PNW Smart Grid Demonstration Project

Chilled Water Load Shed

Smart Grid >> Grid Stability Support >> Chilled Water Load Shedding
WSU Steam PLantWSU Chilled Water Load Shed

Air conditioning on most of the WSU Pullman campus is provided by a District Chilled Water (CHW) system. The CHW Plants are home to 9 electric chillers which provide 11,000 tons of cooling capacity. The CHW is pumped through a 2-pipe (Supply and Return) underground system to over 70 campus facilities. The CHW Supply lines carry ~ 40 deg. F. water to the buildings where the chilled water runs through cooling coils on the fan units, warming up to 50-60 deg. F. as it cools the outside air being brought into the building fans. The warm water is carried by the CHW Return lines back to the Chiller Plants to be cooled back down to ~ 40 deg and re-used.

The CHW system also includes a 2 million gallon Thermal Storage Tank. Chilled water can be generated at night when electrical rates may be lower and stored in the Tank for supplemental or emergency use the next day.

Load Shed Control Screen

When a CHW Load Shed is triggered upon receipt of a SGDP Transactive/AGRS request from Battelle/Avista, the CHW output from the Tank will be increased for up to an hour to provide some of the CHW to the campus and reduce the load the chillers need to supply, thereby reducing the electrical chiller load on the grid. The same amount of CHW is provided to the campus, just from different sources, so there is no effect on the cooling available to the campus buildings.

1500 Ton VFD Electric Chiller 2 Million Gallon Thermal Storage Tank
WSU Benefits
  • The Chilled Water Load Shed capability provides a valuable tool for optimizing the CHW system operations in the future by allowing automatic control of the Tank discharge flow
  • As the electrical power rates continue to increase, the ability to shed CHW load on demand will be one tool which can be used for peak shaving to reduce power costs
Facilities Services, 100 Dairy Road, Washington State University, Pullman WA 99164-1150, 509-335-9000