Water management has become critical for thermoelectric power generation in the US. Increasing demand for scarce water resources for domestic, agricultural, and industrial use affects water availability for power plants. In particular, the population in the Southwestern part of the US is growing and water resources are over-stressed.The engineering and management teams at the Palo Verde Generating Station (PV) in the Sonoran Desert have long understood this problem and began a partnership with Sandia National Laboratories in 2017 to develop a long-term water strategy for PV. As part of this program, Sandia and Palo Verde staff have developed a comprehensive software tool that models all aspects of the PV (plant cooling) water cycle. The software tool – the Palo Verde Water Cycle Model (PVWCM) – tracks water operations from influent to the plant through evaporation in one of the nine cooling towers or one of the eight evaporation ponds.PV is the largest nuclear power generation plant in the US. With a net average generation of more than 3600 MW of electricity, the plant requires evaporation of more than 65 Million gallons of water per day (65 MGD). PV is also the only commercial nuclear plant in the world that is not located near a large natural body of water. As such, PV purchases reclaimed water from the city of Phoenix and surrounding municipalities. This water is then treated in PV’s tertiary treatment plant to ensure the various salt concentrations are low enough that effective operation of the cooling towers is maintained.The PVWCM has been developed using a process called System Dynamics. The flow rate and chemical makeup of influent, as well as PV’s tertiary water treatment is simulated in the Water Reclamation Facility sub-model. The Power Conversion sub-model simulates the conversion of heat to electricity, using an empirical model for efficiency as a function of temperature and relative humidity. The Cooling Loop sub-model performs mass and energy balances to determine the evaporation rate of water in the cooling towers. Cooling water chemistry is maintained by blowdown to PV’s 650 acres of evaporation ponds. Blow down flow is optimized, and evaporation rates calculated by the evaporation pond sub-model to determine time dependent inventory levels. In addition to these sub-models, power generation and costs for all aspects of PV water operations are calculated. The PVWCM is developed to allow scenario comparison for various plant operating strategies.

The Palo Verde Water Cycle Model (PVWCM) – Development of an Integrated Multi-Physics and Economics Model for Effective Water Management

Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2021/volume/85109

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