Energy/electricity production & water are linked very closely – you need water to produce energy, and energy is used to deliver us fresh water.
In this guide, we look at the water footprint and water efficiency of the different energy sources for electricity production.
Summary – Water Efficiency Of Energy Sources For Electricity Production
Water is also used from other direct and indirect activities in electricity production other than the operation stage – such as for mining and extraction of energy sources, cleaning, processing, waste disposal, and so on
There’s a difference between water withdrawals and water consumption – water consumed means the water isn’t returned to it’s source and it permanently used up, whereas water withdrawn may be returned to it’s sources or re-used
When looking at water use per one megawatt hour of electricity produced (according to various reports) …
Solar thermal with wet cooling, coal, nuclear and natural gas use the most water.
Some biofuels also tend to be high water users
Wind uses the least, followed by solar thermal with dry cooling, and solar photovoltaic.
Hydroelectric and geothermal can also be water efficient if considering water withdrawals vs water consumption
Renewable energy sources allow electricity production essentially eliminate water use at the operation stage (although there’s water used for cleaning solar panels, and in evaporation for hydro power)
Some sources indicate that the most water efficient energy production methods in terms of per Btu produced, are natural gas and synthetic fuels produced by coal gasification
There are variables at play for water efficiency of different energy sources, which can change results
Measuring according to BTUs produced as opposed to Megawatts of electricity can also change results
At the consumer level, burning a fluorescent bulb saves a significant amount of water compared to burning a incandescent one
Some potential solutions to better water efficiency in electricity production might include upgrading coal power plants with newer water efficient systems, having closed loop water systems for cooling in thermal power plants, dry cooling, making better use of salt water compared to fresh water, investing in water efficient technology, and the obvious one – using energy sources that are more water efficient than others
How Electricity Generation Uses Water
In most power plants, water cools the steam that spins the electricity-generating turbines.
Almost all major sources of electricity rely to some degree on water.
Most power plants generate heat from their fuel (by burning coal or natural gas, for example, or by maintaining a fission reaction), and use that heat to boil water, produce steam, and turn turbines.
Water is also used during various stages of energy-related resource extraction, processing, and waste disposal.
– ucsusa.org (read more about how the different electricity generation methods require and use water here)
Water usage is one of the most obvious environmental impacts of electricity generation.
All thermal cycles (coal, natural gas, nuclear, geothermal, and biomass) use water as a cooling fluid to drive the thermodynamic cycles that allow electricity to be extracted from heat energy.
Other energy sources such as wind and solar use water for cleaning equipment, while hydroelectricity has water usage from evaporation from the reservoirs.
How Much Water Electricity Uses In The United States Every Year
They also discuss other environmental impacts, such as the impact on wildlife.
Important notes are:
Because of the large amount of water required by thermoelectric plants, total US withdrawals for thermoelectric power accounted for 41 percent of total water withdrawals in 2015 (the most recent year data is available).
That added up to 133 billion gallons per day, most of which were from surface water sources and 72 percent of which were from freshwater sources like lakes and rivers.
Power plants that used once-through cooling systems accounted for 96 percent of all withdrawals for thermoelectric power.
Water Footprint Of Different Energy/Electricity Production Sources
The water use by power plants, in terms of water consumed to produce one megawatt hour of electricity (which is enough to power 1000 homes) is:
Solar thermal with wet cooling – 786 gallons
Coal – 687 gallons
Nuclear – 672 gallons
Natural gas – 198 gallons
Solar photovoltaic – 26 gallons
Solar thermal with dry cooling – 26 gallons
Wind – 0 gallons
As a side note – Roughly 90 percent of the energy [the US used in 2013 came from] nuclear or fossil fuel power plants.
Coal, nuclear and natural gas plants use enormous amounts of steam to create electricity.
Producing all of that steam requires 190,000 million gallons of water per day, or 39% of all freshwater withdrawals in the nation [as of 2013]
Using renewable energy technologies such as wind and photovoltaics means doing away entirely with water use for electricity production
[one piece of research studied the] water-efficiency of some of the most common energy sources and power generating methods
… 11 types of energy sources, including coal, fuel ethanol, natural gas, and oil; and five power generating methods, including hydroelectric, fossil fuel thermoelectric, and nuclear methods
… [the most water efficient energy sources in gallons of water per British Thermal Unit (BTU) are] natural gas and synthetic fuels produced by coal gasification … [and] The least water-efficient energy sources are fuel ethanol and biodiesel
… in terms of power generation … geothermal and hydroelectric energy types use the least amount of water, while nuclear plants use the most.
[what is interesting is] burning a compact fluorescent bulb for the same amount of time [as an incandescent one] would save about 2,000 to 4,000 gallons of water per year
[results should be taken lightly because] several variables such as geography and climate, technology type and efficiency, and accuracy of measurements that come into play.
However, by standardizing the measurement unit, we have been able to obtain a unique snapshot of the water used to produce different kinds of energy
How To Reduce Water Footprint In Energy/Electricity Production
Some ideas might include having closed loop water systems for cooling in thermal power plants, making better use of salt water compared to fresh water, investing in water efficient technology, and using energy sources that are more water efficient.
Ucsusa.org has these recommendations:
Retrofit existing coal power plants with new water efficient systems and technology could double water efficiency
Use more water efficient energy sources like solar and wind in the future for our energy