Investing in coal plants carries real risk

By The Bond Buyer


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Andrew Ackerman's January 13 article "Climate Disclosure Sought" accurately reflects the current state of public debate on disclosure of financial risk to investors in tax-exempt bonds that support new and existing coal-fired electric generation plants. It is a debate fraught with paradox and risk.

Federal energy experts, the Rural Utility Service, have stopped allowing federal tax dollars to be invested in these coal plants because they are risky investments. In large measure this is due to impending costs imposed due to new carbon regulations.

Federal finance experts at the Treasury Department have ignored this energy expertise and issued no guidance to bond investors, as if the risk to a federal tax dollar were somehow different than a bondholder's dollar.

Our credit rating agencies seem equally confused. In your article a representative of Moody's defends a recent bond disclosure for a new coal plant because the offering document contains some discussion of carbon risk. The disclosure he defends ignores the same worrisome set of credit risks that Moody's warned about in February 2008 in a special report on climate risk.

Developers of coal plants and utilities face not only the risk of new carbon regulations and the costs from them, but they also face compliance costs with regard to sulfur dioxide, mercury and other air pollution requirements.

The recent ash spill in Tennessee has added future regulation of ash disposal onto the list of new costs. The volatility of future coal costs have been raised as a matter of concern by federal agencies as well.

Moody's and Standard & Poor's have raised the issue of "cumulative risk" in their reports. Future carbon regulation alone creates a significant financial risk to coal as a future resource for electricity generation. However, as a pure financial play it is the combination of regulatory burdens and shifting market realities related to coal generation that requires a full explanation for investors.

The recent changes in the nation's fortunes related to its natural gas supply have placed the rising cost of coal into stark relief against its competition: wind, solar, natural gas and energy efficiency. Progress Energy's recent decision to close much of its existing coal fleet rests on its own cost-benefit analysis of these risks.

Comprehensive disclosure of information to bond investors is essential to smooth market functioning. This needs to include untidy facts like the federal government pulling out of financing coal plants, as well as disclosure of the cumulative costs from factoring the real cost of coal into the price of electricity, even if it shows that coal-plant investments are no longer competitive.

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Texas Utilities back out of deal to create smart home electricity networks

Smart Meter Texas real-time pricing faces rollback as utilities limit on-demand reads, impacting demand response, home area networks, ERCOT wholesale tracking, and thermostat automation, reducing efficiency gains promised through deregulation and smart meter investments.

 

Key Points

A plan linking smart meters to ERCOT prices, enabling near real-time usage alignment and automated demand response.

✅ Twice-hourly reads miss 15-minute ERCOT price spikes.

✅ Less than 1% of 7.3M meters use HAN real-time features.

✅ Limits hinder automation for HVAC, EV charging, and pool pumps.

 

Utilities made a promise several years ago when they built Smart Meter Texas that they’d come up with a way for consumers to monitor their electricity use in real time. But now they’re backing out of the deal with the approval of state regulators, leaving in the lurch retail power companies that are building their business model on the promise of real time pricing and denying consumers another option for managing their electricity costs.

Texas utilities collected higher rates to finance the building of a statewide smart meter network that would allow customers to track their electricity use and the quickly changing prices on wholesale power markets almost as they happened. Some retailers are building electricity plans around this promise, providing customers with in-home devices that would eventually track pricing minute-by-minute and allow them to automatically turn down or shut off air conditioners, pool pumps and energy sucking appliances when prices spiked on hot summer afternoons and turn them back on when they prices fell again.

The idea is to help save consumers money by allowing them to shift their electricity consumption to periods when power is cheaper, typically nights and weekends, even as utility revenue in a free-power era remains a debated topic.

“We’re throwing away a large part of (what) ratepayers paid for,” said John Werner, CEO of GridPlus Texas, one of the companies offering consumers a real-time pricing plan that is scheduled to begin testing next month. “They made the smart meters dumb meters.”

When Smart Meter Texas was launched a decade ago by a consortium of the state’s biggest utilities, it was considered an important part of deregulation. The competitive market for electricity held the promise that consumers would eventually have the technology to control their electricity use through a home area network and cut their power bills.

Regulators and legislators also were enticed by the possibility of making the electric system more efficient and relieving pressure on the power grid as consumers responded to high prices and cut consumption when temperatures soared, with ongoing discussions about Texas grid reliability informing policy choices.

One study found that smart meters coupled with smart real time consumption monitors could reduce electricity use between 3 percent and 5 percent, according to Call Me Power, a website sponsored by the European electricity price shopping service Selectra.

But utilities complained that the home area network devices were expensive to install and not used very often, and, with flat electricity demand weighing on growth, they questioned further investment. CenterPoint manager Esther Floyd Kent filed an affidavit with the commission in May that it costs the utility about $30,000 annually to support the network devices, plus maintenance.

Over a six-year period, CenterPoint paid $124,500, or about $20,000 a year, to maintain the system. As of April, there were only 4,067 network devices in CenterPoint’s service area, meaning the utility pays about $30.70 each year to maintain each device.

Centerpoint last year generated $9.6 billion in revenues and earned a $1.8 billion profit, according to its financial filings. CenterPoint officials did not respond to requests for comment.

Other utilities that are part of the Smart Meter consortium also complained to the Public Utility Commission that, up to now, the system hasn’t developed. All told, Texas has 7.3 million meters connected to Smart Meter Texas, but less than 1 percent are using the networking functions to track real-time prices and consumption, according to the testimony of Donny R. Helm, director of technology strategy and architecture for the state’s largest utility Oncor Electric Delivery Co. in Dallas.

The isssue was resolved recently through a settlement agreement that limits on-demand readings to twice an hour that Smart Meter Texas must provide customers. The price of power changes every 15 minutes, so a twice an hour reading may miss some price spikes.

The Public Utility Commission signed off on the deal, and so did several other groups including several retail electricity providers and the Office of Public Utility Counsel which represents residential customers and small businesses.

Michele Gregg, spokeswoman for the Public Utility Counsel, testified in December that the consumer advocate supported the change because widespread use of the networks never materialized. Catherine Webking, an Austin lawyer who represents the Texas Energy Association for Marketers, a group of retail electric providers, said she believes the deal was a reasonable resolution of providing the benefits of Smart Meter Texas while not incurring too much cost.

But Griddy, an electricity provider that offers customers the opportunity to pay wholesale power prices, which also issued a plea to customers during a price surge, said the state hasn’t given the smart-meter networks a chance and could miss out on its potential. Griddy was counting on the continued adoption of real time pricing as the next step for customers wanting to control their electricity costs.

Right now, Griddy sends out price alerts from the grid operator Electric Reliability Council of Texas so businesses like hotels can run washers and dryers when electricity prices are cheapest. But the company was counting on a smart-meter program that would allow customers to track wholesale prices and manage consumption themselves, making Griddy’s offerings attractive to more people.

Wholesale prices are generally cheaper than retail prices, but they can fluctuate widely, especially when the Texas power grid faces another crisis during extreme weather. Last year, wholesale prices averaged less than 3 cents per kilowatt hour, much lower than than retail rates that now are running above 11 cents, but they can spike at times of high demand to as much as $9 a kilowatt hour.

What customers want is to be able to use energy when it’s cheapest, said Greg Craig, Griddy’s CEO, and they want to do it automatically. They want to be able to program their thermostat so that if the price rises they can shut off their air conditioning and if the price falls, they can charge their electric-powered vehicle.

Griddy customers may still save money even without real time data, he said. But they won’t be able to see their usage in real time or see how much they’re spending.

“The big utilities have big investments in the existing way and going to real time and more transparency isn’t really in their best interest,” said Craig.

 

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Ontario's electricity operator kept quiet about phantom demand that cost customers millions

IESO Fictitious Demand Error inflated HOEP in the Ontario electricity market, after embedded generation was mis-modeled; the OEB says double-counted load lifted wholesale prices and shifted costs via the Global Adjustment.

 

Key Points

An IESO modeling flaw that double-counted load, inflating HOEP and charges in Ontario's wholesale market.

✅ Double-counted unmetered load from embedded generation

✅ Inflated HOEP; shifted costs via Global Adjustment

✅ OEB flagged transparency; exporters paid more

 

For almost a year, the operator of Ontario’s electricity system erroneously counted enough phantom demand to power a small city, causing prices to spike and hundreds of millions of dollars in extra charges to consumers, according to the provincial energy regulator.

The Independent Electricity System Operator (IESO) also failed to tell anyone about the error once it noticed and fixed it.

The error likely added between $450 million and $560 million to hourly rates and other charges before it was fixed in April 2017, according to a report released this month by the Ontario Energy Board’s Market Surveillance Panel.

It did this by adding as much as 220 MW of “fictitious demand” to the market starting in May 2016, when the IESO started paying consumers who reduced their demand for power during peak periods. This involved the integration of small-scale embedded generation (largely made up of solar) into its wholesale model for the first time.

The mistake assumed maximum consumption at such sites without meters, and double-counted that consumption.

The OEB said the mistake particularly hurt exporters and some end-users, who did not benefit from a related reduction of a global adjustment rate applicable to other customers.

“The most direct impact of the increase in HOEP (Hourly Ontario Energy Price) was felt by Ontario consumers and exporters of electricity, who paid an artificially high HOEP, to the benefit of generators and importers,” the OEB said.

The mix-up did not result in an equivalent increase in total system costs, because changes to the HOEP are offset by inverse changes to a electricity cost allocation mechanism such as the Global Adjustment rate, the OEB noted.


A chart from the OEB's report shows the time of day when fictitious demand was added to the system, and its influence on hourly rates.

Peak time spikes
The OEB said that the fictitious demand “regularly inflated” the hourly price of energy and other costs calculated as a direct function of it.

For almost a year, Ontario's electricity system operator @IESO_Tweets erroneously counted enough phantom demand to power a small city, causing price spikes and hundreds of millions in charges to consumers, @OntEnergyBoard says. @5thEstate reports.

It estimated the average increase to the HOEP was as much as $4.50/MWh, but that price spikes, compounded by scheduled OEB rate changes, would have been much higher during busier times, such as the mid-morning and early evening.

“In times of tight supply, the addition of fictitious demand often had a dramatic inflationary impact on the HOEP,” the report said.

That meant on one summer evening in 2016 the hourly rate jumped to $1,619/MWh, it said, which was the fourth highest in the history of the Ontario wholesale electricity market.

“Additional demand is met by scheduling increasingly expensive supply, thus increasing the market price. In instances where supply is tight and the supply stack is steep, small increases in demand can cause significant increases in the market price.

The OEB questioned why, as of September this year, the IESO had failed to notify its customers or the broader public, amid a broader auditor-regulator dispute that drew political attention, about the mistake and its effect on prices.

“It's time for greater transparency on where electricity costs are really coming from,” said Sarah Buchanan, clean energy program manager at Environmental Defence.

“Ontario will be making big decisions in the coming years about whether to keep our electricity grid clean, or burn more fossil fuels to keep the lights on,” she added. “These decisions need to be informed by the best possible evidence, and that can't happen if critical information is hidden.”

In a response to the OEB report on Monday, the IESO said its own initial analysis found that the error likely pushed wholesale electricity payments up by $225 million. That calculation assumed that the higher prices would have changed consumer behaviour, while upcoming electricity auctions were cited as a way to lower costs, it said.

In response to questions, a spokesperson said residential and small commercial consumers would have saved $11 million in electricity costs over the 11-month period, even as a typical bill increase loomed province-wide, while larger consumers would have paid an extra $14 million.

That is because residential and small commercial customers pay some costs via time-of-use rates, including a temporary recovery rate framework, the IESO said, while larger customers pay them in a way that reflects their share of overall electricity use during the five highest demand hours of the year.

The IESO said it could not compensate those that had paid too much, given the complexity of the system, and that the modelling error did not have a significant impact on ratepayers.

While acknowledging the effects of the mistake would vary among its customers, the IESO said the net market impact was less than $10 million, amid ongoing legislation to lower electricity rates in Ontario.

It said it would improve testing of its processes prior to deployment and agreed to publicly disclose errors that significantly affect the wholesale market in the future.

 

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Alberta gives $40M to help workers transition from coal power jobs

Alberta Coal Transition Support offers EI top-ups, 75% wage replacement, retraining, tuition vouchers, and on-site advice for workers leaving thermal coal mines and coal-fired power plants during the provincial phase-out.

 

Key Points

Alberta Coal Transition Support is a $40M program providing EI top-ups, retraining, and tuition vouchers to coal workers.

✅ 75% EI top-up; province requests federal alignment

✅ Tuition vouchers and retraining for displaced workers

✅ On-site transition services; about 2,000 workers affected

 

Alberta is putting aside $40 million to help workers losing their jobs as the province transitions away from thermal coal mines and coal-fired power plants, a shift connected to the future of work in the electricity sector over the next decade.

Labour Minister Christina Gray says the money will top up benefits to 75 per cent of a worker’s previous earnings during the time they collect employment insurance, amid regional shifts such as how COVID-19 reshaped Saskatchewan in recent months.

Alberta is asking the federal government to not claw back existing benefits as the province tops up those EI benefits, as utilities face pressures like Manitoba Hydro cost-cutting during the pandemic, while also extending EI benefits for retiring coal workers.

Gray says even if the federal government does not step up, the province will provide the funds to match that 75 per cent threshold, a contrast to problems such as Kentucky miners' cold checks seen elsewhere.

There will also be help for workers in the form of tuition vouchers, retraining programs like the Nova Scotia energy training program that connects youth to the sector, and on-site transitioning advice.

The province estimates there are 2,000 workers affected.

 

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Trump Tariff Threat Delays Quebec's Green Energy Bill

Quebec Energy Bill Tariff Delay disrupts Canada-U.S. trade, renewable energy investment, hydroelectric expansion, and clean technology projects, as Trump tariffs on aluminum and steel raise costs, threatening climate targets and green infrastructure timelines.

 

Key Points

A policy pause in Quebec from U.S. tariff threats, disrupting clean investment, hydro expansion, and climate targets.

✅ Tariff risk inflates aluminum and steel project costs.

✅ Quebec delays clean energy legislation amid trade uncertainty.

✅ Hydroelectric reliance complicates emissions reduction timelines.

 

The Trump administration's tariff threat has had a significant impact on Quebec's energy sector, with tariff threats boosting support for projects even as the uncertainty resulted in the delay of a critical energy bill. Originally introduced to streamline energy development and tackle climate change, the bill was meant to help transition Quebec towards greener alternatives while fostering economic growth. However, the U.S. threat to impose tariffs on Canadian goods, including energy products, introduced a wave of uncertainty that led to a pause in the bill's legislative process.

Quebec’s energy bill had ambitious goals of transitioning to renewable sources like wind, solar, and hydroelectric power. It sought to support investments in clean technologies and the expansion of the province's clean energy infrastructure, as the U.S. demand for Canadian green power continues to grow across the border. Moreover, it emphasized the reduction of carbon emissions, an important step towards meeting Quebec's climate targets. At its core, the bill aimed to position the province as a leader in green energy development in Canada and globally.

The interruption caused by President Donald Trump's tariff rhetoric has, however, cast a shadow over the legislation. Tariffs, if enacted, would disproportionately affect Canada's energy exports, with electricity exports at risk under growing tensions, particularly in sectors like aluminum and steel, which are integral to energy infrastructure development. These tariffs could increase the cost of energy-related projects, thereby hindering Quebec's ability to achieve its renewable energy goals and reduce carbon emissions in a timely manner.

The tariff threat was seen as a part of the broader trade tensions between the U.S. and Canada, a continuation of the trade war that had escalated under Trump’s presidency. In this context, the Quebec government was forced to reconsider its legislative priorities, with policymakers citing concerns over the potential long-term consequences on the energy industry, as leaders elsewhere threatened to cut U.S.-bound electricity to exert leverage. With the uncertainty around tariffs and trade relations, the government opted to delay the bill until the geopolitical situation stabilized.

This delay underscores the vulnerability of Quebec’s energy agenda to external pressures. While the provincial government had set its sights on an ambitious green energy future, it now faces significant challenges in ensuring that its projects remain economically viable under the cloud of potential tariffs, even as experts warn against curbing Quebec's exports during the dispute. The delay in the energy bill also reflects broader challenges faced by the Canadian energy sector, which is highly integrated with the U.S. market.

The situation is further complicated by the province's reliance on hydroelectric power, a cornerstone of its energy strategy that supplies markets like New York, where tariffs could spike New York energy prices if cross-border flows are disrupted. While hydroelectric power is a clean and renewable source of energy, there are concerns about the environmental impact of large-scale dams, and these concerns have been growing in recent years. The tariff threat may prompt a reevaluation of Quebec’s energy mix and force the government to balance its environmental goals with economic realities.

The potential imposition of tariffs also raises questions about the future of North American energy cooperation. Historically, Canada and the U.S. have enjoyed a symbiotic energy relationship, with significant energy trade flowing across the border. The energy bill in Quebec was designed with the understanding that cross-border energy trade would continue to thrive. The Trump administration's tariff threat, however, casts doubt on this stability, forcing Quebec lawmakers to reconsider how they proceed with energy policy in a more uncertain trade environment.

Looking forward, Quebec's energy sector will likely need to adjust its strategies to account for the possibility of tariffs, while still pushing for a sustainable energy future, especially if Biden outlook for Canada's energy proves more favorable for the sector in the medium term. It may also open the door for deeper discussions about diversification, both in terms of energy sources and trade partnerships, as Quebec seeks to mitigate the impact of external threats. The delay in the energy bill, though unfortunate, may serve as a wake-up call for Canadian lawmakers to rethink how they balance environmental goals with global trade realities.

Ultimately, the Trump tariff threat highlights the delicate balance between regional energy ambitions and international trade dynamics. For Quebec, the delay in the energy bill could prove to be a pivotal moment in shaping the future of its energy policy.

 

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Saudis set to 'boost wind by over 6GW'

Saudi Arabia Wind Power Market set to lead the Middle East, driven by Vision 2030 renewables goals, REPDO tenders, and PIF backing, adding 6.2GW wind capacity by 2028 alongside solar PV diversification.

 

Key Points

It is the emerging national segment leading Middle East wind growth, targeting 6.2GW by 2028 under Vision 2030 policies.

✅ Adds 6.2GW, 46% of regional wind capacity by 2028

✅ REPDO tenders and PIF funding underpin pipeline

✅ Targets: 16GW wind, 40GW solar under Vision 2030

 

Saudi Arabia will become a regional heavyweight in the Middle East's wind power market adding over 6GW in the next 10 years, according to new research by Wood Mackenzie Power & Renewables.

The report – 'Middle East Wind Power Market Outlook, 2019-2028’ – said developers will build 6.2GW of wind capacity in the country or 46% of the region’s total wind capacity additions between 2019 and 2028.

Wood Mackenzie Power & Renewables senior analyst Sohaib Malik said: “The integration of renewables in Vision 2030’s objectives underlines strong political commitment within Saudi Arabia.

“The level of Saudi ambition for wind and solar PV varies significantly, despite the cost parity between both technologies during the first round of tenders in 2018.”

Saudi Arabia has set a 16GW target for wind by 2030 and 40GW for solar, plans to solicit 60 GW of clean energy over the next decade, Wood Mackenzie added.

“Moving forward, the Renewable Energy Project Development Office will award 850MW of wind capacity in 2019, which is expected to be commissioned in 2021-2022, and increase the local content requirement in future tendering rounds,” Malik said.

However, Saudi Arabia will fall short of its current 2030 renewables target, despite growth projections and regional leadership, the report said.

Some 70% of the renewables capacity target is to be supported by the Public Investment Fund (PIF), the Saudi sovereign wealth fund, while the remaining capacity is to be awarded through REPDO.

“A central concern is the PIF’s lack of track record in the renewables sector and its limited in-house sectoral expertise,” said Malik

“REPDO, on the other hand, completed two renewables request for proposals after pre-developing the sites,” he said.

PIF is estimated to have $230bn of assets – targeted to reach $2 trillion under Vision 2030 – driven by investments in a variety of sectors ranging from electric vehicles to public infrastructure, Wood Mackenzie said.

“There is little doubt about the fund’s financial muscle, however, its past investment strategy focused on established firms in traditional industries,” Malik added.

“Aspirations to develop a value chain for wind and PV technologies locally is a different ball game and requires the PIF to acquire new capabilities for effective oversight of these ventures,” he said.

The report noted that regional volatility is expected to remain, with strong positive growth, driven by Jordan and Iran in 2018 expected to reverse in 2019, and policy shifts, as in Canada’s scaled-back projections, can influence outcomes.

Post-2020 Wood Mackenzie Power & Renewables sees regional demand returning to steady growth as global renewables set more records elsewhere.

“In 2018, developers added 185MW and 63MW of wind capacity in Jordan and Iran, respectively, compared to 53MW of capacity across the entire region in 2017, following a record year for renewables in 2016,” said Malik.

“The completion of the 89MW Al Fujeij and the 86MW Al Rajef projects in 2018 indicates that Jordan has 375MW of the region’s operational 675MW wind capacity.

“Iran followed with 278MW of installed capacity at the end of 2018. A slowdown in 2019 is expected, as project development activity softens in Iran.

“Additionally, delays in awarding the 400MW Dumat Al Jandal project in Saudi Arabia will limit annual capacity additions to 184MW.”

He added that a maturing project pipeline in the region supports the 2020-2021 outlook, even as wind power grew despite Covid-19 globally.

“Saudi Arabian demand serves as the foundation for regional demand. Regional demand diversification is also occurring, with Lebanon set to add 200-400MW to its existing permitted capacity pipeline of 202MW in 2019,” he said

“These developments pave the way for the addition of 2GW of wind capacity between 2019 and 2021.”

Wood Mackenzie Power & Renewables added that the outlook for solar in the region is “much more positive” than wind.

“Compared to only 6GW of wind power capacity, developers will add 53GW of PV capacity through 2024,” said Malik.

He added: “Solar PV, supported by trends such as China’s rapid PV growth in 2016, has become a natural choice for many countries in the region, which is endowed with world class solar energy resources.

“The increased focus on solar energy is demonstrated by ambitious PV targets across the region.”

 

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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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