Councillors quit hydro board

By Toronto Star


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Three Mississauga councillors who sit on the board of the city's hydro utility have resigned after their extra salaries were slashed by city council.

In a statement, Councillors Nando Iannicca, Carmen Corbasson and Sue McFadden said they had no choice but to resign, accusing fellow councillors of "crass politics, hypocrisy and cowardice" for cutting their pay.

"The personal attacks by council became an issue of confidence, so we did the honourable thing and resigned," the statement said.

It came one day after the board of Enersource, based on legal advice, decided that only Mississauga, which owns 90 per cent of the utility, and minority shareholder Borealis could determine salaries, not board members themselves.

The saga began in April, when council slashed the salaries of its eight appointees to the 10-member board. Earning $32,000 to $45,000 a year, Enersource's board members had been among the highest paid at a GTA municipal utility. Their pay was slashed by council to $15,000; the chair's pay from $75,000 to $45,000 a year.

Following a quiet rebellion by the three councillors on the board, city council eliminated their salaries for Enersource service altogether, except for a $500 stipend to attend committee meetings.

Borealis had initially vetoed the pay cuts, leading to a tense standoff between the shareholders.

But late in October it agreed to the council-ordered cuts.

Iannicca, Corbasson and McFadden refused to agree to the council-ordered cuts and instead joined the board in seeking the opinion of an outside consultant on their salaries. Just last month, the three refused to sign an "irrevocable" agreement to accept the reduced compensation.

That's when council voted 5-3 to cut their pay (though not of the citizen appointees) down to nothing.

Mayor Hazel McCallion, who also sits on the board, deftly sidestepped criticism by giving up her board salary entirely when the pay issue became controversial earlier this year.

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France nuclear power stations to limit energy output due to high river temps

France Nuclear Heatwave Restrictions signal reduced nuclear power along the Rhone River as EDF imposes output limits due to high water temperatures, grid needs, with minimal price impact amid strong solar and exports.

 

Key Points

Temporary EDF output limits at Rhone River reactors due to hot water, protecting ecosystems and grid reliability.

✅ EDF expects halved output at Bugey and Saint Alban.

✅ Cuts align with water temperature and discharge rules.

✅ Weekend midday curtailments offset by solar supply.

 

The high temperature warning has come early this year but will affect fewer nuclear power plants. High temperatures could halve nuclear power production, with river temperature limits at plants along France's Rhone River this week. 

Output restrictions are expected at two nuclear plants in eastern France due to high temperature forecasts, nuclear operator EDF said. It comes several days ahead of a similar warning that was made last year but will affect fewer plants, and follows a period when power demand has held firm during lockdowns across Europe.

The hot weather is likely to halve the available power supply from the 3.6 GW Bugey plant from 13 July and the 2.6 GW Saint Alban plant from 16 July, the operator said.

However, production will be at least 1.8 GW at Bugey and 1.3 GW at Saint Alban to meet grid requirements, and may change according to grid needs, the operator said.

Kpler analyst Emeric de Vigan said the restrictions were likely to have little effect on output in practice. Cuts are likely only at the weekend or midday when solar output was at its peak so the impact on power prices would be slim.

He said the situation would need monitoring in the coming weeks, however, noting it was unusually early in the summer for nuclear-powered France to see such restrictions imposed.

Water temperatures at the Bugey plant already eclipsed the initial threshold for restrictions on 9 July, as European power hits records during the heatwave. They are currently forecast to peak next week and then drop again, Refinitiv data showed.

"France is currently net exporting large amounts of power – and, despite a nuclear power dispute with Germany, single nuclear units' supply restrictions will not have the same effect as last year," Refinitiv analyst Nathalie Gerl said.

The Garonne River in southern France has the highest potential for critical levels of warming, but its Golfech plant is currently offline for maintenance until mid-August, as Europe faces nuclear losses, the data showed.

"(The restrictions were) to be expected and it will probably occur more often," Greenpeace campaigner Roger Spautz said.

"The authorities must stick to existing regulations for water discharges. Otherwise, the ecosystems will be even more affected," he added.

 

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How Ukraine Will Keep the Lights On This Winter

Ukraine Winter Energy Strategy strengthens the power grid through infrastructure repairs, electricity imports, renewable integration, nuclear output, and conservation to ensure reliable heating, blackout mitigation, and grid resilience with international aid, generators, and transmission lines.

 

Key Points

A wartime plan to stabilize Ukraine's grid via repairs, imports, renewables, and nuclear to deliver reliable electricity.

✅ Repairs, imports, and demand management stabilize the grid.

✅ Renewables and nuclear reduce outage risks in winter.

✅ International aid supplies transformers, generators, expertise.

 

As Ukraine braces for the winter months, the question of how the country will keep the lights on has become a pressing concern, as the country fights to keep the lights on amid ongoing strikes. The ongoing war with Russia has severely disrupted Ukraine's energy infrastructure, leading to widespread damage to power plants, transmission lines, and other critical energy facilities. Despite these challenges, Ukraine has been working tirelessly to maintain its energy supply during the cold winter months, which are essential not only for heating but also for the functioning of homes, businesses, hospitals, and schools. Here's a closer look at the steps Ukraine is taking to keep the lights on this winter and ensure that its people have access to reliable electricity.

1. Repairing Damaged Infrastructure

One of the most immediate concerns for Ukraine's energy sector is the extensive damage inflicted on its power infrastructure by Russian missile and drone attacks. Since the war began in 2022, Ukraine has faced repeated attacks targeting power plants, substations, and power lines, including strikes on western regions that caused widespread outages across communities. These attacks have left parts of the country with intermittent or no electricity, and repairing the damage has been a monumental task.

However, Ukraine has made significant progress in restoring its energy infrastructure. Government agencies and energy companies have been working around the clock to repair power plants and transmission networks. Teams of technicians and engineers have been deployed to restore power to areas that have been hardest hit by Russian attacks, often under difficult and dangerous conditions. While some areas may continue to face outages, efforts to rebuild the energy grid are ongoing, with the government prioritizing critical infrastructure to ensure that hospitals, military facilities, and essential services have access to power.

2. Energy Efficiency and Conservation Measures

To cope with reduced energy availability and avoid overloading the grid, Ukrainian authorities have been encouraging energy efficiency and conservation measures. These efforts are particularly important during the winter when demand for electricity and heating is at its peak.

The government has implemented energy-saving programs, urging citizens and businesses to reduce their consumption and adopt new energy solutions that can be deployed quickly. Measures include limiting electricity use during peak hours, setting thermostats lower in homes and businesses, and encouraging the use of energy-efficient appliances. Ukrainian officials have also been promoting public awareness campaigns to educate people about the importance of energy conservation, which is crucial to avoid grid overload and ensure the distribution of power across the country.

3. Importing Energy from Abroad

To supplement domestic energy production, Ukraine has been working to secure electricity imports from neighboring countries. Ukraine has long been interconnected with energy grids in countries such as Poland, Slovakia, and Hungary, which allows it to import electricity during times of shortage. In recent months, Ukraine has ramped up efforts to strengthen these connections, ensuring that it can import electricity when domestic production is insufficient to meet demand, and in a notable instance, helped Spain during blackouts through coordinated cross-border support.

While electricity imports from neighboring countries provide a temporary solution, this is not without its challenges. The cost of importing electricity can be high, and the country’s ability to import large amounts of power depends on the availability of energy in neighboring nations; officials say there are electricity reserves and no scheduled outages if strikes do not resume. Ukraine has been actively seeking new energy partnerships and working with international organizations to secure access to electricity, including exploring the potential for importing energy from the European Union.

4. Harnessing Renewable Energy Sources

Another key part of Ukraine's strategy to keep the lights on this winter is tapping into renewable energy sources, particularly wind and solar power. While Ukraine’s energy sector has historically been dependent on fossil fuels, the country has been making strides in integrating renewable energy into its grid. Solar and wind energy are particularly useful in supplementing the national grid, especially during the winter months when demand is high.

Renewable energy sources are less vulnerable to missile strikes compared to traditional power plants, making them an attractive option for Ukraine's energy strategy. Although renewable energy currently represents a smaller portion of Ukraine’s overall energy mix, its contribution is expected to increase as the country invests more in clean energy infrastructure. In addition to reducing dependence on fossil fuels, this shift is aligned with Ukraine’s broader environmental goals and will be important for the long-term sustainability of its energy sector.

5. International Aid and Support

International support has been crucial in helping Ukraine keep the lights on during the war. Western allies, including the European Union and the United States, have provided financial assistance, technical expertise, and equipment to help restore the energy infrastructure, though Washington recently ended some grid restoration support as priorities shifted. In addition to rebuilding power plants and transmission lines, Ukraine has received advanced energy technologies and materials to strengthen its energy security.

The U.S. has sent electrical transformers, backup generators, and other essential equipment to help Ukraine restore its energy grid. The European Union has also provided both financial and technical assistance, supporting Ukraine’s efforts to integrate more renewable energy into its grid and enhancing the country’s ability to import electricity from neighboring states.

6. The Role of Nuclear Energy

Ukraine’s nuclear energy plants play a critical role in the country’s electricity supply. Before the war, nuclear power accounted for around 50% of Ukraine’s total electricity generation, and for communities near the front line, electricity is civilization that depends on reliable baseload. Despite the ongoing conflict, Ukrainian nuclear plants have remained operational, though they face heightened security risks due to the proximity of active combat zones.

In the winter months, nuclear plants are expected to continue providing a significant portion of Ukraine's electricity, which is essential for meeting the country's heating and power needs. The government has made efforts to ensure the safety and security of these plants, which remain a vital part of the country's energy strategy.

Keeping the lights on in Ukraine during the winter of 2024 is no small feat, given the war-related damage to energy infrastructure, rising energy demands, and ongoing security risks. However, the Ukrainian government has taken proactive steps to address these challenges, including repairing critical infrastructure, importing energy from neighboring countries, promoting energy efficiency, and expanding renewable energy sources. International aid and the continued operation of nuclear plants also play a vital role in ensuring a reliable energy supply. While challenges remain, Ukraine’s resilience and determination to overcome its energy crisis are clear, and the country is doing everything it can to keep the lights on through this difficult winter.

 

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California’s Solar Power Cost Shift: A Misguided Policy Threatening Energy Equity

California Rooftop Solar Cost Shift examines PG&E rate hikes, net metering changes, and utility infrastructure spending impacts on low-income households, distributed generation, and clean energy adoption, potentially raising bills and undermining grid resilience.

 

Key Points

A claim that rooftop solar shifts fixed grid costs to others; critics cite PG&E rates, avoided costs, and impacts.

✅ PG&E rates outpace national average, underscoring cost drivers.

✅ Net metering cuts risk burdening low- and middle-income homes.

✅ Distributed generation avoids infrastructure spend and grid strain.

 

California is grappling with soaring electricity prices across the state, with Pacific Gas & Electric (PG&E) rates more than double the national average and increasing at an average of 12.5% annually over the past six years. In response, Governor Gavin Newsom issued an executive order directing state energy agencies to identify ways to reduce power costs. However, recent policy shifts targeting rooftop solar users may exacerbate the problem rather than alleviate it.

The "Cost Shift" Theory

A central justification for these pricing changes is the "cost shift" theory. This theory posits that homeowners with rooftop solar panels reduce their electricity consumption from the grid, thereby shifting the fixed costs of maintaining and operating the electrical grid onto non-solar customers. Proponents argue that this leads to higher rates for those without solar installations.

However, this theory is based on a flawed assumption: that PG&E owns 100% of the electricity generated by its customers and is entitled to full profits even for energy it does not deliver. In reality, rooftop solar users supply only about half of their energy needs and still pay for the rest. Moreover, their investments in solar infrastructure reduce grid strain and save ratepayers billions by avoiding costly infrastructure projects and reducing energy demand growth, aligning with efforts to revamp electricity rates to clean the grid as well.

Impact on Low- and Middle-Income Households

The majority of rooftop solar users are low- and middle-income households. These individuals often invest in solar panels to lower their energy bills and reduce their carbon footprint. Policy changes that undermine the financial viability of rooftop solar disproportionately affect these communities, and efforts to overturn income-based charges add uncertainty about affordability and access.

For instance, Assembly Bill 942 proposes to retroactively alter contracts for millions of solar consumers, cutting the compensation they receive from providing energy to the grid, raising questions about major changes to your electric bill that could follow if their home is sold or transferred. This would force those with solar leases—predominantly lower-income individuals—to buy out their contracts when selling their homes, potentially incurring significant financial burdens.

The Real Drivers of Rising Energy Costs

While rooftop solar users are being blamed for rising electricity rates, calls for action have mounted as the true culprits lie elsewhere. Unchecked utility infrastructure spending has been a significant factor in escalating costs. For example, PG&E's rates have increased rapidly, yet the utility's spending on infrastructure projects has often been criticized for inefficiency and lack of accountability. Instead of targeting solar users, policymakers should scrutinize utility profit motives and infrastructure investments to identify areas where costs can be reduced without sacrificing service quality.

California's approach to addressing rising electricity costs by targeting rooftop solar users is misguided. The "cost shift" theory is based on flawed assumptions and overlooks the substantial benefits that rooftop solar provides to the grid and ratepayers. To achieve a sustainable and equitable energy future, the state must focus on controlling utility spending, promoting clean energy access for all, especially as it exports its energy policies across the West, and ensuring that policies support—not undermine—the adoption of renewable energy technologies.

 

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TVA faces federal scrutiny over climate goals, electricity rates

TVA Rates and Renewable Energy Scrutiny spotlights electricity rates, distributed energy resources, solar and wind deployment, natural gas plans, grid access charges, energy efficiency cuts, and House oversight of lobbying, FERC inquiries, and least-cost planning.

 

Key Points

A congressional probe into TVA pricing and practices affecting renewables, energy efficiency, and climate goals.

✅ House panel probes TVA rates, DER and solar policies.

✅ Efficiency programs cut; least-cost planning questioned.

✅ Inquiry on lobbying, hidden fees; FERC scrutiny.

 

The Tennessee Valley Authority is facing federal scrutiny about its electricity rates and climate action, amid ongoing debates over network profits in other markets.

Members of the House Committee on Energy and Commerce are “requesting information” from TVA about its ratepayer bills and “out of concern” that TVA is interfering with the deployment of renewable and distributed energy resources, even as companies such as Tesla explore electricity retail to expand customer options.

“The Committee is concerned that TVA’s business practices are inconsistent with these statutory requirements to the disadvantage of TVA’s ratepayers and the environment,” the committee said in a letter to TVA CEO Jeffrey Lyash.

The four committee members — U.S. Reps. Frank Pallone, Jr. (D-NJ), Bobby L. Rush (D-IL), Diana DeGette (D-CO), and Paul Tonko (D-NY) — suggested that Tennessee Valley residents pay too much for electricity despite TVA’s relatively low rates, even as regulators have, in other cases, scrutinized mergers like the Hydro One-Avista deal to safeguard ratepayers, underscoring similar concerns. In 2020, Tennessee residents had electric bills higher than the national average, while low-income residents in Memphis have historically faced one of the highest energy burdens in the U.S.

In 2018, TVA reduced its wholesale rate while adding a grid access charge on local power companies—and interfered with the adoption of solar energy. Internal TVA documents obtained through a Freedom of Information Act request by the Energy and Policy Institute revealed that TVA permitted local power companies to impose new fees on distributed solar generation to “lessen the potential decrease in TVA load that may occur through the adoption of [behind the meter] generation.”

Additionally, the committee said TVA is not prioritizing energy conservation and efficiency or “least-cost planning” that includes renewables, as seen in oversight such as the OEB's Hydro One rates decision emphasizing cost allocation. TVA reduced its energy efficiency programs by nearly two-thirds between 2014 and 2018 and cut its energy efficiency customer incentive programs.

At this time, TVA has not aligned its long-term planning with the Biden administration’s goal to achieve a carbon-free electricity sector by 2035. TVA’s generation mix, which is roughly 60% carbon-free, comprises 39% nuclear, 19% coal, 26% natural gas, 11% hydro, 3% wind and solar, and 1% energy efficiency programs, according to TVA.

The committee is “greatly concerned that TVA has invested comparatively little to date in deploying solar and wind energy, while at the same time considering investments in new natural gas generation.”

TVA has announced plans to shutter the Kingston and Cumberland coal plants and is evaluating whether to replace this generation with natural gas, which is a fossil fuel, while debates over grid privatization raise questions about consumer benefits. TVA’s coal and natural gas plants represent most of the largest sources of greenhouses emissions in Tennessee.

TVA responded with a statement without directly addressing the committee’s concerns. TVA said its “developing and implementing emerging technologies to drive toward net-zero emissions by 2050.”

The final question that the House committee posed is whether TVA is funding any political activity. In 2019, the committee questioned TVA about its membership to the now-disbanded Utility Air Regulatory Group, a coalition that was involved in over 200 lawsuits that primarily fought Clear Air Act regulations.

TVA revealed that it had contributed $7.3 million to the industry lobbying group since 2001. Since TVA doesn’t have shareholders, customers paid for UARG membership fees, echoing findings that deferred utility costs burden customers in other jurisdictions. An Office of the Inspector General investigation couldn’t prove whether TVA’s contributions directly funded litigation because UARG didn’t have a line-by-line accounting of what they did with TVA’s dollars.

The congressional committee questioned whether TVA is still paying for lobbying or litigation that opposes “public health and welfare regulations.”

This last question follows a recent trend of questioning utilities about “hidden fees.” In December, the Federal Energy Regulatory Commission issued a Notice of Inquiry to examine how bills from investor-owned utilities might contain fees that fund political activity, and regulators have penalized firms like NT Power over customer notice practices, highlighting consumer protection. The Center for Biological Diversity filed a petition to protect electric and gas customers of investor-owned utilities from paying these fees, which may be used for lobbying, campaign-related donations and litigation.

 

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LNG powered with electricity could be boon for B.C.'s independent power producers

B.C. LNG Electrification embeds clean hydro and wind power into low-emission liquefied natural gas, cutting carbon intensity, enabling coal displacement in Asia, and opening grid-scale demand for independent power producers and ITMO-based climate accounting.

 

Key Points

Powering LNG with clean electricity cuts carbon intensity, displaces coal, and grows demand for B.C.'s clean power.

✅ Electric-drive LNG cuts emissions intensity by up to 80%.

✅ Creates major grid load, boosting B.C. independent power producers.

✅ Enables ITMO crediting when coal displacement is verified.

 

B.C. has abundant clean power – if only there was a way to ship those electrons across the sea to help coal-dependent countries reduce their emissions, and even regionally, Alberta–B.C. grid link benefits could help move surplus power domestically.

Natural gas that is liquefied using clean hydro and wind power and then exported would be, in a sense, a way of embedding B.C.’s low emission electricity in another form of energy, and, alongside the Canada–Germany clean energy pact, part of a broader export strategy.

Given the increased demand that could come from an LNG industry – especially one that moves towards greater electrification and, as the IEA net-zero electricity report notes, broader system demand – poses some potentially big opportunities for B.C.’s clean energy independent power sector, as those attending the Clean Energy Association of BC's annual at the Generate conference heard recently.

At a session on LNG electrification, delegates were told that LNG produced in B.C. with electricity could have some significant environmental benefits.

Given how much power an LNG plant that uses electric drive consumes, an electrified LNG industry could also pose some significant opportunities for independent power producers – a sector that had the wind taken out of its sails with the sanctioning of the Site C dam project.

Only one LNG plant being built in B.C. – Woodfibre LNG – will use electric drive to produce LNG, although the companies behind Kitimat LNG have changed their original design plans, and now plan to use electric drive drive as well.

Even small LNG plants that use electric drive require a lot of power.

“We’re talking about a lot of power, since it’s one of the biggest consumers you can connect to a grid,” said Sven Demmig, head of project development for Siemens.

Most LNG plants still burn natural gas to drive the liquefaction process – a choice that intersects with climate policy and electricity grids in Canada. They typically generate 0.35 tonnes of CO2e per tonne of LNG produced.

Because it will use electric drive, LNG produced by Woodfibre LNG will have an emissions intensity that is 80% less than LNG produced in the Gulf of Mexico, said Woodfibre president David Keane.

In B.C., the benchmark for GHG intensities for LNG plants has been set at 0.16 tonnes of CO2e per tonne of LNG. Above that, LNG producers would need to pay higher carbon taxes than those that are below the benchmark.

The LNG Canada plant has an intensity of 0.15 tonnes og CO2e per tonne of LNG. Woodfibre LNG will have an emissions intensity of just 0.059, thanks to electric drive.

“So we will be significantly less than any operating facility in the world,” Keane said.

Keane said Sinopec has recently estimated that it expects China’s demand for natural gas to grow by 82% by 2030.

“So China will, in fact, get its gas supply,” Keane said. “The question is: where will that supply come from?

“For every tonne of LNG that’s being produced today in the United States -- and tonne of LNG that we’re not producing in Canada -- we’re seeing about 10 million tonnes of carbon leakage every single year.”

The first Canadian company to produce LNG that ended up in China is FortisBC. Small independent operators have been buying LNG from FortisBC’s Tilbury Island plant and shipping to China in ISO containers on container ships.

David Bennett, director of communications for FortisBC, said those shipments are traced to industries in China that are, indeed, using LNG instead of coal power now.

“We know where those shipping containers are going,” he said. “They’re actually going to displace coal in factories in China.”

Verifying what the LNG is used for is important, if Canadian producers want to claim any kind of climate credit. LNG shipped to Japan or South Korea to displace nuclear power, for example, would actually result in a net increase in GHGs. But used to displace coal, the emissions reductions can be significant, since natural gas produces about half the CO2 that coal does.

The problem for LNG producers here is B.C.’s emissions reduction targets as they stand today. Even LNG produced with electricity will produce some GHGs. The fact that LNG that could dramatically reduce GHGs in other countries, if it displaces coal power, does not count in B.C.’s carbon accounting.

Under the Paris Agreement, countries agree to set their own reduction targets, and, for Canada, cleaning up Canada’s electricity remains critical to meeting climate pledges, but don’t typically get to claim any reductions that might result outside their own country.

Canada is exploring the use of Internationally Transferred Mitigation Outcomes (ITMO) under the Under the Paris Agreement to allow Canada to claim some of the GHG reductions that result in other countries, like China, through the export of Canadian LNG.

“For example, if I were producing 4 million tonnes of greenhouse gas emissions in B.C. and I was selling 100% of my LNG to China, and I can verify that they’re replacing coal…they would have a reduction of about 60 or million tonnes of greenhouse gas emissions,” Keane said.

“So if they’re buying 4 million tonnes of emissions from us, under these ITMOs, then they have net reduction of 56 million tonnes, we’d have a net increase of zero.”

But even if China and Canada agreed to such a trading arrangement, the United Nations still hasn’t decided just how the rules around ITMOs will work.

 

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Cheap material converts heat to electricity

Polycrystalline Tin Selenide Thermoelectrics enable waste heat recovery with ZT 3.1, matching single crystals while cutting costs, powering greener car engines, industrial furnaces, and thermoelectric generators via p-type and emerging n-type designs.

 

Key Points

Low-cost tin selenide devices that turn waste heat into power, achieving ZT 3.1 and enabling p-type and n-type modules.

✅ Oxygen removal prevents heat-leaking tin oxide grain skins.

✅ Polycrystalline ingots match single-crystal ZT 3.1 at lower cost.

✅ N-type tin selenide in development to pair with p-type.

 

So-called thermoelectric generators turn waste heat into electricity without producing greenhouse gas emissions, providing what seems like a free lunch. But despite helping power the Mars rovers, the high cost of these devices has prevented their widespread use. Now, researchers have found a way to make cheap thermoelectrics that work just as well as the pricey kind. The work could pave the way for a new generation of greener car engines, industrial furnaces, and other energy-generating devices.

“This looks like a very smart way to realize high performance,” says Li-Dong Zhao, a materials scientist at Beihang University who was not involved with the work. He notes there are still a few more steps to take before these materials can become high-performing thermoelectric generators. However, he says, “I think this will be used in the not too far future.”

Thermoelectrics are semiconductor devices placed on a hot surface, like a gas-powered car engine or on heat-generating electronics using thin-film converters to capture waste heat. That gives them a hot side and a cool side, away from the hot surface. They work by using the heat to push electrical charges from one to the other, a process of turning thermal energy into electricity that depends on the temperature gradient. If a device allows the hot side to warm up the cool side, the electricity stops flowing. A device’s success at preventing this, as well as its ability to conduct electrons, feeds into a score known as the figure of merit, or ZT.

 Over the past 2 decades, researchers have produced thermoelectric materials with increasing ZTs, while related advances such as nighttime solar cells have broadened thermal-to-electric concepts. The record came in 2014 when Mercouri Kanatzidis, a materials scientist at Northwestern University, and his colleagues came up with a single crystal of tin selenide with a ZT of 3.1. Yet the material was difficult to make and too fragile to work with. “For practical applications, it’s a non-starter,” Kanatzidis says.

So, his team decided to make its thermoelectrics from readily available tin and selenium powders, an approach that, once processed, makes grains of polycrystalline tin selenide instead of the single crystals. The polycrystalline grains are cheap and can be heated and compressed into ingots that are 3 to 5 centimeters long, which can be made into devices. The polycrystalline ingots are also more robust, and Kanatzidis expected the boundaries between the individual grains to slow the passage of heat. But when his team tested the polycrystalline materials, the thermal conductivity shot up, dropping their ZT scores as low as 1.2.

In 2016, the Northwestern team discovered the source of the problem: an ultrathin skin of tin oxide was forming around individual grains of polycrystalline tin selenide before they were pressed into ingots. And that skin acted as an express lane for the heat to travel from grain to grain through the material. So, in their current study, Kanatzidis and his colleagues came up with a way to use heat to drive any oxygen away from the powdery precursors, leaving pristine polycrystalline tin selenide, whereas other devices can generate electricity from thin air using ambient moisture.

The result, which they report today in Nature Materials, was not only a thermal conductivity below that of single-crystal tin selenide but also a ZT of 3.1, a development that echoes nighttime renewable devices showing electricity from cold conditions. “This opens the door for new devices to be built from polycrystalline tin selenide pellets and their applications to be explored,” Kanatzidis says.

Getting through that door will still take some time. The polycrystalline tin selenide the team makes is spiked with sodium atoms, creating what is known as a “p-type” material that conducts positive charges. To make working devices, researchers also need an “n-type” version to conduct negative charges.

Zhao’s team recently reported making an n-type single-crystal tin selenide by spiking it with bromine atoms. And Kanatzidis says his team is now working on making an n-type polycrystalline version. Once n-type and p-type tin selenide devices are paired, researchers should have a clear path to making a new generation of ultra-efficient thermoelectric generators. Those could be installed everywhere from automobile exhaust pipes to water heaters and industrial furnaces to scavenge energy from some of the 65% of fossil fuel energy that winds up as waste heat. 

 

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