Energy and Water: Check Your Water Footprints at the Door, Please

Whenever we waste energy, we waste water.

Courtesy: utsa.edu

(NOVATO, Calif.) - Carbon gets all the press. But more and more scientists are starting to figure out that it takes so much water to create energy, and so much energy to move water, that whenever we talk about the carbon footprint of energy, we really should be talking about its water footprint as well.

Here's why: Except for wind and photovoltaic solar found on rooftops, most power plants big or small do one simple thing: They boil water. That's it.

The water then makes steam, which spins a turbine, which runs a generator, which creates electricity in a way that is almost miraculous.

But with that miracle comes a price: Water. Lots and lots of it.

No matter if it is coal powered, or nuclear, or oil or even large scale solar, all that heat has to be cooled down. Thus the water. It takes at least a gallon of water to create one kilowatt hour of power - enough to run your air conditioner for one hour.

The numbers tell the tale: Rachelle Hill and Dr. Tamim Younos of Virginia Tech University estimate that “fossil fuel thermoelectric plants use between … 8 to 16 gallons of water to burn one 60-Watt light bulb for 12 hours per day. Over the duration of one year this one incandescent light bulb would consume about 3,000 to 6,300 gallons of water.”

That's a lot of water for a little bit of light. Other household appliances are just as thirsty: A central air conditioner running for 12 hours a day will drink up 16,800 gallons of water every year at the power plant. A laptop computer uses 200 gallons a year. A coffee maker perking two hours a day needs 672 gallons of water every year to brew that cup of Joe.

Different types of power plants require different amounts of water. Coal and oil plants need about a gallon or two per kilowatt hour. Hydropower plants in the Northwest, for example, need 18 gallons for the same amount of energy. Power plants in Arizona use 7 gallons per kilowatt hour.

In California, 49 percent of all the water withdrawn in the state is used for energy. Much of the water used to cool power plants is returned to the river or ocean whence it came, true enough. But not before killing billions and billions of fish and marine mammals every year. Not before a lot of it evaporates.

All that happens just at the power plant. Take one step back to the mine or the oil field, and every day, billions of gallons of water are consumed coaxing energy from beneath the earth. The amount varies from the one gallon of water it takes to extract a gallon of oil from conventional means, to up to 350 gallons of water for every gallon when the oil is harder to find.

That is still only half the picture. It also takes a tremendous amount of energy to move, treat, and ultimately dispose water. In California, 20 percent of the energy in the state is used to move water. So we use water to create energy, and we use energy to create water -- to create more energy to create more water. And on and on and on it goes in a downward spiral that completely distorts the way we think and act about water and power.

Whenever we waste energy, we waste water. Big transmission lines, for example, that carry energy from the thirsty power plants to energy-hungry refrigerators and light bulbs hundreds of miles away leak energy like a sieve. They lose 7 percent of their juice before lighting a single bulb.

That's not just wasting power, its wasting water too.

Not all power plants create heat. Photovoltaic solar panels - the kind found on roofs and backyards and schools and wineries and farms and roads and office buildings and hotels - create electricity, not heat.

So except for a few spritzes to wash them off, they do not need water. But they do need a magnifying glass if you want to see their water footprint.