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.

Craig Miller

The California coast near Pigeon Point.

When ocean explorer and documentary filmmaker Jean-Michel Cousteau brought his environmental message to Silicon Valley, I caught up with him to discuss climate change; President Obama’s energy policy efforts; and AB 32, California’s response to climate change.

Jean-Michel Cousteau is the son of legendary ocean explorer, Jacques Cousteau, and chairman of Ocean Futures Society, a non-profit dedicated to exploring, protecting and educating people about the world’s oceans. He was vocal in condemning BP for its Gulf oil spill and has frequently highlighted the link between climate change and the state of our oceans and coastline.

A native of France, he now calls Santa Barbara home and describes California’s response to climate change – its Global Warming Solutions Act (AB 32) and proposed cap and trade system – as steps in the right direction. But he also explained why we need to do a lot more.

“It’s an issue of understanding and changing our ways,” he said. “Creating new ways of serving our needs and taking care of the environment at the same time.”

He’s talking specifically about renewable energy and points out that algae are fueling US Navy ships and commercial airliners. He emphasizes the advances being made in solar and wind energy and even cites a hotel in Bora Bora that is using temperature differences in the ocean depths to power its air conditioning system — all this without petroleum and its hefty environmental impact.

Alison van Diggelen / Fresh Dialogues

The son of Jacques Cousteau considers himself the "voice of the ocean."

Surprisingly, despite his dives to examine the BP oil spill devastation in the Gulf of Mexico, Cousteau still had good things to say about Big Oil, pointing out that oil companies like Shell, Total and BP are investing in renewable energy.

“Traditional industries are coming to understand that whether it’s nuclear [or] traditional oil and gas, in the end it’s going to be in their best interests to slowly adopt other ways of collecting energy, renewable energy,” he said.

He also emphasized that Americans are consuming more energy per capita than anywhere else in the world and that before we criticize other heavy CO2 emitters, like China, we must look closer to home.

So, in the ocean explorer’s view, is President Obama doing the right thing in response to climate change?

“He really has to convince our decision makers, in government and in industry, that things have to change,” he said and even offered his assistance to the president.

“If I can help I will do that,” he said.

He’s done it before. Cousteau made former President George W. Bush an unlikely environmental hero, at least in the mid-Pacific. In 2006, Cousteau showed Voyage to Kure, his documentary about the Northwestern Hawaiian Islands, (co-produced by KQED Public Television) at the White House. Shortly after, Bush designated the 140,000 square mile stretch the world’s largest marine conservation area.

If he gets to revisit the White House this year and discuss climate change and energy policy with President Obama, he might be wise to repeat his father’s mantra: “The impossible missions are the only ones which succeed.”