POWER November 2010 - 49

SMART GRID
2. Short stack. From most points on campus, the power plant's stacks cannot be seen. A dry
low-NOx emission system avoided the necessity of taller stacks. The top of the chilled water tower is
visible on the right, behind the eucalyptus tree and the Central Utilities Building. Source: POWER
UCSD's cogeneration plant at a glance. Source: UCSD
Equipment
Prime movers
Emissions control
Chilled water
Thermal storage
Operation
NOx emissions level
Gross thermal efficiency
Net efficiency
Costs
Capital cost
$27 million
Avoided electricity purchase costs per year $8,040,000
Payback (years)
5
Take a Video Tour of UCSD's Cogeneration Plant
We have posted links to a video tour
of the cogeneration facility at the
University of California, San Diego on
our web site. For the next few months,
you'll find a link on our home page
(www.powermag.com) in the Video
section (lower right). You can access
that link via the online version of this
story over the longer term. If you
thought cooling towers were only for
48
cooling turbines, watch the video to
learn about another important function
they can provide.
We're also posting links on the
home page and in the online version
of this story to a video produced by
the university that looks at the combined
heat and power plant and includes
shots of some of the campus
photovoltaic installations.
www.powermag.com
2 Solar Turbines Titan 130 13.5-MW combustion turbine generators
(combined cycle)
1 Dresser-Rand 3-MW steam turbine
Solar Turbines SoLoNOx (dry low emissions)
Murray-Tuthill steam-driven centrifugal chiller
3.8 million gallon cold water storage tower from PDM to meet peak
cooling needs
1.2 ppm annual average (permitted level is 2.5 ppm)
70%
66%
the table for details), which operates at a
net efficiency (LHV) of 66%. Cogeneration
plants are also often called " combined heat
and power " plants, but they can do more. Although
many cogen plants do not use steam
to drive chilled water, doing so makes a lot
of sense for UCSD, Dilliott noted (see sidebar).
Chilled water-cooled overnight when
electrical demand is low-is stored in a 3.8
million gallon storage tower. During the
day, chilled water goes out to all the campus
buildings for air conditioning. The heat removed
from the buildings is absorbed by the
refrigerant, transferred to the cooling water
in the chiller, and rejected to the atmosphere
by the cooling towers.
The San Diego campus was founded in
1960, and the Central Utilities Building (Figure
1) was the first structure built. Thanks to
forward-thinking planners, steam was produced
on campus from the beginning, and
supply lines for heating and cooling were built
out as the campus grew. Having all the steamusing
equipment in place made adding cogeneration
a lot easier, Dilliott acknowledged.
Annually, the cogen plant, which operates
in electrical load-following mode with thermal
override, supplies 85% of campus electricity
needs, 95% of its heating, and 95% of its cooling.
(See the online supplement " Matching
Load and Generation at UCSD " for seasonal
electrical and thermal load profiles.)
Thanks to Solar Turbines' SoLoNOx dry
low-emissions system, the UCSD plant's
emissions of NOx
are typically below 1 ppm,
which, Dilliott explained, is why the plant
does not require tall stacks (Figure 2). In fact,
Dilliott noted that when area wildfires have
burned, the ambient air held more NOx
the plant was emitting.
than
Economics, Pure and Simple
When asked about the original impetus for
constructing a cogen plant, Dilliott explained
that it was purely economics. Prior to deregulation
in California, utilities' " departing load
charges " served as a disincentive to distributed
generation (DG), as did various utility
incentives not to cogenerate. When utilities
went out of the generation business and those
potential charges were no longer a factor, the
economics improved.
Before cogeneration, the campus imported
all of its electricity and purchased natural gas
to operate boilers that made steam for heating
and cooling the campus. Though the campus
still purchases gas for the plant's turbines, it
does so through the California Department
of General Services at an attractive rate.
(The local utility, San Diego Gas & Electric
[SDG&E], only provides transmission and
distribution for commodity power and gas.)
That option, Dilliott pointed out, was open
POWER| November 2010

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POWER November 2010

Table of Contents for the Digital Edition of POWER November 2010