The Benefits and Challenges of Applying Heat Pump Chillers for Laboratory Facilities

Gerald Williams and Eric Utterson, McClure Engineering Associates

This presentation will describe the addition and incorporation of a 600-ton heat pump chiller to serve a major group of laboratory facilities at the Washington University School of Medicine in St. Louis, Missouri. The project began with a need to add 600 tons of firm chiller capacity to an existing chilled water loop but with the constraint that no further space was available to install additional cooling towers on this urban campus. The pursuit of this goal lead the design team to explore the use of the laboratory building reheat systems as the heat rejection mode for this chiller. Ultrasonic flow meter measurements and heat exchanger temperature differences were measured to determine the summer and winter loads that existed on the heating water systems used for reheat in three adjacent laboratory buildings with a total area of approximately 825,000 square feet. The analysis also involved determining the minimum supply water temperature necessary to provide these heating needs on a seasonal basis. Serendipity was certainly at work here as the design team ultimately found an elegant solution to this design problem that was both cost effective and sustainable compared to the existing systems. Additional electricity was required to power the heat pump chiller but with significant reductions in campus natural gas use as well as reductions in water use due to no additional need for cooling tower evaporation or blowdown for this additional cooling load. The final cost, energy, and greenhouse gas (GHG) statistics on the project are as follows:

• Project Cost: $2,480,000
• Estimated Project Cost of 600-ton Conventional Chiller and Cooling Tower: $1,305,000
• Cost of Installing Heat Pump Chiller: $1,175,000
• Annual Electrical Energy Increase: $149,000 (+ 4,333,876 kWh; + 4,122 tons CO₂)
• Annual Natural Gas Reduction: $952,000 (- 1,076,655 therms; - 6,288 tons CO₂)
• Annual Water Reduction: $37, 500 (- 15,574,000 gal)
• Total Annual Project Cost and GHG Emissions Reduction: $840,500 (- 2,166 tons CO₂)
• Payback Period on Marginal Additional Cost: 1.4 years
• Payback as a Stand Alone Project: 3.0 years

The system has been in operation since the fall of 2007.

Biographies:

Gerald J. Williams, P.E., LEED AP, is the President of McClure Engineering Associates in St. Louis, Missouri, and has over thirty years of experience in the design, analysis, and commissioning of low-energy HVAC systems. Mr. Williams was a principal lecturer in the ASHRAE Professional Development Seminar "Air Systems Design and Retrofit" from 1982 through 1992 and is past president of the St. Louis Chapter of ASHRAE. He holds both Bachelor and Master of Science degrees in Mechanical Engineering from Washington University and is a Registered Professional Engineer in Missouri, Illinois, Oklahoma, Ohio, Kansas, and California. Mr. Williams is on the Editorial Advisory Board for HPAC Engineering Magazine and presented the Webcast for HPAC entitled "Rightsizing Fans" in May 2007. He has been active in the training of National Environmental Balancing Bureau (NEBB) testing and balancing technicians. He served as a past affiliate professor of mechanical engineering at Washington University. He holds certification as a NEBB System Commissioning Administrator. Mr. Williams has authored numerous technical papers on HVAC and plumbing systems design and analysis in industry technical publications. Mr. Williams has been the principal and project manager on major building designs, energy studies, system energy retrofit projects, and building commissioning projects for such clients as the Washington University Main Campus, Washington University School of Medicine, the Monsanto World Headquarters Campus, Missouri University of Science and Technology, Nestle-Purina, and Pfizer.

Eric G. Utterson, P.E., is a principal at McClure Engineering Associates in St. Louis, Missouri. He holds both Bachelor and Master of Science Degrees in Mechanical Engineering from the Missouri University of Science and Technology and is a Registered Professional Engineer in Missouri, Illinois, and Colorado. Mr. Utterson began his career with McClure Engineering as an intern in the spring of 1996. From 1996 to 1998, Mr. Utterson worked as a project engineer for AJT & Associates in Huntsville, Alabama. Mr. Utterson returned to McClure Engineering Associates as a project manager in 1998 and was promoted to principal in 2002. Some of his projects at McClure Engineering and AJT & Associates have included campus energy studies, mechanical systems commissioning, studies of ventilation and pressure control problems, and PID loop tuning, as well as hydronic, air, plumbing, medical gas, and temperature control systems design for laboratories and other high technology facilities.

Mr. Utterson has considerable experience with laboratory and healthcare facilities, most recently for the Memorial Hospital of Carbondale, Carbondale, Illinois; Southern Illinois Healthcare, Carbondale, Illinois; and Washington University School of Medicine, St. Louis, Missouri. He has served as principal and project manager for laboratory system energy and operational systems retrofits, utility studies and analyses, central plant facility design and analysis, and commissioning of various new construction and retrofit projects. Mr. Utterson has authored several technical papers related to HVAC system controls and applications.

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