Water Impacts of a Low-Carbon Electric Power Future: Assessment Methodology and Status

105

The United States (US) energy system is a large water user, but the nature of that use is poorly understood. To support resource comanagement and fill this noted gap in the literature, this work presents detailed estimates for US-based water consumption and withdrawals for the US energy system as of 2014, including both intensity values and the first known estimate of total water consumption and withdrawal by the US energy system. We address 126 unit processes, many of which are new additions to the literature, differentiated among 17 fuel cycles, five life cycle stages, three water source categories, and four levels of water quality. Overall coverage is about 99% of commercially traded US primary energy consumption with detailed energy flows by unit process. Energy-related water consumption, or water removed from its source and not directly returned, accounts for about 10% of both total and freshwater US water consumption. Major consumers include biofuels (via irrigation), oil (via deep well injection, usually of nonfreshwater), and hydropower (via evaporation and seepage). The US energy system also accounts for about 40% of both total and freshwater US water withdrawals, i.e., water removed from its source regardless of fate. About 70% of withdrawals are associated with the once-through cooling systems of approximately 300 steam cycle power plants that produce about 25% of US electricity.

Section: Introductionmentioning

confidence: 99%

Water Use in the United States Energy System: A National Assessment and Unit Process Inventory of Water Consumption and Withdrawals

Grubert

Sanders

2018

105

“…The water system module embedded in the IECM estimates cooling water consumption at power plants based on mass and energy balances with the inputs such as fuel type, cooling technology, and ambient climate conditions. IECM has been used extensively in previous studies ,,,, to estimate the water use at various stages of the entire fuel life cycle. In this study, we focus on the plant operation stage involving cooling water consumption that usually accounts for more than 90% of the total life-cycle water consumption.…”

Section: Methodsmentioning

confidence: 99%

Seasonal Risk Assessment of Water–Electricity Nexus Systems under Water Consumption Policy Constraint

Zhang

Cai

et al. 2020

Previous studies have estimated power plant cooling water consumption based on the long-term average cooling water consumption intensity (WI: water consumption per unit of electricity generation) at an annual scale. However, the impacts of the seasonality of WI and streamflow on electricity generation are less well understood. In this study, a risk assessment method is developed to explore the seasonal risk of water−electricity nexus based on the Integrated Environmental Control Model, which can simulate variable WIs in response to daily weather conditions and avoid underestimation in WIs as well as nexus risk during dry seasons. Three indicators, reliability, maximum time to recovery, and total power generation loss, are proposed to quantify the seasonal nexus risk under water consumption policy constraint represented by the allowed maximum percentage of water consumption to streamflow. The applications of the method in two representative watersheds demonstrate that the nexus risk is highly seasonal and is greatly impacted by the seasonal variability of streamflow rather than annual average water resources conditions on which most previous studies are based. The nexus is found more risky in the watershed with almost double mean annual streamflow and greater streamflow variability, compared with the watershed with less streamflow variability.

“…The operational water use for the electric power sector has been reported and calculated for individual combinations of technology/fuel and cooling type, − for current electricity generation mixes, , and future scenarios of electric power at various scales. − Assessments of future electric sector water use commonly leverage scenarios incorporating CO 2 emissions reductions using various modeling platforms (several articles provide comprehensive reviews of these studies − ). Under climate mitigation scenarios, operational withdrawals typically fall relative to the base year.…”

Section: Introductionmentioning

confidence: 99%

Scenarios for Low Carbon and Low Water Electric Power Plant Operations: Implications for Upstream Water Use

Dodder

Barnwell

Yelverton

2016

Electric sector water use, in particular for thermoelectric operations, is a critical component of the water-energy nexus. On a life cycle basis per unit of electricity generated, operational (e.g., cooling system) water use is substantially higher than water demands for the fuel cycle (e.g., natural gas and coal) and power plant manufacturing (e.g., equipment and construction). However, could shifting toward low carbon and low water electric power operations create trade-offs across the electricity life cycle? We compare business-as-usual with scenarios of carbon reductions and water constraints using the MARKet ALlocation (MARKAL) energy system model. Our scenarios show that, for water withdrawals, the trade-offs are minimal: operational water use accounts for over 95% of life cycle withdrawals. For water consumption, however, this analysis identifies potential trade-offs under some scenarios. Nationally, water use for the fuel cycle and power plant manufacturing can reach up to 26% of the total life cycle consumption. In the western United States, nonoperational consumption can even exceed operational demands. In particular, water use for biomass feedstock irrigation and manufacturing/construction of solar power facilities could increase with high deployment. As the United States moves toward lower carbon electric power operations, consideration of shifting water demands can help avoid unintended consequences.