Climate change and future power systems: the importance of energy storage in reduced-hydropower systems in the American Southwest

Power systems are responding to climate change both through efforts to reduce greenhouse-gas emissions and through adaptive responses to the effects of climate change,such as changes in hydroelectric generation.These changes,experienced together,may cause new patterns in plant operations or pollutant emissions.Various scenarios representing future climate change mitigation and adaptation in the power sector were explored using the PLEXOS production-cost model,with a focus on plant utilization and behaviour,total system-operating costs and total CO_(2) emissions.Further,the effect of introducing widespread utility-scale energy storage into these scenarios was quantified in terms of these same parameters.Large increases in variable renewable penetration combined with extreme reduction of hydroelectric generation in the American Southwest(based on climate modelling in the Colorado River basin and actual drought experience in California)caused significant increases in thermal plant start-up/shutdown cycling.The introduction of storage significantly reduced this cycling,without a material increase in CO_(2) emissions.Storage introduced on even a modest scale can provide considerable flexibility under a range of future power-system circumstances that might be experienced due to climate change.

Cost implications of increased solar penetration and time-of-use rate interactions

Electricity-grid operators are facing new challenges in matching load and generation due to increased solar generation and peak-load growth.This paper demonstrates that time-of-use(TOU)rates are an effective method to address these challenges.TOU rates use price differences to incentivize conserving electricity during peak hours and encouraging use during off-peak hours.This strategy is being used across the USA,including in Arizona,California and Hawaii.This analysis used the production-cost model PLEXOS with an hourly resolution to explore how production costs,locational marginal prices and dispatch stacks(type of generation used to meet load)change due to changes in load shapes prompted by TOU rates and with additional solar generation.The modelling focused on implementing TOU rates at three different adoption(response)levels with and without additional solar generation in the Arizona balancing areas within a PLEXOS model.In most cases analysed,implementing TOU rates in Arizona reduced reserve shortages in the Western Interconnect and,in some cases,very substantially.This result is representative of the interactions that happen interconnection-wide,demonstrating the advantage of modelling the entire interconnection.Production costs were decreased by the additional solar generation and the load change from TOU rates,and high response levels reduced the production costs the most for high-solar-generation cases.Load change from TOU rates decreased locational marginal prices for a typical summer day but had inconsistent results on a high-load day.Additional solar generation decreased the usage of combustion turbines,combined cycles and coal-fired generation.