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Phase A: Initial Development of an Advanced Diagnostic Procedure for Air-Side Retrofits in Commercial Buildings
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The objective of this research is to develop a diagnostic approach that involves analyzing monitored whole-building cooling and heating energy use in large commercial buildings in order to determine the effectiveness of air-side energy retrofits. HVAC systems consume energy in excess of the sum total of the building loads. This excess energy use is due to the fact that a single air-handler unit in a HVAC system, having to provide conditioned air at different supply temperatures to different zones in the building, can do so only by resorting to either, (a) a certain amount of mixing of cold and hot air streams as in dual-duct systems, or (b) to reheat at the terminal boxes in single-duct systems. This mixing of cold and hot air streams or terminal reheating results in an energy penalty, which can often be minimized by converting a constant air volume (CAV) system to a variable air volume (VAV) system. Usually, this penalty cannot be entirely eliminated.
DescriptionThis report proposes an index, called the Energy Delivery Efficiency (EDE), which characterizes this penalty and rates the energy performance of HVAC systems on an absolute scale. The engineering basis of the EDE approach is developed for both one-zone and two-zone buildings, which allows estimating the variation of the ideal EDE with outdoor temperature for a particular building. Year-long measured whole-building cooling and heating energy use data from two retrofitted buildings are finally used to illustrate differences between actual EDE plots of CAV and VAV systems, and how they compare with the ideal EDE of a two-zone building. The use of this analysis approach to provide diagnostic insights into HVAC air-side energy retrofits in both buildings is also discussed. Logical extensions of this work are finally outlined.
Reddy, T. A.; Kissock, J. K.; Katipamula, S.; Claridge, D. E. (1994). Phase A: Initial Development of an Advanced Diagnostic Procedure for Air-Side Retrofits in Commercial Buildings. Energy Systems Laboratory (http://esl.tamu.edu), Texas A&M University; Department of Mechanical Engineering, Texas A&M University. Available electronically from