The University of Utahs new cogeneration project might look like any other system, but it represents an unexpected approach to CHP.
Blame it on the bold, new world of
sustainability, where economics isn’t necessarily a top priority, a turbine’s
efficiency actually can be too high, and electricity—rather than exhaust heat-is
the byproduct. Yes, the University of Utah’s new combined heat and power (CHP)
has rewritten the rules, but it still offers a textbook case of distributed
energy’s superior performance.
This unique CHP unit is the final
chapter of a six phase, 20-year guaranteed energy savings contract between the
University of Utah (located in Salt Lake City, UT), and Chevron Energy Solutions
(San Francisco, CA). It began in 1998 and includes extensive heating, cooling,
lighting, and energy management; and water conservation improvements to 81
campus buildings. In all, the first five phases offered a radical construction
and cultural change for the university, so it’s no surprise that the CHP project
would cap the program by turning traditional CHP methodology on its head. As
evidence of the “green” trend universities are embracing, it’s easy to see why
the project was destined from the beginning to be different.
According to Cory Higgins,
director of Utah’s plant operations, sustainability was a top priority when
campus engineers decided it was time to replace aging boilers that supplied
450˚F water to heat campus buildings. “In the last years, the university has
recognized that we have a responsibility and an opportunity to represent to the
community good business practices,” he says. “Particularly as they relate to the
environment and sustainability.”
Rather than just taking the
simplest and cheapest solution, engineers looked at the other alternatives.
Higgins adds, “To replace these two boilers may have cost us near $4 million,
but we asked ourselves—‘do we just get the usual maintenance money and replace
these, or is there something else that would make more sense?’”
Cogeneration was one of the
obvious alternatives, and a study by Chevron came up with a heat-based design
that satisfied the university’s heat loads, operational needs, space
availability, and cost. The study, which took about six months, showed that a
small increase in natural gas usage could drive a turbine that created 6 MW of
electricity.
Higgins and his team visited
cogeneration projects at other schools, but found that their project didn’t fit
the mold in a number of areas. “Other schools in Utah and California use
cogeneration, but they were sized and designed on the model of electricity first
and waste heat second,” he recalls.
The team also found that the high
efficiency of the electricity-first designs was stressed, but with the turbine’s
waste heat output as the prime concern for Utah, such high efficiency wasn’t the
only factor in choosing the right turbine.
How Much Efficiency Is Too
Much?
“One of the things we kept looking
at was the efficiency of electric turbines,” explains Higgins. “You have to look
at it differently because you don’t want a really efficient unit that makes less
heat. I think Chevron and solar turbines matched the system to give us the most
efficient balance. We could have gone with a more efficient turbine and that
could have generated more electricity, but then we would have to spend more
money and we wouldn’t have enough heat. But we were still trying to get the most
out of every Btu. Nonetheless, the
system has an efficiency rating in the high 90s.”
According to Frank Gallardo,
project manager for Chevron, the university’s concern for the environment and
the aging boilers presented an ideal opportunity to bring a different approach
to cogeneration. “One of the things we worked towards was their concern for
sustainability,” says Gallardo. “They had five boilers, and the two we pulled
out were early 1960’s vintage and not good for the environment.”
Those two units accounted for 65
million Btu per hour, and contributed to keeping the campus’ 450˚F high
temperature, hot water demands.
“Our intent was not to put in the
electric plants; we designed these as thermal plants,” notes Gallardo. “We did
not want to create any load by going in with absorbers or anything else that
would increase their thermal requirements.”
High Exhaust Heat From Low NOx
Output
As for the choice of a turbine
that didn’t stress thermal efficiency, Chevron specified a Solar Taurus 70
natural gas turbine, rated at 6.0 MW (site adjusted). The unit produces
25–28-million-Btu-per hour waste heat, and there’s an extra benefit to please
the sustainability requirements—just 9 parts per million of nitrogen oxide (NOx)
output.
“That's very low compared to other
equipment,” notes Gallardo. “It’s clean without needing strategic catalytic
reduction due to Solar’s SoLoNOx technology.”
The clean exhaust travels to a
Rentec waste heat recovery unit, and since the total boiler capacity is 110
million Btu per hour, a supplemental burner adds another 75 million Btu per
hour.
With the additional 6 MW of
electricity to the campus grid, some substation upgrades were needed. A new,
12.47 kV switchgear, with dual bus arrangement to facilitate maintenance, was
installed. Then came breakers to the feed generator’s 12.47-kV, 4-kV and 7-kV
loads. Two utility transformers were removed, and, finally, a main breaker for
interconnection with Rocky Mountain Power and interconnection protective
relaying rounded out the substation’s improvements.
Due to the size of the campus, the
heating system was designated as having upper and lower sections that were
originally served by two separate boiler facilities. After weighing the issues
of pumping hot water long distances and concerns about aging equipment,
Chevron’s plan called for upgrading only the lower section.
“Initially we were hired to take a
look at both heating plants and determine the viability of cogeneration,”
Gallardo explains. “Based on our
analysis, we specified the lower campus heat plants as good candidates, but in
the upper plants we recommended that they hold off until there was more heat
load.”
 |
Photo: Chevron Energy Solutions |
| The new CHP unit's success has laid the ground-work for future improvements at the University. |
As for handling future growth in
the heat requirements of the lower campus, Chevron sized the turbine and waste
heat unit to meet the demand for up to a 12% increase in heating loads.
Conversely, when heating demands fall, the unit can be ramped down to operate in
a “load follow” function. And with the university’s focus on sustainability,
it’s likely that the turbine will see some days of below-average load demand.
Although much of the university’s energy demand has dropped, thanks to the first
five phases of Chevron’s energy savings contract.
Savings Rack Up Millions
In fact, the lowered demand was
responsible for a surprisingly high financial impact on the total project. The
unexpected excess savings from phase one were $780,000. Phase two saw excess
savings of $620,000. The combined savings from the first two phases funded a new
6800-ton-capacity central chilled water plant. Phase 4 managed to deliver
savings of $600,000—enough to pay for a new high-temperature water plant.
All these savings started with a
comprehensive energy analysis launched in October 1998. The first and second
phases addressed building energy usage in 24 buildings, with conservation
improvements such as: high-efficiency lighting, new chillers, energy management
systems, and variable speed drives and pumps. Phase three built a new 6800-ton
chilled water plant. Phase four brought more energy conservation improvements to
another 57 buildings, and phase five saw the construction of a
210-million-Btu-capacity, high-temperature hot water plant.
Chevron’s contract includes
operations training for university personnel and the initial commissioning
process will provide training on the waste heat recovery unit and the new
controls for the plant. “Training and commissioning is a big part of what we're
doing here,” says Gallardo.
Another big part is the
contribution to a culture change. Gallardo has seen an impact far beyond the
mechanical and electrical changes.
University president, Michael
Young, agrees. “In everything we do there is not only a practical dimension, but
there’s a teaching dimension as well,” says Young. “To the extent that we can
weave into our everyday operations these habits and practices that make
economical and environmental sense, it helps inculcate these principles into the
lives of our students as they go out into the larger world.”
Now that phase six is drawing to
close, Gallardo is taking a second look at both the complexity and the sheer
volume of work. “One thing that is unique about working with a university is
that they are huge,” he notes. “They have a lot of critical load and a lot of
research is going on so any outage or inconvenience can be crucial. We had
weekly construction meetings to review the previous week's progress and in
addition to that to go over any issues coming up. The good communication has
been a key factor in the project’s success.”
For Higgins, success will be
measured in the contribution to sustainability and the system’s economics. “We
sized our project so that only 10 to 15% of our electricity will be generated by
the unit, but 100% of our heat needs will be met,” he says. “It makes sense because we have to buy
the gas to generate the heat either way and it's not that much more gas.”
Though the CHP unit was still
waiting for final approvals from the utility company, initial estimates showed
an increase of about 20% more natural gas over the amount used if the university
had chosen to simply replace the old boilers with high-efficiency models. But
much of that cost will be offset by the 6 MW of power, and one other factor that
wasn’t a major issue until recently-skyrocketing oil prices.
“We loved the idea of the
efficiency and capacity to recapture heat, and generating electricity seemed
like a very good idea,” recalls Young. “Then, we thought that we would be paying
more to build the system but looking at the cost of natural gas; at the time it
was a close call. So, at the time, we made a decision it was more of an
environmental consideration. Yet now we look like geniuses because of oil
prices.”
Moreover, the university looks
like it has secured a position of leadership in the fast-growing green campus
movement. Young notes that the CHP project helped his administration to create
awareness, by orchestrating the CHP’s ribbon cutting ceremony to coincide with
Earth Day. On that day, Young also announced that Utah had established both a
sustainability committee to advise him on projects and policies for the
university, and a permanent sustainability office and director.
Finally, he joined more than 500
other college and university presidents that have signed the American College
& University Presidents Climate Commitment, an initiative addressing global
warming through institutional commitments to neutralize greenhouse gas emissions
and accelerate climate research.
Ultimately,
the commissioning of the new CHP unit isn’t really the final chapter of the
university’s energy savings contract. Its success has laid the groundwork for
future distributed energy improvements to the upper campus, and major policy
changes, such as all new buildings designed to meet Leadership in Energy and
Environmental Design (LEED) certification standards. And the university’s goals
for creating an impact are succeeding. The project has been credited in helping
to promote energy performance contracts for a regional state office building,
the Utah State Prison, and Utah Valley Community College.