Energy-Water Nexus

Water and energy, both necessary for life, are linked. Large amounts of water are needed for electricity generation; for example in the process of generating electricity from coal, water is used for extraction, processing, fuel conversion and cooling. Similarly a large amount of electricity is needed for extraction, treatment, and distribution of water. Up to now water and energy issues have been considered independently, but the increasing scarcity and cost of each will demand that they be considered together.

A study found that water requirements for electricity generation vary greatly depending on the primary energy source and the conversion and cooling technologies used. The biggest users are bioenergy from dedicated energy crops, hydroelectric facilities and thermoelectric facilities using once through cooling. Waste based facilities, solar photovoltaic, wind turbines and thermoelectric facilities using dry cooling use the least water.

Major water efficiencies can be achieved using technologies that target water efficiencies. Dry cooling and coal gasification can decrease California’s projected 2020 scenario for annual freshwater withdrawal and consumption by 66%; and by adding more water efficient technologies such as solar photovoltaic, wind and waste based bioenergy a 90% reduction is projected.

The study concluded:

  • Water efficient electricity generation requires the right mix of primary energy sources, conversion technologies and cooling technologies. Utilities must plan to invest in such water efficient technologies as wind, solar photovoltaic and coal gasification.
  • Policies that encourage water conservation can make a big impact. Such polices may include:

- Issuing conservation credits to power utilities that implement programs to reduce water use.

- Co-locating water treatment plants and power plants to facilitate the use of reclaimed water.

Further study is needed on the full life cycle of electricity generation including the construction of the power plant to understand the full water requirements of electricity generation.

Issues to be considered in the integration of water and electricity planning include:

  • The transition to more water efficient means of electricity generation must be accomplished in a manner that will not compromise energy reliability.
  • In addition to the impacts of water on electricity generation, planning must include other environmental impacts such as habitat, ecosystems and biodiversity.
  • Impacts on water resources may be regional as seen in the bioenergy sector. For example some areas that have plenty of water may be more viable for production of dedicated energy crops.

Source: “California’s Energy-Water Nexus: Water Use in Electricity Generation

By Cheryl Weiden, Feb 03 2012


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