -20C and 40C (-4F and 104F) with a 0 C limit only for starting the system,
as it will keep itself warm when in operation even if ambient is as low as -20 C.

The CleanSource2 is shipped with bearing unloaders installed to relieve the bearings of transient forces that
may be encountered during shipping and handling. Prior to motoring, these bearing unloaders must be
removed and the bearing cartridges properly seated and aligned. An authorized Active Power representative
must perform this operation.
Vacuum System
The CleanSource2 is designed to operate in a rough vacuum at pressures below 50mTorr. This greatly reduces
levels of drag, vibration and noise resulting in low standby losses and low dBA measurement.
The vacuum inside the flywheel housing is maintained by a vacuum roughing pump that is capable of many
years of continuous service with a minimum of maintenance.

A vacuum gauge is installed on the top of each flywheel module and is interfaced to the CleanSource2 control
electronics. Upon sensing unacceptable vacuum limits the system will enter a wait state until the proper
vacuum level is restored.

Computer Monitoring
A built-in LCD display and operator panel is standard on each CleanSource2 system. This includes an audible
alarm and capability to scroll through up to 1000 log records. This display also provides real-time monitoring
and display of over 25 system parameters updated three times per second. Remote monitoring can be
supported with an optional modem for dial-up access, network connection or via the RS-232 interface built-in
to every CleanSource2 system.

This RS-232 interface provides telemetry that can be monitored on a user supplied IBM compatible PC using a
software package called CSView from Active Power. CSView is a data-monitoring package that tracks over
twenty-five variables on the CleanSource2 system in real time and displays them on a PC. This gives the user
access to a wide range of data, including rotor speed, temperatures of various components, and system currents
and voltages. CSView can also be used for remote monitoring over a network connection or via modem.

All parameters displayed in CSView are normally lettered in green. If the parameter reaches a marginal value,
the text in that box will turn yellow. If it reaches a critical value, it will turn red, and information about that
parameter and the controller’s reaction to it will usually appear in the event log. Optional remote notification
can also be enabled with CSView dialing preset beeper or phone numbers. An event code is transmitted to the
beepers indicating the type of alarm that occurred.

Each parameter is displayed as a digital value in a small data box that can be expanded into a bar chart and
trend graph by clicking on two small squares in the upper left corner of the box. The bar chart shows
horizontal yellow and red lines at the setpoints that will cause the display to turn yellow or red

An event log text window at the top of the CSView screen displays plain English status messages. In the event
of an unusual occurrence such as a shutdown, error messages appear here. Discharges and self-tests are also
announced in this window.

CSView automatically logs data to disk in a comma-delimited format compatible with Microsoft Excel and
most other popular spreadsheets.

CleanSource2 also stores up to 4,000 system event notices on board for history tracking. This is especially
useful when needing further information on an event or when requiring further diagnostics.

Routine Operation
Under routine operating conditions, the CleanSource2 will idle at 7700 RPM and maintain readiness to support
the UPS DC bus whenever a sag or outage causes the UPS DC power supply to shut down or lose regulation.
During standby condition, the CleanSource2 system will use about 2.5 kW of power per wheel. This standby
loss is independent of delivered power from the system.

As described above, the flywheel’s internal controller monitors a wide range of parameters and provides early
warning of impending maintenance needs, and in the event of serious diversions from normal operating
parameters, the controller will execute a controlled shutdown and inform CSView of its status. Routine
operation can be verified by glancing at the CSView screen to see if any fields are yellow or red.

Unlike the bank of chemical batteries it replaces, the CleanSource2 requires very little routine maintenance.
There are no chemicals to corrode contacts, and no need for water addition. The degree of charge and state of
system health are always shown on the CSView display. Nonetheless, like all high-power equipment, the
CleanSource2 does require some maintenance:

1. The air filter on the bottom of the enclosure should be changed at 2 to 3 month intervals in normal
   environments, or more often in dusty or dirty conditions.
2. The vacuum pump requires a periodic oil change. This can be performed in only a few minutes.
3.   Bearings should be replaced when CSView reports telltale vibrations indicating significant bearing wear.
     The CleanSource2 vibration sensors and software provide warning of bearing problems. Since the
     bearings are mounted in cartridges that can be removed without flywheel disassembly, bearing
     replacement is a quick, simple and inexpensive procedure.

                                          11525 Stonehollow Drive
                                            Austin, Texas 78758
                                             Tel: 512-836-6464
                                             Fax: 512-836-4511

For more information on the revolutionary CleanSource2 flywheel energy storage system, please call
Active Power or visit our website for the name of a representative in your area.


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