City looks to garbage for renewable power

U.S. Energy Transition traces the shift from coal and oil to natural gas, nuclear power, and renewables like wind and solar, driven by efficiency, grid modernization, climate goals, and economic innovation.

Key Points

The U.S. Energy Transition is the shift from fossil fuels to cleaner power, driven by tech, policy, and markets.

✅ Shift from coal and oil to gas, nuclear, wind, and solar

✅ Enabled by grid modernization, storage, and efficiency

✅ Aims to cut emissions while ensuring reliability and affordability

The evolution of energy use in the United States is a dynamic narrative that reflects technological advancements, economic shifts, environmental awareness, and societal changes over time. From the nation's early reliance on wood and coal to the modern era dominated by oil, natural gas, and renewable sources, the story of energy consumption in the U.S. is a testament to innovation and adaptation.

Early Energy Sources: Wood and Coal

In the early days of U.S. history, energy needs were primarily met through renewable resources such as wood for heating and cooking. As industrialization took hold in the 19th century, coal emerged as a dominant energy source, fueling steam engines and powering factories, railways, and urban growth. The widespread availability of coal spurred economic development and shaped the nation's infrastructure.

The Rise of Petroleum and Natural Gas

The discovery and commercialization of petroleum in the late 19th century transformed the energy landscape once again. Oil quickly became a cornerstone of the U.S. economy, powering transportation, industry, and residential heating, and informing debates about U.S. energy security in policy circles. Concurrently, natural gas emerged as a significant energy source, particularly for heating and electricity generation, as pipelines expanded across the country.

Electricity Revolution

The 20th century witnessed a revolution in electricity generation and consumption, and understanding where electricity comes from helps contextualize how systems evolved. The development of hydroelectric power, spurred by projects like the Hoover Dam and Tennessee Valley Authority, provided clean and renewable energy to millions of Americans. The widespread electrification of rural areas and the proliferation of appliances in homes and businesses transformed daily life and spurred economic growth.

Nuclear Power and Energy Diversification

In the mid-20th century, nuclear power emerged as a promising alternative to fossil fuels, promising abundant energy with minimal greenhouse gas emissions. Despite concerns about safety and waste disposal, nuclear power plants became a significant part of the U.S. energy mix, providing a stable base load of electricity, even as the aging U.S. power grid complicates integration of variable renewables.

Renewable Energy Revolution

In recent decades, the U.S. has seen a growing emphasis on renewable energy sources such as wind, solar, and geothermal power, yet market shocks and high fuel prices alone have not guaranteed a rapid green revolution, prompting broader policy and investment responses. Advances in technology, declining costs, and environmental concerns have driven investments in clean energy infrastructure and policies promoting renewable energy adoption. States like California and Texas lead the nation in wind and solar energy production, demonstrating the feasibility and benefits of transitioning to sustainable energy sources.

Energy Efficiency and Conservation

Alongside shifts in energy sources, improvements in energy efficiency and conservation have played a crucial role in reducing per capita energy consumption and greenhouse gas emissions. Energy-efficient appliances, building codes, and transportation innovations have helped mitigate the environmental impact of energy use while reducing costs for consumers and businesses, and weather and economic factors also influence demand; for example, U.S. power demand fell in 2023 on milder weather, underscoring the interplay between efficiency and usage.

Challenges and Opportunities

Looking ahead, the U.S. faces both challenges and opportunities in its energy future, as recent energy crisis effects ripple across electricity, gas, and EVs alike. Addressing climate change requires further investments in renewable energy, grid modernization, and energy storage technologies. Balancing energy security, affordability, and environmental sustainability remains a complex task that requires collaboration between government, industry, and society.

Conclusion

The evolution of energy use throughout U.S. history reflects a continuous quest for innovation, economic growth, and environmental stewardship. From wood and coal to nuclear power and renewables, each era has brought new challenges and opportunities in meeting the nation's energy needs. As the U.S. transitions towards a cleaner and more sustainable energy future, leveraging technological advancements and embracing policy solutions, amid debates over U.S. energy dominance, will be essential in shaping the next chapter of America's energy story.

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IAEA Nuclear Security Mission in China reviews regulatory frameworks, physical protection, and compliance at nuclear power plants, endorsing CAEA efforts, IPPAS guidance, and capacity building to strengthen safeguards, risk management, and global cooperation.

Key Points

An IAEA advisory visit assessing China's nuclear security, physical protection, and regulatory frameworks.

✅ Reviews laws, regulations, and physical protection measures

✅ Endorses CAEA, COE, and IPPAS-aligned best practices

✅ Recommends accelerated rulemaking for expanding reactors

The International Atomic Energy Agency commended China's efforts and accomplishments in nuclear security after conducting its first nuclear security advisory mission to the nation, according to the China Atomic Energy Authority.

The two-week International Physical Protection Advisory Service mission, from Aug 28to Saturday, reviewed the legislative and regulatory framework for nuclear security as well as the physical protection of nuclear material and facilities, including worker safety protocols during health emergencies.

An eight-member expert team led by Joseph Sandoval of the United States' Sandia National Laboratories visited Fangjiashan Nuclear Power Plant, part of the Qinshan Nuclear Power Station in Zhejiang province, to examine security arrangements and observe physical protection measures, where recognized safety culture practices can reinforce performance.

The experts also met with officials from several Chinese government bodies involved in nuclear security such as the China Atomic Energy Authority, National Nuclear Safety Administration and Ministry of Public Security.

The international agency has carried out 78 of the protection missions in 48 member states since 1995. This was the first in China, it said.

The China Atomic Energy Authority said on Tuesday that a report by the experts highly approves of the Chinese government's continuous efforts to strengthen nuclear safety, to boost the sustainable development of the nuclear power industry and to help establish a global nuclear security system.

The report identifies the positive roles played by the State Nuclear Security Technology Center and its subsidiary, the Center of Excellence on Nuclear Security, in enhancing China's nuclear security capability and supporting regional and global cooperation in the field, such as bilateral cooperation agreements that advance research and standards, officials at the China Atomic Energy Authority said.

"A strong commitment to nuclear security is a must for any state that uses nuclear power for electricity generation and that is planning to significantly expand this capacity by constructing new power reactors," said Muhammad Khaliq, head of the international agency's nuclear security of materials and facilities section. "China'sexample in applying IAEA nuclear security guidance and using IAEA advisory services demonstrates its strong commitment to nuclear security and its enhancement worldwide."

The report notes that along with the rapid growth of China's nuclear power sector, challenges have emerged when it comes to the country's nuclear security mechanism and management, as highlighted by grid reliability warnings during pandemics in other markets.

It suggests that the Chinese government accelerate the making of laws and regulations to better govern this sector.

Deng Ge, director of the State Nuclear Security Technology Center, said the IAEAmission would help China strengthen its nuclear security since the nation could learn from other countries' successful experience, including on-site staffing measures to maintain critical operations, and find out its weaknesses for rectification.

Deng added that the mission's report can help the international community understand China's contributions to the global nuclear security system and also offer China's best practices to other nations.

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FERC Grid Resiliency Pricing Opposition underscores industry groups, RTOs, and ISOs rejecting DOE's NOPR, warning against out-of-market subsidies for coal and nuclear, favoring competitive markets, reliability, and true grid resilience.

Key Points

Coalition urging FERC to reject DOE's NOPR subsidies, protecting reliability and competitive power markets.

✅ Industry groups, RTOs, ISOs oppose DOE NOPR

✅ PJM reports sufficient reliability and resilience

✅ Reject out-of-market aid to coal, nuclear

A diverse group of a dozen energy industry associations representing oil, natural gas, wind, solar, efficiency, and other energy technologies today submitted reply comments to the Federal Energy Regulatory Commission (FERC) continuing their opposition to the Department of Energy's (DOE) proposed rulemaking on grid resiliency pricing and electricity pricing changes within competitive markets, in the next step in this FERC proceeding.

Action by FERC, as lawmakers urge movement on aggregated DERs to modernize markets, is expected by December 11.

In these comments, this broad group of energy industry associations notes that most of the comments submitted initially by an unprecedented volume of filers, including grid operators whose markets would be impacted by the proposed rule, urged FERC not to adopt DOE'sproposed rule to provide out-of-market financial support to uneconomic coal and nuclear power plants in the wholesale electricity markets overseen by FERC.

Just a small set of interests - those that would benefit financially from discriminatory pricing that favors coal and nuclear plants - argued in favor of the rule put forward by DOE in its Notice of Proposed Rulemaking, or NOPR, as did coal and business interests in related regulatory debates. But even those interests - termed 'NOPR Beneficiaries' by the energy associations - failed to provide adequate justification for FERC to approve the rule, and their specific alternative proposals for implementing the bailout of these plants were just as flawed as the DOE plan, according to the energy industry associations.

'The joint comments filed today with partners across the energy spectrum reflect the overwhelming majority view that this proposed rulemaking by FERC is unprecedented and unwarranted, said Todd Foley, Senior Vice President, Policy & Government Affairs, American Council on Renewable Energy.

We're hopeful that FERC will rule against an anti-competitive distortion of the electricity marketplace and avoid new unnecessary initiatives that increase power prices for American consumers and businesses.'

In the new reply comments submitted in response to the initial comments filed by hundreds of stakeholders on or before October 23 - the energy industry associations made the following points: Despite hundreds of comments filed, no new information was brought forth to validate the assertion - by DOE or the NOPR Beneficiaries - that an emergency exists that requires accelerated action to prop up certain power plants that are failing in competitive electricity markets: 'The record in this proceeding, including the initial comments, does not support the discriminatory payments proposed' by DOE, state the industry groups.

Nearly all of the initial comments filed in the matter take issue with the DOE NOPR and its claim of imminent threats to the reliability and resilience of the electric power system, despite reports of coal and nuclear disruptions cited by some advocates: 'Of the hundreds of comments filed in response to the DOE NOPR, only a handful purported to provide substantive evidence in support of the proposal. In contrast, an overwhelming majority of initial comments agree that the DOE NOPR fails to substantiate its assertions of an immediate reliability or resiliency need related to the retirement of merchant coal-fired and nuclear generation.'

Grid operators filed comments refuting claims that the potential retirement of coal and nuclear plants which could not compete for economically present immediate or near-term challenges to grid management, even as a coal CEO criticism targeted federal decisions: 'Even the RTOs and ISOs themselves filed comments opposing the DOE NOPR, noting that the proposed cost-of-service payments to preferred generation would disrupt the competitive markets and are neither warranted nor justified.... Most notably, this includes PJM Interconnection, ... the RTO in which most of the units potentially eligible for payments under the DOE NOPR are located. PJM states that its region 'unquestionably is reliable, and its competitive markets have for years secured commitments from capacity resources that well exceed the target reserve margin established to meet [North American Electric Reliability Corp.] requirements.' And PJM analysis has confirmed that the region's generation portfolio is not only reliable, but also resilient.'

The need for NOPR Beneficiaries to offer alternative proposals reflects the weakness of DOE'srule as drafted, but their options for propping up uneconomic power plants are no better, practically or legally: 'Plans put forward by supporters of the power plant bailout 'acknowledge, at least implicitly, that the preferential payment structure proposed in the DOE NOPR is unclear, unworkable, or both. However, the alternatives offered by the NOPR Beneficiaries, are equally flawed both substantively and procedurally, extending well beyond the scope of the DOE NOPR.'

Citing one example, the energy groups note that the detailed plan put forward by utility FirstEnergy Service Co. would provide preferential payments far more costly than those now provided to individual power plants needed for immediate reasons (and given a 'reliability must run' contract, or RMR): 'Compensation provided under [FirstEnergy's proposal] would be significantly expanded beyond RMR precedent, going so far as to include bailing [a qualifying] unit out of debt based on an unsupported assertion that revenues are needed to ensure long-term operation.'

Calling the action FERC would be required to take in adopting the DOE proposal 'unprecedented,' the energy industry associations reiterate their opposition: 'While the undersigned support the goals of a reliable and resilient grid, adoption of ill-considered discriminatory payments contemplated in the DOE NOPR is not supportable - or even appropriate - from a legal or policy perspective.

About ACORE

The American Council on Renewable Energy (ACORE) is a national non-profit organization leading the transition to a renewable energy economy. With hundreds of member companies from across the spectrum of renewable energy technologies, consumers and investors, ACORE is uniquely positioned to promote the policies and financial structures essential to growth in the renewable energy sector. Our annual forums in Washington, D.C., New York and San Franciscoset the industry standard in providing important venues for key leaders to meet, discuss recent developments, and hear the latest from senior government officials and seasoned experts.

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Pumped Storage Hydroelectricity balances renewable energy, stabilizes the grid, and provides large-scale energy storage using reservoirs and reversible turbines, delivering flexible peak power, frequency control, and rapid response to variable wind and solar generation.

Key Points

A reversible hydro system that stores energy by pumping water uphill, then generates flexible peak power.

✅ Balances variable wind and solar with rapid ramping

✅ Stores off-peak electricity in upper reservoirs

✅ Enhances grid stability, frequency control, and reserves

The expense of hydroelectricity is moderately low, making it a serious wellspring of sustainable power. The hydro station burns-through no water, dissimilar to coal or gas plants. The commonplace expense of power from a hydro station bigger than 10 megawatts is 3 to 5 US pennies for every kilowatt hour, and Niagara Falls powerhouse upgrade projects show how modernization can further improve efficiency and reliability. With a dam and supply it is likewise an adaptable wellspring of power, since the sum delivered by the station can be shifted up or down quickly (as meager as a couple of moments) to adjust to changing energy requests.

When a hydroelectric complex is developed, the task creates no immediate waste, and it for the most part has an extensively lower yield level of ozone harming substances than photovoltaic force plants and positively petroleum product fueled energy plants, with calls to invest in hydropower highlighting these benefits. In open-circle frameworks, unadulterated pumped storage plants store water in an upper repository with no normal inflows, while pump back plants use a blend of pumped storage and regular hydroelectric plants with an upper supply that is renewed to a limited extent by common inflows from a stream or waterway.

Plants that don't utilize pumped capacity are alluded to as ordinary hydroelectric plants, and initiatives focused on repowering existing dams continue to expand clean generation; regular hydroelectric plants that have critical capacity limit might have the option to assume a comparable function in the electrical lattice as pumped capacity by conceding yield until required.

The main use for pumped capacity has customarily been to adjust baseload powerplants, however may likewise be utilized to decrease the fluctuating yield of discontinuous fuel sources, while emerging gravity energy storage concepts broaden long-duration options. Pumped capacity gives a heap now and again of high power yield and low power interest, empowering extra framework top limit.

In specific wards, power costs might be near zero or once in a while negative on events that there is more electrical age accessible than there is load accessible to retain it; despite the fact that at present this is infrequently because of wind or sunlight based force alone, expanded breeze and sun oriented age will improve the probability of such events.

All things considered, pumped capacity will turn out to be particularly significant as an equilibrium for exceptionally huge scope photovoltaic age. Increased long-distance bandwidth, including hydropower imports from Canada, joined with huge measures of energy stockpiling will be a critical piece of directing any enormous scope sending of irregular inexhaustible force sources. The high non-firm inexhaustible power entrance in certain districts supplies 40% of yearly yield, however 60% might be reached before extra capaciy is fundamental.

Pumped capacity plants can work with seawater, despite the fact that there are extra difficulties contrasted with utilizing new water. Initiated in 1966, the 240 MW Rance flowing force station in France can incompletely function as a pumped storage station. At the point when elevated tides happen at off-top hours, the turbines can be utilized to pump more seawater into the repository than the elevated tide would have normally gotten. It is the main enormous scope power plant of its sort.

Alongside energy mechanism, pumped capacity frameworks help control electrical organization recurrence and give save age. Warm plants are substantially less ready to react to abrupt changes in electrical interest, and can see higher thermal PLF during periods of reduced hydro generation, conceivably causing recurrence and voltage precariousness.

Pumped storage plants, as other hydroelectric plants, including new BC generating stations, can react to stack changes in practically no time. Pumped capacity hydroelectricity permits energy from discontinuous sources, (for example, sunlight based, wind) and different renewables, or abundance power from consistent base-load sources, (for example, coal or atomic) to be put something aside for times of more popularity.

The repositories utilized with siphoned capacity are tiny when contrasted with ordinary hydroelectric dams of comparable force limit, and creating periods are regularly not exactly a large portion of a day. This technique produces power to gracefully high top requests by moving water between repositories at various heights.

Now and again of low electrical interest, the abundance age limit is utilized to pump water into the higher store. At the point when the interest gets more noteworthy, water is delivered once more into the lower repository through a turbine. Pumped capacity plans at present give the most monetarily significant methods for enormous scope matrix energy stockpiling and improve the every day limit factor of the age framework. Pumped capacity isn't a fuel source, and shows up as a negative number in postings.

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East-West Transmission Project Ontario connects Thunder Bay to Wawa, facing OEB bidding, Hydro One vs NextBridge, First Nations consultation, environmental assessment, Pukaskwa National Park route, and reliability needs for Northwestern Ontario industry and communities.

Key Points

A 450 km Thunder Bay-Wawa power line proposal facing OEB bidding, Hydro One competition, and First Nations consultation.

✅ Competing bids: Hydro One vs NextBridge under OEB rules

✅ First Nations cite duty to consult and environmental review gaps

✅ Route debate: Pukaskwa Park vs bypass; jobs and reliability at stake

Leaders of six First Nations are urging the Ontario government to "clean up" the bureaucratic process that determines who will build an "urgently needed" high-capacity power transmission line to service northern Ontario.

The proposed 450 kilometre East-West Transmission Project is set to stretch from Thunder Bay to Wawa, providing much-needed electricity to northern Ontario. NextBridge Infrastructure, in partnership with Bamkushwada Limited Partnership (BLP) — an entity the First Nations created in order to become co-owners and active participants in the economic development of the line — have been the main proponents of the project since 2012 and were awarded the right to construct.

In 2018, Hydro One appealed to the previous Liberal government with a proposal to build the transmission line with lower maintenance costs. On Dec. 20, the Ontario Energy Board (OEB) issued a decision that said it will issue the contract to construct the project to the company with the lowest bid, even as a Manitoba Hydro line delay followed a board recommendation in a comparable case.

The transmission regime in Ontario allows competing bids at the beginning of a project to designate a transmitter, and then again at the end of the project to award leave to construct.

As a result, the Hydro One was permitted to submit a competing bid, five years after it was first proposed. The chiefs of the six First Nations say that will delay the project by two years, impede their land and violate their rights. The former Liberal government under which the project was initiated "left the door open" for competition to enter this late in the construction, according to the community leaders.

"The former government created this mess and Hydro One has taken advantage of this loophole," Fort William First Nation Chief Peter Collins said in a Queen's Park news conference on Thursday. "Hydro One is an interloper coming in at the last minute, trying taking over the project and all the hard work that has been done, without doing the work it needs to do."

Mess will explode, says chief

According to Collins, the Ontario Energy Board is likely to choose Hydro One's late submission in February, "causing this mess to explode." The electricity and distribution utility has not completed any of the legal requirements demanded by a project of this magnitude, Collins said, including extensive consultations with First Nations, such as oral traditional evidence hearings that inform regulators, and thorough environment assessments. He speculated that by ignoring these two things, even though in B.C. Ottawa did not oppose a Site C work halt pending a treaty rights challenge, Hydro One's bid will be the lowest cost.

"Hydro One's interference is a big problem," said Collins. He was flanked by the leaders of the Pic Mobert First Nation, Opwaaganasiniing (also known as the Red Rock Indian Band), Michipicoten, Biigtigong Nishnaabeg — or Pic River First Nation — and Pays Plat First Nation.

Collins also highlighted that Hydro One's proposed route for the transmission line will go through Pukaskwa National Park on which there are Aboriginal title claims, and noted that an opponent of the Site C dam has been sharing concerns with northerners, underscoring the need for meaningful engagement. NextBridge's proposal, Collins said, will go around the park.

If Hydro One is awarded the construction project, at risk, too, are as many as 1,000 job opportunities in northern Ontario (including the Ring of Fire) that are expected from NextBridge's proposal, as well as the "many millions" in contracting opportunities for the communities, Collins said.

"That companies such as Hydro One can do this and dissolve all that has been developed by NextBridge and our [partnership] and all the opportunities we have created will signal to ... everyone in Ontario that Ontario's not open for business, at least fair business," Collins said.

Ontario Energy Minister 'disappointed' by OEB's decision

In an email statement to National Observer, Energy Minister Greg Rickford's press secretary said the government acknowledged the concerns of the First Nations leaders, and is "disappointed that the OEB continues to stall on this important project."

"The East-West Tie project is a priority for Ontario because it is needed to provide a reliable and adequate supply of electricity to northwestern Ontario to support economic growth," she wrote.

In October, Rickford wrote to the OEB outlining his expectation that a prompt decision would be made through an efficient and fair process.

Despite the minister’s request, the OEB delayed a decision on this project in December — as in B.C., a utilities watchdog has pressed for answers on Site C dam stability — pushing the service date back to at least 2021. In 2017, NextBridge said that, pending OEB approval, it would start construction in 2018, with completion scheduled for 2020.

Without the transmission line, the community faces a higher likelihood of power outages and less reliable electricity overall.

"Our government takes the duty to consult seriously and it is committed to ensuring that all Indigenous communities are properly consulted and kept informed regardless of the result of the OEB process," Rickford's office's statement said.

In a letter sent to Premier Doug Ford, Rickford and to Environment Minister Rod Phillips, all members of the Bamkushwada Limited Partnership said they will be compelled to appeal the OEB's decision if the right to construct is given to Hydro One.

The entire situation, they wrote in their letter, is "an undeniable mess" that requires government intervention.

"If the Ontario government can correct this looming outcome, it is incumbent on the Ontario government to do so," they wrote, urging the government to "take all legal means to prevent the OEB from rendering an unconstitutional and unjust decision."

"Our First Nations and the north have waited five long years for this transmission project," Collins said. "Enough is enough."

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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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