How do non-carbon priorities affect zero-carbon electricity systems? A case study of freshwater consumption and cost for Senate Bill 100 compliance in California

摘要

Characterizing the advantages and disadvantages of different electricity resource mixes in meeting electricity decarbonization goals is an active area of research. Many system-level assessments, however, evaluate different mixes on the basis of minimizing electricity costs without accounting for regional environmental externalities. California represents a highly populated region with both aggressive electricity decarbonization policies and water scarcity issues that are projected to worsen under climate change, representing an interesting case study for assessing the tradeoffs between the costs of electricity decarbonization and water resource consumption. This study therefore combines electric grid dispatch modeling and regional life cycle freshwater consumption data to compare in-state freshwater consumption and levelized cost of electricity for four electricity mix scenarios designed to achieve zero-carbon electricity in California by 2045, compliant with current law (California Senate Bill 100). In modeled scenarios, we find that the lowest costs occurred for mixes with lower energy storage capacity needs enabled by high capacity factor and dispatchable renewables. However these mixes also resulted in high freshwater consumption due largely to heavy reliance on geothermal resources. By contrast, the mix with the lowest freshwater consumption relied exclusively on wind, solar, and hydropower and reduced water consumption by an order of magnitude compared to that of the lowest cost mix. Due to lower capacity factors and greater difficulty in matching supply to demand (increasing energy storage needs), this mix increased the levelized cost of electricity by 30%. Overall, our results show that prioritizing low electricity costs as well as other climate-relevant criteria, such as freshwater consumption, in meeting zero-carbon electricity goals will result in a very different electricity mix than simply considering costs alone.