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.

BrightSource Energy

Solar-thermal plants use mirrors or "heliostats" to focus sunlight on a tower receptor that produces steam to generate electricity.

A major barrier for solar power has always been that it doesn’t work at night (Duh). A few years ago, developers of big “utility-scale” solar projects were able to shrug this off to some degree. But Oakland-based BrightSource Energy has reversed field and decided to add to several projects the ability to store electricity for distribution after dark.

BrightSource managers say times have changed. Where utilities once wanted all the renewable capacity they could get, to meet state requirements, the priority has since shifted to having those renewable electrons available when they’re needed.

“The challenges of integrating photovoltaics and wind into the grid have driven a much deeper appreciation for those that can be highly reliable,” BrightSource CEO John Woolard told me in a phone interview.

But another driver is — well — us. When I interviewed Woolard a couple of years ago, I asked him why his company wasn’t including storage technology in its California projects. He said it wasn’t needed in California, which had a different pattern of electrical use than, say, Arizona.

That’s changing. Woolard says peak demand, which has traditionally hit around 4 p.m., has been shifting to later in the day, and by the end of this decade, will probably happen around 6 p.m. He says changing lifestyles are behind the shift, such as when people arrive home and fire up their air conditioners and other appliances.

BrightSource says it will use a molten-salt technology to store the power, rather than huge banks of batteries or experimental technologies such as flywheels. “That’s a solution for 2050 or 2060,” Woolard told me, “depending on whether you’re an optimist or a pessimist.”

Here’s a good summary of how it works, from The Energy Blog:

“The molten salt, with properties like water at temperatures above its 240^oC (464^oF) melting point, is pumped from a large storage tank to the receiver, where it is heated in tubes to temperatures of 565^oC (1049^oF). The salt is then returned to a second large storage tank, where it remains until needed by the utility for power generation. At that time, the salt is pumped through a steam generator to produce the steam to power a conventional, high-efficiency steam turbine to produce electricity. The salt at 285^oC (545^oF) then returns to the first storage tank to be used in the cycle again.”

BrightSource will add molten-salt units to three of its projects in Riverside and San Bernardino Counties, but not to its Ivanpah Valley project, already under construction near the Nevada border. Spokesman Keely Wachs says that the added cost will be “fairly nominal,” and that expanding the plants’ operating hours will, in effect, reduce the price of energy from those plants.

CEO Woolard says that despite plunging prices for conventional photovoltaic solar panels, BrightSource will not be joining a trend among developers to convert some of their giant solar arrays to PV. He says PV output tends to peak at noon (PV power is a function of light, not heat), so their output is falling just as demand is rising. He says that by adding storage capacity to solar-thermal plants such as his,”You can extend when you deliver power and and you’re delivering more of it when the real system peak is.”

Gretchen Weber

Construction of one of three planned solar thermal towers at the Ivanpah Solar Electric Generating System, Ivanpah Dry Lake, CA

Construction of the Ivanpah site is reportedly on-schedule for completion in 2013

The National Clean Energy Summit 4.0 opens in Las Vegas on Tuesday, bringing policy makers and industry leaders from around the country together to “chart the course for the future of energy in America.” It’s also attracting lots of media, which is why on Monday Oakland-based BrightSource Energy opened the gates to the construction site of its 3,500 acre Ivanpah Solar Complex, which lies just over the California border, 45 minutes southwest of the Las Vegas Strip.

About 15 reporters donned hard hats and safety goggles in 100-plus temperatures to tour the active construction site in the Mojave Desert, along with officials from BrightSource, San Francisco-based construction company Bechtel Corp., and NRG Energy, which, along with Google, is the project’s main investor.

Touted as the the largest solar thermal plant under construction in the world today, the 370-megawatt array is expected to power 140,000 homes when it’s completed in 2013.  BrightSource officials say that will double the total solar thermal capacity of the entire United States, and increase the world’s supply by about a third.

Gretchen Weber

Ivanpah constuction from a distance

The site will eventually consist of three towers more than 450-feet tall and 53,000 “heliostats” dotting the surrounding acreage. Heliostats are the mirrors that focus the sun’s energy onto a boiler at the top of the tower, creating the heat necessary to generate steam and energy.

BrightSource’s Carlos Aguilar said that by employing a technology called dry cooling, which uses air to cool the plant instead of water, the site will use 97% less water than it otherwise would have. The project is slated to use about 100 acre-feet of water per year, which, he said, is about the amount used by 300 homes in a year.

“Three-hundred homes’ worth of water use for 140,000 homes’ worth of energy is quite a trade-off,” said Aguilar.

Another low-impact environmental strategy at the site includes efforts to keep the natural contours of the land intact, in order to keep the natural drainage system functioning.  And according to BrightSource CEO John Woolard, because the plant is 50% more efficient than a photovoltaic installation, it’s able to encompass a smaller footprint.

“We’ve got probably the lowest environmental impact of any technology out there in solar,” said Woolard.

Gretchen Weber

That hasn’t stopped activists from organizing pickets outside the company’s headquarters in downtown Oakland. Ivanpah has been the target of some environmental groups arguing that the solar installation threatens the endangered desert tortoise.  In April, the Bureau of Land Management shut down construction on two sections of site when more tortoises were found on-site than expected. But in June, after further environmental review, the agency granted permission for work to resume. On Monday, Bechtel and BrightSource officials said the project is on schedule.

The event was an unusually high-profile affair for BrightSource of late, as the company is preparing for an initial public offering of stock and is in an SEC-enforced “quiet” period.

The federal Bureau of Land Management today issued its first approvals of major solar energy projects in California.

The Tessera project will use "SunCatchers" to concentrate solar power. (Image: Tessera Solar)

Tessera Energy’s 700-megawatt Ocotillo project, located in the Imperial Valley, about 100 miles east of San Diego, and a smaller photovoltaic (PV) project by San Ramon-based Chevron Corp., are both cleared to go forward.

The two projects set a precedent not just for California. On a call with reporters this morning, Department of Interior Secretary Ken Salazar called it a “historic day,” saying the two projects “bear the distinction of being the first large-scale solar energy projects ever approved for construction on our nation’s public lands.”

For projects being developed on federal land, BLM approval is the final hurdle before construction can begin. Big solar-thermal projects, which concentrate the Sun’s energy to make steam, also require approval from the California Energy Commission (photovoltaic projects, like the Chevron array, are under the eyes of the state’s Pubic Utilities Commission and county governments). State energy commissioners have approved seven major solar installations in the California desert since July. Several of these are still pending BLM approval.

BLM director Robert Abbey uses the catch phrase “smart from the start” to describe his agency’s new approach to site permitting, which he calls “streamlined without cutting corners.” Abbey says the Bureau is still sifting through a backlog of 180 pending applications, nationwide.  He said his agency manages about 23 million acres “with solar potential,” across several western states, about half of that in California.

The Tessera project, shown in some CEC filings as SES Solar Two, could deliver more than 700 megawatts of solar-thermal power when completed late next year. It will occupy more than 6,000 acres of BLM land, and a few hundred acres of adjacent private land. Chevron’s Lucerne Valley project is significantly smaller, rated at 45 megawatts, with a footprint of about 400 acres in the Lucerne Valley of San Bernardino County.

Asked about opposition from environmentalists, Salazar said the projects had won support from several major organizations, including Defenders of Wildlife, the Sierra Club, The Wilderness Society and Natural Resources Defense Council (NRDC).

In a press release, NRDC attorney Johanna Wald wrote that: “the process provided valuable lessons that careful planning, siting and designing up front will lead to renewable projects that are smart from the start.”

Salazar told reporters that transmission lines are already available for all of the Chevron project’s output and a little less than half the expected output from Ocotillo, and that he looks forward to seeing “thousands of megawatts of renewable energy sprouting” over the next few years.