Discussion and Outlook The reference project demonstrates a significant GHG avoidance potential with load shifting. When dispatch sequences are well-configured and designed to respond to changing grid conditions, even a battery bank with a small capacity can avoid substantial GHG emissions. When not designed well, however, the GHG avoidance from on-site renewable resources can diminish in the future as the grid gets cleaner. Accordingly, any design and system sizing decisions based on present grid emission profiles can seriously limit the future emissions avoidance potential. The reference project is based in California within the context of an electric grid with high solar contribution already, and a projection that solar photovoltaic penetration will increase significantly over the next few years. While the exact results of a similar study will differ for other projects based on their demand profiles and grid-regions, the findings are applicable for any region with a reasonable Renewable Portfolio Standard. With renewable penetration increasing in grids across the board, periods of curtailment for intermittent renewable energy sources may differ but the magnitude of difference in GHG emission factors between mid-day and lateafternoon hours will be similar. Finally, it is important to note that this paper focuses on only one of several mechanisms for load shifting - electrical storage and dispatch with the help of batteries. Similar arguments apply to load shifting through thermal storage and building demand management controls. Such microgrids - thermal or electric - that offer an optimal combination of building controls, distributed energy resources, and storage will play an increasingly important role towards decarbonization of the built environment, especially with the increasing penetration of intermittent renewables in the grid as time-of-use considerations becomes paramount to avoid future grid emissions.
Shreshth Nagpal Principal - Design Analytics | snagpal@elementaengineering.com Rushil Desai Building Performance Analyst | rdesai@elementaengineering.com
Endnotes
1 Desai R, Shah S, Nagpal S, Investigating the impact of cost-based and carbon-based renewable energy generation and storage sizing strategies on carbon emissions for all-electric buildings; 2018 BPACS 2 https://www.integralgroup.com/news/climate-mobilization-act/ 3 https://www.cityofberkeley.info/climate/ 4 Siler-Evans K, Azevedo IL, Morgan MG. Marginal emissions factors for the US electricity system. Environmental science & technology. 2012 May 1;46(9):4742-8.
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