Use of Excess Renewable Electricity Generation to meet Future California Stated System Goals
Open Access Publications from the University of California

## Use of Excess Renewable Electricity Generation to meet Future California Stated System Goals

• Author(s): Wang, Sarah Mulan
• et al.
Abstract

The integration of renewable resources, such as wind and solar, is essential to establishing low or zero-carbon systems for climate mitigation. To set this in motion, technologies are necessary to capture the variable, intermittent excess renewable electricity (ERE) generation that exceeds the electric demand. Technologies which can utilize ERE include (1) electric vehicles for zero-emission transportation; (2) energy storage technologies to store renewable generation for later use; and (3) electrolyzers to produce hydrogen for later use in stationary fuel cells and fuel cell electric vehicles. Due to the variety in costs and operational constraints of the technologies and integration to serve different end-uses, an evaluation of low-cost technology is required portfolios to meet stated system goals, such as the renewable penetration into the electric grid.Through linear optimization programming, a methodology was developed to determine the least-cost technology portfolio to achieve the stated system goals. The stated system goals and demands, considered in this study, were based on California as a representative case with the goals for the electric grid of 60% renewable portfolio standard (RPS) by 2030 and zero-carbon by 2045. Demand projections were based on the Energy and Environmental Economics PATHWAYS model commissioned by California state agencies. The results show that the optimized technology portfolios vary depending on the availability of renewable generation. To meet the 2045 goal, for example, the technology portfolio is reliant on (1) higher efficient technologies when less ERE is available and the cost is lower and (2) lower efficient technologies when a higher ERE is available. The lowest total system cost occurs when ample ERE is available, thereby allowing the use of less expensive, lower efficient technologies and the ability to curtail portions of the ERE without having to deploy large capacity electricity capturing technologies to intake peak solar, resulting in 48% curtailment as a percent of the electric demand. This trend is also seen for the 2030 60% goal. However, for the 2045 zero-carbon electric grid, long duration storage is necessary to ensure the seasonally variable renewable generation is properly managed.