Obama commits $2 billion to solar companies

IESO Capacity Auctions will competitively procure resources for Ontario electricity needs, boosting reliability and resource adequacy through market-based bidding, enabling demand response, energy storage, and flexible supply to meet changing load and regional grid conditions.

Key Points

A competitive, technology-neutral auction buys capacity at lowest cost to keep Ontario's grid reliable and flexible.

✅ Market-based procurement reduces system costs.

✅ Enables demand response, storage, and hybrid resources.

✅ Increases flexibility and regional reliability in Ontario.

The Independent Electricity System Operator (IESO) is introducing changes to Ontario's electricity system that will help save Ontarians about $3.4 billion over a 10-year period. The changes include holding annual capacity auctions to acquire electricity resources at lowest cost that can be called upon when and where they are needed to meet Ontario electricity needs. 

Today's announcement marks the release of a high level design for future auctions, with changes for electricity consumers expected as the first is set to be held in late 2022.

"These auctions will specify how much electricity we need, and introduce a competitive process to determine who can meet that need. It's a competition among all eligible resources, and it's the Ontario consumer, including industrial electricity ratepayers, who benefits through lower costs and a more flexible system better able to respond to changing demand and supply conditions," says IESO President and CEO Peter Gregg.

In the past decade, electricity supply was typically acquired through very prescriptive means with defined targets for specific types of resources such as wind and solar, and secured through 20-year contracts.  While these long-term commitments helped Ontario transform its generation fleet over the last decade, electricity cost allocation also played a role, but longer term contracts provide limited flexibility in dealing with unexpected changes in the power system. 

"Imagine signing a 20-year contract for your cable TV service. In five years' time, electricity rates could be lower, new competitors may have entered the market, or entirely new and innovative platforms and services like Netflix may have emerged. You miss out on opportunities for improvement by being locked-in," says Gregg.

Provincial electricity demand has traditionally fluctuated over time due to factors like economic growth, conservation and the introduction of generating resources on local distribution systems, with occasional issues such as phantom demand affecting customers' costs as well. Technological changes are adding another layer of uncertainty to future demand as electric vehicles, energy storage and low-cost solar panels become more common.

"Our planners do their best to forecast electricity demand, but the truth is there's no such thing as certainty in electricity planning. That's why flexibility is so important. We don't want Ontarians to have to pay more on the typical Ontario electricity bill for electricity resources than are needed to ensure a reliable power system that can continue to meet Ontario's needs," says IESO Vice President and COO Leonard Kula.

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Brazil ICMS Tax Cap limits state VAT on fuels, natural gas, electricity, communications, and transit, promising short-term price relief amid inflation, with federal compensation to states and potential legal challenges affecting investments and ANP auctions.

Key Points

A policy capping state VAT at 17-18 percent on fuels, electricity, and services to temper prices and inflation.

✅ Caps VAT to 17-18% on fuels, power, telecom, transit

✅ Short-term relief; medium-long term impact uncertain

✅ Federal compensation; potential court challenges, investment risk

Brazil’s congress approved a bill that limits the ICMS tax rate that state governments can charge on fuels, natural gas, electricity, communications, and public transportation. 

Local lawyers told BNamericas that the measure may reduce fuel and power prices in the short term, similar to Brazil power sector relief loans seen during the pandemic, but it is unlikely to produce any major effects in the medium and long term. 

In most states the ceiling was set at 17% or 18% and the federal government will pay compensation to the states for lost tax revenue until December 31, via reduced payments on debts that states owe the federal government.

The bill will become law once signed by President Jair Bolsonaro, who pushed strongly for the proposal with an eye on his struggling reelection campaign for the October presidential election. Double-digit inflation has turned into a major election issue and fuel and electricity prices have been among the main inflation drivers, as seen in EU energy-driven inflation across the bloc this year. Congress’ approval of the bill is seen by analysts as political victory for the Brazilian leader.

How much difference will it make?

Marcus Francisco, tax specialist and partner at Villemor Amaral Advogados, said that in the formation of fuel and electricity prices there are other factors, including high natural gas prices, that drive increases.

“In the case of fuels, if the barrel of oil [price] increases, automatically the final price for the consumer will go up. For electricity, on the other hand, there are several subsidies and policy choices such as Florida rejecting federal solar incentives that are part of the price and that can increase the rate [paid],” he said. 

There is also a possibility that some states will take the issue to the supreme court since ICMS is a key source of revenue for them, Francisco added.

Tiago Severini, a partner at law firm Vieira Rezende, said the comparison between the revenue impact and the effective price reduction, based on the estimates made by the states and the federal government, seems disproportionate, and, as seen in Europe, rolling back European electricity prices is often tougher than it appears. 

“In other words, a large tax collection impact is generated, which is quite unequal among the different states, for a not so strong price reduction,” he said.

“Due to the lack of clarity regarding the precision of the calculations involved, it’s difficult even to assess the adequacy of the offsets the federal government has been considering, and international cases such as France's new electricity pricing scheme illustrate how complex it can be to align fiscal offsets with regulatory constraints, to cover the cost it would have with the compensation for the states” Severini added.

The compensation ideas that are known so far include hiking other taxes, such as the social contribution on net profits (CSLL) that is paid by oil and gas firms focused on exploration and production.

“This can generate severe adverse effects, such as legal disputes, reduced investments in the country, and reduced attractiveness of the new auctions by [sector regulator] ANP, and costly interventions like the Texas electricity market bailout after extreme weather events,” Severini said. 

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BC Hydro Rate Increase proposes a 2.3% hike from April, with BCUC review, aligning below inflation and funding clean energy, electrification, and grid upgrades across British Columbia while keeping electricity prices among North America's lowest.

Key Points

A proposed 2.3% BC Hydro hike from April, under BCUC review, funds clean energy and keeps average bills below inflation.

✅ Adds about $2 per month to average residential bill

✅ Sixth straight increase below inflation since 2018

✅ Supports renewable projects and grid modernization

The British Columbia government says the province’s Crown power utility is applying for a 2.3-per-cent rate increase starting in April, with higher BC Hydro rates previously outlined, adding about $2 a month to the average residential bill.

A statement from the Energy Ministry says it’s the sixth year in a row that BC Hydro has applied for an increase below the rate of inflation, similar to a 3 per cent rise noted in a separate approval, which still trailed inflation.

It says rates are currently 15.6 per cent lower than the cumulative rate of inflation over the last seven years, starting in 2017-2018, with a provincial rate freeze among past measures, and 12.4 per cent lower than the 10-year rates plan established by the previous government in 2013.

The ministry says the “modest” rate increase application comes after consideration of a variety of options and their long-term impacts, including scenarios like a 3.75% two-year path evaluated alongside others, and the B.C. Utilities Commission is expected to decide on the plan by the end of February.

Chris O’Riley, president of BC Hydro, says the rates application would keep electricity costs in the province among the lowest in North America, even as a BC Hydro fund surplus prompted calls for changes, while supporting investments in clean energy to power vehicles, homes and businesses.

Energy Minister Josie Osborne says it’s more important than ever to keep electricity bills down, especially as Ontario hydro rates increase in a separate jurisdiction, as the cost of living rises at rates that are unsustainable for many.

“Affordable, stable BC Hydro rates are good for people, businesses and climate as we work together to power our growing economy with renewable energy instead of fossil fuels,” Osborne says in a statement issued Monday.

Earlier this year, the ministry said BC Hydro provided $315 million in cost-of-living bill credits, while in another province Manitoba Hydro scaled back an increase to ease pressure, to families and small businesses in the province, including those who receive their electricity service from FortisBC or a municipal utility.

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Hedonistic Sustainability turns Copenhagen's ARC waste-to-energy plant into a public playground, blending ski slope, climbing wall, and trails with carbon-neutral heating, renewables, circular economy design, and green growth for climate action and liveability.

Key Points

A design approach fusing public recreation with clean-energy infrastructure to drive carbon-neutral, livable urban growth.

✅ Waste-to-energy plant doubles as recreation hub

✅ Supports carbon-neutral heating and renewables

✅ Stakeholder-driven, scalable urban climate model

“We call it hedonistic sustainability,” says Jacob Simonsen of the decision to put an artificial ski slope on the roof of the £485m Amager Resource Centre (Arc), Copenhagen’s cutting-edge new waste-to-energy power plant that feeds the city’s district heating network as well. “It’s not just good for the environment, it’s good for life.”

Skiing is just one of the activities that Simonsen, Arc’s chief executive, and Bjarke Ingels, its lead architect, hope will enhance the latest jewel in Copenhagen’s sustainability crown. The incinerator building also incorporates hiking and running trails, a street fitness gym and the world’s highest outdoor climbing wall, an 85-metre “natural mountain” complete with overhangs that rises the full height of the main structure.

In Copenhagen, green transformation goes hand-in-hand with job creation, a growing economy and a better quality of life

Frank Jensen, lord mayor

It’s all part of Copenhagen’s plan to be net carbon-neutral by 2025. Even now, after a summer that saw wildfires ravagethe Arctic Circle and ice sheets in Greenland suffer near-record levels of melt, the goal seems ambitious. In 2009, when the project was formulated, it was positively revolutionary.

“A green, smart, carbon-neutral city,” declared the cover of the climate action plan, aligning with a broader electric planet vision, before detailing the scale of the challenge: 100 new wind turbines; a 20% reduction in both heat and commercial electricity consumption; 75% of all journeys to be by bike, on foot, or by public transport; the biogas-ification of all organic waste; 60,000 sq metres of new solar panels; and 100% of the city’s heating requirements to be met by renewables.

Radical and far-reaching, the scheme dared to rethink the very infrastructure underpinning the city. There’s still not a climate project anywhere else in the world that comes close, even as leaders elsewhere champion a fully renewable grid by 2030.

And, so far, it’s working. CO2 emissions have been reduced by 42% since 2005, and while challenges around mobility and energy consumption remain (new technologies such as better batteries and carbon capture are being implemented, and global calls for clean electricity investment grow), the city says it is on track to achieve its ultimate goal.

More significant still is that Copenhagen has achieved this while continuing to grow in traditional economic terms. Even as some commentators insist that nothing short of a total rethink of free-market economics and corporate structures is required to stave off global catastrophe, the Danish capital’s carbon transformation has happened alongside a 25% growth in its economy over two decades. Copenhagen’s experience will be a model for other world cities as the global energy transition unfolds.

The sentiment that lies behind Arc’s conception as a multi-use public good – “hedonistic sustainability” – is echoed by Bo Asmus Kjeldgaard, former mayor of Copenhagen for the environment and the man originally tasked, back in 2010, with making the plan a reality.

“We combined life quality with sustainability and called it ‘liveability’,” says Kjeldgaard, now CEO of his own climate adaptation company, Greenovation. “We succeeded in building a good narrative around this, one that everybody could believe in.”

The idea was first floated in the late 1990s, when the newly elected Kjeldgaard had a vision of Copenhagen as the environmental capital of Europe. His enthusiasm ran into political intransigence, however, and despite some success, a lack of budget meant most of his work became “just another branding exercise – it was greenwashing”.

We’re such a rich country – change should be easy for us

Claus Nielsen, furniture maker and designer

But after stints as mayor of family and the labour market, and children and young people, he ended up back at environment in 2010 with renewed determination and, crucially, a broader mandate from the city council. “I said: ‘This time, we have to do it right,’” he recalls, “so we made detailed, concrete plans for every area, set the carbon target, and demanded the money and the manpower to make it a reality.”

He brought on board more than 200 stakeholders, from businesses to academia to citizen representatives, and helped them develop 22 specific business plans and 65 separate projects. So far the plan appears on track: there has been a 15% reduction in heat consumption, 66% of all trips in the city are now by bike, on foot or public transport, and 51% of heat and power comes from renewable electricity sources.

The onus placed on ordinary Copenhageners to walk and cycle more, pay higher taxes (especially on cars) and put up with the inconvenience of infrastructure construction has generally been met with understanding and good grace. And while some people remain critical of the fact that Copenhagen airport is not factored into the CO2 calculations – it lies beyond the city’s boundaries – and grumble about precise definitions and formulae, dissent has been rare.

This relative lack of nimbyism and carping about change can, says Frank Jensen, the city’s lord mayor, be traced to longstanding political traditions.

“Caring for the environment and taking responsibility for society in general has been an integral part of the upbringing of many Danes,” he says. “Moreover, there is a general awareness that climate change now calls for immediate, ambitious and collective action.” A 2018 survey by Concito, a thinktank, found that such action was a top priority for voters.

Jensen is keen to stress the cooperative nature of the plan and says “our visions have to be grounded in the everyday lives of people to be politically feasible”. Indeed, involving so many stakeholders, and allowing them to actively help shape both the ends and the means, has been key to the plan’s success so far and the continued goodwill it enjoys. “It’s so important to note that we [the authorities] cannot do this alone,” says Jørgen Abildgaard, Copenhagen’s executive climate programme director.

Many businesses around the world have typically been reluctant to embrace sustainability when a dip in profits or inconvenience might be the result, but not in Copenhagen. Martin Manthorpe, director of strategy, business development and public affairs at NCC, one of Scandinavia’s largest construction and industrial groups, was brought in early on by Abildgaard to represent industry on the municipality’s climate panel, and to facilitate discussions with the wider business community. He thinks there are several reasons why.

“The Danes have a trading mindset, meaning ‘What will I have to sell tomorrow?’ is just as important as ‘What am I producing today?’” he says. “Also, many big Danish companies are still ultimately family-owned, so the culture leans more towards long-term thinking.”

It is, he says, natural for business to be concerned with issues around sustainability and be willing to endure short-term pain: “To do responsible, long-term business, you need to see yourself as part of the larger puzzle that is called ‘society’.”

Furthermore, in Denmark climate change denial is given extremely short shrift. “We believe in the science,” says Anders Haugaard, a local entrepreneur. “Why wouldn’t you? We’re told sustainability brings only benefits and we’ve got no reason to be suspicious.”

“No one would dare argue against the environment,” says his friend Claus Nielsen, a furniture maker and designer. “We’re such a rich country – change should be easy for us.” Nielsen talks about how enlightened his kids are – “my 11-year-old daughter is now a flexitarian ” – and says that nowadays he mainly buys organic; Haugaard doesn’t see a problem with getting rid of petrol cars (the whole country is aiming to be fossil fuel-free by 2050 as the EU electricity use by 2050 is expected to double).

Above all, there’s a belief that sustainability need not make the city poorer: that innovation and “green growth” can be lucrative in and of themselves. “In Copenhagen, green transformation goes hand-in-hand with job creation, a growing economy and a better quality of life,” says Jensen. “We have also shown that it’s possible to combine this transition with economic growth and market opportunities for businesses, and I think that other countries can learn from our example.”

Besides, as Jensen notes, there is little alternative, and even less time: “National states have failed to take enough responsibility, but cities have the power and will to create concrete solutions. We need to start accelerating their implementation – we need to act now.”

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New England Solar Interconnection Costs highlight distributed generation strains, transmission charges, distribution upgrades, and DAF fees as National Grid maps hosting capacity, driving queue delays and FERC disputes in Rhode Island and Massachusetts.

Key Points

Rising upfront grid upgrade and DAF charges for distributed solar in RI and MA, including some transmission costs.

✅ Upfront grid upgrades shifted to project developers

✅ DAF and transmission charges increase per MW costs

✅ Queue delays tied to hosting capacity and cluster studies

Solar developers in Rhode Island and Massachusetts say soaring charges to interconnect with the electric grid are threatening the viability of projects. 

As more large-scale solar projects line up for connections, developers are being charged upfront for the full cost of the infrastructure upgrades required, a long-common practice that they say is now becoming untenable amid debates over a new solar customer charge in Nova Scotia. 

“It is a huge issue that reflects an under-invested grid that is not ready for the volume of distributed generation that we’re seeing and that we need, particularly solar,” said Jeremy McDiarmid, vice president for policy and government affairs at the Northeast Clean Energy Council, a nonprofit business organization. 

Connecting solar and wind systems to the grid often requires upgrades to the distribution system to prevent problems, such as voltage fluctuations and reliability risks highlighted by Australian distributors in their networks. Costs can vary considerably from place to place, depending on the amount of distributed generation coming online and the level of capacity planning by regulators, said David Feldman, a senior financial analyst at the National Renewable Energy Laboratory.

“Certainly the Northeast often has more distribution challenges than much of the rest of the country just because it’s more populous and often the infrastructure is older,” he said. “But it’s not unique to the Northeast — in the Midwest, for example, there’s a significant amount of wind projects in the queues and significant delays.”

In Rhode Island and Massachusetts, where strong incentive programs are driving solar development, the level of solar coming online is “exposing the under-investment in the distribution system that is causing these massive costs that National Grid is assigning to particular projects or particular groups of projects,” McDiarmid said. “It is going to be a limiting factor for how much clean energy we can develop and bring online.”

Frank Epps, chief executive officer at Energy Development Partners, has been developing solar projects in Rhode Island since 2010. In that time, he said, interconnection charges on his projects have grown from about $80,000-$120,000 per megawatt to more than $400,000 per megawatt. He attributed the increase to a lack of investment in the distribution network by National Grid over the last decade.

He and other developers say the utility is now adding further to their costs by passing along not just the cost of improving the distribution system — the equivalent of the city street of the grid that brings power directly to customers — but also costs for modifying the transmission system — the interstate highway that moves bulk power over long distances to substations. 

Solar developers who are only requesting to hook into the distribution system, and not applying for transmission service, say they should not be charged for those additional upgrades under state interconnection rules unless they are properly authorized under the federal law that governs the transmission system. 

A Rhode Island solar and wind developer filed a complaint with the Federal Energy Regulatory Commission in February over transmission system improvement charges for its four proposed solar projects. Green Development said National Grid subsidiaries Narragansett Electric and New England Power Company want to charge the company more than $500,000 a year in operating and maintenance expenses assessed as so-called direct assignment facility charges. 

“This amount nearly doubles the interconnection costs associated with the projects,” which total 38.4 megawatts in North Smithfield, the company says in its complaint. “Crucially, these charges are linked to recovering costs associated with providing transmission service — even though no such transmission service is being provided to Green Development.”

But Ted Kresse, a spokesperson for National Grid, said the direct assignment facility, or DAF, construct has been in place for decades and has been applied to any customer affecting the need for transmission upgrades.

“It is the result of the high penetration and continued high volume of distributed generation interconnections that has recently prompted the need for transmission upgrades, and subsequently the pass-through of the associated DAF charges,” he said. 

Several complaints before the Rhode Island Public Utilities Commission object to these DAF and other transmission charges.

One petition for dispute resolution concerns four solar projects totaling 40 MW being developed by Energy Development Partners in a former gravel pit in North Kingstown. Brown University has agreed to purchase the power. 

The developer signed interconnection service agreements with Narragansett Electric in 2019 requiring payment of $21.6 million for costs associated with connecting the projects at a new Wickford Junction substation. Last summer, Narragansett sought to replace those agreements with new ones that reclassified a portion of the costs as transmission-level costs, through New England Power, National Grid’s transmission subsidiary.

That shift would result in additional operational and maintenance charges of $835,000 per year for the estimated 35-year life of the projects, the complaint says.

“This came as a complete shock to us,” Epps said. “We’re not just paying for the maintenance of a new substation. We are paying a share of the total cost that the system owner has to own and operate the transmission system. So all of the sudden, it makes it even tougher for distributed energy resources to be viable.”

In its response to the petition, National Grid argues that the charges are justified because the solar projects will require transmission-level upgrades at the new substation. The company argues that the developer should be responsible for the costs rather than ratepayers, “who are already supporting renewable energy development through their electric rates.”

Seth Handy, one of the lawyers representing Green Development in the FERC complaint, argues that putting transmission system costs on distribution assets is unfair because the distributed resources are “actually reducing the need to move electricity long distances. We’ve been fighting these fights a long time over the underestimating of the value of distributed energy in reducing system costs.”

Handy is also representing the Episcopal Diocese of Rhode Island before the state Supreme Court in its appeal of an April 2020 public utilities commission order upholding similar charges for a proposed 2.2-megawatt solar project at the diocese’s conference center and camp in Glocester. 

Todd Bianco, principal policy associate at the utilities commission, said neither he nor the chairperson can comment on the pending dockets contesting these charges. But he noted that some of these issues are under discussion in another docket examining National Grid’s standards for connecting distributed generation. Among the proposals being considered is the appointment of an independent ombudsperson to resolve interconnection disputes. 

Separately, legislation pending before the Rhode Island General Assembly would remove responsibility for administering the interconnection of renewable energy from utilities, and put it under the authority of the Rhode Island Infrastructure Bank, a financing agency.

Handy, who recently testified in support of the bill, said he believes National Grid has too many conflicting interests to administer interconnecting charges in a timely, transparent and fair fashion, and pointed to utility moves such as changes to solar compensation in other states as examples. In particular, he noted the company’s interests in expanding natural gas infrastructure. 

“There are all kinds of economic interests that they have that conflict with our state policy to provide lower-cost renewable energy and more secure energy solutions,” Handy said.

In testimony submitted to the House Committee on Corporations opposing the legislation, National Grid said such powers are well beyond the purpose and scope of the infrastructure bank. And it cited figures showing Rhode Island is third in the country for the most installed solar per square mile (behind New Jersey and Massachusetts).

Nadav Enbar, program manager at the Electric Power Research Institute, a nonprofit research organization for the utility industry, said interconnection delays and higher costs are becoming more common due to “the incredible uptake” in distributed renewable energy, particularly solar.

That’s impacting hosting capacity, the room available to connect all resources to a circuit without causing adverse harm to reliability and safety. 

“As hosting capacity is being reduced, it’s causing an increasing number of situations where utilities need to study their systems to guarantee interconnection without compromising their systems,” he said. “And that is the reason why you’re starting to see some delays, and it has translated into some greater costs because of the need for upgrades to infrastructure.”

The cost depends on the age or absence of infrastructure, projected load growth, the number of renewable energy projects in the queue, and other factors, he said. As utilities come under increasing pressure to meet state renewable goals, and as some states pilot incentives like a distributed energy rebate in Illinois to drive utility innovation, some (including National Grid) are beginning to provide hosting capacity maps that provide detailed information to developers and policymakers about the amount of distributed energy that can be accommodated at various locations on the grid, he said. 

In addition, the coming availability of high-tech “smart inverters” should help ease some of these problems because they provide the grid with more flexibility when it comes to connecting and communicating with distributed energy resources, Enbar said. 

In Massachusetts, the Department of Public Utilities has opened a docket to explore ways to better plan for and share the cost of upgrading distribution infrastructure to accommodate solar and other renewable energy sources as part of a grid overhaul for renewables nationwide. National Grid has been conducting “cluster studies” there that attempt to analyze the transmission impacts of a group of solar projects and the corresponding interconnection cost to each developer.

Kresse, of National Grid, said the company favors cost-sharing methodologies under consideration that would “provide a pathway to spread cost over the total enabled capacity from the upgrade, as opposed to spreading the cost over only those customers in the queue today.” 

Solar developers want regulators to take an even broader approach that factors in how the deployment of renewables and the resulting infrastructure upgrades benefit not just the interconnecting generator, but all customers. 

“Right now, if your project is the one that causes a multimillion-dollar upgrade, you are assigned that cost even though that upgrade is going to benefit a lot of other projects, as well as make the grid stronger,” said McDiarmid, of the clean energy council. “What we’re asking for is a way of allocating those costs among a variety of developers, as well as to the grid itself, meaning ratepayers. There’s a societal benefit to increasing the modernization of the grid, and improving the resilience of the grid.”

In the meantime, BlueHub Capital, a Boston-based solar developer focused on serving affordable housing developments, recently learned from National Grid that, as a part of one of the area studies, it will be required to pay $5.8 million in transmission and distribution upgrades to interconnect a 2-megawatt solar-plus-storage project that leverages cheaper batteries to enhance resilience, approved for a brownfield site in Gardner, Massachusetts. 

According to testimony submitted to the department, the sum is supposed to be paid within the next year, even though the project will have to wait to be interconnected until April 2027, when a new transmission line is completed. In addition, BlueHub will be responsible for DAF charges totaling $3.4 million over the 20-year life of the project. 

“We’re being asked to pay a fortune to provide solar that the state wants,” said DeWitt Jones, BlueHub’s president. “It’s so expensive that the upgrades are driving everyone out of the interconnection queue. The costs stay the same, but they fall on fewer projects. We need a process of grid design and modernization to guide this.”

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

Key Points

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

✅ Uses thermocouples to convert temperature gradients to voltage.

✅ Exploits radiative cooling to outer space for night power.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This research was published in Joule.

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