Okay, I’m a little slow on the uptake on this but I’ve been pursing a recent report from Lawrence Berkeley Laboratory on the effect of installing a rooftop solar array on the sale price of homes in California.

(It makes for dense reading and unless you’re really into “hedonic pricing models” and “difference-in-difference model,” you might want to stick with the two-page summary.)

The upshot: California homes that sport solar panels sell for a $17,000 premium for an average newish 3.1-kilowatt photovoltaic array.

“This is a sizable effect,” Ryan Wiser, a staff scientist at the Lab and a coauthor of the report, said in a statement.  “This research might influence the decisions of homeowners considering installing a PV system and of home-buyers considering buying a home with PV already installed.”

Similar studies have been done previously, but the Berkeley report is apparently the first to analyze the statewide real estate market. California is by far the nation’s largest solar market, with some 100,000 rooftop systems installed. About 90 percent of those have been put on residential roofs, according to the report.

The scientists analyzed California 72,000 home sales from 1999 to 2009. Nearly 2,000 of those homes had solar panels at the time of sale.

“When the dataset is split between new and existing homes, PV system premiums are found to be markedly affected … with new homes with PV demonstrating average premiums of $2.3 to 2.6/watt, while the average premium for existing homes with PV being more than $6/watt,” wrote the authors.

Translation: Buy a house in a new subdivision where solar comes standard and your home values could rise between around $7,000 and $8,000. Purchase an older home with a solar array and the value rises by $18,000 or more. (That’s assuming a 3.1-kilowatt array has been installed.)

The authors speculated that the disparity might be explained by differences in installation costs and homebuilders’ willingness to discount the price of solar systems in bid to increase sales.

The report notes that the relative premium commanded by solar panels on a home drops as the system ages and its efficiency declines.

And why would a prospective homeowner be willing to pay a premium for a house with solar panels on the roof, beyond green bragging rights? For the same reason the existing owner probably installed the system: Lower electricity bills, the report concludes.

It was a sunny year at the 2011 Coachella Music Festival, and the stage is set for the town’s new concentrating photovoltaic farm.Photo: Paige K. ParsonsAn interesting solar development got buried by Thursday’s big news that French fossil fuel conglomerate Total had agreed to acquire a majority stake in SunPower, the Silicon Valley photovoltaic panel maker and power plant development.

That $1.37 billion Total is spending on SunPower naturally overshadowed the Southern California desert community of Coachella’s announcement that it had flipped the switch on a 420-kilowatt concentrating photovoltaic farm at its water reclamation plant.

Don’t yawn. Here’s why the project is innovative, both in its use of technology and the business model.

Electricity payments typically account for 30 percent of a wastewater plant’s operation and maintenance costs (and such facilities consume three percent of the nation’s power — who knew?), according to the United States Environmental Protection Agency.

Coachella’s solution to rising electricity costs was found on a patch of degraded city-owned land thought to be of little value.

But now Coachella is leasing the land to Solar Power Partners, which developed the photovoltaic farm with Johnson Controls. It buys back the solar electricity, which offsets 40 percent of the electricity demand at the water reclamation plant.

“By installing the new solar energy system utilizing the latest technology available at our water reclamation facility, the city and SPP will power this critical city resource in a manner that will greatly reduce our operating expenses,” Coachella’s mayor, Eduardo Garcia, said in a statement.

The city was able to wring quite a bit of power out of a relatively small strip of land, thanks to the deployment of concentrating photovoltaic arrays made by SolFocus, a Silicon Valley startup.

The 55 arrays use lens to concentrate the sun onto tiny, ultra-efficient solar cells mounted in panels on large pedestals that track the sun throughout the day. That boosts electricity production while minimizing environmental impacts on the land. The catch: The technology must be deployed in areas with intense sunshine — i.e. the desert.

While that means you won’t see SolFocus arrays in Seattle or San Francisco, they’re good news for Coachella. Check ‘em out if you head south for next year’s Coachella music festival. 

Now that we’ve put together some green muscle, what will we do with it?Photo: Denis Giles

California, as usual, is heading down a different road. The enviro-business coalition that defeated Prop 23, Texas oil companies’ attempt to derail the state’s global-warming law, is stepping up effort to push lawmakers to expand California’s climate-change efforts.

First, the No on 23 campaign led by billionaire hedge-fund manager Tom Steyer resurfaced last month as Californians for Clean Energy and Jobs.

On Tuesday, a second group, the Silicon Valley-based Clean Coalition, emerged to press a similar agenda in an effort it calls the Clean California Campaign. “The Campaign promotes policies to meet Gov. Jerry Brown’s call to install 12,000 megawatts of new renewable energy projects in California communities by 2020,” the group said in a statement. “The Campaign’s initiatives will maximize clean energy job creation, attract billions of private investment dollars, boost state and local government budgets, and reduce electric bills.”

In the Golden State, that’s like saying you love the beach, dolphins, and sunshine. So what is the Clean Coalition — whose members range from the Los Angeles Business Council to the California chapters of the U.S. Green Building Council to Westinghouse Solar — actually going to do?

One, push for the expansion of programs requiring utilities to pay premiums — aka feed-in tariffs — for distributed generation of renewable energy, such as rooftop solar and small photovoltaic farms.

The Clean Coalition also plans to lobby to simplify and speed up the process of connecting renewable energy projects to the grid, currently a years-long, laborious process not designed for bringing on hundreds if not thousands of new power sources. Stephanie Wang, the Clean Coalition’s program director, told me the group would focus on legislation and regulatory reform to achieve its aims.

In a sign of the Clean Coalition’s pull, the organization trotted out California’s green elite to endorse its campaign, from a former state energy commissioner to Terry Tamminen, who served as secretary of the California Environmental Protection Agency under Gov. Arnold Schwarzenegger.

While the Clean Coalition and Steyer’s group are pursuing separate if complementary agendas, the result is likely to be a full-court press to get California Democrats, who control all top statewide offices from Gov. Jerry Brown on down as well as the legislature, to ramp up renewable energy production.

Tech companies have something hanging over their heads.Photo: The Sharpteam

According to a Greenpeace report [PDF] released this week, all those presumably green and well-meaning digital workers-slash-slackers are contributing to global warming every time they update their Facebook status, scan their Twitter stream or check their Gmail.

That’s because all those apps live in massive data centers — a.k.a. “the cloud.” In the “How Dirty is Your Data?” report, Greenpeace analysts estimate data centers currently consume between 1.5 and 2 percent of global electricity production.

“Cloud computing is converting our work, finances, health and relationships into invisible data, centralized in out-of-the-way storage facilities or data centers,” state the study’s authors. “This report seeks to answer an important question about this trend, currently underway across the globe: As cloud technology disrupts our lives in many positive ways, are the companies that are changing everything failing to address their own growing environmental footprint?”

The report ranks operators of major data centers — Apple, Facebook, Google, etc. — according to a number of factors, including their source of electricity, i.e. whether the cloud is powered by coal, natural gas, wind, hydro, or other energy sources.

But before we get into the numbers, a big caveat: Tech companies guard their data-center data like state secrets, and Greenpeace is relying on what public information is available, as well as previous studies.

“Much of the information that would allow us to assess the net benefits of the cloud by also measuring the true environmental cost of these localized, power-hungry data centers is missing,” Greenpeace acknowledged. “This veil of secrecy makes it nearly impossible to measure the actual benefits of cloud technologies or understand the extent to which IT’s growing need for electricity is increasing the use of dirty energy.”

With that in mind, the rankings are not kind to Silicon Valley companies who like to cultivate a clean green image.

Greenpeace calls Apple the most dependent on coal to power its data centers, earning a 54.5 percent “coal-intensity” ranking and scoring only 6.7 percent on the group’s “clean energy” index.

Facebook, which has been the target of an ongoing Greenpeace campaign, was held to be the second most coal-intensive data-center operator with a 53.2 percent ranking. 

Google, which this week invested $100 million in contracts to buy electricity from a wind farm to power a new Oklahoma data center, scored comparatively well with a 34.7 percent coal-intensity ranking and 36.4 percent on the clean energy index.

But rival Yahoo took the top spot for clean energy with a 55.9 percent ranking and an 18.3 percent coal-intensity score.

Given the secrecy surrounding data centers, these numbers are probably general indicators. But the real impact of the report may be to get our heads out of the cloud to start thinking about the down-to-earth impact of our virtual ways. 

Google’s Oklahoma wind farm will be built this year.Photo: Marcin Wichary

But this week’s big money move — the third so far this month — is different. It also involves wind but is a power purchase agreement (known as a PPA in the utility trade) rather than a direct investment in a specific project.

The deal with wind developer NextEra Energy Resources was struck by Google Energy, a subsidiary of the search giant that has been licensed by the federal government to buy electricity on the wholesale market.

Essentially, Google Energy acts as a quasi-utility, signing long-term contracts for electricity. In this case, it has committed to a 20-year contract to buy the electricity generated by a 100.8-megawatt wind farm called Minco II that NextEra will build in Oklahoma, where a new Google data center is set to go online later this year.

“This 100.8 megawatt facility will be built as a direct result of our financial commitment and should be operational in late 2011,” Gary Demasi, of Google’s global infrastructure team, wrote on the company’s official blog.

“We’ve been exploring ways, such as this PPA, to reduce emissions further by increasing the amount of renewable energy we use to power our operations,” he added. “We purchase high-quality carbon offsets for any remaining emissions.”

The value of the power purchase agreement was not disclosed — typically such deals are kept in a black box for competitive reasons. The advantage of such a deal over a direct investment is that it assures bankers and other financiers that a project has a guaranteed market for the electricity. And Google gets to claim that clean energy even though it goes into the grid rather than directly to its facility.

The Oklahoma wind farm will be built this year, according to NextEra, the United States’ largest wind developer.

The deal is Google’s second power purchase agreement with NextEra. Last year, it signed a 20-year contract to buy electricity generated by a 114-megawatt Iowa wind farm. 

Google is helping to create economies of scale for clean energy.Photo: T.J.

Google has been on a green tech investment roll of late. Last week, the search giant put $168 million into BrightSource Energy’s 370-megawatt solar thermal power plant, currently the world’s largest solar project, which is under construction in the Southern California desert. And on Monday, Google announced it would invest $100 million in the 845-megawatt Shepherds Flat Wind Farm in Oregon. Shepherds Flat, being built near Arlington, Ore., will be the world’s largest turbine farm when completed, if it hasn’t been overtaken by another project by then.

“This project is exciting to us not only because of its size and scale, but also because it uses advanced technology,” Rick Needham, Google’s director of green business operations, wrote in a blog post. “This will be the first commercial wind farm in the U.S. to deploy, at scale, turbines that use permanent magnet generators — tech-speak for evolutionary turbine technology that will improve efficiency, reliability, and grid connection capabilities.”

“Though the technology has been installed outside the U.S., it’s an important, incremental step in lowering the cost of wind energy over the long term in the U.S.,” he added.

Other investors in the Oregon wind farm are General Electric, the nation’s biggest turbine maker, and Sumitomo Corporation.

Shepherds Flat has been something of a controversial project for the $1.3 billion federal loan guarantee its developer, Caithness Energy, has secured as well as state incentives for a wind farm that will create relatively few jobs.

But for Google, the investment is probably less about creating green jobs than generating green energy at scale as part of its corporate commitment to make carbon-free energy cheaper than that of coal-fired power.

The Silicon Valley giant says it has so far invested $350 million in clean energy projects. Two weeks ago, for instance, Google invested $5 million in a German photovoltaic power plant

“This facility will provide clean energy to more than 5,000 households in the area surrounding Brandenburg,” wrote Benjamin Kott, Google’s clean energy advocacy manager, in a blog post. “Until the early 90′s, the site was used as a training ground by the Russian military. We’re glad it has found a new use!”

The $350 million is just what Google has directly invested in projects. Its investment arm, Google Ventures, has put in tens of millions more in various governments, ranging from peer-to-peer car sharing ventures to biofuel firms to an Ag 2.0 startup.

The Notrees wind farm.Photo: Duke Energy

Duke Energy is not a Texas company, but it owns the aptly named Notrees wind farm in the Texas panhandle. The North Carolina power giant is teaming up with an Austin area startup called Xtreme Power to install a 36-megawatt battery at the 153-megawatt Notrees Windpower Project near Kermit, Texas.

That’s one big battery. Such technology is likely to become crucial as wind farms become ever larger but erratic suppliers of electricity to the grid. In wind-blown West Texas, the region’s massive turbine farms can generate more electricity than the grid can handle at some times while all but ceasing production at other times. That creates headaches for grid operators, and the ability to store wind energy and release it when needed would help smooth out the ebbs and flows of the electricity stream.

“This system will store excess wind energy and discharge it whenever demand for electricity is highest — not just when wind turbine blades are turning. In addition to increasing the supply of renewable energy during periods of peak demand,” Duke said in a statement.

Pacific Northwest grid operators will probably be watching the experiment closely. That region boasts abundant hydropower and huge wind farms, which has created situations when there’s a surplus of both wind and water power and insufficient capacity on transmission lines to offload the electricity. Batteries would help, though it probably would take huge banks of them to have a significant impact.

The federal government is obviously interested in the technology. The Department of Energy has thrown in $22 million for the project, with Duke matching the grant with another $22 million.

Duke and Xtreme plan to plug in the battery by late 2012. 

The Kogan Creek Power Station.Photo: Kogan Solar Boost

Why, you may be wondering, would the PM travel to a remote 750-megawatt coal power station to make a big renewable energy news pronouncement?

Well, coal is king in Australia, and the 44-megawatt solar thermal project to be built by Areva Solar at the Kogan Creek Power Station will generate additional steam to drive the coal plant’s turbines.

“By using energy from the sun with Areva’s solar booster application, we will make the coal-fired plant more fuel-efficient and reduce its greenhouse intensity — avoiding the production of 35,600 tons of greenhouse gas emissions annually,” David Brown, chief executive of CS Energy, the coal plant’s owner, said in a statement.

Australia depends on coal to supply about 87 percent of its electricity demand, which gives it one of the highest per capita rates of greenhouse gas emissions in the world. Coal is also a major export, and at any given moment a flotilla of ships sits off the Queensland coast waiting to ferry the fuel to China and other overseas markets.

Despite Australia’s abundant sunshine, the country has been something of a laggard when it comes to renewable energy — which is why a 44-megawatt solar power project is considered a big deal.

In fact, Australia has suffered a green brain drain in recent years as solar entrepreneurs, frustrated with the lack of government support for renewable energy, fled to California.

One of those startups was called Ausra, which developed compact linear fresnel reflector technology that uses rows of long mirrors to focus sunlight on liquid-filled tubes suspended over the arrays. The heat creates steam, which in turn drives standard electricity-generating turbines.

In California, Ausra attracted investment from such prominent Silicon Valley venture capital firms such as Kleiner Perkins Caufield & Byers and Khosla Ventures. But last year the startup was sold to — you guessed it — Areva, the French energy giant and nuclear power plant builder.

Rebranded Areva Solar, Ausra has now come home, so to speak, to Australia.

When I spoke to Areva Solar executives late last year, they were bullish on the market for such so-called solar boost projects like the one at Kogan Creek. But the company also plans to build stand-alone solar power stations to generate 100 percent carbon-free electricity.

Maybe even in Australia. 

A rendering of the future Ivanpah solar plant. Photo: BrightSource Energy

On Monday, BrightSource Energy became the first solar power plant developer to complete the financing of a large-scale project in two decades. The United States Department of Energy finalized a $1.6 billion loan guarantee BrightSource’s 370-megawatt Ivanpah Solar Electric Generating System solar thermal power plant now under construction in the Mojave Desert in Southern California. (The feds initially had pledged $1.37 billion but threw in another $230 million Monday.)

As the deal closed, Google announced it was investing $168 million in the Ivanpah project. The search giant had been an early investor in BrightSource but dramatically upped its stake with this latest investment.

“We need smart capital to transform our energy sector and build a clean energy future,” Rick Needham, Google’s director of green business operations, wrote Monday on the official Google blog.

“This is our largest investment to date, and we’ve now invested over $250 million in the clean energy sector,” he added. “We’re excited about Ivanpah because our investment will help deploy a compelling solar energy technology that provides reliable clean energy, with the potential to significantly reduce costs on future projects.”

BrightSource previously had secured a pledge from NRG Energy to invest up to $300 million in Ivanpah. NRG, which operates fossil fuel and nuclear plants, has in the past two years invested in several big solar projects.  

Now to Tuesday’s news. California Gov. Jerry Brown is scheduled to sign into law a requirement that the state’s utilities obtain 33 percent of their electricity from renewable sources by 2020.

U.S. Energy Secretary Steven Chu is jetting in for the signing ceremony at a new photovoltaic panel manufacturing plant in Silicon Valley operated by SunPower and Flextronics.

According to SunPower, the new factory has created more than 100 jobs and will supply 75 megawatts’ a year worth of panels for the San Jose company’s photovoltaic farm projects and rooftop projects in the U.S.

Solar company PR people have been flooding my inbox in recent days with statements regarding the 33 percent renewable portfolio standard, but the reality is that not much is going to change.

Former Gov. Arnold Schwarzenegger previously had issued an executive ordering mandating that 33 percent standard, and regulators and utilities have been operating under the presumption that the target needed to be met.

Still, executive orders are subject to revocation by a governor’s successors. Brown’s action enshrining the 33 percent standard into law sends a strong signal to investors, renewable energy entrepreneurs, and utilities.

But the renewable energy news isn’t all sunny these days. Congressional Republicans continue to try to scrap the Energy Department’s loan guarantee program. If that happens, Ivanpah may be the first and last big solar power plant built in California for some time.

I was going to write today about Facebook’s efforts to boost the energy efficiency of its Oregon data center by 38 percent. The social networking Goliath did that by redesigning servers and the operations of the facility, then broke with industry convention by sharing its secret sauce with competitors in a new initiative it calls the Open Compute Project.

(That didn’t exactly neutralize criticism from Greenpeace, which has mounted a campaign against Facebook for its dependence on coal-fired power plants at the company’s Prineville, Ore., data center.)

Data centers are the steel mills of our post-industrial information economy and consume enormous amounts of electricity, so reducing their power consumption is a huge environmental issue.

Unfortunately, it’s also quite a boring topic to non-engineers. (Believe me, I watched the live Facebook webcast on the Open Compute Project on Thursday.)

Why use virgin plastic for cylinder covers when recycled carpet does the trick?Photo: FordSo, since it’s Friday, I was easily distracted by this news morsel: Ford is using recycled carpet in its engines. More specifically, the recycled material is being repurposed as cylinder head covers.

Now normally, I would have no idea what that means exactly, but I recently wrote a story on Silicon Valley-backed startups developing new super fuel-efficient versions of the internal combustion engine, so I’ve spent some time in garages lately.

The cylinder head is the part of the engine where fuel combustion takes place. Cylinder head covers usually are made of virgin plastic — read petroleum. (Ford has also used soy for seat cushions, recycled yarn for seat covers, and old blue jeans to dampen sound.)

Ford is now using a material called EcoLon, made by Wellman Engineering Resins from entirely recycled carpet, for cylinder heads manufactured by Dana Holding Corporation in its Escape, Fusion, Mustang, and F-150 vehicles.

The bottom line: Ford says it has so far kept 4.1 million pounds of carpets out of landfills — that’s the equivalent of 154 football fields, according to the automaker — and has reduced oil consumption by 430,000 gallons.

Sounds like a magic carpet ride.