Towards Optimizing Building Energy Use to Reduce Electric System Carbon Emissions

In spite of heightened interest in anthropogenic climate change, little attention has been paid to optimizing a building’s carbon emissions at the source. Most work in building efficiency has assumed that generating plant carbon emissions are constant at their long-term average values. This study sought to improve our understanding of the temporal variations in carbon emissions on a diurnal time scale and their relation to electric system dispatch and load in order to motivate future work in optimizing building operation to reduce carbon emissions. Hourly fossil fuel plant emissions and load data, available from the EPA, were used to characterize power system performance for four US locations (IL, NY, TX, and CA). The study had set out with a hypothesis hoping to find a simple relationship between electric system load and emissions. It was found that there is a significant correlation between increased system load and decreased emissions rates, yet this correlation is not easily defined. During high load conditions, emissions reductions are related to the increased use of gas generators, or may be related to operating plants at more efficient part load ratios. The work conducted in this study shows that, while more complex than hoped for, there is indeed a strong relationship between electric system load and carbon emissions rates.