How’s this for drought response? Earlier this month the utilities division opened the valve on a project that will save 61 million gallons of potable water annually on the Davis campus. 

And all it took was $20,000 in materials and two weeks of staff labor!

HOW IT WORKS

If you’re in an office, lab or other inside space, chances are you’re feeling the results of this cooling project right now!

It all has to do with the chilled water that feeds the cooling systems in our buildings. First, some basics: Chilled water circulates all over the campus via a closed pipeline system — think of it as a big loop. The chilled water delivers its chill all along the way; as a result, by the time the chilled water completes the loop, the water has warmed and needs to be rechilled.

The chilling process takes place in, you guessed it, chillers. Basically, they are giant refrigerators, electric-powered, drawing off heat from the “chilled water return” line. The water comes in at 57 degrees and goes out at 39 degrees.

That’s a lot of heat to get rid of, and, while the chillers could do it all by themselves, the process would take a lot more time and a lot more power for a place as big as UC Davis.

So, the cooling system incorporates a second water supply to help with the heat exchange. This water comes from cooling towers — think of them as giant swamp coolers. Closed pipelines carry the water from the towers, through the chillers (where the water draws heat from the “chilled water return") and back to the towers for a cool-down.

The cooling process is all natural (except for giant fans): The heat is lost to evaporation as the water flows through air-cooled baffles.

Now, here’s how we’re saving all that good drinking water: Cooling towers require a lot of makeup water to account for the evaporation and the water that is drained regularly to guard against mineral deposits in the towers. Up until mid-June, we used well water to fill four of our six towers.

Now we are using treated water from the campus’s sewage treatment plant. That’s right: Instead of releasing the treated water into Putah Creek, as the state allows us to do, we are putting it in the cooling towers.

It’s important to note, the two water supplies never mix. Chilled water stays in its closed system of pipelines, and those pipes do not run through the cooling towers. The towers, now using recycled water, simply provide cool water (in a separate set of pipelines) for the heat exchange in the chillers that keep the chill in the chilled water system.

LANDSCAPE IRRIGATION

UC Davis used about 100 million gallons less water (nonpotable) for landscape irrigation over the last 12 months, compared with the same 12-month period ending in 2013. That’s  30 percent reduction. Here’s an insider’s look from the UC Davis Arboretum and Public Garden about how it’s managing to cut its water use, and how you can do the same thing at home.

The saved water amounts to about 9 percent of the campus’s total potable water use for a year. With this project and other conservation measures, UC Davis has cut potable and nonpotable water use by 13 percent over 2013 and expects to achieve a 20 percent reduction by the end of this year.

In the cooling system project, the utilities division started using recycled water instead of well water to help cool the water that keeps the campus cool. The two supplies never touch each other as one of them, the recycled water, draws heat off the other through the process of heat exchange. The other supply, the one giving off heat, is the “chilled water return” — that is, the water (not so chill anymore) that comes back to the cooling plant after looping through air handling systems in buildings all around the campus.

The rechilled water goes back out to the campus, while the recycled water goes through cooling towers. After cooling down, the recycled water is used again (and again) to draw heat off the chilled water return.

See box for a more thorough explanation, and slideshow for construction photos and schematics.

“With the drought the way it is, we dusted off an idea that had been around for a while,” said David Phillips, director of utilities.

Dave Lawlor, vice chancellor-chief financial officer, in charge of Finance, Operations and Administration, said UC Davis thrives on finding new ways to solve problems.

“This is definitely a clever way to save big on water,” he said. “Credit goes to David and his staff for putting this plan into action, and for doing it so quickly.” 

The right team

Phillips had everyone he needed on his team to get the job done: Mike Fan and his wastewater crew, Lew Pollock and his water and gas crew, and John Larsen and his staff from the Central Heating and Cooling Plant.

“Everyone bought into it right away,” said Terry Duncan, a supervisor on the water and gas team. “Water’s on the top of everyone’s mind.”

Phillips said projects like this are common throughout the state wherever high-quality recycled water is available. “The trick is having the water in the vicinity of where it’s needed, and getting it there,” he said. The Davis campus not only has a nearby source — our own sewage treatment plant, south of Interstate 80 — but we already had a pipeline in the ground to carry the treated water to the main campus.

This pipe was already delivering treated water to the arboretum waterway (to help with circulation), and now we are diverting some of the water to a set of four cooling towers off Putah Creek Lodge Drive, between the arboretum and La Rue Road.

All our crew had to do was lay down about 725 feet of 6-inch PVC pipe. A pump, valves and controls — all connected to the central plant — round out the project.

“I think it is a great example of UC Davis’ taking a leadership position on water management in response to the drought,” Phillips said. “If this works as well as we anticipate, we plan to keep this system in place long after the drought ends.”

How's the “chill” in your building? Too warm, too cold? Tell the utilities division via the “Thermal Feedback” tile on MyUCDavis.

Wringing extra energy from the campus steam plant.

Follow Dateline UC Davis on Twitter.