Simulation of the Post-Retrofit Thermal Energy Use for the University Teaching Center (UTC) Building with the Use of Simplified System Models

Abstract

Several state owned buildings with dual-duct constant volume (DDCV) systems have been retrofitted with energy efficient variable air volume systems (VAV) as part of the Texas LoanSTAR Program. One method of determining the energy savings resulting from energy conserving retrofits relies on the use of a model for the daily whole building consumption, Epre, in the pre-retrofit configuration. Epre is typically a function of primary influencing parameters such as ambient temperature, humidity, building internal gains and others (Figure 1). Following the retrofit, the energy saved, Esav is determined using measured daily consumption, Emea3 as shown in Figure 1. This method is being used in the Texas LoanSTAR monitoring and analysis program for buildings that have adequate pre-retrofit monitored data (Kelly et al., 1992). Unfortunately, in the University Teaching Center (UTC) the retrofits were completed before the monitoring instrumentation was installed. Therefore, no pre-retrofit monitored data are available. Hence another method to estimate savings was needed. Such a method was developed and tested on a large engineering center (Katipamula and Claridge 1991). This method was based on the use of the ASHRAE TC 4.7 simplified energy analysis procedure (SEAP). It involved developing one model each for the VAV (post-retrofit system) and the DDCV (pre-retrofit system) systems.