Bangladesh evaluates coal-fired plants

Hurricane Ida New Orleans Infrastructure faced a split outcome: levees and pumps protected against storm surge, while the power grid collapsed as transmission lines failed, prompting large-scale restoration efforts across Louisiana and Mississippi.

Key Points

It summarizes Ida's impact: levees and pumps held, but the power grid failed, causing outages and slow restoration.

✅ Levees and pumps mitigated flooding and storm surge impacts.

✅ All transmission lines failed, crippling the power grid.

✅ Crews and drones assess damage; restoration may take weeks.

Infrastructure in the city of New Orleans turned in a mixed performance against the fury of Hurricane Ida, with the levees and pumps warding off catastrophic flooding even as the electrical grid, part of the broader Louisiana power grid, failed spectacularly.

Ida’s high winds, measuring 150 miles (240 kilometers) an hour at landfall, took out all eight transmissions lines that deliver power into New Orleans, ripped power poles in half and crumpled at least one steel transmission tower into a twisted metal heap, knocking out electricity to all of the city. A total of more than 1.2 million homes and businesses in Louisiana and Mississippi lost power. While about 90,000 customers were reconnected by Monday afternoon, many could face days without electricity, and frustration can mount as seen during the Houston outage after major storms.

In contrast, the New Orleans area’s elaborate flood defenses seem to have held up, a vindication of the Army Corps of Engineers’ $14.5 billion project to rebuild levees, flood gates and pumps in the wake of the devastation wrought by Hurricane Katrina in 2005. While there were reports of scattered deaths tied to Ida, the city escaped the kind of flooding that destroyed entire neighborhoods in Katrina’s wake, left parts of the city uninhabitable for months and claimed 1,800 lives. 

“The situation in New Orleans, as bad as it is today with the power, could be so much worse,” Louisiana Governor John Bel Edwards said Monday on the Today Show, praising the levee system’s performance. “All you have to do is go back 16 years to get a glimpse of what that would have been like.”

While the levees’ resiliency is no doubt due to the rebuilding effort that followed Katrina, the starkly different outcomes also stems from the storms’ different characteristics. Katrina slammed the coast with a 30-foot storm surge of ocean water, while preliminary estimates from Ida put its surge far lower. 

Ida’s winds, however, were stronger than Katrina’s, and that’s what ultimately took out so many power lines, a dynamic that also saw Texas utilities struggle during Harvey. Deanna Rodriguez, the chief executive officer of power provider Entergy New Orleans, declined to comment on when service would be restored, saying the company was using helicopters and drones to help assess the damage.

Michael Webber, an energy and engineering professor at the University of Texas at Austin, estimated power restoration will take days and possibly weeks, a pattern seen in Florida restoration timelines after major hurricanes, based on the initial damage reports from the storm. More than 25,000 workers from at least 32 states and Washington are mobilized to assist with power restoration efforts, similar to FPL's massive response after Irma, according to the Edison Electric Institute.

“The question is, how long will it take to rebuild these lines,” Webber said. The utilities will first need to complete their damage assessments before they can get a sense of repair timelines, a step that Gulf Power crews have highlighted in past recoveries, he said. “You can imagine that will take days at least, possibly weeks.”

The loss of electricity will have other affects as well, and even though grid resilience during the pandemic was strong, local systems face immediate constraints. Sewer substations, for example, need electricity to keep wastewater moving, said Ghassan Korban, executive director of the New Orleans Sewerage & Water Board. The storm knocked out power to about 80 of the city’s 84 pumping stations, he said at a Monday press conference. “Without electricity, wastewater backs up and can cause overflows,” he said, adding that residents should conserve water to lessen stress on the system.

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Texas Electricity Prices are shifting as deregulation matures, with competitive market shopping lowering residential rates, narrowing gaps with regulated areas, and EIA data showing long term declines versus national averages across most Texans.

Key Points

Texas Electricity Prices are average residential rates in deregulated and regulated markets across the state.

✅ Deregulated areas saw 17.4% residential price declines since 2006

✅ Regulated zones experienced a 5.5% increase over the same period

✅ Competitive shopping narrowed the gap; Texas averaged below US

Shopping for electricity is becoming cheaper for most Texans, according to a new study from the Texas Coalition for Affordable Power. But for those who live in an area with only one electricity provider, prices have increased in a recent 10-year period, the study says.

About 85 percent of Texans can purchase electricity from a number of providers in a deregulated marketplace, while the remaining 15 percent must buy power from a single provider, often an electric cooperative, in their area.

The report from the Texas Coalition for Affordable Power, which advocates for cities and local governments and negotiates their power contracts, pulls information from the U.S. Energy Information Administration to compare prices for Texans in the two models. Most Texans could begin choosing their electricity provider in 2002.

Buying power tends to be more expensive for Texans who live in a part of the state with a deregulated electricity market. But that gap is continuing to shrink as Texans become more willing to shop for power, even as electricity complaints have periodically risen. In 2015, the gap “was the smallest since the beginning of deregulation,” according to the report.

Between 2006 and 2015, the last year for which data is available, average residential electric prices for Texans in a competitive market decreased by 17.4 percent, while average prices increased by 5.5 percent in the regulated areas, even as the Texas power grid has periodically faced stress.

“These residential price declines are promising, and show the retail electric market is maturing,” Jay Doegey, executive director for the Texas Coalition for Affordable Power, said in a statement. “We’re encouraged by the price declines, but more progress is needed.”

The study attributes the decline to the prevalence of “low-priced individual deals” in the competitive areas, while policymakers consider market reforms to bolster reliability.

Overall, the average price of electricity in Texas (which produces and consumes the most electricity in the U.S.) — including the price in the deregulated marketplace, for the third time in four years — was below the national average in 2015.

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UK EV Per-Mile Taxes are reshaping road pricing and vehicle taxation for electric cars, raising fairness concerns, climate policy questions, and funding needs for infrastructure and charging networks across the country.

Key Points

They are per-mile road charges on EVs to fund infrastructure, raising fairness, emissions, and vehicle taxation concerns.

✅ Propose tax relief or credits for EV owners

✅ Consider emission-based road user charging

✅ Invest in charging networks and road infrastructure

As the UK continues its push towards a greener future with increased adoption of electric vehicles (EVs) and surging EV interest during supply disruptions, a growing number of electric car drivers are voicing their frustration over the current tax system. The debate centers around the per-mile vehicle taxes that are being proposed and implemented, which many argue are unfairly burdensome on EV owners. This issue has sparked a broader campaign advocating for a more equitable approach to vehicle taxation, one that reflects the evolving landscape of transportation and environmental policy.

Rising Costs for Electric Car Owners

Electric vehicles have been hailed as a crucial component in the UK’s strategy to reduce carbon emissions and combat climate change. Government incentives, such as grants for EV purchases and tax breaks, have been instrumental in encouraging the shift from petrol and diesel cars to cleaner alternatives, even as affordability concerns persist among many UK consumers. However, as the number of electric vehicles on the road grows, the financial dynamics of vehicle taxation are coming under scrutiny.

One of the key issues is the introduction and increase of per-mile vehicle taxes. While these taxes are designed to account for road usage and infrastructure costs, they have been met with resistance from EV drivers who argue that they are being disproportionately affected. Unlike traditional combustion engine vehicles, electric cars typically have lower running costs compared to petrol or diesel models and, in many cases, benefit from lower or zero emissions. Yet, the current tax system does not always reflect these advantages.

The Taxation Debate

The crux of the debate lies in how vehicle taxes are structured and implemented. Per-mile taxes are intended to ensure that all road users contribute fairly to the maintenance of transport infrastructure. However, the implementation of such taxes has raised concerns about fairness and affordability, particularly for those who have invested heavily in electric vehicles.

Critics argue that per-mile taxes do not adequately take into account the environmental benefits of driving an electric car, noting that the net impact depends on the electricity generation mix in each market. While EV owners are contributing to a cleaner environment by reducing emissions, they are also facing higher taxes that could undermine the financial benefits of their greener choice. This has led to calls for a reassessment of the tax system to ensure that it aligns with the UK’s climate goals and provides a fair deal for electric vehicle drivers.

Campaigns for Fairer Taxation

In response to these concerns, several advocacy groups and individual EV owners have launched campaigns calling for a more balanced approach to vehicle taxation. These campaigns emphasize the need for a system that supports the transition to electric vehicles and recognizes their role in reducing environmental impact, drawing on ambitious EV targets abroad as useful benchmarks.

Key proposals from these campaigns include:

1. Tax Relief for EV Owners: Advocates suggest providing targeted tax relief for electric vehicle owners to offset the costs of per-mile taxes. This could include subsidies or tax credits that acknowledge the environmental benefits of EVs and help to make up for higher road usage fees.

2. Emission-Based Taxation: An alternative approach is to design vehicle taxes based on emissions rather than mileage. This system would ensure that those driving high-emission vehicles contribute more to road maintenance, while EV owners, who are already reducing emissions, are not penalized.

3. Infrastructure Investments: Campaigners also call for increased investments in infrastructure that supports electric vehicles, such as charging networks and proper grid management practices that balance load. This would help to address concerns about the adequacy of current road maintenance and support the growing number of EVs on the road.

Government Response and Future Directions

The UK government faces the challenge of balancing revenue needs with environmental goals. While there is recognition of the need to update the tax system in light of increasing EV adoption, there is also a focus on ensuring that any changes are equitable and do not disincentivize the shift towards cleaner vehicles, while considering whether the UK grid can handle additional EV demand reliably.

Discussions are ongoing about how to best implement changes that address the concerns of electric vehicle owners while ensuring that the transportation infrastructure remains adequately funded. The outcome of these discussions will be critical in shaping the future of vehicle taxation in the UK and supporting the country’s broader environmental objectives.

Conclusion

As electric vehicle adoption continues to rise in the UK, the debate over vehicle taxation becomes increasingly important. The campaign for fairer per-mile taxes highlights the need for a tax system that supports the transition to cleaner transportation while also being fair to those who have made environmentally conscious choices. Balancing these factors will be key to achieving the UK’s climate goals and ensuring that all road users contribute equitably to the maintenance of transport infrastructure. The ongoing dialogue and policy adjustments will play a crucial role in shaping a sustainable and just future for transportation in the UK.

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UK low-carbon electricity 2019 saw stalled growth as renewables rose slightly, wind expanded, nuclear output fell, coal hit record lows, and net-zero targets demand faster deployment to cut CO2 intensity below 100gCO2/kWh.

Key Points

Low-carbon sources supplied 54% of UK power in 2019, up just 1TWh; wind grew, nuclear fell, and coal dropped to 2%.

✅ Wind up 8TWh; nuclear down 9TWh amid outages

✅ Fossil fuels 43% of generation; coal at 2%

✅ Net-zero needs 15TWh per year added to 2030

The amount of electricity generated by low-carbon sources in the UK stalled in 2019, Carbon Brief analysis shows.

Low-carbon electricity output from wind, solar, nuclear, hydro and biomass rose by just 1 terawatt hour (TWh, less than 1%) in 2019. It represents the smallest annual increase in a decade, where annual growth averaged 9TWh. This growth will need to double in the 2020s to meet UK climate targets while replacing old nuclear plants as they retire.

Some 54% of UK electricity generation in 2019 came from low-carbon sources, including 37% from renewables and 20% from wind alone, underscoring wind's leading role in the power mix during key periods. A record-low 43% was from fossil fuels, with 41% from gas and just 2% from coal, also a record low. In 2010, fossil fuels generated 75% of the total.

Carbon Brief’s analysis of UK electricity generation in 2019 is based on figures from BM Reports and the Department for Business, Energy and Industrial Strategy (BEIS). See the methodology at the end for more on how the analysis was conducted.

The numbers differ from those published earlier in January by National Grid, which were for electricity supplied in Great Britain only (England, Wales and Scotland, but excluding Northern Ireland), including via imports from other countries.

Low-carbon low
In 2019, the UK became the first major economy to target net-zero greenhouse gas emissions by 2050, increasing the ambition of its legally binding Climate Change Act.

To date, the country has cut its emissions by around two-fifths since 1990, with almost all of its recent progress coming from the electricity sector.

Emissions from electricity generation have fallen rapidly in the decade since 2010 as coal power has been almost phased out and even gas output has declined. Fossil fuels have been displaced by falling demand and by renewables, such as wind, solar and biomass.

But Carbon Brief’s annual analysis of UK electricity generation shows progress stalled in 2019, with the output from low-carbon sources barely increasing compared to a year earlier.

The chart below shows low-carbon generation in each year since 2010 (grey bars) and the estimated level in 2019 (red). The pale grey bars show the estimated future output of existing low-carbon sources after old nuclear plants retire and the pale red bars show the amount of new generation needed to keep electricity sector emissions to less than 100 grammes of CO2 per kilowatt hour (gCO2/kWh), the UK’s nominal target for the sector.

 Annual electricity generation in the UK by fuel, terawatt hours, 2010-2019. Top panel: fuel by fuel. Bottom panel: cumulative total generation from all sources. Source: BEIS energy trends, BM Reports and Carbon Brief analysis. Chart by Carbon Brief using Highcharts.
As the chart shows, the UK will require significantly more low-carbon electricity over the next decade as part of meeting its legally binding climate goals.

The nominal 100gCO2/kWh target for 2030 was set in the context of the UK’s less ambitious goal of cutting emissions to 80% below 1990 levels by 2050. Now that the country is aiming to cut emissions to net-zero by 2050, that 100gCO2/kWh indicator is likely to be the bare minimum.

Even so, it would require a rapid step up in the pace of low-carbon expansion, compared to the increases seen over the past decade. On average, low-carbon generation has risen by 9TWh each year in the decade since 2010 – including a rise of just 1TWh in 2019.

Given scheduled nuclear retirements and rising demand expected by the Committee on Climate Change (CCC) – with some electrification of transport and heating – low-carbon generation would need to increase by 15TWh each year until 2030, just to meet the benchmark of 100gCO2/kWh.

For context, the 3.2 gigawatt (GW) Hinkley C new nuclear plant being built in Somerset will generate around 25TWh once completed around 2026. The world’s largest offshore windfarm, the 1.2GW Hornsea One scheme off the Yorkshire coast, will generate around 5TWh each year.

The new Conservative government is targeting 40GW of offshore wind by 2030, up from today’s figure of around 8GW. If policies are put in place to meet this goal, then it could keep power sector emissions below 100gCO2/kWh, depending on the actual performance of the windfarms built.

However, new onshore wind and solar, further new nuclear or other low-carbon generation, such as gas with carbon capture and storage (CCS), is likely to be needed if demand is higher than expected, or if the 100gCO2/kWh benchmark is too weak in the context of net-zero by 2050.

The CCC says it is “likely” to “reflect the need for more rapid deployment” of low-carbon towards net-zero emissions in its advice on the sixth UK carbon budget for 2033-2037, due in September.

Trading places
Looking more closely at UK electricity generation in 2019, Carbon Brief’s analysis shows why there was so little growth for low-carbon sources compared to the previous year.

There was another increase for wind power in 2019 (up 8TWh, 14%), with record wind generation as several large new windfarms were completed including the 1.2GW Hornsea One project in October and the 0.6GW Beatrice offshore windfarm in Q2 of 2019. But this was offset by a decline for nuclear (down 9TWh, 14%), due to ongoing outages for reactors at Hunterston in Scotland and Dungeness in Kent.

(Analysis of data held by trade organisation RenewableUK suggests some 0.6GW of onshore wind capacity also started operating in 2019, including the 0.2GW Dorenell scheme in Moray, Scotland.)

As a result of these movements, the UK’s windfarms overtook nuclear for the first time ever in 2019, becoming the country’s second-largest source of electricity generation, and earlier, wind and solar together surpassed nuclear in the UK as momentum built. This is shown in the figure below, with wind (green line, top panel) trading places with nuclear (purple) and gas (dark blue) down around 25% since 2010 but remaining the single-largest source.

 Annual electricity generation in the UK by fuel, terawatt hours, 2010-2019. Top panel: fuel by fuel. Bottom panel: cumulative total generation from all sources. Source: BEIS energy trends, BM Reports and Carbon Brief analysis. Chart by Carbon Brief using Highcharts.
The UK’s currently suspended nuclear plants are due to return to service in January and March, according to operator EDF, the French state-backed utility firm. However, as noted above, most of the UK’s nuclear fleet is set to retire during the 2020s, with only Sizewell B in Suffolk due to still be operating by 2030. Hunterston is scheduled to retire by 2023 and Dungeness by 2028.

Set against these losses, the UK has a pipeline of offshore windfarms, secured via “contracts for difference” with the government, at a series of auctions. The most recent auction, in September 2019, saw prices below £40 per megawatt hour – similar to current wholesale electricity prices.

However, the capacity contracted so far is not sufficient to meet the government’s target of 40GW by 2030, meaning further auctions – or some other policy mechanism – will be required.

Coal zero
As well as the switch between wind and nuclear, 2019 also saw coal fall below solar for the first time across a full year, echoing the 2016 moment when wind outgenerated coal across the UK, after it suffered another 60% reduction in electricity output. Just six coal plants remain in the UK, with Aberthaw B in Wales and Fiddlers Ferry in Cheshire closing in March.

Coal accounted for just 2% of UK generation in 2019, a record-low coal share since centralised electricity supplies started to operate in 1882. The fuel met 40% of UK needs as recently as 2012, but has plummeted thanks to falling demand, rising renewables, cheaper gas and higher CO2 prices.

The reduction in average coal generation hides the fact that the fuel is now often not required at all to meet the UK’s electricity needs. The chart below shows the number of days each year when coal output was zero in 2019 (red line) and the two previous years (blue).

 Cumulative number of days when UK electricity generation from renewable sources has been higher than that from fossil fuels. Source: BEIS energy trends, BM Reports and Carbon Brief analysis. Chart by Carbon Brief using Highcharts.
The 83 days in 2019 with zero coal generation amount to nearly a quarter of the year and include the record-breaking 18-day stretch without the fuel.

Great Britain has been running for a record TWO WEEKS without using coal to generate electricity – the first time this has happened since 1882.

The country’s grid has been coal-free for 45% of hours in 2019 so far.https://www.carbonbrief.org/countdown-to-2025-tracking-the-uk-coal-phase-out …

Coal generation was set for significant reductions around the world in 2019 – including a 20% reduction for the EU as a whole – according to analysis published by Carbon Brief in November.

Notably, overall UK electricity generation fell by another 9TWh in 2019 (3%), bringing the total decline to 58TWh since 2010. This is equivalent to more than twice the output from the Hinkley C scheme being built in Somerset. As Carbon Brief explained last year, falling demand has had a similar impact on electricity-sector CO2 emissions as the increase in output from renewables.

This is illustrated by the fact that the 9TWh reduction in overall generation translated into a 9TWh (6%) cut in fossil-fuel generation during 2019, with coal falling by 10TWh and gas rising marginally.

Increasingly renewable
As fossil-fuel output and overall generation have declined, the UK’s renewable sources of electricity have continued to increase. Their output has risen nearly five-fold in the past decade and their share of the UK total has increased from 7% in 2010 to 37% in 2019.

As a result, the UK’s increasingly renewable grid is seeing more minutes, hours and days during which the likes of wind, solar and biomass collectively outpace all fossil fuels put together, and on some days wind is the main source as well.

The chart below shows the number of days during each year when renewables generated more electricity than fossil fuels in 2019 (red line) and each of the previous four years (blue lines). In total, nearly two-fifths of days in 2019 crossed this threshold.

 Cumulative number of days when the UK has not generated any electricity from coal. Source: BEIS energy trends, BM Reports and Carbon Brief analysis. Chart by Carbon Brief using Highcharts.
There were also four months in 2019 when renewables generated more of the UK’s electricity than fossil fuels: March, August, September and December. The first ever such month came in September 2018 and more are certain to follow.

National Grid, which manages Great Britain’s high-voltage electricity transmission network, is aiming to be able to run the system without fossil fuels by 2025, at least for short periods. At present, it sometimes has to ask windfarm operators to switch off and gas plants to start running in order to keep the electricity grid stable.

Note that biomass accounted for 11% of UK electricity generation in 2019, nearly a third of the total from all renewables. Some two-thirds of the biomass output is from “plant biomass”, primarily wood pellets burnt at Lynemouth in Northumberland and the Drax plant in Yorkshire. The remainder was from an array of smaller sites based on landfill gas, sewage gas or anaerobic digestion.

The CCC says the UK should “move away” from large-scale biomass power plants, once existing subsidy contracts for Drax and Lynemouth expire in 2027.

Using biomass to generate electricity is not zero-carbon and in some circumstances could lead to higher emissions than from fossil fuels. Moreover, there are more valuable uses for the world’s limited supply of biomass feedstock, the CCC says, including carbon sequestration and hard-to-abate sectors with few alternatives.

Methodology
The figures in the article are from Carbon Brief analysis of data from BEIS Energy Trends chapter 5 and chapter 6, as well as from BM Reports. The figures from BM Reports are for electricity supplied to the grid in Great Britain only and are adjusted to include Northern Ireland.

In Carbon Brief’s analysis, the BM Reports numbers are also adjusted to account for electricity used by power plants on site and for generation by plants not connected to the high-voltage national grid. This includes many onshore windfarms, as well as industrial gas combined heat and power plants and those burning landfill gas, waste or sewage gas.

By design, the Carbon Brief analysis is intended to align as closely as possible to the official government figures on electricity generated in the UK, reported in BEIS Energy Trends table 5.1.

Briefly, the raw data for each fuel is in most cases adjusted with a multiplier, derived from the ratio between the reported BEIS numbers and unadjusted figures for previous quarters.

Carbon Brief’s method of analysis has been verified against published BEIS figures using “hindcasting”. This shows the estimates for total electricity generation from fossil fuels or renewables to have been within ±3% of the BEIS number in each quarter since Q4 2017. (Data before then is not sufficient to carry out the Carbon Brief analysis.)

For example, in the second quarter of 2019, a Carbon Brief hindcast estimates gas generation at 33.1TWh, whereas the published BEIS figure was 34.0TWh. Similarly, it produces an estimate of 27.4TWh for renewables, against a BEIS figure of 27.1TWh.

National Grid recently shared its own analysis for electricity in Great Britain during 2019 via its energy dashboard, which differs from Carbon Brief’s figures.

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BC Hydro 2021 Peak Load Records highlight record-breaking electricity demand, peak load spikes, heat dome impacts, extreme cold, and shifting work-from-home patterns managed by a flexible hydroelectric system and climate-driven load trends.

Key Points

Record-breaking electricity demand peaks from extreme heat and cold that reshaped daily load patterns across BC in 2021.

✅ Heat dome and deep freeze drove sustained peak electricity demand

✅ Peak load built gradually, reflecting work-from-home behavior

✅ Flexible hydroelectric system adapts quickly to demand spikes

From June’s heat dome to December’s extreme cold, 2021 was a record-setting year, according to BC Hydro, and similar spikes were noted as Calgary's electricity use surged in frigid weather.

On Friday, the energy company released a new report on electricity demand, and how extreme temperatures over extended periods of time, along with growing scrutiny of crypto mining electricity use, led to record peak loads.

“We use peak loads to describe the electricity demand in the province during the highest load hour of each day,” Kyle Donaldson, BC Hydro spokesperson, said in a media release.

“With the heat dome in the summer and the sustained cold temperatures in December, we saw more record-breaking hours on more days last year than any other single year.”

According to BC Hydro, during summer, the Crown corporation recorded 19 of its top 25 all-time summer daily peak records — including breaking its all-time summer peak hourly demand record.

In December, which saw extremely cold temperatures and heavy snowfall, BC Hydro said its system experienced the highest and longest sustained load levels ever, as it activated its winter payment plan to assist customers.

Overall, BC Hydro says it has experienced 11 of its top 25 all-time daily peak records this winter, adding that Dec. 27 broke its all-time high peak hourly demand record.

“BC Hydro’s hydroelectric system is directly impacted by variations in weather, including drought conditions that require adaptation, and in 2021 more electricity demand records were broken than any other year prior, largely because of the back-to-back extreme temperatures lasting for days and weeks on end,” reads the report.

The energy company expects this trend to continue, noting that it has broken the peak record five times in the past five years, and other jurisdictions such as Quebec consumption record have also shattered consumption records.

It also noted that peak demand patterns have also changed since the first year of the COVID-19 pandemic, with trends seen during Earth Hour usage offering context.

“When the previous peak hourly load record was broken in January 2020, load displayed sharper increases and decreases throughout the day, suggesting more typical weather and behaviour,” said the report.

“In contrast, the 2021 peak load built up more gradually throughout the day, suggesting more British Columbians were likely working from home, or home for the holidays – waking up later and home earlier in the evening – as well as colder weather than average.”

BC Hydro also said “current climate models suggest a warming trend continuing in years to come which could increase demand year-round,” but noted that its flexible hydroelectric system can meet changes in demand quickly.

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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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