California's Looming Green New Car Wreck

U.S. Solar-Plus-Storage Growth 2021-2024 highlights rising battery storage co-location with solar PV, grid flexibility, RTO/ISO market signals, and ITC incentives, enabling peak shaving, firming renewable output, and reliable night-time power.

Key Points

Summary of U.S. plans pairing battery storage with solar PV, guided by RTO/ISO markets, grid needs, and ITC policy.

✅ 9.4 GW (63%) co-located with solar PV by 2024

✅ 97% of standalone capacity sited in RTO/ISO regions

✅ ITC improves project economics and grid services revenue

Of the 14.5 gigawatts (GW) of battery storage power capacity planned to come online amid anticipated growth in solar and storage in the United States from 2021 to 2024, 9.4 GW (63%) will be co-located with a solar photovoltaic (PV) solar-plus-storage power plant, based on data reported to us and published in our Annual Electric Generator Report. Another 1.3 GW of battery storage will be co-located at sites with wind turbines or fossil fuel-fired generators, such as natural gas-fired plants. The remaining 4.0 GW of planned battery storage will be located at standalone sites.

Historically, most U.S. battery systems have been located at standalone sites. Of the 1.5 GW of operating battery storage capacity in the United States at the end of 2020, 71% was standalone, and 29% was located onsite with other power generators.

Most standalone battery energy storage sites have been planned or built in power markets that are governed by regional transmission organizations (RTOs) and independent system operators (ISOs). RTOs and ISOs can enforce standard market rules that lay out clear revenue streams for energy storage projects in their regions, which promotes the deployment of battery storage systems. Of the utility-scale pipeline battery systems announced to come online from 2021 to 2024, 97% of the standalone battery capacity and 60% of the co-located battery capacity are in RTO/ISO regions.

Over 90% of the planned battery storage capacity outside of RTO and ISO regions will be co-located with a solar PV plant. At some solar PV co-located plants, the batteries can charge directly from the onsite solar generator when electricity demand and prices are low. They can then discharge electricity to the grid when peak demand is higher or when solar generation is unavailable, such as at night.

Although factors such as cloud cover can affect solar generation output, solar generators, now the number three renewable source in the U.S., in particular can effectively pair with battery storage because of their relatively regular daily generation patterns. This predictability works well with battery systems because battery systems are limited in how long they can discharge their power capacity before needing to recharge. If paired with a wind turbine, for example, a battery system could go days before having the opportunity to fully recharge.

Another advantage of pairing batteries with renewable generators is the ability to take advantage of tax incentives such as the Investment Tax Credit (ITC), which is available for solar projects, and other favorable government plans supporting deployment.

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Lion Electric Battery Plant Quebec secures near $100M public investment for an automated battery-pack assembly in Saint-Jérôme, fueling EV manufacturing, R&D, local supply chains, and heavy-duty zero-emission vehicle competitiveness and jobs.

Key Points

Automated battery-pack plant in Saint-Jérôme boosting EV manufacturing and strengthening Quebec's supply chain.

✅ $100M joint federal-provincial investment announced

✅ 135 jobs in 2023; 150 more long-term positions

✅ R&D hub to enhance heavy-duty EV battery performance

Canadian Prime Minister of Canada, Justin Trudeau, and the Premier of Quebec, François Legault, have announced an equal investment totalling nearly $100 million to Lion Electric, as a B.C. battery plant announcement has done in another province, for the establishment of a highly automated battery-pack assembly plant in Saint–Jérôme, in the Laurentians. This project, valued at nearly $185 million, will create 135 jobs when construction of the plant is completed in 2023. It is also expected that 150 additional jobs will be created over the longer term.

For the announcement, Mr. Trudeau and Mr. Legault were accompanied by the Minister of Innovation, Science and Industry, François-Philippe Champagne, by Quebec's Minister of Economy and Innovation, Pierre Fitzgibbon, and by Marc Bédard, President and Founder of Lion Electric.

The battery packs assembled at the new plant will be used in Lion Electric vehicles. This strategic investment will allow the company to improve its cost structure, and better control the design and shape of its batteries, making it more competitive in the heavy-duty electric vehicle market, as EV assembly deals put Canada in the race. Ultimately, the company will be able to increase the volume of its vehicle production. Lion Electric will be the first Canadian manufacturer of medium and heavy-duty vehicles to have state-of-the-art, automated battery-pack manufacturing facilities.

The company will also establish a research and development innovation centre within its manufacturing plant, which will allow it to test and refine products for future use, including batteries for emergency vehicles such as ambulances. The company will test innovations from research and development, including energy storage capacity and battery performance. The results will make these products more competitive in the North American market, where a Niagara Region battery plant signals growing demand.

The company said it expects to employ 135 people at the plant when it is operational by 2023. It also plans to invest in a research and development facility that could create a number of spinoff jobs.

"When we talk about an economic recovery that's good for workers, for families and for the environment, this is exactly the kind of project we mean," Trudeau said at a news conference in Montreal.

Trudeau toured Lion Electric's factory in Saint-Jérôme, Que., last March, just before the pandemic. (Ryan Remiorz/The Canadian Press)
It was the prime minister's first trip to Montreal in more than a year. He said one of the reasons he decided to attend the announcement was to illustrate the importance of the green economy and how Canada can capitalize on the U.S. EV pivot for future job growth.

The project also aligns with the Legault government's desire to create a supply chain within Quebec that is able to feed the electric vehicle industry, where Canada-U.S. collaboration could accelerate progress.

At Monday's announcement, Economy Minister Pierre Fitzgibbon spoke at length about the province's deposits of lithium and nickel — key components in electric vehicle batteries — as well as its supply of low-emission hydroelectricity.

"If we play our cards right, we could become world leaders in this market of the future," Fitzgibbon said.

Currently, many of those strategic minerals found in Quebec are exported to Asia where they are turned into battery cells, and then imported back to Quebec by companies like Lion, said Mickaël Dollé, a chemistry professor at the Université de Montréal.

By opening a battery assembly plant in Quebec, Lion could help stimulate more cell-makers, such as the Northvolt project near Montreal, to set up shop in the province. Further localizing the supply chain, Dollé said, means better value and a greener product. 

But other countries have the same goal in mind, he said, and the window for the province to establish itself as an important player in the emerging electric vehicle battery industry is closing quickly, as major Ford Oakville deal commitments accelerate competition.

"The decision has to be taken now, or in the coming months, but if we wait too long we may miss our main goal which is to get our own supply chain in Canada," Dollé said.

What's in a name?
Monday's announcement was closely watched in Quebec for what it foretold about the political future as well as the economic one.

By coming to Montreal and touring a vaccination clinic before making the funding announcement, Trudeau fed speculation in the province that he is preparing to call an election soon.

Intrigue also surrounded the informal meeting Trudeau had with Legault on Monday. The Quebec premier and members of his government have repeatedly expressed frustration with Trudeau during the pandemic.

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Spain has broken its reliance on fossil gas as soaring wind and solar energy drive Europe’s lowest wholesale electricity prices, reducing emissions, stabilizing the grid, and advancing renewable power, energy independence, and clean transition goals across the EU.

How Has Spain Broken the Gas Link with Wind and Solar??

Spain has broken the link between gas and power prices by rapidly expanding wind and solar generation, which now supplies nearly half its electricity, cutting fossil fuel influence by 75% since 2019 and reducing power costs 32% below the EU average.

✅ Wind and solar cut fossil influence by 75% since 2019

✅ Power prices 32% below EU average in 2025

✅ Renewables meet nearly half of national electricity demand

Spain has emerged as one of Europe’s most affordable electricity markets, largely due to its rapid expansion of wind and solar power. By decoupling its wholesale electricity prices from volatile fossil gas and coal, Spain has achieved a 32 percent lower average wholesale price than the EU average in the first half of 2025. This remarkable shift marks a dramatic turnaround from 2019, when Spain had some of the highest power prices in Europe.

According to new data, the influence of fossil fuels on Spain’s electricity prices has fallen by 75 percent since 2019, mirroring how renewables have surpassed fossil fuels in Europe over the same period, dropping from 75 percent of hours tied to gas costs to just 19 percent in early 2025. “Spain has broken the ruinous link between power prices and volatile fossil fuels, something its European neighbours are desperate to do,” said Dr. Chris Rosslowe, Senior Energy Analyst at Ember.

The change is driven by a surge in renewable generation. Between 2019 and mid-2025, Spain added more than 40 gigawatts of new solar and wind capacity—second only to Germany, whose power market is twice the size. Wind and solar now meet nearly half (46 percent) of Spain’s electricity demand, compared with 27 percent six years ago. As a result, fossil generation has fallen to 20 percent of total demand, well below the levels seen in other major economies such as Germany (41 percent) and Italy (43 percent).

This renewable growth has also cut Spain’s dependence on imported fuels. In the past five years, new solar and wind plants have avoided 26 billion cubic metres of gas imports, saving €13.5 billion—five times the amount the country invested in transmission infrastructure over the same period. The Central Bank of Spain estimated that wholesale electricity prices would have been 40 percent higher in 2024 if renewables had not displaced fossil generation, and neighboring France has seen negative prices during periods of renewable surplus.

August 2025 marked a historic milestone: Spain recorded a full month without coal-fired generation for the first time. A decade earlier, coal accounted for a quarter of the nation’s electricity supply. Gas use has also declined steadily, from 26% of demand in 2019 to 19% this year.

However, the system still faces challenges. Following the April 28th Iberian blackout, Spain has relied more heavily on gas-fired plants to stabilize the grid. These services—such as voltage control and balancing—have proven to be expensive, with costs doubling since the blackout and accounting for 57 percent of the average electricity price in May 2025, up from 14 percent the previous year. Curtailment of renewables has also tripled, reaching 7.2 percent of generation between May and July.

Despite being Europe’s fourth-largest electricity market, Spain ranks only 13th in battery storage capacity, underscoring the need for further investment in clean flexibility solutions, such as grid-scale batteries to provide flexibility and stronger interconnections. Post-blackout reforms aim to address this weakness and ensure the gains from renewable integration are not lost.

“Spain risks sliding back into costly gas reliance amid post-blackout fears,” warned Rosslowe. “Boosting grids and batteries will help Spain break free from fossil dependency for good.”

With record-low electricity prices and one of the fastest decoupling rates in Europe, Spain’s experience demonstrates how large-scale wind and solar adoption can reshape energy economics—and offers a roadmap for other nations seeking to escape the volatility of fossil fuels.

Vineyard Wind I advances as BOEM issues a final environmental impact statement for the 800 MW offshore wind farm south of Martha's Vineyard, delivering clean energy, jobs, and carbon reductions to Massachusetts toward net-zero.

Key Points

An 800 MW offshore wind project near Martha's Vineyard supplying clean power to Massachusetts.

✅ 800 MW capacity; power for 400,000+ homes and businesses

✅ BOEM final EIS; record of decision pending within 30+ days

✅ 1.68M metric tons CO2 avoided annually; jobs and lower rates

Federal environmental officials have completed their review of the Vineyard Wind I offshore wind farm, moving the project that is expected to deliver clean renewable energy to Massachusetts by the end of 2023 closer to becoming a reality.

The U.S. Department of the Interior said Monday morning that its Bureau of Ocean Energy Management completed the analysis it resumed about a month ago, published the project's final environmental impact statement, and said it will officially publish notice of the impact statement in the Federal Register later this week.

"More than three years of federal review and public comment is nearing its conclusion and 2021 is poised to be a momentous year for our project and the broader offshore wind industry," Vineyard Wind CEO Lars Pedersen said. "Offshore wind is a historic opportunity to build a new industry that will lead to the creation of thousands of jobs, reduce electricity rates for consumers and contribute significantly to limiting the impacts of climate change. We look forward to reaching the final step in the federal permitting process and being able to launch an industry that has such tremendous potential for economic development in communities up and down the Eastern seaboard."

The 800-megawatt wind farm planned for 15 miles south of Martha's Vineyard was the first offshore wind project selected by Massachusetts utility companies with input from the Baker administration to fulfill part of a 2016 clean energy law. It is projected to generate cleaner electricity for more than 400,000 homes and businesses in Massachusetts, produce at least 3,600 jobs, reduce costs for Massachusetts ratepayers by an estimated $1.4 billion, and eliminate 1.68 million metric tons of carbon dioxide emissions annually.

Offshore wind power, informed by the U.S. offshore wind outlook, is expected to become an increasingly significant part of Massachusetts' energy mix. The governor and Legislature agree on a goal of net-zero carbon emissions by 2050, but getting there is projected to require having about 25 gigawatts of offshore wind power. That means Massachusetts will need to hit a pace in the 2030s where it has about 1 GW of new offshore wind power on the grid coming online each year.

"I think that's why today's announcement is so historic, because it does represent that culmination of work to understand how to permit and build a cost-effective and environmentally-responsible wind farm that can deliver clean energy to Massachusetts ratepayers, but also just how to do this from start to finish," said Energy and Environmental Affairs Secretary Kathleen Theoharides. "As we move towards our goal of probably [25 GW] of offshore wind by 2050 to hit our net-zero target, this does give us confidence that we have a much clearer path in terms of permitting."

She added, "There's a huge pipeline, so getting this project out really should open the door to the many additional projects up and down the East Coast, such as Long Island proposals, that will come after it."

According to the American Wind Energy Association, there are expected to be 14 offshore projects totaling 9,112 MW of capacity in operation by 2026.

Susannah Hatch, the clean energy coalition director for the Environmental League of Massachusetts and a leader of the broad-based New England for Offshore Wind Regional group, called offshore wind farms like Vineyard Wind "the linchpin of our decarbonization efforts in New England." She said the Biden administration's quick action on Vineyard Wind is a positive sign for the burgeoning sector.

"Moving swiftly on responsibly developed offshore wind is critical to our efforts to mitigate climate change, and offshore wind also provides an enormous opportunity to grow the economy, create thousands of jobs, and drive equitable economic benefits through increased minority economic participation in New England," Hatch said.

With the final environmental impact statement published, Vineyard Wind still must secure a record of decision from BOEM, which processes wind lease requests, an air permit from the Environmental Protection Agency and sign-offs from the U.S. Army Corps of Engineers and the National Marine Fisheries Service to officially clear the way for the project that is on track to be the nation's first utility-scale offshore wind farm. BOEM must wait at least 30 days from the publication of the final environmental impact statement to issue a record of decision.

Project officials have said they expect the final impact statement and then a record of decision "sometime in the first half of 2021." That would allow the project to hit its financial close milestone in the second half of this year, begin on-shore work quickly thereafter, start offshore construction in 2022, begin installing turbines in 2023 and begin exporting power to the grid, marking Vineyard Wind first power, by late 2023, Pedersen said in January.

"Offshore energy development provides an opportunity for us to work with Tribal nations, communities, and other ocean users to ensure all decisions are transparent and utilize the best available science," BOEM Director Amanda Lefton said.

The commercial fishing industry has been among the most vocal opponents of aspects of the Vineyard Wind project and the Responsible Offshore Development Alliance (RODA) has repeatedly urged the new administration to ensure the voices of the industry are heard throughout the licensing and permitting process.

In comments submitted earlier this month in response to a BOEM review of an offshore wind project that is expected to deliver power to New York, including the recent New York offshore wind approval, RODA said the present is "a time of significant confusion and change in the U.S. approach to offshore wind energy (OSW) planning" and detailed mitigation measures it wants to see incorporated into all projects.

"To be clear, none of these requests are new -- nor hardly radical. They have simply been ignored again, and again, and again in a political push/pull between multinational energy companies and the U.S. government, leaving world-famous seafood, and the communities founded around its harvest, off the table," the group said in a press release last week. Some of RODA's suggestions were analyzed as part of BOEM's Vineyard Wind review.

Vineyard Wind has certainly taken a circuitous path to get to this point. The timeline for the project was upended in August 2019 when the Trump administration decided to conduct a much broader assessment of potential offshore wind projects up and down the East Coast, which delayed the project by almost a year.

When the Trump administration delayed its action on a final environmental impact statement last year, Vineyard Wind on Dec. 1 announced that it was pulling its project out of the federal review pipeline in order to complete an internal study on whether the decision to use a certain type of turbine would warrant changes to construction and operations plan. The Trump administration declared the federal review of the project "terminated."

Within two weeks of President Joe Biden being inaugurated, Vineyard Wind said its review determined no changes were necessary and the company resubmitted its plans for review. BOEM agreed to pick up where the Trump administration had left off despite the agency previously declaring its review terminated.

"It would appear that fishing communities are the only ones screaming into a void while public resources are sold to the highest bidder, as BOEM has reversed its decision to terminate a project after receiving a single letter from Vineyard Wind," RODA said.

The final environmental impact statement that BOEM published Monday showed that the federal regulators believe the Vineyard Wind I development as proposed will have "moderate" impacts on commercial fisheries and for-hire recreational fishing outfits, and that the project combined with other factors not related to wind energy development will have "major" impacts on commercial and recreational fishing ventures.

Vineyard Wind pointed Monday to the fishery mitigation agreements it has entered into with Massachusetts and Rhode Island, a fishery science collaboration with the University of Massachusetts Dartmouth's School of Marine Science and Technology, and an agreement with leading environmental organizations around the protection of the endangered right whale.

Responding to concerns about safe navigation among RODA and others in the fishing sector, Vineyard Wind and the four other developers holding leases for offshore wind sites off New England agreed to orient their turbines in fixed east-to-west rows and north-to-south columns spaced one nautical mile apart. Last year, the U.S. Coast Guard concluded that the grid layout was the best way to maintain maritime safety and ease of navigation in the offshore wind development areas south of Martha's Vineyard and Nantucket.

Since a 2016 clean energy law kicked off the state's foray into the offshore wind world, Massachusetts utilities have contracted for a total of about 1,600 MW between two projects, Vineyard Wind I and Mayflower Wind.

A joint venture of Shell and Ocean Winds North America, Mayflower Wind was picked unanimously in 2019 by utility executives to build and operate a wind farm approximately 26 nautical miles south of Martha's Vineyard and 20 nautical miles south of Nantucket, with South Coast construction activity expected as the project progresses. The 804-megawatt project is expected to be operational by December 2025.

Massachusetts and its utilities are expected to go out to bid for up to another 1,600 MW of offshore wind generation capacity later this year using authorization granted by the Legislature in 2018.

The climate policy bill that Gov. Charlie Baker returned to the Legislature with amendments more than a month ago would require that the executive branch direct Massachusetts utilities to buy an additional 2,400 MW of offshore wind power.

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US Renewable Energy Transition is the shift from fossil fuels to wind, solar, and nuclear, targeting net-zero emissions via grid modernization, battery storage, and new transmission to replace legacy plants and meet rising electrification.

Key Points

The move to decarbonize electricity by scaling wind, solar, and nuclear with storage and transmission upgrades.

✅ Falling LCOE makes wind and solar competitive with gas and coal.

✅ 4-hour lithium-ion storage shifts solar to evening peak demand.

✅ New high-voltage transmission links resource-rich regions to load.

Generating electricity to power homes and businesses is a significant contributor to climate change. In the United States, one quarter of greenhouse gas emissions come from electricity production, according to the Environmental Protection Agency.

Solar panels and wind farms can generate electricity without releasing any greenhouse gas emissions, and recent research suggests wind and solar could meet about 80% of U.S. demand with supportive infrastructure. Nuclear power plants can too, although today’s plants generate long-lasting radioactive waste, which has no permanent storage repository.

But the U.S. electrical sector is still dependent on fossil fuels. In 2021, 61 percent of electricity generation came from burning coal, natural gas, or petroleum. Only 20 percent of the electricity in the U.S. came from renewables, mostly wind energy, hydropower and solar energy, according to the U.S. Energy Information Administration, and in 2022 renewable electricity surpassed coal nationwide as portfolios shifted. Another 19 percent came from nuclear power.

The contribution from renewables has been increasing steadily since the 1990s, and the rate of increase has accelerated, with renewables projected to reach one-fourth of U.S. generation in the near term. For example, wind power provided only 2.8 billion kilowatt-hours of electricity in 1990, doubling to 5.6 billion in 2000. But from there, it skyrocketed, growing to 94.6 billion in 2010 and 379.8 billion in 2021.

That’s progress, as the U.S. moves toward 30% electricity from wind and solar this decade, but it’s not happening fast enough to eliminate the worst effects of climate change for our descendants.

“We need to eliminate global emissions of greenhouse gases by 2050,” philanthropist and technologist Bill Gates wrote in his 2023 annual letter. “Extreme weather is already causing more suffering, and if we don’t get to net-zero emissions, our grandchildren will grow up in a world that is dramatically worse off.”

And the problem is actually bigger than it looks, even as pathways to zero-emissions electricity by 2035 are being developed.

“We need not just to create as much electricity as we have now, but three times as much,” says Saul Griffith, an entrepreneur who’s sold companies to Google and Autodesk and has written books on mass electrification. To get to zero emissions, all the cars and heating systems and stoves will have to be powered with electricity, said Griffith. Electricity is not necessarily clean, but at least it it can be, unlike gas-powered stoves or gasoline-powered cars.

The technology to generate electricity with wind and solar has existed for decades. So why isn’t the electric grid already 100% powered by renewables? And what will it take to get there?

First of all, renewables have only recently become cost-competitive with fossil fuels for generating electricity. Even then, prices depend on the location, Paul Denholm of the National Renewable Energy Laboratory told CNBC.

In California and Arizona, where there is a lot of sun, solar energy is often the cheapest option, whereas in places like Maine, solar is just on the edge of being the cheapest energy source, Denholm said. In places with lots of wind like North Dakota, wind power is cost-competitive with fossil fuels, but in the Southeast, it’s still a close call.

Then there’s the cost of transitioning the current power generation infrastructure, which was built around burning fossil fuels, and policymakers are weighing ways to meet U.S. decarbonization goals as they plan grid investments.

“You’ve got an existing power plant, it’s paid off. Now you need renewables to be cheaper than running that plant to actually retire an old plant,” Denholm explained. “You need new renewables to be cheaper just in the variable costs, or the operating cost of that power plant.”

There are some places where that is true, but it’s not universally so.

“Primarily, it just takes a long time to turn over the capital stock of a multitrillion-dollar industry,” Denholm said. “We just have a huge amount of legacy equipment out there. And it just takes awhile for that all to be turned over.”

Intermittency and transmission
One of the biggest barriers to a 100% renewable grid is the intermittency of many renewable power sources, the dirty secret of clean energy that planners must manage. The wind doesn’t always blow and the sun doesn’t always shine — and the windiest and sunniest places are not close to all the country’s major population centers.

Wind resources in the United States, according to the the National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
Wind resources in the United States, according to the the National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
National Renewable Energy Laboratory, a national laboratory of the U.S. Department of Energy.
The solution is a combination of batteries to store excess power for times when generation is low, and transmission lines to take the power where it is needed.

Long-duration batteries are under development, but Denholm said a lot of progress can be made simply with utility-scale batteries that store energy for a few hours.

“One of the biggest problems right now is shifting a little bit of solar energy, for instance, from say, 11 a.m. and noon to the peak demand at 6 p.m. or 7 p.m. So you really only need a few hours of batteries,” Denholm told CNBC. “You can actually meet that with conventional lithium ion batteries. This is very close to the type of batteries that are being put in cars today. You can go really far with that.”

So far, battery usage has been low because wind and solar are primarily used to buffer the grid when energy sources are low, rather than as a primary source. For the first 20% to 40% of the electricity in a region to come from wind and solar, battery storage is not needed, Denholm said. When renewable penetration starts reaching closer to 50%, then battery storage becomes necessary. And building and deploying all those batteries will take time and money.
 

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Thermoradiative Diode Power leverages infrared radiation and night-sky cooling to harvest waste heat. Using MCT (mercury cadmium telluride) detectors with photovoltaics, it extends renewable energy generation after sunset, exploiting radiative cooling and low-power density.

Key Points

Technology using MCT infrared diodes to turn radiative Earth-to-space heat loss into electricity, aiding solar at night.

✅ MCT diodes radiate to cold sky, generating tiny current at 20 C

✅ Complements photovoltaics by harvesting post-sunset infrared flux

✅ Potential up to one-tenth solar output with further efficiency gains

Conventional solar technology soaks up rays of incoming sunlight to bump out a voltage. Strange as it seems, some materials are capable of running in reverse, producing power as they radiate heat back into the cold night sky environment.

A team of engineers in Australia has now demonstrated the theory in action, using the kind of technology commonly found in night-vision goggles to generate power, while other research explores electricity from thin air concepts under ambient humidity.

So far, the prototype only generates a small amount of power, and is probably unlikely to become a competitive source of renewable power on its own – but coupled with existing photovoltaics technology and thermal energy into electricity approaches, it could harness the small amount of energy provided by solar cells cooling after a long, hot day's work.

"Photovoltaics, the direct conversion of sunlight into electricity, is an artificial process that humans have developed in order to convert the solar energy into power," says Phoebe Pearce, a physicist from the University of New South Wales.

"In that sense, the thermoradiative process is similar; we are diverting energy flowing in the infrared from a warm Earth into the cold Universe."

By setting atoms in any material jiggling with heat, you're forcing their electrons to generate low-energy ripples of electromagnetic radiation in the form of infrared light, a principle also explored with carbon nanotube energy harvesters in ambient conditions.

As lackluster as this electron-shimmy might be, it still has the potential to kick off a slow current of electricity. All that's needed is a one-way electron traffic signal called a diode.

Made of the right combination of elements, a diode can shuffle electrons down the street as it slowly loses its heat to a cooler environment.

In this case, the diode is made of mercury cadmium telluride (MCT). Already used in devices that detect infrared light, MCT's ability to absorb mid-and long-range infrared light and turn it into a current is well understood.

What hasn't been entirely clear is how this particular trick might be used efficiently as an actual power source.

Warmed to around 20 degrees Celsius (nearly 70 degrees Fahrenheit), one of the tested MCT photovoltaic detectors generated a power density of 2.26 milliwatts per square meter.

Granted, it's not exactly enough to boil a jug of water for your morning coffee. You'd probably need enough MCT panels to cover a few city blocks for that small task.

But that's not really the point, either, given it's still very early days in the field, and there's potential for the technology to develop significantly further in the future.

"Right now, the demonstration we have with the thermoradiative diode is relatively very low power. One of the challenges was actually detecting it," says the study's lead researcher, Ned Ekins-Daukes.

"But the theory says it is possible for this technology to ultimately produce about 1/10th of the power of a solar cell."

At those kinds of efficiencies, it might be worth the effort weaving MCT diodes into more typical photovoltaic networks alongside thin-film waste heat solutions so that they continue to top up batteries long after the Sun sets.

To be clear, the idea of using the planet's cooling as a source of low-energy radiation is one engineers have been entertaining for a while now. Different methods have seen different results, all with their own costs and benefits, with low-cost heat-to-electricity materials also advancing in parallel.

Yet by testing the limits of each and fine-tuning their abilities to soak up more of the infrared bandwidth, we can come up with a suite of technologies and thermoelectric materials capable of wringing every drop of power out of just about any kind of waste heat.

"Down the line, this technology could potentially harvest that energy and remove the need for batteries in certain devices – or help to recharge them," says Ekins-Daukes.

"That isn't something where conventional solar power would necessarily be a viable option."

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