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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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Idaho Power Valmy Settlement outlines early closure of the North Valmy coal-fired plant in Nevada, accelerated depreciation recovery, a 1.17% base-rate increase, and impacts for customers, NV Energy co-ownership, and Idaho Public Utilities Commission review.

Key Points

A proposed agreement to close North Valmy early, recover costs via a 1.17% rate hike, and seek PUC approval.

✅ Unit 1 closes 2019; Unit 2 closes 2025 in Nevada.

✅ 1.17% base-rate hike; about $1.20 per 1,000 kWh monthly bill.

✅ Idaho PUC comment deadline May 25; NV Energy co-owner.

State regulators have set a May 25 deadline for public comment on a proposed settlement related to the early closure of a coal-fired plant co-owned by Idaho Power, even as some utilities plan to keep a U.S. coal plant running indefinitely in other jurisdictions.

The settlement calls for shuttering Unit 1 of the North Valmy Power Plant in Nevada in 2019, with Unit 2 closing in 2025, amid regional coal unit retirements debates. The units had been slated for closure in 2031 and 2035, respectively.

If approved by the Idaho Public Utilities Commission, the settlement would increase base rates by approximately $13.3 million, or 1.17 percent, in order to allow the company to recover its investment in the plant on an accelerated basis.

That equates to an additional $1.20 on the monthly bill of the typical residential customer using 1,000 kilowatt-hours of energy per month.

Idaho Power, which co-owns the plant with NV Energy, maintains that closing Valmy early rather than continuing to operate it until it is fully depreciated in 2035, will ultimately save customers $103 million in today's dollars.

The company said a significant decrease in market prices for electricity has made it uneconomic to operate the plant except during extremely cold or hot weather, when the demand for energy peaks, a trend underscored by transactions involving the San Juan Generating Station deal elsewhere. The company also said plant balances have increased by approximately $70 million since its last general rate case in 2011, due to routine maintenance and repairs, as well as investments required to meet environmental regulations.

The proposed settlement reflects a number of changes to Idaho Power's original proposal regarding Valmy, and comes in the wake of discussions with interested parties in February and April, against the backdrop of a broader energy debate over plant closures and reliability.

In its initial application, filed in October, Idaho Power proposed closing both units in 2025. The original proposal would have increased base rates by $28.5 million, or about 2.5 percent, in order to allow the company to recover its costs associated with the plant's accelerated depreciation, decommissioning and anticipated investments, with cautionary examples such as the Kemper power plant costs illustrating potential risks.

Concurrently, Idaho Power asked for commission approval to adjust depreciation rates for its other plants and equipment based on the result of a study it conducts every five years, as outlined in Case IPC-E-16-23. The adjustment would have led to a $6.7 million increase to base rates.

The two requests filed in October would have increased customer costs by a total of $35.2 million or 3.1 percent, leading to a $3.08 increase on the bills of the typical residential customer who uses 1,000 kilowatt-hours per month.

The proposed settlement submitted to the Commission on May 4 calls for $13,285,285 to be recovered from all customer classes through base rates until 2028, all related to the Valmy shutdown. That is an increase of 1.17 percent and would result in a $1.20 increase on the bills of the typical residential customer who uses 1,000 kilowatt-hours per month.

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Ontario Utility Scam Alert: protect against phishing, spoofed calls, texts, and emails, disconnection threats, and demands for prepaid cards or bitcoin. Tips from Alectra, Elexicon, Hydro One, Hydro Ottawa, and Toronto Hydro.

Key Points

A joint warning by Ontario utilities on tactics and steps to prevent customer fraud, phishing, and spoofed contacts.

✅ Verify bills; call your utility using the official number.

✅ Ignore links; do not accept unexpected e-transfers.

✅ Never pay with gift cards, prepaid cards, or bitcoin.

Five of Ontario's largest utilities have joined forces to raise awareness about ongoing sophisticated utility scams targeting utility customers.

Some common tactics fraudsters use to target Ontarians include impersonation of the local utility or its employees; sending threatening phone calls, texts and emails; or showing up in-person at a customer's home or business and requesting personal information or payment. The requests can include pressure for immediate payment, threats to disconnect service the same day, and demands to purchase prepaid debit cards, gift cards or bitcoin.

The utilities are encouraging all customers to protect themselves and are providing them with the following tips to stay safe, noting that customers want more choice and flexibility in how they manage accounts:

• Never make a payment for a charge that isn't listed on your most recent bill
• Ignore text messages or emails with suspicious links promising refunds
• Don't call the number provided to you — instead, call your utility directly to check the status of your account
• Only provide personal information or details about your account when you have initiated the contact with the utility representative  
• Utility companies will never threaten immediate disconnection for non-payment, and many offer relief programs during hardship
• If you feel threatened in any way, contact your local police
• Steps you can take to protect yourself against fraud:

Take five minutes to ask additional questions and listen to your instincts — if something doesn't seem right, ask someone about it, and look for news of official utility support efforts that confirm legitimate outreach

• Immediately hang up on suspicious phone calls
• Don't click any links in emails/text messages asking you to accept electronic transfers
• Avoid sharing personal information
• Always compare bills to previous ones, including the dollar amount and account number, and stay informed about any official rate changes from your utility
• Reporting suspicious behaviour, including suspected electricity theft, helps authorities

If you believe you may be a victim of fraud, please contact the Canadian Anti-Fraud Centre at 1-888-495-8501 and your local utility.

Customers can find more information at:

• Alectra Utilities
• Elexicon Energy
• Hydro One
• Hydro Ottawa 
• Toronto Hydro

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ABO Wind Tunisia 10MW Solar Project will build a photovoltaic park in Gabes with a STEG PPA, fixed tariff, 2,500 m grid connection, producing 18 million kWh annually, targeted for 2020 commissioning with local partners.

Key Points

A 10MW photovoltaic park in Gabes with a 20-year STEG PPA and fixed tariff, slated for 2020 commissioning.

✅ 18 million kWh/year; 2,500 m grid tie, 20-year fixed tariff

✅ Electricity supplied to STEG under PPA; 2020 commissioning

✅ Located in Gabes; built with local partners, 10MW capacity

ABO Wind has received a permit and a tariff for a 10MW photovoltaic project in Tunisia, amid global activity such as Spain's 90MW wind project now underway, which it plans to build and commission in 2020.

The solar park, in the governorate of Gabes, is 400km south of the country’s capital Tunis and aligns with renewable funding initiatives seen across developing markets.

The developer said it plans to build the project next year in close cooperation with local partners, as regional markets from North Africa to the Gulf expand, with Saudi Arabia boosting wind capacity as well.

ABO Wind department head Nicolas Konig said: “The solar park will produce more than 18 million kilowatt hours of electricity per year and will feed it into the grid at a distance of 2500 metres.”

The developer will conclude an electricity supply contract with the state-owned energy supplier (Societe tunisienne de l’electricite et du gaz (STEG), which will provide a fixed remuneration over 20 years, a model echoed by Germany's wind-solar tender for the electricity fed into the grid.

Earlier this year, ABO Wind had already secured a tariff for a wind farm with a capacity of 30MW in a tender, 35km south-east of Tunis, underscoring Tunisia's wind investments under its long-term plan.

The company is working on half a dozen Tunisian wind and solar projects, as institutions like the World Bank support wind growth in developing countries.

“We are making good progress on our way to assemble a portfolio of several ready-to-build wind and solar projects attractive to investors, as Saudi clean energy targets continue to expand globally,” said ABO Wind general manager responsible for international business development Patrik Fischer.

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Great Northern Transmission Line delivers 250 MW of carbon-free hydropower from Manitoba Hydro, strengthening Midwest grid reliability, enabling wind storage balancing, and advancing Minnesota Power's EnergyForward strategy for cleaner, renewable energy across the region.

Key Points

A 500 kV cross-border line delivering 250 MW of carbon-free hydropower, strengthening reliability and enabling renewables.

✅ 500 kV, 224-mile line from Manitoba to Minnesota

✅ Delivers 250 MW hydropower via ALLETE-Minnesota Power

✅ Enables wind storage and grid balancing with Manitoba Hydro

Minnesota Power, a utility division of ALLETE Inc. (NYSE:ALE), has energized its Great Northern Transmission Line, bringing online an innovative delivery and storage system for renewable energy that spans two states and one Canadian province, similar to the Maritime Link project in Atlantic Canada.

The 500 kV line is now delivering 250 megawatts of carbon-free hydropower from Manitoba, Canada, to Minnesota Power customers.

Minnesota Power completed the Great Northern Transmission Line (GNTL) in February 2020, ahead of schedule and under budget. The 224-mile line runs from the Canadian border in Roseau County to a substation near Grand Rapids, Minnesota. It consists of 800 tower structures which were fabricated in the United States and used 10,000 tons of North American steel. About 2,200 miles of wire were required to install the line's conductors. The GNTL also is contributing significant property tax revenue to local communities along the route.

"This is such an incredible achievement for Minnesota Power, ALLETE, and our region, and is the culmination of a decade-long vision brought to life by our talented and dedicated employees," said ALLETE President and CEO Bethany Owen. "The GNTL will help Minnesota Power to provide our customers with 50 percent renewable energy less than a year from now. As part of our EnergyForward strategy, it also strengthens the grid across the Midwest and in Canada, enhancing reliability for all of our customers."

With the GNTL energized and connected to Manitoba Hydro's recently completed Manitoba-Minnesota Transmission Project at the border, the companies now have a unique "wind storage" mechanism that quickly balances energy supply and demand in Minnesota and Manitoba, and enables a larger role for renewables in the North American energy grid.

The GNTL and its delivery of carbon-free hydropower are important components of Minnesota Power's EnergyForward strategy to transition away from coal and add renewable power sources while maintaining reliable and affordable service for customers, echoing interties like the Maritime Link that facilitate regional power flows. It also is part of a broader ALLETE strategy to advance and invest in critical regional transmission and distribution infrastructure, such as the TransWest Express transmission project, to ensure grid integrity and enable cleaner energy to reduce carbon emissions.

"The seed for this renewable energy initiative was planted in 2008 when Minnesota Power proposed purchasing 250 megawatts of hydropower from Manitoba Hydro. Beyond the transmission line, it also included a creative asset swap to move wind power from North Dakota to Minnesota, innovative power purchase agreements, and a remarkable advocacy process to find an acceptable route for the GNTL," said ALLETE Executive Chairman Al Hodnik. "It marries wind and water in a unique connection that will help transform the energy landscape of North America and reduce carbon emissions related to the existential threat of climate change."

Minnesota Power and Manitoba Hydro, a provincial Crown Corporation, coordinated on the project from the beginning, navigating National Energy Board reviews along the way. It is based on the companies' shared values of integrity, environmental stewardship and community engagement.

"The completion of Minnesota Power's Great Northern Transmission Line and our Manitoba-Minnesota Transmission Project is a testament to the creativity, perseverance, cooperation and skills of hundreds of people over so many years on both sides of the border," said Jay Grewal, president and CEO of Manitoba Hydro. "Perhaps even more importantly, it is a testament to the wonderful, longstanding relationship between our two companies and two countries. It shows just how much we can accomplish when we all work together toward a common goal."

Minnesota Power engaged federal, state and local agencies; the sovereign Red Lake Nation and other tribes, reflecting First Nations involvement in major transmission planning; and landowners along the proposed routes beginning in 2012. Through 75 voluntary meetings and other outreach forums, a preferred route was selected with strong support from stakeholders that was approved by the Minnesota Public Utilities Commission in April 2016.

A four-year state and federal regulatory process culminated in late 2016 when the federal Department of Energy approved a Presidential Permit for the GNTL, similar to the New England Clean Power Link process, needed because of the international border crossing. Construction of the line began in early 2017.

"A robust stakeholder process is essential to the success of any project, but especially when building a project of this scope," Owen said. "We appreciated the early engagement and support from stakeholders, local communities and tribes, agencies and regulators through the many approval milestones to the completion of the GNTL."

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U.S. Electricity Trade by State, 2013-2017 highlights EIA grid patterns, interstate imports and exports, cross-border flows with Canada and Mexico, net exporters and importers, and market regions like ISOs and RTOs shaping consumption and generation.

Key Points

Brief EIA overview of interstate and cross-border power flows, ranking top net importers and exporters.

✅ Pennsylvania was the largest net exporter, averaging 59 million MWh.

✅ California was the largest net importer, averaging 77 million MWh.

✅ Top cross-border: NY, CA, VT, MN, MI imports; WA, TX, CA, NY, MT exports.

According to the U.S. Energy Information Administration (EIA) State Electricity Profiles, from 2013 to 2017, Pennsylvania was the largest net exporter of electricity, while California was the largest net importer.

Pennsylvania exported an annual average of 59 million megawatt-hours (MWh), while California imported an average of 77 million MWh annually.

Based on the share of total consumption in each state, the District of Columbia, Maryland, Massachusetts, Idaho and Delaware were the five largest power-importing states between 2013 and 2017, highlighting how some clean states import 'dirty' electricity as consumption outpaces local generation. Wyoming, West Virginia, North Dakota, Montana and New Hampshire were the five largest power-exporting states. Wyoming and West Virginia were net power exporting states between 2013 and 2017.

New York, California, Vermont, Minnesota and Michigan imported the most electricity from Canada or Mexico on average from 2013 to 2017, reflecting the U.S. look to Canada for green power during that period. Similarly, Washington, Texas, California, New York, and Montana exported the most electricity to Canada or Mexico, on average, during the same period.

Electricity routinely flows among the Lower 48 states and, to a lesser extent, between the United States and Canada and Mexico. From 2013 to 2017, Pennsylvania was the largest net exporter of electricity, sending an annual average of 59 million megawatthours (MWh) outside the state. California was the largest net importer, receiving an average of 77 million MWh annually.

Based on the share of total consumption within each state, the District of Columbia, Maryland, Massachusetts, Idaho, and Delaware were the five largest power-importing states between 2013 and 2017. Wyoming, West Virginia, North Dakota, Montana, and New Hampshire were the five largest power-exporting states. States with major population centers and relatively less generating capacity within their state boundaries tend to have higher ratios of net electricity imports to total electricity consumption, as utilities devote more to electricity delivery than to power production in many markets.

Wyoming and West Virginia were net power exporting states (they exported more power to other states than they consumed) between 2013 and 2017. Customers residing in these two states are not necessarily at an economic disadvantage or advantage compared with customers in neighboring states when considering their electricity bills and fees and market dynamics. However, large amounts of power trading may affect a state’s revenue derived from power generation.

Some states also import and export electricity outside the United States to Canada or Mexico, even as Canada's electricity exports face trade tensions today. New York, California, Vermont, Minnesota, and Michigan are the five states that imported the most electricity from Canada or Mexico on average from 2013 through 2017. Similarly, Washington, Texas (where electricity production and consumption lead the nation), California, New York, and Montana are the five states that exported the most electricity to Canada or Mexico, on average, for the same period.

Many states within the continental United States fall within integrated market regions, referred to as independent system operators or regional transmission organizations. These integrated market regions allow electricity to flow freely between states or parts of states within their boundaries.

EIA’s State Electricity Profiles provide details about the supply and disposition of electricity for each state, including net trade with other states and international imports and exports, and help you understand where your electricity comes from more clearly.

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