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NOTICEThis report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Executive SummaryThis report provides estimates of operational water withdrawal and water consumption factors for electricity generating technologies in the United States. Estimates of water factors were collected from published primary literature and were not modified except for unit conversions. The presented water factors may be useful in modeling and policy analyses where reliable power plant level data are not available. Major findings of the report include:• The power sector withdraws more water than any other sector in the United States and is heavily dependent on available water resources. Changes in water resources may impact the reliability of power generation.• Water withdrawal and consumption factors vary greatly across and within fuel technologies. Water factors show greater agreement when organized according to cooling technologies as opposed to fuel technologies. Once-through cooling technologies withdraw 10 to 100 times more water per unit of electric generation than recirculating cooling technologies; recirculating cooling technologies consume at least twice as much water as once-through cooling technologies.• A transition to a less carbon-intensive electricity sector could result in either an increase or decrease in water use, depending on the choice of technologies and cooling systems employed. Concentrating solar power (CSP) technologies and coal facilities with carbon capture and sequestration (CCS) capabilities have the highest water consumption values when using a recirculating cooling system. Non-thermal renewables, such as photovoltaics (PV) and wind, have the lowest water consumption factors.• Federal datasets on water use in power plants have numerous gaps and methodological inconsistencies. Federal agencies are currently coordinating to improve these data. Water use factors discussed here are good proxies for use in modeling and policy analyses, at least until power plant level data improve.

Water use by the electricity sector represents a significant portion of the United States water budget (41% of total freshwater withdrawals; 3% consumed). Sustainable management of water resources necessitates an accurate accounting of all water demands, including water use for generation of electricity. Since 1985, the Department of Energy (DOE) Energy Information Administration (EIA) has collected self-reported data on water consumption and withdrawals from individual power generators. These data represent the only annual collection of water consumption and withdrawals by the electricity sector. Here, we compile publically available information into a comprehensive database and then calculate water withdrawals and consumptive use for power plants in the US. In effect, we evaluate the quality of water use data reported by EIA for the year 2008. Significant differences between reported and calculated water data are evident, yet no consistent reason for the discrepancies emerges.

Techno-ecological synergies of solar energy produce outcomes that mitigate global change Abstract | The strategic engineering of solar energy technologies-from individual rooftop modules to large solar energy power plants-can confer significant synergistic outcomes across industrial and ecological boundaries. Here, we propose technoecological synergy (TES), a framework for engineering mutually beneficial relationships between technological and ecological systems, as an approach to augment the sustainability of solar energy across a diverse suite of recipient environments, including land, food, water, and built-up systems. We provide a conceptual model and framework to describe 16 TESs of solar energy and characterize 20 potential techno-ecological synergistic outcomes of their use. For each solar energy TES, we also introduce metrics and illustrative assessments to demonstrate techno-ecological potential across multiple dimensions. The numerous applications of TES to solar energy technologies are unique among energy systems and represent a powerful frontier in sustainable engineering to minimize unintended consequences on nature associated with a rapid energy transition.

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