Author

Tina Casey

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

Activism Jobs

1,000 New Solar Jobs For US Military Veterans

by Tina Casey November 10, 2015

written by Tina Casey

In advance of Veterans Day, the non-profit solar installer GRID Alternatives has announced a hookup with Wells Fargo to kick off “Troops to Solar,” a three-year program aimed at training more than 1,000 military veterans for jobs in the burgeoning solar industry. The program will also train service men and women who are still on active duty, which will help foster a seamless transition to employment once they return to civilian life.

So…it doesn’t seem like those 35 permanent jobs promised by the Keystone XL oil pipeline project will be missed.

Solar Jobs For Solar Veterans

As the US Department of Defense ramps up its transition to renewable energy, more servicemen and -women are becoming exposed to solar power. That includes both utility scale solar and rooftop solar for housing and other facilities at permanent military bases, solar canopies and solar-enabled microgrids for forward bases, and even portable solar gear to carry into the field.

That familiarity is one factor that could make military service an attractive background for solar employers. However, there are deeper elements at work. Nat Kreamer, a veteran and Board Chairman of the trade organization SEIA (Solar Energy Industry Association), explains:

As an industry, we are completely committed to hiring more veterans. Today, America’s solar energy companies already employ twice as many veterans as the average U.S. business. We hire veterans because they come trained, ready and passionate. The solar industry is filled with people who are motivated to build our economy, improve our environment and strengthen our national security.

[snip]

…Solar, like the military, is not just about the paycheck; it is also about working for something larger than oneself.

Last spring SEIA locked arms with First Lady Michelle Obama and Dr. Jill Biden in support of Joining Forces, an initiative aimed at rallying support for US service members and veterans, with a commitment to fill 50,000 solar jobs with veterans by 2020.

That initiative includes on-base solar job training for active duty service members under an Energy Department pilot project that just graduated its first class earlier this year at Camp Pendleton.

GRID Alternatives And Solar Jobs (And Wells Fargo)

With its goal of 1,000 trained solar workers, the new GRID Alternatives Troops to Solar program will take a nice little bite out of the 50,000 mark.

The three-year program, funded by a $750,000 grant from Wells Fargo, will provide placement services leveraging Grid Alternatives’s existing network services as well as solar job training and solar job training.

As part of Troops to Solar, GRID Alternatives is launching a new focus on Native American veterans and “high-need” communities on tribal reservations.

Wells Fargo notes that it is a longtime partner of GRID Alternatives, having invested more than $3.8 million (including the latest grant) since 2007. The funding has gone to GRID Alternatives’ twin goals of installing solar systems for low-income households, including veterans, while also training veterans for solar jobs.

For those of you unfamiliar with GRID Alternatives, here’s a rundown:

GRID Alternatives is America’s largest non-profit solar installer bringing clean energy technology and job training to low-income families and underserved communities through a network of community partners, volunteers, and philanthropic supporters. GRID has installed nearly 6000 rooftop solar systems with a combined installed capacity of over 20MW, saving $155 million in lifetime electricity costs, preventing 450,000 tons of greenhouse gas emissions, and providing over 22,000 people with solar training.

GRID Alternatives works all over the country, with a solar project in Baltimore being one recent example, and this year it also formed a powerful solar jobs training partnership with industry leader SunEdison.

As For Keystone…

Now that the dust has settled over President Obama’s decision to deny a federal permit for construction of the pipeline, at least one conservative observer has hinted that the President did TransCanada — and its investors — an enormous favor by effectively killing the project. It doesn’t make sense in today’s glutty oil world, as described by The New Republic (cited in a longer New York Magazine piece):

Tar sands oil is remarkably expensive to cultivate…Oil is currently trading at less than $50 a barrel and there’s increasing speculation that the stuff will remain cheap for a long time to come. The plunge in oil prices is already affecting tar sands production: Earlier this year, Shell cancelled plans for a major investment in the tar sands. Nor are they the only ones calling off future development. The plunge in oil prices and fall-off in investment means that Keystone simply no longer makes economic sense.

We’re thinking that all of those pipeline jobs “lost” over Keystone will be made up by the renewable energy industry, and then some. SEIA’s commitment alone tops the 42,000 temporary construction jobs promised by TransCanada for building Keystone XL, and the Joining Forces initiative is backed up by other Obama Administration solar jobs initiatives.

However, take a look at one of our favorite news blogs — FuelFix.com — and you’ll notice that those zombie oil and gas pipeline jobs could very well spring to life in eastern states, so stay tuned.

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Photo credit: Portable solar canopy deployed in Djibouti via US Army.

November 10, 2015 0 comment

Solar Records

New Solar Cell Efficiency Record Breaks 21% Barrier

by Tina Casey November 9, 2015

written by Tina Casey

A new solar cell efficiency record has been set by China’s Trina Solar Limited, which announced that its new p-type multi-crystalline silicon solar cell has achieved a solar conversion efficiency of 21.25 percent according to the results of third-party testing. Greater efficiency does not necessarily translate into lower costs, but the manufacturing method is based on Trina’s existing technology and the company anticipates that its new solar cell will provide an extra push to the steep downward trend for the cost of solar-sourced electricity.

Somewhat ironically, the news of additional progress in the solar energy field caps off a series of extremely bad news for fossil fuels — particularly petroleum — beginning with the incredible Volkswagen diesel emissions scandal on up to denial of a permit for the Keystone XL tar sands oil pipeline in the US, and the exposure of ExxonMobil’s duplicity on climate change.

Solar Cell Efficiency Records

Where were we? Oh right, the new solar cell efficiency record. For those of you new to the topic, while complex multi-layer solar cells can already achieve solar conversion efficiencies far greater than 21 percent, relatively low cost and simplicity still provides silicon solar cells with an edge in the marketplace.

Trina Solar had its solar cell efficiency rated by the Fraunhofer ISE in Germany, which just a few days ago issued a report on the current state of solar technology and markets. Here’s what Fraunhofer had to say about solar cell efficiency records for technologies on the market today:

The record lab cell efficiency is 25.6 % for mono-crystalline and 20.8 % for multi-crystalline silicon wafer-based technology.

The highest lab efficiency in thin film technology is 21.0 % for CdTe and 20.5 % for CIGS solar cells.

In the last 10 years, the efficiency of average commercial wafer-based silicon modules increased from about 12 % to 16 %. At the same time, CdTe module efficiency increased from 9 % to 13 %.

In the laboratory, best performing modules are based on mono- crystalline silicon with about 23 % efficiency. Record efficiencies demonstrate the potential for further efficiency increases at the production level.

In the laboratory, high concentration multi-junction solar cells achieve an efficiency of up to 46.0 % today. With concentrator technology, module efficiencies of up to 38.9 % have been reached.

Did you catch that first item where it said the record for multi-crystalline solar cells was *only* 21 percent? Fortunately, the researchers who put together the report prefaced the whole thing by noting that in the fast-paced world of solar cell efficiency development, their information would probably be out of date sooner rather than later.

And, they were right.

The Trina Solar Cell Efficiency Record

That mark of 20.8 percent was probably rounded up from Trina’s earlier record-setting entry for solar cell efficiency, which clocked in at 20.76 percent about one year ago.

If you’re thinking that the difference between 20.76 and 21.25 doesn’t sound all that impressive, consider that even just breaking the 20 percent barrier has been a long, hard slog. Solar cell efficiency for multi-crystalline silicon technology was still hovering around the 19.8 percent mark back in 1999. As described in the solar cell efficiency study we came across, the researchers zeroed in on a “honeycomb” surface, echoing Trina’s Honey Plus brand:

The improved multicrystalline cell performance results [partly] from isotropic etching to form a hexagonally-symmetric “honeycomb” surface texture. This texture, largely of inverted hemispheres, reduces reflection loss and improves absorption of infrared light by effectively acting as a randomizer.

In its solar cell efficiency announcement, Trina notes that it purposefully focused on low-cost, scalable processes to manufacture the record breaking solar cell, leading to high-volume commercial production. Here’s the rundown:

The record-breaking p-type multi-crystalline silicon solar cell was fabricated on a high-quality mc-Si substrate with a process that integrates advanced Honey Plus technologies including back surface passivation and local back surface field. The 156×156 mm2 solar cell reached a total-area efficiency of 21.25%.

Solar Cell Efficiency Up, ExxonMobil Down

Getting back to that bad week for petroleum, ExxonMobil is dealing with a barrage of criticism for knowing all about the global risks and impacts of its products, yet choosing to sit on the facts while supporting a mini-industry of lies about climate science. As of this writing the company is also under investigation by New York State Attorney General Eric Schneiderman, so there’s that.

In a 2008 article, New York Times reporter Jad Mouawad provides a fascinating glimpse into the corporate culture behind the global warming denial strategy. Do read the whole thing but here’s a snippet including a remark by ExxonMobil CEO Rex Tillerson:

What might be called the Exxon Way can be summed up in three ideals: discipline, patience and long-term vision. It is a formula the company drills into its managers from the moment they join Exxon, and which it keeps repeating through their careers. It explains the company’s resilience and its view that it has survived, and thrived, through countless commodity cycles.

“We are all homegrown,” Mr. Tillerson says. “That happens through a very deliberate and very closely managed process, and it starts the day the person walks through the door with us. And we are the product of that system…

TAKE a room full of oil managers, and the Exxon people usually stand out, even as they try not to draw much attention to themselves. They typically band together, and often cultivate an aura of secrecy — and sometimes superiority — toward the outside world.

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Image (screenshot) via Trina Solar.

November 9, 2015 0 comment

CSP Energy Storage

Next-Gen Energy Storage Aims At Concentrating Solar Power Plants

by Tina Casey November 6, 2015

written by Tina Casey

Energy storage is the key to making concentrating solar power plants an economical, reliable alternative to coal for electricity generation, and the US is determined to lead the field into new levels of efficiency. In the latest development, the Energy Department’s SunShot initiative is behind a new energy storage system based on chemical bonds that transfer heat as they store and release energy.

If R&D on the new system progresses, the result will be an energy storage system with greater density, translating into lower costs for electricity generated by concentrating solar power plants. In the context of US President Barack Obama’s new Clean Power Plan, that help sun-rich US states meet their carbon goals through solar-sourced electricity that is competitive with cheap natural gas as well as coal, this is very good news indeed.

New Materials For Thermochemical Energy Storage

The new energy storage research comes from Oregon State University in collaboration with the University of Florida. The system is based on thermochemical storage, which is different from conventional batteries because it deploys chemical bonds to deploy heat, not electricity. It is also different from thermal energy storage, such as the molten salt energy storage system that represents the leading edge of energy storage for the next-generation concentrating solar power (CSP) plants of today.

The key advantage of the new system is that it can potentially accommodate greater heat, up to 1,200 degrees centigrade, compared to the 600 or so degrees centigrade typical of molten salt energy storage.

Here’s the rundown on the University of Florida’s contribution, from the Energy Department:

The University of Florida (UF), through the Concentrating Solar Power: Efficiently Leveraging Equilibrium Mechanisms for Engineering New Thermochemical Storage (CSP: ELEMENTS) funding program, is working on making concentrated solar power economically competitive with traditional forms of energy generation by driving the cost towards $0.06/kWh through the use of thermochemical energy storage (TCES).

The project uses inexpensive, safe, and non-corrosive strontium-based carbonates* and high temperatures from concentrated sunlight to break chemical bonds and store energy during the day time. During off-sun periods, the reaction is reversed to remake the chemical bonds previously broken, releasing the stored heat, and doing so at temperatures previously unachievable in other carbonate-based TCES processes.

(*Note to Star Wars fans — that’s carbonate, not carbonite).

The research team at UF has been using an alarmingly named screening method called Sacrificial Pore Formation to screen strontium-based carbonates for capacity and durability. That researched is aimed at modelling the economics of the new system, with the goal of demonstrating a capital investment of less than $10/kWh_th (kilowatt hours – thermal).

The end goal is to drum up interest in the investor community to team up with the Energy Department and its academic partners, with the overall goal of generating solar-sourced electricity at less than $0.06 cents per kilowatt hour.

Harnessing Thermochemistry For Energy Storage

The new energy storage study is available at ChemSusChem, the Chemistry and Sustainability/Energy and Materials journal under the title “Solar Thermochemical Energy Storage Through Carbonation Cycles of SrCO3/SrO Supported on SrZrO3.”

The system works by using the reversible nature of strontium carbonate, which decomposes into strontium oxide and carbon dioxide. The decomposition process consumes thermal energy, which is released when the two substances recombine.

The research team points out several factors working in favor of the new system. It is based on cheap, non-toxic materials, and the high temperature of the operation could be deployed directly in a hot air turbine system, as well as generating steam for a steam-driven turbine. Overall, the low cost and high output could result in a tenfold increase in energy density, according to the research team.

So far the system has been tested on a small, pre-prototype scale. The researchers have already noted a decline in energy storage capacity after 45 heating and cooling cycles, expressed as “slowing carbonation kinetics.” Before the system gets to the prototype level, the next steps include drawing out the carbonation steps and addressing the issue of thermal shocks.

So, What About The Clean Power Plan

Speaking of innovative new energy storage systems, we got a preview copy of the Energy on the Edge episode of the new National Geographic Channel Series, Breakthrough. Check it out and you’ll get an idea of the gut-churning drama involved when your reputation and your research dollars are riding on the progress of your lab-work.

The episode also includes some great footage of the massive Crescent Dunes CSP plant as it commences a step in its startup run, including an insidery view of the actual molten salt.

The basic point that Energy on the Edge hammers home (thanks to some great storytelling by sci-fi veteran Akiva Goldsman), is that energy risk-takers are putting it all on the line to propel the human community into a sustainable model for energy generation.

Keep that all in mind when you hear about opposition to the Clean Power Plan.

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Image: by Kelvin Randhir, courtesy of the University of Florida.

November 6, 2015 0 comment

Science Solar Research

Perovskite Solar Cells Rule, Clean Power Plan Lawsuits Drool

by Tina Casey November 2, 2015

written by Tina Casey

We were just talking about the accelerated pace of R&D for perovskite solar cells, and along comes the University of California, Los Angeles, with another contribution to the perovskite pot. Put that in the context of the lawsuits sprouting up against President Obama’s new Clean Power Plan, and you have yet another instance of the fossil fuel lobby waging battle in a war that’s already been lost.

That’s because perovskite is a cheap, easily manufactured material that has the potential to force the cost of solar energy even lower than it is today, forcing its chief competitors — coal and natural gas — off the electric power plant field, Clean Power Plan or not.

By the way, did you know that the iconic fossil fuel producing state of Texas is already well on the way to meeting its Clean Power Plan goals? More on that in a second.

Perovskite Power, Solar Cell Style

Where were we? Oh right, perovskite solar cells. For those of you new to the topic, perovskite actually refers to a class of synthetic crystalline materials based on the unique properties of the naturally occurring mineral perovskite.

Perovskite offer enormous promise in terms of solar cell conversion efficiency, but they also have an enormous Achilles heel, which is their tendency to fall apart when exposed to air, especially humid air.

Just this week we took note of a futuristic new development in the field involving so called hot-carrier perovskite solar cells, but the new perovskite solar cell research from the University of California – Los Angeles (UCLA) is a bit more down to earth in terms of solving the air-phobia problem.

A team from UCLA’s California Nanosystems Institute has figured out a new way to stabilize perovskite, basically by creating a perovskite solar cell sandwich.

The conventional approach is to use an organic material as the top buffer layer, in order to get the solar-generated electricity out of the cell. However, the materials typically in use aren’t all that stable themselves, and provide relatively poor cover for the perovskite layer.

By replacing those layers with metal oxides, the UCLA team achieved a “dramatic” difference in longevity. Specifically, the new perovskite solar cells are composed of layers in this order: glass, indium tin oxide, NiOx (oxidized nickel oxide), perovskite, zinc oxide, aluminum, with the ZnO layer providing protection by keeping the aluminum from the perovskite.

In a 60-day open air test at room temperature, the metal oxide perovskite solar cells retained 90 percent of their original conversion efficiency.

Okay, so that doesn’t solve the entire problem, but it indicates that the way forward is to engineer metal oxide layers that are more dense, providing better protection for the perovskite.

You can read all about it in the journal Nature.com under the title “Improved air stability of perovskite solar cells via solution-processed metal oxide transport layer.” The study includes a relatively plain-language description of the challenges involved in engineering a long-lived perovskite solar cell.

UCLA’s press materials also provide a good snapshot of just how fast the rate of perovskite R&D is accelerating. The team started less than two years ago with a conversion efficiency of less than one percent, and it’s already closing in on the 20 percent mark. In the new study, the relatively stable version clocked in at approximately 14.6 percent plus or minus 1.5 percent, for a maximum of 16.1 percent.

The Clean Power Plan Battle (Or Horse Race)

As for the Clean Power Plan, our friends over at TheHill.com have been tracking the “quagmire” of lawsuits pouring in from legislators and businesses over the whole bundle of Obama Administration executive actions on climate and environment.

However, the Clean Power Plan may suffer death by a thousand cuts — and Senator Inhofe may schlep a boatload of snowballs to the Paris climate talks — but the simple fact is that the cost of renewable energy generally, and solar energy in particular, has been dropping like a stone despite efforts by the fossil fuel lobby to monkeywrench progress at the federal and local level. When you put an army of scientists up against an army of lawyers, science is already winning. If you prefer sports metaphors, let’s call it a horse race.

In the case of solar energy, the march of technology is only part of the equation. Costs have also been dropping because the Obama Administration has been focusing on smoothing over “soft” bumps for solar energy such as the permitting process, zoning rules, and administrative costs. Those soft costs still account for about 70 percent of the installed cost of a solar array, and the Energy Department has big plans to push that figure way down with a new “same-day” rooftop solar initiative.

If you prefer nature metaphors, take a look at Texas and you’ll see why the Clean Power Plan obstructionists are barking at a losing tree. Thanks partly to its magnificent wind resources, as well as a huge incentive to improve its transmission infrastructure, Texas is already well on its way to meeting its Clean Power Plan goals, even without sporting the kind of clean energy political image that some other states have been working on.

Stay tuned.

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Photo: via UCLA.

November 2, 2015 0 comment

Science Solar Research

Hot-Carrier Perovskite Solar Cells Could Bounce to 66% Efficiency

by Tina Casey October 30, 2015

written by Tina Casey

Perovskite solar cells have been getting a lot of attention for their potential to reach new heights of efficiency and new lows of cost. In the latest development, our friends over at the National Renewable Energy Laboratory have revealed a critical “bottleneck” in perovskite solar conversion that has huge implications for third-generation, super-efficient, hot-carrier solar cells.

Hot-Carrier Solar Cells

For those of you new to the topic of hot-carrier solar cells, you can get the lowdown in plain language from SPIE, the International Society for Optics and Phonics. The gist of it is as follows: With conventional solar cells, you only get two choices: simple materials, low cost, and low efficiency (such as single-junction solar cells); or multiple materials, high cost, and high efficiency (that would be multi-junction solar cells). In contrast, with hot-carrier solar cells, you could get simplicity of design, low cost, and high efficiency all in one, kind of like having your cake and eating it too. Here’s the explanation from SPIE:

“Heat production is detrimental to the output of solar cells. It occurs when a material absorbs photons with energies larger than its bandgap. To circumvent this problem, photogenerated charge carriers must be collected through specially designed contacts that are energy-selective. Carriers with large kinetic energies—‘hot carriers’—reach these contacts before losing most of their energy as heat. In principle, efficiencies as high as 86% could be achieved.”

If that sounds too good to be true, it is. Hot-carrier solar cells are a long way from the marketplace, one big challenge is how to rev up the kinetic energy transfer to top speed (as in, subpicoseconds), in order to prevent energy loss.

Nevertheless, the high return on efficiency makes the hot-carrier field full of temptation. When SPIE covered hot-carrier solar cells back in 2011, the high mark for solar conversion was 40%, achieved by multi-junction solar cells. In December 2014, CleanTechnica took note of a new solar conversion record of 46%. Considering that the theoretical limit is about 87%, that still leaves plenty of room for alternative, “third-generation” technologies to elbow in.

The Perovskite Solution For Hot-Carrier Solar Cells

So, finally, that brings us back around to the National Renewable Energy Laboratory (NREL). Just today, the lab announced that researchers have figured out a pathway for tackling the heat loss problem by deploying hot-carrier technology in perovskite solar cells.

Perovskite refers to a class of easily synthesized crystals with a structure based on a naturally occurring mineral, perovskite, that was discovered in the Ural mountains in 1839. Within recent years, researchers have been pursuing perovskites for improving solar conversion efficiency.

The commercial deployment of perovskite in solar cells faces some obstacles, with the use of lead being a particular thorny issue, but according to NREL, successive versions of perovskite solar cells have been “shooting up the efficiency charts faster than almost anything researchers have seen before,” making them juicy targets for further research, lead or no lead (for the record, tin is being explored as one alternative to lead).

When NREL began studying perovskites in 2009, it achieved a 3.8% efficiency rate. Within just a few years, the latest attempts have jumped up to more than 20%.

The new study, published in Nature Photonics under the title “Observation of a hot-phonon bottleneck in lead-iodide perovskites,” provides a pathway for pushing perovskite levels into the stratosphere, possibly as high as 66%. Here’s the rundown from the NREL media team:

“The NREL research determined that charge carriers created by absorbing sunlight by the perovskite cells encounter a bottleneck where phonons (heat carrying particles) that are emitted while the charge carriers cool cannot decay quickly enough. Instead, the phonons re-heat the charge carriers, thereby drastically slowing the cooling process and allowing the carriers to retain much more of their initial energy for much longer periods of time. This potentially allows this extra energy to be tapped off in a hot-carrier solar cell.”

According to the research team, the new study fills a critical information gap:

“Despite the earlier flurry of activity in characterizing the lead iodide perovskite system by transient absorption (TA) spectroscopy, a comprehensive and profound interpretation of the photocarrier-induced spectra is lacking. Previous work explained the TA spectra using a straightforward state-filling or Burstein–Moss model. However, a full assignment of the spectral response and the correlation between the magnitude of the TA signal and charge carrier density remains unexplored, in particular the role that excitonic transitions play in both the linear and excited-state optical and electronic properties.”

Did you get all that? Coincidentally, this morning, we just got a sneak peek at the new National Geographic–General Electric six-part series on breakthrough technology, aptly titled “Breakthrough,” which begins unspooling this Sunday, November 1. Following the reel, we got to hear from a panel of rather interesting people involved in creating the series, and one of the themes that came up was the speed at which technology is advancing, to the point where the filmmakers found themselves recording new developments practically in real time rather than simply recounting the past. Today’s revved-up world of solar cell research certainly fits the bill.

The whole series looks amazing, and of course we’re especially excited about the “Energy on the Edge” episode directed by the incredible sci-fi storyteller Akiva Goldsman. We’ll bring you some more details about that soon, including an exclusive interview with the folks at Dogfish Head (yep, these guys), a company featured in the episode.

Photo via NREL.

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October 30, 2015 0 comment

New Technology PV Science Solar Research

A (Relatively) Gigantic Perovskite Solar Cell Breakthrough

by Tina Casey October 9, 2015

written by Tina Casey

We’ve been spilling a lot of ink over perovskite solar cells recently, and here comes Brown University with yet another breakthrough. Along with researchers from the National Renewable Energy Laboratory, the Brown team has figured out a way to grow larger perovskite solar cells while keeping the conversion efficiency at a fairly high level. (h/t James Wimberley)

The Promise Of Perovskites

Solar researchers are all over perovskites, a class of synthetic crystals that mimic the unique structure of naturally occurring perovskite. Perovskites could become a low-cost, easy-to-manufacture substitute for silicon in solar cells, and researchers have been slowly breaking down the barriers to achieving that.

One problem, according to the Brown team, is that while relatively high solar conversion efficiencies of more than 20% have been reported in the laboratory, those are based on very small samples, typically 1/10 of a square centimeter.

Conventional processes for producing larger perovskite solar cells have fallen short in the quality department, with defects that interfere with efficiency.

“Glue” For Bigger, Better Perovskite Solar Cells

The new study can be found in the journal Advanced Materials under the title “Square-Centimeter Solution-Processed Planar CH3NH3PbI3 Perovskite Solar Cells with Efficiency Exceeding 15%.”

It’s based on a perovskite fabrication process previously developed at Brown, in which a solvent containing perovskite precursors is spread out on a substrate. An “anti-solvent” is then applied to get rid of the first solvent, leaving a nice smooth film of perovskite crystals.

The beauty of this method, aside from yielding a high-quality product, is its potential for scaling up to a commercial rate while keeping costs down, one factor being its ability to produce perovskite solar cells under room temperature conditions.

Scaling that process up is the challenge tackled by the new perovskite study. Here’s the rundown from Brown:

“The trick is to add excess organic precursor that initially “glues” the small perovskite crystals and helps them merge into larger ones during a heat-treatment, which then bakes away the excess precursor.”

Initial results for the new perovskite solar cells show an efficiency of 15%, which is not bad considering the potential to churn them out quickly and cheaply.

The team is pretty confident that this method, or one closely resembling it, could eventually get up to the 20% range and higher.

From The Lab To… Your Electric Vehicle

We’re still a ways away from a perovskite solar cell in every pot (except for maybe these guys), but when perovskites break through, there could be some very interesting applications in the mix.

In particular, we’re keeping an eye on this one with our sister site Gas2.org — a perovskite coating for electric vehicles, which would recharge your battery on the go a lot more efficiently than strapping a panel of silicon solar cells on top.

Earlier this year, we also floated the idea that Volkswagen might be toying around with a perovskite based EV battery, with a decision on the new battery apparently due this past July.

That date has come and gone, and the last we heard, Volkswagen chief Martin Winterkorn was still teasing the idea, so if you’ve heard anything drop us a note in the comment thread.

Meanwhile, of course, Winterkorn has left the company, which appears to have its hands full with other matters.

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Image via Brown University/NREL.

October 9, 2015 0 comment

Science Solar Modules Solar Research Thin Film Solar

Detergent-Enabled “Green” Thin-Film Solar Cells Wipe The Floor With “Clean” Diesel

by Tina Casey October 6, 2015

written by Tina Casey

As the saying goes, there ain’t no such thing as a free lunch. You can’t generate usable energy without some form of impact, whether it’s fossil fuels or renewables, and the Volkswagen “clean diesel” scandal provides ample evidence that technology solutions for fossil fuels are reaching their limit. In contrast, a new “green” thin-film solar cell study by Oak Ridge National Laboratory in the US demonstrates that solar energy has ample wiggle room to earn its clean cred.

What’s Not Clean About Thin Film Solar Cells

While solar energy is renewable, creating the goods needed to harvest that energy involves impacts all along the supply chain, from mining to manufacturing.

We’ve been spilling a lot of ink on thin-film solar cells partly because, although their solar conversion efficiency can’t match conventional silicon solar cells, they involve a highly efficient manufacturing process that cuts costs and helps to reduce lifecycle impacts. What has escaped our attention — our bad — is that the typical thin-film solar cell manufacturing process involves solvents, which are generally toxic.

The Road To Greener Thin Film Solar Cells

Well, group hug for all you US taxpayers. The new thin-film solar cell study from Oak Ridge National Laboratory (ORNL) indicates that the industry could transition out of its dependency on toxic solvents in favor of a more environmentally relaxed solvent called a surfactant, which is fancyspeak for detergent.

If you’re up for it, you can find the study under the title “Controlling molecular ordering in solution-state conjugated polymers” in the aptly named journal Nanoscale.

As described by ORNL, in the manufacturing of conventional thin-film solar cells, toxic solvents are deployed to shepherd molecules of polymers (that’s fancyspeak for plastics) to form nanoscale films. That’s 1,000 times thinner than your hair, for those of you keeping score at home.

To come up with a non-toxic alternative, the ORNL team designed a unique new polymer with a water-repelling “backbone” and water-attracting side chains.

The next step was to put the tailor-made polymer into a solution with a non-toxic surfactant. Like the new polymer, the surfactant also had both water-repelling (hydrophobic) and water-attracting (hydrophilic) ends.

When the research team tweaked the temperature and concentration of the solution, this happened:

“…the surfactant self-assembles into different templates that guide the polymer to pack into different nanoscale shapes—hexagons, spherical micelles and sheets.”

In other words, the surfactant arranges itself in a series of tiny stamps — kind of like nanoscale cookie cutters — that determine the shape of the polymer.

Here’s research team co-leader Jiahua Zhu enthusing over the discovery:

“Rationally encoding molecular interactions to rule the molecular geometry and inter-molecular packing order in a solution of conjugated polymers is long desired in optoelectronics and nanotechnology…”

Zhu further notes that the team was able to confirm its findings accurately because the researchers measured the effect of the surfactant in situ (fancyspeak for “in place”), instead of isolating the material or altering their tests.

Another Group Hug For Greener Thin-Film Solar Cells

Accurate in situ measurements can be extremely difficult — think of the difference between measuring the length of an eel while it’s swimming, compared to pinning it out on a board.

For its delicate nanoscale task, the ORNL team designed a test chamber that enabled the use of optical probes while the surfactant was busy doing its work.

So, another group hug for us taxpayers. The research team was based at ORNL’s Spallation Neutron Source, which does this:

“SNS is a one-of-a-kind research facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development. SNS produces neutrons with an accelerator-based system that delivers short (microsecond) proton pulses to a target/moderator system, where neutrons are produced by a process called spallation.”

That’s just for starters. Along with the spallation, you have your deuteration, which is a method for depositing heavier atoms into the polymer. That makes it easier to pick out contrasts, which helps to define the structure accurately as it evolves over time, from a solution to a solid.

In addition to defining the structure, the test chamber enables researchers to monitor the changing state of the material in real time when exposed to different conditions, including the type of solvent and the temperature, pressure, and humidity.

Don’t run out to Home Depot just yet to get your greener thin-film solar cells. So far, the research team has tested the new non-toxic self-assembly method under increasing temperatures. The next step is to do pressure tests, among other things.

As for so-called “clean diesel,” it looks like you can lump that in the same category as “clean coal.”

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Image: “A surfactant template guides the self-assembly of functional polymer structures in an aqueous solution” by Youngkyu Han and Renee Manning, via Oak Ridge National Laboratory.

October 6, 2015 0 comment

Investment New Technology PV Solar $Solar Modules Startups Thin Film Solar

“World-Beating” Perovskite Technology Rakes In $19 Million

by Tina Casey October 6, 2015

written by Tina Casey

The UK startup Oxford Photovoltaics has just announced a second round of funding for 2015 that brings its haul for the year to $19 million. That enables a big step forward in the company’s R&D plans for solar cells based on perovskite materials — those promising but pesky crystals that could help lower the cost of solar energy down to the ground.

Oxford PV and Perovskites

For those of you new to the topic, perovskite refers to a class of crystalline materials that can be synthesized easily (and cheaply) in the laboratory. The structure is based on the naturally occurring perovskite mineral, discovered in the Ural mountains in the 19th century.

With a killer combination of low cost and high efficiency, perovskites could be very useful in the solar industry except for a couple of hitches. One main problem is the crystals tend to wilt under humidity.

Oxford PV has been on our radar since 2013, when the company (a spinoff from the Snaith lab at Oxford University) announced a solar conversion efficiency of 15.4% for its perovskite solar cell.

In September 2014, the company tackled the humidity problem with a perovskite-enhanced, “turbo-boosted” solar cell consisting of thin-film perovskite solar cells printed directly onto silicon solar cells. According to Oxford PV, the perovskite film can boost the efficiency of a silicon solar cell by more than 25%.

Since then, the company has added two more iterations, printing thin-film perovskite solar cells onto CIGS solar cells and glass. Here’s the rundown from the Oxford PV website:

“Pioneering work developing perovskite thin-film solar cells has delivered a route to boosting the efficiency of current commercial cells; using a high efficiency coating in a multi-junction or ‘tandem’ cell architecture. In addition, printing perovskites directly onto glass has led to a semi-transparent coating ideal for BIPV applications and, once integrated into the glazing units of a building, the technology is capable of providing a significant percentage of the building’s electrical energy requirements directly from sun light, as can be seen from our case studies.”

Onwards And Upwards For Perovskite Solar Cells

The new round of funding builds £4.4 million on to the £8 million raised earlier this year by Oxford PV, so it looks like we could hear some news about commercializing the company’s perovskite solar cells sooner rather than later, which Oxford PV confirms:

“The £4.4 million top-up round announced today will help fund the continued development of Oxford PV’s world-beating technology as we move towards scale-up and commercial engagement with potential licensees.”