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Archive for the ‘solar power plants’ Category

I wrote this story for Reuters, where it first appeared on November 30, 2010.

With NRG Energy’s announcement on Tuesday that it will invest $450 million investment in a California photovoltaic project, the New Jersey-based power provider has pledged a total of $750 million for big solar plants in the past two months.

A new report from GTM Research indicates why NRG sees such sunny prospects for the solar business. According to the researchers, utilities in the United States already have signed contracts for 5,400 megawatts’ worth of photovoltaic power plants that will be built by 2014 with another 10,100 megawatts in negotiation.

The U.S. utility-scale photovoltaic market is expected to grow from $1 billion in 2010 to $8 billion by 2015, the report said.

“The global PV industry is increasingly turning its attention toward the U.S. utility PV market as a driver of global demand over the next five years,” the report’s authors wrote. “Indeed, conditions appear right to support massive growth.”

That growth is being driven by a 50 percent fall in the price of photovoltaic modules since 2009 as well as state mandates that require utilities to obtain a certain percentage of their electricity from renewable sources.

The price of natural gas, though, will play a critical role in the competitiveness of solar power plants.

While solar farms can produce electricity at near-competitive rates with natural gas-fired power plants during peak demand in some states, the plunge in natural gas prices in recent years has put more pressure on photovoltaic developers to lower costs.

“From the perspective of the U.S. utility PV market, the importance of being within competitive range of a natural gas project is nearly as valuable as becoming cheaper, the report said. “In order for the U.S. utility market to take off, the key argument to be made by developers to utilities, and by utilities to their regulators, is that PV can deliver power at a competitive rate with other peaking facilities.”

No surprise that the largest solar market remains in California, where the state’s three big investor-owned utilities hold contracts for 78 percent of the nation’s 5,400 megawatt pipeline of projects.

But there is one dark cloud that threatens to rain on this photovoltaic parade: Project financing.

As part of the federal stimulus package, the government offered renewable energy developers the option of taking cash grants to cover 30 percent of a project’s costs in lieu of an existing investment tax credit. With the cash grant program expiring at year’s end, developers will have to turn to so-called tax equity investors who take the investment tax credit in exchange for cash to finance power plant construction.

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I wrote this story for Reuters, where it first appeared on November 30, 2010.

A subsidiary of NRG Energy on Tuesday said it will invest up to $450 million in a 250-megawatt photovoltaic power plant to be built by Silicon Valley’s SunPower on the central California coast.

The New Jersey-based power provider, which operates a fleet of fossil fuel and nuclear plants, has emerged as significant investor in solar projects.

In October, NRG agreed to invest $300 million in BrightSource Energy’s 370-megawatt Ivanpah solar thermal power plant now under construction in the Mojave Desert in Southern California. The company has also struck a partnership with eSolar, a Pasadena, Calif., startup, to build solar power plants in the desert Southwest. And NRG owns a 20-megawatt photovoltaic farm in Blythe, Calif., and has other solar projects under development in Arizona, California and New Mexico.

In the deal with SunPower, NRG Solar will take ownership of the California Valley Solar Ranch in San Luis Obispo County and responsibility for financing the project. SunPower said on Tuesday that it is seeking a federal loan guarantee to build the solar farm and has received a draft term sheet from the United States Department of Energy.

SunPower, a solar power plant developer and one of the U.S.’ largest manufacturers of photovoltaic modules, will build and operate the San Luis Obispo project. The company, based in San Jose, Calif., has a 25-year contract to sell the electricity generated by California Valley Solar Ranch to utility PG&E. Construction is set to begin next year and when the project is completed in 2013 it will produce enough electricity to power about 100,000 homes, according to the company.

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photo: Tessera Solar

I wrote this story for Reuters, where it first appeared:

The California Energy Commission has temporarily withdrawn approval of a controversial solar power plant by NTR’s Tessera Solar after opponents protested that the 663.5-megawatt Calico project had been improperly licensed.

California aims to get a third of its electricity from renewable energy by 2020 and the $2 billion plant is an important step toward that goal.

An attorney for California Unions for Reliable Energy had argued in a November 11 letter that the energy commission, which licenses large-scale solar thermal power plants, had not filed required written findings about Calico environmental consequences when it approved the project on October 28.

The order was issued late on Friday and the commission will take up the decision again on December 1, but the Sierra Club told Reuters on Monday that the environmental group may mount a legal challenge to Calico due to its impact on the imperiled desert tortoise, fringe-toed lizard and other wildlife.

“We are considering litigation,” Gloria D. Smith, a senior staff attorney with the Sierra Club in San Francisco, said in an email.

California Unions for Reliable Energy also is contemplating a legal challenge to the Calico decision on environmental grounds, said Marc D. Joseph, an attorney for the group.

Calico is one of seven huge solar thermal power plants that the energy commission has licensed over the past three months so developers can begin construction by the end of the year to qualify for a federal cash grant that covers 30 percent of a project’s cost.

Tessera has signed a contract to supply electricity generated by Calico to utility Edison International’s Southern California Edison, which is counting on the project to help it meet its renewable energy targets.

On Friday, Karen Douglas, the energy commission’s chairman, issued an order withdrawing the date approval would go into effect for Calico.

Douglas wrote that the decision did not mean that the commission agreed with the California Unions for Reliable Energy that the commission’s action had been improper.

Sean Gallagher, Tessera’s vice president of market strategy and regulatory affairs, described the issue as a procedural one that the commission could easily correct.

“There were some clerical errors in the way the documents were issued,” he said. “They are not going to address the substance of the decision.”

The company plans to deploy 26,540 solar dishes called Suncatchers at Calico. Resembling giant mirrored satellite receivers, each Suncatcher is 40 feet high and 38 feet wide and generates electricity by focusing the sun on a Stirling engine to heat hydrogen gas. As the gas expands, it drives pistons to generate electricity.

The commission approved Calico only after Tessera agreed to reduce its footprint nearly in half to 4,613 acres in Southern California’s Mojave Desert. The revised configuration would reduce the impact on the desert tortoise by 79 percent, the commission said.

But in an October 20 letter to the commission, Smith argued that even a downsized project would prove devastating to protected wildlife.

You can read the rest of the story here.

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photo: Amonix

I wrote this story for Reuters, where it first appeared:

As solar panel prices have plummeted over the past year, photovoltaic power plants have become a more attractive option for utilities under pressure to meet renewable energy targets.

Case in point: Late last week utility Southern California Edison announced it had signed contracts for 239.5 megawatts of electricity to be generated by 20 small-scale photovoltaic farms.

“Photovoltaics are definitely more cost competitive than they were just a couple of years ago,” said Mike Marelli, director of contracts for renewable and alternative power at Southern California Edison. “We’re seeing just a wild response to our solicitations for projects.”

The utility has inked deals in past years for huge solar thermal power plants that can generate 500 megawatts or more. But those projects — which focus large arrays of mirrors on liquid-filled boilers to generate steam that drives electricity-generating turbines –  need vast stretches of desert land.  Transmission lines must often be built or upgraded to carry the power to coastal cities.

The photovoltaic farms, ranging in size from five megawatts to 20 megawatts, are designed to be built near existing transmission lines or substations and plugged into the grid. And in California, for instance, photovoltaic power plants do not undergo the extensive environmental review required of big solar thermal projects, meaning they can be built much more quickly.

In the power purchase agreements reached last week, Southern California Edison also for the first time placed bets on a technology known as concentrating photovoltaics – -CPV — signing contracts for 28.5 megawatts of electricity to be generated by four projects using technology supplied by Amonix,  a Seal Beach, Calif., company.

Resembling supersized solar panels, each Amonix CPV power generator is 77 feet by 50 feet and produces 72 kilowatts of electricity by using plastic lenses to focus the sun on tiny but highly efficient solar cells.

The panels are more efficient than conventional photovoltaic modules but high production costs, technological challenges and other hurdles had kept CPV on the sidelines with just a few small installations operating around the world.

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photo: Todd Woody

I made my debut on Reuters on Thursday with a scoop on one of China’s biggest solar companies forming a joint venture with California’s SolarReserve to build photovoltaic power plants in the United States:

A subsidiary of China’s GCL-Poly Energy Holdings Ltd has formed a joint venture with SolarReserve, a California developer, to build photovoltaic power plants in the United States.

The deal, to be announced Thursday, marks a major bid by a Chinese solar company to enter a market dominated by European and U.S. firms. Last week, GCL obtained a commitment from Wells Fargo to provide $100 million in financing for its solar projects.

GCL is China’s largest manufacturer of polysilicon and wafers used to make photovoltaic modules. The company also builds conventional power plants in China along with wind and solar projects. The state-owned China Investment Corporation owns a 20 percent stake in GCL.

“We value the U.S. market as one of the most important markets for us and we wanted to get into the development side of the game,” Yumin Liu, president of GCL Solar Energy Inc, the company’s San Francisco-based subsidiary, said in an interview.

“To support the continued growth of the company we have to have a portfolio for years to come. The only way to do it economically is to secure a pipeline of projects.”

GCL will acquire a 50 percent share of SolarReserve’s 1,100-megawatt project pipeline in photovoltaics for an undisclosed price.

SolarReserve, based in Santa Monica, California, has focused on developing large solar thermal power plants using molten-salt technology licensed from United Technologies Corporation. This type of plant is not part of the joint venture.

Kevin Smith, SolarReserve’s chief executive, said the startup last year began to acquire control of 40 sites throughout the desert Southwest that would be suitable for smaller-scale photovoltaic-power projects. The company hired Macquarie Capital to search for a partner to share development costs.

“The U.S. market is a hugely competitive market on pricing, given the current policy structures and limited federal government support for renewable energy,” Smith said. “Partnering with a low-cost Chinese company gives us insight on how to maintain competitiveness in these markets and we will learn a trick or two.”

He said that SolarReserve will handle land acquisition, permitting and negotiating power purchase agreements with utilities while GCL will oversee procurement of solar panels and construction. Work on 400 megawatts’ worth of projects should begin in 2011.

You can read the rest of the story here.

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photo: Todd Woody

In The New York Times on Wednesday, I follow up my story on community solar power plants:

In an article in the special Energy section of The New York Times on Wednesday, I write about a developer who wants to sell “garden plots” in a 15-megawatt photovoltaic farm in Davis, Calif., so that residents can go solar without having to cut down trees in the city’s urban forest to install rooftop arrays.

While solar power plants seem like a 21st-century phenomenon, the Davis project dates from 1987, when the utility Pacific Gas and Electric built P.V.U.S.A. — Photovoltaics for Utility Scale Applications –- to test various nascent technologies.

Matt Cheney, a veteran renewable financier in San Francisco and founder of CleanPath Ventures, eventually acquired P.V.U.S.A. and received the city’s blessing to expand the power plant from around one megawatt to 15 megawatts.

Last week, I took a took a tour of the solar farm, a veritable outdoor Smithsonian of solar power displaying a dozen photovoltaic technologies. Some have become common sights on rooftops and at power plants while others barely left the laboratory before failing and bear the name of start-ups long gone.

Built on an abandoned wastewater treatment plant and surrounded by farmland on Davis’s outskirts, P.V.U.S.A. features two-story-high thin-film solar panel arrays that were on the technological cutting edge in their day but only became commercially viable in recent years.

Strips of early solar tiles designed to serve as power-generating roofing material are laid out on a wooden platform.

And behind rows of more conventional solar panels lies a field of what looks like photovoltaic sunflowers. Pods of 25 small mirrors designed to concentrate the sun on a high-efficiency photovoltaic cell suspended on a stamenlike strut.

“They installed them back in 2004 and 2005, and two months into the installation, it stopped working and the company didn’t want to deal with them anymore,” said Dang H. Dang, P.V.U.S.A.’s on-site manager, as jackrabbits darted among the arrays.

You can read the rest of the story here.

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photo: Todd Woody

In the New York Times on Wednesday, I follow up my story on solar power plants and desert tortoises:

In an article in The New York Times on Wednesday, I write about how the fortunes of big solar power plants in the desert Southwest can hinge on the way developers handle imperiled wildlife in the path of their projects.

The protected desert tortoise has become the totemic animal for environmentalists fighting to ensure that the huge solar farms don’t eliminate essential habitat for the long-lived reptile and other wildlife, like the bighorn sheep and flat-tailed horned lizard.

The tortoise has been in decline for decades, and the rampant changing of the desert — including the development of casinos, strip malls and subdivisions, and designation of off-road recreational vehicle areas — took its toll long before construction began late last month on the Ivanpah solar power plant, the first large-scale solar thermal project to be break ground in the United States in 20 years.

Still, the solar farms will industrialize the desert on an unparalleled scale. The seven projects already licensed in California will cover 42 square miles with immense mirror arrays.

But as much as some biologists fear that the need to generate electricity without carbon dioxide emissions will harm the desert tortoise, the projects offer an opportunity for intensive research on the critter. That’s because regulations require solar developers to monitor tortoises for three years after they are relocated.

“Certainly the monitoring of the translocated desert tortoises will yield useful research information on the ability of desert tortoises to adapt to new surroundings,” Larry LaPré, a wildlife biologist with the United States Bureau of Land Management, said in an e-mail.

Such data is critical. While environmental regulations and efforts by developers like BrightSource Energy, the builder of the Ivanpah project in Southern California, are tailored to remove the tortoise from harm’s way during construction, the survival of the animals depends on how well they adjust to their new homes.

The track record on tortoise relocations is not encouraging. In 2008, more than 700 tortoises were moved from the Fort Irwin military installation in Southern California so the base could expand. Nearly half the relocated tortoises died within two years from, among other things, predation by coyotes and ravens, according to state records.

Biologists I met recently at the Ivanpah power plant site were far more optimistic about the relocation of 23 tortoises found in the project’s first phase.

“The tortoises at Fort Irwin were moved a lot further than these, and there also was a big problem with predators there,” Peter Woodman, a biologist who worked on the military project, explained as he stood by a holding pen where the Ivanpah tortoises will live until they are moved next spring.

You can read the rest of the story here.

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photo: Todd Woody

In The New York Times special Energy report, I write about how the success of large-scale solar power plants being built in the desert Southwest depends on how developers deal with the imperiled desert tortoise and other wildlife:

NIPTON, Calif. — On the construction site of the $2 billion Ivanpah solar power plant here, burly laborers slowly walk around their trucks, dropping to their knees to peer underneath before turning the ignition. Hanging on each rearview mirror is a placard warning workers to “Look under your car for desert tortoise before you drive away!”

Road graders and backhoes crawl along at 10 miles per hour, led by biologists wearing green hard hats who scan for tortoises in a landscape studded with creosote bushes. “Nobody is allowed on the site without a biologist to escort them,” said Mercy Vaughn, the lead biologist for BrightSource Energy, the Oakland, Calif., company that is building the 370-megawatt power plant, the first large-scale solar thermal project to break ground in the United States in two decades.

The imperiled desert tortoise sets the pace here in the desert Southwest, and how developers deal with a host of protected plants and animals has become crucial to getting vast renewable energy projects built. That means hiring scores of biologists, managing the relocation of species and acquiring thousands of acres of replacement habitat.

With seven large solar power plants already approved that would cover 42 square miles of the California desert with huge mirror arrays, solar dishes and towers, environmentalists and regulators have increasingly become concerned about the impact that industrialization of the desert will have on fragile landscapes.

“If wildlife issues are not at the top of a developer’s list, they should be,” said Karen Douglas, the chairwoman of the California Energy Commission, which licenses large solar thermal power plants. “The footprint of these solar projects is unprecedented, and obviously they can impact a range of species.”

Developers underestimate the importance of desert animals at their peril.

The California Energy Commission in October, for instance, approved Tessera Solar’s huge Calico project in Southern California only after the company agreed to slash the project nearly in half to avoid having to relocate most of the 104 tortoises found on the site this year. And the commission’s staff has indicated that it is unlikely to recommend the licensing of Solar Millennium’s 250-megawatt Ridgecrest power plant because of its impact on the desert tortoise and the Mohave ground squirrel.

Late last month, the Quechan Indian Tribe sued the federal government over its approval of a second Tessera power plant, contending that the 709-megawatt Imperial Valley Solar Project would harm the flat-tailed horned lizard, an animal proposed for endangered species protection. It is part of the tribe’s creation story.

As the first big solar thermal power project to undergo licensing in 20 years and the first to begin construction, Ivanpah is being watched closely by environmentalists, regulators and competitors over how it handles wildlife challenges.

BrightSource, which is backed by Google, Morgan Stanley and several oil companies, has signed contracts to deliver 2,610 megawatts of electricity to utilities in the state. It took three years for the project to be licensed by the California Energy Commission as BrightSource and environmental groups tussled over the power plant’s impact on the desert tortoise, bighorn sheep and other species that roam the 3,582-acre site in the Mojave Desert.

BrightSource shrank Ivanpah by 12 percent, reducing the number of desert tortoises that would have to be relocated and avoiding an area of rare plants. The portion of the project that would most affect wildlife was cut by 23 percent.

The energy commission in September licensed Ivanpah over the objections of the Sierra Club, the Center for Biological Diversity and other groups that argued it would eliminate high-quality habitat for the tortoise.

“If you put a project in the wrong place and even do some things to reduce its impact, it’s still bad,” said Lisa Belenky, a senior lawyer with the Center for Biological Diversity in San Francisco. “We’re really trying to get companies and regulators focused on lands that have already been disturbed.”

The Ivanpah site is just over the Nevada border, about 40 miles southwest of Las Vegas. The neon glow of two hulking casinos looms in the distance. An incongruous patch of luminescent green marks an 18-hole golf course adjacent to the site.

“Everyone wants to do the right thing, but everyone is concerned because there are so many precedents that are being set since we’re the first ones through the hoop,” Todd Stewart, the Ivanpah project manager, said recently as he stood amid the desert scrub as biologists tracked a tortoise that had been outfitted with a radio transmitter. The orange and brown tortoise, which the biologists said was probably 30 to 40 years old, was about the size of a soccer ball.

By 2014, nearly six square miles of government-owned desert surrounding Mr. Stewart will be covered with 347,000 mirrors, each the dimension of a billboard. The mirrors will focus the sun on a three 459-foot towers topped by water-filled boilers to create steam that will drive turbines to generate electricity.

BrightSource executives take pains to point out that they designed Ivanpah to minimize its disturbance of the desert. Vegetation, for example, will be trimmed rather than plowed as equipment is installed.

Following conditions of its license, the company fielded an army of more than 50 biologists to capture and radio-tag tortoises in the 900-acre first phase of the project and ensure none were harmed as construction began.

You can read the rest of the story here.

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photo: Todd Woody

In The New York Times special Energy report, I write about how community solar power plants offer residents a chance to own photovoltaic arrays without putting panels on their roofs — or cutting down trees:

DAVIS, Calif. — In this environmentally conscious college town, thousands of bicyclists commute each day through a carefully cultivated urban forest whose canopy shields riders and their homes from the harsh sun of this state’s Central Valley.

The intensity of that sunshine also makes Davis an attractive place to generate clean green energy from rooftop solar panels. And therein lies a conundrum. Tapping the power of the sun can also mean cutting down some of those trees.

“Davis has spent many, many decades getting trees planted and improving energy efficiency by virtue of shade trees that cool houses,” said Mitch Sears, the city’s sustainability program manager. “But if you want solar energy, it’s not rocket science that you need the sun.”

Now a San Francisco company, CleanPath Ventures, is promoting a solution to allow homeowners to keep their trees and go solar at the same time. CleanPath plans to expand its existing solar farm on the city’s outskirts and then sell “garden plots” to homeowners who would own the electricity generated by their patch of photovoltaic panels. Apartment dwellers and other residents whose homes are not suitable for rooftop solar arrays would also be able to own a piece of the power plant.

“If you moved down the block, you’d take the electricity production with you just like if you make an investment in a community garden, wherever you live you’ll benefit from what’s grown in the garden,” said Matt Cheney, a longtime financier of renewable energy and the founder of CleanPath Ventures.

Community solar power plants are seen as a way to expand the availability of renewable energy while taking advantage of the economies of scale that result from installing thousands of solar panels in a central location rather than scattered on thousands of individual homes.

“To get the energy benefits of solar there’s no reason to drill holes in a roof,” said Jim Burke, manager of the SolarShares program for the Sacramento Municipal Utility District, which serves the region surrounding the state capital.

The utility, known as SMUD, started SolarShares, one of the nation’s first community solar-power-plant programs, in July 2008 when it offered customers the opportunity to buy electricity from a 1.2-megawatt photovoltaic power plant built on a turkey farm southeast of Sacramento.

“People love solar, but we required you to own a roof” and that it face a certain way, said Mr. Burke. “Multifamily buildings were usually excluded and renters were excluded.”

Then there was the tree issue.

“SMUD has planted hundreds of thousands of trees to shade rooftops and then with solar we’re saying cut them down,” he noted.

The SolarShares program gives customers the option of buying power from a half-kilowatt or a one-kilowatt portion of the solar farm. For instance, for a household that uses 2,158 kilowatt-hours a year, a one-kilowatt solar system would cover about 81 percent of their electricity consumption and cost $21.50 a month. However, the household would receive a monthly credit for the solar electricity produced that would average $13.96.

The pilot SolarShares program sold out within six months and there’s now a waiting list, according to Mr. Burke.

He said SMUD was planning a one-megawatt community solar-power plant that would be built next year and was exploring the placement of up to four megawatts of solar farms on highway rights-of-way owned by the state transportation agency.

Like a community solar farm in St. George, Utah, and a proposed solar garden in Falmouth, Mass., the CleanPath project in Davis would offer residents the chance to buy a physical part of a solar farm.

You can read the rest of the story here.

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photo: Todd Woody

I wrote this story for Grist, where it first appeared.

If you want a birds-eye view of the future of power, scramble up to the roof of a 562,089-square-foot warehouse in Ontario, a city that sits in the smoggy heart of Southern California’s Inland Empire east of Los Angeles.

On a roof the size of several football fields, workers are busy installing 11,591 solar panels that will generate 2.55 megawatts of electricity. Across the street is another massive warehouse blanketed in photovoltaic panels. Beyond that lie two more warehouses with solar arrays under construction.

Warehouses themselves use relatively little electricity, so owners lease their roofs to utility Southern California Edison, which own the solar arrays and feeds the power they produce into the grid. Over the next five years, the utility will install 250 megawatts worth of photovoltaic panels on big commercial rooftops and buy an additional 250 megawatts from solar developers that will build and operate warehouse arrays. At peak output, those solar arrays will generate as much electricity as a mid-sized fossil-fuel power plant.

“In the Inland Empire you’ve got big buildings and good sun,” Rudy Perez, manager of the utility’s solar rooftop program, said as we stood on the top of the warehouse where solar panels covered the roof as far as the eye could see.

He noted that the number of applications from solar developers to connect rooftop photovoltaic projects to the grid has tripled in the past six months alone.

“It’s one thing when you have one building in an area with a big solar array, another when you have five,” said Perez. “As you get into the higher and higher numbers, that’s where you really need smart grid technology.”

That’s because the rise of renewable energy and electric cars will vastly complicate how the power grid operates.

“We could literally have more change in the system in the next 10 years than we’ve had in the last 100 years,” Theodore F. Craver, Jr., chief executive of the utility’s parent company, Edison International, said in an interview after meeting with executives from French utility giant EDF. The French had come to Los Angeles to learn about Southern California Edison’s smart grid efforts.

In the current, mostly analog grid, the distribution of electricity is fairly straightforward. A utility or another company builds a fossil-fuel-powered plant and flips the switch. For the next 30 years or more, electricity flows into high-voltage transmission lines hour after hour, day after day.

The transmission lines carry the electricity to a distribution system where transformers “step down” the power to a lower voltage and then send it to homes and businesses. And though technological improvements have been made over the decades to the grid, it remains essentially a one-way system. And while storms and accidents can bring down power lines and blackouts can occur when demand soars on a hot day and electricity generation can’t keep up, power flows 24/7 from a natural gas or coal-fired plant.

Now consider the challenges posed by intermittent sources of electricity like solar and wind, not to mention the prospect of thousands of cars plugging into the grid at once to recharge their batteries.

“A rolling cloud can cut electrical output by 80 percent in a just few seconds,” says Perez. “That’s one reason why we have to be smart about where we put [solar].”

And why it’s necessary to build a digitalized grid that deploys software, sensors, and other hardware to monitor and manage electricity distribution and troubleshoot problems.

Instead of relying on dozens of big power plants, the smart grid of the future will increasingly tap thousands or millions of individual rooftop power plants and wind turbines. It will need to collect information about their electricity output and balance the flow of electricity throughout the grid — to ensure that a neighborhood doesn’t go dark because a large cloud is hovering over the solar array atop the local Costco.

“As we start to replace more of the generation with different technologies, we are altering the physics of the system,” said Pedro Pizarro, Southern California Edison’s executive vice president of power operations.

This drizzly October morning is a case in point. A ceiling of gray clouds hangs over the four Ontario warehouses that altogether would be generating some 7.59 megawatts if the sun were shining at peak intensity. So the smart grid also needs to be able to forecast the weather and know, say, that for the next few days electricity production is going to fall in one area while it might rise another, sun-splashed one.

“There’s new technologies that allow for much precise control of the grid,” Perez said. “One of the concerns would be that the intermittency of one of these buildings causes problem for our customers.”

Down the coast at the University of California, San Diego (UCSD), researchers have built what looks like a mirrored hemispherical bowl that scans the skies and snaps two photos a minute to predict when clouds will form over the campus’ one-megawatt worth of solar panels that are installed at seven locations.

“We do a 3-D characterization of all clouds on the horizon every 30 seconds,” Byron Washom, director of strategic energy initiatives at UCSD, said at a solar conference in October. “And then in the next second we note its vector, its speed, its height, its opacity and we characterize it.”

“So we actually begin to forecast what type of cloud is going to intersect where the sun is,” added Washom. “We know where it is at all times in the sky [in relation to] each individual panel on campus.”

He said the scientists’ goal is to be able to use the machines, which cost $12,000 apiece and have a range of one kilometer (0.62 miles), to do hourly forecasts with 90 percent accuracy.

“So a capital investment of less than $1 million could bring this to the Southern California rooftop market if we crack the science,” said Washom, referring to the concentration of warehouses in places such as Ontario.

Another smart grid strategy is to store energy generated by solar arrays in batteries and feed power to the grid when renewable energy production falls or demand spikes.

Washom showed a picture of a device that looks like the back end of a DVD player. The Sanyo lithium ion battery can store 1.5-kilowatt hours of electricity. UCSD plans to stack them like servers in a data center so it can store 1.5 megawatts of electricity produced by campus solar arrays.

In the San Francisco Bay Area, SolarCity, a solar panel installer, and electric carmaker Tesla Motors have received a $1.8 million state grant for a pilot project that will put lithium ion car batteries in half a dozen homes with rooftop solar arrays.

The Sacramento Municipal Utility District (SMUD), meanwhile, plans to install lithium ion batteries in 15 residences as part of its smart solar homes program. The utility will also put two 500-kilowatt batteries near substations to test energy storage on a larger scale.

Such systems are expensive but if the price eventually falls, utilities would be able to use them to release power to the grid when, say, a one of Washom’s cloud-forecasting devices predicts electricity production will fall off. (SMUD also will deploy 70 solar stations to help it forecast weather conditions that could affect electricity production, according to Mark Rawson, the utility’s project manager for advanced, renewable and distributed generation.)

So will the smart grid and increasing production of rooftop solar and other renewable energy spell the end of big centralized power stations and the multibillion-dollar transmission infrastructure? Will the future bring some sort of Ecotopian nirvana where power is put in the hands of the people (or at least on their rooftops)?

Not anytime soon, according to Pizarro of Southern California Edison, barring technological breakthroughs that dramatically reduce the cost of photovoltaic power.

“Right now solar is increasing but it’s not overwhelming the system,” says Pizarro, noting that rooftop photovoltaics remain a tiny percentage of the overall power supply even in places like California, where utilities must obtain a third of their electricity from renewable sources by 2020.

Still, renewable energy “has the potential to reduce the generation from central stations,” Pizarro said. “It’s a question of how much and how soon.”

The other wild card is the price of oil and natural gas, notes Craver, Edison’s chief executive. When the cost of natural gas — the dominant energy source in California — rises, renewable energy becomes more attractive. When natural gas prices plunge, as they have over the past couple of years, installing solar becomes far more expensive in relative terms.

At last month’s solar conference, SMUD’s Rawson said his utility currently relies on photovoltaics, or PV, for less than one percent of its electricity generation. But that will likely change dramatically in the years ahead, he says, as the smart grid evolves to handle the widespread distribution of solar power.

“We’re trying to change PV from something that is tolerated by the utility to something that is controlled by the utility,” he said.

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