Characterizing Weather and Climate Risks of Wind/Solar–Centric Power Grid in Iowa
Date
2024-08
Authors
Ajang, Dut
Major Professor
McCalley, James
Advisor
Committee Member
Pandey, Santosh
Cui, Bai
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Abstract
Decarbonization of electric energy generation is identified as an effort to slow down climate change. The United States has adopted multiple policies to encourage solar and wind as viable sources of electric power generation. In conjunction with federal policies, major utilities in Iowa – MidAmerican Energy and Alliant Energy, have set an ambitious target of a 100% carbon-free grid by 2050. Iowa’s electric grid is one of the most decarbonized in the country leveraging over 56% of power generation sourced from wind and solar. This transition as the trend has shown projects that the grid will continue to be dominated by wind and solar. To prepare for this transition, evaluation of wind/solar resources, impacts of climate change, and trend of extreme weather events are all basic needs to inform accurate expansion planning process in the state. This study, therefore, aims to assess the reliability of wind and solar resources, specifically examining the frequency of low resource occurrences leading to inadequate generation. It evaluates whether the planned and existing solar and wind plants possess sufficient capacity to meet Iowa's electric power demand. Additionally, it investigates the impact of extreme weather events on the grid's resilience, analyzes the trend of climate change effects on wind/solar resources and overall energy demand, and determines the optimal generation mix between solar and wind to ensure reliability. The study utilizes High-Resolution Rapid Refresh (HRRR) and Super-Resolution for Renewable Energy Resource Data with Climate Change Impacts (Sup3rCC) both of which provide past and future weather data respectively. These sources provide data elements to calculate wind and solar power outputs for all existing and queued projects in Iowa. Solar and wind projects as of 2023– existing and queued, had a total nameplate capacity of 21,431.722MW. The National Renewable Energy Laboratory’s (NREL) System Advisory Model (SAM) is the primary platform for simulation of wind and solar power outputs. Python SAM (PySAM) module utilizes wind turbines power curves to calculate power outputs for existing windfarms. For future wind farms, Vestas V112.3.0 power curve is used to simulate power outputs. SAM’s PVWatts model is used to calculate solar power. With the use of the python pandas library, the computation of per unit powers (PUP) is performed to provide the basis of resources evaluation. Considering the capacity credit of the Midcontinent Independent System Operator (MISO) and intricacies of contingency power system operation, the (PUP) values up to 30% are deemed indicative of low resource conditions (LRC). PUP values below 10% are classified as extreme risks, while values ranging from 11% to 20% and 21% to 30% represent high and low risk conditions, respectively. Examination of recorded extreme whether events in the state of Iowa is also performed. LRC results consistently for 2019 – 2022 indicate that there are at least 973 hours each year where the combined power outputs of wind and solar fall below 10% of the installed capacity. Such extreme event hours are concentrated in the months of July and August. The results also indicate that both existing and planned wind and solar plants are inadequate to meet demand in Iowa. Wind and solar resources are complimentary with wind being low during the summer when solar peaks. This complementarity improves the overall capacity factor during the summer months. The generation mix that supported basic reliability where the PUP is maintained at a minimum level of 30% was found to be 62% wind and 38% solar. Examination of extreme weather events indicates that high wind speed events which are a threat to power system resilience have been on the rise and are predicted to continue rising. Temperatures are expected to rise by 2050. At the same time, the overall combined capacity factor of both wind and solar is posed to increase by 2050. The comparison of results from both HRRR and Sup3rCC indicate level of symmetry where variations lie within the 2% margin of error. To address the prevalent resilience risks as well as reliability concerns noted in the results, the state of Iowa needs to perform a co-optimized expansion planning on the grid to prepare for higher penetration of wind and solar.
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creative component
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Attribution-NoDerivs 3.0 United States
Copyright
2024