JLab process cools scientific machines, slashing electricity costs for units

Engineers at Thomas Jefferson National Accelerator Center for the past decade have been fine-tuning a process that brings down the cost of cooling large scientific machines operating at their lab and other Energy Department facilities.

Now, the lab has a patent pending for the process it calls the Ganni Cycle, named after the lab's lead thermodynamicist Rao Ganni, and is awaiting DOE approval for a licensing agreement with a company that is seeking to use the technology in cryogenic refrigeration units it manufactures. The lab is also working closely with a manufacturer of small cryogenic units that are more extensively used than those servicing large science facilities, said Dana Arenius, JLab's cryogenic staff group leader. Such units or plants are used to cool machines like the Continuous Electron Bean Accelerator Facility at JLab and the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. JLab first implemented a version of the cycle in 1995 and achieved a 1-megawatt reduction in its electricity use, Arenius said, adding that continued refinement of the Ganni Cycle last year yielded an additional saving of another megawatt. Using 2 MW less energy per day has resulted in a daily saving of $1,000 per day, Arenius said. A megawatt of electricity is enough to power 1,000 homes.

But the savings attained by Brookhaven after it implemented just some aspects of the Ganni Cycle, in addition to some from home-grown process changes since 2003 at the helium cryogenic plant that cools RHIC, are even more dramatic. The RHIC cryogenic plant experienced a 3.3-MW reduction in electricity use, Ahmed Sidi-Yekhlef, the lab's cryogenic engineering group leader, said.

Brookhaven pays between $85 and $110 for a megawatt-hour of electricity, he said. Changes to the RHIC cooling plant have yielded the lab an average daily savings of more than $7,700. This summer, Sidi-Yekhlef's group is making further adjustments to RHIC's cooling plant that are expected to reduce electricity consumption by another megawatt, for a total of 4.3 MW. Cryogenic refrigeration units have traditionally been made to operate on a single operating point — either high, medium or low. If the machine somehow drifts from that operating point, efficiency drops, Arenius said. He said many refrigerators used by DOE labs operate at that highest operating point constantly and unnecessarily.

Performance also improved
Ganni said an unexpected bonus to implementing the process has been improved performance of the machines during experimentation.

Just how much money a facility could save by implementing the Ganni Cycle or some other control process varies by region and what the local electricity utility charges per megawatt hour, Arenius said.

Implementation of the Ganni Cycle does not require new software or hardware, he said. Instead, the process entrails reconfiguring existing components and changing the way they are controlled, Ganni said.

In addition to JLab and Brookhaven, the Ganni Cycle is built into the facility that cools the $1-billion Spallation Neutron Source that recently opened at Oak Ridge National Laboratory. Results there indicate that electricity use decreased from 3.8 MW to 2.6 MW, Arenius said.
The process technology could be easily used in a science facility such as the proposed International Linear Collider, which DOE may build at the Fermi National Accelerator Laboratory, Sidi-Yekhlef said.

JLab's cryogenic team has held workshops with other labs, providing information about the Ganni Cycle and how cryogenic helium cooling units can be adjusted to be more energy efficient, but Brookhaven and the SNS appear to be the only DOE facilities where the cycle or parts of it were implemented, Ganni said. "We've handled a number of inquires" on implementing the Ganni process, including some from Argonne, Arenius said.