NREL and research partner GE are conducting the Western Wind and Solar Integration Study (WWSIS) in order to provide insight into the costs and operational impacts caused by the variability and uncertainty of wind, photovoltaic, and concentrated solar power employed to serve up to 35% of the load energy in the WestConnect region (Arizona, Colorado, Nevada, New Mexico, and Wyoming). The heart of the WWSIS is an hourly cost production simulation of the balancing areas in the study footprint using GE’s Multi-Area Production Simulation Model (MAPS). The estimated 2017 load being served is 60 GW, with up to 30 GW of wind power and 4 GW of existing hydropower. Because hydropower generators are inherently flexible and often combined with reservoir storage, they play an important role in balancing load with generation. However, these hydropower facilities serve multiple higher priority functions that constrain their use for system balancing. Through a series of comparisons of the MAPS simulations, it was possible to deduce the value of hydropower as an essential balancing resource. Several case comparisons were performed demonstrating the potential benefits of hydro and to ascertain if the modeled data was within the defined hydro parameters and constraints. The results, methodologies, and conclusions of these comparisons are discussed, including how the hydro system is affected by the wind power for different wind forecasts and penetration levels, identifying the magnitude and character of change in generation pattern at each of the selected hydro facilities. Results from this study will focus on the appropriate benefits that hydropower can provide as a balancing resource including adding value to wind and solar and reducing system operating costs to nearly one billion dollars when offsetting more expensive generation systems as large penetration levels of renewable, especially wind power, are introduced to the grid system.

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