How many gallons to run that microwave?

Lauren Sommer / KQED

A natural gas power plant in Long Beach that uses "once-through" cooling.

We hear a lot about how green our energy is in California. Instead of using coal, the state runs on natural gas and increasingly, renewable power.

But there’s a hidden cost to our energy supply: water use. In fact, every time you turn on a light, it’s like turning on your faucet. It’s been calculated that it takes 1.5 gallons of water to run a 100-watt light bulb for 10 hours.

The way water and power work together is a lot like a tea kettle. Steam drives the power industry.

How Power Needs Water

You can see it at the Gateway Generating Station, a natural gas power plant in the northeast Bay Area. The plant looks complicated but making power is pretty simple. Step number one: burn natural gas. That produces a lot of heat.

“You’ve got 1,700-degree exhaust energy, or waste heat,” says Steve Royall of PG&E, who is giving me a tour through the maze of pipes and compartments. The heat hits pipes that are filled with water and the water is boiled off to create steam. That’s step number two: make steam to turn a steam turbine, which is attached to a generator. It’s the water that’s making the power.

Source: National Renewable Energy Laboratory. Illustration by Andy Warner.

But water has another job in power plants. That steam, even after it makes power, is still hot. So, most power plants use water to cool it down. “You’ve got to have the ability to cool everything down so the cycle can continue and your equipment doesn’t overheat,” says Royall. (Learn more about how power needs water in this illustration).

Nuclear plants and coals plants use water the same way, in some cases, millions of gallons a year. In fact, nationwide, power plants need more freshwater than farms do, according to a U.S. Geological Survey study.

Newer power plants reuse water, but a lot of it is lost to evaporation, which means it has to be replenished. “Typically water has been the most abundant resource available,” says Royall, “but as water resources become more valuable, it’s extremely important that we think about water use.”

Future of Water Scarcity

“There is a general understanding that the era of abundance is over,” agrees Heather Cooley of the Pacific Institute, an Oakland-based think tank focused on water issues.

“Water resources are limited and there is a growing demand. We have growing population in the West. We have a growing economy.”

And then there’s the climate – which is changing. “The climate models suggest that water availability will be more variable. So we’ll have wetter years, we’ll have drier years. We’ll have a smaller snowpack,” says Cooley. In some places, power plants are already feeling the effects of tightening water supplies.

Power plants can cut their water impact by using recycled water. “We can look at less water-intensive renewable energy systems. So looking at wind and at solar panels,” says Cooley.

But it turns out, some renewables need water, too.

Solar Technology Grapples with Water Costs

In a parched corner of California’s Mojave Desert, construction equipment shimmers in the mid-day heat. These 3,500 acres near the Nevada border are the site of the Ivanpah Solar Project.

“The Ivanpah project, when it’s operational, will be the largest solar thermal project operating in the world,” says Joseph Desmond with BrightSource Energy.

You’ll notice he said “solar thermal,” a technology that’s different than the solar panels you see on rooftops. The plant is a huge field of mirrors that are specially angled to focus the sun’s heat at a tower, 400 feet tall.

“Inside the top of that tower is a boiler. All of the energy is then is used to create high temperature, high pressure steam in excess of 1,000 degrees Fahrenheit,” says Desmond.

That spins a steam turbine that makes electricity. Just like a natural gas plant, that steam has to be cooled back down, which is normally done with water. In the desert, it’s not easy to find. “You have to dig down, I want to say about 840 feet,” says Desmond.

The Ivanpah solar project under construction. (Photo: BrightSource Energy)

So, the Ivanpah plant will use a new technology called “dry cooling.” Instead of using water, the plant uses massive fans to blow air over the pipes of hot steam. “Air cooling allows us to reduce the water consumption by as much as 90%,” says Desmond.

But there’s a catch. Dry cooling uses more energy, so the plant’s not as efficient. It’s even less efficient when it’s hot out.

It also costs more to build. “It can range between one and five percent more. Now, that may not seem like a lot but when you’re competing and every penny counts, it’s an important factor,” Desmond says.

Three of the seven solar thermal plants planned in California won’t use dry cooling. But Desmond says, even though the state needs renewable power, he doesn’t think agencies would approve that today. “I think it’s safe to say if somebody said we’d like to use water cooling, that getting a permit for that would be challenging to say the least.”

The same could be true for fossil fuel plants, too, as California’s future water supply is called into question more and more.

Explore the Water and Power series and hear Lauren’s radio story on KQED’s The California Report.

SAUL LOEB/AFP/Getty Images

The EPA's new rule limits carbon emissions from new power plants nationwide.

The US Environmental Protection Agency will, for the first time, begin restricting greenhouse gas emissions from fossil fuel-fired power plants. The EPA’s new standard limits how many pounds of carbon can be emitted per megawatt-hour of electricity generated. It doesn’t apply to existing power plants or to new plants that have already been permitted, and natural gas-powered plants should be able to meet the standard without changes. But coal-powered plants will no longer make the cut without adding carbon capture and sequestration technology.

This won’t have much of an effect on California’s energy industry, Dave Clegern from the California Air Resources Board told me, though he’s not complaining. “It’s always good to see a national standard, and we’re glad the EPA is doing it.”

Former governor Arnold Schwarzenegger signed a similar standard for power plants in California back in 2006. The state gets very little electricity from coal-powered plants, and the coal-fired power California residents do use comes from outside of California.

“The EPA kind of levels the playing field for us,” Clegern said. “Now everyone will be operating with a standard that’s pretty close to ours.”

Read more:

• Washington Post: EPA imposes first greenhouse gas limits on power plants
• Politico: EPA unveils greenhouse gas standard for new power plants
• Associated Press (via NPR): Administration To Propose New Power Plant Rules
• Grist: The top five things you need to know about EPA’s new carbon rule

Sea water spews from an outlet after being used for cooling at PG&E's Diablo Canyon nuclear power plant. Photo: Craig Miller

Prior to Tuesday’s vote by the Water Resources Control Board, the head of that body’s ocean unit testified that once-through cooling systems kill 2.6 million fish, 19 billion fish larvae and 57 seals, sea lions and sea turtles each year, Dow Jones reported.

According to the Board’s summary:

“The proposed policy establishes technology-based standards to implement federal Clean Water Act section 316(b) and reduce the harmful effects associated with cooling water intake structures on marine and estuarine life.”

The rules require that companies phase out the practice and install equipment that reduces impact on marine ecosystems within the next several years.  Some generators have warned that the high cost of complying with the regulations could force them to shut some plants down.

For more on the practice of “once through cooling” and its effects on marine life, listen to Amy Standen’s Quest radio report from Monday.

Carbon capture demo at the annual American Geophysical Union meeting. Photo: Molly Samuel

Almost lost amid the Copenhagen media clutter was last week’s meeting of the American Geophysical Union in San Francisco. So this week we’re playing a little catch-up. Lauren Sommer has the second of three posts on things that caught our attention at AGU.

Carbon capture technology has largely focused on the most convenient emissions sources–namely the stacks at large power plants. But as Columbia University’s Allen Wright showed at the American Geophysical Union conference in San Francisco last week, there are other ways to do it.

Wright and colleagues demonstrated their “air capture” technology, where carbon dioxide is absorbed straight from the air by something that looks a lot like a gadget for cleaning Venetian blinds. It’s a special plastic material with a sponge-like consistency. Once the carbon is absorbed, the material is exposed to water or water vapor which causes the carbon to be released. It can then be captured. Wright says it captures CO2 three to five times better than a leaf in full sunlight.

On a large scale, this technology might be built into “artificial trees” that could be stationed anywhere around the globe. The prototype, designed by Wright’s Global Research Technologies, doesn’t look much like a tree. It’s a shipping container with a circular, rotating basket on top where the air capture units are exposed to the air. After one rotation, the baskets would be brought “downstairs” where the carbon is captured. From there, the carbon could be geologically sequestered or even used to make beverages bubbly.

Of course, the main criticism of this approach is efficiency. Carbon dioxide is only about 0.04% of the atmosphere, which is why more concentrated sources like power plant stacks get more attention. Wright says capturing carbon from power generation will be important, “but capture at the stack isn’t enough. It won’t do what has to be done. Air capture has the advantage of being able to deal with emissions from anywhere on the planet from any source.”

Cars are one of the sources he’s talking about. Their prototype unit is designed to capture a ton of carbon a day, which would neutralize the emissions from about 20 cars. They hope to get the cost of each carbon-capturing unit down to the price of car, so the cost of reducing a ton of carbon could one day be similar to other technologies.

Still, to make an impact on global emissions, millions of these units would need to dot the landscape. And just as with renewable energy, NIMBY issues are a potential roadblock. But as is a common refrain these days, Wright says if we’re serious about cutting emissions, we’ll need every technology that shows promise.