Ecocentricity Blog: The Energy-Water Collision

I haven’t used my unbearably lazy and unimaginative “let’s play a game” opening in quite some time, so how about we dust it off? You can play if you want to, or don’t, whatevs. I really have no way of knowing. I’m just trying to make a deadline here.

Let’s play a game! I’ll tell you, according to 2015 Department of the Interior data, how many gallons of water are used in the United States every day (about 322 billion), and you tell me which of eight use categories (aquaculture, domestic, industrial, irrigation, livestock, mining, public supply, and thermoelectric power) is responsible for the highest percentage of that use.

Hmmmmmm. Yep, I just successfully asked the worst trivia question ever. I mean, seriously, that sentence is just impossible to read. Look, scratch the “let’s play a game” thing, and I’ll just tell you - the amount of water used to generate thermoelectric power (think coal/natural gas/nuclear) is just bananas.

From Table 2A in the report I linked to above, we use 132.9 BILLION gallons of water a day on thermoelectric power generation. It’s responsible for 41% of all the water we use in this country.

A couple of disclaimers are worth noting here. First, if we looked at just freshwater, then thermoelectric power would finish second to irrigation (118 billion gallons per day vs. 95.1 billion gallons per day). Keeping our lights on/air cold/gadgets working still accounts for 34% of freshwater withdrawals though. Second, a lot of the water used for electricity generation does get put back from whence it came. There’s a problem with that too though, and to highlight it, I should probably explain why our power plants are so thirsty.

Thermoelectric power plants either burn something (fossil fuels) or split something (atoms) to generate lots and lots of heat. The heat then makes water boil, and the resulting steam turns a turbine, creating electricity. While water is needed for the steam, that’s not actually how most of the water is used. Instead, power plants need all that H2O as coolant, allowing the steam to condense before running through the turbines again.

The problem is this pesky thing called the first law of thermodynamics, which applies the law of the conservation of energy to thermodynamic systems. Stated simply, if you use cold water to cool hot steam, that cold water will warm up. Because…duh.

Unfortunately, lots of aquatic lifeforms don’t like it when power plants dump hot-tub water into their habitats. The term for these disruptive discharges is “thermal pollution.” Such discharges are often regulated, but that means that power plants will have to limit power production or shut down if their discharge water is too warm.

Relatedly, sometimes the water is too hot in the first instance to be effectively used as coolant. Know when that is? Yep – in the heat of the summer, which will only get worse as our planet warms. Another challenge for thermoelectric plants? Droughts…..like the kind also predicted to be more frequent as the climate changes.

The Union of Concerned Scientists calls this “The Energy-Water Collision.” There’s good stuff in that article, so take a look. I’ll bottom-line it though – conserving energy and transitioning to renewable energy helps solve multiple problems, not the least of which are our water challenges.

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