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Identifying Energy Efficiency Strategies for Laboratories

Otto Van Geet, National Renewable Energy Laboratory
Susan Reilly, Enermodel Engineering

Abstract:

The energy intensity of laboratories creates great opportunities to implement energy efficiency strategies and realize short paybacks. To identify and demonstrate these opportunities, we developed a simplified model of a laboratory and simulated its energy performance in Minneapolis, Denver, Seattle and Atlanta. Outside air requirements and plug loads drive the sizing of the mechanical systems and energy use in laboratories, so the efficiency strategies we evaluated focus primarily on ventilation, energy recovery, and process equipment load (i.e. plug load) impacts.

The laboratory is a four-story, 100,000 square foot building with 70% of the area devoted to laboratories. A constant volume reheat system serves the building with a maximum relative humidity of 60% and a minimum relative humidity of 30%. Outside air ventilation is supplied at a constant 2 cfm/sf by high efficiency fans. The building has a central plant with water-cooled chillers and hot water boilers. The baseline building meets the ASHRAE 90.1-99 building energy standard, and measured and predicted energy use data from laboratory case studies was used to tune the simulation models. The efficiency strategies are compared to this baseline.

Electricity rates of $0.03/kWh, $7/kW on-peak and $4 off-peak were used in all four climates. On-peak hours are 8 a.m. to 10 p.m., Monday through Friday. Gas rates are $0.6/therm. A rule of thumb for office buildings is that energy costs average $1/sf/yr. For laboratories, the cost is $5-to-$10/sf/yr. The simulation models reflect this, with electricity costs averaging $4/sf/yr and gas costs ranging from $2/sf/yr in Seattle to $5/sf/yr in Minneapolis.

Preliminary results show annual cost savings of $2/sf with a variable air volume system. The fan electricity use alone is reduced by 14 kWh/sf and the peak demand is reduced by 2 W/sf. The paper will discuss the impact of other measures, such as enthalpy wheels, heat pipes, run-around loops, evaporative cooling, and plug load assumptions, as well. Where possible, we will provide rules of thumb for applying these results to new projects.

Biographies:

Susan Reilly received her Bachelor of Science in mechanical engineering from the University of Colorado, and her Master of Science in mechanical engineering from the University of California in Berkeley. Ms. Reilly is a registered Professional Engineer in Colorado and California, and has 18 years of experience in the building energy field. She worked for Pacific Gas & Electric performing energy audits of commercial facilities, and Lawrence Berkeley National Laboratory and the Fraunhofer Institute for Solar Energy Systems researching the energy performance of windows.

Susan Reilly, P.E. is currently president of Enermodal Engineering, Inc., an engineering consulting firm located in Denver, Colorado. Ms. Reilly specializes in simulating the energy performance of commercial buildings using the DOE-2.2 software. She provides design assistance to a wide variety of clients, including the Federal Energy Management Program at NREL, the National Park Service, and private design firms throughout the U.S. She has recently completed work on a large research facility for the University of Hawaii Medical School, as well as analysis of a broad range of efficiency strategies for laboratories in Minneapolis, Denver, Seattle and Atlanta.

Otto Van Geet is currently the Senior Mechanical Engineer in the Site Operations group at NREL, where he has worked on the planning, design, construction and operation of facilities for the past 9 years. Prior to joining NREL, he was a Mechanical Engineer for Sandia National Labs in Albuquerque, New Mexico, for 11 years. Mr. Van Geet has been involved in the design, construction, and operation of energy efficient R&D facilities for microelectronics, photovoltaic, thermal, and biological research, as well as office and general use facilities. This has included integrated building design of clean rooms, supply, exhaust, heat recovery and treatment systems, process gas systems, safety systems, drain systems, fire protection systems, central heating and cooling plants, lighting systems, and control systems. Experience also includes passive solar building design, use of design tools, photovoltaic system design, energy audits, and minimizing energy use. He designed and built an off-the-electric-grid PV power passive solar home in Colorado in which he and his family live.

Mr. Van Geet is a Registered Professional Engineer, a Certified Energy Manager by the Association of Energy Engineers, and has been designated a Project Management Professional by the Project Management Institute. He received a B.S. degree in Mechanical Engineering from the University of New Mexico and an A.A.S. degree in Air Conditioning Technology from the State University of New York.

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