The University of Chicago is a proud ENERGY STAR® Partner, working with the United States Environmental Protection Agency and our peer institutions to find ways to reduce higher education campus energy usage. The goal of this program is three-fold: 1) reduce our impact on the environment as our energy usage is about 75% of our total carbon footprint; 2) reduce our operating and capital cost to free up funding for other campus needs, and 3) enable talented University technicians to perform critical tasks on a large and complex campus portfolio of buildings.
As part of the ENERGY STAR® initiative, The University of Chicago’s Facilities Services (FS) department recently completed optimization of the chilled water system to reduce energy usage when outside air temperatures drop below 45F. The University of Chicago campus is served primarily by two chilled water plants, West Campus Central Utility Plant (WCCUP) and South Campus Chiller Plant (SCCP). These plants produce chilled water for over 50 buildings. The chilled water plants use two chilled water economizer heat exchangers to provide “free cooling” when outside air temperatures drop below 45F.
Campus demand for chilled water exceeded the capacity of the chilled water economizer heat exchangers at the plants requiring the operation of additional lower efficiency chillers to augment capacity. In 2017, FS commissioned a study that quantified a 1,100-ton winter load for the campus and hospital, so plans were developed to install additional free cooling heat exchangers at a cost of $350,000 to add the required 400-tons of capacity. The free cooling heat exchangers use roughly one-half of the energy used by plant chillers that use ozone-depleting refrigerant.
The FS Team (from right to left): Adam D’Ambrosio, Camilo Garza, Mike Affeldt, Mike DeSoto, Andy Cobb, and Dan Carey (Not pictured are Felix Leen, Marcus Patterson, John Kerkemeyer, and Jim Murphy).
Prior to investing University capital dollars into the project, the FS team met to determine if operational changes could be made to bring campus chilled water demand within the capacity of the existing heat exchangers. In November 2018, over a series of several meetings, FS staff identified buildings where modifications could be made to reduce the need for additional cooling capacity at lower temperatures. In total, the team identified 20 buildings that could undergo minor mechanical, controls, or operational changes to reduce the need for chilled water and therefore the need for less efficient refrigerant cooling using the Plan-Do-Check-Act model.
Plan – the team agreed to incremental changes that could be made at each building to reduce demand for cooling.
Do – the Engineering Shops and BAS made the changes identified.
Check – the team evaluated the impact of each change to confirm that building systems were not adversely affected and the desired outcome was achieved.
Act – after reviewing the results, the team made changes where appropriate to improve system performance.
Additionally, the team determined that building cooling needs could be met at higher chilled water temperatures allowing free cooling operations at higher outside air temperatures resulting in additional energy savings. By the end of November 2018, all of the incremental modifications were completed.
As a result of this project, electricity consumption from November to April was reduced by 30 percent between 2017 and 2019 resulting in a reduction of over 1,100 metric tons of equivalent carbon dioxide emissions, which is the equivalent of eliminating 234 vehicles. Through teamwork, FS was able to complete the operational improvements at no cost and to avoid the costly purchase of an additional heat exchanger.