Simulation of the Post-Retrofit Thermal Energy Use for the Perry-Castaneda Library Building with the Use of Simplified System Models

Abstract

Several state owned buildings with dual-duct constant volume (DDCV) systems are being retrofitted with energy efficient variable air volume (VAV) systems as part of 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, E,av 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. Unfortunately, in the Perry-Castaneda Library (PCL) building, the retrofits were completed before the monitoring instrumentation was installed. Therefore, no pre-retrofit monitored data are available for this building. Hence another method to estimate savings is needed. Such a method was developed and tested (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.