California’s Water Emergency – A Solution Worth Considering

by the TESV folks in California

When considering options for energy production in drought stricken geographies like California, nuclear energy plants such as The San Onofre Nuclear Generating Station (SONGS), should be highlighted for the role they can play in meeting our energy needs, while not consuming an abundance of freshwater resources. During its operation, SONGS conserved approximately 126,548 gallons of freshwater per hour and produced enough energy to desalinate 668 trillion gallons of water a year. (2 million acre-feet.)

Ninety percent of the electricity produced in the United States comes from fossil fuel and nuclear power plants, which require large quantities of water for cooling steam (that is used to spin turbines that generate electricity) back to water that can be reused in the electricity generation process. Each type of power plant requires different amounts of water for cooling. For example, once-through cooling systems (such as the one used at SONGS) for nuclear power plants consume 400 gallons/MWh, coal power plants consume 300 gallons/MWh, and natural gas power plants consume 100 gallons/MWh. Once-through systems most commonly use freshwater from rivers, lakes, or aquifers, thus consuming water that could be used for agriculture, industry, and residential consumption. However, some power plants built near the ocean, like the SONGS, incorporate seawater into their once-through cooling system and require very little freshwater, leaving valuable water resources available for other purposes.

During its operation, SONGS produced 19% of the power used by Southern California Edison customers, supplying power to large portions of Southern California. Operating at full capacity from 1984-2011, units 2 and 3 of SONGS had a gross capacity of 1,127 MW and supplied on average 7,592 GWh of electricity a year and required the use of very little freshwater resources. The negative impacts of SONGS closure on the environment is already being realized. Carbon dioxide emissions from California’s power generation facilities increased from 30.7 million tons in 2011 to 41.6 million tons in 2012 in part due to the early closure of SONGS. Furthermore, millions of gallons of water that could be used for a multitude of other purposes have been used in fossil fuel energy production processes to replace the electricity once produced by SONGS. During its operation, SONGS conserved approximately 126,548 gallons of freshwater per hour (see calculations and assumptions below) that would have been used to produce the same amount of energy from other sources.

Furthermore the energy produced by SONGS could have been used in other ways to address water scarcity issues in California. For example, the average energy supplied through SONGS could have desalinated 668 trillion gallons of water a year, (2 million acre-feet) assuming it takes 3kWh to desalinate one cubic meter of water. That is enough water produced each year to supply San Diego’s population of over 3 million people with 119 gallons of freshwater (San Diego County’s daily average per capita) every day for five years.

Producing water locally would have also saved a considerable amount of energy that is required to pump water from reservoirs to Southern California. It requires on average 2908 kWh of energy to supply Southern California with one acre-foot (326,700 gallons) of water. Therefore during an average year, SONGS could have desalinated enough water locally, saving 5948 GWh of energy a year that would otherwise be required to pump water to Southern California.

Freshwater Conservation Calculations and Assumptions

Assuming the majority of the energy produced at SONGS would be used by Southern California Edison (SCE) customers, SCE’s energy mix can be used to determine what proportion of energy sources would be needed to make up for the loss of 7592.9 GWh of electricity SONGS supplied on average each year.

 SCE Energy Mix for 2006 (the most recent energy mix data):

  • Natural Gas: 54%

  • Coal: 8%

  • Nuclear: 17%

  • Large Hydro: 5%

  • Renewables: 16%

If energy production was ramped up proportionally across the energy mix of the SCE, each energy source would need to produce the following additional energy:

  • Natural Gas: 4,100.166 GWh (54% of 7,592.9)

  • Coal: 607.432 GWh (8% of 7,592.9)

  • Nuclear: 1290.793.59 GWh (17% of 7,592.9)

  • Large Hydro: 379.645 GWh (5% of 7,592.9)

  • Renewables: 1214.864 GWh (16% of 7,592.9)

According to the Nuclear Energy Institute, natural gas, coal, and nuclear consume the following amount of freshwater to produce electricity:

  • Natural Gas: 100 gallons MWh

  • Coal: 300 gallons MWh

  • Nuclear: 400 gallons MWh

Which would result in the following freshwater consumption a year:

  • Natural Gas: 410,016,600 gallons (4,100,166 MWh * 100 gallons MWh)

  • Coal: 60,743,200 gallons (607,432 MWh  * 300 gallons MWh)

  • Nuclear: 129,079,300 gallons (1,290,794 MWh * 400 gallons MWh)

  • Total: 1,108,563,400 gallons

Therefore during its operation in 2006, SONGS conserved 1,108,563,400 gallons of freshwater a year or 126,548 gallons of water an hour, that would have otherwise been used by other power generation processes to produce the same amount of energy.

So if you’re thinking that San Onofre Nuclear Plant should not have been closed then you get it.

2 thoughts on “California’s Water Emergency – A Solution Worth Considering

  1. Tim Skoglund

    In paragraph four you state, “it takes 3kWh to desalinate one cubic foot of water.”, with a link to a Wikipedia article which gives the volume of water as ‘one cubic meter’.

    One cubic foot of water is ~7.48 U.S. gallons (liquid). One cubic meter of water is 264.17
    U.S. gallons (liquid).

  2. Dr A. Cannara

    Good post, with the correction. The Calif. Legislature & administration officials have failed us, for many years — long droughts were predicted many years ago, the need to reduce combustion power was explained many years ago, and yet we have combustion-industry folks giving $ to naive protesters trying to shut down our cleanest, most reliable power sources: San Onofre & Diablo Canyon.

    I guess we might expect such from a state that passed Prop 8, almost passed Prop 23 and passed a bill allowing “personal choice” to endanger our kids by voiding immunizations — a bill that the Legislature now says it will repeal.

    The unfinished work for our Governor, CEC, CPUC & Legislature is to call Ohio and ask who fixed Davis-Besse for FirstEnergy, so that it could eliminate a few coal plants’ emissions — emissions that our foolish closure of SONGS has now added in the Four Corners coal-burning stations & local gas plants…
    “Davis-Besse nuclear power plant is operating again after undergoing a $600 million upgrade. FirstEnergy spent the last 3 months replacing the two original steam generators at the plant near Toledo.”… or:

    Of course, we in Calif. are used to wasting $billions on flashy stuff. But wasting $7.7billion on ruining SONGS takes the cake.


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