Two great energy-water nexus reports from Claudia Copeland and Nicole T. Carter of the Congressional Research Service:
1) Energy-Water Nexus: The Water Sector’s Energy Use (Copeland and Carter - updated 24 January 2017)
Download CRS_Water_Sector_Energy_Use_24Jan2017
2) Energy-Water Nexus: The Energy Sector’s Water Use (Carter)
Download CRS_Energy_Water_Nexus_Energy_Sectors_Water_Use
Summaries of each report follow.
Summary No. 1: Energy-Water Nexus: The Water Sector’s Energy Use
Water and energy are resources that are reciprocally and mutually linked, because meeting energy needs requires water, often in large quantities, for mining, fuel production, hydropower, and power plant cooling, and energy is needed for pumping, treatment, and distribution of water and for collection, treatment, and discharge of wastewater. This interrelationship is often referred to as the energy-water nexus, or the water-energy nexus. There is growing recognition that “saving water saves energy.” Energy efficiency initiatives offer opportunities for delivering significant water savings, and likewise, water efficiency initiatives offer opportunities for delivering significant energy savings. In addition, saving water also reduces carbon emissions by saving energy otherwise generated to move and treat water.
This report provides background on energy for facilities that treat and deliver water to end users and also dispose of and discharge wastewater. Energy use for water is a function of many variables, including water source (surface water pumping typically requires less energy than groundwater pumping), treatment (high ambient quality raw water requires less treatment than brackish or seawater), intended end-use, distribution (water pumped long distances requires more energy), amount of water loss in the system through leakage and evaporation, and level of wastewater treatment (stringency of water quality regulations to meet discharge standards). Likewise, the intensity of energy use of water, which is the relative amount of energy needed for a task such as pumping water, varies depending on characteristics such as topography (affecting groundwater recharge), climate, seasonal temperature, and rainfall. Most of the energy used for water-related purposes is in the form of electricity. Estimates of water-related energy use range from 4% to perhaps 13% of the nation’s electricity generation, but regional differences can be significant. In California, for example, as much as 19% of the state’s electricity consumption is for pumping, treating, collecting and discharging water and wastewater.
Energy consumption by public drinking water and wastewater utilities, which are primarily owned and operated by local governments, can represent 30-40% of a municipality’s energy bill. At drinking water plants, the largest energy use (about 80%) is to operate motors for pumping. At wastewater treatment plants, aeration, pumping, and solids processing account for most of the electricity that is used. Energy is the second highest budget item for these utilities, after labor costs, so energy conservation and efficiency are issues of increasing importance to many of them. Opportunities for efficiency exist in several categories, such as upgrading to more efficient equipment, improving energy management, and generating energy on-site to offset purchased electricity. However, barriers to improved energy efficiency by water and wastewater utilities exist, including capital costs and reluctance by utility officials to change practices or implement new technologies.
Topics for research to better understand water-related energy use include studies of energy demands for water at local, regional, and national scales; development of consistent data collection methodology to track water and energy data across all sectors; development and implementation of advanced technologies that save energy and water; and analysis of incentives, disincentives, and lack of incentives to investing in cost-effective energy or water efficiency measures.
Summary No. 2: Energy-Water Nexus: The Energy Sector’s Water Use
Water and energy are critical resources that are reciprocally linked; this interdependence is often described as the water-energy nexus. Meeting energy-sector water needs, which are often large, depends upon the local availability of water for fuel production, hydropower generation, and thermoelectric power plant cooling. The U.S. energy sector’s use of water is significant in terms of water withdrawals and water consumption. In 2005, thermoelectric cooling represented 41% of water withdrawn nationally, and 6% of water consumed nationally. The majority of the anticipated increase in water consumption by 2030 is attributed to domestic biofuel and oil and gas production. Policy makers at the federal, state, and local levels are faced with deciding whether to respond to the growing water needs of the energy sector, and if so, which policy levers to use (e.g., tax incentives, loan guarantees, permits, regulations, planning, or education). Many U.S. energy sector water decisions are made by private entities, and state entities have the majority of the authority over water use and allocation policies and decisions.
For fuel production, water is either an essential input or is difficult and costly to substitute, and degraded water is often a waste byproduct that creates management and disposal challenges. U.S. unconventional oil and gas production has expanded quickly since 2008, and U.S. natural gas and coal exports may rise. This has sparked interest in the quantities of water and other inputs “embedded” in these resources, as well as the wastes produced (e.g., wastewaters from oil and gas extraction). Much of the growth in water demand for unconventional fuel production is concentrated in regions with already intense competition over water (e.g., tight gas and other unconventional production in Colorado, Eagle Ford shale gas and oil in south Texas), preexisting water concerns (e.g., groundwater decline in North Dakota before Bakken oil development), or regions with abundant, but ecologically sensitive surface water resources (e.g., Marcellus shale region in Pennsylvania and New York).
Conventional hydropower accounts for approximately 8% of total U.S. net electricity generation, and more than 80% of U.S. electricity is generated at thermoelectric facilities that depend on cooling water. Water availability issues, such as regional drought, low flow, or intense competition for water can curtail hydroelectric and thermoelectric generation. An assessment of the drought vulnerability of electricity in the western United States found broad resiliency, while also identifying the Pacific Northwest and the Texas grid at higher risk. Future withdrawals associated with electric generation may grow slightly, remain steady, or decline depending on a number of factors. These include reduced generation from facilities using once-through cooling because of compliance with proposed federal cooling water intake regulations or shifts in how electricity is generated (e.g., less from coal and more from wind and natural gas).
Energy choices represent complex tradeoffs; water use and wastewater byproducts are two of many factors to consider when making energy choices. For many policymakers, concerns other than water—low-cost reliable energy, energy independence and security, climate change mitigation, public health, and job creation—are more significant drivers of their positions on energy policies.
Enjoy!
Thanks to Jan Schoonmaker for sending these my way.
"Analyses quickly get complex when attempting to comprehensively evaluate energy-water tradeoffs." - Nicole T. Carter, Energy-Water Nexus: The Energy Sector’s Water Use, p.10
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