S A C R A M E N T O
C E N T R A L
U T I L I T Y
P L A N T
I
C A S E
S T U D Y
BACnet system inside Sacramento’s new state-of-the-art central
utility plant generates powerful energy and water savings.
Built in 1968, the central utility plant (central plant) serving the
city of Sacramento, California, was out of date in the twenty-first
century. Not only was it incapable of handling high-demand
times, the current system could not expand its capacity and
its use of well water in the single pass condenser barrels of
the chillers thermally polluted the Sacramento River. The State
required an entirely new central plant and it tapped L&H Airco,
Alerton’s central California dealer, to perform the installation of
the chiller plant and heating, ventilating and air conditioning
(HVAC) system temperature controls and energy management
systems.
The new central plant includes a steam boiler plant, chiller
plant and steam turbine generator and thermal energy storage
(TES) tank. L&H Airco
faced a number
of challenges in
tackling the chiller
plant and HVAC for a
project of this scale.
30” return pipes and 250hp fans are just two of
several massive components controlled by the
Alerton system running the chiller plant and HVAC.
Wi t h fo u r m i l l i o n
square feet in
23 State-owned
b u i l d i n g s —
including the State
Capitol—relying on it for heating and cooling services, it was
vital that the new central plant increase its operational efficiency
and capacity—during ANY operational period—while reducing
energy costs and water consumption at the same time.
The plant’s TES tank stores 4.2 million gallons of chilled water
to meet the daytime cooling needs of all 23 buildings. The tank
would need to be tied into—and monitored by—the Alerton
system.
In addition to extensive device-by-device integration, the HVAC
system would also tie in monitoring and control of the steam
turbine generator, a black-start generator, high-pressure steam
boilers, solar arrays, rainwater capture and CO2 monitoring.
The plant’s design also required the incorporation of
sustainability features into every aspect of its operations. The
Alerton system would centrally monitor the HVAC to ensure it
met the plant’s sustainability goals and achieved the required
LEED Gold certification.
The central plant is located in downtown Sacramento. One
major change to the design of the new plant was that it would
incorporate a cooling tower instead of using a river—in this
case the Sacramento River—as a cooling medium for the
chillers. Because of the plant’s cooling capacity requirements,
the cooling towers would be massive—its eight fans are
For our central plant, the choice was made to go with Alerton
and every day it proves it was the right choice.
Jerry Piotrowski, Manager, Sacramento Central Utility Plant
CENTRAL UTILITY PLANT
CASE STUDY
200hp and the condenser
water pumps are 250hp—
yet had to appear as if
they weren’t there at all to
avoid making the entire
area look too industrial. In
addition to minimizing the
visual impact on the site
L&H integrated the thermal energy storage
and surrounding area, the
(TES) tank into the Alerton system for
State required that the new
pinpoint monitoring and control.
facility make a significantly
less environmental impact than the old one.
Finally, L&H Airco had to complete the installation and
commissioning of the new HVAC system according to the rigid
timeline, and with no downtime of any services.
“We considered how we can intercept services and the logic
was, what can we demo and what can we build?” said Mike
Donoho, chief engineer for the central utility plant.
L&H Airco installed two complete Alerton energy management
systems (EMS) to ensure centralized monitoring of the entire
HVAC installation. One Alerton EMS is on the State server level,
which currently controls 23 buildings using the combination
of a BCM-ETH and a VLC-1188. The other EMS is exclusively
dedicated to the plant and energy management. Alerton
operator workstations manage all the facility’s functions
through Alerton’s native BACnet® system, Envision for BACtalk®.
The EMS dedicated to the central plant senses vital chilled
water and steam distribution. L&H Airco integrated seven York
chillers and 64 variable frequency drives (VFDs) through the
BACnet serial interface. The VFDs enable the chiller plant to
operation at 0.5kw per ton—about half the energy use of a
traditional chiller plant.
The central plant uses a Hartman LOOP™, which pulls operating
parameters from the installed equipment—e.g., secondary VFD
speeds and cooling tower fan speeds—and then calculates
the most efficient operating points of the chiller loadings and
returns to the Alerton system a set of optimized setpoints that
the plant facilities staff can then use to adjust the cooling tower.
For example, instead of running two cooling towers at 100%,
it may be more efficient to run three towers with the chillers
operating at 40%. The Hartman LOOP enhances the Alerton
EMS’ data collection and analysis functionality.
“The flexible BACnet interface can actually be a good integration
software tool for collecting data from other systems,” said Jerry
Piotrowski, plant manager for the Sacramento central utility
plant. “Part of the flexibility of the Alerton system is that you
can collect a lot of trendlogs—data—because you never know
what’s critical for you. It should be easy to store and it’s a huge
benefit of Alerton how very easy it is to backup, store and
retrieve your data.”
The Alerton system uses the TES tank to reduce the peak chiller
operation by spreading its cooling load during daytime hours,
which eliminates the need to engage additional chillers during
peak demand times. During the night, the chillers can less
expensively generate chilled water, which is stored and used
during the day. Due to the immense size of the tank, L&H Airco
installed a temperature sensor array inside the tank to generate
the most accurate readings of the thermacline for optimal
cooling. Bifurcation valves enable the chillers to cool the 23
buildings during the day and then charge the TES tank at low
cooling demand periods.
“The TES tank is the key to the new plant on the chill water side,”
Piotrowski said. “Using Alerton software and all the components
to integrate it was one of the major design advantages for the
new plant.”
Occupancy-based sensing, which integrates the lighting system,
reduces energy consumption in the plant’s administrative
spaces by going into standby mode when those areas are
unoccupied. The plant also generates some of its own energy
from solar arrays, which are tied into the Alerton system as well.
When an abundance of solar thermal energy is available, the
system can also heat the HVAC hot water for space heating.
In addition to extensive and complex device-by-device integration and centralized control of the chiller plant, steam
boiler plant and HVAC, the Alerton system ties in monitoring and control of the steam turbine generator, a black-start
generator, high-pressure steam boilers, solar arrays, rainwater capture and CO2 monitoring.
Anticipate the impossible, because it’s probably NOT impossible. Don’t be afraid
of success: that’s exactly what we’re living here. In the end, it was sure worth it.
Mike Donoho, Chief Engineer, Sacramento Central Utility Plant
CENTRAL UTILITY PLANT
CASE STUDY
L&H Airco also installed
Alerton controls for the
steam turbine generator,
which provides the
chillers with emergency
power in the event of a
power failure or during a
demand response loadConstruction of Sacramento’s new central
plant—including the 4.2m gallon TES tank shedding event. In addition
above—and demolition of the old plant
to integrating the steam
had to occur simultaneously to avoid any
operational downtime and disruption to
turbine generator, L&H Airco
services.
used a field server gateway
to integrate the black-start generator and four high-pressure,
250psi steam boilers.
The Alerton system monitors CO2 levels in the office space
and tag-teams it with demand-based ventilation controls for
optimal indoor air quality.
To reduce its visibility, the chiller plant uses the Alerton system
to control eight cooling tower fans at slow rotational speeds
to reduce telltale vapor overhead. The central plant’s use of
evaporative cooling towers, instead of discharging warm water
into the Sacramento River, substantially reduces the plant’s
impact on the environment.
Dashboards are a major feature for every tour of the facility.
Visitors can see all the central plant’s features, the layout of the
chiller plant and steam boiler plant, the CO2 monitoring and the
energy savings.
between construction and commissioning of the new central
plant, and demolition of the old one.
“We transferred the boilers first, then the air system went
from the old to the new,” Donoho said. “Then the chillers
were transferred from the old to the new, so that, as we were
transferring the system to the new plant, they could demo that
section and start erecting equipment.”
“It was quite meticulous planning because you had to share
time and space,” Piotrowski said. “If you were to look at the old
plant and the new, and say, ‘Let’s build and demolish at the
same time,’ the response would be, ‘Are you kidding?’”
The central plant’s facilities manager, chief engineers and their
staff use the data from the plant-dedicated Alerton EMS to
calculate energy use for the plant operation. The HVAC system
installed by L&H Airco uses 70% less energy than current
ASHRAE standards. Piotrowski estimates the total energy
savings around 58%—which equates to 28,000 kWh per day—
and the reduction in water consumption is approximately 90%.
With the inherent energy efficiency measures in the new facility,
the State of California estimates the new steam boiler plant will
return its initial investment within two years, and the chilled
water plant within six years thanks to significantly less energy
consumption. Instead of achieving LEED Gold certification,
the new plant earned Platinum—the highest level of “green”
building design certification awarded by the U.S. Green
Building Council (USGBC).
“The dashboard makes an impact should someone interested in
plant design want to know how it works,” Piotrowski said.
The native BACnet®-based nature of the Alerton system and its
subsequent ability to integrate with other building systems was
a major factor in the State’s decision to choose an Alerton EMS.
Despite the massive scale of the project—and the enormous
size of the equipment to be installed and integrated—L&H
Airco’s expert coordination with the other on-site crews
enabled them to complete the chiller plant and HVAC project
on time per the State’s deadline. There was no downtime
“It’s modern, it’s predictable, it’s accessible,” Piotrowski said. “We
have all the software to operate the plant, we have people who
are trained, and the plant delivered what the design demanded.
What else can you ask for?”
MK-CS-DGSCUP
May 2012
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