Posts Tagged ‘Sacramento Municipal Utility District’

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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photo: PG&E

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

Amid the hullabaloo over government-chartered mortgage giants derailing the green financing program known as Property Assessed Clean Energy, or PACE, the march toward distributed generation of renewable energy — that is, generating electricity from decentralized sources such as rooftop solar panels or backyard wind turbinescontinues.

Case in point: The Sacramento Municipal Utility District (SMUD) announced Wednesday that it had awarded contracts to San Francisco’s Recurrent Energy to install 60 megawatts’ worth of solar panels in the region surrounding California’s state capital.

Rather than construct a central solar power station, Recurrent will scatter a dozen five-megawatt installations around two cities in Sacramento County. Each installation will be located near an existing substation, which means that the solar arrays can be plugged directly into the grid without requiring any expensive transmission upgrades.

As I wrote earlier this year in Grist, when SMUD put 100 megawatts of renewable energy contracts out for bid, the allocation sold out within a week. The utility is paying the solar developers a standard premium for their photovoltaic energy — called a feed-in-tariff. But according to calculations done by Vote Solar, a San Francisco non-profit that promotes solar energy, SMUD will pay no more for this clean green solar electricity than it does for fossil-generated power at peak demand times. A 40-percent plunge in solar module costs over the past year has made solar photovoltaic energy increasingly competitive with natural gas, the main fossil fuel used in California to generate electricity.

California’s two big investor-owned utilities, PG&E and Southern California Edison, have launched similar distributed generation programs, which will bring 1,000 megawatts of photovoltaic installations online over the next five years. At peak oputput, that’s the equivalent of a nuclear power plant.

Two weeks ago, PG&E cut the ribbon on the first project to come online as part of its 500-megawatt distributed generation initiative. The two-megawatt Vaca-Dixon Solar Station is built near a utility substation 50 miles north of San Francisco.

It took just nine months to install the fields of solar panels for the Vaca-Dixon station — that’s light speed in a state where the first new big solar thermal power plant in 20 years, BrightSource Energy’s Ivanpah project, has been undergoing licensing for nearly three years.

Solar thermal power plants generate electricity by using mirrors to focus the sun on a liquid-filled boiler. The process creates create steam that drives a conventional turbine which can generate hundreds of megawatts of electricity. Solar thermal projects, by nature, are large centralized facilities, the clean and green versions of a big fossil-fuel power plant.

Photovoltaic farms, on the other hand, generate electricity when sunshine strikes semiconducting materials in a solar cell. If you want to produce more power, you just keep adding solar panels.

While BrightSource hopes to secure a license for its solar thermal project soon, the developer of a hybrid biomass solar trough power plant to be built in California’s Central Valley pulled the plug on the project last month, after spending 18 months and untold millions of dollars in the licensing process before the California Energy Commission.

PG&E has been depending on both those solar thermal projects to supply electricity to help it meet its renewable energy mandates. No wonder then, the utility’s growing enthusiasm for solar panel power. Photovoltaic farms do not have to be approved by California Energy Commission and can be built on already degraded land or close to cities.

And as I reported last month, the developer of another project being built to generate electricity for PG&E, the Alpine SunTower, decided to drop solar thermal technology made by its partner, eSolar, in favor of photovoltaic panels. The official explanation for the switch was that project was being downsized due to transmission constraints and solar panels proved a better fit.

But one has to wonder if economics as much as energy was behind the change. If so, deals like the one SMUD struck could be a recurrent theme.

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