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Discussion of
Low Load “Diesel” Options
Alan Fetters
Project Manager – Rural Energy
Alaska Energy Authority
Within the Session
Diesel Issues in Wind-Diesel Systems
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Low Load “Diesel Generator” Options
Overview
• Diesel Engine & Generator Sizing Considerations
– Fuel efficiency curves
– Rotating generator end parameters
– Manufacturer’s recommended minimum loading
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Low Load Diesel Options
– Standard 1200 or 1800 rpm generator end with constant speed
transmission and variable speed propulsion diesel engine
• CVT Corp
• Marsh Creek LLC & Flux Drive
– Electronic inverter with power factor correction, DC generator end,
and variable speed propulsion diesel engine
• Cummins Permanent magnet Alternator and Power Conditioning System
• Energetic Drives
– Run what ya brung
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Potential Low Load Options that are
not Represnted
• Liquid Fueled Capstone Micro –AVEC tested these
a decade ago
• Power Corp Low Load Diesel – Recently acquired
by ABB
• Flywheel energy storage
• Battery storage
• Tecogen - They specialize in natural gas but the
technology is directly applicable to diesel
• Synchronous condenser, synchronous capacitor
or synchronous compensator for kVAR support
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Fuel Efficiency Curves
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Fuel Efficiency Curves
(continued)
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Fuel Efficiency Curves
(continued)
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Rotating Generator End Parameters
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Rotating Generator End Parameters
(continued)
This Figure is a reactive capability
chart for a typical generator end. A
load point within this area defines
the:
· Active Power
· Reactive Power
· Apparent Power
· Current
· Power Factor
· Excitation
The heavy dark line, with points
labeled:
m-n-p-s-q-u-t
indicates absolute limits that are
tolerated in a machine. Generators
are rated within these limits.
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Manufacturer Recommended Minimum Loading
This is an excerpt from the Cummins Power Generation
Application Engineering T-30: Liquid-Cooled Generator Set
Application Manual April 2012
Minimum Genset Load/Capacity
Running a generator set under light load can lead to engine
damage and reduced generator set reliability. Cummins Power
Generation does not recommend running generator sets at less
than 30 percent of rated load -- this is the default setting in
GenSize. Load banks should be used to supplement the regular
loads when loading falls below the recommended value. A
generator set should not run at less than 10 percent of rated load
for any extended period.
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Manufacturer Recommended Minimum Loading
(continued)
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Manufacturer Recommended Minimum Loading
(continued)
This is an excerpt from PowerTech Engines (John Deere) Engine Application
Guidelines AG-21
EXCESS CAPACITY
The typical generator set runs at less than its full capacity most of the time. As
the load decreases, the operating efficiency of the engine decreases which
increases cost per produced kilowatt. This is not a major concern for Standby
generator sets. However, the increased cost of operating Prime and Continuous
systems at decreased loads can be significant.
Part load operation also allows unburned fuel to gather in the engine exhaust
and lube systems. This type of operation can result in unsightly leakage from the
exhaust system, as well as increased maintenance costs. An oversized engine will
more likely have these problems. A generator set operates best from 50% to 90%
of full rated load. Long term operation at less than 30% of full rated load is not
recommended.
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Low Load Diesel Options
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Low Load Diesel Options
(continued)
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Low Load Diesel Options
(continued)
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Low Load Diesel Options
(continued)
Marsh Creek, LLC. has been selected for award
via the Alaska Energy Authority’s (AEA) Emerging
Energy Technology Fund (EETF) to test and
demonstrate the use of Flux Drive transmission
technology to couple a propulsion diesel engine
to a rotating generator end
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Low Load Diesel Options
(continued)
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Low Load Diesel Options
(continued)
Use the Flux Drive for switching the diesel engines between two gear boxes,
thus allowing the diesel engine to drop its rotational speed from 1800 RPM to 1200 RPM at
lower power demand. This alone would provide about 30% savings of diesel fuel. The
advantage of this option is high power transfer efficiency and the ability to be used for
retrofitting existing generator sets.
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Stamford Permanent Magnet Alternator
Cummins Generator Technologies have used their expertise in generator design
and manufacture to bring you a new generation of axial flux bearing-free
STAMFORD Permanent Magnet Alternators (PMA). Advantages of this
development include a substantially smaller footprint by replacing the engine
flywheel, high efficiency and use in either fixed or variable speed applications
up to 3600 RPM.
Working in conjunction with the
STAMFORD Power Conditioning System
(PCS) the packager can produce a full
variable speed generating set to deliver
high quality output power in a very
compact package, providing benefits of
significantly reduced overall size, weight
and fuel consumption.
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Generating Power through Variable Speed
Stamford Permanent Magnet Alternator
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Stamford Permanent Magnet Alternators
Features, 40kVA PMA compared to conventional 40kVA ac generator:
• Substantial mass and volume reduction
• High efficiency
• No bearings
• Integrated flywheel replacement
• Compact modular design
• Can operate as a motor or a generator
• High Power/Weight/Torque ratio
• High short circuit handling capability
• Can be used for "drive through" applications
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Stamford Permanent Magnet Alternators
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Variable Speed Power Electronics
STAMFORD Power Conditioning System (PCS) is a robust power electronics
device capable of delivering a clean electrical supply for almost any application:AC, DC, 3-Phase, single phase, high and low volts, 50Hz and 60Hz. The PCS
enclosure is fully sealed to give maximum environmental protection.
Working in conjunction with the
STAMFORD Permanent Magnet Alternator
(PMA) the packager can produce a full
variable speed generating set to deliver
high quality output power in a very
compact package size giving the benefits
of reduced overall size, weight and
significant improvements in fuel
consumption.
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Variable Speed Power Electronics
Features:
• Wave form distortion (linear load) – less than 3%
• Wave form distortion (non-linear load, 12 pulse rectifier) - 8%
• Control of engine speed depending upon load
• Fuel savings of up to 25%
• AC and DC outputs at the same time
• Programmable output voltage and frequency
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed
Variable Speed Power Electronics
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Low Load Diesel Options
(continued)
Generating Power through Variable Speed Propulsion Diesel using
Stamford’s Permanent Magnet Alternator (PMA) and Power Condition System (PCS)
• The PMA replaces the flywheel on the engine there by replacing the standard
generator end
• PMA has no bearings, the only moving part is the disk which replaces the engine
flywheel
• The PMA is considerably lighter and smaller
• The 50kVA PCS is approximately 18” square in size
• Constant frequency output
• Maximum size is 50 kVA, though they are currently working on a 100 kVA
• Each is custom built to order. Currently there is not an “off the shelf” option.
• They will custom build to pair with any engine assuming adequate horsepower
curve. You do not need to use Cummins engines.
• Operational rpm’s of the PMA are 800-3300 rpm
• Currently their largest customer is the German military, who use it to power their off
grid operations as prime power.
• Cost for the 50 kVA PCS, PMA and Engineering is around $30,000. No engine
included.
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Low Load Diesel Options
(continued)
Energetic Drives, LLC has designed and created a state of the art diesel generator
employing permanent magnet power that provides 20-30% fuel savings.
The following features are standard.
• Global Power supply: 240 volt through 690 volt 3 phase and 1 phase.
• Advanced Load Demand Load Adapt technology- required for Micro Grid and
Smart Grid compliance.
• Global Certification. IEE 1547, IEE 519, UL 1741, UL 508, CUL, CE verifiable
global compliance.
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Low Load Diesel Options
(continued)
• 4 pole permanent magnet or
induction generator end
• 4 or 6 cylinder diesel engine
• throttle control from 900 - 1800
rpm
• Produces 480v, 60 hz, 3 ph
• Excellent power efficiencies
realized
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Low Load Diesel Options
(continued)
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Low Load Diesel Options
(continued)
• Variable speed diesel generator saves 20-30 % fuel over
existing technologies
• Compact design utilizing liquid cooled power transistor
technology
• System designed to work with new and installed
technologies, rapid deployment, 2 weeks installation
• Ability to control engine air intake temperature, throttle
engine rpm and produce power through extended rpm
range 1200-2200rpm
• More efficient use of power predicated by load demand
• Advance, Load Adapt, Load Demand , patent pending
technology, employed to automatically adjust to load
variances in less than one hundredth of a second
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Low Load Diesel Options
(continued)
Active Power Factor Correction - no capacitors required
• Power Factor ‘setpoint’ provides user adjustability leading or lagging
• Inverter injects corrected kVAR by Pulse-Width-Modulation
• Inverter calculates required kVAR compensation
• Inverter continuously measures PF
Active VAR Control
Active VAR Regulation
Setpoint: 0 - 1.0 lag or lead
VAR Compensation
Sine wave
filter
3-phase
PWM Inverter
AC
Power
Factor
sensors
DC
Power In
Transformer
460VAC:575VAC
3-phase
3 phase
Diode Bridge Rectifier
60Hz
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Run What Ya Brung
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Run What Ya Brung
(continued)
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Run What Ya Brung
Run What Ya (continued)
Brung
(continued)
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Run What Ya Brung
(continued)
Run What Ya Brung
(continued)
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Run What Ya Brung
(continued)
Notes:
1. There are actually 2
each CAT3456
generators on line to
provide grid kVAR
support and stability.
2. The grid load at his
time was 714kW, wind
supplying 546kW,
diesels supplying
168kW, electric boiler
loaded to 26kW.
3. The data point are
15min apart spread
across over a day
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Run What Ya Brung
(continued)
Could these be considered Low Load Diesels?
Are they currently the best option when availability
economics and maintenance are considerd?
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The Bottom Line
• Fuel efficient, proven reliable with reasonable
availability low load diesel technology for Rural Alaska
is emerging and might be pre-commerical
• Select “one off” units are available but come at a order
of magnitude increased price, substantially longer lead
time and unique support and reliability opportunities
• The technologies that hold future promise include:
– Electronic inverter with power factor correction,
permanent magnet generator end, and variable speed
propulsion diesel engine
– If electronic inverters/converters are used they must be
grid forming and/or be capable of kVAR support.
– Standard 1200 or 1800 rpm generator end with constant
speed output transmission paired to a variable speed
propulsion diesel engine
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The Bottom Line
(continued)
• How will the diesel engines we purchase in the
future (low loaded stationary or propulsion used
as stationary) comply with current and pending
emission regulations
• Reciprocating Internal Combustion Engines (RICE)
and National Emission Standards for Hazardous
Air Pollutants (NESHAP)
– New Source Performance Standards (NSPS) and the
Alaska provisions
– Standards of Performance for Stationary Compression
Ignition Internal Combustion Engines
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The Bottom Line
(continued)
• Some of the Utility’s with hybrid wind-diesel
systems are running their modern electronically
fuel injected diesel generator sets below
manufacturers recommended minimum loading
for periods of time and have not reported
consequences that would deter them from
continuing the practice
• From casual discussions, most in this situation
are looking for ways to improve the fuel
efficiency of the diesels when loaded outside
their sweet spot
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The Bottom Line
(continued)
• Review of limited data reveals a clue as to why there
may not be increased engine maintenance on the newer
electronically fuel injected engines. The engines are not
actually subject to extended constant periods of low
load.
• The wind variability along with the need for grid kVAR
support causes the engine to frequently adjust and run
above manufactures recommended minimum loading
for a long enough duration to not have an impact
significant enough to stop the practice.
• This concept may be an idea worth further review to
more clearly define the boundaries we should consider
when designing these systems .
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