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Monitoring Nuclear Fuel With Sound

Nuclear reactors are packed with a host of sensing and control systems. But at their innermost core, where nuclear fuel burns inside metal rods, conditions are so extreme that placing any kind of sensor has been a huge challenge. As a result, reactor operators haven't been able to get a complete picture of how their nuclear cores are performing.

Now researchers have developed sensors that convert the heat differences inside the reactors into whistle-like sounds that reveal the condition of the fuel. These thermoacoustic sensors could provide operators with valuable data like temperature, gas composition, and pressure inside the fuel rods, as well as fuel burn-up rate and swelling of the rods.

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DOE Spends $141 Million to Speed Offshore Wind Project Development

Though the actual waters off of the United States' windy shores remains free of turbines (with one minor exception), the theoretical waters are getting crowded with turbines. Along with frontrunners Cape Wind and Deepwater Wind near Massachusetts and Rhode Island, a few other projects are starting to get the sort of backing that will help them join the party. Yesterday, the Department of Energy announced funding of up to $47 million each for three projects off of New Jersey, Virginia, and Oregon.

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U.S. Climate Report Predicts Growing Problems for Energy Sector

More frequent and intense weather events—from hurricanes to wildfires to sweltering summers—can be attributed to climate change and are affecting energy production and power delivery in the United States, according to a new government report.

The latest National Climate Assessment, prepared by the U.S. National Climate Assessment and Development Advisory Committee (NCADAC) and released yesterday, says that climate-related effects are not only already being felt but will likely get worse.

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Two Labs Get the Lead Out of Promising Perovskite Solar Cells

Photovoltaic cells made from perovskite materials have rapidly become one of the hottest areas in energy research over the past few years. But most of these materials have included the toxic metal lead, raising concerns about their environmental impact.

Now, two teams have independently developed perovskite cells that swap lead for tin, which could help to convince investors and regulators that the cells have a commercial future.

Perovskite materials are named after the common crystal structure they share with a naturally occurring mineral. Cells using the material made a modest debut in 2009, reaching energy conversion efficiencies of 3.8 percent.

But they were soon leaping ahead, rising to 10 percent efficiency in 2012, and 15 percent by 2013. The same year, Henry Snaith at the University of Oxford, UK, unveiled a perovskite cell that reached 15 percent efficiency, but with a much simpler design. His device relied on a thin film of methyl­ammonium lead iodide chloride to do double duty as both light absorber and charge carrier. Since then, photovoltaic cell efficiencies have ticked up further, to 17.9 percent—an advance achieved by Sang Il Seok at the Korean Research Institute of Chemical Technology in Daejeon.

This efficiency already rivals that of bulkier silicon cells, and is gaining fast on thin-film photovoltaic cells that use materials such as copper indium gallium selenide (CIGS). The unprecedented progress is made all the sweeter by the fact that these perovskites are extremely stable, use cheap and abundant materials, and are simple to incorporate into cells.

But using lead-based materials was obviously not ideal. There were only small amounts of lead in each cell, but enough to have a significant environmental impact if they were deployed widely around the world. Researchers worried that this might limit their use. “It’s a problem when it comes to convincing investors,” says Mercouri Kanatzidis, a chemist at Northwestern University, Evanston, Illinois.

Snaith has now reported in Energy and Environmental Science that a cell made from methyl­ammonium tin iodide, which is lead-free, is about 6 percent efficient. Just days later, Kanatzidis independently reported very similar results in Nature Photonics using methyl­ammonium tin iodide bromide.

One major drawback is that tin perovskites are unstable, and must be handled under an inert atmosphere. But Kanatzidis says that the necessary processing methods are already well-established in industry, and that the cells are fairly stable once sealed in an air-tight housing. He is also confident that tin perovskites can be pushed far above 6 percent efficiency. “There’s no showstopper,” he says.

Tin perovskites might offer an insurance policy if lead perovskites do turn out to be an environmental problem. But looking for alternative metals is also smart science, because they might actually improve the cells’ performance. The tin-based cells, for example, actually produce a higher voltage than the original lead perovskite cells. “It may well be that tin ends up being higher efficiency,” says Snaith.

The similarities between the results from the two labs highlights the frenzied pace of the field. “The competition is amazing,” says Snaith. “You can’t assume you’re doing anything unique.”

Snaith has cofounded a start up, Oxford Photovoltaics, to commercialize his perovskite cells, and Kanatzidis is talking to solar PV manufacturers about his tin tech. But both agree that the biggest hurdle for commercial deployment of the cells is their long-term stability. “The biggest question is whether we can make these things stable for 25 years,” says Snaith.

NASA Uses Transmission Lines For Geomagnetic Antenna Study

Not all threats to the electric grid originate here on Earth. To better understand large solar events, which can be dangerous to the transmission grid, a researcher at NASA’s Goddard Space Flight Center is using high-voltage transmission lines to map large-scale geomagnetically-induced currents (GICs).

GICs occur when the sun ejects huge bubbles of charged particles that can carry up to 10 billion tons of matter. When the bubbles strike the Earth’s atmosphere, the geomagnetic field that surrounds our planet fluctuates.

These fluctuations in the electrical current can then flow through any large conductive structure such as power lines, oil and gas pipelines, undersea cables, and railways, according to NASA. When excess current flows through the electric transmission system, it can overload transformers and collapse the system, leading to large-scale outages. From 1960 to 2000, the high voltage grid in the United States has grown nearly tenfold, according Oak Ridge National Laboratory [PDF], making it increasingly susceptible to GICs.

The concern that a large GIC could plunge part of the United States into a blackout is high on the list of issues faced by the Federal Energy Regulatory Commission (FERC), and is as much of a focus as physical or cyber security threats.

Last year, FERC ordered the North American Reliability Corporation to propose reliability standards for the grid that address the impact of geomagnetic disturbances; owners of the bulk-power grid will have to conduct assessments of the potential impact of GICs on their systems moving forward.

To better understand the effects of GICs, Antti Pulkkinen, a heliophysicst at Goddard, is installing three substations beneath high-voltage transmission lines to measure GICs.

“This is the first time we have used the U.S. high-voltage power transmission system as a science tool to map large-scale GICs,” Pulkkinen said in the NASA publication Cutting Edge [PDF]. “This application will allow unprecedented, game-changing data gathering over a wide range of spatial and temporal scales.”

Two of the three substations being built by Goddard engineers will be buried 1.2 meters below ground at a spot where Dominion Virginia Power’s high-voltage lines pass overhead. The lines will act as antennae for the electrical current. The substations will contain commercially available magnetometers that can make precise measurements of GICs. (The third substation will be located about three kilometers away to provide reference measurements.)

Pulkkinen’s team is using technology also developed at Goddard to command and control the magnetometers from an iPad. The application, which tags and geolocates data, will send it to a server once every second.

The pilot project is expected to last one to two years, but Pulkkinen hopes to eventually deploy hundreds of substations with long-term funding from multiple government agencies. The current project is funded by NASA’s Center Innovation Fund and Goddard International Research and Development program.

GE's Distributed Power Station Delivery Goes From Months to Weeks

When utilities needed new sources of power in the past, they planned for large, capital-intensive centralized generation that could take years to build and decades to pay off.

Big power plants are still being built, but many utilities are increasingly looking for smaller, more flexible solutions. In Libya, the General Electricity Company of Libya (GECOL), recently installed mobile backup power plants from General Electric (GE) in a matter of weeks, instead of the six-to-nine months usually required.

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U.S. Energy Department Offering $4 Billion for Renewable Energy Loans

Biofuels made from leftover corn may not be any better than conventional gasoline in terms of greenhouse gas emissions, according to a new study from Nature Climate Change that was paid for by the U.S. government.

In terms of life cycle analysis, fuels made from corn residue release 7 percent more greenhouse gases in a 10-year timeline compared to gasoline, even though they may be better than gas in the long run, according to a report in the Associated Press. The federal government has spent more than US $1 billion supporting cellulosic biofuel research.

Although the fuel stock may change, biofuels continue to be a big focus for the government. Biofuel-based drop-in replacements for gasoline are one of five technology areas that were identified as part of the U.S. Department of Energy’s (DOE) latest renewable energy and energy efficiency solicitation.

The DOE will offer up to $4 billion in loan guarantees to help commercialize technologies that may not be able to obtain full commercial financing, the agency said last week. The program falls under a different section of the law than the part than the one that funded Solyndra.That section,1705, has now expired but had a more than 90 percent success rate across the portfolio despite some significant failures. 

“Through our existing renewable energy loan guarantees, the Department’s Loan Programs Office helped launch the U.S. utility-scale solar industry and other clean energy technologies that are now contributing to our clean energy portfolio,” DOE Secretary Ernest Moniz said in a statement. “We want to replicate that success by focusing on technologies that are on the edge of commercial-scale deployment today.”

The DOE will take applications for any project that meets the eligibility requirements, but it is particularly interested in: 

  • Advanced grid integration and storage
  • Drop-in biofuels
  • Waste-to-energy
  • Enhancement of existing facilities
  • Efficiency improvements.

For biofuels, the DOE noted “qualifying projects may include, but are not limited to, the following: new bio-refineries that produce gasoline, diesel fuel, and/or jet fuel; bio-crude refining processes; and modifications to existing ethanol facilities to gasoline, diesel fuel, and/or jet fuel.”

The U.S. Department of Defense, in particular, is eager for drop-in biofuels to meet its goals. The Navy, for example, has a goal of 50 percent of its liquid fuels will come from alternative sources by 2020.

It is unclear if the findings from the Nature Climate Change study would be considered by the DOE for any applications that are related to corn residue biofuels. According to the AP, other research, including a study by the DOE’s Argonne National Laboratory, has found that corn-based biofuels were still better than gasoline in terms of greenhouse gas emissions.

There will be plenty of other technologies, both other feedstock for biofuels, and other areas of clean tech, that will be vying for the loans. In the first quarter of 2014, more than 90 percent of new power generation was renewable energy, according to the US Federal Energy Regulatory Commission [pdf].

In the area of advanced grid integration and storage projects would help mitigate grid issues caused by intermittent renewable energy. Along the same lines, the DOE's funding for “enhancement of existing facilities” will focus on incorporating renewables into existing generation facilities.

Waste-to-energy applications should focus on projects that turn landfill methane or segregated waste streams, such as forestry waste or crop waste, into energy. Energy efficiency is also a key area, and could fund efficiency in residential, commercia,l or industrial processes or ways that efficiency and demand response could help dispatch underutilized renewable energy.

The DOE is taking public comments until 16 May and the final solicitation will be issued in June.

White Light, Stored Heat

Researchers have developed a new material for solar thermal energy applications, a collector that can serve as its own heat battery. As a result, the technology could help smooth out the production of electricity from solar power over a day and night cycle, or during cloudy weather.

The essential idea, says MIT postdoctoral research associate Timothy Kucharski, involves a molecule containing a kind of spring-wound hinge. Exposing the molecule to a burst of sunlight latches the solar energy in place, like arming a mousetrap. The molecule can then be left idle until its energy is needed, at which point a simple chemical catalytic reaction springs the molecular hinge and releases the stored solar energy as heat.

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Supercapacitor-Enhanced Hybrid Storage to Earn Cash for Subways

A moving train represents a significant amount of energy, which is often lost as carriages slow to stop at a station. Trains in the Philadelphia subway are not only capturing that energy in banks of batteries but also selling it to the local grid operator. This fall, it’ll be capturing even more energy—maybe earning more money from grid operators—because it plans to upgrade the system with a hybrid of both lithium ion batteries and supercapacitors.

The Southeastern Pennsylvania Transit Authority (SEPTA) stores energy produced by braking railway cars, much the way a hybrid car juices its battery when slowing. The spinning wheels turn a motor-generator to charge a bank of batteries via a third rail system. The battery is located at the Lettery substation, which powers a portion of the Market-Frankford Line in Philadelphia, and the autumn upgrade will be installed on the same line about 5 kilometers away.

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Time to Rightsize the Grid?

Last week a team of systems scientists known for counter-intuitive insights on power grids delivered a fresh one that questions one of the tenets of grid design: bigger grids, they argue, may not make for better grids. Iowa State University electrical engineering professor Ian Dobson and physicists David Newman and Ben Carreras make the case for optimal sizing of power grids in last week's issue of the nonlinear sciences journal Chaos. 

In a nutshell, the systems scientists use grid modeling to show that grid benefits such as frequency stabilization and power trading can be outweighed by the debilitating impacts of big blackouts. As grids grow larger, they become enablers for ever larger cascading blackouts. The Northeast Blackout of 2003 was a classic case. From a tripped line in northern Ohio, the outage cascaded in all directions to unplug more than 50 million people from western Michigan and Toronto to New York City.

This week's findings are more conceptual, however, than some news outlets would have us believe. NBC News, in an online article entitled Researchers Suggest It's Time to Downsize Power Grid, misjudged the Chaos report as a call to break up the dual grids that interconnect most of eastern and western North America. "It’s not possible to really make that statement," says Carreras, who runs Oak Ridge, TN-based consulting firm BACV Solutions and is a visiting professor at Madrid's Universidad Carlos III.

B.A. Carreras/BACV Solutions

NBC misinterpreted Carreras et al's simulations showing that grids with just 700-1000 nodes (over 15 times smaller than North America's big grids) maximize interconnection benefits while minimizing blackout costs (see above chart). The researchers say this could indicate that some real grids are too large, but there are two big reasons to be cautious about drawing conclusions. 

Carreras stresses that the model nodes are not necessarily representative of those on a real grid. Many of the group's simulations, for example, use scale models of the Western grid in which each node in the model represents, on average, 10 nodes on the real grid. 

Newman, a physics professor at the University of Alaska in Fairbanks, notes that the specific models used in this Chaos study were idealized, homogeneous systems. As such, he says, they bear little resemblance to the heterogeneity of real grids with their diversity of voltage levels, branching patterns and other features. "700-1000 nodes was the optimal size for the artificial network we had constructed," says Newman.

Media hype is a problem that has dogged this team of system scientists since they gained notoriety over a decade ago by identifying cascading failures as an innate feature of power grids. Their simulations, which a Spectrum cover story profiled ten years ago, show that economic pressure to maximize return on investment loads power grids to levels that leave them at heightened risk of costly blackouts.

The researchers delivered a complex systems view of blackouts that they hoped would spur novel thinking about the costs and benefits in grid design, and novel approaches to blackout prevention. But their message was often misinterpreted as an attack on the quality of grid engineering, or an argument that trying to prevent blackouts was futile. 

Carreras et al argue that this week's report has important conceptual value, if one gets beyond the hype. For one thing, blackout risks should be factored into the cost-benefit calculation when grid planners consider expanded interconnection. This could be applicable in developing countries as well as in Europe, which recently expanded its grid to include Turkey's and is considering extensions to North Africa and Russia.  

It's also possible that grid design could be engineered to enable extended interconnection without expanding cascading blackout risk. Newman points to the possibility that weak links could be deliberately placed within grids to confine cascading blackouts to their region of origin. The team's next step, says Newman, is to study just that possibility by simulating and optimizing heterogeneous networks. 

A correction to this post was made on 23 April 2014: Ian Dobson is at Iowa State University, not the University of Iowa as originally reported.


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