UC Berkeley, March 30, 2022 – Early this past Monday morning, a small team of University of California, Berkeley, engineers gathered around a two-story-tall drilling rig parked at an out-of-the-way spot on the north side of campus. As the overnight rain turned to drizzle, the team watched as a drilling crew used a massive 8-inch-wide drill bit to start punching a new borehole in the soil.

By the end of the week, this borehole will extend 400 feet below ground, becoming the deepest borehole on campus and providing engineers with the first opportunity to study the properties of the bedrock that sits below UC Berkeley. They will use the information that they gather from the borehole to help determine whether a geothermal heat pump system — which uses the thermal properties of subsurface rock to help heat and cool buildings more efficiently — could be integrated into UC Berkeley’s long-term plans for decarbonizing its energy system.

“Nobody has ever drilled this deep beneath the campus,” said Kenichi Soga, the Chancellor’s Professor and Donald H. McLaughlin Chair in Mineral Engineering at UC Berkeley. “Most of the boreholes that we have on campus are used for designing new buildings and typically only go down to 60 or 80 feet. Now, we’re going to 400 feet. It’s going to let us see what is happening at that depth and better understand the possibility of using geothermal heat pumps on campus.”

Unlike deep geothermal energy systems, which use boreholes as deep as 10,000 feet or more to harvest heat from Earth’s core, geothermal heat pump systems use the thermal properties of the near underground. In these systems, the heating and cooling needs for a community are provided by a network of water pipes, which run through shallow boreholes that extend approximately 400 to 500 feet below the surface. Ideally, these systems take heat that is generated by cooling buildings during the summer and store it underground, where it can be used to heat buildings during the winter.

As part of the Clean Energy Campus Initiative, UC Berkeley plans to decommission its 40-year-old cogeneration plant and replace its current steam heating system with a new system that uses water pipes to heat and cool buildings on campus. While the cogeneration plant burns natural gas to produce electricity and steam heat for the campus, the new system will use electricity for both power and thermal needs. By using clean energy sources, such as wind and solar, to produce this electricity, the campus’s future power, heating and cooling needs would be entirely carbon-free.

The borehole will provide the research team with the first detailed measurements of the geological conditions hundreds of feet below the campus, a necessary first step in determining whether geothermal technologies can be used to make this heating and cooling system even more energy efficient. The primary support for this initial borehole was provided by The Green Initiative Fund, a grant program funded by UC Berkeley student fees and administered by a student-majority committee.

“We need to replace this cogeneration plant because its useful life is almost over, and we want to pivot and build something for the future,” said Kira Stoll, chief sustainability and carbon solutions officer at UC Berkeley. “Our goal is to have the campus transition to using 100% clean energy to heat and cool our buildings by 2028. I’m looking forward to finding whether we do have geothermal potential on the campus and whether we can integrate that into our plans to make a very efficient clean energy system.”

Many of the devices that we use to keep things cool rely on heat pumps, which work by redistributing heat energy from one location to another. For example, air conditioning systems work by transferring heat energy from the inside of a building to the outside of a building.

Because rock and soil have a much larger heat capacity than air — they can absorb and store more heat energy without letting it diffuse away — the ground underneath our feet can essentially act as a storage tank for heat. Geothermal heat pumps, also known as ground source heat pumps, are designed to pump excess heat underground into boreholes, where it can be stored.

“If you pump heat outside into the air, it will quickly dissipate, whereas if you heat or cool down a large amount of rock, then it will stay hot or cold for a much longer period of time, and you can potentially get the hot or cold back,” said Peter Nico, soil and environmental biogeochemist and acting division director for the Energy Geosciences Division at Lawrence Berkeley National Laboratory (Berkeley Lab).
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For full article by Kara Manke, visit: https://news.berkeley.edu/2022/03/30/...

Video by Roxanne Makasdjian, Alan Toth, Adam Lau

http://news.berkeley.edu/
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