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.

By Thibault Worth

Craig Miller/KQED

As the nation's power plants age, a new report warns against relying too much on natural gas.

The nation’s power plants are aging. An increasing number require replacement parts; others can’t keep up with new environmental regulations.

A report released today [PDF] by the Boston-based think tank Ceres estimates that in the next two decades, up to $100 billion will be invested in the electric utility industry every year – twice the amount invested in recent years.

According to the report, that boom in investment will take place in a shifting regulatory environment. Air pollution and greenhouse gas restrictions will increase, and fossil fuel-burning power plants will have to keep up. Governments are setting requirements for energy from renewable sources. (California, for example, is targeting a 33% renewable energy ratio by 2020.) Smart grids and new consumer technologies are changing how people think about energy production and consumption.

The good news is that the industry is growing, and will have an unprecedented chance to clean up its act. The bad – or cautionary – news is that state regulators will face increasingly complex investment challenges and pressures to make short-term fixes when they need to be thinking long-term.

A prime example is the recent expansion of the natural gas-fired power plant fleet across the country. Public utilities and private energy companies have been applying for permits to build natural gas power plants in record numbers, in part because of the current low cost of natural gas, in part because many regulators believe they are a solution to the inherent fluctuations in renewable energy sources such as wind and solar. But over-investment in natural gas would be a “folly” says Denise Furey, a co-author of the Ceres study.

“The problem with natural gas is that it is a commodity and subject to price fluctuations.”

If the price of natural gas goes up, so will electricity prices for consumers. And we’ll be stuck with a bunch of fossil fuel-burning plants that contribute to climate change.

The report’s authors say it is important that state regulators remain risk-aware, and diversify energy baskets over the long term.

On page 16 of the measure, Prop 10 specifically allocates multi-million-dollar grants to each of eight cities in California. Los Angeles, San Diego, Long Beach, Irvine, San Francisco, Oakland, Fresno and Sacramento (listed in that order) would each get $25 million:

“…for the purpose of capital projects and operating expenses promoting and demonstrating the actual use of alternative and renewable energy in park, recreation and cultural venues, including the education of students, residents and the visiting public about these technologies and practices.”

Seems straightforward enough–except nobody seems to know how these eight cities were chosen. It’s not merely a list of the state’s eight largest cities. It’s close, except that San Jose (#3) is conspicuously missing but Irvine (#17) makes the cut.

John Dunlap, former head of the state Air Resources Board and a paid consultant to the Prop 8 campaign, appeared to be stumped when I asked him for the rationale. His best  guess was that they might be locations with significant transportation infrastructure, such as major port facilities. Again, the mystery of Irvine…and Fresno isn’t quite the Rotterdam of the West Coast.

I called the official office of “Yes on 10” and a media representative told me that she thought the cities were chosen for “geographic distribution” but admitted that she hadn’t been asked before. She promised to get back to me with a definitive answer. That was last week. Election Day is tomorrow. If Prop 10 goes down to defeat, it won’t matter. If it passes, it’ll be even more important to have an answer.