A Sequential Search Technique for Identifying Optimal Building Designs on the Path to Zero Net Energy

A zero net energy (ZNE) building produces as much energy on-site as it uses annually -with a grid-tied, netmetered photovoltaic (PV) system and active solar water heating. On a plot of annual costs (the sum of utility bills and mortgage payments for energy options) versus percent energy savings, the path to ZNE extends from a base case building through a series of energy-saving designs to the ZNE building. The optimal path is defined by connecting the points for building designs that achieve various levels of energy savings at minimal cost (establishing the lower bound of results from all possible building designs). BEopt, a computer program for building energy optimization, calls the DOE2 and TRNSYS simulation programs and automates the optimization process. The optimization method involves sequentially searching for the most cost-effective option across a range of categories (e.g., wall type, ceiling type, window glass type, HVAC type, etc.) to identify optimal building designs along the path to ZNE. The method is particularly well suited to ZNE path optimization, because it deals with discrete options, finds intermediate points along the path and, in the process, identifies a number of near-optimal alternative designs.