Micro Turbine Generator Program

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Abstract
A number of micro turbines generators have recently
been announced as currently commercially available for
sale to customers, such as end users, utilities, and energy
service providers.
Manufacturers and others are reporting certain
performance capabilities of the turbines; however, no
consistent third-party independent testing as been done to
confirm or discredit such performance claims. The
purpose of this project is to provide such an independent,
third party testing assessment.
This project purchased, installed, operated and tested
micro turbines to assess their performance. Data was
collected electronically and manually. This project
generally reports the performance testing program.
The paper will reveal the relative maturity of the
technology overall and look forward to the needs of the
“next generation” of microturbines.
1 Overview
There are several manufacturers of Micro turbine
generators (MTGs) announcing their products as currently
commercially available. Their potential customers are
end-users, utilities, and energy service providers.
The chart shows some of the MTG Manufacturers and
current MTG operating features.
To be competitive with existing technology, most
MTG manufacturers rely on enhanced reliability and
lower maintenance costs. MTG manufacturers expect to
achieve greater reliability and lower costs by using fewer
moving parts and lower manufacturing costs.
Manufacturers thus expect economy of manufacturing of
microturbines to replace economics of scale for central
plants.
For MTGs to be competitive in the marketplace,
minimum customers’ expectations are:

40,000 hour “wheel life”

Heat rate of 12,000 to 16,000 BTU/kWh

Good part load performance

Emissions < 9ppm

Noise < 70 dB

Cheap and easy installation and maintenance
There is a tremendous potential market for MTGs if the
MTG manufacturers can make their products competitive
with the other forms of energy available at the meter.
Using turbo-charger technology, the cost of producing an
MTG can become lower and lower -- depending on the
manufacturer’s expertise in economy of manufacturing.
This is especially true if the manufacturer can use a
casting process versus a machined process. The MTG
manufacturers realize that with an adequate volume of
sales, relying on low cost economics of manufacturing,
MTGs have a stronger potential to compete well at the
meter with large central power plants. Additionally, on
site power maybe able to pick off other markets within
niches to provide for future product development.
MTGs are intended to provide the energy industry with
dispersed power generation assets that may be located
close to the loads they serve. For utilities, interest in
MTGs is based on deferred central power plant
construction, deferred distribution line upgrades, and
improved reliability. End use customers may view MTGs
as an alternative to other small generators, an
environmentally acceptable power generation device, and
a reliability improvement mechanism.
There is speculation that MTGs may be an integral part
of the future utility infrastructure. In such as speculation,
numerous, small generators are scattered throughout a
utility's traditional distribution network working in
parallel with central power plants. Some believe this will
emulate what personal computers and local area networks
did by working in parallel to mainframes.
MTG manufacturers and others are reporting certain
performance capabilities of the turbines; however, no
consistent, independent, third party independent testing
has been done to confirm or discredit such performance
claims.
However, MTGs will only be considered if they
perform acceptably and meet customers’ requirements for
power quality, reliability, availability, environmental
considerations, cost effectiveness, usability and system
efficiency.
As a part of the overall testing program, MTGs are
purchased, installed, operated and tested to assess their
performance. Data was collected electronically and
manually.
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Ultimately results, as applicable for each unit, include
the following performance measures:

Starts/stops

Overall unit efficiency

Net power output

Operability

Emissions level monitoring

Power quality monitoring

Endurance testing
2 Technical Background
MTGs are small, high-speed power plants that usually
include the turbine, compressor, generator, and power
electronics to deliver the power to the grid. These small
power plants typically operate on natural gas. Future units
may have the potential to use lower energy fuels such as
gas produced from landfill or digester gas.
Figure 1. MTG Components
MTGs have a high-speed gas turbine engine driving an
integral electrical generator that produces 20-100 kW
power while operating at a high speed, generally in the
range of 50,000-120,000 rpm. Electric power is produced
in the 10,000s of Hz, converted to high voltage DC, and
then inverted back to 60 Hz, 480 VAC by an inverter.
Most of MTG engine designs typically have one or
several power producing sections, which include the
turbine, compressor, and generator on a single shaft.
During engine operation, engine air is drawn into the
unit and passes through the recuperator where temperature
is increased by hot exhaust gas. The air flows into the
combustor where it is mixed with fuel, ignited and burned.
The ignitor is used only during startup, and then the flame
is self-sustaining.
The combusted gas passes through the turbine nozzle
and turbine wheel, converting thermal energy of the hot
expanding gases to rotating mechanical energy of the
turbine. The turbine drives the compressor and generator.
The gas exhausting from the turbine is directed back
through the recuperator, and then out the stack.
3 MTG Testing Program
This MTG test program is expected to provide
valuable insight, both qualitative and quantitative, into the
installation, performance and maintenance requirements
of units presently available to the market. Test results are
based on actual operating conditions at the test site in
Irvine, California. In addition to the results and
experiences derived from installing and operating these
units, performance data are collected to trend and profile
operating characteristics via a Data Acquisition System
and manually.
3.1 Data Acquisition System (DAS)
The Data Acquisition System (DAS) installed at the
MTG test site provides interval sampling of MTGs in
operation. Raw data is collected in 5-minute intervals
from various measurement sensors that feed a datalogger
with either pulse or analog signals. The raw data is
collected nightly, and processed once a month.
Each MTG is retrofitted with sensors at various
locations. Additionally, environmental parameters are
collected for the entire site. Data parameters collected are
described in Table 1.
Table 1. MTG DAS Monitoring Parameters
Parameter Instrument
Electrical Energy
Produced
3-phase electrical meter
with pulse output module
Fuel Consumed (Gas
Flow)
Gas flow meter
Fuel Temperature RTD
Gas Pressure Pressure transducer
Water Flow* Water flow meter
Boiler Air
Temperature – Inlet
and Outlet*
Thermocouple
Water Temperature –
Inlet and Outlet*
Resistance Thermal
Detector (RTD)
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Parameter Instrument
Power Quality
Snapshots
BMI 7100 and BMI
8010 power quality
meters
Ambient Temperature Temperature Probe
Relative Humidity Solid State IC
Barometric Pressure Barometric pressure
transducer
* Only MTGs with boilers are instrumented with these
sensors
3.2 Test Procedures
To fully evaluate the MTGs, a series of tests were
developed. Testing of MTGs is categorized into three
phases:

Installation and Startup

Operation and Maintenance

Performance
3.3 Installation and Startup
Each MTG delivered to the test site is inspected and
noted to include operating instructions, repair parts or a
recommended spare parts list, consumable supplies,
trouble-shooting and maintenance procedures/guides, and
a drawings and diagrams to sufficient to support
maintenance
Once installed, the MTGs start and stop capabilities are
tested. Units are expected to withstand the wear of daily
starts and stops. Operators at the test site manually shut
down the units several times per month. At other times,
the units shut down (e.g. loss of grid) and/or were
manually restarted.
Figure 2. Bowman MTGs
Bowman 60 kW rated MTG (left) and a Bowman 35
kW rated MTG (right) are shown installed at test
location.
4 Machine Performance Test Criteria
4.1 Endurance
For the test program, MTGs will be operated for as
long as practicable at nominal load. Daily operating
parameters: fuel flow, ambient air pressure, temperature
and humidity, energy (kWh), operating temperatures and
pressures will be recorded. Critical MTG parameters will
be recorded with the intent of correlating degradation with
factors other than wear and tear.
4.2 Transient Response
MTGs should be able to respond adequately to load
changes. Units that are not capable of isolated bus
operation will operate in parallel with the system grid.
Changes in system load will be picked up by the grid and
not by MTG units. Load changes on these MTG units will
be accomplished by manually setting load using the
control system.
4.3 Harmonic Distortion
The power output will be measured with a BMI or
equivalent recorder, which will measure total harmonic
distortion (THD). The BMI will also be used to determine
the power factor of the fully loaded unit during the
endurance test. The measured power factor will be used to
Proceedings of the 33rd Hawaii International Conference on System Sciences - 2000
0-7695-0493-0/00 $10.00 © 2000 IEEE 3
verify that the package achieves rated output when
connected to the utility grid.
4.4 Noise Measurement
Ambient noise levels will be measured using a
handheld noise meter. Each unit will be operated
independently to acquire the noise measurements during
operations.
4.5 Emissions Measurement
For each MTG type tested, one certified test will be
conducted to determine compliance with South Coast Air
Quality Management District Rule 2005 for NOx
emissions. Additionally, periodic measurements with
available handheld equipment would be made to
determine trends and any condition of degradation that
may occur with operating hours.
4.6 Peak Load Gross and Net
Peak load gross and net measurements will be taken
with a BMI meter or equivalent recorder that measures
power. For units without compressors, or compressors that
are externally powered, the net output must be determined
by subtracting the external power requirements to sustain
MTG operation. Results of this test will yield performance
characteristics such as efficiency, heat rate, fuel
consumption and operating hours. Comparisons will be
made to manufacturer specifications.