USDA Grants $4.37 Billion for Rural Energy Upgrades

Build Back Better Act Energy Savings curb volatile fossil fuel heating bills by accelerating electrification and renewable electricity, insulating households from natural gas, propane, and oil price spikes while cutting emissions and lowering energy costs.

Key Points

BBBA policies expand clean power and electrification to curb volatility, lower bills, and cut emissions.

✅ Tax credits for renewables, EVs, and efficient all-electric homes

✅ Shields households from natural gas, propane, and heating oil spikes

✅ Cuts methane, lowers bills, and improves grid reliability and jobs

Experts are forecasting serious sticker shock from home heating bills this winter. Nearly 60 percent of United States’ households heat their homes with fossil fuels, including natural gas, propane, or heating oil, and these consumers are expected to spend much more this winter because of fuel price increases.

That could greatly burden many families and businesses already operating on thin margins. Yet homes that use electricity for heating and cooking are largely insulated from the pain of volatile fuel markets, and they’re facing dramatically lower price increases as a result.

Projections say cost increases for households could range anywhere from 22% to 94% more, depending on the fuel used for heating and the severity of the winter temperatures. But the added expenditures for the 41% of U.S. households using electricity for heating are much less stark—these consumers will see only a 6% price increase on average. The projected fossil fuel price spikes are largely due to increased demand, limited supply, declining fuel stores, and shifting investment priorities in the face of climate change.

The fossil fuel industry is already seizing this moment to use high prices to persuade policymakers to vote against clean energy policies, particularly the Build Back Better Act (BBBA). Spokespeople with ties to the fossil fuel industry and some consumer groups are trying to pin higher fuel prices on the proposed legislation even before it has passed, even as analyses show the energy crisis is not spurring a green revolution on its own, let alone begun impacting fuel markets. But the claim the BBBA would cost Americans and the economy is false.

The facts tell a different story. Adopting smart climate policies and accelerating the clean energy transition are precisely the solutions to counter this vicious cycle by ending our dependance on volatile fossil fuels. The BBBA will ensure reliable, affordable clean electricity for millions of Americans, in line with a clean electricity standard many experts advocate—a key strategy for avoiding future vulnerability. Unlike fossil fuels subject to the whims of a global marketplace, wind and sunshine are always free. So renewable-generated electricity comes with an ultra-low fixed price decades into the future.

By expanding clean energy and electric vehicle tax credits, creating new incentives for efficient all-electric homes, and dedicating new funding for state and local programs, the BBBA provides practical solutions that build on lessons from Biden's climate law to protect Americans from price shocks, save consumers money, and reduce emissions fueling dangerous climate change.

What’s really causing the gas price spikes?
The U.S. Energy Information Administration’s winter 2021 energy price forecasts project that homes heated with natural gas, fuel oil, and propane will see average price increases of 30%, 43%, and 54%, respectively. Those who heat their homes with electricity, on the other hand, should expect a modest 6% increase. At the pump, drivers are seeing some of the highest gas prices in nearly a decade as the U.S. energy crisis ripples through electricity, gas, and EV markets today. And the U.S. is not alone. Countries around the globe are experiencing similar price jumps, including Britain's high winter energy costs this season.

A closer look confirms the cause of these high prices is not clean energy or climate policies—it’s fossil fuels themselves.  

First, the U.S. (and the world) are just now feeling the effects of the oil and gas industry’s reduced fuel production and spending due to the pandemic. COVID-19 brought the world’s economies to a screeching halt, and most countries have not returned to pre-COVID economic activity. During the past 20 months, the oil and gas industry curtailed its production to avoid oversupply as demand fell to all-time lows. Just as businesses were reopening, stored fuel was needed to meet high demand for cooling during 2021’s hottest summer on record, driving sky-high summer energy bills for many households. February’s Texas Big Freeze also disrupted gas distribution and production.

The world is moving again and demand for goods and services is rebounding to pre-pandemic levels. But even with higher energy demand, OPEC announced it would not inject more oil into the economy. Major oil companies have also held oil and gas spending flat in 2021, with their share of overall upstream spending at 25%, compared with nearly 40% in the mid-2010s. And as climate change threats loom in the financial world, investors are reducing their exposure to the risks of stranded assets, increasingly diversifying and divesting from fossil fuels. 

Second, despite strong and sustained growth for renewable energy, energy storage, and electric vehicles, the relatively slow pace to adopt fossil fuel alternatives at scale has left U.S. households and businesses tethered to an industry well-known for price volatility. Today, some oil drillers are using profits from higher gas prices to pay back debt and reward shareholders as demanded by investors, instead of increasing supply. Rising prices for a limited commodity in high demand is generating huge profits for many of the world’s largest companies at the expense of U.S. households.

Because 48% of homes use fossil gas for heating and another 10% heat with propane and fuel oil, more than half of U.S. households will feel the impact of rising prices on their home energy bills. One in four U.S. households continues to experience a high energy burden (meaning their energy expenses consume an inordinate amount of their income), including risks of pandemic power shut-offs that deepen energy insecurity, and many are still experiencing financial hardships exacerbated by the pandemic. Those with inefficient fossil-fueled appliances, homes, and cars will be hardest hit, and many families with fixed- and lower-incomes could be forced to choose between heat or other necessities.

We have the solutions—the BBBA will unlock their benefits for all households

Short-term band-aids may be enticing, but long-term policies are the only way out of this negative feedback loop. Clean energy and building electrification will prevent more costly disasters in the future, but they’re the very solutions the fossil fuel industry fights at every turn. All-electric homes and vehicles are a natural hedge against the price spikes we’re experiencing today since renewables are inherently devoid of fuel-related price fluctuations.

RMI analysis shows all-electric single-family homes in all regions of the country have lower energy bills than a comparable mixed fuel-homes (i.e., electricity and gas). Electric vehicles also save consumers money. Research from University of California, Berkeley and Energy Innovation found consumers could save a total of $2.7 trillion in 2050—or $1,000 per year, per household for the next 30 years—if we accelerate electric vehicle deployment in the coming decade.

The BBBA would help deliver these consumer savings by expanding and expediting clean energy, while ensuring equitable adoption among lower-income households and underserved communities. Extending and expanding clean energy tax credits; new incentives for electric vehicles (including used electric vehicles); and new incentives for energy efficient homes and all-electric appliances (and electrical upgrades) will reduce up-front costs and spur widespread adoption of all-electric homes, buildings, and cars.

A combination of grants, incentives, and programs will promote private sector investments in a decarbonized economy, while also funding and supporting state and local governments already leading the way. The BBBA also allocates dedicated funding and makes important modifications (such as higher rebate amounts and greater point-of-purchase availability) to ensure these technologies are available to low-income households, underserved urban and rural communities, tribes, frontline communities, and people living in multifamily housing.

Finally, the BBBA proposes to make oil and gas polluters pay for the harm they are causing to people’s health and the climate through a methane fee. This fee would cost companies less than 1% of their revenue, meaning the industry would retain over 99% of its profits. In return return we’d see substantial reductions of a powerful greenhouse gas and a healthier environment in communities living near fossil fuel production. These benefits also come with a stronger economy—Energy Innovation analysis shows the methane fee would create more than 70,000 jobs by 2050 and boost gross domestic product more than $250 billion from 2023 to 2050.

The facts speak for themselves. Gas prices are rising because of reasons totally unrelated to smart climate and clean energy policies, which research shows actually lower costs. For the first time in more than a decade, America has the opportunity to enact a comprehensive energy policy that will yield measurable savings to consumers and free us from oil and gas industry control over our wallets.

The BBBA will help the U.S. get off the fossil fuel rollercoaster and achieve a stable energy future, ensuring that today’s price spikes will be a thing of the past. Proving, once and for all, that the solution to our fossil fuel woes is not more fossil fuels.

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

Key Points

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

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

✅ Leaks from switchgear, breakers, gas-insulated substations

✅ Clean air and vacuum alternatives emerging for MV/HV

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

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

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

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

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

It prevents electrical accidents and fires.

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

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

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

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

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

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

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

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

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

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

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

How do we know that SF6 is increasing?

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

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

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

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

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

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

How does SF6 get into the atmosphere?

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

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

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

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

How damaging to the climate is this gas?

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

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

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

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

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

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

Why hasn't this been banned?

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

But they faced strong opposition from industries across Europe.

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

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

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

What do regulator and electrical companies say about the gas?

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

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

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

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

Are there alternatives - and are they very expensive?

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

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

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

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

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

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

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

Some companies are feeling the winds of change

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

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

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

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

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

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

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

What happens next ?

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

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Energy Storage for Microgrids enables renewables integration via ESS, boosting resilience and reliability while supporting solar PV and wind, innovative financing, and business models, with strong growth forecast across Asia-Pacific and North America.

Key Points

Systems that store energy in microgrids to integrate renewables, boost resilience, and optimize distributed power.

✅ Integrates solar PV and wind with stable, dispatchable output

✅ Reduces costs via new financing and service business models

✅ Expands reliable power for remote, grid-constrained regions

A new report from Navigant Research examines the global market for energy storage for microgrids (ESMG), providing an analysis of trends and market dynamics in the context of the evolving digital grid landscape, with forecasts for capacity and revenue that extend through 2026.

Interest in energy storage-enabled microgrids is growing alongside an increase in solar PV and wind deployments. Although not required for microgrids to operate, energy storage systems (ESSs) have emerged as an increasingly valuable component of distributed energy networks, including virtual power plants that coordinate distributed assets, because of their ability to effectively integrate renewable generation.

“There are several key drivers resulting in the growth of energy storage-enabled microgrids globally, including the desire to improve the resilience of power supply both for individual customers and the entire grid, the need to expand reliable electricity service to new areas, rising electricity prices, and innovations in business models and financing,” says Alex Eller, research analyst with Navigant Research. “Innovations in business models and financing will likely play a key role in the expansion of the ESMG market during the coming years.”

One example of microgrid deployment for resilience is the SDG&E microgrid in Ramona built to help communities prepare for peak wildfire season.

According to the report, the most successful companies in this industry will be those that can unlock the potential of new business models to reduce the risk and upfront costs to customers. This is particularly true in Asia Pacific and North America, which are projected to be the largest regional markets for new ESMG capacity by far, a trend underscored by California's push for grid-scale batteries to stabilize the grid.

The report, “Market Data: Energy Storage for Microgrids,” outlines the key market drivers and barriers within the global ESMG market. The study provides an analysis of specific trends, including evolving grid edge trends, and market dynamics for each major world region to illustrate how different markets are taking shape. Global ESMG forecasts for capacity and revenue, segmented by region, technology, and market segment, extend through 2026. The report also briefly examines the major technology issues related to ESSs for microgrids.

Google made energy storage news recently when its parent company Alphabet announced it is hoping to revolutionize renewable energy storage using vats of salt and antifreeze. Alphabet’s secretive research lab, simply named “X,” is developing a system for storing renewable energy that would otherwise be wasted. The project, named “Malta,” is hoping its energy storage systems “has the potential to last longer than lithium-ion batteries and compete on price with new hydroelectric plants and other existing clean energy storage methods, according to X executives and researchers,” reports Bloomberg.

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Hydro One Avista takeover rejection signals Washington regulators blocking a utility acquisition over governance risk, EPS dilution, and balance sheet impact, as investors applaud share price gains and a potential US$103M break fee.

Key Points

A regulator-led block of Hydro One's Avista bid, citing EPS dilution, balance sheet risk, and governance concerns.

✅ Washington denies approval; Idaho, Oregon decisions pending.

✅ EPS dilution avoided; balance sheet strength preserved.

✅ Shares rise 5.7%; US$103M break fee if deal collapses.

Opposition politicians may not like it but investors are applauding the rejection of Hydro One Ltd.'s $6.7-billion Avista takeover of U.S.-based utility Avista Corp.

Shares in the power company controlled by the Ontario government, which has also proposed a bill redesign to simplify statements, closed at $21.53, up $1.16 or 5.7 per cent, on the Toronto Stock Exchange on Thursday.

On Wednesday, Washington State regulators said they would not allow Ontario's largest utility to buy Avista over concerns about political risk that the provincial government, which owns 47 per cent of Hydro One's shares, might meddle in Avista's operations.

Financial analysts had predicted investors would welcome the news because the deal, announced in July 2017, would have eroded earnings per share and weakened Hydro One's balance sheet.

"The Washington regulator's denial of Avista is a positive development for the shares, in our opinion," said analyst Ben Pham of BMO Capital Markets in a report on Wednesday.

"While this may sound odd, we note that the Avista deal is expected to be EPS dilutive and result in a weaker balance sheet for (Hydro One). Not acquiring Avista and refocusing its attention on its core Ontario franchise ... along with related interprovincial arrangements such as the Ontario-Quebec electricity deal under discussion would likely be viewed positively if the deal ultimately breaks."

Decisions are yet to come from Idaho and Oregon state regulators, but Washington was probably the most important as the state contains customers making up about 60 per cent of Avista's rate base, Pham said.

He pointed out that a US$103-million break fee is to be paid to Avista if the deal collapses due to a failure to obtain regulatory approval.

CIBC analyst Robert Catellier raised his 12-month Hydro One target price by 25 cents and said many shareholders will feel "relieved" that the deal had failed.

He warned that the company's earnings power could deteriorate as the province seeks to reduce power bills by 12 per cent, despite an Ontario-Quebec hydro deal that may not lower costs.

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San Juan Generating Station eyed for $1 coal-plant sale, as Farmington and Acme propose CCS retrofit, meeting emissions caps and renewable mandates by selling captured CO2 for enhanced oil recovery via a nearby pipeline.

Key Points

A New Mexico coal plant eyed for $1 and a CCS retrofit to cut emissions and sell CO2 for enhanced oil recovery.

✅ $400M-$800M CCS retrofit; 90% CO2 capture target

✅ CO2 sales for enhanced oil recovery; 20-mile pipeline gap

✅ PNM projects shutdown savings; renewable and emissions mandates

One dollar. That’s how much an aging New Mexico coal plant is worth. And by some estimates, even that may be too much.

Acme Equities LLC, a New York-based holding company, is in talks to buy the 847-megawatt San Juan Generating Station for $1, after four of its five owners decided to shut it down. The fifth owner, the nearby city of Farmington, says it’s pursuing the bargain-basement deal with Acme to avoid losing about 1,600 direct and indirect jobs in the area amid a broader just transition debate for energy workers.

We respectfully disagree with the notion that the plant is not economical

Acme’s interest comes as others are looking to exit a coal industry that’s been plagued by costly anti-pollution regulations. Acme’s plan: Buy the plant "at a very low cost," invest in carbon capture technology that will lower emissions, and then sell the captured CO2 to oil companies, said Larry Heller, a principal at the holding group.

By doing this, Acme “believes we can generate an acceptable rate of return,” Heller said in an email.

Meanwhile, San Juan’s majority owner, PNM Resources Inc., offers a distinctly different view, echoing declining coal returns reported by other utilities. A 2022 shutdown will push ratepayers to other energy alternatives now being planned, saving them about $3 to $4 a month on average, PNM has said.

“We could not identify a solution that would make running San Juan Generating Station economical,” said Tom Fallgren, a PNM vice president, in an email.

The potential sale comes as a new clean-energy bill, supported by Governor Lujan Grisham, is working its way through the state legislature. It would require the state to get half of its power from renewable sources by 2030, and 100 percent by 2045, even as other jurisdictions explore small modular reactor strategies to meet future demand. At the same time, the legislation imposes an emissions cap that’s about 60 percent lower than San Juan’s current levels.

In response, Acme is planning to spend $400 million to $800 million to retrofit the facility with carbon capture and sequestration technology that would collect carbon dioxide before it’s released into the atmosphere, Heller said. That would put the facility into compliance with the pending legislation and, at the same time, help generate revenue for the plant.

The company estimates the system would cut emissions by as much as 90 percent, and the captured gas could be sold to oil companies, which uses it to enhance well recovery. The bottom line, according to Heller: “A winning financial formula.”

It’s a tricky formula at best. Carbon-capture technology has been controversial, even as new coal plant openings remain rare, expensive to install and unproven at scale. Additionally, to make it work at the San Juan plant, the company would need to figure out how to deliver the CO2 to customers since the nearest pipeline is about 20 miles (32 kilometers) away.

Reducing costs

Acme is also evaluating ways to reduce costs at San Juan, Heller said, including approaches seen at operators extending the life of coal plants under regulatory scrutiny, such as negotiating a cheaper coal-supply contract and qualifying for subsidies.

Farmington’s stake in the plant is less than 10 percent. But under terms of the partnership, the city — population 45,000 — can assume full control of San Juan should the other partners decide to pull out, mirroring policy debates over saving struggling nuclear plants in other regions. That’s given Farmington the legal authority to pursue the plant’s sale to Acme.

At the end of the day, nobody wants the energy

“We respectfully disagree with the notion that the plant is not economical,” Farmington Mayor Nate Duckett said by email. Ducket said he’s in better position than the other owners to assess San Juan’s importance “because we sit at Ground Zero.”

The city’s economy would benefit from keeping open both the plant and a nearby coal mine that feeds it, according to Duckett, with operations that contribute about $170 million annually to the local area.

While the loss of those jobs would be painful to some, Camilla Feibelman, a Sierra Club chapter director, is hard pressed to see a business case for keeping San Juan open, pointing to sector closures such as the Three Mile Island shutdown as evidence of shifting economics. The plant isn’t economical now, and would almost certainly be less so after investing the capital to add carbon-capture systems.

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Nighttime Thermoelectric Generator converts radiative cooling into renewable energy, leveraging outer space cold; a Stanford-UCLA prototype complements solar, serving off-grid loads with low-power output during peak evening demand, using simple materials on a rooftop.

Key Points

A device converting nighttime radiative cooling into electricity, complementing solar for low-power evening needs.

✅ Uses thermocouples to convert temperature gradients to voltage.

✅ Exploits radiative cooling to outer space for night power.

✅ Complements solar; low-cost parts suit off-grid applications.

Two years ago, one freezing December night on a California rooftop, a tiny light shone weakly with a little help from the freezing night air. It wasn't a very bright glow. But it was enough to demonstrate the possibility of generating renewable power after the Sun goes down.

Working with Stanford University engineers Wei Li and Shanhui Fan, University of California Los Angeles materials scientist Aaswath Raman put together a device that produces a voltage by channelling the day's residual warmth into cooling air, effectively generating electricity from thin air with passive heat exchange.

"Our work highlights the many remaining opportunities for energy by taking advantage of the cold of outer space as a renewable energy resource," says Raman.

"We think this forms the basis of a complementary technology to solar. While the power output will always be substantially lower, it can operate at hours when solar cells cannot."

For all the merits of solar energy, it's just not a 24-7 source of power, although research into nighttime solar cells suggests new possibilities for after-dark generation. Sure, we can store it in a giant battery or use it to pump water up into a reservoir for later, but until we have more economical solutions, nighttime is going to be a quiet time for renewable solar power. 

Most of us return home from work as the Sun is setting, and that's when energy demands spike to meet our needs for heating, cooking, entertaining, and lighting.

Unfortunately, we often turn to fossil fuels to make up the shortfall. For those living off the grid, it could require limiting options and going without a few luxuries.

Shanhui Fan understands the need for a night time renewable power source well. He's worked on a number of similar devices, including carbon nanotube generators that scavenge ambient energy, and a recent piece of technology that flipped photovoltaics on its head by squeezing electricity from the glow of heat radiating out of the planet's Sun-warmed surface.

While that clever item relied on the optical qualities of a warm object, this alternative device makes use of the good old thermoelectric effect, similar to thin-film waste-heat harvesting approaches now explored.

Using a material called a thermocouple, engineers can convert a change in temperature into a difference in voltage, effectively turning thermal energy into electricity with a measurable voltage. This demands something relatively toasty on one side and a place for that heat energy to escape to on the other.

The theory is the easy part – the real challenge is in arranging the right thermoelectric materials in such a way that they'll generate a voltage from our cooling surrounds that makes it worthwhile.

To keep costs down, the team used simple, off-the-shelf items that pretty much any of us could easily get our hands on.

They put together a cheap thermoelectric generator and linked it with a black aluminium disk to shed heat in the night air as it faced the sky. The generator was placed inside a polystyrene enclosure sealed with a window transparent to infrared light, and linked to a single tiny LED.

For six hours one evening, the box was left to cool on a roof-top in Stanford as the temperature fell just below freezing. As the heat flowed from the ground into the sky, the small generator produced just enough current to make the light flicker to life.

At its best, the device generated around 0.8 milliwatts of power, corresponding to 25 milliwatts of power per square metre.

That might just be enough to keep a hearing aid working. String several together and you might just be able to keep your cat amused with a simple laser pointer. So we're not talking massive amounts of power.

But as far as prototypes go, it's a fantastic starting point. The team suggests that with the right tweaks and the right conditions, 500 milliwatts per square metre isn't out of the question.

"Beyond lighting, we believe this could be a broadly enabling approach to power generation suitable for remote locations, and anywhere where power generation at night is needed," says Raman.

While we search for big, bright ideas to drive the revolution for renewables, it's important to make sure we don't let the smaller, simpler solutions like these slip away quietly into the night.

This research was published in Joule.

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