LED milestone passes quietly

By Toronto Star


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It passed by without much mention, but early this summer a major milestone was reached in the realm of LED lighting.

Home Depot quietly began taking online orders for a light-emitting diode LED bulb designed to replace a standard 40-watt incandescent bulb. It consumes only 8.6 watts of power, boasts superior light quality, can be dimmed, and unlike compact fluorescent bulbs doesn't contain any mercury.

The milestone is that Home Depot is selling this bulb for $20 US, half the price of most other retail offerings. Sounds pricey, yes, but keep in mind the bulb is supposed to last more than two decades and will save you at least $200 in energy costs over that time.

Industry watchers say the bulb, made for Home Depot by Lighting Sciences Group, will put pressure on other bulb manufacturers, including General Electric, Philips and Osram Sylvania, to speed up their own production plans and push costs down.

A number of manufacturers are expected to come out with 60-watt equivalent LED bulbs before year's end. It will be interesting to see what price points they hit.

"We're in the midst of the great lighting transformation, with solid-state LEDs on the cusp of transforming the lighting industry," Eric Wesoff, a senior analyst at GTM Research, declared. "The Edison bulb will soon be a relic and CFLs an interim step."

If you ask me, it can't come soon enough. I use compact fluorescent lamps CFLs throughout my home, and like most people are happy that the price of these energy-efficient bulbs have come down so dramatically. Too often, however, they have let me down.

The mercury issue bugs me, but with proper disposal I can live with that. Even the light quality of CFLs has improved and won me over. My problem is that they fail prematurely, despite claims of long life.

This happened most recently while sitting in my living room. I have four recessed lighting fixtures in this room that can be dimmed, and one of them contains a CFL bulb that was designed for the purpose.

I moved into this house only three years ago, but just recently the CFL sizzled, popped and died. My plan was to replace the three remaining incandescent bulbs with a CFL when they burned out. Unfortunately, the CFL blew first. That's not how it's supposed to happen.

Still, even at $20 a bulb I'm not sure I'd opt for the LED option just yet. Past studies indicate that $10 is the threshold to fall below before most consumers start biting.

CFLs had to make the same journey. The average cost of a standard CFL hit about $19 back in 1996, fell to $11 in 1999 and below $6 by 2003, according to a four-year-old report by U.S.-based Pacific Northwest National Laboratory. Today, they're about $1.50 each.

Will it take seven years to get to a $6 LED bulb, and 14 years to get to $1.50? Given market demand for energy-efficient products and government attention to energy efficiency and conservation, I'm convinced LEDs face a much shorter path.

In 1996, for example, retailers such as Wal-Mart and Home Depot weren't using their purchasing power to accelerate the introduction and adoption of green products and put pressure on rivals to do the same. Today, exerting such influence is creating strategic benefits in the retail market.

As we wait for more affordable consumer LED products, it's encouraging to see many niche markets taking off.

One example is streetlights, most of which are based on high-pressure sodium HPS fixtures that give off a yellowish, gloomy light and contain mercury. These HPS lights need to be replaced every few years for between $100 and $250 per fixture.

LED lights don't have these maintenance costs – once installed they can be left alone for 20 years or so. They give off a better quality light, and they consume less electricity. Energy savings can range from 50 to 80 per cent, and that's excluding the savings on maintenance.

Halifax-based LED Roadway Lighting, which can churn out up to 5,000 of its LED streetlight fixtures each week, says there are 4.3 million streetlights in Canada. Assuming all were HPS lights, the company estimates total costs to municipalities and provinces would be nearly $16 billion over 20 years, about $12 billion of that related to electricity and $3.27 billion to maintenance.

President and co-founder Charles Cartmill says total cost would be reduced to $6.73 billion if all HPS lights were switched to his company's LED streetlight fixtures. His fixtures would cost nearly four times as much, but electricity costs would be 60 per cent lower and maintenance would be a staggering 99 per cent lower.

"Business is taking off," says Cartmill.

There's little wonder why.

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Ireland announces package of measures to secure electricity supplies

Ireland electricity support measures include PSO levy rebates, RESS 2 renewables, CRU-directed EirGrid backup capacity, and grid investment for the Celtic Interconnector, cutting bills, boosting security of supply, and reducing reliance on imported fossil fuels.

 

Key Points

Government steps to cut bills and secure supply via PSO rebates, RESS 2 renewables, backup power, and grid upgrades.

✅ PSO levy rebates lower domestic electricity bills.

✅ RESS 2 adds wind, solar, and hydro to the grid.

✅ EirGrid to procure temporary backup capacity for winter peaks.

 

Ireland's Cabinet has approved a package of measures to help mitigate the rising cost of rising electricity bills, as Irish provider price increases continue to pressure consumers, and to ensure secure supplies to electricity for households and business across Ireland over the coming years.

The package of measures includes changes to the Public Service Obligation (PSO) levy (beyond those announced earlier in the year), which align with emerging EU plans for more fixed-price electricity contracts to improve price stability. The changes will result in rebates, and thus savings, for domestic electricity bills over the course of the next PSO year beginning in October. This further reduction in the PSO levy occurs because of a fall in the relative cost of renewable energy, compared to fossil fuel generation.

The Government has also approved the final results of the second onshore Renewable Electricity Support Scheme (RESS 2) auction, echoing how Ontario's electricity auctions have aimed to lower costs for consumers. This will bring significantly more indigenous wind, solar and hydro-electric energy onto the National Grid. This, in turn, will reduce our reliance on increasingly expensive imported fossil fuels, as the UK explores ending the gas-electricity price link to curb bills.

The package also includes Government approval for the provision of funding for back-up generation capacity, to address risks to security of electricity supply over the coming winters, similar to the UK's forthcoming energy security law approach in this area. The Commission for the Regulation of Utilities (CRU), which has statutory responsibility for security of supply, has directed EirGrid to procure additional temporary emergency generation capacity (for the winters of 2023/2024 to 2025/2026). This will ultimately provide flexible and temporary back-up capacity, to safeguard secure supplies of electricity for households and businesses as we deploy longer-term generation capacity.

Today’s measures also see an increased borrowing limit (€3 billion) for EirGrid – to strengthen our National Grid as part of 'Shaping Our Electricity Future' and to deliver the Celtic (Ireland-France) Interconnector, amid wider European moves to revamp the electricity market that could enhance cross-border resilience. An increased borrowing limit (€650 million) for Bord na Móna will drive greater deployment of indigenous renewable energy across the Midlands and beyond – as part of its 'Brown to Green' strategy, while measures like the UK's household energy price cap illustrate the scale of consumer support elsewhere.

 

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Cheap at Last, Batteries Are Making a Solar Dream Come True

Solar Plus Storage is accelerating across utilities and microgrids, pairing rooftop solar with lithium-ion batteries to enhance grid resilience, reduce peak costs, prevent blackouts, and leverage tax credits amid falling prices and decarbonization goals.

 

Key Points

Solar Plus Storage combines solar generation with batteries to shift load, boost reliability, and cut energy costs.

✅ Cuts peak demand charges and enhances blackout resilience

✅ Falling battery and solar costs drive nationwide utility adoption

✅ Enables microgrids and grid services like frequency regulation

 

Todd Karin was prepared when California’s largest utility shut off power to millions of people to avoid the risk of wildfires last month. He’s got rooftop solar panels connected to a single Tesla Powerwall in his rural home near Fairfield, California. “We had backup power the whole time,” Karin says. “We ran the fridge and watched movies.”

Californians worried about an insecure energy future are increasingly looking to this kind of solution. Karin, a 31-year-old postdoctoral fellow at Lawrence Berkeley National Laboratory, spent just under $4,000 for his battery by taking advantage of tax credits. He's also saving money by discharging the battery on weekday evenings, when energy is more expensive during peak demand periods. He expects to save around $1,500 over the 10 years the battery is under warranty.

The economics don’t yet work for every household, but the green-power combo of solar panels plus batteries is popping up on a much bigger scale in some unexpected places. Owners of a rice processing plant in Arkansas are building a system to generate 26 megawatts of solar power and store another 40 MW. The plant will cut its power bill by a third, and owners say they will pass the savings to local rice growers. New York’s JFK Airport is installing solar plus storage to reduce its power load by 10 percent, while Pittsburgh International Airport is building a 20-MW solar and natural gas microgrid to keep it independent from the local utility. Officials at both airports are worried about recent power shutdowns due to weather and overload-related blackouts.

And residents of the tiny northern Missouri town of Green City (pop. 608) are getting 2.5 MW of solar plus four hours of battery storage from the state’s public utility next year. The solar power won’t go directly to townspeople, but instead will back up the town’s substation, reducing the risk of a potential shutdown. It’s part of a $68 million project to improve the reliability of remote substations far from electric generating stations.

“It’s a pretty big deal for us,” says Chad Raley, who manages technology and renewables at Ameren, a Missouri utility that is building three rural solar-plus-storage projects to better manage the flow of electricity across the local grid. “It gives us so much flexibility with renewable generation. We can’t control the sun or clouds or wind, but we can have battery storage.”

The first solar-plus-storage installations started about a decade ago on a small scale in sunny states like California, Hawaii, and Arizona. Now they’re spreading across the country, driven by falling prices of both solar panels and lithium-ion batteries the size of a shipping container imported from both China and South Korea, with wind, solar, and batteries making up most of the utility-scale pipeline nationwide. These countries have ramped up production efficiencies and lowered labor costs, leaving many US manufacturers in the dust. In fact, the price of building a comparable solar-plus-storage generating facility is now cheaper than operating a coal-fired power plant, industry officials say. In certain circumstances, the cost is equal to some natural gas plants.

“This is not just a California, New York, Massachusetts thing,” says Kelly Speakes-Backman, CEO of the Energy Storage Association, an industry group in Washington. She says more than 30 states have renewable storage on the grid. Utilities have proposed and states have approved 7 gigawatts to be installed by 2030, and most new storage will be paired with solar across the US.

Speakes-Backman estimates the unit cost of electricity produced from a solar-plus-storage system will drop 10 to 15 percent each year through 2024, supporting record growth in solar and storage investments. “If you have the option of putting out a polluting or non-polluting generating source at the same price, what are you going to pick?” says Speakes-Backman.

She notes that PJM, a large Mid-Atlantic wholesale grid operator, announced it will deploy battery storage to help smooth out fluctuating power from two wind farms it operates. “When the grid fluctuates, storage can react to it quickly and can level out the supply,” she says. In the Midwest, grid-level battery storage is also being used to absorb extra wind power. Batteries hold onto the wind and put it back onto the grid when people need it.

While the solar-plus-storage trend isn’t yet putting a huge dent in our fossil fuel use, according to Paul Denholm, an energy analyst at the National Renewable Energy Laboratory in Golden, Colorado, it is a good beginning and has the side effect of cutting air pollution. By 2021, solar and other renewable energy sources will overtake coal as a source of energy, and the US is moving toward 30% electricity from wind and solar, according to a new report by the Institute for Energy Economics and Financial Analysis, a nonprofit think tank based in Cleveland.

That’s a glimmer of hope in a somewhat dreary week of news on carbon emissions. A new United Nations report released this week finds that the planet is on track to warm by 3.9 degrees Celsius (7 Fahrenheit) by 2100 unless drastic cuts are made by phasing out gas-powered cars, eliminating new coal-fired power plants, and changing how we grow and manage land, and scientists are working to improve solar and wind power to limit climate change as well.

Energy-related greenhouse gas emissions in the US rose 2.7 percent in 2018 after several years of decline. The Trump administration has rolled back climate policies from the Obama years, including withdrawing from the Paris climate accords.

There may be hope from green power initiatives outside the Beltway, though, and from federal proposals like a tenfold increase in US solar that could remake the electricity system. Arizona plans to boost solar-plus-storage from today’s 6 MW to a whopping 850 MW by 2025, more than the entire capacity of large-scale batteries in the US today. And some folks might be cheering the closing of the West’s biggest coal-fired power plant, the 2.25-gigawatt Navajo Generating Station, in Arizona, which had spewed soot and carbon dioxide over the region for 45 years until last week. The closure might help the planet and clear the hazy smog over the Grand Canyon.

 

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Ontario Ministry of Energy proposes growing hydrogen economy through reduced electricity rates

Ontario Hydrogen Strategy accelerates green hydrogen via electrolysis, reduced electricity rates, and IESO pilots, leveraging ICI, interruptible rates, and surplus power to grow clean tech, low-carbon energy, and export markets across Ontario.

 

Key Points

A provincial plan to scale green hydrogen with electricity costs, IESO pilots, and surplus power to boost tech.

✅ Amends ICI to admit hydrogen producers from 50 kW demand

✅ Enables co-located electrolysers to use surplus curtailed power

✅ Offers interruptible rates via IESO pilot for flexible loads

 

The Ontario Ministry of Energy is seeking input on accelerating Ontario’s hydrogen economy. The province has been promoting growth in the clean tech sector, including low-carbon energy production and the Hydrogen Innovation Fund, as an avenue for post-COVID-19 economic recovery. Hydrogen produced through electrolysis (or “green hydrogen”) has been central to these efforts, complimenting both federal and provincial initiatives to create vibrant domestic and export markets for the energy as a principal alternative to conventional fossil fuels.

On April 14, 2022, the Ministry filed a proposal (the Proposal) on the Environmental Registry of Ontario (ERO) to gather input from stakeholders, aligning with the province’s industrial electricity pricing consultation underway. As part of Ontario’s Hydrogen Strategy, the Ministry is considering several options that would provide reduced electricity rates for green hydrogen producers to make production more economically competitive with other energies. To date, the relatively high production cost of green hydrogen has been a challenge facing its adoption, both domestically and internationally.

The Proposal features three options:

  • Amending the rules for the Industrial Conservation Initiative (ICI) applicable to hydrogen producers;
  • Enabling onsite hydrogen production using electricity that would otherwise be curtailed; and
  • Providing an interruptible electricity rate for hydrogen producers.

Option 1: Amending the ICI rules

Option 1 would amend the ICI rules to allow all hydrogen producers with an average monthly peak demand of 50kW to participate. Hydrogen producers’ facilities could qualify for ICI in the first year of operation with a peak demand factor determined based on a deemed consumption profile, using a method yet to be determined by the Ministry. At the end of the first year, their global adjustment (GA) charges would be reconciled based on their actual consumption pattern. As set out in our prior article, GA was introduced by the province in January 2005 to ensure reliable, sustainable and a diverse supply of power at stable and competitive prices, aligning with plans to rely on battery storage to meet rising energy demand. The Ministry’s current proposal would require hydrogen producers to place a security deposit for their facilities’ first year of operation with the Independent Electricity System Operator (IESO) or their Local Distribution Company (LDC) to ensure other consumer would not be adversely affected.

Option 2: Enable onsite hydrogen production using surplus electricity

Option 2 would allow businesses to co-locate hydrogen electrolysers at electricity generation facilities, drawing on recent electrolyzer investment trends, to make use of what would become curtailed generation. Under this option in the Proposal, the developer for the hydrogen production facility would be required to be a separate legal entity from the one that owns or operates the electricity generation facility. Based on this required level of independence, the hydrogen developer would be required to pay the electricity generator for the electricity supply.

At this stage, it is not clear whether, or how the generator would be required to share the revenue with other consumers. The next steps of the Proposal may require regulatory amendments, and/or amendments to electricity generator’s contracts, consistent with efforts enabling storage in Ontario's electricity system to integrate flexible resources.

Option 3: Interruptible electricity rates for hydrogen producers

In 2021, the Ministry posted a proposal on the ERO including an Interruptible Rate Pilot that was to be developed in conjunction with the IESO in order to address stakeholder feedback received during the 2019 Industrial Consultation specific to the challenges of identifying and responding to peak demand events while participating in the ICI. The pilot was targeted towards large electricity consumers, where participants were charged GA at a reduced rate in exchange for agreeing to reduce consumption during system or local reliability events, as identified by IESO.

Option 3 would allow for the introduction for a dedicated stream for hydrogen producers into the interruptible rate pilot, which is currently under development with the IESO. This would take into account the unique circumstances of hydrogen producers, as well as the importance of the hydrogen sector in Ontario’s Low-Carbon Hydrogen Strategy. Under the pilot, participants would be given advance notice by the IESO to reduce demand over a fixed number of hours, several times each year, and emerging vehicle-to-grid models where EV owners can sell electricity back to the grid highlight additional flexibility options. Ultimately, the pilot would support low-carbon hydrogen production by offering large electricity consumers, such as hydrogen producers, reduced electricity rates in exchange for reduces consumption during system or local reliability events.

Following this initial development work, the Ministry intends to consult with stakeholders later this year to determine design details, as well as the timing for the potential roll out of the proposed pilot.

Key takeaways

The design options are not meant to be mutually exclusive, and might be pursued by the Ministry in combination. Ultimately, Ontario is focusing on ways to reduce electricity rates in an attempt to make the province a leader in the adoption of green hydrogen, as made clear in the Ontario Hydrogen Strategy, even as an electricity supply crunch looms, underscoring the urgency. Stakeholders will want to participate in this process given its long-term implications for both the hydrogen and power sectors.

 

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Energy experts: US electric grid not designed to withstand the impacts of climate change

Summer Power Grid Reliability and Climate Risk drives urgent planning as extreme heat, peak demand, drought, and aging infrastructure strain ERCOT, NERC regions, risking outages without renewables integration and climate-informed grid modeling.

 

Key Points

Assessment of how extreme weather and demand stress the US grid, informing climate-smart planning to reduce outages.

✅ Many operators rely on historical weather, not climate projections

✅ NERC flags elevated blackout risk amid extreme heat and drought

✅ Renewables and storage can boost capacity and cut emissions

 

As heat ramps up ahead of what forecasters say will be a hotter than normal summer, electricity experts and officials are warning that states may not have enough power to meet demand in the coming months. And many of the nation's grid operators are also not taking climate change into account in their planning, despite available grid resilience guidance that could inform upgrades, even as extreme weather becomes more frequent and more severe.

Power operators in the Central US, in their summer readiness report, have already predicted "insufficient firm resources to cover summer peak forecasts." That assessment accounted for historical weather and the latest NOAA outlook that projects for more extreme weather this summer.

But energy experts say that some power grid operators are not considering how the climate crisis is changing our weather — including more frequent extreme events — and that is a problem if the intent is to build a reliable power grid while accelerating investing in carbon-free electricity across markets.

"The reality is the electricity system is old and a lot of the infrastructure was built before we started thinking about climate change," said Romany Webb, a researcher at Columbia University's Sabin Center for Climate Change Law. "It's not designed to withstand the impacts of climate change."

Webb says many power grid operators use historical weather to make investment decisions, rather than the more dire climate projections, simply because they want to avoid the possibility of financial loss, even as climate-related credit risks for nuclear plants are being flagged, for investing in what might happen versus what has already happened. She said it's the wrong approach and it makes the grid vulnerable.

"We have seen a reluctance on the part of many utilities to factor climate change into their planning processes because they say the science around climate change is too uncertain," Webb said. "The reality is we know climate change is happening, we know the impact it has in terms of more severe heatwaves, hurricanes, drought, with recent hydropower constraints in British Columbia illustrating the risks, and we know that all of those things affect the electricity system so ignoring those impacts just makes the problems worse."

An early heatwave knocked six power plants offline in Texas earlier this month. Residents were asked to limit electricity use, keeping thermostats at 78 degrees or higher and, as extreme heat boosts electricity bills for consumers, avoid using large appliances at peak times. The Electric Reliability Council of Texas, or ERCOT, in its seasonal reliability report, said the state's power grid is prepared for the summer and has "sufficient" power for "normal" summer conditions, based on average weather from 2006 to 2020.

But NOAA's recently released summer outlook forecasts above average temperatures for every county in the nation.

"We are continuing to design and site facilities based on historical weather patterns that we know in the age of climate change are not a good proxy for future conditions," Webb said.

When asked if the agency is creating a blind spot for itself by not accounting for extreme weather predictions, an ERCOT spokesperson said the report "uses a scenario approach to illustrate a range of resource adequacy outcomes based on extreme system conditions, including some extreme weather scenarios."

The North American Electric Reliability Corporation, or NERC — a regulating authority that oversees the health of the nation's electrical infrastructure — has a less optimistic projection.

In a recent seasonal reliability report, NERC placed Texas at "elevated risk" for blackouts this summer. It also reported that while much of the nation will have adequate electricity this summer, several markets are at risk of energy emergencies.

California grid operators, who recently avoided widespread rolling blackouts as heat strained the grid, in its summer reliability report also based its readiness analysis on "the most recent 20 years of historical weather data." The report also notes the assessment "does not fully reflect more extreme climate induced load and supply uncertainties."

Compounding the US power grid's supply and demand problem is drought: NERC says there's been a 2% loss of reliable hydropower from the nation's power-producing dams. Add to that the rapid retirement of many coal power plants — all while nearly everything from toothbrushes to cars are now electrified. Energy experts say adding more renewables into the mix will have the dual impact of cutting climate change inducing greenhouse gas emissions but also increasing the nation's power supply, aligning with efforts such as California's 100% carbon-free mandate that aim to speed the transition.
 

 

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Tesla reduces Solar + home battery pricing following California blackouts

Tesla Solar and Powerwall Discount offers a ~10% installation price cut amid PG&E blackouts, helping California homeowners with solar panels, battery storage, and backup power, while supporting renewable energy and resilient Supercharger infrastructure.

 

Key Points

A ~10% installation discount on Tesla solar panels and Powerwall batteries to boost backup power during PG&E blackouts.

✅ ~10% off installation for solar plus Powerwall

✅ Helps during PG&E shutoffs and wildfire mitigation

✅ Supports resilience, backup power, and EV charging

 

Pacific Gas & Electric’s (PG&E) shutoff of electric supply to residents in California’s Bay Area has caught the attention of Tesla and SpaceX CEO Elon Musk, who, while highlighting a huge future for Tesla Energy in coming years, has announced that he would be offering a price reduction of approximately 10% for a solar panel and Tesla Powerwall battery installation. The discount will be available to anyone interested in powering their homes with solar energy, not just the 800,000 affected homes in the Bay Area.

After initially tweeting a link to Tesla’s Solar page on Tesla.com, Musk added that he would be offering a “~10% price reduction” in installation price for solar panels and Powerwall batteries for anyone, as California explores EVs for grid stability during emergencies, including those who have lost power in response to PG&E’s power shutoff. The blackout induced by the California-based power company is a part of an effort to reduce the possibility of wildfires. PG&E lines were the cause of multiple fires in the past, so the company is taking every necessary precaution to reduce the probability of its lines causing another fire in the future.

Tesla Solar recently offered a subscription program that would allow homeowners to lease panels for a fraction of the cost. The service is available to both residential and commercial customers, and costs as little as $45 a month in some states, particularly appealing in California where EV sales top 20% recently. The option to lease solar panels carries no long-term contracts that would tie down customers to a lengthy commitment.

Wildfires have always been an issue in California. Currently, fires are ripping through Los Angeles county, presumably caused by the winds of the Autumn season. The effort to reduce the environmental impact of forest fires in the state has been increasingly more prevalent over the years. But 2019 is a different story, underscoring that California may need a much bigger grid to support electrification, considering the previous year was noted as the deadliest wildfire season in California’s history. Over 8,500 fires destroyed over 1.89 million acres of land burned due to fires, causing the California Department of Forestry and Fire Protection to spend $432 million through the end of August 2018, according to the Associated Press.

In reaction to the news of the power shutoffs, Tesla added words of advice to vehicle affected owners on its app. The company posted a message encouraging drivers to keep their vehicles charged to 100% and highlighted that EVs can power homes for up to three days during outages, in order to prevent interruptions in driving. Those who are driving ICE vehicles are feeling the effects of the blackout too, as gas stations in California’s affected region have begun to shut down. Musk also tweeted that he would be installing Tesla Powerpacks at all Supercharger stations in the affected region, a move that can help ease strain on state power grids during outages, in order to allow owners to charge their vehicles.

In addition to the efforts that Tesla has already put into place, Musk plans to transition all Supercharger stations to solar power as soon as possible. But the sunny climate of California offers residents a great opportunity to move from gas and electric, even as some warn of a looming green car wreck in the state, to a more eco-friendly, sun-powered option. Tesla solar will completely eliminate power blackouts that are used to control wildfires in California.

 

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Cheap material converts heat to electricity

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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