POWER October 2015 - 52

DISTRIBUTED GENERATION
cycle. Rather than rely on separate injectors
controlled by a camshaft, HPCR uses a single
system that supplies all the injectors in the
engine with a common source of fuel. This
allows much higher fuel pressures than a mechanical
injection system, which maximizes
vaporization of the fuel and, thus, combustion
rate.
In addition, unlike a camshaft that can only
control one injection event per combustion
cycle, an HPCR system uses an electronic actuator
that can manage multiple separate injections
at different stages of the cycle. That
means far better control of injection timing
and characteristics, which can be customized
for the demands the engine is called upon to
meet while maintaining peak efficiency and
lower emissions.
Ultra-low-sulfur diesel fuel (with a sulfur
content around 15 ppm) is now the standard
for diesel gensets in areas where emissions
must be controlled. The use of biodiesel
(mostly blended with petroleum diesel) is also
growing as a result of the U.S. Renewable Fuels
Standard, though this has been somewhat
controversial and total U.S. production is still
small, around 1 billion gallons a year.
Selective catalytic reduction (SCR) has
been successfully used on new diesel gensets
to reduce NOx
emissions as much as
95%. Another method often used with it is
exhaust gas recirculation, which sends part
of the exhaust gases back into the combustion
chamber. This lowers the adiabatic flame
temperature, allowing for lower-temperature
combustion and thus lower NOx
production.
Better Controls
All this sophisticated technology requires
more sophisticated controls, and traditional
analog systems are giving way to advanced
digital control systems. While small, rarely
used backup gensets can survive on analog,
larger and more complex systems-especially
those providing baseload power-are
moving to digital.
Digital controls are essential for the newest
gensets that rely on HPCR fuel systems and
precise control of ignition and combustion.
They're also necessary where tight emissions
compliance is a consideration.
Another advantage is that digital controls
can monitor the real-time state of a wide variety
of operating parameters and display them
on a centralized panel, as opposed to analog
systems that rely on less-sophisticated alarms
and indicator lights. This allows operators to
identify and correct faults much more quickly,
leading to more reliable power and less
downtime. They also allow for remote monitoring
and operation (though proper cybersecurity
is necessary), another advantage for
gensets that may be located in remote areas.
Though operators must be trained in understanding
more sophisticated systems and
understanding what may be hundreds of different
fault codes, digital systems in general
mean more efficient and reliable operation.
With diesel gensets typically representing
either emergency generation or generation
where there may be no grid power to fall
back on, these are critical considerations.
Diesel Power Is Still Relevant
A casual observer can be forgiven for thinking
that diesel-based power plants are on
their way out. Nothing could be further from
the truth, though. New ones are still being
built, and older ones are being upgraded with
modern controls and other technological
improvements to boost output, increase efficiency,
and reduce emissions.
One such new plant is under construction
in a remote area of Saudi Arabia. The United
Cement Industrial Co. contracted with MAN
Diesel & Turbo to build a 54.5-MW plant
that will power its new cement plant between
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