Power system upgrades keep AC flowing

US SF6 Emissions Decline as NOAA analysis and EPA mitigation show progress, with atmospheric measurements and Greenhouse Gas Reporting verifying reductions from the electric power grid; sulfur hexafluoride's extreme global warming potential underscores inventory improvements.

Key Points

A documented drop in US sulfur hexafluoride emissions, confirmed by NOAA atmospheric data and EPA reporting reforms.

✅ NOAA towers and aircraft show 2007-2018 decline

✅ EPA reporting and utility mitigation narrowed inventory gaps

✅ Winter leaks and servicing signal further reduction options

A new NOAA analysis shows U.S. emissions of the super-potent greenhouse gas sulfur hexafluoride (SF6) have declined between 2007-2018, likely due to successful mitigation efforts by the Environmental Protection Agency (EPA) and the electric power industry, with attention to SF6 in the power industry across global markets. 

At the same time, significant disparities that existed previously between NOAA’s estimates, which are based on atmospheric measurements, and EPA’s estimates, which are based on a combination of reported emissions and industrial activity, have narrowed following the establishment of the EPA's Greenhouse Gas Reporting Program. The findings, published in the journal Atmospheric Chemistry and Physics, also suggest how additional emissions reductions might be achieved. 

SF6 is most commonly used as an electrical insulator in high-voltage equipment that transmits and distributes electricity, and its emissions have been increasing worldwide as electric power systems expand, even as regions hit milestones like California clean energy surpluses in recent years. Smaller amounts of SF6 are used in semiconductor manufacturing and in magnesium production. 

SF6 traps 25,000 times more heat than carbon dioxide over a 100-year time scale for equal amounts of emissions, and while CO2 emissions flatlined in 2019 globally, that comparison underscores the potency of SF6. That means a relatively small amount of the gas can have a significant impact on climate warming. Because of its extremely large global warming potential and long atmospheric lifetime, SF6 emissions will influence Earth’s climate for thousands of years.

In this study, researchers from NOAA’s Global Monitoring Laboratory, as record greenhouse gas concentrations drive demand for better data, working with colleagues at EPA, CIRES, and the University of Maryland, estimated U.S. SF6 emissions for the first time from atmospheric measurements collected at a network of tall towers and aircraft in NOAA’s Global Greenhouse Gas Reference Network. The researchers provided an estimate of SF6 emissions independent from the EPA’s estimate, which is based on reported SF6 emissions for some industrial facilities and on estimated SF6 emissions for others.

“We observed differences between our atmospheric estimates and the EPA’s activity-based estimates,” said study lead author Lei Hu, a Global Monitoring Laboratory researcher who was a CIRES scientist at the time of the study. “But by closely collaborating with the EPA, we were able to identify processes potentially responsible for a significant portion of this difference, highlighting ways to improve emission inventories and suggesting additional emission mitigation opportunities, such as forthcoming EPA carbon capture rules for power plants, in the future.” 

In the 1990s, the EPA launched voluntary partnerships with the electric power, where power-sector carbon emissions are falling as generation shifts, magnesium, and semiconductor industries to reduce SF6 emissions after the United States recognized that its emissions were significant. In 2011, large SF6 -emitting facilities were required to begin tracking and reporting their emissions under the EPA Greenhouse Gas Reporting Program. 

Hu and her colleagues documented a decline of about 60 percent in U.S. SF6 emissions between 2007-2018, amid global declines in coal-fired power in some years—equivalent to a reduction of between 6 and 20 million metric tons of CO2 emissions during that time period—likely due in part to the voluntary emission reduction partnerships and the EPA reporting requirement. A more modest declining trend has also been reported in the EPA’s national inventories submitted annually under the United Nations Framework Convention on Climate Change. 

Examining the differences between the NOAA and EPA independent estimates, the researchers found that the EPA’s past inventory analyses likely underestimated SF6 emissions from electrical power transmission and distribution facilities, and from a single SF6 production plant in Illinois. According to Hu, the research collaboration has likely improved the accuracy of the EPA inventories. The 2023 draft of the EPA’s U.S. Greenhouse Gas Emissions and Sinks: 1990-2021 used the results of this study to support revisions to its estimates of SF6 emissions from electrical transmission and distribution. 

The collaboration may also lead to improvements in the atmosphere-based estimates, helping NOAA identify how to expand or rework its network to better capture emitting industries or areas with significant emissions, according to Steve Montzka, senior scientist at GML and one of the paper’s authors.

Hu and her colleagues also found a seasonal variation in SF6 emissions from the atmosphere-based analysis, with higher emissions in winter than in summer. Industry representatives identified increased servicing of electrical power equipment in the southern states and leakage from aging brittle sealing materials in the equipment in northern states during winter as likely explanations for the enhanced wintertime emissions—findings that suggest opportunities for further emissions reductions.

“This is a great example of the future of greenhouse gas emission tracking, where inventory compilers and atmospheric scientists work together to better understand emissions and shed light on ways to further reduce them,” said Montzka.

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Drax Biomass Conversion accelerates renewable energy by replacing coal with wood pellets, sustainable forestry feedstock, and piloting carbon capture and storage, supporting the UK grid, emissions cuts, and a net-zero pathway.

Key Points

Drax Biomass Conversion is Drax's shift from coal to biomass with CCS pilots to cut emissions and aid UK's net-zero.

✅ Coal units converted to biomass wood pellets

✅ Sourced from sustainable forestry residues

✅ CCS pilots target lifecycle emissions cuts

A power station that used to be the biggest polluter in western Europe has made a near-complete switch to renewable energy, mirroring broader shifts as Denmark's largest energy company plans to end coal by 2023.

The Drax Power Station in Yorkshire, England, used to spew out millions of tons of carbon dioxide a year by burning coal. But over the past eight years, it has overhauled its operations by converting four of its six coal-fired units to biomass. The plant's owners say it now generates 15% of the country's renewable power, as Britain recently went a full week without coal power for the first time.

The change means that just 6% of the utility's power now comes from coal, as the wider UK coal share hits record lows across the national electricity system. The ultimate goal is to stop using coal altogether.

"We've probably reduced our emissions more than any other utility in the world by transforming the way we generate power," Will Gardner, CEO of the Drax Group, told CNN Business.

Subsidies have helped finance the switch to biomass, which consists of plant and agricultural matter and is viewed as a promising substitute for coal, and utilities such as Nova Scotia Power are also increasing biomass use. Last year, Drax received £789 million ($1 billion) in government support.

Is biomass good for the environment?

While scientists disagree over the extent to which biomass as a fuel is environmentally friendly, and some environmentalists urge reducing biomass use amid concerns about lifecycle emissions, Drax highlights that its supplies come from from sustainably managed and growing forests.

Most of the biomass used by Drax consists of low-grade wood, sawmill residue and trees with little commercial value from the United States. The material is compressed into sawdust pellets.

Gardner says that by purchasing bits of wood not used for construction or furniture, Drax makes it more financially viable for forests to be replanted. And planting new trees helps offset biomass emissions.

Forests "absorb carbon as they're growing, once they reach maturity, they stop absorbing carbon," said Raphael Slade, a senior research fellow at Imperial College London.

But John Sterman, a professor at MIT's Sloan School of Management, says that in the short term burning wood pellets adds more carbon to the atmosphere than burning coal.

That carbon can be absorbed by new trees, but Sterman says the process can take decades.

"If you're looking at five years, [biomass is] not very good ... If you're looking at a century-long time scale, which is the sort of time scale that many foresters plan, then [biomass] can be a lot more beneficial," says Slade.

Carbon capture

Enter carbon capture and storage technology, which seeks to prevent CO2 emissions from entering the atmosphere and has been touted as a possible solution to the climate crisis.

Drax, for example, is developing a system to capture the carbon it produces from burning biomass. But that could be 10 years away.

The Coal King is racing to avoid bankruptcy

The power station is currently capturing just 1 metric ton of CO2 emissions per day. Gardner says it hopes to increase this to 10,000 metric tons per day by the mid to late 2020s.

"The technology works but scaling it up and rolling it out, and financing it, are going to be significant challenges," says Slade.

The Intergovernmental Panel on Climate Change shares this view. The group said in a 2018 report that while the potential for CO2 capture and storage was considerable, its importance in the fight against climate change would depend on financial incentives for deployment, and whether the risks of storage could be successfully managed. These include a potential CO2 pipeline break.

In the United Kingdom, the government believes that carbon capture and storage will be crucial to reaching its goal of achieving net-zero greenhouse gas emissions by 2050, even as low-carbon generation stalled in 2019 according to industry analysis.

It has committed to consulting on a market-based industrial carbon capture framework and in June awarded £26 million ($33 million) in funding for nine carbon capture, usage and storage projects, amid record coal-free generation on the British grid.

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German Energy Price Brakes harness price signals in a market-based policy, cutting gas consumption, preserving industrial output, and supporting CO2 reduction, showcasing Germany's resilience and adaptation while protecting households and businesses across Europe.

Key Points

Fixed-amount subsidies preserving price signals to curb gas use, shield consumers, and sustain industrial output.

✅ Maintains incentives via market-based price signals

✅ Cuts gas consumption without distorting EU markets

✅ Protects households and industry while curbing CO2

German industry and society are once again proving much more resilient and adaptable than certain people feared. Horror scenarios of a dangerous energy rationing or a massive slump in our economy have often been bandied about. But we are nowhere near that. With a challenging year just behind us, this is good news — not only for Germany, but also for Europe, where France-Germany energy cooperation has strengthened solidarity.

Companies and households reacted swiftly to the sharp increases in energy prices, in line with momentum in the global energy transition seen across markets. They installed more efficient heating or production facilities, switched to alternatives and imported intermediate products. The results are encouraging: German households and businesses have reduced gas consumption significantly, despite recent cold weather. From the start of the war in Ukraine to mid-December industrial gas consumption in Germany was (temperature-adjusted) around 20 per cent lower than the average level for the preceding three years. Even if some firms have cut back production, especially in energy-intensive sectors, industrial output as a whole has only fallen by about 1 per cent since the start of 2022. Added to this, in a survey released by the Ifo institute in November, over a third of German companies saw the potential to reduce gas consumption further without endangering output.

Instead of imposing excessive laws and regulations, we have relied on price signals and the prudence of market participants to create the right incentives and reduce gas consumption, as falling costs like record-low solar power prices continue to reinforce those signals across sectors.

We will follow this approach in coming months, when energy savings will remain important, even as the EU electricity outlook anticipates sharply higher demand by 2050. Our latest relief measures will not distort price signals. To this end, the Bundestag approved gas and electricity price brakes in its final session in 2022. They are designed to function without any intervention in markets or prices. This system will pay out a fixed amount relative to previous years’ consumption and the current difference to a reference price — regardless of current consumption.

Energy price brakes are the main component of Germany’s “protective shield”, which makes up to €200bn available for measures in 2022 to 2024. Seen in relation to the German economy’s size, its past heavy reliance on Russian energy imports and the fact that the measures will expire in 2024, these are balanced and expedient mechanisms. In contrast to instruments used in other countries, our new arrangements will not affect the price formation process driven by supply and demand, or on incentives to save gas. Companies and households will continue to save the full market price when they reduce consumption by a unit of gas or electricity. In this way, the price brakes also avoid the creation of additional demand for gas at the expense of consumers in other European countries, even as Europe’s Big Oil turning electric signals broader structural shifts in energy markets. No one need fear that competition will be distorted or that gas will be bought up. Indeed, a recent IMF working paper on cushioning the impact of high energy prices on households explicitly praises the German energy price brakes.

Current developments confirm the effectiveness of a market-based approach — and show that we should also rely on price signals when it comes to reducing CO₂ emissions, as suggested by IEA CO2 trends in recent years. Last year, households and companies had only a few weeks to adapt, yet we have already seen a strong response. The effect of CO₂ prices can be even stronger, as adaptation is possible over a much longer time and they additionally affect expectations and long-term decisions. Regulatory interventions and subsidy schemes, even if well targeted, cannot compete with market co-ordination and incentives that support individual decision-making and promote innovation.

Europe and Germany can weather this crisis without a collapse in industrial production. We also have an opportunity to deal efficiently with the move to climate neutrality, aligned with Germany’s hydrogen strategy for imported low-carbon fuels. In both cases, we should have confidence in price signals as well as in the power of people and business to innovate and adapt.

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Minnesota Carbon-Free Power by 2050 aims to shift utilities to renewable energy, wind and solar, boosting efficiency while managing grid reliability, emissions, and costs under a clean energy mandate and statewide climate policy.

Key Points

A statewide goal to deliver 100% carbon-free power by 2050, prioritizing renewables, efficiency, and grid reliability.

✅ Targets 100% carbon-free electricity statewide by 2050

✅ Prioritizes wind, solar, and efficiency before fossil fuels

✅ Faces utility cost, reliability, and legislative challenges

Gov. Tim Walz's plan for Minnesota to get 100 percent of its electricity from carbon-free sources by 2050, similar to California's 100% carbon-free mandate in scope, was criticized Tuesday at its first legislative hearing, with representatives from some of the state's smaller utilities saying they can't meet that goal.

Commerce Commissioner Steve Kelley told the House climate committee that the Democratic governor's plan is ambitious. But he said the state's generating system is "aging and at a critical juncture," with plants that produce 70 percent of the state's electricity coming up for potential retirement over the next two decades. He said it will ensure that utilities replace them with wind, solar and other innovative sources, and increased energy efficiency, before turning to fossil fuels.

"Utilities will simply need to demonstrate why clean energy would not work whenever they propose to replace or add new generating capacity," he said.

Walz's plan, announced last week, seeks to build on the success of a 2007 law that required Minnesota utilities to get at least 25 percent of their electricity from renewable sources by 2025. The state largely achieved that goal in 2017 thanks to the growth of wind and solar power, and the topic of climate change has only grown hotter, with some proposals like a fully renewable grid by 2030 pushing even faster timelines, hence the new goal for 2050.

But Joel Johnson, a lobbyist for the Minnkota Power Cooperative, testified that the governor's plan is "misguided and unrealistic" even with new technology to capture carbon dioxide emissions from power plants. Johnson added that even the big utilities that have set goals of going carbon-free by mid-century, such as Minneapolis-based Xcel Energy, acknowledge they don't know yet how they'll hit the net-zero electricity by mid-century target they have set.

Minnkota serves northwestern Minnesota and eastern North Dakota.

Tim Sullivan, president and CEO of the Wright-Hennepin Cooperative Electric Association in the Twin Cities area, said the plan is a "bad idea" for the 1.7 million state electric consumers served by cooperatives. He said Minnesota is a "minuscule contributor" to total global carbon emissions, even as the EU plans to double electricity use by 2050 to meet electrification demands.

"The bill would have a devastating impact on electric consumers," Sullivan said. "It represents, in our view, nothing short of a first-order threat to the safety and reliability of Minnesota's grid."

Isaac Orr is a policy fellow at the Minnesota-based conservative think tank, the Center for the American Experiment, which released a report critical of the plan Tuesday. Orr said all Minnesota households would face higher energy costs and it would harm energy-intensive industries such as mining, manufacturing and health care, while doing little to reduce global warming.

"This does not pass a proper cost-benefit analysis," he testified.

Environmental groups, including Conservation Minnesota and the Sierra Club, supported the proposal while acknowledging the challenges, noting that cleaning up electricity is critical to climate pledges in many jurisdictions.

"Our governor has called climate change an existential crisis," said Kevin Lee, director of the climate and energy program at the Minnesota Center for Environmental Advocacy. "This problem is the defining challenge of our time, and it can feel overwhelming."

Rep. Jean Wagenius, the committee chairwoman and Minneapolis Democrat who's held several hearings on the threats that climate change poses, said she expected to table the bill for further consideration after taking more testimony in the evening and would not hold a vote Tuesday.

While the bill has support in the Democratic-controlled House, it's not scheduled for action in the Republican-led Senate. Rep. Pat Garofalo, a Farmington Republican, quipped that it "has a worse chance of becoming law than me being named the starting quarterback for the Minnesota Vikings."

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Alberta Power Grid Level 2 Alert signals AESO reserve power usage, load management, supply shortage from generator outages, low wind, and limited imports, urging peak demand conservation to avoid blackouts and preserve grid reliability.

Key Points

An AESO status where reserves power the grid and load management is used during supply constraints to prevent blackouts.

✅ Triggered by outages, low wind, and reduced import capacity

✅ Peak hours 4 to 7 pm saw conservation requests

✅ Several hundred MW margin from Level 3 load shedding

Alberta's energy grid ran on reserves Wednesday, after multiple factors led to a supply shortage, a scenario explored in U.S. grid COVID response discussions as operators plan for contingencies.

At 3:52 p.m. Wednesday, the Alberta Electric System Operator issued a Level 2 alert, meaning that reserves were being used to supply energy requirements and that load management procedures had been implemented, while operators elsewhere adopted Ontario power staffing lockdown measures during COVID-19 for continuity. The alert ended at 6:06 p.m.

"This is due to unplanned generator outages, low wind and a reduction of import capability," the agency said in a post to social media. "Supply is tight but still meeting demand."

AESO spokesperson Mike Deising said the intertie with Saskatchewan had tripped off, and an issue on the British Columbia side of the border, as seen during BC Hydro storm response events, meant the province couldn't import power. 

"There are no blackouts … this just means we're using our reserve power, and that's a standard procedure we'll deploy," he said. 

AESO had asked that people reduce their energy consumption between 4 and 7 p.m., similar to Cal ISO conservation calls during grid strain, which is typically when peak use occurs. 

Deising said the system was several hundred MWs away from needing to move to an alert Level 3, with utilities such as FortisAlberta precautions in place to support continuity, which is when power is cut off to some customers in order to keep the system operating. Deising said Level 2 alerts are fairly rare and occur every few years. The last Level 3 alert was in 2013. 

According to the supply and demand report on AESO's website, the load on the grid at 5 p.m. was 10,643 MW.

That's down significantly from last week, when a heat wave pushed demand to record highs on the grid, with loads in the 11,700 MW range, contrasting with Ontario demand drop during COVID when many stayed home. 

A heat warning was issued Wednesday for Edmonton and surrounding areas shortly before 4 p.m., with temperatures above 29 C expected over the next three days, with many households seeing residential electricity use up during such periods. 

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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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