Wind farm planned near Groton

100% Clean Energy Targets drive renewable electricity, decarbonization, and cost savings through state policies, CCAs, RECs, and mandates, with timelines and interim goals that boost jobs, resilience, and public health across cities, counties, and utilities.

Key Points

Policies for cities and states to reach 100% clean power by set dates, using mandates, RECs, and interim goals.

✅ Define eligible clean vs renewable resources

✅ Mandate vs goal framework with enforcement

✅ Timelines with interim targets and escape clauses

“An enormous amount of authority still rests with the states for determining your energy future. So we can build these policies that will become a postcard from the future for the rest of the country,” said David Hochschild, chair of the California Energy Commission, speaking last week at a UCLA summit on state and local progress toward 100 percent clean energy.

According to a new report from the UCLA Luskin Center for Innovation, 13 states, districts and territories, as well as more than 200 cities and counties, with standout clean energy purchases by Southeast cities helping drive momentum, have committed to a 100 percent clean electricity target — and dozens of cities have already hit it.

This means that one of every three Americans, or roughly 111 million U.S. residents representing 34 percent of the population, live in a community that has committed to or has already achieved 100 percent clean electricity, including communities like Frisco, Colorado that have set ambitious targets.

“We’re going to look back on this moment as the moment when local action and state commitments began to push the entire nation toward this goal,” said J.R. DeShazo, director of the UCLA Luskin Center for Innovation.

Not all 100 percent targets are alike, however. The report notes that these targets vary based on 1) what resources are eligible, 2) how binding the 100 percent target is, and 3) how and when the target will be achieved.

These distinctions will carry a lot of weight as the policy discussion shifts from setting goals to actually meeting targets. They also have implications for communities in terms of health benefits, cost savings and employment opportunities.

100% targets come in different forms

One key attribute is whether a target is based on "renewable" or "clean" energy resources. Some 100 percent targets, like Hawaii’s and Rhode Island’s 2030 plan, are focused exclusively on renewable energy, or sources that cannot be depleted, such as wind, solar and geothermal. But most jurisdictions use the broader term “clean energy,” which can also include resources like large hydroelectric generation and nuclear power.

States also vary in their treatment of renewable energy certificates, used to track and assign ownership to renewable energy generation and use. Unbundled RECs allow for the environmental attributes of the renewable energy resource to be purchased separately from the physical electricity delivery.

The binding nature of these targets is also noteworthy. Seven states, as well as Puerto Rico and the District of Columbia, have passed 100 percent clean energy transition laws. Of the jurisdictions that have passed 100 percent legislation, all but one specifies that the target is a “mandate,” according to the report. Nevada is the only state to call the target a “goal.”

Governors in four other states have signed executive orders with 100 percent clean energy goals.

Target timelines also vary. Washington, D.C. has set the most ambitious target date, with a mandate to achieve 100 percent renewable electricity by 2032. Other states and cities have set deadline years between 2040 and 2050. All "100 percent" state laws, and some city and county policies, also include interim targets to keep clean energy deployment on track.

In addition, some locations have included some form of escape clause. For instance, Salt Lake City, which last month passed a resolution establishing a goal of powering the county with 100 percent clean electricity by 2030, included “exit strategies” in its policy in order to encourage stakeholder buy-in, said Mayor Jackie Biskupski, speaking last week at the UCLA summit.

“We don’t think they’ll get used, but they’re there,” she said.

Other locales, meanwhile, have decided to go well beyond 100 percent clean electricity. The State of California and 44 cities have set even more challenging targets to also transition their entire transportation, heating and cooling sectors to 100 percent clean energy sources, and proposals like requiring solar panels on new buildings underscore how policy can accelerate progress across sectors.

Businesses are simultaneously electing to adopt more clean and renewable energy. Six utilities across the United States have set their own 100 percent clean or carbon-free electricity targets. UCLA researchers did not include populations served by these utilities in their analysis of locations with state and city 100 percent clean commitments.

“We cannot wait”

All state and local policies that require a certain share of electricity to come from renewable energy resources have contributed to more efficient project development and financing mechanisms, which have supported continued technology cost declines and contributed to a near doubling of renewable energy generation since 2008.

Many communities are switching to clean energy in order to save money, now that the cost calculation is increasingly in favor of renewables over fossil fuels, as more jurisdictions get on the road to 100% renewables worldwide. Additional benefits include local job creation, cleaner air and electricity system resilience due to greater reliance on local energy resources.

Another major motivator is climate change. The electricity sector is responsible for 28 percent of U.S. greenhouse gas emissions, second only to transportation. Decarbonizing the grid also helps to clean up the transportation sector as more vehicles move to electricity as their fuel source.

“The now-constant threat of wildfires, droughts, severe storms and habitat loss driven by climate change signals a crisis we can no longer ignore,” said Carla Peterman, senior vice president of regulatory affairs at investor-owned utility Southern California Edison. “We cannot wait and we should not wait when there are viable solutions to pursue now.”

Prior to joining SCE on October 1, Peterman served as a member of the California Public Utilities Commission, which implements and administers renewable portfolio standard (RPS) compliance rules for California’s retail sellers of electricity. California’s target requires 60 percent of the state’s electricity to come from renewable energy resources by 2030, and all the state's electricity to come from carbon-free resources by 2045.  

How CCAs are driving renewable energy deployment

One way California communities are working to meet the state’s ambitious targets is through community-choice aggregation, especially after California's near-100% renewable milestone underscored what's possible, via which cities and counties can take control of their energy procurement decisions to suit their preferences. Investor-owned utilities no longer purchase energy for these jurisdictions, but they continue to operate the transmission and distribution grid for all electricity users.                           

A second paper released by the Luskin Center for Innovation in recent days examines how community-choice aggregators are affecting levels of renewable energy deployment in California and contributing to the state’s 100 percent target.

The paper finds that 19 CCAs have launched in California since 2010, growing to include more than 160 towns, cities and counties. Of those communities, 64 have a 100 percent renewable or clean energy policy as their default energy program.

Because of these policies, the UCLA paper finds that “CCAs have had both direct and indirect effects that have led to increases in the clean energy sold in excess of the state’s RPS.”

From 2011 to 2018, CCAs directly procured 24 terawatt-hours of RPS-eligible electricity, 11 TWh of which have been voluntary or in excess of RPS compliance, according to the paper.

The formation of CCAs has also had an indirect effect on investor-owned utilities. As customers have left investor-owned utilities to join CCAs, the utilities have been left holding contracts for more renewable energy than they need to comply with California’s clean energy targets, amid rising solar and wind curtailments that complicate procurement decisions. UCLA researchers estimate that this indirect effect of CCA formation has left IOUs holding 13 terawatt-hours in excess of RPS requirements.

The paper concludes that CCAs have helped to accelerate California’s ability to meet state renewable energy targets over the past decade. However, the future contributions of CCAs to the RPS are more uncertain as communities make new power-purchasing decisions and utilities seek to reduce their excess renewable energy contracts.

“CCAs offer a way for communities to put their desire for clean energy into action. They're growing fast in California, one of only eight states where this kind of mechanism is allowed," said UCLA's Kelly Trumbull, an author of the report. "State and federal policies could be reformed to better enable communities to meet local demand for renewable energy.”

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Site C Dam Update outlines hydroelectric budget overruns, geotechnical risks, COVID-19 construction delays, BC Hydro timelines, cancellation costs, and First Nations treaty rights concerns affecting renewable energy, ratepayers, and Peace Valley impacts.

Key Points

Overview of Site C costs, delays, geotechnical risks, and concerns shaping BC Hydro hydroelectric plans.

✅ Cost to cancel estimated at least $10B

✅ Final budget now about $16B; completion pushed to 2025

✅ COVID-19 and geotechnical risks drove delays and redesigns

The cost to cancel a massive B.C. energy development project would be at least $10 billion, provincial officials revealed in an update on the future of Site C.

Thus the project will go ahead, Premier John Horgan and Energy Minister Bruce Ralston announced Friday, but with an increased budget and timeline.

Horgan and Ralston spoke at a news conference in Victoria about the findings of a status report into the hydroelectric dam project in northeastern B.C.

Peter Milburn, former deputy finance minister, finished the report earlier this year, but the findings were not initially made public.

$10B more than initial estimate
On Friday, it was announced that the project's final price tag has once again ballooned by billions of dollars.

Site C was initially estimated to cost $6 billion, and the first approved budget, back in 2014, was $8.775 billion. The budget increased to $10.8 billion in 2018.

But the latest update suggests it will cost about $16 billion in total.

And, in addition to a higher budget, the date of completion has been pushed back to 2025 – a year later than the initial target.

Among the reasons for the revisions, according to the province, is the impact of COVID-19. While officials did not get into details, there have been multiple cases of the disease publicly reported at Site C work camps.

Additionally, fewer workers were permitted on site to allow for physical distancing, and construction was scaled back.

Also cited as a cause for the increased cost were "unforeseeable" geotechnical issues at the site, which required installation of an enhanced drainage system.

Speaking to reporters Friday, the premier deflected blame.

“Managing the contract the BC Liberals signed has been difficult because it transfers the vast majority of the geotechnical risk back to BC Hydro,” said Horgan.

Former Premier Christy Clark vowed to get the project to a point of no return, and in 2017 the NDP decided to continue with the project because of the cost of cancelling it.

The Liberals now say the clean energy project should continue, but deny they shoulder any of the blame.

“Someone has to take ownership – and it's got to be government in power,” said MLA Tom Shypitka, BC Liberal critic for energy. 

There are also several reviews underway, including how to change contractor schedules to reflect delays and potential cost impacts from COVID-19, and how to keep the work environment safe during the pandemic.

A total of 17 recommendations were made in Milburn's report, all of which have been accepted by BC Hydro and the province.

Among these recommendations is a restructured project assurance board with a focus on skill-specific membership and autonomy from BC Hydro.

Cost of cancelling the project
The report looked into whether it would be better to scrap the project altogether, but the cost of cancelling it at this point would be at least $10 billion, Horgan and Ralston said.

That cost does not include replacing lost energy and capacity that Site C's electricity would have provided, according to the province.

A study conducted in 2019 suggested B.C. will need to double its electricity production by 2055, especially as drought conditions are forcing BC Hydro to adapt power generation. 

The NDP government says the cost to ratepayers of cancelling the project would be $216 a year for 10 years. Going forward will still have a cost, but instead, that payment will be split over more than 70 years, the estimated lifetime of Site C, meaning BC Hydro customers will pay about $36 more a year once the site goes live, the NDP says, even as cryptocurrency mining raises questions about electricity use.

“We will not put jobs at risk; we will not shock people's hydro bills,” said Horgan.

"Our government has taken this situation very seriously, and with the advice of independent experts guiding us, I am confident in the path forward for Site C," Ralston said.

"B.C. needs more renewable energy to bridge the electricity gap with Alberta and electrify our economy, transition away from fossil fuels and meet our climate targets."

The minister said the site is currently employing about 4,500 people.

Arguments against Site C
While there are benefits to the project, there has also been vocal opposition.

In a statement released following the announcement that the project would go ahead, the Union of B.C. Indian Chiefs suggested the decision violated the premier's commitment to a UN declaration.

"The Site C dam has never had the free, prior and informed consent of all impacted First Nations, and proceeding with the project is a clear infringement of the treaty rights of the West Moberly First Nation," the UBCIC's secretary treasurer said.

Kukpi7 Judy Wilson said the UN's Committee on the Elimination of Racial Discrimination has called for a suspension of the project until it has the consent of Indigenous peoples.

"B.C. did not even attempt to engage First Nations about the safety risks associated with the stability of the dam in the recent reviews," she said.

"It is unfathomable that such clear human rights violations are somehow OK by this government."

Chief Roland Wilson of the West Moberly First Nation said he was disappointed the province didn’t consult his and other communities prior to making this announcement. In an interview with CTV News, he said he was offered an opportunity to join a call this morning.

“We signed a treaty in 1814,” he said. “Our treaty rights are being trampled on.”

Wilson said his nation has ongoing concerns about safety issues and the plans to flood the Peace Valley. West Moberly is in a bitter court battle with the province.

At the BC Legislature, Green Party Leader Sonia Furstenau slammed the government’s decision.

“It is an astonishingly terrible business case in any circumstances, but considering that we lose the agricultural land, the biodiversity, the traditional treaty lands of Treaty 8, this is particularly catastrophic,” she told reporters.

She went on to accuse the NDP government of keeping bad news from the public. She alleged the NDP knew of serious problems before last fall’s unscheduled election, but chose not to release information.

Prior to the decision former BC Hydro president and a former federal fisheries minister are among those who added their voices to calls to halt work on the dam.

They were among 18 Canadians who wrote an open letter to the province calling for an independent team of experts to explore geotechnical problems at the site.

In the letter, signed in September, the group that also included Grand Chief Stewart Phillip of the UBCIC wrote that going ahead would be a "costly and potentially catastrophic mistake." 

According to Friday's update, independent experts have confirmed the site is safe, though improvements have been recommended to enhance oversight and risk management.

Earlier in the project, a B.C. First Nation claimed it was a $1-billion treaty violation, though an agreement was reached in 2020 after the province promised to improve land management and restore traditional place names in areas of cultural significance.

The Prophet River First Nation will also receive payments while the site is operating, and some Crown land will be transferred to the nation as part of the agreement. 

Additionally, residents of a tiny community not far from the site is suing the province over two slow-moving landslides they claim caused property values to plummet.

Nearly three dozen residents of Old Fort are behind the allegations of negligence and breach of their charter right to security of person. The claim is tied to two landslides, in 2018 and 2020, that the group alleges were caused by ground destabilization from construction related to Site C.

One of the landslides damaged the only road into the community, leaving residents under evacuation for a month.

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Manus Island Naval Base strengthens US-Australia-PNG cooperation at Lombrum, near the South China Sea, bolstering sovereignty, maritime rights, and Pacific security amid APEC talks, infrastructure investment, and Belt and Road competition.

Key Points

A US-Australia-PNG facility at Lombrum to bolster Pacific security and protect maritime rights across the region.

✅ Shared by US, Australia, and PNG at Lombrum on Manus Island

✅ Near South China Sea, reinforcing maritime security and access

✅ Counters opaque lending, aligns with free trade and infrastructure

Scott Morrison has caught himself bang in the middle of escalating tensions between the United States and China.

The US and Australia will share a naval base in the north end of Papua New Guinea on Manus Island, creating another key staging point close to the contested South China Sea.

“The United States will partner with Papua New Guinea and Australia on their joint initiative at Lombrum Naval Base,” US Vice President Mike Pence said.

“We will work with these two nations to protect sovereignty and maritime rights in the Pacific Islands. ”

At an Asia Pacific Economic Cooperation meeting in Port Moresby on Saturday, Mr Morrison urged nations to embrace free trade and avoid “unsustainable debt”, as the Philippines' clean energy commitment also featured in discussions.

He confirmed the US and Australia will share an expanded naval base on Manus Island, as the US ramped up rhetoric against China.

Mr Pence quoted President Donald Trump in his speech following Chinese President Xi Jinping, even as a Biden energy agenda is seen by some as better for Canada.

“We have great respect for President Xi and respect for China. But in the president’s words, China’s taken advantage of the United States for many, many years,” he said.

“And those days are over.”

His speech was met with stony silence from the Chinese delegation, after President Xi had reassured leaders his Belt and Road Initiative was not a debt trap.

China has also been at loggerheads with the United States over its territorial ambitions in the Pacific, encapsulated by Xi’s Belt and Road Initiative.

Unveiled in 2013, the Belt and Road initiative aims to bolster a sprawling network of land and sea links with Southeast Asia, Central Asia, the Middle East, Europe and Africa.

China’s efforts to win friends in the resource-rich Pacific have been watched warily by the traditionally influential powers in the region — Australia and the United States.

“It is not designed to serve any hidden geopolitical agenda,” President Xi said on Saturday.

“Nor is it a trap, as some people have labelled it.”

But Mr Pence said loans to developing countries were too often opaque and encouraged nations to look to the US instead of China.

“Too often they come with strings attached and lead to staggering debt,” he said in his speech.

“Do not accept foreign debt that could compromise your sovereignty.

“Just like America, always put your country first.”

Mr Morrison committed Australia to look to the Pacific nations and on Sunday he will host an informal BBQ with Pacific leaders, amid domestic moves like Western Australia's electricity bill credit for households.

He also announced a joint partnership with Japan and the US to fund infrastructure around the region, while at home debates over an electricity market overhaul continue.

On the back of Mr Morrison’s defence of free trade at the summit, Australian Trade Minister Simon Birmingham said he was confident the US was interested in an open trading environment in the long run, with parallel discussions such as a U.S.-Canada energy partnership underscoring regional economic ties.

Australia is hoping the US will, in the end, take a similar approach to its trade dispute with China as it did with its tariff threats against Mexico and Canada, as cross-border negotiations like the Columbia River Treaty continue to shape U.S.-Canada ties.

“Ultimately, they laid down arms, they walked away from threats, and they struck a new trade deal that ensures trade continues in that North American bloc,” Mr Birmingham told ABC TV on Sunday.

“We hope the same will happen in relation to China.”

Four countries including the US have signed up to an effort to bring electricity to 70 per cent of Papua New Guinea’s people by 2030.

Australia, Japan, the US and New Zealand on Sunday signed an agreement to work with Papua New Guinea’s government on electrification.

It’s the latest sign of great power rivalry in the South Pacific, where China is vying with the US and its allies for influence.

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Costa Rica Renewable Energy Record highlights 99.99% clean power in May 2019, driven by hydropower, wind, solar, geothermal, and biomass, enabling ICE REM electricity exports and reduced rates from optimized generation totaling 984.19 GWh.

Key Points

May 2019 benchmark: Costa Rica generated 99.99% of 984.19 GWh from renewables, shifting from imports to regional exports.

✅ 99.99% renewable share across hydro, wind, solar, geothermal, biomass

✅ 984.19 GWh generated; ICE suspended imports and exported via REM

✅ Geothermal output increased to offset dry-season hydropower variability

During the whole month of May 2019, Costa Rica generated a total of 984.19 gigawatt hours of electricity, the highest in the country’s history. What makes this feat even more impressive is the fact that 99.99% of this energy came from a portfolio of renewable sources such as hydropower, wind, biomass, solar, and geothermal.

With such a high generation rate, the state power company Instituto Costariccense de Electricidad (ICE) were able to suspend energy imports from the first week of May and shifted to exports, while U.S. renewable electricity surpassed coal in 2022 domestically. To date, the power company continues to sell electricity to the Regional Electricity Market (REM) which generates revenues and is likely to reduce local electricity rates, a trend echoed in places like Idaho where a vast majority of electricity comes from renewables.

The record-breaking power generation was made possible by optimization of the country’s renewable sources, much as U.S. wind capacity surpassed hydro capacity at the end of 2016 to reshape portfolios. As the period coincided with the tail end of the dry season, the geothermal quota had to be increased.

Costa Rica remains a leader in renewable power generation, whereas U.S. wind generation has become the most-used renewable source in recent years. In 2015, more than 98% of the country’s electrical generation came from renewable sources, while U.S. renewables hit a record 28% in April in one recent benchmark. Through the years, this figure has remained fairly constant despite dry bouts caused by the El Niño phenomenon, and U.S. solar generation also continued to rise.

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Thermoelectric Materials convert waste heat into electricity via the Seebeck effect; quantum computations and semiconductors accelerate discovery, enabling clean energy, higher efficiency, and scalable heat-to-power conversion from abundant, non-toxic, cost-effective compounds.

Key Points

Thermoelectric materials turn waste heat into electricity via the Seebeck effect, improving energy efficiency.

✅ Convert waste heat to electricity via the Seebeck effect

✅ Quantum computations rapidly identify high-performance candidates

✅ Target efficient, low-thermal-conductivity, non-toxic, abundant compounds

The need to transition to clean energy is apparent, urgent and inescapable. We must limit Earth’s rising temperature to within 1.5 C to avoid the worst effects of climate change — an especially daunting challenge in the face of the steadily increasing global demand for energy and the need for reliable clean power, with concepts that can generate electricity at night now being explored worldwide.

Part of the answer is using energy more efficiently. More than 72 per cent of all energy produced worldwide is lost in the form of heat, and advances in turning thermal energy into electricity could recover some of it. For example, the engine in a car uses only about 30 per cent of the gasoline it burns to move the car. The remainder is dissipated as heat.

Recovering even a tiny fraction of that lost energy would have a tremendous impact on climate change. Thermoelectric materials, which convert wasted heat into useful electricity, can help, especially as researchers pursue low-cost heat-to-electricity materials for scalable deployment.

Until recently, the identification of these materials had been slow. My colleagues and I have used quantum computations — a computer-based modelling approach to predict materials’ properties — to speed up that process and identify more than 500 thermoelectric materials that could convert excess heat to electricity, and help improve energy efficiency.

Making great strides towards broad applications
The transformation of heat into electrical energy by thermoelectric materials is based on the “Seebeck effect.” In 1826, German physicist Thomas Johann Seebeck observed that exposing the ends of joined pieces of dissimilar metals to different temperatures generated a magnetic field, which was later recognized to be caused by an electric current.

Shortly after his discovery, metallic thermoelectric generators were fabricated to convert heat from gas burners into an electric current. But, as it turned out, metals exhibit only a low Seebeck effect — they are not very efficient at converting heat into electricity.

In 1929, the Russian scientist Abraham Ioffe revolutionized the field of thermoelectricity. He observed that semiconductors — materials whose ability to conduct electricity falls between that of metals (like copper) and insulators (like glass) — exhibit a significantly higher Seebeck effect than metals, boosting thermoelectric efficiency 40-fold, from 0.1 per cent to four per cent.

This discovery led to the development of the first widely used thermoelectric generator, the Russian lamp — a kerosene lamp that heated a thermoelectric material to power a radio.

Are we there yet?
Today, thermoelectric applications range from energy generation in space probes to cooling devices in portable refrigerators, and include emerging thin-film waste-heat harvesters for electronics as well. For example, space explorations are powered by radioisotope thermoelectric generators, converting the heat from naturally decaying plutonium into electricity. In the movie The Martian, for example, a box of plutonium saved the life of the character played by Matt Damon, by keeping him warm on Mars.

In the 2015 film, The Martian, astronaut Mark Watney (Matt Damon) digs up a buried thermoelectric generator to use the power source as a heater.

Despite this vast diversity of applications, wide-scale commercialization of thermoelectric materials is still limited by their low efficiency.

What’s holding them back? Two key factors must be considered: the conductive properties of the materials, and their ability to maintain a temperature difference, as seen in nighttime electricity from cold concepts, which makes it possible to generate electricity.

The best thermoelectric material would have the electronic properties of semiconductors and the poor heat conduction of glass. But this unique combination of properties is not found in naturally occurring materials. We have to engineer them, drawing on advances such as carbon nanotube energy harvesters to guide design choices.

Searching for a needle in a haystack
In the past decade, new strategies to engineer thermoelectric materials have emerged due to an enhanced understanding of their underlying physics. In a recent study in Nature Materials, researchers from Seoul National University, Aachen University and Northwestern University reported they had engineered a material called tin selenide with the highest thermoelectric performance to date, nearly twice that of 20 years ago. But it took them nearly a decade to optimize it.

To speed up the discovery process, my colleagues and I have used quantum calculations to search for new thermoelectric candidates with high efficiencies. We searched a database containing thousands of materials to look for those that would have high electronic qualities and low levels of heat conduction, based on their chemical and physical properties. These insights helped us find the best materials to synthesize and test, and calculate their thermoelectric efficiency.

We are almost at the point where thermoelectric materials can be widely applied, but first we need to develop much more efficient materials. With so many possibilities and variables, finding the way forward is like searching for a tiny needle in an enormous haystack.

Just as a metal detector can zero in on a needle in a haystack, quantum computations can accelerate the discovery of efficient thermoelectric materials. Such calculations can accurately predict electron and heat conduction (including the Seebeck effect) for thousands of materials and unveil the previously hidden and highly complex interactions between those properties, which can influence a material’s efficiency.

Large-scale applications will require themoelectric materials that are inexpensive, non-toxic and abundant. Lead and tellurium are found in today’s thermoelectric materials, but their cost and negative environmental impact make them good targets for replacement.

Quantum calculations can be applied in a way to search for specific sets of materials using parameters such as scarcity, cost and efficiency, and insights can even inform exploratory devices that generate electricity out of thin air in parallel fields. Although those calculations can reveal optimum thermoelectric materials, synthesizing the materials with the desired properties remains a challenge.

A multi-institutional effort involving government-run laboratories and universities in the United States, Canada and Europe has revealed more than 500 previously unexplored materials with high predicted thermoelectric efficiency. My colleagues and I are currently investigating the thermoelectric performance of those materials in experiments, and have already discovered new sources of high thermoelectric efficiency.

Those initial results strongly suggest that further quantum computations can pinpoint the most efficient combinations of materials to make clean energy from wasted heat and the avert the catastrophe that looms over our planet.

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Near-Field Thermophotovoltaics captures radiated energy across a nanoscale gap, using thin-film photovoltaic cells and indium gallium arsenide to boost power density and efficiency, enabling compact Army portable power from emitters via radiative heat transfer.

Key Points

A nanoscale TPV method capturing near-field photons for higher power density at lower emitter temperatures.

✅ Nanoscale gap boosts radiative transfer and usable photon flux

✅ Thin-film InGaAs cells recycle sub-band-gap photons via reflector

✅ Achieved ~5 kW/m2 power density with higher efficiency

With the addition of sensors and enhanced communication tools, providing lightweight, portable power has become even more challenging, with concepts such as power from falling snow illustrating how diverse new energy-harvesting approaches are. Army-funded research demonstrated a new approach to turning thermal energy into electricity that could provide compact and efficient power for Soldiers on future battlefields.

Hot objects radiate light in the form of photons into their surroundings. The emitted photons can be captured by a photovoltaic cell and converted to useful electric energy. This approach to energy conversion is called far-field thermophotovoltaics, or FF-TPVs, and has been under development for many years; however, it suffers from low power density and therefore requires high operating temperatures of the emitter.

The research, conducted at the University of Michigan and published in Nature Communications, demonstrates a new approach, where the separation between the emitter and the photovoltaic cell is reduced to the nanoscale, enabling much greater power output than what is possible with FF-TPVs for the same emitter temperature.

This approach, which enables capture of energy that is otherwise trapped in the near-field of the emitter is called near-field thermophotovoltaics or NF-TPV and uses custom-built photovoltaic cells and emitter designs ideal for near-field operating conditions, alongside emerging smart solar inverters that help manage conversion and delivery.

This technique exhibited a power density almost an order of magnitude higher than that for the best-reported near-field-TPV systems, while also operating at six-times higher efficiency, paving the way for future near-field-TPV applications, including remote microgrid deployments in extreme environments, according to Dr. Edgar Meyhofer, professor of mechanical engineering, University of Michigan.

"The Army uses large amounts of power during deployments and battlefield operations and must be carried by the Soldier or a weight constrained system," said Dr. Mike Waits, U.S. Army Combat Capabilities Development Command's Army Research Laboratory. "If successful, in the future near-field-TPVs could serve as more compact and higher efficiency power sources for Soldiers as these devices can function at lower operating temperatures than conventional TPVs."

The efficiency of a TPV device is characterized by how much of the total energy transfer between the emitter and the photovoltaic cell is used to excite the electron-hole pairs in the photovoltaic cell, where insights from near-light-speed conduction research help contextualize performance limits in semiconductors. While increasing the temperature of the emitter increases the number of photons above the band-gap of the cell, the number of sub band-gap photons that can heat up the photovoltaic cell need to be minimized.

"This was achieved by fabricating thin-film TPV cells with ultra-flat surfaces, and with a metal back reflector," said Dr. Stephen Forrest, professor of electrical and computer engineering, University of Michigan. "The photons above the band-gap of the cell are efficiently absorbed in the micron-thick semiconductor, while those below the band-gap are reflected back to the silicon emitter and recycled."

The team grew thin-film indium gallium arsenide photovoltaic cells on thick semiconductor substrates, and then peeled off the very thin semiconductor active region of the cell and transferred it to a silicon substrate, informing potential interfaces with home battery systems for distributed use.

All these innovations in device design and experimental approach resulted in a novel near-field TPV system that could complement distributed resources in virtual power plants for resilient operations.

"The team has achieved a record ~5 kW/m2 power output, which is an order of magnitude larger than systems previously reported in the literature," said Dr. Pramod Reddy, professor of mechanical engineering, University of Michigan.

Researchers also performed state-of-the-art theoretical calculations to estimate the performance of the photovoltaic cell at each temperature and gap size, informing hybrid designs with backup fuel cell solutions that extend battery life, and showed good agreement between the experiments and computational predictions.

"This current demonstration meets theoretical predictions of radiative heat transfer at the nanoscale, and directly shows the potential for developing future near-field TPV devices for Army applications in power and energy, communication and sensors," said Dr. Pani Varanasi, program manager, DEVCOM ARL that funded this work.

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