Impact of Water Availability on Regional Power System Operations – A Case Study of ERCOT

Abstract:

Impact of water availability on regional power system operations – A case study of ERCOT

Thermal power plants are the largest single source of water withdrawals in the United States, mainly for cooling purposes. The amount of water that is required for cooling is highly dependent on a number of factors including the generation technologies being used, the temperature of the input water, and the total electricity load in the system. During summer months, many of these factors coincide to greatly increase the demand for water in a power system. Electricity demand typically reaches its annual peak when temperatures are high due to increased air conditioning loads. Ambient water temperatures also increase, meaning that greater quantities of water are required to provide the same amount of cooling at thermal generation plants. Finally, water availability is generally constrained due to seasonal effects and potential droughts. This raises concerns that water scarcity may lead to forced de-rating at some power plants during periods of peak demand, resulting in a more vulnerable and less reliable energy system. While increasing attention has recently been given to the inexorable link between water and energy, most commercial power models do not explicitly account for water use when optimizing system operation. We apply the AURORAxmp power modeling software to a case study analysis of the ERCOT power system to determine the water requirements of the system during periods of peak power demand. We then analyze water availability by location and time to identify potential supply shortages, which may reduce actual power generation availability. These data are fed back into the power systems model and specific generation units are de-rated as necessitated by water constraints. We then analyze these results to determine how the optimal generation mix, system reliability, and wholesale electricity prices may be affected by when the ERCOT power system is operated under water constraints.