power plants


The Water That Fuels California’s Power Grid

How many gallons to run that microwave?

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.

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EPA’s New Carbon Rule Doesn’t Do Much in CA

California enacted similar limits to pollution from power plants in 2006

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.

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CA Power Plants Must Find New Cooling Methods

California’s electrical power generators will be scrambling for new ways to cool their turbines, now that state regulators have ordered a phase-out of  “once-through cooling.” The practice, which has been under study by regulators since at least 2005, requires sucking in billions of gallons of cold ocean or river water and then returning it at higher temperatures. Nineteen major power plants across the state, including California’s only two commercial nuclear plants, are currently using once-through cooling.

Sea water used for cooling at Diablo Canyon nuclear power plant. Photo: Craig Miller

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.

Creating Carbon Sponges

Carbon capture demo at the annual American Geophysical Union meeting. Credit: Molly Samual.

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.