Use of Simplified System Models to Measure Retrofit Energy Savings

[+] Author and Article Information
S. Katipamula, D. E. Claridge

Energy Systems Laboratory, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843

J. Sol. Energy Eng 115(2), 57-68 (May 01, 1993) (12 pages) doi:10.1115/1.2930033 History: Received September 17, 1992; Revised January 06, 1993; Online June 06, 2008


The retrofit of dual-duct constant volume systems (DDCV) with energy-efficient variable air volume systems (VAV) has become common in recent years. In general, the energy savings from such retrofits are estimated by developing a temperature-dependent regression model using whole building preretrofit energy consumption data. Model predictions are then compared with measured post retrofit consumption, to determine the savings. In cases where the preretrofit energy consumption is not available such a method cannot be implemented. This paper describes a method that can be used to calculate savings in such cases. The method is based on use of simplified calibrated system models. A VAV model was developed based on the ASHRAE TC 4.7 Simplified Energy Analysis Procedure (SEAP) (Knebel, 1983) and calibrated with the postretrofit energy consumption of a large engineering center in Central Texas. The loads from the calibrated VAV model were then used with the DDCV model to estimate the preretrofit energy use, also based on TC 4.7 SEAP, and apparent savings were determined as the difference between the DDCV predicted consumption and measured energy consumption for the postretrofit VAV system. The simulated hourly cooling energy consumption from the VAV model was within ±1GJ (±20 percent) of the measured consumption. The simulated daily consumption (the sum of 24 hours of consumption) compared better with the measured daily consumption (within ±7 percent). The apparent saving from the retrofit of the DDCV system with VAV was about 684 GJ in cooling energy and 324 GJ in heating energy for a three-week period June–July 1991.

Copyright © 1993 by The American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.





Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In