Regulators consider Duke’s “Save-a-Watt” plan

California Grid Transition drives decarbonization with renewable energy, EV charging, microgrids, and energy storage, while tackling wildfire risk, aging infrastructure, and cybersecurity threats to build grid resilience and reliability across a rapidly electrifying economy.

Key Points

California Grid Transition is the statewide shift to renewables, storage, EVs, and resilient, secure infrastructure.

✅ Integrates solar, wind, storage, and demand response at scale

✅ Expands microgrids and DERs to enhance reliability and resilience

✅ Addresses wildfire, aging assets, and cybersecurity risks

Gretchen Bakke thinks a lot about power—the kind that sizzles through a complex grid of electrical stations, poles, lines and transformers, keeping the lights on for tens of millions of Californians who mostly take it for granted.

They shouldn’t, says Bakke, who grew up in a rural California town regularly darkened by outages. A cultural anthropologist who studies the consequences of institutional failures, she says it’s unclear whether the state’s aging electricity network and its managers can handle what’s about to hit it, as U.S. blackout risks continue to mount.

California is casting off fossil fuels to become something that doesn’t yet exist: a fully electrified state of 40 million people. Policies are in place requiring a rush of energy from renewable sources such as the sun and wind and calling for millions of electric cars that will need charging—changes that will tax a system already fragile, unstable and increasingly vulnerable to outside forces.

“There is so much happening, so fast—the grid and nearly everything about energy is in real transition, and there’s so much at stake,” said Bakke, who explores these issues in a book titled simply, “The Grid.”

The state’s task grew more complicated with this week’s announcement that Pacific Gas and Electric, which provides electricity for more than 5 million customer accounts, intends to file for bankruptcy in the face of potentially crippling liabilities from wildfires. But the reshaping of California’s energy future goes far beyond the woes of a single company.

The 19th-century model of one-way power delivery from utility companies to customers is being reimagined. Major utilities—and the grid itself—are being disrupted by rooftops paved with solar panels and the rise of self-sufficient neighborhood mini-grids. Whole cities and counties are abandoning big utilities and buying power from wholesalers and others of their choosing.

With California at the forefront of a new energy landscape, officials are racing to design a future that will not just reshape power production and delivery but also dictate how we get around and how our goods are made. They’re debating how to manage grid defectors, weighing the feasibility of an energy network that would expand to connect and serve much of the West and pondering how to appropriately regulate small power producers.

“We are in the depths of the conversation,” said Michael Picker, president of the state Public Utilities Commission, who cautions that even as the system is being rebooted, like repairing a car while driving in practice, there’s no real plan for making it all work.

Such transformation is exceedingly risky and potentially costly. California still bears the scars of having dropped its regulatory reins some 20 years ago, leaving power companies to bilk the state of billions of dollars it has yet to completely recover. And utility companies will undoubtedly pass on to their customers the costs of grid upgrades to defend against natural and man-made threats.

Some weaknesses are well known—rodents and tree limbs, for example, are common culprits in power outages, even as longer, more frequent outages afflict other parts of the U.S. A gnawing squirrel squeezed into a transformer on Thanksgiving Day three years ago, shutting off power to parts of Los Angeles International Airport. The airport plans to spend $120 million to upgrade its power plant.

But the harsh effects of climate change expose new vulnerabilities. Rising seas imperil coastal power plants. Electricity infrastructure is both threatened by and implicated in wildfires. Picker estimates that utility operations are related to one in 10 wildland fires in California, which can be sparked by aging equipment and winds that send tree branches crashing into power lines, showering flammable landscapes with sparks.

California utilities have been ordered to make their lines and equipment more fire-resistant as they’re increasingly held accountable for blazes they cause. Pacific Gas and Electric reported problems with some of its equipment at a starting point of California’s deadliest wildfire, which killed at least 86 people in November in the town of Paradise. The cause of the fire is under investigation.

New and complex cyber threats are more difficult to anticipate and even more dangerous. Computer hackers, operating a world away, can—and have—shut down electricity systems, toggling power on and off at will, and even hijacked the computers of special teams dispatched to restore control.

Thomas Fanning, CEO of Southern Co., one of the country’s largest utilities, recently disclosed that his teams have fended off multiple attempts to hack a nuclear power plant the firm operates. He called grid hacking “the most important under-reported war in American history.”

However, if you’ve got what seems like an insoluble problem requiring a to-the-studs teardown and innovative rebuild, California is a good place to start. After all, the first electricity grid was built in San Francisco in 1879, three years before Thomas Edison’s power station in New York City. (Edison’s plant burned to the ground a decade later.)

California’s energy-efficiency regulations have helped reduce statewide energy use, which peaked a decade ago and is on the decline, somewhat easing pressure on the grid. The major utilities are ahead of schedule in meeting their obligation to obtain power from renewable sources.

California’s universities are teaming with national research labs to develop cutting-edge solutions for storing energy produced by clean sources. California is fortunate in the diversity of its energy choices: hydroelectric dams in the north, large-scale solar operations in the Mojave Desert to the east, sprawling windmill farms in mountain passes and heat bubbling in the Geysers, the world’s largest geothermal field north of San Francisco. A single nuclear-power plant clings to the coast near San Luis Obispo, but it will be shuttered in 2025.

But more renewable energy, accessible at the whims of weather, can throw the grid off balance. Renewables lack the characteristic that power planners most prize: dispatchability, ready when called on and turned off when not immediately needed. Wind and sun don’t behave that way; their power is often available in great hunks—or not at all, as when clouds cover solar panels or winds drop.

In the case of solar power, it is plentiful in the middle of the day, at a time of low demand. There’s so much in California that most days the state pays its neighbors to siphon some off,  lest the excess impede the grid’s constant need for balance—for a supply that consistently equals demand.

So getting to California’s new goals of operating on 100 percent clean energy by 2045 and having 5 million electric vehicles within 12 years will require a shift in how power is acquired and managed. Consumers will rely more heavily on battery storage, whose efficiency must improve to meet that demand.

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BC Hydro COVID-19 Bill Relief offers pandemic support with bill credits, rate cuts, and deferred payments for residential, small business, and industrial customers across B.C., easing utilities costs during COVID-19 economic hardship.

Key Points

COVID-19 bill credits, a rate cut, and deferred payments for eligible B.C. homes, small businesses, and industrial customers.

✅ Non-repayable credits equal to 3 months of average bills.

✅ Small businesses closed can skip bills for three months.

✅ Large industry may defer 50% of electricity costs.

B.C. residents who have lost their jobs or had their wages cut will get a three-month break on BC Hydro bills, while small businesses, amid commercial consumption plummets during COVID-19, are also eligible to apply for similar relief.

Premier John Horgan said Wednesday the credit for residential customers will be three times a household’s average monthly bill over the past year and does not have to be repaid as part of the government’s support package during the COVID-19 pandemic, as BC Hydro demand down 10% highlights the wider market pressures.

He said small businesses that are closed will not have to pay their power bills for three months, and in Ontario an Ontario COVID-19 hydro rebate complemented similar relief, and large industrial customers, including those operating mines and pulp mills, can opt to have 50 per cent of their electricity costs deferred, though a deferred costs report warned of long-term liabilities.

BC Hydro rates will be cut for all customers by one per cent as of April 1, a move similar to Ontario 2021 rate reductions that manufacturers supported lower rates at the time, after the B.C. Utilities Commission provided interim approval of an application the utility submitted last August.

Eligible residential customers can apply for bill relief starting next week and small business applications will be accepted as of April 14, while staying alert to BC Hydro scam attempts during this period, with the deadline for both categories set at June 30.

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U.S. Wind Generation surpassed hydroelectric output in 2019, EIA data shows, becoming the top renewable electricity source, driven by PTC incentives, expanded capacity, and utility-scale projects across states, boosting the national electricity mix.

Key Points

U.S. Wind Generation is the nation's top renewable, surpassing hydro as EIA-tracked capacity grows under PTC incentives.

✅ EIA: wind topped hydro in 2019, over 300M MWh generated

✅ PTC credits spurred growth in utility-scale wind projects

✅ 103 GW installed; 77% added in the last decade

Last year saw wind power surging in the U.S. to overtake hydroelectric generation for the first time, according to data from the U.S. Energy Information Administration (EIA).

Released Wednesday, the figures from the EIA’s “Electric Power Monthly” report show that yearly wind generation hit a little over 300 million megawatt hours (MWh) in 2019. This was roughly 26 million MWh more than hydroelectric production.

Wind now represents the “most-used renewable electricity generation source” in the U.S., the EIA said, and renewables hit a 28% monthly record in April in later data.

Overall, total renewable electricity generation — which includes sources such as solar's 4.7% share in 2022 as one example, geothermal and landfill gas — at utility scale facilities hit more than 720 million MWh in 2019, compared to just under 707 million MWh in 2018. To put things in perspective, generation from coal came to more than 966 million MWh in 2019, while renewables surpassed coal in 2022 nationally according to later analyses.

According to the EIA’s “Today in Energy” briefing, which was also published Wednesday, generation from wind power has grown “steadily” across the last decade, and by 2020, renewables became the second-most prevalent source in the U.S. power mix.

This, it added, was partly down to the extension of the Production Tax Credit, or PTC, amid favorable government plans supporting solar and wind growth. According to the EIA, the PTC is a system which gives operators a tax credit per kilowatt hour of renewable electricity production. It applies for the first 10 years of a facility’s operation.

At the end of 2019, the country was home to 103 gigawatts (GW) of wind capacity, with 77% of this being installed in the last decade, and wind capacity surpassed hydro in 2016 according to industry data. The U.S. is home 80 GW of hydroelectric capacity, according to the EIA.

“The past decade saw a steady increase in wind capacity across the country and we capped the decade with a monumental achievement for the industry in reaching more than 100 GW,” Tom Kiernan, the American Wind Energy Association’s CEO, said in a statement issued Thursday.

“And more wind energy is coming, as the industry is well into investing $62 billion in new projects over the next few years that put us on the path to achieving 20 percent of the nation’s electricity mix in 2030,” Kiernan went on to state.

“As a result, wind is positioned to remain the largest renewable energy generator in the country for the foreseeable future.”

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Seattle City Light Energy Efficiency Programs help 93,000 residents cut bills with rebates, home energy audits, weatherization, conservation workshops, and sustainability tools, reducing electricity use and greenhouse gas emissions across Seattle communities.

Key Points

They are utility programs that lower electricity use and bills via rebates, energy audits, and weatherization services.

✅ Rebates for ENERGY STAR appliances and efficient HVAC upgrades

✅ Free audits with tailored recommendations and savings roadmaps

✅ Weatherization aid for low-income households and renters

In a noteworthy achievement for both residents and the environment, Seattle City Light has successfully helped more than 93,000 customers reduce their electricity bills through various energy efficiency programs. This initiative not only alleviates financial burdens for many households, amid concerns about pandemic-era shut-offs that heightened energy insecurity, but also aligns with the city’s commitment to sustainability and responsible energy use.

The Drive for Energy Efficiency

Seattle City Light, the city’s publicly owned electric utility, has been at the forefront of promoting energy efficiency among its customers. Recognizing that energy costs can strain household budgets, the utility has developed a range of programs and tracks emerging utility rate designs to help residents lower their energy consumption and, consequently, their bills.

One of the main aspects of this initiative is the emphasis on education and awareness. By providing customers with tools and resources to understand their energy usage, City Light empowers residents to make informed choices that can lead to substantial savings and prepare for power outage events as well.

Key Programs and Services

Seattle City Light offers a variety of programs aimed at reducing energy consumption. Among the most popular are:

1. Energy Efficiency Rebates: Customers can receive rebates for purchasing energy-efficient appliances, such as refrigerators, washing machines, and HVAC systems. These appliances are designed to consume less electricity than traditional models, resulting in lower energy bills over time.

2. Home Energy Audits: Free energy audits are available for residential customers. During these audits, trained professionals assess homes for energy efficiency and provide recommendations on improvements. This personalized service allows homeowners to understand specific changes that can lead to savings.

3. Weatherization Assistance: This program is particularly beneficial for low-income households. By improving insulation, sealing air leaks, and enhancing overall energy efficiency, residents can maintain comfortable indoor temperatures without over-relying on heating and cooling systems.

4. Community Workshops: Seattle City Light conducts workshops that educate residents about energy conservation strategies. These sessions cover topics such as smart energy use, seasonal tips for reducing consumption, and the benefits of renewable energy sources, highlighting examples of clean energy engagement in other cities.

The Impact on Households

The impact of these initiatives is profound. By assisting over 93,000 customers in lowering their electricity bills, Seattle City Light not only provides immediate financial relief but also encourages a long-term commitment to energy conservation. This collective effort has resulted in significant reductions in overall energy consumption, contributing to a decrease in greenhouse gas emissions—a critical step in the fight against climate change.

Additionally, the programs have been particularly beneficial for low-income households. By targeting these communities, Seattle City Light ensures that the benefits of energy efficiency reach those who need them the most, promoting equity-focused regulation and access to essential resources.

Looking Ahead: Challenges and Opportunities

While the success of these initiatives is commendable, challenges remain. Fluctuating energy prices can still pose difficulties for many households, especially those on fixed incomes, as some utilities explore minimum charges for low-usage customers in their rate structures. Seattle City Light recognizes the need for ongoing support and resources to help residents navigate these financial challenges.

The utility is committed to expanding its programs to reach even more customers in the future. This includes enhancing outreach efforts to ensure that residents are aware of the available resources, even as debates like utility revenue in a free-electricity future shape planning, and potentially forming partnerships with local organizations to broaden the impact of its initiatives.

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Bitcoin Energy Debate examines electricity usage, mining costs, environmental impact, and blockchain efficiency, weighing renewable power, carbon footprint, scalability, and transaction throughput to clarify stakeholder claims from Tesla, Square, academics, and policymakers.

Key Points

Debate on Bitcoin mining's power use, environmental impact, efficiency, and scalability versus alternative blockchains.

✅ Compares energy intensity with transaction throughput and system outputs.

✅ Weighs renewables, stranded power, and carbon footprint in mining.

✅ Assesses PoS blockchains, stablecoins, and scalability tradeoffs.

There is a great debate underway about the electricity required to process Bitcoin transactions. The debate is significant, the stakes are high, the views are diverse, and there are smart people on both sides. Bitcoin generates a lot of emotion, thereby producing too much heat and not enough light. In this post, I explain the importance of identifying the key issues in the debate, and of understanding the nature and extent of disagreement about how much electrical energy Bitcoin consumes.

Consider the background against which the debate is taking place. Because of its unstable price, Bitcoin cannot serve as a global mainstream medium of exchange. The instability is apparent. On January 1, 2021, Bitcoin’s dollar price was just over $29,000. Its price rose above $63,000 in mid-April, and then fell below $35,000, where it has traded recently. Now the financial media is asking whether we are about to experience another “cyber winter” as the prices of cryptocurrencies continue their dramatic declines.

Central banks warns of bubble on bitcoins as it skyrockets
As bitcoins skyrocket to more than $12 000 for one BTC, many central banks as ECB or US Federal ... [+] NURPHOTO VIA GETTY IMAGES
Bitcoin is a high sentiment beta asset, and unless that changes, Bitcoin cannot serve as a global mainstream medium of exchange. Being a high sentiment beta asset means that Bitcoin’s market price is driven much more by investor psychology than by underlying fundamentals.

As a general matter, high sentiment beta assets are difficult to value and difficult to arbitrage. Bitcoin qualifies in this regard. As a general matter, there is great disagreement among investors about the fair values of high sentiment beta assets. Bitcoin qualifies in this regard.

One major disagreement about Bitcoin involves the very high demand for electrical power associated with Bitcoin transaction processing, an issue that came to light several years ago. In recent months, the issue has surfaced again, in a drama featuring disagreement between two prominent industry leaders, Elon Musk (from Tesla and SpaceX) and Jack Dorsey (from Square).

On one side of the argument, Musk contends that Bitcoin’s great need for electrical power is detrimental to the environment, especially amid disruptions in U.S. coal and nuclear power that increase supply strain.  On the other side, Dorsey argues that Bitcoin’s electricity profile is a benefit to the environment, in part because it provides a reliable customer base for clean electric power. This might make sense, in the absence of other motives for generating clean power; however, it seems to me that there has been a surge in investment in alternative technologies for producing electricity that has nothing to do with cryptocurrency. So I am not sure that the argument is especially strong, but will leave it there. In any event, this is a demand side argument.

A supply side argument favoring Bitcoin is that the processing of Bitcoin transactions, known as “Bitcoin mining,” already uses clean electrical power, power which has already been produced, as in hydroelectric plants at night, but not otherwise consumed in an era of flat electricity demand across mature markets.

Both Musk and Dorsey are serious Bitcoin investors. Earlier this year, Tesla purchased $1.5 billion of Bitcoin, agreed to accept Bitcoin as payment for automobile sales, and then reversed itself. This reversal appears to have pricked an expanding Bitcoin bubble. Square is a digital transaction processing firm, and Bitcoin is part of its long-term strategy.

Consider two big questions at the heart of the digital revolution in finance. First, to what degree will blockchain replace conventional transaction technologies? Second, to what degree will competing blockchain based digital assets, which are more efficient than Bitcoin, overcome Bitcoin’s first mover advantage as the first cryptocurrency?

To gain some insight about possible answers to these questions, and the nature of the issues related to the disagreement between Dorsey and Musk, I emailed a series of academics and/or authors who have expertise in blockchain technology.

David Yermack, a financial economist at New York University, has written and lectured extensively on blockchains. In 2019, Yermack wrote the following: “While Bitcoin and successor cryptocurrencies have grown remarkably, data indicates that many of their users have not tried to participate in the mainstream financial system. Instead they have deliberately avoided it in order to transact in black markets for drugs and other contraband … or evade capital controls in countries such as China.” In this regard, cyber-criminals demanding ransom for locking up their targets information systems often require payment in Bitcoin. Recent examples of cyber-criminal activity are not difficult to find, such as incidents involving Kaseya and Colonial Pipeline.

David Yermack continues: “However, the potential benefits of blockchain for improving data security and solving moral hazard problems throughout the financial system have become widely apparent as cryptocurrencies have grown.” In his recent correspondence with me, he argues that the electrical power issue associated with Bitcoin “mining,” is relatively minor because Bitcoin miners are incentivized to seek out cheap electric power, and patterns shifted as COVID-19 changed U.S. electricity consumption across sectors.

Thomas Philippon, also a financial economist at NYU, has done important work characterizing the impact of technology on the resource requirements of the financial sector. He has argued that historically, the financial sector has comprised about 6-to-7% of the economy on average, with variability over time. Unit costs, as a percentage of assets, have consistently been about 2%, even with technological advances. In respect to Bitcoin, he writes in his correspondence with me that Bitcoin is too energy inefficient to generate net positive social benefits, and that energy crisis pressures on U.S. electricity and fuels complicate the picture, but acknowledges that over time positive benefits might be possible.

Emin Gün Sirer is a computer scientist at Cornell University, whose venture AVA Labs has been developing alternative blockchain technology for the financial sector. In his correspondence with me, he writes that he rejects the argument that Bitcoin will spur investment in renewable energy relative to other stimuli. He also questions the social value of maintaining a fairly centralized ledger largely created by miners that had been in China and are now migrating to other locations such as El Salvador.

Bob Seeman is an engineer, lawyer, and businessman, who has written a book entitled Bitcoin: The Mother of All Scams. In his correspondence with me, he writes that his professional experience with Bitcoin led him to conclude that Bitcoin is nothing more than unlicensed gambling, a point he makes in his book.

David Gautschi is an academic at Fordham University with expertise in global energy. I asked him about studies that compare Bitcoin’s use of energy with that of the U.S. financial sector. In correspondence with me, he cautioned that the issues are complex, and noted that online technology generally consumes a lot of power, with electricity demand during COVID-19 highlighting shifting load profiles.

My question to David Gautschi was prompted by a study undertaken by the cryptocurrency firm Galaxy Digital. This study found that the financial sector together with the gold industry consumes twice as much electrical power as Bitcoin transaction processing. The claim by Galaxy is that Bitcoin’s electrical power needs are “at least two times lower than the total energy consumed by the banking system as well as the gold industry on an annual basis.”

Galaxy’s analysis is detailed and bottom up based. In order to assess the plausibility of its claims, I did a rough top down analysis whose results were roughly consistent with the claims in the Galaxy study. For sake of disclosure, I placed the heuristic calculations I ran in a footnote.1 If we accept the Galaxy numbers, there remains the question of understanding the outputs produced by the electrical consumption associated with both Bitcoin mining and U.S. banks’ production of financial services. I did not see that the Galaxy study addresses the output issue, and it is important.

Consider some quick statistics which relate to the issue of outputs. The total market for global financial services was about $20 trillion in 2020. The number of Bitcoin transactions processed per day was about 330,000 in December 2020, and about 400,000 in January 2021. The corresponding number for Bitcoin’s digital rival Ethereum during this time was about 1.1 million transactions per day. In contrast, the global number of credit card transactions per day in 2018 was about 1 billion.2

Bitcoin Value Falls
LONDON, ENGLAND - NOVEMBER 20: A visual representation of the cryptocurrencies Bitcoin and Ethereum ... [+] GETTY IMAGES
These numbers tell us that Bitcoin transactions comprise a small share, on the order of 0.04%, of global transactions, but use something like a third of the electricity needed for these transactions. That said, the associated costs of processing Bitcoin transactions relate to tying blocks of transactions together in a blockchain, not to the number of transactions. Nevertheless, even if the financial sector does indeed consume twice as much electrical power as Bitcoin, the disparity between Bitcoin and traditional financial technology is striking, and the experience of Texas grid reliability underscores system constraints when it comes to output relative to input.  This, I suggest, weakens the argument that Bitcoin’s electricity demand profile is inconsequential because Bitcoin mining uses slack electricity.

A big question is how much electrical power Bitcoin mining would require, if Bitcoin were to capture a major share of the transactions involved in world commerce. Certainly much more than it does today; but how much more?

Given that Bitcoin is a high sentiment beta asset, there will be a lot of disagreement about the answers to these two questions. Eventually we might get answers.

At the same time, a high sentiment beta asset is ill suited to being a medium of exchange and a store of value. This is why stablecoins have emerged, such as Diem, Tether, USD Coin, and Dai. Increased use of these stable alternatives might prevent Bitcoin from ever achieving a major share of the transactions involved in world commerce.

We shall see what the future brings. Certainly El Salvador’s recent decision to make Bitcoin its legal tender, and to become a leader in Bitcoin mining, is something to watch carefully. Just keep in mind that there is significant downside to experiencing foreign exchange rate volatility. This is why global financial institutions such as the World Bank and IMF do not support El Salvador’s decision; and as I keep saying, Bitcoin is a very high sentiment beta asset.

In the past I suggested that Bitcoin bubble would burst when Bitcoin investors conclude that its associated processing is too energy inefficient. Of course, many Bitcoin investors are passionate devotees, who are vulnerable to the psychological bias known as motivated reasoning. Motivated reasoning-based sentiment, featuring denial,3 can keep a bubble from bursting, or generate a series of bubbles, a pattern we can see from Bitcoin’s history.

I find the argument that Bitcoin is necessary to provide the right incentives for the development of clean alternatives for generating electricity to be interesting, but less than compelling. Are there no other incentives, such as evolving utility trends, or more efficient blockchain technologies? Bitcoin does have a first mover advantage relative to other cryptocurrencies. I just think we need to be concerned about getting locked into an technologically inferior solution because of switching costs.

There is an argument to made that decisions, such as how to use electric power, are made in markets with self-interested agents properly evaluating the tradeoffs. That said, think about why most of the world adopted the Windows operating system in the 1980s over the superior Mac operating system offered by Apple. Yes, we left it to markets to determine the outcome. People did make choices; and it took years for Windows to catch up with the Mac’s operating system.

My experience as a behavioral economist has taught me that the world is far from perfect, to expect to be surprised, and to expect people to make mistakes. We shall see what happens with Bitcoin going forward.

As things stand now, Bitcoin is well suited as an asset for fulfilling some people’s urge to engage in high stakes gambling. Indeed, many people have a strong need to engage in gambling. Last year, per capita expenditure on lottery tickets in Massachusetts was the highest in the U.S. at over $930.

High sentiment beta assets offer lottery-like payoffs. While Bitcoin certainly does a good job of that, it cannot simultaneously serve as an effective medium of exchange and reliable store of value, even setting aside the issue at the heart of the electricity debate.

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Nighttime thermoradiative power converts outgoing infrared radiation into electricity using semiconductor photodiodes, leveraging negative illumination and sky cooling to harvest renewable energy from Earth-to-space heat flow when solar panels rest, regardless of weather.

Key Points

Nighttime thermoradiative power converts Earth's outgoing infrared heat into electricity using semiconductor diodes.

✅ Uses negative illumination to tap Earth-to-space heat flow

✅ Infrared semiconductor photodiodes generate small nighttime current

✅ Theoretical output ~4 W/m^2; lab demo reached 64 nW/m^2

There's a stark contrast between the freezing temperatures of space and the relatively balmy atmosphere of Earth, and that contrast could help generate electricity, scientists say – and alongside concepts such as space-based solar power, utilizing the same optoelectronic physics used in solar panels. The obvious difference this would have compared with solar energy is that it would work during the night time, a potential source of renewable power that could keep on going round the clock and regardless of weather conditions.

Solar panels are basically large-scale photodiodes - devices made out of a semiconducting material that converts the photons (light particles) coming from the Sun into electricity by exciting electrons in a material such as silicon, while concepts like space solar beaming could complement them during adverse weather.

In this experiment, the photodiodes work 'backwards': as photons in the form of infrared radiation - also known as heat radiation - leave the system, a small amount of energy is produced, similar to how raindrop electricity harvesting taps ambient fluxes in other experiments.

This way, the experimental system takes advantage of what researchers call the "negative illumination effect" – that is, the flow of outgoing radiation as heat escapes from Earth back into space. The setup explained in the new study uses an infrared semiconductor facing into the sky to convert this flow into electrical current.

"The vastness of the Universe is a thermodynamic resource," says one of the researchers, Shanhui Fan from Stanford University in California.

"In terms of optoelectronic physics, there is really this very beautiful symmetry between harvesting incoming radiation and harvesting outgoing radiation."

It's an interesting follow-up to a research project Fan participated in last year: a solar panel that can capture sunlight while also allowing excess heat in the form of infrared radiation to escape into space.

In the new study, this "energy harvesting from the sky" process can produce a measurable amount of electricity, the researchers have shown – though for the time being it's a long way from being efficient enough to contribute to our power grids, but advances in peer-to-peer energy sharing could still make niche deployments valuable.

In the team's experiments they were able to produce 64 nanowatts per square metre (10.8 square feet) of power – only a trickle, but an amazing proof of concept nevertheless. In theory, the right materials and conditions could produce a million times more than that, and analyses of cheap abundant electricity show how rapidly such advances compound, reaching about 4 watts per square metre.

"The amount of power that we can generate with this experiment, at the moment, is far below what the theoretical limit is," says one of the team, Masashi Ono from Stanford.

When you consider today's solar panels are able to generate up to 100-200 watts per square metre, and in China solar is cheaper than grid power across every city, this is obviously a long way behind. Even in its earliest form, though, it could be helpful for keeping low-power devices and machines running at night: not every renewable energy device needs to power up a city.

Now that the researchers have proved this can work, the challenge is to improve the performance of the experimental device. If it continues to show promise, the same idea could be applied to capture energy from waste heat given off by machinery, and results in humidity-powered generation suggest ambient sources are plentiful.

"Such a demonstration of direct power generation of a diode facing the sky has not been previously reported," explain the researchers in their published paper.

"Our results point to a pathway for energy harvesting during the night time directly using the coldness of outer space."

The research has been published in Applied Physics Letters.

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