The Office of Science manages 10 world-class laboratories, which often are called the "crown jewels" of our national research infrastructure. While many scientific user facilities operated by the Office of Science are highly energy intensive and therefore excluded from the energy reduction goals of the 2005 Energy Policy Act, several facilities have not let this fact deter them from reducing their energy consumption.
An energy saving technology called the “Ganni Cycle” has been developed at Thomas Jefferson National Accelerator Facilityfor application to cryogenic refrigeration systems. The Ganni Cycle (named after a Cryogenic expert at Jefferson Lab) has been proven to reduce energy consumption for cryogenic refrigeration systems by 20 to 45 percent. Since these systems tend to be very energy intensive, the resulting cost savings are substantial.
At Jeffseron Lab, three refrigerators provide -452 and -456 degrees Fahrenheit cold liquid helium for the operation of the Continuous Electron Beam Accelerator Facilityand its three experimental halls, the Free-Electron Laser Facility, and the Superconducting Radio Frequency Test Facility.
The portions of the Ganni Cycle that can be used for existing systems have slashed the power requirements of Jefferson Lab’s refrigeration system, while still meeting the Lab's needs. The cycle has dropped the electricity consumption of the Lab’s cryogenic systems from 6 Megawatts (MW) to 4.2 MW, resulting in a direct savings of $33,000 each month in electricity costs. The cost savings are likely to become even more significant in the future since electric rates are expected to increase from the currently very low rate of approximately 4 cents/kw-hr.
In addition to energy use reductions and energy costs savings, the Ganni Cycle has the added benefit of reducing maintenance costs. The Ganni Cycle nearly doubles the lifetime of some refrigerator components, increasing the time between necessary maintenance periods. Industry standards would indicate that maintenance personnel have to tear down a compressor for a complete rebuild after a maximum of 45,000 hours of operation. At Jefferson Lab with the Ganni Cycle, the number of hours before a required compressor rebuild is around 74,000 hours, gaining a factor of just over 1.7 more running time without having to do repair or maintenance. This is a substantial savings in manpower and spare parts. In addition, the system runs more reliably and efficiently, is more available, and has improved stability.
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratoryand the Spallation Neutron Source (SNS) at Oak Ridge National Lab have both benefited from this innovation through collaborations with Jefferson Lab, and now other facilities are expressing an interest in implementing the process in their cryogenic systems.
At RHIC at Brookhaven, the collaboration reduced the refrigerator electric power consumption by 45 percent, from 9.2 MW to 5.1 MW, through hardware upgrades and the implementation of the “Ganni Cycle.” The RHIC staff has also reported an increase in system stability and reliability.
At the SNS at Oak Ridge, a similar effort centered on optimizing the -456 degrees Fahrenheit liquid helium cryogenic plant operation led to a 32 percent electric power reduction, from 3.8 MW to 2.6 MW.
The DOE Office of Science laboratories will continue to explore the boundaries of science as well as identify and develop new technologies to make our facilities more effective and efficient in this endeavor.