Four-in-One ‘Universal Wind Turbine’ in development

Nuclear Plant Climate Risks span flood risk, heat stress, and water scarcity, threatening operations, safety systems, and steam generation; resilience depends on mitigation investments, cooling-water management, and adaptive maintenance strategies.

Key Points

Climate-driven threats to nuclear plants: floods, heat, and water stress requiring resilience and mitigation.

✅ Flooding threats to safety and cooling systems

✅ Heat stress reduces thermal efficiency and output

✅ Water scarcity risks limit cooling capacity

Climate change can affect every aspect of nuclear plant operations like fuel handling, power and steam generation and the need for resilient power systems planning, maintenance, safety systems and waste processing, the credit rating agency said.

However, the ultimate credit impact will depend upon the ability of plant operators to invest in carbon-free electricity and other mitigating measures to manage these risks, it added.
Close proximity to large water bodies increase the risk of damage to plant equipment that helps ensure safe operation, the agency said in a note.

Moody’s noted that about 37 gigawatts (GW) of U.S. nuclear capacity is expected to have elevated exposure to flood risk and 48 GW elevated exposure to combined rising heat, extreme heat costs and water stress caused by climate change.

Parts of the Midwest and southern Florida face the highest levels of heat stress, while the Rocky Mountain region and California face the greatest reduction in the availability of future water supply, illustrating the need for adapting power generation to drought strategies, it said.

Nuclear plants seeking to extend their operations by 20, or even 40 years, beyond their existing 40-year licenses in support of sustaining U.S. nuclear power and decarbonization face this climate hazard and may require capital investment adjustments, Moody’s said, as companies such as Duke Energy climate report respond to investor pressure for climate transparency.

“Some of these investments will help prepare for the increasing severity and frequency of extreme weather events, highlighting that the US electric grid is not designed for climate impacts today.”

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Canadian Hydropower Transmission delivers HVDC clean energy via New England Clean Energy Connect and Champlain Hudson Power Express, linking HydroQuébec to Maine and New York grids for renewable energy, decarbonization, and lower wholesale electricity rates.

Key Points

HVDC delivery of HydroQuébec power to New England and New York via NECEC and CHPE, cutting emissions and costs.

✅ 1,200 MW via NECEC; 1,000 MW via CHPE.

✅ HVDC routes: 145-mile NECEC and 333-mile CHPE.

✅ Debates: land impacts, climate justice, wholesale rates.

As the sole residents of unorganized territory T5 R7 deep within Maine's North Woods, Duane Hanson and his wife, Sally Kwan, have watched the land around them—known for its natural beauty, diverse wildlife and recreational fishing—transformed by decades of development. 

But what troubles them most is what could happen in the next few months. State and corporate officials are pushing for construction of a 53-mile-long power line corridor cutting right through the woods and abutting the wild lands surrounding Hanson's property. 

If its proponents succeed, Hanson fears the corridor may represent the beginning of the end of his ability to live "off the land" away from the noise of technology-obsessed modern society. Soon, that noise may be in his backyard. 

"I moved here to be in the pristine wilderness," said Hanson.
 
With his life in what he considers the last "wild" place left on the East Coast on the line, the stakes have never felt higher to Hanson—and many across New England, as well.

The corridor is part of the New England Clean Energy Connect, one of two major and highly controversial transmission line projects meant to deliver Canadian hydropower from the government-owned utility HydroQuébec, in a province that has closed the door on nuclear power, to New England electricity consumers. 

As New England states rush to green their electric grids and combat the accelerating climate crisis, the simultaneous push from Canada to expand the market for hydroelectric power from its vast water resources, including Manitoba's clean energy, has offered these states a critical lifeline at just the right moment. 

The other big hydropower transmission line project will deliver 1,000 megawatts of power, or enough to serve approximately one million residential customers, to the New York City metropolitan area, which includes the city, Long Island, and parts of the Hudson Valley, New Jersey, Connecticut and Pennsylvania. 

The 333-mile-long Champlain Hudson Power Express project will consist of two high voltage direct current cables running underground and underwater from Canada, beneath Lake Champlain and the Hudson River, to Astoria, Queens. 

There, the Champlain Hudson project will interconnect to a sector of the New York electricity grid where city and corporate officials say the hydropower supplied can help reduce the fossil fuels that currently comprise significantly more of the base load than in other parts of the state. Though New York has yet to finalize a contract with HydroQuébec over its hydropower purchase, developers plan to start construction on the $2.2 billion project in 2021 and say it will be operational in 2025. 

The New England project consists of 145 miles of new HVDC transmission line that will run largely above ground from the Canadian border, through Maine to Massachusetts. The $1 billion project, funded by Massachusetts electricity consumers, is expected to deliver 1,200 megawatts of clean energy to the New England energy grid, becoming the region's largest clean energy source. 

Central Maine Power, which will construct the Maine transmission corridor, says the project will decrease wholesale electric rates and create thousands of jobs. Company officials expect to receive all necessary permits and begin construction by the year's end, with the project completed and in service by 2020. 

With only months until developers start making both projects on-the-ground realities, they have seized public attention within, and beyond, their regions. 

Hanson is one among many concerned New England and New York residents who've joined the ranks of environmental activists in a contentious battle with public and corporate officials over the place of Canadian hydropower in their states' clean energy futures. 

Officials and transmission line proponents say importing Canadian hydropower offers an immediate and feasible way to help decarbonize electricity portfolios in New York and New England and to address existing transmission constraints that limit cross-border flows today, supporting their broader efforts to combat climate change. 

But some environmental activists say hydropower has a significant carbon footprint of its own. They fear the projects will make states look "greener" at the expense of the local environment, Indigenous communities, and ultimately, the climate. 

"We're talking about the most environmentally and economically just pathway" to decarbonization, said Annel Hernandez, associate director of the NYC Environmental Justice Alliance. "Canadian hydro is not going to provide that." 

To that end, environmental groups opposing Canadian hydropower say New York and New England should seize the moment to expedite local development of wind and solar power. 

Paul Gallay, president of the nonprofit environmental organization Riverkeeper—which withdrew its initial support for the Champlain Hudson Power Express last November— believes New York has the capacity to develop enough in-state renewable energy sources to meet its clean energy goals, without the new transmission line. 

Yet New York City's analysis shows clearly that Canadian hydropower is critical for its clean energy strategy, said Dan Zarrilli, director of OneNYC and New York City's chief climate policy adviser. 

"We need every bit of clean energy we can get our hands on," he said, to meet the city's goal of carbon neutrality by 2050 and help achieve the state's clean energy mandates. 

Removing Canadian hydropower from the equation, said Zarilli, would commit the city to the "unacceptable outcome" of burning more gas. The city's marginalized communities would likely suffer most from the resulting air pollution and associated health impacts. 

While the two camps debate Canadian hydropower's carbon footprint and what climate justice requires, this much is clear: When it comes to pursuing a zero-carbon future, there are no easy answers. 

Hydropower's Carbon Footprint
Many people take for granted that because hydropower production doesn't involve burning fossil fuels, it's a carbon-neutral endeavor. But that's not always the case, depending on where hydropower is sourced. 

Large-scale hydropower projects often involve the creation of hydroelectric dams and reservoirs, and, in some cases, repowering existing dams to generate clean electricity. The release and flow of water from the reservoir through the dam provides the energy necessary to generate hydropower, which long-distance power lines, or transmission lines, carry to its intended destination—in this case, New England and New York. 

The initial process of flooding land to create a hydroelectric reservoir can have a sizable carbon footprint, especially in heavily vegetated areas. It causes the vegetation and soil underwater to decompose, releasing carbon dioxide and methane—a greenhouse gas 84 times more potent over a 20-year period than carbon dioxide. 

Hydropower accounts for 60 percent of Canada's electricity generation, and HydroQuébec has planned to increase capacity to 37,000 MW in 2021, with the nation second only to China in the percentage of the world's total hydroelectricity it generates. By contrast, hydropower only accounts for seven percent of U.S. utility-scale electricity generation, making it a foreign concept to many Americans. 

As New England works to introduce substantial amounts of Canadian hydropower to its electricity grid, hydropower proponents are promoting it as a prime source for clean electricity, and new NB Power agreements are expanding regional transfers within Canada as well. 

Last fall, Central Maine Power formed its own political action committee, Clean Energy Matters, to advance the New England hydropower project. Together with HydroQuébec, the Maine utility has spent nearly $17 million campaigning for the project this year. 

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Utility Battery Storage Rankings measure grid-connected capacity, not ownership, highlighting MW, MWh, and watts per customer across PJM, MISO, and California IOUs, featuring Duke Energy, IPL, ancillary services, and frequency regulation benefits.

Key Points

Rankings that track energy storage connected to utility grids, comparing MW, MWh, and W/customer rather than ownership.

✅ Ranks by MW, MWh, and watts per customer, not asset ownership

✅ Highlights PJM, MISO cases and California IOUs' deployments

✅ Examples: Duke Energy, IPL, IID; ancillary services, frequency response

The rankings do not tally how much energy storage a utility built or owns, but how much was connected to their system. So while IPL built and owns the storage facility in its territory, Duke does not own the 16 MW of storage that connected to its system in 2016. Similarly, while California’s utilities are permitted to own some energy storage assets, they do not necessarily own all the storage facilities connected to their systems.

Measured by energy (MWh), IPL ranked fourth with 20 MWh, and Duke Energy Ohio ranked eighth with 6.1 MWh.

Ranked by energy storage watts per customer, IPL and Duke actually beat the California utilities, ranking fifth and sixth with 42 W/customer and 23 W/customer, respectively.

Duke ready for next step

Given Duke’s plans, including projects in Florida that are moving ahead, the utility is likely to stay high in the rankings and be more of a driving force in development. “Battery technology has matured, and we are ready to take the next step,” Duke spokesman Randy Wheeless told Utility Dive. “We can go to regulators and say this makes economic sense.”

Duke began exploring energy storage in 2012, and until now most of its energy storage efforts were focused on commercial projects in competitive markets where it was possible to earn revenues. Those included its 36 MW Notrees battery storage project developed in partnership with the Department of Energy in 2012 that provides frequency regulation for the Electric Reliability Council of Texas market and two 2 MW storage projects at its retired W.C. Beckjord plant in New Richmond, Ohio, that sells ancillary services into the PJM Interconnection market.

On the regulated side, most of Duke’s storage projects have had “an R&D slant to them,” Wheeless said, but “we are moving beyond the R&D concept in our regulated territory and are looking at storage more as a regulated asset.”

“We have done the demos, and they have proved out,” Wheeless said. Storage may not be ready for prime time everywhere, he said, but in certain locations, especially where it can it can be used to do more than one thing, it can make sense.

Wheeless said Duke would be making “a number of energy storage announcements in the next few months in our regulated states.” He could not provide details on those projects.

More flexible resources
Location can be a determining factor when building a storage facility. For IPL, serving the wholesale market was a driving factor in the rationale to build its 20 MW, 20 MWh storage facility in Indianapolis.

IPL built the project to address a need for more flexible resources in light of “recent changes in our resource mix,” including decreasing coal-fired generation and increasing renewables and natural gas-fired generation, as other regions plan to rely on battery storage to meet rising demand, Joan Soller, IPL’s director of resource planning, told Utility Dive in an email. The storage facility is used to provide primary frequency response necessary for grid stability.

The Harding Street storage facility in May. It was the first energy storage project in the Midcontinent ISO. But the regulatory path in MISO is not as clear as it is in PJM, whereas initiatives such as Ontario storage framework are clarifying participation. In November, IPL with the Federal Energy Regulatory Commission, asking the regulator to find that MISO’s rules for energy storage are deficient and should be revised.

Soller said IPL has “no imminent plans to install energy storage in the future but will continue to monitor battery costs and capabilities as potential resources in future Integrated Resource Plans.”

California legislative and regulatory push

In California, energy storage did not have to wait for regulations to catch up with technology. With legislative and regulatory mandates, including CEC long-duration storage funding announced recently, as a push, California’s IOUs took high places in SEPA’s rankings.

Southern California Edison and San Diego Gas & Electric were first and fourth (63.2 MW and 17.2 MW), respectively, in terms of capacity. SoCal Ed and SDG&E were first and second (104 MWh and 28.4 MWh), respectively, and Pacific Gas and Electric was fifth (17 MWh) in terms of energy.

But a public power utility, the Imperial Irrigation District (IID), ended up high in the rankings – second in capacity (30 MW) and third  in energy (20 MWh) – even though as a public power entity it is not subject to the state’s energy storage mandates.

But while IID was not under state mandate, it had a compelling regulatory reason to build the storage project. It was part of a settlement reached with FERC over a September 2011 outage, IID spokeswoman Marion Champion said.

IID agreed to a $12 million fine as part of the settlement, of which $9 million was applied to physical improvements of IID’s system.

IID ended up building a 30 MW, 20 MWh lithium-ion battery storage system at its El Centro generating station. The system went into service in October 2016 and in May, IID used the system’s 44 MW combined-cycle natural gas turbine at the generating station.

Passing savings to customers
The cost of the storage system was about $31 million, and based on its experience with the El Centro project, Champion said IID plans to add to the existing batteries. “We are continuing to see real savings and are passing those savings on to our customers,” she said.

Champion said the battery system gives IID the ability to provide ancillary services without having to run its larger generation units, such as El Centro Unit 4, at its minimum output. With gas prices at $3.59 per million British thermal units, it costs about $26,880 a day to run Unit 4, she said.

IID’s territory is in southeastern California, an area with a lot of renewable resources. IID is also not part of the California ISO and acts as its own balancing authority. The battery system gives the utility greater operational flexibility, in addition to the ability to use more of the surrounding renewable resources, Champion said.

In May, IID’s board gave the utility’s staff approval to enter into contract negotiations for a 7 MW, 4 MWh expansion of its El Centro storage facility. The negotiations are ongoing, but approval could come in the next couple months, Champion said.

The heart of the issue, though, is “the ability of the battery system to lower costs for our ratepayers,” Champion said. “Our planning section will continue to utilize the battery, and we are looking forward to its expansion,” she said.” I expect it will play an even more important role as we continue to increase our percentage of renewables.”

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FERC DER Aggregation advances debates over distributed energy resources as Congress presses action on Order 841, grid resilience, and wholesale market access, including rooftop solar, storage, and virtual power plant participation across PJM and ISO-NE.

Key Points

FERC DER Aggregation enables grouped distributed resources to join wholesale markets, providing capacity and flexibility.

✅ Opens wholesale market access for aggregated DER portfolios

✅ Aligns with Order 841, storage, and grid resilience goals

✅ Raises jurisdictional questions between FERC and state regulators

The Monday letter from Congressional Democrats illustrates growing frustration in Washington over the lack of FERC action on multiple power sector issues, including the aging U.S. grid and related challenges.

Last May, after the FERC technical conference, 16 Democratic Senators wrote to then-Chairman Kevin McIntyre urging him to develop guidance for grid operators on aggregated DERs.

In July, McIntyre responded, saying that FERC was "diligently reviewing the record," but the commission has taken no action since.

Since then, "DER adoption and renewable energy aggregation have continued to grow," House and Senate lawmakers wrote in their identical Monday letters, "driven not only by state and federal policies, but consumer interest in choosing cost-competitive technologies such as rooftop solar, smart thermostats and customer-sited energy generation and storage, reflecting key utility trends in the sector."

The lawmakers wrote they were "encouraged" by FERC Chairman Neil Chatterjee's comments in June 2018, writing that he "specifically cited the role DERs will play in our continued grid transition."

In that speech at the S&P Global Platts 2018 Transmission Planning and Development Conference, Chatterjee noted "growing interest" in non-transmission alternatives, including "DERs and storage."

"How the Commission treats filings associated with those first-of-kind projects could prove an important factor in investors’ assessments of whether similar non-traditional projects are bankable or not — and more broadly signal whether FERC is open to innovation in the transmission sector,” he said.

In addition to the DER order and rehearing decision on Order 841, FERC has multiple other power sector initiatives that have not seen official action in months, even as major changes to electricity pricing are debated by stakeholders.

The highest profile is its open proceeding on grid resilience, set up last January after FERC rejected a coal and nuclear bailout proposal from the Department of Energy. In October, the CEO of the PJM Interconnection, the nation’s largest wholesale power market, urged FERC to issue a final order in the docket, calling for "leadership" from the commission.

Chatterjee, however, has not indicated when FERC could decide on the case. In December, Commissioner Rich Glick told a Washington audience he is "not entirely sure where the chairman wants to go with that proceeding yet."

Outside of resilience, FERC also has open reviews of both its pipeline certificate policy and implementation of the Public Utilities Regulatory Policy Act, a key law supporting renewable energy. McIntrye set those reviews in motion during his tenure as chairman, but after his death in January the timing of both remains unclear.

In recent months, Chatterjee has also delayed FERC votes on major export facilities for liquefied natural gas and a political spending case involving PJM after impasses between Republicans and Democrats on FERC.

Two members from each party currently sit on the commission. That allows Democrats to deadlock commission votes on natural gas facilities and other issues — a partisan divide on display this week when they clashed with the chairman over offshore wind.

As the commission considers final guidance on DERs, the boundaries of federal jurisdiction are likely to be a key issue. At the technical conference, states from the Midcontinent ISO argued FERC should allow them to choose whether to let aggregated DERs participate in retail and wholesale markets. Other states argued the value proposition of distributed resources may rely on that sort of dual participation.

Despite the lack of action from FERC, some grid operators are moving forward with aggregated distributed resources in New England market reform efforts and elsewhere, demonstrating momentum. Last week, a residential solar-plus-storage aggregation cleared the ISO-NE capacity auction for the first time, committing to provide 20 MW of capacity beginning in 2022.

On the Senate side, Sens. Sheldon Whitehouse, R.I., and Ed Markey, Mass., led the letter to FERC. In the House, Reps. Peter Welch, Vt., and Mike Levin, Calif., led the signatories.

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U.S. Natural Gas Power Demand is surging for electricity generation amid summer heat, with ERCOT, Texas grid reserves tight, EIA reporting coal and nuclear retirements, renewables intermittency, and pipeline expansions supporting combined-cycle capacity and prices.

Key Points

It is rising use of natural gas for power, driven by summer heat, plant retirements, and new combined-cycle capacity.

✅ ERCOT reserve margin 9%, below 14% target in Texas

✅ Gas share of U.S. power near 40-43% this summer

✅ Coal and nuclear retirements shift capacity to combined cycle

As the hot months linger, it will be natural gas that is leaned on most to supply the electricity that we need to run our air conditioning loads on the grid and keep us cool.

And this is surely a great and important thing: "Heat causes most weather-related deaths, National Weather Service says."

Generally, U.S. gas demand for power in summer is 35-40% higher than what it was five years ago, with so much more coming (see Figure).

The good news is regions across the country are expected to have plenty of reserves to keep up with power demand.

The only exception is ERCOT, covering 90% of the electric load in Texas, where a 9% reserve margin is expected, below the desired 14%.

Last summer, however, ERCOT’s reserve margin also was below the desired level, yet the grid operator maintained system reliability with no load curtailments.

Simply put, other states are very lucky that Texas has been able to maintain gas at 50% of its generation, despite being more than justified to drastically increase that.

At about 1,600 Bcf per year, the flatness of gas for power demand in Texas since 2000 has been truly remarkable, especially since Lone Star State production is up 50% since then.

Increasingly, other U.S. states (and even countries) are wanting to import huge amounts of gas from Texas, a state that yields over 25% of all U.S. output.

Yet if Texas justifiably ever wants to utilize more of its own gas, others would be significantly impacted.

At ~480 TWh per year, if Texas was a country, it would be 9th globally for power use, even ahead of Brazil, a fast growing economy with 212 million people, and France, a developed economy with 68 million people.

In the near-term, this explains why a sweltering prolonged heat wave in July in Texas, with a hot Houston summer setting new electricity records, is the critical factor that could push up still very low gas prices.

But for California, our second highest gas using state, above-average snowpack should provide a stronger hydropower for this summer season relative to 2018.

Combined, Texas and California consume about 25% of U.S. gas, with Texas' use double that of California.

Across the U.S., gas could supply a record 40-43% of U.S. electricity this summer even as the EIA expects solar and wind to be larger sources of generation across the mix

Our gas used for power has increased 35-40% over the past five years, and January power generation also jumped on the year, highlighting broad momentum.

Our gas used for power has increased 35-40% over the past five years. DATA SOURCE: EIA; JTC

Indeed, U.S. natural gas for electricity has continued to soar, even as overall electricity consumption has trended lower in some years, at nearly 10,700 Bcf last year, a 16% rise from 2017 and easily the highest ever.

Gas is expected to supply 37% of U.S. power this year, even as coal-fired generation saw a brief uptick in 2021 in EIA data, versus 27% just five years ago (see Figure).

Capacity wise, gas is sure to continue to surge its share 45% share of the U.S. power system.

"More than 60% of electric generating capacity installed in 2018 was fueled by natural gas."

We know that natural gas will continue to be the go-to power source: coal and nuclear plants are retiring, and while growing, wind and solar are too intermittent, geography limited, and transmission short to compensate like natural gas can.

"U.S. coal power capacity has fallen by a third since 2010," and last year "16 gigawatts (16,000 MW) of U.S. coal-fired power plants retired."

This year, some 2,000 MW of coal was retired in February alone, with 7,420 MW expected to be closed in 2019.

Ditto for nuclear.

Nuclear retirements this year include Pilgrim, Massachusetts’s only nuclear plant, and Three Mile Island in Pennsylvania.

This will take a combined ~1,600 MW of nuclear capacity offline.

Another 2,500 MW and 4,300 MW of nuclear are expected to be leaving the U.S. power system in 2020 and 2021, respectively.

As more nuclear plants close, EIA projects that net electricity generation from U.S. nuclear power reactors will fall by 17% by 2025.

From 2019-2025 alone, EIA expects U.S. coal capacity to plummet nearly 25% to 176,000 MW, with nuclear falling 15% to 83,000 MW.

In contrast, new combined cycle gas plants will grow capacity almost 30% to around 310,000 MW.

Lower and lower projected commodity prices for gas encourage this immense gas build-out, not to mention non-stop increases in efficiency for gas-based units.

Remember that these are official U.S. Department of Energy estimates, not coming from the industry itself.

In other words, our Department of Energy concludes that gas is the future.

Our hotter and hotter summers are therefore more and more becoming: "summers for natural gas"

Ultimately, this shows why the anti-pipeline movement is so dangerous.

"Affordable Energy Coalition Highlights Ripple Effect of Natural Gas Moratorium."

In April, President Trump signed two executive orders to promote energy infrastructure by directing federal agencies to remove bottlenecks for gas transport into the Northeast in particular, where New England oil-fired generation has spiked, and to streamline federal reviews of border-crossing pipelines and other infrastructure.

Builders, however, are not relying on outside help: all they know is that more U.S. gas demand is a constant, so more infrastructure is mandatory.

They are moving forward diligently: for example, there are now some 27 pipelines worth $33 billion already in the works in Appalachia.

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Carbon Nanotube Solvent Electricity enables wire-free electrochemistry as organic solvents like acetonitrile pull electrons, powering alcohol oxidation and packed bed reactors, energy harvesting, and micro- and nanoscale robots via redox-driven current.

Key Points

Solvent-driven electron extraction from carbon nanotube particles generates current for electrochemistry.

✅ 0.7 V per particle via solvent-induced electron flow

✅ Packed bed reactors drive alcohol oxidation without wires

✅ Scalable for micro- and nanoscale robots; energy harvesting

MIT engineers have discovered a new way of generating electricity, alongside advances in renewable power at night that broaden what's possible, using tiny carbon particles that can create a current simply by interacting with liquid surrounding them.

The liquid, an organic solvent, draws electrons out of the particles, generating a current, unlike devices based on a cheap thermoelectric material that rely on heat, that could be used to drive chemical reactions or to power micro- or nanoscale robots, the researchers say.

"This mechanism is new, and this way of generating energy is completely new," says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. "This technology is intriguing because all you have to do is flow a solvent through a bed of these particles. This allows you to do electrochemistry, but with no wires."

In a new study describing this phenomenon, the researchers showed that they could use this electric current to drive a reaction known as alcohol oxidation—an organic chemical reaction that is important in the chemical industry.

Strano is the senior author of the paper, which appears today in Nature Communications. The lead authors of the study are MIT graduate student Albert Tianxiang Liu and former MIT researcher Yuichiro Kunai. Other authors include former graduate student Anton Cottrill, postdocs Amir Kaplan and Hyunah Kim, graduate student Ge Zhang, and recent MIT graduates Rafid Mollah and Yannick Eatmon.

Unique properties
The new discovery grew out of Strano's research on carbon nanotubes—hollow tubes made of a lattice of carbon atoms, which have unique electrical properties. In 2010, Strano demonstrated, for the first time, that carbon nanotubes can generate "thermopower waves." When a carbon nanotube is coated with layer of fuel, moving pulses of heat, or thermopower waves, travel along the tube, creating an electrical current that exemplifies turning thermal energy into electricity in nanoscale systems.

That work led Strano and his students to uncover a related feature of carbon nanotubes. They found that when part of a nanotube is coated with a Teflon-like polymer, it creates an asymmetry, distinct from conventional thermoelectric materials approaches, that makes it possible for electrons to flow from the coated to the uncoated part of the tube, generating an electrical current. Those electrons can be drawn out by submerging the particles in a solvent that is hungry for electrons.

To harness this special capability, the researchers created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side of each sheet was coated with a Teflon-like polymer, and the researchers then cut out small particles, which can be any shape or size. For this study, they made particles that were 250 microns by 250 microns.

When these particles are submerged in an organic solvent such as acetonitrile, the solvent adheres to the uncoated surface of the particles and begins pulling electrons out of them.

"The solvent takes electrons away, and the system tries to equilibrate by moving electrons," Strano says. "There's no sophisticated battery chemistry inside. It's just a particle and you put it into solvent and it starts generating an electric field."

Particle power
The current version of the particles can generate about 0.7 volts of electricity per particle. In this study, the researchers also showed that they can form arrays of hundreds of particles in a small test tube. This "packed bed" reactor, unlike thin-film waste-heat harvesters for electronics, generates enough energy to power a chemical reaction called an alcohol oxidation, in which an alcohol is converted to an aldehyde or a ketone. Usually, this reaction is not performed using electrochemistry because it would require too much external current.

"Because the packed bed reactor is compact, it has more flexibility in terms of applications than a large electrochemical reactor," Zhang says. "The particles can be made very small, and they don't require any external wires in order to drive the electrochemical reaction."

In future work, Strano hopes to use this kind of energy generation to build polymers using only carbon dioxide as a starting material. In a related project, he has already created polymers that can regenerate themselves using carbon dioxide as a building material, in a process powered by solar energy and informed by devices that generate electricity at night as a complement. This work is inspired by carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide, using energy from the sun.

In the longer term, this approach could also be used to power micro- or nanoscale robots. Strano's lab has already begun building robots at that scale, which could one day be used as diagnostic or environmental sensors. The idea of being able to scavenge energy from the environment, including approaches that produce electricity 'out of thin air' in ambient conditions, to power these kinds of robots is appealing, he says.

"It means you don't have to put the energy storage on board," he says. "What we like about this mechanism is that you can take the energy, at least in part, from the environment."

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