Toward Grid-Friendly Zero-Energy Buildings

High-performance buildings, such as zero-energy buildings (ZEBs), are an important step toward a reduction in greenhouse-gas emissions. Because ZEBs may exhibit large differences between demand and on-site generated electricity, residual electrical loads imposed by the building may fluctuate between positive and negative values. Furthermore, such buildings can be characterized by large temporal changes in residual load, commonly caused by clouds passing on a sunny day. Today, electricity grid operators can easily deal with a single ZEB with this behavior. But what happens if large portfolios of ZEBs have the same behavior? In this study, a highly efficient office building with a total floor area of 8,355 m² located in Denver, Colorado, was designed and simulated using a detailed building energy modeling approach. Combining the building energy model with a photovoltaic model showed that the building reached net positive status on an annual basis. Further analysis of residual loads and strategies for their reduction revealed the limited potential of demand-side management in ZEBs and the high flexibility of batteries. Using a multiple-objective optimization approach for optimizing several simplified electric and thermal storage systems allowed the comparison of different strategies for residual load reduction. Although electrical storage may not yet be economical given today’s system costs, results show that the residual loads can be effectively managed and reduced, and at the same time, an increase in photovoltaic self-consumption can be achieved. The analysis concludes with the presentation of a multiple-objective optimal solution (Pareto front) for a battery storage model, indicating what utility incentives would be required to achieve cost-effectiveness for a range of price scenarios for battery systems.