The University of Texas at Austin houses what is often described as the most integrated and largest microgrid in the U.S., a model for saving energy and money.
Built in 1929 as a steam plant, the facility has evolved to provide 100 percent of the power, heat and cooling for a 20-million square-foot campus with 150 buildings.
The university is known for its premier research facilities, which demand high-quality, reliable power. And its microgrid has delivered with 99.9998 percent reliability over the last 40 years.
The facility features a combined heat and power plant that provides 135-MW (62-MW peak) and 1.2 million lb/hr of steam generation (300k peak).
The system also includes 45,000 tons of chilled water capacity in four plants (33k peak); a 4 million gallon/36,000 ton-hour thermal energy storage tank; and 6 miles of distribution tunnels to distribute hot water and steam. The microgrid engages in real-time load balancing for steam and chilled water. Since 1936, natural gas has fueled the energy plant.
Long history, frequent innovation
As the campus grew over the years, the plant operators had to find ways to increase its capacity in a cost-effective manner that maintained high reliability. UT Austin added over 4 million square feet in less than two decades and now has 2 million more square feet in design and construction.
"The objective was: How can we pay for this expansion and not increase costs to the campus," said Juan Ontiveros, the university's executive director of Utilities and Energy Management.
Ontiveros achieved this goal by saving fuel. This meant redesigning the load control system and implementing new control strategies, always with an eye toward retaining high reliability not only for electricity, but also steam and cooling.
"We have a lot of contingencies built into our system that most people don't have, but probably would like to have. We can island, wheel, and we handle all three energies simultaneously, 24 hours a day," he said.
The plant's combined heat and power system allows it to recover heat energy that a conventional plant would waste even a state-of-the-art supercritical unit might discard 40 percent of the heat it produces, Ontiveros said. But a CHP system extracts the heat from a steam turbine generator and re-uses it to heat the campus. Leveraging the existing distribution system captures more efficiency in cooling technology.
"We use all the tricks. We can do turbine inlet-air cooling, thermal storage, load shifting, load shedding. It's all built into our load control system. We produce our all electric cooling at probably 40 percent (of the cost) that the rest of the world does," he said.
The campus has become so highly efficient that despite its expansion it now uses no more fuel and emits no more carbon dioxide emissions than it did in 1976.
"The overall plant efficiency in those days was 42 percent; we're at 86 percent now," Ontiveros said.
High performance at net zero
While some microgrids sell power or services to the grid, UT Austin does not. This is because its energy plant is sized to be net zero: to produce only what it needs.
The university holds a 25-MW standby contract with the local utility for back-up power if equipment fails, at a cost of about $1 million annually, a small portion of the plant's $50 million annual operating budget. Other than that, UT Austin operates with autonomy from the central grid.
"I see ourselves as at high risk anytime we are on the grid because we are more reliable than them," Ontiveros said.
Energy reliability is extremely important to the university. Eighty percent of the campus space is dedicated to research valued at about $500 million.
"If a professor loses a transgenic mouse with 20 years of research built into it, that's a nightmare. That's what keeps me up at night," Ontiveros said.
Ontiveros's worry about always keeping the lights on is echoed by energy plant operators throughout the U.S. as our power-dependent economy becomes increasingly research- and technology-oriented. This is why energy-sensitive institutions and industries are increasingly investigating development of microgrids. And with its impressive record of only three campus-wide outages in 40 years, UT Austin's microgrid stands as a signature case study for how it's done.
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12 December 2017