Coal an important ingredient in Canada's energy mix

COVID-19 Impact on U.S. Electricity Consumption shows commercial and industrial demand dropped as residential use rose, with flattened peak loads, weekday-weekend convergence, Texas hourly data, and energy demand as a real-time economic indicator.

Key Points

It reduced commercial and industrial demand while raising residential use, shifting peaks and weekday patterns.

✅ Commercial electricity down 12%; industrial down 14% in Q2 2020

✅ Residential use up 10% amid work-from-home and lockdowns

✅ Peaks flattened; weekday-weekend loads converged in Texas

This is an important turning point for the United States. We have a long road ahead. But one of the reasons I’m optimistic about Biden-Harris is that we will once again have an administration that believes in science.

To embrace this return to science, I want to write today about a fascinating new working paper by Tufts economist Steve Cicala.

Professor Cicala has been studying the effect of Covid on electricity consumption since back in March, when the Wall Street Journal picked up his work documenting an 18% decrease in electricity consumption in Italy.

The new work, focused on the United States, is particularly compelling because it uses data that allows him to distinguish between residential, commercial, and industrial sectors, against a backdrop of declining U.S. electricity sales over recent years.

Without further ado, here are four facts he uncovers about Covid and U.S. electricity demand during COVID-19 and consumption.

Fact #1: Firms Are Using Less
U.S. commercial electricity consumption fell 12% during the second quarter of 2020. U.S. industrial electricity consumption fell 14% over the same period.

This makes sense. The second quarter was by some measures, the worst quarter for the U.S. economy in over 145 years!

Economic activity shrank. Schools closed. Offices closed. Factories closed. Restaurants closed. Malls closed. Even health care offices closed as patients delayed going to the dentist and other routine care. All this means less heating and cooling, less lighting, less refrigeration, less power for computers and other office equipment, less everything.

The decrease in the industrial sector is a little more surprising. My impression had been that the industrial sector had not fallen as far as commercial, but amid broader disruptions in coal and nuclear power that strained parts of the energy economy, the patterns for both sectors are quite similar with the decline peaking in May and then partially rebounding by July. The paper also shows that areas with higher unemployment rates experienced larger declines in both sectors.

Fact #2: Households Are Using More
While firms are using less, households are using more. U.S. residential electricity consumption increased 10% during the second quarter of 2020. Consumption surged during March, April, and May, a reflection of the lockdown lifestyle many adopted, and then leveled off in June and July – with much less of the rebound observed on the commercial/industrial side.

This pattern makes sense, too. In Professor Cicala’s words, “people are spending an inordinate amount of time at home”. Many of us switched over to working from home almost immediately, and haven’t looked back. This means more air conditioning, more running the dishwasher, more CNN (especially last week), more Zoom, and so on.

The paper also examines the correlates of the decline. Areas in the U.S. where more people can work from home experienced larger increases. Unemployment rates, however, are almost completely uncorrelated with the increase.

Fact #3: Firms are Less Peaky
The paper next turns to a novel dataset from Texas, where Texas grid reliability is under active discussion, that makes it possible to measure hourly electricity consumption by sector.

As the figure above illustrates, the biggest declines in commercial/industrial electricity consumption have occurred Monday through Friday between 9AM and 5PM.

The dashed line shows the pattern during 2019. Notice the large spikes in electricity consumption during business hours. The solid line shows the pattern during 2020. Much smaller spikes during business hours.

Fact #4: Everyday is Like Sunday
Finally, we have what I would like to nominate as the “Energy Figure of the Year”.

Again, start with the pattern for 2019, reflected by the dashed line. Prior to Covid, Texas households used a lot more electricity on Saturdays and Sundays.

Then along comes Covid, and turned every day into the weekend. Residential electricity consumption in Texas during business hours Monday-Friday is up 16%(!).

In the pattern for 2020, it isn’t easy to distinguish weekends from weekdays. If you feel like weekdays and weekends are becoming a big blur – you are not alone.

Conclusion
Researchers are increasingly thinking about electricity consumption as a real-time indicator of economic activity, even as flat electricity demand complicates utility planning and investment. This is an intriguing idea, but Professor Cicala’s new paper shows that it is important to look sector-by-sector.

While commercial and industrial consumption indeed seem to measure the strength of an economy, residential consumption has been sharply countercylical – increasing exactly when people are not at work and not at school.

These large changes in behavior are specific to the pandemic. Still, with the increased blurring of home and non-home activities we may look back on 2020 as a key turning point in how we think about these three sectors of the economy.

More broadly, Professor Cicala’s paper highlights the value of social science research. We need facts, data, and yes, science, if we are to understand the economy and craft effective policies on energy insecurity and shut-offs as well.

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Germany energy liquidity crisis is straining municipal utilities as gas and power prices surge, margin calls rise, and Russian supply cuts bite, forcing state support, interventions, and emergency financing to stabilize households and businesses.

Key Points

A cash squeeze on German municipal utilities as soaring gas and power prices trigger margin calls and funding gaps.

✅ Margin calls and spot-market purchases strain cash flow

✅ State liquidity lines and EU collateral support proposed

✅ Gazprom cuts, Uniper distress heighten default risks

Germany’s fears that soaring power prices and gas prices could trigger a deeper crisis is starting to get real. 

Several hundred local utilities are coming under strain and need support, according to the head of Germany’s largest energy lobby group. The companies, generally owned by municipalities, supply households and small businesses directly and are a key part of the country’s power and gas network.

“The next step from the government and federal states must be to secure liquidity for these municipal companies,” Kerstin Andreae, chairwoman of the German Association of Energy and Water Industries, told Bloomberg in Berlin. “Prices are rising, and they have no more money to pay the suppliers. This is a big problem.”

Germany’s energy crunch intensified over the weekend after Russia’s Gazprom PJSC halted its key gas pipeline indefinitely, a stark wake-up call for policymakers to reduce fossil fuel dependence. European energy prices have surged again amid concerns over shortages this winter and fears of a worst-case energy scenario across the bloc. 

Many utilities are running into financial issues as they’re forced to cover missing Russian deliveries with expensive supplies on the spot market. German energy giant Uniper SE, which supplies local utilities, warned it will likely burn through a 7 billion-euro ($7 billion) government safety net and will need more help already this month.

Some German local utilities have already sought help, according to a government official, who asked not to be identified in line with briefing rules.  

With Europe’s largest economy already bracing for recession, Chancellor Olaf Scholz’s administration is battling on several fronts, testing the government’s financial capacity. The ruling coalition agreed Sunday on a relief plan worth about 65 billion euros -- part of an emerging energy shield package to contain the fallout of surging costs for households and businesses. 

Starting in October, local utilities will have to pay a levy for the gas acquired, which will further increase their financial burden, Andreae said.

Margin Calls
European gas prices are more than four times higher than usual for this time of year, underscoring why rolling back electricity prices is tougher than it appears for policymakers, as Russia cuts supplies in retaliation for sanctions related to its invasion of Ukraine. When prices peak, energy companies have to pay margin calls, extra collateral required to back their trades.

Read more: Energy Trade Risks Collapsing Over Margin Calls of $1.5 Trillion

The problem has hit local utilities in other countries as well. In Austria, the government approved a 2 billion-euro loan for Vienna’s municipal utility last month. 

The European Union is also planning help, floating gas price cap strategies among other tools. The bloc’s emergency measures will include support for electricity producers struggling to find enough cash to guarantee trades, according to European Commission President Ursula von der Leyen.

The situation has worsened in Germany as some of the country’s big gas importers are reluctant to sell more supplies to some of municipal companies amid fears they could default on payments, Andreae said. 

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Quebec Hydropower Export Retaliation examines using electricity exports to counter U.S. tariffs amid Canada-U.S. trade tensions, weighing clean energy supply, grid reliability, energy security, legal risks, and long-term market impacts.

Key Points

Using Quebec electricity exports as leverage against U.S. tariffs, and its economic, legal, and diplomatic consequences.

✅ Revenue loss for Quebec and higher costs for U.S. consumers

✅ Risk of legal disputes under trade and energy agreements

✅ Long-term erosion of market share and grid cooperation

As trade tensions between Canada and the United States continue to escalate, with electricity exports at risk according to recent reporting, discussions have intensified around potential Canadian responses to the imposition of U.S. tariffs. One of the proposals gaining attention is the idea of reducing or even halting the export of energy from Quebec to the U.S. This measure has been suggested by some as a potential countermeasure to retaliate against the tariffs. However, experts and industry leaders are urging caution, emphasizing that the consequences of such a decision could have significant economic and diplomatic repercussions for both Canada and the United States.

Quebec plays a critical role in energy trade, particularly in supplying hydroelectric power to the United States, especially to the northeastern states, including New York where tariffs may spike energy prices according to analysts, strengthening the case for stable cross-border flows. This energy trade is deeply embedded in the economic fabric of both regions. For Quebec, the export of hydroelectric power represents a crucial source of revenue, while for the U.S., it provides access to a steady and reliable supply of clean, renewable energy. This mutually beneficial relationship has been a cornerstone of trade between the two countries, promoting economic stability and environmental sustainability.

In the wake of recent U.S. tariffs on Canadian goods, some policymakers have considered using energy exports as leverage, echoing threats to cut U.S. electricity exports in earlier disputes, to retaliate against what is viewed as an unfair trade practice. The idea is to reduce or stop the flow of electricity to the U.S. as a way to strike back at the tariffs and potentially force a change in U.S. policy. On the surface, this approach may appear to offer a viable means of exerting pressure. However, experts warn that such a move would be fraught with significant risks, both economically and diplomatically.

First and foremost, Quebec's economy is heavily reliant on revenue from hydroelectric exports to the U.S. Any reduction in these energy sales could have serious consequences for the province's economic stability, potentially resulting in job losses and a decrease in investment. The hydroelectric power sector is a major contributor to Quebec's GDP, and recent events, including a tariff threat delaying a green energy bill in Quebec, illustrate how trade tensions can ripple through the policy landscape, while disrupting this source of income could harm the provincial economy.

Additionally, experts caution that reducing energy exports could have long-term ramifications on the energy relationship between Quebec and the northeastern U.S. These two regions have developed a strong and interconnected energy network over the years, and abruptly cutting off the flow of electricity could damage this vital partnership. Legal challenges could arise under existing trade agreements, and even as tariff threats boost support for Canadian energy projects among some stakeholders, the situation would grow more complex. Such a move could also undermine trust between the two parties, making future negotiations on energy and other trade issues more difficult.

Another potential consequence of halting energy exports is that U.S. states may seek alternative sources of energy, diminishing Quebec's market share in the long run. As the U.S. has a growing demand for clean energy, especially as it looks to transition away from fossil fuels, and looks to Canada for green power in several regions, cutting off Quebec’s electricity could prompt U.S. states to invest in other forms of energy, including renewables or even nuclear power. This could have a lasting effect on Quebec's position in the U.S. energy market, making it harder for the province to regain its footing.

Moreover, reducing or ceasing energy exports could further exacerbate trade tensions, leading to even greater economic instability. The U.S. could retaliate by imposing additional tariffs on Canadian goods or taking other measures that would negatively impact Canada's economy. This could create a cycle of escalating trade barriers that would hurt both countries and undermine the broader North American trade relationship.

While the concept of using energy exports as a retaliatory tool may seem appealing to some, the experts' advice is clear: the potential economic and diplomatic costs of such a strategy outweigh the short-term benefits. Quebec’s role as an energy supplier to the U.S. is crucial to its own economy, and maintaining a stable, reliable energy trade relationship is essential for both parties. Rather than escalating tensions further, it may be more prudent for Canada and the U.S. to seek diplomatic solutions that preserve trade relations and minimize harm to their economies.

While the idea of using Quebec’s energy exports as leverage in response to U.S. tariffs may appear attractive on the surface, and despite polls showing support for tariffs on energy and minerals among Canadians, it carries significant risks. Experts emphasize the importance of maintaining a stable energy export strategy to protect Quebec’s economy and preserve positive diplomatic relations with the U.S. Both countries have much to lose from further escalating trade tensions, and a more measured approach is likely to yield better outcomes in the long run.

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AI-Powered Utility Customer Experience enables transparency, real-time pricing, smart thermostats, demand response, and billing optimization, helping utilities integrate distributed energy resources, battery storage, and microgrids while boosting customer satisfaction and reducing costs.

Key Points

An approach where utilities use AI and real-time data to personalize service, optimize billing, and cut energy costs.

✅ Real-time pricing aligns retail and wholesale market signals

✅ Device control via smart thermostats and home energy management

✅ Analytics reveal appliance-level usage and personalized savings

The latest electric utility customer satisfaction survey results from the American Customer Satisfaction Index (ACSI) Energy Utilities report reveal that nearly every investor-owned utility saw customer satisfaction go down from 2018 to 2019. Residential customers are sending a clear message in the report: They want more transparency and control over energy usage, billing and ways to reduce costs.

With both customer satisfaction and utility revenues on the decline, utilities are facing daunting challenges to their traditional business models amid flat electricity demand across many markets today. That said, it is the utilities that see these changing times as an opportunity to evolve that will become the energy leaders of tomorrow, where the customer relationship is no longer defined by sales volume but instead by a utility company's ability to optimize service and deliver meaningful customer solutions.

We have seen how the proliferation of centralized and distributed renewables on the grid has already dramatically changed the cost profile of traditional generation and variability of wholesale energy prices. This signals the real cost drivers in the future will come from optimizing energy service with things like batteries, microgrids and peer-to-peer trading networks. In the foreseeable future, flat electricity rates may be the norm, or electricity might even become entirely free as services become the primary source of utility revenue.

The key to this future is technological innovation that allows utilities to better understand a customer’s unique needs and priorities and then deliver personalized, well-timed solutions that make customers feel valued and appreciated as their utility helps them save and alleviates their greatest pain points.

I predict utilities that adopt new technologies focused on customer experience, aligned with key utility trends shaping the sector, and deliver continual service improvements and optimization will earn the most satisfied, most loyal customers.

To illustrate this, look at how fixed pricing today is applied for most residential customers. Unless you live in one of the states with deregulated utilities where most customers are free to choose a service provider in a competitive marketplace, as consumers in power markets increasingly reshape offerings, fixed-rate tariffs or time-of-use tariffs might be the only rate structures you have ever known, though new utility rate designs are being tested nationwide today. These tariffs are often market distortions, bearing little relation to the real-time price that the utility pays on the wholesale market.

It can be easy enough to compare the rate you pay as a consumer and the market rate that utilities pay. The California ISO has a public dashboard -- as do other grid operators -- that shows the real-time marginal cost of energy. On a recent Friday, for example, a buyer in San Francisco could go to the real-time market and procure electricity at a rate of around 9.5 cents per kilowatt-hour (kWh), yet a residential customer can pay the utility PG&E between 22 cents and 49 cents per kWh amid major changes to electric bills being debated, depending on usage.

The problem is that utility customers do not usually see this data or know how to interpret it in a way that helps add value to their service or drive down the cost.

This is a scenario ripe for innovation. Artificial intelligence (AI) technologies are beginning to be applied to give customers the transparency and control over the energy they desire, and a new type of utility is emerging using real-time pricing signals from wholesale markets to give households hassle-free energy savings. Evolve Energy in Texas is developing a utility service model, even as Texas utilities revisit smart home network strategies, that delivers electricity to consumers at real-time market prices and connects to smart thermostats and other connected devices in the home for simple monitoring and control -- all managed via an intuitive consumer app.

My company, Bidgely, partners with utilities and energy retailers all over the world to apply artificial intelligence and machine learning algorithms to customer data in order to bring transparency to their electricity bills, showing exactly where the customers’ money is going down to the appliance and offering personalized, actionable advice on how to save.

Another example is from energy management company Keewi. Its wireless outlet adaptors are revealing real-time energy usage information to Texas A&M dorm residents as well as providing students the ability to conserve energy through controlling items in their rooms from their smartphones.

These are but a few examples of innovations among many in play that answer the consumer demand for increased transparency and control over energy usage.

Electric service providers will be closely watching how consumers respond to AI-driven innovation, including providers in traditionally regulated markets that are exploring equitable regulation approaches now, to stay aligned with policy and customer expectations. While regulated utilities have no reason to fear that their customers might sign up with a competitor, they understand that the revenues from electricity sales are going down and the deployment of distributed energy resources is going up. Both trends were reflected in a March report from Bloomberg New Energy Finance (via ThinkProgress) that claimed unsubsidized storage projects co-located with solar or wind are starting to compete with coal and gas for dispatchable power. Change is coming to regulated markets, and some of that change can be attributed to customer dissatisfaction with utility service.

Like so many industries before, the utility-customer relationship is on track to become less about measuring unit sales and more about driving revenue through services and delivering the best customer value. Loyal customers are most likely to listen and follow through on the utility’s advice and to trust the utility for a wide range of energy-related products and services. Utilities that make customer experience the highest priority today will emerge tomorrow as the leaders of a new energy service era.

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US energy mix shows how the electric grid blends renewables, fossil fuels, nuclear, and hydro, varying by ISO/RTO markets, utilities, and state policies, affecting carbon emissions, pricing, reliability, and access.

Key Points

The US energy mix is the grid's source breakdown by region: fossil fuels, renewables, nuclear, and hydro.

✅ Check ISO or RTO dashboards for real-time generation by fuel source.

✅ Utilities may offer green power plans or RECs at modest premiums.

✅ Energy mix shifts with policy, pricing, and grid reliability needs.

There are few resources more important than energy. Sure, you may die if you don't eat for days. But your phone will die if you go too long without charging it. Energy feeds tech, the internet, city infrastructure, refrigerators, lights, and has evolved throughout U.S. history in profound ways. You get the idea. Yet unlike our other common needs, such as food, energy sources aren't exactly front of mind for most people. 

"I think a lot of people don't put a lot of bandwidth into thinking about this part of their lives," said Richard McMahon, the SVP of energy supply and finance at Edison Electric Institute, a trade group that represents investor-owned electric companies in the US. 

It makes sense. For most Americans, electricity is always there, and in many locations, there's not much of a choice involved, even as electricity demand is flat across the U.S. today. You sign up with a utility when you move into a new residence and pay your bills when they're due. 

But there's an important reality that indifference eschews: In 2018, a third of the energy-related carbon-dioxide emissions in the US came from the electric power sector, according to the US Energy Information Administration (EIA). 

A good chunk of that is from the residential sector, which consistently uses more energy than commercial customers, per EIA data.

Just as many people exercise choice when they eat, you typically also have a choice when it comes to your energy supply. That's not to say your current offering isn't what you want, or that switching will be easy or affordable, but "if you're a customer and want power with a certain attribute," McMahon said, "you can pretty much get it wherever you are." 

But first, you need to know the energy mix you have right now. As it turns out, it's not so straightforward. At all.

This brief guide may help. 

For some utility providers, you can find out if it publishes the energy mix online. Dominion Energy, which serves Idaho, North Carolina, Ohio, South Carolina, Utah, Virginia, West Virginia, and Wyoming, provides this information in a colored graphic. 

"Once you figure out who your utility is you can figure out what mix of resources they use," said Heidi Ratz, an electricity markets researcher at the World Resources Institute.

But not all utilities publish this information.

It has to do with their role in the grid and reflects utility industry trends in structure and markets. Some utility companies are vertically integrated; they generate power through nuclear plants or wind farms and distribute those electrons directly to their customers. Other utilities just distribute the power that different companies produce. 

Consider Consolidated Edison, or Con Ed, which distributes energy to parts of New York City. While reporting this story, Business Insider could not find information about the utility's energy mix online. When reached for comment, a spokesperson said, "we're indifferent to where it comes from."

That's because, in New York, distribution utilities like Con Ed often buy energy through a wholesale marketplace.

Take a look at this map. If you live in one of the colored regions, your electricity is sold on a wholesale market regulated by an organization called a regional transmission organization (RTO) or independent system operator (ISO). Distribution utilities like Con Ed often buy their energy through these markets, based on availability and cost, while raising questions about future utility revenue models as prices shift. 

Still, it's pretty easy to figure out where your energy comes from. Just look up the ISO or RTO website (such as NYISO or CAISO). Usually, these organizations will provide energy supply information in near-real time. 

That's exactly what Con Edison (which buys energy on the NYISO marketplace) suggested. As of Friday morning, roughly 40% of the energy on the market place was natural gas or other fossil fuels, 34% was nuclear, and about 22% was hydro. 

If you live in another region governed by an ISO or RTO, such as in most of California, you can do the same thing. Like NYISO, CAISO has a dashboard that shows (again, as of Friday morning) about 36% of the energy on the market comes from natural gas and more than 20% comes from renewables. 

In the map linked above, you'll notice that some of the ISOs and RTOs like MISO encompass enormous regions. That means that even if you figure out where the energy in your market comes from, it's not going to be geographically specific. But there are a couple of ways to drill down even further. 

The Environmental Protection Agency has a straightforward tool called Power Profiler. You can enter your zip code to see the fuel mix in your area. But it's not perfect. The data are from 2016 and, in some regions of the country like the upper Midwest, they aren't much more localized, and some import dirty electricity due to regional trading. 

The World Resources Institute also has a tool that allows you to see the electricity mix by state, based on 2017 data from EIA. These numbers represent power generation, not the electricity actually flowing into your sockets, but they offer a rough idea of what energy resources are operating in your state. 

One option is to check with your utility to see if it has a "green power" offering. Over 600 utilities across the country have one, according to the Climate Reality Project, though they often come at a slightly higher cost. It's typically on the scale of just a few more cents per kilowatt-hour. 

There are also independent, consumer-facing companies like Arcadia and Green Mountain Energy that allow you to source renewable energy, by virtually connecting you to community solar projects or purchasing Renewable Energy Certificates, or RECs, on your behalf, as America goes electric and more options emerge. 

"RECs measure an investment in a clean energy resource," Ratz said, in an email. "The goal of putting that resource on the grid is to push out the need for dirtier resources."

The good news: Even if you do nothing, your energy mix will get cleaner. Coal production has fallen to lows not seen since the 1980s, amid disruptions in coal and nuclear sectors that affect reliability and costs, while renewable electricity generation has doubled since 2008. So whether you like it or not, you'll be roped into the clean energy boom one way or another. 

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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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