22 December 2016

Vulnerability of Western U.S. Grid Operations to Water Availability: Identified Critical Droughts

Research finds that there is a 3% chance that 6% or more energy demand could be unmet in the summer months.


Droughts reduce hydropower generation and generation capacity of thermoelectric plants due to constrained cooling.  Critical droughts require electricity grid operations to deviate from normal to avoid unserved energy in the summer. The research estimates electricity grid operations over the Western United States during 30 years of water availability conditions to isolate and characterize critical droughts. They demonstrated and quantified the interdependency between drought severity and impact on grid operations using reliability and economics metrics (unserved energy, capacity reserve margin, production cost). They also isolated regional drought patterns which lead to higher vulnerability.


This is the first analysis quantifying the risk distribution of the grid vulnerability as a function of water availability. The combination of the distribution with the developed grid-centric drought severity metric can be used to evaluate and develop adaptation and mitigation scenarios.  


Large-scale assessments of the vulnerability of electric infrastructure are usually performed for a baseline water year or a specific period of drought. This approach does not provide insights into the full distribution of stress on the grid across the diversity of historic climate events.  In this research, scientists from the Department of Energy’s Pacific Northwest National Laboratory estimated the Western United States’ grid stress distribution as a function of inter-annual variability in regional water availability. They ‘softly’ coupled an integrated water model (climate, hydrology, routing, water resources management, and socioeconomic water demand models) into an electricity production cost model and simulated electricity generation and delivery of power for combinations of 30 years of historical water availability data. The results indicate a clear correlation between grid vulnerability (unmet electricity services) for the month of August, and annual water availability. There is a 21 percent chance of insufficient generation (system threshold) and a 3 percent chance that at least 6 percent of the electricity demand cannot be met in August. Better knowledge of the risk exposure probability distribution of the electricity system due to water constraints could improve power system planning. Deeper understanding of the impacts of regional variability in water availability on the reliability of the grid could help develop trade-off strategies.

Nathalie Voisin
Pacific Northwest National Laboratory (PNNL)
Voisin, N, M Kintner-Meyer, R Skaggs, TB Nguyen, D Wu, JA Dirks, Y Xie, and M Hejazi.  2016.  "Vulnerability of the US western electric grid to hydro-climatological conditions: How bad can it get?"  Energy 115: 1-12, doi:10.1016/j.energy.2016.08.059.