FPL Group lauded for quality of climate change disclosure

Sulphur Hexafluoride (SF6) Emissions drive rising greenhouse gas impacts in electrical switchgear, power grids, and renewables, with extreme global warming potential, long atmospheric lifetime, and leakage risks challenging climate targets and grid decarbonization.

Key Points

SF6 emissions are leaks from electrical switchgear and grids, a high-GWP gas with ~1,000-year lifetime.

✅ 23,500x CO2 global warming potential (GWP)

✅ Leaks from switchgear, breakers, gas-insulated substations

✅ Clean air and vacuum alternatives emerging for MV/HV

Sulphur hexafluoride, or SF6, is widely used in the electrical industry to prevent short circuits and accidents.

But leaks of the little-known gas in the UK and the rest of the EU in 2017 were the equivalent of putting an extra 1.3 million cars on the road.

Levels are rising as an unintended consequence of the green energy boom and the broader global energy transition worldwide.

Cheap and non-flammable, SF6 is a colourless, odourless, synthetic gas. It makes a hugely effective insulating material for medium and high-voltage electrical installations.

It is widely used across the industry, from large power stations to wind turbines to electrical sub-stations in towns and cities.

It prevents electrical accidents and fires.

However, the significant downside to using the gas is that it has the highest global warming potential of any known substance. It is 23,500 times more warming than carbon dioxide (CO2).

Just one kilogram of SF6 warms the Earth to the same extent as 24 people flying London to New York return.

It also persists in the atmosphere for a long time, warming the Earth for at least 1,000 years.

So why are we using more of this powerful warming gas?

The way we make electricity around the world is changing rapidly, with New Zealand's push to electrify in its energy system.

Where once large coal-fired power stations brought energy to millions, the drive to combat climate change and to move away from coal means they are now being replaced by mixed sources of power including wind, solar and gas.

This has resulted in many more connections to the electricity grid, and with EU electricity use could double by 2050, a rise in the number of electrical switches and circuit breakers that are needed to prevent serious accidents.

Collectively, these safety devices are called switchgear. The vast majority use SF6 gas to quench arcs and stop short circuits.

"As renewable projects are getting bigger and bigger, we have had to use it within wind turbines specifically," said Costa Pirgousis, an engineer with Scottish Power Renewables on its new East Anglia wind farm, which doesn't use SF6 in turbines.

"As we are putting in more and more turbines, we need more and more switchgear and, as a result, more SF6 is being introduced into big turbines off shore.

"It's been proven for years and we know how it works, and as a result it is very reliable and very low maintenance for us offshore."

How do we know that SF6 is increasing?

Across the entire UK network of power lines and substations, there are around one million kilograms of SF6 installed.

A study from the University of Cardiff found that across all transmission and distribution networks, the amount used was increasing by 30-40 tonnes per year.

This rise was also reflected across Europe with total emissions from the 28 member states in 2017 equivalent to 6.73 million tonnes of CO2. That's the same as the emissions from 1.3 million extra cars on the road for a year.

Researchers at the University of Bristol who monitor concentrations of warming gases in the atmosphere say they have seen significant rises in the last 20 years.

"We make measurements of SF6 in the background atmosphere," said Dr Matt Rigby, reader in atmospheric chemistry at Bristol.

"What we've seen is that the levels have increased substantially, and we've seen almost a doubling of the atmospheric concentration in the last two decades."

How does SF6 get into the atmosphere?

The most important means by which SF6 gets into the atmosphere is from leaks in the electricity industry.

Electrical company Eaton, which manufactures switchgear without SF6, says its research indicates that for the full life-cycle of the product, leaks could be as high as 15% - much higher than many other estimates.

Louis Schaeffer, electrical business manager at Eaton, said: "The newer gear has very low leak rates but the key question is do you have newer gear?

"We looked at all equipment and looked at the average of all those leak rates, and we didn't see people taking into account the filling of the gas. Plus, we looked at how you recycle it and return it and also included the catastrophic leaks."

How damaging to the climate is this gas?

Concentrations in the atmosphere are very small right now, just a fraction of the amount of CO2 in the air.

However, the global installed base of SF6 is expected to grow by 75% by 2030, as data-driven electricity demand surges worldwide.

Another concern is that SF6 is a synthetic gas and isn't absorbed or destroyed naturally. It will all have to be replaced and destroyed to limit the impact on the climate.

Developed countries are expected to report every year to the UN on how much SF6 they use, but developing countries do not face any restrictions on use.

Right now, scientists are detecting concentrations in the atmosphere that are 10 times the amount declared by countries in their reports. Scientists say this is not all coming from countries like India, China and South Korea.

One study found that the methods used to calculate emissions in richer countries "severely under-reported" emissions over the past two decades.

Why hasn't this been banned?

SF6 comes under a group of human-produced substances known as F-gases. The European Commission tried to prohibit a number of these environmentally harmful substances, including gases in refrigeration and air conditioning, back in 2014.

But they faced strong opposition from industries across Europe.

"In the end, the electrical industry lobby was too strong and we had to give in to them," said Dutch Green MEP Bas Eickhout, who was responsible for the attempt to regulate F-gases.

"The electric sector was very strong in arguing that if you want an energy transition, and you have to shift more to electricity, you will need more electric devices. And then you also will need more SF6.

"They used the argument that otherwise the energy transition would be slowed down."

What do regulator and electrical companies say about the gas?

Everyone is trying to reduce their dependence on the gas, and US control efforts suggest targeted policies can drive declines, as it is universally recognised as harmful to the climate.

In the UK, energy regulator Ofgem says it is working with utilities to try to limit leaks of the gas.

"We are using a range of tools to make sure that companies limit their use of SF6, a potent greenhouse gas, where this is in the interest of energy consumers," an Ofgem spokesperson told BBC News.

"This includes funding innovation trials and rewarding companies to research and find alternatives, setting emissions targets, rewarding companies that beat those targets, and penalising those that miss them."

Are there alternatives - and are they very expensive?

The question of alternatives to SF6 has been contentious over recent years.

For high-voltage applications, experts say there are very few solutions that have been rigorously tested.

"There is no real alternative that is proven," said Prof Manu Haddad from the school of engineering at Cardiff University.

"There are some that are being proposed now but to prove their operation over a long period of time is a risk that many companies don't want to take."

Medium voltage operations there are several tried-and-tested materials. Some in the industry say that the conservative nature of the electrical industry is the key reason that few want to change to a less harmful alternative.

"I will tell you, everyone in this industry knows you can do this; there is not a technical reason not to do it," said Louis Schaffer from Eaton.

"It's not really economic; it's more a question that change takes effort and if you don't have to, you won't do it."

Some companies are feeling the winds of change

Sitting in the North Sea some 43km from the Suffolk coast, Scottish Power Renewables has installed one of world's biggest wind farms, in line with a sustainable electric planet vision, where the turbines will be free of SF6 gas.

East Anglia One will see 102 of these towering generators erected, with the capacity to produce up to 714MW (megawatts) of power by 2020, enough to supply half a million homes.

Previously, an installation like this would have used switchgear supplied with SF6, to prevent the electrical accidents that can lead to fires.

Each turbine would normally have contained around 5kg of SF6, which, if it leaked into the atmosphere, would add the equivalent of around 117 tonnes of carbon dioxide. This is roughly the same as the annual emissions from 25 cars.

"In this case we are using a combination of clean air and vacuum technology within the turbine. It allows us to still have a very efficient, reliable, high-voltage network but to also be environmentally friendly," said Costa Pirgousis from Scottish Power Renewables.

"Once there are viable alternatives on the market, there is no reason not to use them. In this case, we've got a viable alternative and that's why we are using it."

But even for companies that are trying to limit the use of SF6, there are still limitations. At the heart of East Anglia One sits a giant offshore substation to which all 102 turbines will connect. It still uses significant quantities of the highly warming gas.

What happens next ?

The EU will review the use of SF6 next year and will examine whether alternatives are available. However, even the most optimistic experts don't think that any ban is likely to be put in place before 2025.

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NRC Advanced Reactor Licensing streamlines a risk-informed, performance-based, technology-inclusive pathway for advanced non-light water reactors, aligning with NEIMA to enable predictable regulatory reviews, inherent safety, clean energy deployment, and industrial heat, hydrogen, and desalination applications.

Key Points

A risk-informed, performance-based NRC pathway streamlining licensing for advanced non-light water reactors.

✅ Aligned with NEIMA: risk-informed, performance-based, tech-inclusive

✅ Predictable licensing for advanced non-light water reactor designs

✅ Enables clean heat, hydrogen, desalination beyond electricity

The US Nuclear Regulatory Commission (NRC) voted 4-0 to approve the implementation of a more streamlined and predictable licensing pathway for advanced non-light water reactors, aligning with nuclear innovation priorities identified by industry advocates, the Nuclear Energy Institute (NEI) announced, and amid regional reliability measures such as New England emergency fuel stock plans that have drawn cost scrutiny.

This approach is consistent with the Nuclear Energy Innovation and Modernisation Act (NEIMA), a nuclear innovation act passed in 2019 by the US Congress calling for the development of a risk-informed, performance-based and technology inclusive licensing process for advanced reactor developers.

NEI Chief Nuclear Officer Doug True said: “A modernised regulatory framework is a key enabler of next-generation nuclear technologies that, amid ACORE’s challenge to DOE subsidy proposals in energy market proceedings, can help us meet our energy needs while protecting the climate. The Commission’s unanimous approval of a risk-informed and performance-based licensing framework paves the way for regulatory reviews to be aligned with the inherent safety characteristics, smaller reactor cores and simplified designs of advanced reactors.”

Over the last several years the industry’s Licensing Modernisation Project, sponsored by US Department of Energy, led by Southern Nuclear, and supported by NEI’s Advanced Reactor Regulatory Task Force, and influenced by a presidential order to bolster uranium and nuclear energy, developed the guidance for this new framework. Amid shifts in the fuel supply chain, including the U.S. ban on Russian uranium, this approach will inform the development of a new rule for licensing advanced reactors, which NEIMA requires.

“A well-defined licensing path will benefit the next generation of nuclear plants, especially as regions consider New England market overhaul efforts, which could meet a wide range of applications beyond generating electricity such as producing heat for industry, desalinating water, and making hydrogen – all without carbon emissions,” True noted.

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H2 Gateway Hydrogen Network accelerates clean energy in B.C., building electrolysis plants and hydrogen fueling stations for zero-emission vehicles, heavy-duty trucks, and long-haul transit, supporting decarbonization, green hydrogen supply, and infrastructure investment.

Key Points

A $900M B.C. initiative by HTEC to build electrolysis plants and 20 hydrogen fueling stations for zero-emission transport.

✅ $900M project with HTEC, CIB, and B.C. government

✅ 3 electrolysis plants plus byproduct liquefaction in North Vancouver

✅ Up to 20 stations; 14 for heavy-duty vehicles in B.C. and Alberta

British Columbia is taking a significant step towards a cleaner future with a brand new $900 million project. This initiative, spearheaded by hydrogen company HTEC and supported by the CIB in B.C. and the B.C. government, aims to establish a comprehensive hydrogen network across the province. This network will encompass both hydrogen production plants and fueling stations, marking a major leap in developing hydrogen infrastructure in B.C.

The project, dubbed "H2 Gateway," boasts several key components. At its core lies the construction of three brand new electrolysis hydrogen production plants. These facilities will be strategically located in Burnaby, Nanaimo, and Prince George, ensuring a wide distribution of hydrogen fuel. An additional facility in North Vancouver will focus on liquefying byproduct hydrogen, maximizing resource efficiency.

The most visible aspect of H2 Gateway will undoubtedly be the network of hydrogen fueling stations. The project envisions up to 20 stations spread across British Columbia and Alberta, complementing the province's Electric Highway build-out, with 18 being situated within B.C. itself. This extensive network will significantly enhance the accessibility of hydrogen fuel, making it a more viable option for motorists. Notably, 14 of these stations will be designed to handle heavy-duty vehicles, catering to the transportation sector's clean energy needs.

The economic and environmental benefits of H2 Gateway are undeniable. The project is expected to generate nearly 300 jobs, aligning with recent grid job creation efforts, providing a much-needed boost to the B.C. economy. More importantly, the widespread adoption of hydrogen fuel promises significant reductions in greenhouse gas emissions. Hydrogen-powered vehicles produce zero tailpipe emissions, making them a crucial tool in combating climate change.

British Columbia's investment in hydrogen infrastructure aligns with a global trend. As countries strive to achieve ambitious climate goals, hydrogen is increasingly viewed as a promising clean energy source. Hydrogen fuel cells offer several advantages over traditional electric vehicles, and while B.C. leads the country in going electric, they boast longer driving ranges and shorter refueling times, making them particularly attractive for long-distance travel and heavy-duty applications.

While H2 Gateway represents a significant step forward, challenges remain. The production of clean hydrogen, often achieved through electrolysis using renewable energy sources, faces power supply challenges and requires substantial initial investment. Additionally, the number of hydrogen-powered vehicles on the road is still relatively low.

However, projects like H2 Gateway are crucial in overcoming these hurdles. By creating a robust hydrogen infrastructure, B.C. is sending a strong signal to the industry and, alongside BC Hydro's EV charging expansion across southern B.C., is building a comprehensive clean transportation network. This investment will not only benefit the environment but also incentivize the development and adoption of hydrogen-powered vehicles. As the technology matures and production costs decrease, hydrogen fuel has the potential to revolutionize transportation and play a key role in a sustainable future.

The road ahead for hydrogen may not be entirely smooth, but British Columbia's commitment to H2 Gateway demonstrates a clear vision. By investing in clean energy infrastructure, the province is not only positioning itself as a leader in the fight against climate change, with Canada and B.C. investing in green energy solutions to accelerate progress, but also paving the way for a more sustainable transportation landscape.

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EPA Telework Policy restricts remote work, balancing work-from-home guidance during the COVID-19 pandemic with flexible schedules, union contracts, OMB guidance, and federal workforce rules, impacting managers, SES staff, and non-bargaining employees nationwide.

Key Points

A directive limiting many EPA staff to two telework days weekly, with pandemic exceptions and flexible schedules.

✅ Limits telework to two days per week for many employees

✅ Allows flexible schedules, including maxiflex, during emergencies

✅ Aligns with OMB, OPM, CDC guidance; honors union agreements

EPA has moved forward on a new policy that would restrict telework even as agency leadership has encouraged staff to work from home during the coronavirus outbreak.

The new EPA order obtained by E&E News would require employees to report to the office at least three days every week.

"Full-time employees are expected to report to the official worksite and duty station a minimum of three (3) days per week," says the order, dated as approved on Feb. 27. It went into effect March 15 — that night, EPA Administrator Andrew Wheeler authorized telework for the entire agency due to the pandemic.

The order focuses on EPA employees' work schedules and gives them new flexibilities that could come in handy during a public health emergency like the COVID-19 virus, when parts of the power sector consider on-site staffing to ensure continuity.

It also stipulates a deep reduction in EPA employees' capability to work remotely, leaving them with two days of telework per week. An agency order on telework, issued in January 2016, said staff could telework full time.

"The EPA supports the use of telework," said that order. "Regular telework may range from one day per pay period up to full time."

An EPA spokeswoman said the new order doesn't change the agency's guidance to staff to work from home during the pandemic.

"The health and safety of our employees is our top priority, and that is why we have requested that all employees telework, even as residential electricity use increases with more people at home, until at least April 3. There is no provision in the work schedules policy, telework policy or collective bargaining agreement that limits this request," said the spokeswoman.

"While EPA did implement the national work schedule policy effective 3/15/2020, it was implemented in order to provide increased work schedule flexibilities for non-bargaining unit employees who were not previously afforded flexible schedules, including maxiflex," she added.

"The implementation of the policy does not currently impact telework opportunities for EPA employees, and EPA has strongly encouraged all staff to telework," she said.

Still, the new order has caused consternation among EPA employees.

One EPA manager described it as another move by the Trump administration to restrict telework across the government.

"Amidst the COVID-19 crisis, this policy seems particularly ill-timed and unwise. It doesn't even give the administration the chance to evaluate the situation once the COVID-19 pandemic passes," said the manager.

"I think this is a dramatic change in the flexibilities available to the EPA employees without any data to support such a drastic move," the manager said. "It has huge ramifications for employees, many of whom commute over an hour each way to the office, increasing air pollution in the process."

Another EPA staffer said, "I honestly think such an order, given current circumstances, would elicit little more than a scoff and a smirk."

The person added, "How tone-deaf and heavy-handed can one administration be?"

Inside EPA first reported on the new order. E&E News obtained the memo independently.

The recently issued policy applies only to non-bargaining-unit employees, including "full-time and part-time" agency staff as well as "supervisors and managers in the competitive, excepted, Senior Level, Scientific and Professional, and Senior Executive Service positions."

In addition, the order covers "Public Health Service Officers, Schedule C, Administratively Determined employees and non-EPA employees serving on Intergovernmental Personnel Act assignments to EPA."

Nevertheless, EPA employees covered under union contracts must adhere to those contracts if the policy runs counter to them.

"If provisions of this order conflict with the provisions of a collective bargaining agreement, the provisions of the agreement must be applied," the order says.

EPA has taken a more restrictive approach with the agency's largest union, American Federation of Government Employees Council 238, which represents about 7,500 EPA employees. EPA imposed a contract on the council's bargaining unit employees last July that limited them to one day of telework per week, among other changes that triggered union protests.

EPA and AFGE have since relaunched contract negotiations, and how to handle telework is one of the issues under discussion. Both sides committed to complete those bargaining talks by April 15 and work with the Federal Service Impasses Panel if needed (Greenwire, Feb. 27).

Both sides of the telework debate
EPA's new order has been under consideration for some time.

E&E News obtained a draft version last year. The agency had circulated it for comment in July, noting the proposal "limits the number of days an employee may telework per week," among other changes (Greenwire, Sept. 12, 2019).

EPA, like other federal agencies under the Trump administration, has sought to reduce employees' telework. That effort, though, has run into the headwinds of a global pandemic, with a U.S. grid warning highlighting broader risks, leading agency leaders to reverse course and now encourage staff to work remotely in order to stop the spread of the COVID-19 virus.

Wheeler in an email last week told staff that he authorized telework for employees across the country. Federal worker unions had sought the opportunity for remote work on behalf of EPA employees, and the agency had already relaxed telework policies at various offices the prior week where the coronavirus had begun to take hold.

The EPA spokeswoman said the agency moved toward telework after guidance from other agencies.

"Consistent with [Office of Management and Budget], [Centers for Disease Control and Prevention] and [Office of Personnel Management] guidance, along with state and local directives, we have taken swift action in regions and at headquarters to implement telework for all employees. We continue to tell all employees to telework," said the spokeswoman.

Wheeler said in a later video message that his expectation was most EPA employees were working from home.

"I understand that this is a difficult and scary time for all of us," said the EPA administrator.

The coronavirus has become a real challenge for EPA, and utilities like BC Hydro Site C updates illustrate broader operational adjustments.

Agency staff have been exposed to the virus while some have tested positive, and nuclear plant workers have raised similar concerns, according to internal emails. That has led to employees self-quarantining while their colleagues worry they may next fall ill (Greenwire, March 20).

One employee said that since EPA's operations have been maintained with staff working from home, even as household electricity bills rise for many, it's harder for the Trump administration to justify restricting remote work.

"With the current climate, I think employees have shown we can keep the agency going with nearly 95% teleworking full time. It makes their argument hard to justify in light of things," said the EPA employee.

The Trump administration overall has pushed for more remote work by the federal workforce in the battle with the COVID-19 virus. The Office of Management and Budget issued guidance to agencies last week "to minimize face-to-face interactions" and "maximize telework across the nation."

Lawmakers have also pushed to expand telework for federal workers due to the virus.

Democratic senators sent a letter last week urging President Trump to issue an executive order directing agencies to use telework.

In addition, Sens. James Lankford (R-Okla.), Chris Van Hollen (D-Md.) and Kyrsten Sinema (D-Ariz.) introduced legislation that would allow federal employees to telework full time during the pandemic.

Some worry EPA's new order could further sour morale at the agency after the pandemic passes, as other utilities consider measures like unpaid days off to trim costs. Employees may leave if they can't work from home more.

"People will quit EPA over something like this. Maybe that's the goal," said the EPA manager.

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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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Hourly Electricity Emissions Tracking maps grid balancing areas, embodied emissions, and imports/exports, revealing carbon intensity shifts across PJM, ERCOT, and California ISO, and clarifying renewable energy versus coal impacts on health and climate.

Key Points

An hourly method tracing generation, flows, and embodied emissions to quantify carbon intensity across US balancing areas.

✅ Hourly traces of imports/exports and generation mix

✅ Consumption-based carbon intensity by balancing area

✅ Policy insights for renewables, coal, health costs

In the United States, electricity generation accounts for nearly 30% of our carbon emissions. Some states have responded to that by setting aggressive renewable energy standards; others are hoping to see coal propped up even as its economics get worse. Complicating matters further is the fact that many regional grids are integrated, and as America goes electric the stakes grow, meaning power generated in one location may be exported and used in a different state entirely.

Tracking these electricity exports is critical for understanding how to lower our national carbon emissions. In addition, power from a dirty source like coal has health and environment impacts where it's produced, and the costs of these aren't always paid by the parties using the electricity. Unfortunately, getting reliable figures on how electricity is produced and where it's used is challenging, even for consumers trying to find where their electricity comes from in the first place, leaving some of the best estimates with a time resolution of only a month.

Now, three Stanford researchers—Jacques A. de Chalendar, John Taggart, and Sally M. Benson—have greatly improved on that standard, and they have managed to track power generation and use on an hourly basis. The researchers found that, of the 66 grid balancing areas within the United States, only three have carbon emissions equivalent to our national average, and they have found that imports and exports of electricity have both seasonal and daily changes. de Chalendar et al. discovered that the net results can be substantial, with imported electricity increasing California's emissions/power by 20%.

Hour by hour
To figure out the US energy trading landscape, the researchers obtained 2016 data for grid features called balancing areas. The continental US has 66 of these, providing much better spatial resolution on the data than the larger grid subdivisions. This doesn't cover everything—several balancing areas in Canada and Mexico are tied in to the US grid—and some of these balancing areas are much larger than others. The PJM grid, serving Pennsylvania, New Jersey, and Maryland, for example, is more than twice as large as Texas' ERCOT, in a state that produces and consumes the most electricity in the US.

Despite these limitations, it's possible to get hourly figures on how much electricity was generated, what was used to produce it, and whether it was used locally or exported to another balancing area. Information on the generating sources allowed the researchers to attach an emissions figure to each unit of electricity produced. Coal, for example, produces double the emissions of natural gas, which in turn produces more than an order of magnitude more carbon dioxide than the manufacturing of solar, wind, or hydro facilities. These figures were turned into what the authors call "embodied emissions" that can be traced to where they're eventually used.

Similar figures were also generated for sulfur dioxide and nitrogen oxides. Released by the burning of fossil fuels, these can both influence the global climate and produce local health problems.

Huge variation
The results were striking. "The consumption-based carbon intensity of electricity varies by almost an order of magnitude across the different regions in the US electricity system," the authors conclude. The low is the Bonneville Power grid region, which is largely supplied by hydropower; it has typical emissions below 100kg of carbon dioxide per megawatt-hour. The highest emissions come in the Ohio Valley Electric region, where emissions clear 900kg/MW-hr. Only three regional grids match the overall grid emissions intensity, although that includes the very large PJM (where capacity auction payouts recently fell), ERCOT, and Southern Co balancing areas.

Most of the low-emissions power that's exported comes from the Pacific Northwest's abundant hydropower, while the Rocky Mountains area exports electricity with the highest associated emissions. That leads to some striking asymmetries. Local generation in the hydro-rich Idaho Power Company has embodied emissions of only 71kg/MW-hr, while its imports, coming primarily from Rocky Mountain states, have a carbon content of 625kg/MW-hr.

The reliance on hydropower also makes the asymmetry seasonal. Local generation is highest in the spring as snow melts, but imports become a larger source outside this time of year. As solar and wind can also have pronounced seasonal shifts, similar changes will likely be seen as these become larger contributors to many of these regional grids. Similar things occur daily, as both demand and solar production (and, to a lesser extent, wind) have distinct daily profiles.

The Golden State
California's CISO provides another instructive case. Imports represent less than 30% of its total electric use in 2016, yet California electricity imports provided 40% of its embodied emissions. Some of these, however, come internally from California, provided by the Los Angeles Department of Water and Power. The state itself, however, has only had limited tracking of imported emissions, lumping many of its sources as "other," and has been exporting its energy policies to Western states in ways that shape regional markets.

Overall, the 2016 inventory provides a narrow picture of the US grid, as plenty of trends are rapidly changing our country's emissions profile, including the rise of renewables and the widespread adoption of efficiency measures and other utility trends in 2017 that continue to evolve. The method developed here can, however, allow for annual updates, providing us with a much better picture of trends. That could be quite valuable to track things like how the rapid rise in solar power is altering the daily production of clean power.

More significantly, it provides a basis for more informed policymaking. States that wish to promote low-emissions power can use the information here to either alter the source of their imports or to encourage the sites where they're produced to adopt more renewable power. And those states that are exporting electricity produced primarily through fossil fuels could ensure that the locations where the power is used pay a price that includes the health costs of its production.

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