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Perovskite Solar Cell Bests Bugbears, Reaches Record Efficiency

Perovskite solar cells are one of the hottest prospects in clean energy research, offering good power outputs from low-cost materials that are relatively simple to process into working devices. But their rapid progress has not been without some stumbling blocks. 

Firstly, the cells’ power conversion efficiency often varies depending on how it is measured, suggesting an underlying instability in the cells’ light-gathering perovskite materials. That’s bad news for photovoltaic panels that need to work for a decade or more. Secondly, researchers were struggling to extend the range of the light wavelengths that the cells could harvest, a key strategy for improving their efficiency beyond the 20 percent or so achieved by typical silicon or thin-film solar cells. Some of the field’s leading lights have spent much of last year grappling with these issues.

Now a team researchers in South Korea has developed a perovskite blend that addresses both these challenges, and delivers what they say is the highest-efficiency perovskite cell to date.

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2014 Renewable Energy Recap: Stepping Backward, Crawling Forward

If we want to stay positive, 2014 was the year when solar power started making the sort of noise in global energy markets that experts have long predicted. If we allow some cynicism to creep in, 2014 was a year when big ideas stalled out, when falling oil prices left renewable energy’s immediate future in limbo, and when international climate deals seem both hopeful and far too timid.

Half full, half empty—take your pick!

Let’s start with the empty side. As has become tradition in these year-end posts, a quick look at the U.S. offshore wind industry: nope, still nothing. The miniature test turbine up in Maine remains the lone offshore turbine; the big projects gunning for the real first-in-water prize, meanwhile, do seem to be getting close. Star-crossed Cape Wind is finally through its legal and permitting hurdles, has made financing progress including $150 million from the Department of Energy, and plans to start construction in 2015; Deepwater Wind’s Block Island Wind Farm is also on track, with permitting completed and steps like naming its turbine foundation fabricator. Progress, perhaps, until we look at Europe and it’s 7000-plus megawatts of installed offshore capacity.

Another branch of marine-based renewable energy had a particularly disappointing year: wave power, long hyped as a great untapped source, seems to be taking steps backward all the time. Ocean Power Technologies, among the theoretical leaders in developing viable wave power tech, has scaled back or cancelled several plans this year, and the world still has no grid-connected wave power at all. In fact, we don’t even really know what wave energy should look like; designs abound, and research continues, but even a few megawatts of wave energy by decade’s end would be impressive.

Moving to the full part of the glass, solar power is really starting to explode. In the U.S., a big third quarter brought the country up to 16.1 gigawatts of installed photovoltaic capacity, with another 1.4 GW of concentrating solar power. According to the Solar Energy Industries Association, the growth through three quarters represented 36 percent of all new electricity capacity; in 2012, solar represented only 9.6 percent of new growth.

Around the world as well, solar made headlines this year. Germany produced half of its electricity from solar power on one particularly sunny day in June, and even the gloomy weather of the United Kingdom set records.

But wait, don’t get too excited: oil prices are dropping with remarkable speed. Though opinions differ about the consequence. Some—like Richard Branson—say this drop in dirty energy prices will have a severely limiting effect on solar power. Others argue that the markets are different, with oil prices affecting transportation fuels far more than the electricity generation markets where solar has been growing. Exactly how $50-per-barrel or lower oil will affect clean energy uptake will be a big story in 2015.

The other major driver of renewables moving forward is national and international climate policy. This year saw an historic deal between China and the United States, far and away the world’s two biggest emitters. It would cut U.S. emissions 26-28 percent below 2005 levels by 2025, and China commited to a peak emissions date of 2030. There are varying opinions on just how great this deal really is, but it undoubtedly changed the international, um, climate, surrounding emissions cuts. The Lima COP20 talks did produce something, though it is little more than a guideline for what might happen next year in Paris. A truly strong, binding, international climate deal, of the type we had all hoped for back in 2009 in Copenhagen and that some do hold out hope for in Paris in 2015, would have an immediate effect on renewable energy development.

Crawl forward, step back, leap forward, fall down flat. Renewable energy progress has never been particularly linear, and this year was no exception. Let’s check back in 12 months to see if these bumpy lines can all start pointing in the right direction.

NTSB Raps Some Knuckles With Boeing Battery-Fire Report

In a report released this month, the U.S. National Transportation Safety Board (NTSB) found plenty of blame to go around when reviewing a lithium-ion battery fire inside a 787 Dreamliner passenger aircraft in January 2013.

The board's report in particular singles out the plane's manufacturer (Boeing), its contracted battery supplier (GS Yuasa), and the Federal Aviation Administration (FAA) as falling short in ensuring public safety. Last year during NTSB hearings, Boeing Vice President Mike Sinnett called their self-policing policy with FAA "in retrospect... [not] conservative enough."

The NTSB apparently agrees. Its report says FAA provided "insufficient guidance" for its own certification engineers to develop testing for rechargeable batteries used in a commercial jumbo jet. (Such conclusions are also consistent with other criticism of FAA, as noted in a 2013 investigation by the Wall Street Journal that the agency today "has neither the budget nor the expertise to do extensive testing on its own.")

David Zuckerbrod, CEO of Baltimore-based Electrochemical Solutions, praises NTSB's thorough report. Zuckerbrod says he was shocked that the metal battery containers’ design had not taken into account the rare but often devastating thermal runaway fires well known in the cellphone, laptop, and portable electronics industry.

"Even the battery box design was poor," he says. "No one had engineered for cascading failure— one cell going boom and taking out the next cell and the next cell and the next cell. Battery folks know that [can] happen. Have you ever googled 'laptop battery fire'? These folks never watched that movie."

Press coverage at the time suggested that the 7 January 2013 Japan Airlines battery fire, which fortunately only ignited after all passengers and crew had disembarked at the gate at Boston's Logan Airport, might have been caused by overcharging, external heating, or environmental conditions surrounding the battery pack.

However, NTSB has concluded the battery caught fire because of an internal short circuit, possibly arising from either a manufacturing defect in the cell or from temperature spikes allowed by a poorly designed battery management system.

Zuckerbrod says NTSB's report found lax battery manufacturing protocols that are not up to the best industry standards.

For instance, he says, battery manufacturer GS Yuasa wasn't sufficiently careful in keep welding debris and other metal filings out of the battery cells. Moreover, cell assembly involved winding battery materials around a cylindrical mandrel and then flattening the cells by hand into a squashed oval shape that was then compacted into the battery container.

"I was surprised that GS Yuasa wasn't doing a better quality job on those cells, because they were going to be used in aircraft. When you have [military] spec stuff, they drive the vendors crazy with their specifications. It becomes a gigantic portion of the work to deal with the quality control. But the way they were assembling the cells was a little bit high-risk."

One number in the NTSB report in particular really took Zuckerbrod by surprise, he says. According to the report, GS Yuasa "stated that less than 1 percent of manufactured [battery] cells were rejected."

If this number is close to 1 percent and accurately reflects the battery's potential failure rate, he says, then it should give considerable pause. By contrast, he says, the industry standard 18650 lithium-ion battery cell has a typical failure rate of about one-in-ten-million (0.000001 percent).

"It seems like they took [a battery design] off the shelf that in retrospect wasn't aircraft grade," he says.

And while it's not known yet how much of the NTSB's Dreamliner recommendations have been adopted, Zuckerbrod says he thinks the agency's and media's scrutiny has made it likely they'll be taken seriously.

"There's a lot of good stuff in the report, with a big list of things they could do better," he says. "Some of which are easily adopted. We got lucky this time."

Electricity and Enzymes Turn Carbon Dioxide Into Alcohol Biofuel

When you drink alcohol, enzymes in your liver break it down into a series of byproducts, including carbon dioxide. A group of scientists in Austria are trying to run the process in reverse, using the same sort of enzymes to convert CO2 to alcohol and other products that can be used as fuel or as raw materials for the biochemical industry.

 “We are trying to reduce the CO2 electrochemically,” Stefanie Schlager, a doctoral student at Johannes Kepler University, Linz, Austria, told a session at the Materials Research Society’s fall meeting in Boston last week.

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Buckyballs Could Make Carbon Capture Better


The ever-useful buckminsterfullerene, or buckyball, has a new potential application: carbon capture. Researchers at Rice University in Texas used buckyballs (carbon-60 molecules, technically) as a “cross-linker” with polyethyleneimine (PEI), and produced a compound that binds carbon dioxide very well, avoids binding methane, and can be used at lower temperatures than other materials.

“We had two goals,” said Andrew R. Barron, of Rice, senior author of the paper describing the advance, in a press release. “One was to make the compound 100 percent selective between carbon dioxide and methane at any pressure and temperature. The other was to reduce the high temperature needed by other amine solutions to get the carbon dioxide back out again. We've been successful on both counts.”

The researchers published their findings in Nature’s Scientific Reports. They discovered that the PEI-C60 compound bound about one-fifth of its weight in carbon dioxide, and essentially zero methane—a big deal for carbon capture materials. The buckyballs are hydrophobic, and push the hydrophilic amines of the PEI to the outer surface of the compound; carbon dioxide floats past, and binds to exposed nitrogen atoms.

The PEI-C60 captured carbon better than materials known as metal organic frameworks (MOFs), which are nanoporous materials considered among the most promising for trapping CO2. The idea of using buckyballs was a natural progression for Barron’s lab; in previous work, the team found that single sheets of graphene did well at absorbing carbon dioxide. Multiwalled carbon nanotubes did better, and nanotubes with thinner single walls did even better still. The spherical buckyball takes the level of curvature to its extreme, which Barron said clearly plays a role in how well the molecules bind.

Another advantage comes up when the CO2 needs to let go of its new home—the final step on its road to toward the “sequestration” part of CCS. Other materials require temperatures to reach 120 and 130 degrees Celsius for the “amine scrubbing process” where the carbon dioxide is released. PEI-C60, meanwhile, has a lower “temperature of regeneration,” below 90 degrees Celsius.

The downside? Cost. “Compared to the cost of current amine used, C60 is pricy,” says Barron. “But the energy costs would be lower because you’d need less to remove the carbon dioxide.”

Progress toward deployment of a practical CCS regime remains slow, so any advances are obviously welcome. One of the first utility-scale CCS plants did recently open in Canada—a billion-dollar add-on to a half-century old coal plant. But without some major advances, or political shifts involving huge infusions of cash to the idea, projects like that are going to remain exceptions rather than the rule.

Turning E-Waste into Light

Bangalore-based IBM Research India has a bright idea for keeping discarded lithium laptop batteries out of landfills: repurposing their cells as energy supplies for the powerless. The idea, presented at this weekend's fifth annual Symposium on Computing for Development (DEV 2014) in San Jose, has passed a small proof-of-principle test run with Bangalore's working poor.

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Blu-ray Discs Spin Their Way Into Making Solar Cells More Efficient

Blu-ray had the misfortune to arrive at the very end of the era of optical storage media. Blu-ray discs are (were) certainly better than DVDs, but it was an incremental improvement at best, as they didn’t offer the same kind of revolution that the DVD offered over VHS. And with the cloud and high speed Internet becoming the standards for media storage and distribution, the future for the Blu-ray disc is a bleak one, full of shiny plastic shards in recycling bins.

Researchers at Northwestern University have hit upon a way to give Blu-ray discs a second chance at usefulness: They make excellent molds for imprinting solar cells with quasi-random nanostructures. Even the ones with terrible movies on them.

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Can China Turn Carbon Capture into a Water Feature?

In an intriguing footnote to their historic climate deal this month, Chinese President Xi Jinping and U.S. President Barack Obama called for demonstration of a hitherto obscure tweak to carbon capture and storage (CCS) technology that could simultaneously increase its carbon storage capacity and reduce its thirst for water. Such an upgrade to CCS holds obvious attraction for China, which is the world's top carbon polluter and also faces severe water deficits, especially in the coal-rich north and west.

As the Union of Concerned Scientists puts it in its The Equation blog, “Cracking this nut … could be a huge issue for China.”

Obama and Xi's deal pledges joint funding for a project that would inject about 1 million tons per year of captured carbon dioxide deep underground and, in the process, produce approximately 1.4 million cubic meters of water annually. One potential target is is GreenGen, an advanced coal-fired generating plant in Tianjin that was explicitly designed as a CCS test bed. 

Such ‘enhanced water recovery’ can be understood as an extension of the CCS-based enhanced oil recovery that is financing installation of carbon capture equipment at several North American coal-fired power plants. These include the upgraded coal generator in Estevan, Saskatchewan, that recently became the first coal plant to capture its CO2. Canadian utility SaskPower sells 1 million tons (1 megaton) of compressed CO2 to an aging oilfield nearby where it is pumped down into the oil-bearing formation to accelerate the upward flow of petroleum. 

If enhancing oil production is a revenue option for CCS, producing water with CCS is primarily about easing the storage of captured CO2 in deep saline aquifers. Geologists see carbonating saline aquifers as the most likely storage target for CCS if it becomes a universal aspect of fossil fuel power generation. Bringing up briny water in the process is not as lucrative as oil production, but offers some potentially significant benefits, starting with decreasing the pressure of the aquifer.

High pressures could fracture overlying rock layers and release injected CO2—a threat highlighted by unforeseen surface deformation detected five years ago atop a CO2 injection site in Algeria. None of the 3.85 megatons of CO2 stored in the 2-kilometer-deep reservoir escaped, but operators prematurely terminated CO2 injection, and anxiety over leakage risks paralyzed Germany’s leading CCS project. In May, the lead company on the German project, European power giant Vattenfall, terminated its CCS research and development activities.

Lowering pressure can reduce risk and/or enable faster and more extensive injection of CO2. A 2012 report on water removal from the International Energy Agency in Paris found that one CCS megaproject in Australia (Chevron's nearly-completed Gorgon liquified natural gas project) could boost CO2 storage capacity from 97.3 megatons to over 600 megatons by producing water.

The displaced water, meanwhile, can be put to good use—assuming it can be desalinated. One needs look no further than the coal-fired power plants that release most of China's CO2. Those plants use lots of water for cooling, and adding carbon capture is likely to make them consume even more.

In July, at one of the bilateral meetings that laid the groundwork for this month's presidential deal, the U.S. and China's joint Clean Energy Research Consortium commissioned a feasibility study for enhanced water recovery near the GreenGen plant in Tianjin. Their findings, presented in September at a U.S.-China CO2 emissions symposium in Hangzhou, were an unreserved  endorsement of this technique, according to Bill Bourcier, a geochemist at Lawrence Livermore National Lab in California and a member of the study team.

GreenGen uses integrated gasification combined cycle (IGCC) technology that is supposed to facilitate carbon capture. According to the feasibility study, GreenGen is currently selling 0.1 MT of captured CO2 per year to beverage producers, and is preparing to increase the amount it captures to between 1 and 2 MT per year. While the China Huaneng Group, which is GreenGen’s majority stakeholder, has previously said it would sell its CO2 for use in enhanced oil recovery, the U.S. and Chinese research team was tasked with quickly evaluating whether CO2 could be safely stored in saline aquifers around Tianjin that are bounded by numerous geological faults.

The study found that removing water would substantially lower the risk of CO2 leakage and simultaneously provide an economically viable source of industrial water.

The report conservatively estimates the cost of purifying the relatively dilute water at RMB14-18 ($2.28-2.93) per cubic meter. That figure is twice the cost of desalinating seawater in California, but Bourcier says the real cost is likely much lower, perhaps as low as 50 cents per cubic meter. Either way, he says, it's “small potatoes” within the total operating budget of a coal-fired power station. 

The optimal CO2 injection site Bourcier et al identified is 8 kilometers from the Tianjin plant site. According to their plan, before injection would begin in the 2-kilometer-deep aquifer, water would be extracted for six months. Thereafter, CO2 injection at that site would be accompanied by ongoing water removal via additional wells a few kilometers away (see image above). Bourcier says the binational team has been asked to deliver more precise numbers by mid-December; the operation could be running within a year if it gets a green light. 

Chinese researchers, meanwhile, are evaluating alternate sites for an enhanced water recovery demonstration. Qi Li, a professor at the Chinese Academy of Sciences' Institute of Rock and Soil Mechanics in Wuhan, recently completed a national assessment of Chinese CCS potential. Qi told me via e-mail earlier this year that he is seeking funds for a demonstration in Western China's Xinjiang Province.

Xinjiang is not just where Li found the greatest capacity for CO2 storage in saline aquifers (44,680 megatons) and the most potential for enhanced water recovery (355 billion gallons). Xinjiang also has China's second largest coal reserves and a dearth of potable water supplies. The province is a target for coal-based chemical and liquid fuels production, which consumes roughly 10 tons of water for every ton of product. But demand for potable water there is already several times greater than its sustainable supply. Qi makes the case for Xinjiang's predicament/opportunity in this 2013 presentation.

Bourcier, meanwhile, is looking for opportunities to demonstrate enhanced water recovery in the United States. His group is interested in a saline aquifer near Bakersfield, California, that has a risk profile similar to the Chinese site. As Bourcier puts it, there would be no shortage of takers for the recovered water: “It is an opportune time to have a freshwater by-product in California.”

World’s Biggest Dump Truck Goes Electric

A massive vehicle that can haul loads weighing more than 500 metric tons—the equivalent of 350 VW Golfs—just hit the work site in Siberia, claiming the title of the world’s largest dump truck.

But it has another claim that makes it even more impressive: an electric drive motor. Electric-powered vehicles have been around to do heavy lifting in mines for years, but those trucks, known as trolley trucks, received their electricity from overhead power lines.

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