OSU student exercise to generate power

By Associated Press


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Thousands of college students regularly hit the cardio exercise machines to work off stress after an exam or stay in shape. Oregon State University is harnessing the energy the machines can generate and converting it to electricity to feed back into the power grid.

It is among the first universities in the United States to do so.

With new technology developed by a Florida firm, OSU has retrofitted 22 elliptical exercise machines in its student fee-funded Dixon Recreation Center and already is collecting the power produced by students.

The effort will produce an estimated 3,500 kilowatt hours of electricity in a year, according to Brandon Trelstad, the universityÂ’s sustainability coordinator.

Its output could be equivalent to what is needed to power a small, very efficient house, Trelstad said. "Our ultimate goal is to maximize both the real power output of the system and the learning opportunities gained by having it at OSU."

In 2007, OSU students voted to tax themselves $8.50 per student per term to purchase renewable energy for the campus. Since then, about three-quarters of the universityÂ’s electricity has come from renewable production.

"OSU students have demonstrated how big student power can be on campus," said Matthew Pennington, chief of staff for the Associated Students of Oregon State University. "It was a grass roots movement that helped OSU turn green and this project moves it forward even farther."

The ReRev technology features a system with a pending patent called ReCardio that captures and converts the otherwise-counterproductive heat energy from exercise machines.

Though some businesses or individuals have dabbled with this type of energy conversion, a program on this scale is unusual, Trelstad said.

"A battery-free system like this, tied to the grid, is quite rare," Trelstad said. "In fact, weÂ’re informed by ReRev which has done extensive market research that this is the largest installation of its kind in the world."

"Capturing electricity from exercise machines represents a small, but potentially widely replicable source of energy," said Jan Schaeffer, special projects manager for Energy Trust.

While students pedal, a real-time display screen shows momentary power production, production to date, production peaks and other data.

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The crisis in numbers: How COVID-19 has reshaped Saskatchewan

Saskatchewan COVID-19 economic impact: real-time data shows drops in electricity demand, oil well licensing, traffic and tickets, plus spikes in internet usage, government site visits, remote work, and alcohol wholesale volumes.

 

Key Points

COVID-19 reduced energy use, drilling and traffic, while pushing activity online; jobs, rents and sales show strain.

✅ Electricity demand down 6.7%; residential usage up

✅ Oil well license applications fell 15-fold in April

✅ Internet traffic up 16%-46%; wireless LTE up 34%

 

We’re only just beginning to grasp how COVID-19 has upended Saskatchewan’s economy, its government and all of our lives.

The numbers that usually make headlines — job losses, economic contraction, bankruptcies — are still well behind the pace of the virus and its toll.

But other numbers change more quickly. Saskatchewan people are using less power, and the power industry is adopting on-site staffing plans to ensure reliability as conditions evolve. We’re racking up fewer speeding tickets. And as new restrictions come, we’re clicking onto Saskatchewan.ca as much as 10,000 times per minute.

Here’s some data that provides a first glimpse into how much our province has changed in just six weeks.

Electricity use tends to rise and fall in tandem with the health of the economy, and the most recent data from SaskPower suggests businesses are powering down, while regional utilities such as Manitoba Hydro seek unpaid days off to trim costs.

Peak load requirements between March 15 and April 26 were 220 MW lower than during the same period in 2019, and elsewhere BC Hydro is posting COVID-19 updates at Site C as it manages project impacts. That’s a decrease of 6.7 per cent, with total load on April 29 at 2,551 MW. A megawatt is enough electricity to power about 1,000 homes.

Separate from pandemic impacts, an external investigation at Manitoba Hydro has drawn attention to workplace conduct issues.

But it’s not homes that are turning off the lights. SaskPower spokesman Joel Cherry said commercial and industrial usage is down, while residential demand is up, with household electricity bills rising as more people stay home.

The timing of power demand has also shifted, a pattern seen as residential electricity use rises during work-from-home routines. Peak load would usually come around 8 or 9 p.m. in April. Now it’s coming earlier, typically between 5 and 6 p.m.

Oil well applications fall 15-fold
Oil prices have cratered since late February, and producers in Saskatchewan have reacted by pulling back on drilling plans, while neighbouring Alberta provides transition support for coal workers amid broader energy shifts.

Applications for well licences fell from 242 in January to 203 in February (including nine potash and one helium operations), before dropping to 84 in March. April, the month benchmark oil prices went negative for one day, producers submitted just 15 applications.

That’s 15 times fewer than the 231 applications the Ministry of Energy and Resources received in April 2019.

Well licences are needed for drilling, operating, injecting, producing or exploring an oil and gas or potash well in the province.

There has been no clear trend in well abandonment, however. There were 176 applications for abandonment in March and 155 in April, roughly in line with figures from the year before.

SGI spokesman Tyler McMurchy believes the lower numbers might stem from a combination of lower traffic volumes during part of the month, possibly combined with a shift in police priorities. The March 2020 numbers are also well below January and February figures.

Indeed, the Ministry of Highways and infrastructure reported a 16 per cent decrease in average daily traffic last month compared to March 2019, through its traffic counts at 11 different spots on highways across the province.

In Regina, traffic counts at 16 locations dropped from a high of 2.1 million in the first week of March to a low of 1.3 million during the week of March 22. That’s a 44 per cent decrease.

Counts have gradually recovered to 1.6 million in the weeks since. The data was fairly consistent at all 16 spots, which are largely major intersections, though the city cautioned they may not be representative of Regina as a whole.

Tickets for cellphone use while driving also fell, dropping from 562 in February to 314 in March. McMurchy noted that distracted driving numbers in general have been falling since November as stiffer penalties were announced. Impaired driving tickets were up, by contrast, but still within a typical range.

Internet traffic shoots up 16 per cent, far more for rural high speed
You may be spending a lot more time on Netflix and Facebook in the age of social distancing, and SaskTel has noticed.

From late February to late April, SaskTel has seen “very significant increases in provincial data traffic.” DSL and fibre optic networks have handled a 16 per cent increase in traffic, while demand on the wireless LTE network is up 34 per cent.

Usage on the Fusion network up 46 per cent. That network serves rural areas that don’t have access to other high-speed options.

The specific reference dates for comparison were February 24 and April 27.

“We attribute these changes in data usage to the pandemic and not expected seasonal or yearly shifts in usage patterns,” said spokesman Greg Jacobs.

Saskatchewan.ca was attracting just 70 page views per minute on average in February. But page views jumped over 10,000 per minute at 2:38 p.m. on March 18, as Moe was still announcing the new measures.

That’s a 14,000 per cent increase.

For all of March, visitor sessions on the site clocked in at 3,905,061, almost four times the 944,904 recorded for February.

Bureaucracy has increasingly migrated to cyberspace, with 62 per cent of civil servants now working from home. Government Skype calls, both audio and video, have tripled from 12,000 sessions per day to 35,000.Telephone conference calls increased by a factor of 14 from the first week of February to the second full week of April, with 25 times more weekly call participants. 

The Ministry of Central Services reported a 17 per cent jump in emails received by government over the past two months, excluding the Ministry of Health.

But as civil servants spend more time on their computers, the government’s fleet is spending a lot less time on the road. The ministry has purchased 40 per cent fewer litres of fuel for its vehicles over the past four weeks, compared to the same time last year.

Alcohol wholesale volumes up 22 per cent, then fall back to normal
Retailers bought more alcohol from the Saskatchewan Liquor and Gaming Authority (SLGA) last month, just as the government began tightening pandemic restrictions.

Wholesale sales volumes were up 22 per cent over March 15 to 28, compared to the same period in 2019. SLGA spokesman David Morris said the additional demand “was likely the result of retailers stocking-up as restrictions related to COVID-19 took effect.”

But the jump didn’t last. Wholesale volumes were back to normal for the first two weeks of April. SLGA did notice a very slight uptick last week, however, with volumes out of its distribution centre up three per cent. The numbers do not include Brewer’s Distributors Ltd.

It’s unclear how much more alcohol consumers actually purchased, since province-wide retail numbers were not available.

There was no discernible trend in March for anti-anxiety medication, however. The number of prescriptions filled for benzodiazepines like Valium, Xanax and Ativan see-sawed over March, according to data provided by the College of Physicians and Surgeons, but its associate registrar does not believe the trends are statistically relevant.

One-fifth of tenants miss April rent
About 20 per cent of residential rent went totally unpaid in the first six days of April, according to the Saskatchewan Landlord Association (SLA).

The precise number is 19.7 per cent, but there’s some uncertainty due to the survey method, which is based on responses from 300 residential landlords with 14,000 units. An additional 12 per cent of tenants paid a portion of their rent, but not the full amount. The figures do not include social housing.

Cameron Choquette, the association’s executive officer, partly blames the province’s decision to suspend most landlord tenant board hearings for evictions, saying it “allows more people to take advantage of landlords by not paying their rent and not facing any consequences.”

The government has defended the suspension by saying it’s needed to ensure everyone has a safe place to self-isolate if needed during the pandemic.

March’s jobs numbers were bad, with almost 21,000 fewer Saskatchewan people employed compared to February.

April’s labour force survey is expected on Friday. But new April numbers released Wednesday show that two-thirds of the province’s businesses managed to avoid laying off staff almost entirely.

According to Statistics Canada, 66.2 per cent of businesses reported laying off between zero and one per cent of their employees due to COVID-19. That was better than any other province. Just 7.6 per cent laid off all of their employees, again the best number outside the territories. The survey period was April 3 to 24.

Some businesses are even hiring. Walmart, for instance, has hired 300 people in Saskatchewan since mid-March.

Trade and Export Development Minister Jeremy Harrison chalked the data up to a relatively more optimistic business outlook in Saskatchewan, combined with “very targeted” restrictions and a support program for small and medium businesses.

That support program, which provides $5,000 grants to qualifying businesses affected by government restrictions, has only been around for three weeks. But it’s already been bombarded with 6,317 applications.

The total value of those applications would be $24,178,000, according to Harrison. Of them, 3,586 have been approved with a value of $11,755,000.

Businesses are coming to Harrison’s ministry with thousands of questions. Since it opened in March, the Business Response Team has received 4,125 calls and 1,758 emails.

The kinds of questions have changed over the course of the pandemic. Many are now asking when they can open their doors, according to Harrison, as they wonder about “grey areas” in the Re-Open Saskatchewan plan.

 

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Worker injured after GE turbine collapse

GE Wind Turbine Collapse Brazil raises safety concerns at Omega Energia's Delta VI wind farm in Maranhe3o, with GE Renewable Energy probing root-cause of turbine failure after a worker injury and similar incidents in 2024.

 

Key Points

An SEO focus on the Brazil GE turbine collapse, its causes, safety investigation, and related 2024 incidents.

✅ Incident at Omega Energia's Delta VI, Maranhao; one worker injured

✅ GE Renewable Energy conducts root-cause investigation and containment

✅ Fifth GE turbine collapse in 2024 across Brazil and the United States

 

A GE Renewable Energy turbine collapsed at a wind farm in north-east Brazil, injuring a worker and sparking a probe into the fifth such incident this year, the manufacturer confirmed.

One of the manufacturer’s GE 2.72-116 turbines collapsed at Omega Energia’s Delta VI project in Maranhão, which was commissioned in 2018.

Three GE employees were on site at the time of the collapse on Tuesday (3 September), the US manufacturer confirmed, even as U.S. offshore wind developers signal growing competitiveness with gas. 

One worker was injured and is currently receiving medical treatment, GE added.

"We are working to determine the root cause of this incident and to provide proper support as needed," it said

The turbine collapse in Brazil is the fifth such incident involving GE turbines this year, even as the UK's biggest offshore windfarm begins power supply this week, underscoring broader sector momentum.

On 16 February, a turbine collapsed at NextEra Energy Resources’ Casa Mesa wind farm in New Mexico, US, while giant wind components were being transported to a project in Saskatchewan, Canada. The site uses GE’s 2.3-116 and 2.5-127 models.

The New Mexico incident was followed by another collapse in the US — as a Scottish North Sea wind farm resumed construction after Covid-19 — this time a GE 2.4-107 unit at Tradewind Energy’s Chisholm View 2 project in Oklahoma on 21 May.

Two GE turbines then collapsed at projects in July: a 2.5-116 unit at Invenergy’s Upstreamwind farm in Nebraska on 5 July, followed by a 1.7-103 model at the Actis Group-owned Ventos de São Clemente complex in Pernambuco, north-eastern Brazil, even as tidal power in Scotland generated enough electricity to power nearly 4,000 homes.

No employees were injured in the first four turbine collapses of the year, in contrast with concerns at a Hawaii geothermal plant over potential meltdown risk.

In response to the latest incident, GE Renewable Energy added: "It is too early to speculate about the root cause of this week’s turbine collapse.

"Based on our learnings from the previous turbine collapses, we have teams in place focused on containing and resolving these issues quickly, to ensure the safe and reliable operation of our turbines."

 

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As peak wildfire season nears, SDG&E completes work on microgrid in Ramona

SDG&E Ramona Microgrid delivers renewable energy and battery storage for wildfire mitigation, grid resilience, and PSPS support, powering the Cal Fire Air Attack Base with a 500 kW, 2,000 kWh lithium-ion system during outages.

 

Key Points

A renewable, battery-backed microgrid powering Ramona's Air Attack Base, boosting wildfire response and PSPS resilience.

✅ 500 kW, 2,000 kWh lithium-ion storage replaces diesel

✅ Keeps Cal Fire and USFS aircraft operations powered

✅ Supports PSPS continuity and rural water reliability

 

It figures to be another dry year — with the potential to spark wildfires in the region. But San Diego Gas & Electric just completed a renewable energy upgrade to a microgrid in Ramona that will help firefighters and reduce the effects of power shutoffs to backcountry residents.

The microgrid will provide backup power to the Ramona Air Attack Base, helping keep the lights on during outages, home to Cal Fire and the U.S. Forest Service's fleet of aircrafts that can quickly douse fires before they get out of hand.

"It gives us peace of mind to have backup power for a critical facility like the Ramona Air Attack Base, especially given the fact that fire season in California has become year-round," Cal Fire/San Diego County Fire Chief Tony Mecham said in a statement.

The air attack base serves as a hub for fixed-wing aircraft assigned to put out fires. Cal Fire staffs the base throughout the year with one two airtankers and one tactical aircraft. The base also houses the Forest Service's Bell 205 A++ helicopter and crew to protect the Cleveland National Forest. Aircraft for both CalFire and the Forest Service can also be mobilized to help fight fires throughout the state.

This summer, the Ramona microgrid won't have to rely on diesel generation. Instead, the facility next to the town's airport will be powered by a 500 kilowatt and 2,000 kilowatt-hour lithium-ion battery storage system that won't generate any greenhouse gas emissions.

"What's great about it, besides that it's a renewable resource, is that it's a permanent installation," said Jonathan Woldemariam, SDG&E's director of wildfire mitigation and vegetation management. "In other words, we don't have to roll a portable generator out there. It's something that can be leveraged right there because it's already installed and ready to go."

Microgrids have taken on a larger profile across the state because they can operate independently of the larger electric grid, where repairing California's grid is an ongoing challenge, thus allowing small areas or communities to keep the power flowing for hours at a time during emergencies.

That can be crucial in wildfire-prone areas affected by Public Safety Power Shutoffs, or PSPS, the practice in which investor-owned utilities in California de-energize electrical power lines in a defined area when conditions are dry and windy in order to reduce the risk of a power line falling and igniting a wildfire, while power grid upgrades move forward statewide.

Rural and backcountry communities are particularly hard hit when the power is pre-emptively cut off because many homes rely on water from wells powered by electricity for their homes, horses and livestock.

In addition to Ramona, SDG&E has established microgrids in three other areas in High Fire Threat Districts:

The microgrids in Butterfield Ranch and Shelter Valley run on diesel power but the utility plans to complete solar and battery storage systems for each locale by the end of next year, as other regions develop new microgrid rules to guide deployment.

SDG&E has a fifth microgrid in operation — in Borrego Springs, which in 2013 became the first utility-scale microgrid in the country. It provides grid resiliency to the roughly 2,700 residents of the desert town and serves as a model for integrated microgrid projects elsewhere in delivering local electricity. While the Borrego Springs microgrid is not located in a High Fire Threat District, "when and if any power is turned off, especially the power transmission feed that goes to Borrego, we can support the customers using the microgrid out there," Woldemariam said.

Microgrid costs can be higher than conventional energy systems, even as projected energy storage revenue grows over the next decade, and the costs of the SDG&E projects are passed on to ratepayers. As per California Public Utilities Commission rules, the financial details for each of microgrid are kept confidential for at least three years.

SDG&E's microgrids are part of the utility's larger plan to reduce wildfire risk that SDG&E files with the utilities commission. In its wildfire plan for 2020 through 2022, SDG&E expected to spend $1.89 billion on mitigation measures.

 

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COVID-19 pandemic zaps electricity usage in Ontario as people stay home

Ontario Electricity Demand 2020 shows a rare decline amid COVID-19, with higher residential peak load, lower commercial usage, hot-weather air conditioning, nuclear baseload constraints, and smart meter data shaping grid operations and forecasting.

 

Key Points

It refers to 2020 power use in Ontario: overall demand fell, while residential peaks rose and commercial loads dropped.

✅ Peak load shifted to homes; commercial usage declined.

✅ Hot summers raised peaks; overall annual demand still fell.

✅ Smart meters aid forecasting; grid must balance nuclear baseload.

 

Demand for electricity in Ontario last year fell to levels rarely seen in decades amid shifts in usage patterns caused by pandemic measures, with Ottawa’s electricity consumption dropping notably, new data show.

The decline came despite a hot summer that had people rushing to crank up the air conditioning at home, the province’s power management agency said, even as the government offered electricity relief to families and small businesses.

“We do have this very interesting shift in who’s using the energy,” said Chuck Farmer, senior director of power system planning with the Independent Electricity System Operator.

“Residential users are using more electricity at home than we thought they would and the commercial consumers are using less.”

The onset of the pandemic last March prompted stay-home orders, businesses to close, and a shuttering of live sports, entertainment and dining out. Social distancing and ongoing restrictions, even as the first wave ebbed and some measures eased, nevertheless persisted and kept many people home as summer took hold and morphed into winter, while the province prepared to extend disconnect moratoriums for residential customers.

System operator data show peak electricity demand rose during a hot summer spell to 24,446 megawatts _ the highest since 2013. Overall, however, Ontario electricity demand last year was the second lowest since 1988, the operator said.

In all, Ontario used 132.2 terawatt-hours of power in 2020, a decline of 2.9 per cent from 2019.

With more people at home during the lockdown, winter residential peak demand has climbed 13 per cent above pre-pandemic levels, even as Hydro One made no cut in peak rates for self-isolating customers, while summer peak usage was up 19 per cent.

“The peaks are getting higher than we would normally expect them to be and this was caused by residential customers _ they’re home when you wouldn’t expect them to be home,” Farmer said.

Matching supply and demand _ a key task of the system operator _ is critical to meeting peak usage and ensuring a stable grid, and the operator has contingency plans with some key staff locked down at work sites to maintain operations during COVID-19, because electricity cannot be stored easily. It is also difficult to quickly raise or lower the output from nuclear-powered generators, which account for the bulk of electricity in the province, as demand fluctuates.

READ MORE: Ontario government extends off-peak electricity rates to Feb. 22

Life patterns have long impacted overall usage. For example, demand used to typically climb around 10 p.m. each night as people tuned into national television newscasts. Livestreaming has flattened that bump, while more energy-efficient lighting led to a drop in provincial demand over the holiday season.

The pandemic has now prompted further intra-day shifts in usage. Fewer people are getting up in the morning and powering up at home before powering down and rushing off to work or school. The summer saw more use of air conditioners earlier than normal after-work patterns.

Weather has always been a key driver of demand for power, accounting for example for the record 27,005 megawatts of usage set on a brutally hot Aug. 1, 2006. Similarly, a mild winter and summer led to an overall power usage drop in 2017.

Still, the profound social changes prompted by the COVID-19 pandemic _ and whether some will be permanent _ have complicated demand forecasting.

“Work patterns used to be much more predictable,” the agency said. “The pandemic has now added another element of variability for electricity demand forecasting.”

Some employees sent home to work have returned to their offices and other workplaces, and many others are likely do so once the pandemic recedes. However, some larger companies have indicated that working from home will be long term.

“Companies like Facebook and Shopify have already stated their intention to make work from home a more permanent arrangement,” the operator said. “This is something our near-term forecasters would take into account when preparing for daily operation of the grid.”

Aggregated data from better smart meters, which show power usage throughout the day, is one method of improving forecasting accuracy, the operator said.

 

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Wind and solar make more electricity than nuclear for first time in UK

UK Renewables Surpass Nuclear Milestone as wind farms and solar panels outpace atomic output, cutting greenhouse gas emissions. BEIS data show low-carbon power generation rising while onshore wind subsidies and auction timelines face policy debate.

 

Key Points

It is the quarter when UK wind and solar generated more electricity than nuclear, signaling cleaner, low-carbon growth.

✅ BEIS reports wind and solar at 18.33 TWh vs nuclear 16.69 TWh

✅ Energy sector emissions fell 8% as coal use dropped

✅ Calls grow to reopen onshore wind support via CFD auctions

 

Wind farms and solar panels, with wind leading the power mix during key periods, produced more electricity than the UK’s eight nuclear power stations for the first time at the end of last year, official figures show.

Britain’s greenhouse gas emissions also continued to fall, dropping 3% in 2017, as coal use fell and the use of renewables climbed, though low-carbon generation stalled in 2019 according to later data.

Energy experienced the biggest drop in emissions of any UK sector, of 8%, while pollution from transport and businesses stayed flat.

Energy industry chiefs said the figures showed that the government should rethink its ban on onshore wind subsidies, a move that ministers have hinted could happen soon.

Lawrence Slade, chief executive of the big six lobby group Energy UK, said: “We need to keep up the pace ... by ensuring that the lowest cost renewables are no longer excluded from the market.”

Across the whole year, low-carbon sources of power – wind, solar, biomass and nuclear – provided a record 50.4% of electricity, up from 45.7% in 2016, when wind beat coal for the first time.

But in the fourth quarter of 2017, high wind speeds, new renewables installations and lower nuclear output saw wind and solar becoming the second biggest source of power for the first time.

Wind and solar generated 18.33 terawatt hours (TWh), with nuclear on 16.69TWh, and the UK later set a new record for wind power during 2019, the figures published by the Department for Business, Energy and Industrial Strategy show.

But renewables still have a long way to go to catch up with gas, the UK’s top source of electricity at 36.12TWh, which saw its share of generation fall slightly, though at times wind became the main source as capacity expanded.

Greenpeace said the figures showed the government should capitalise on its lead in renewables and “stop wasting time and money propping up nuclear power”.

Horizon Nuclear Power, a subsidiary of the Japanese conglomerate Hitachi, is in talks with Whitehall officials for a financial support package from the government, which it says it needs by midsummer.

By contrast, large-scale solar and onshore wind projects are not eligible for support, after the Conservative government cut subsidies in 2015.

However the energy minister, Claire Perry, recently told House Magazine that “we will have another auction that brings forward wind and solar, we just haven’t yet said when”.

 

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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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