Wash those dishes during off-peak hours

By Toronto Star


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Dining fashionably late – really late – will get cheaper as Toronto Hydro moves to a new pricing system that charges residents different rates depending on when they use electricity.

The cheapest rates? Weekends, holidays and the overnight period from 10 p.m. to 7 a.m.

Most expensive? At least in summer, during the heat of the day, from 11 a.m. to 5 p.m. (Winter peak periods are different, covering morning and early evening hours.)

The high peak rates are intended to prompt consumers to use power-hungry appliances such as washers, dryers and air conditioners as little as possible during peak demand times.

On very hot and very cold days, demand can outstrip supply, causing brownouts and blackouts. Expensive generating stations must be built to cover these short periods – and sit idle most of the year.

The 10,000 randomly selected customers in Etobicoke, Scarborough and North York who will go on time-of-use rates starting June 1 are the latest to move to a system that should be in use province-wide by the end of next year. Customers of Milton Hydro and Newmarket Hydro are already using their so-called "smart meters" in this way.

The Toronto customers will get their first bills reflecting the new rates as early as August, and all single-family households in the city should be on them within the year. Customers will be notified before they're switched to the new rates.

The city core will be the last, because the meters needed to record the precise time of day power is used are still being installed there.

The new rates won't affect households without smart meters, meaning most rental apartments and some condos. But 611,000 households already have them – about 85 per cent of single-family home customers.

Householders currently pay 5.7 cents per kilowatt hour for the first 600 kW/h per month in summer; 6.6 cents beyond that. For a typical household, using about 1,000 kW/h per month, that averages to a little over 6 cents. (That represents the energy portion of the bill, about half the total; the rest pays for the wires and operating the system.)

Under the new system, the price on weekends and overnight drops to 4.2 cents, but rises to 9.1 cents during the peak, and 7.6 cents at other times of the day.

Toronto Hydro estimates that the average family will pay about 1 per cent more, or $1.25, on their overall bill if they stick with their current patterns. Customers who change their behaviour, on the other hand, may be able to shave a few dollars off the bill.

An example: Running a dishwasher at 8 p.m. currently costs about 22 cents per load. Under the new mid-peak rate, it will cost about 27 cents. But if you turn it on after 10 p.m., it will cost only 15 cents.

So, running the dishwasher after 10 p.m. four weeknights each week will save about $1.20 a month compared with current rates, and about $2 a month based on the new rates.

Mayor David Miller heartily endorsed the new rates, which he said will discourage waste and allow consumers to lower their energy bills.

"It doesn't make sense to do your laundry at noon on a very hot day when everybody has their air conditioning on," Miller said.

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Hydro once made up around half of Alberta's power capacity. Why does Alberta have so little now?

Alberta Hydropower Potential highlights renewable energy, dams, reservoirs, grid flexibility, contrasting wind and solar growth with limited investment, regulatory hurdles, river basin resources, and decarbonization pathways across Athabasca, Peace, and Slave River systems.

 

Key Points

It is the technical capacity for new hydro in Alberta's river basins to support a more reliable, lower carbon grid.

✅ 42,000 GWh per year developable hydro identified in studies.

✅ Major potential in Athabasca, Peace, and Slave River basins.

✅ Barriers include high capital costs, market design, water rights.

 

When you think about renewable energy sources on the Prairies, your mind may go to the wind farms in southern Alberta, or even the Travers Solar Project, southeast of Calgary.

Most of the conversation around renewable energy in the province is dominated by advancements in solar and wind power, amid Alberta's renewable energy surge that continues to attract attention. 

But what about Canada's main source of electricity — hydro power?

More than half of Canada's electricity is generated from hydro sources, with 632.2 terawatt-hours produced as of 2019. That makes it the fourth largest installed capacity of hydropower in the world. 

But in Alberta, it's a different story. 

Currently, hydro power contributes between three and five per cent of Alberta's energy mix, while fossil fuels make up about 89 per cent.

According to Canada's Energy Future report from the Canada Energy Regulator, by 2050 it will make up two per cent of the province's electricity generation shares.

So why is it that a province so rich in mountains and rivers has so little hydro power?


Hydro's history in Alberta
Hydro power didn't always make up such a small sliver of Alberta's electricity generation. Hydro installations began in the early 20th century as the province's population exploded. 

Grant Berg looks after engineering for hydro for TransAlta, Alberta's largest producer of hydro power with 17 facilities across the province.

"Our first plant was Horseshoe, which started in 1911 that we formed as Calgary Power," he said. 

"It was really in response to the City of Calgary growing and having some power needs."

Berg said in 1913, TransAlta's second installation, the Kananaskis Plant, started as Calgary continued to grow.

A historical photo of a hydro-electric dam in Kananaskis Alta. taken in 1914.
Hydro power plant in Kananaskis as seen in 1914. (Glenbow Archives)
Some bigger installations were built in the 1920s, including Ghost reservoir, but by mid-century population growth increased.

"Quite a large build out really, I think in response to the growth in Alberta following the war. So through the 1950s really quite a large build out of hydro from there."

By the 1950s, around half of the province's installed capacity was hydro power.

"Definitely Calgary power was all hydro until the 1950s," said Berg. 


Hydro potential in the province 
Despite the current low numbers in hydroelectricity, Alberta does have potential. 

According to a 2010 study, there is approximately 42,000 gigawatt-hours per year of remaining developable hydroelectric energy potential at identified sites. 

An average home in Alberta uses around 7,200 kilowatt-hours of electricity per year, meaning that the hydro potential could power 5.8 million homes each year. 

"This volume of energy could be sufficient to serve a significant amount of Alberta's load and therefore play a meaningful role in the decarbonization of the province's electric system," the Alberta Electric System Operator said in its 2022 Pathways to Net-Zero Emissions report.

Much of that potential lies in northern Alberta, in the Athabasca, Peace and Slave River basins.

The AESO report says that despite the large resource potential, Alberta's energy-only market framework has attracted limited investment in hydroelectric generation. 

Hydro power was once a big deal in Alberta, but investment in the industry has been in decline since the 1950s. Climate change reporter Christy Climenhaga explains why.
So why does Alberta leave out such a large resource potential on the path to net zero?

The government of Alberta responded to that question in a statement. 

"Hydro facilities, particularly large scale ones involving dams, are associated with high costs and logistical demands," said the Ministry of Affordability and Utilities. 

"Downstream water rights for other uses, such as irrigation, further complicate the development of hydro projects."

The ministry went on to say that wind and solar projects have increased far more rapidly because they can be developed at relatively lower cost and shorter timelines, and with fewer logistical demands.

"Sources from wind power and solar are increasingly more competitive," said Jean-Denis Charlebois, chief economist with the Canadian Energy Regulator. 


Hydro on the path to net zero
Hydro power is incredibly important to Canada's grid, and will remain so, despite growth in wind and solar power across the province.

Charlebois said that across Canada, the energy make-up will depend on the province. 

"Canadian provinces will generate electricity in very different ways from coast to coast. The major drivers are essentially geography," he said. 

Charlebois says that in British Columbia, Manitoba, Quebec and Newfoundland and Labrador, hydropower generation will continue to make up the majority of the grid.

"In Alberta and Saskatchewan, we see a fair bit of potential for wind and solar expansion in the region, which is not necessarily the case on Canada's coastlines," he said.

And although hydro is renewable, it does bring its adverse effects to the environment — land use changes, changes in flow patterns, fish populations and ecosystems, which will have to be continually monitored. 

"You want to be able to manage downstream effects; make sure that you're doing all the proper things for the environment," said Ryan Braden, director of mining and hydro at TransAlta.

Braden said hydro power still has a part to play in Alberta, even with its smaller contributions to the future grid. 

"It's one of those things that, you know, the wind doesn't blow or the sun doesn't shine, this is here. The way we manage it, we can really support that supply and demand," he said.

 

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Overturning statewide vote, Maine court energizes Hydro-Quebec's bid to export power

Maine Hydropower Transmission Line revived by high court after referendum challenge, advancing NECEC, Hydro-Quebec supply, Central Maine Power partnership, clean energy integration, grid reliability, and lower rates across New England pending land-lease ruling.

 

Key Points

A court-revived NECEC line delivering 1,200 MW of Hydro-Quebec hydropower via CMP to strengthen the New England grid.

✅ Maine high court deems retroactive referendum unconstitutional

✅ Pending state land lease case may affect final route

✅ Project could lower rates and cut emissions in New England

 

Maine's highest court on Tuesday breathed new life into a $1-billion US transmission line that aims to serve as conduit for Canadian hydropower, after construction starts drew scrutiny, ruling that a statewide vote rebuking the project was unconstitutional.

The Supreme Judicial Court ruled that the retroactive nature of the referendum last year violated the project developer's constitutional rights, sending it back to a lower court for further proceedings.

The court did not rule in a separate case that focuses on a lease for a 1.6-kilometre portion of the proposed power line that crosses state land.

Central Maine Power's parent company and Hydro-Québec teamed up on the project that would supply up to 1,200 megawatts of Canadian hydropower, amid the ongoing Maine-Quebec corridor debate in the region. That's enough electricity for one million homes.

Most of the proposed 233-kilometre power transmission line would be built along existing corridors, but a new 85-kilometre section was needed to reach the Canadian border, echoing debates around the Northern Pass clash in New Hampshire.

Workers were already clearing trees and setting poles when the governor asked for work to be suspended after the referendum in November 2021, mirroring New Hampshire's earlier rejection of a Quebec-Massachusetts proposal that rerouted regional plans. The Maine Department of Environmental Protection later suspended its permit, but that could be reversed depending on the outcome of legal proceedings.

The high court was asked to weigh in on two separate lawsuits. Developers sought to declare the referendum unconstitutional while another lawsuit focused on a lease allowing transmission lines to cross a short segment of state-owned land.

Supporters say bold projects such as this one, funded by ratepayers in Massachusetts, are necessary to battle climate change and introduce additional electricity into a region that's heavily reliant on natural gas, which can cause spikes in energy costs, as seen with Nova Scotia rate increases recently across the Atlantic region.

Critics say the project's environmental benefits are overstated — and that it would harm the woodlands in western Maine.

It was the second time the Supreme Judicial Court was asked to weigh in on a referendum aimed at killing the project. The first referendum proposal never made it onto the ballot after the court raised constitutional concerns.

Although the project is funded by Massachusetts ratepayers, the introduction of so much electricity to the grid would serve to stabilize or reduce electricity rates for all consumers, proponents contend, even as Manitoba Hydro rate hikes face opposition elsewhere.

The referendum on the project was the costliest in Maine history, topping $90 million US and underscoring deep divisions.

The high-stakes campaign put environmental and conservation groups at odds, and pitted utilities backing the project, amid the Hydro One-Avista backlash, against operators of fossil fuel-powered plants that stand to lose money.

 

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All-electric home sports big windows, small footprint

Cold-Climate Heat Pumps deliver efficient heating and cooling for Northern B.C. Net Zero Ready homes, with air-source Mitsubishi H2i systems, triple-pane windows, blower door ACH 0.8, BC Hydro rebates, and CleanBC incentives.

 

Key Points

Electric air-source systems that heat and cool in subzero climates, cutting emissions and lowering energy costs.

✅ Net Zero Ready, Step Code 5, ACH 0.8 airtightness

✅ Operate efficiently to about -28 C with backup heat

✅ Eligible for BC Hydro and CleanBC rebates

 

Heat pump provides heating, cooling in northern B.C. home
It's a tradition at Vanderhoof-based Northern Homecraft that, on the day of the blower door test for a just-completed home, everyone who worked on the build gathers to watch it happen. And in the spring of 2021, on a dazzling piece of land overlooking the mouth of the Stuart River near Fort St. James, that day was a cause for celebration.

A new 3,400-square foot home subjected to the blower door test – a diagnostic tool to determine how much air is entering or escaping from a home – was rated as having just .8 air changes per hour (ACH). That helps make it a Net Zero Ready home, and BC Energy Code Step 5 compliant. That means it would take about a third of the amount of energy to heat the home compared to a typical similar-sized home in B.C. today.

From an energy-efficiency perspective, this is a home whose evident beauty is anything but skin deep.

"The home has lot of square footage of finished living space, and it also has a lot of glazing," says Northern Homecraft owner Shay Bulmer, referring to the home's large windows. "We had a lot of window space to deal with, as well as large vaulted open areas where you can only achieve so much additional insulation. There were a few things that the home had going against it as far as performance goes. There were challenges in keeping it comfortable year-round."


Well-insulated home ideal for heat pump option
Most homes in colder areas of B.C. lean on gas-fueled heating systems to deal with the often long, chilly winters. But with the arrival of cold climate heat pumps capable of providing heat efficiently when temperatures dip as low as -30°C, there's now a clean option for those homes, and using more electricity for heat is gaining support in the North as well.

Heat pumps are an increasingly popular option, both for new and existing homes, because they avoid carbon emissions associated with fossil use while also offering summer cooling, even as record-high electricity demand in Yukon underscores the need for efficient systems.

The Fort St. James home, which was built with premium insulation, airtightness and energy efficiency in mind, made the decision to opt for a heat pump even easier. Still, the heat pump option took the home's owners Dexter and Cheryl Hodder by surprise. While their focus was on designing a home that took full advantage of views down to the river, the couple was under the distinct impression that heat pumps couldn't cut it in the chilly north.

"I wasn't really considering a heat pump, which I thought was only a good solution in a moderate climate," says Dexter, who as director of research and education for the John Prince Research Forest, studies wildlife and forestry interactions in north central B.C. "The specs on the heat pump indicate it would work down to -28°C, and I was skeptical of that. But it worked exactly to spec. It almost seems ridiculous to generate heat from outside air at those low temperatures, but it does."

 

Getting it right with support and rebates
Northern Homecraft took advantage of BC Hydro's Mechanical System Design Pilot program to ensure proper heat pump system design, installation, and verification for the home were applied, and with BC Hydro's first call for power in 15 years driven by electrification, the team prioritized efficient load management.

Based on the home's specific location, size, and performance targets, they installed a ducted Mitsubishi H2I air-source heat pump system. Windows are triple pane, double coated, and a central feature of the home, while insulation specifications were R-40 deep frame insulation in the exterior walls, R-80 insulation in the attic, and R-40 insulation in the vaulted ceilings.

The combination of the year-round benefits of heat pumps, their role in reducing fossil fuel emissions, and the availability of rebates, is making the systems increasingly attractive in B.C., especially as two new BC generating stations were recently commissioned to expand clean supply.

BC Hydro offers home renovation rebates of up to $10,000 for energy-efficient upgrades to existing homes. Rebates are available for windows and doors, insulation, heat pumps, and heat pump hot water heaters. In partnership with CleanBC, rebates of up to $11,000 are also available – when combined with the federal Greener Homes program – for those switching from fossil fuel heating to an electric heat pump.


'Heat dome' pushes summer highs to 40°C
Cooling wasn't really a consideration for Dexter and Cheryl when they were living in a smaller bungalow shaded by trees. But they knew that with the big windows, vaulted ceiling in the living room, and an upstairs bedroom in the new home, there may come a time when they needed air conditioning.

That day arrived shortly after the home was built, as the infamous "heat dome" settled on B.C. and drove temperatures at Fort St. James to a dizzying 40°C.

"It was disgustingly hot, and I don't care if I never see that again here," says Hodder, with a laugh. "But the heat pump maintained the house really nicely throughout, at about 22 degrees. The whole house stayed cool. We just had to close the door to the upper bedroom so it wasn't really heating up during the day."

Hodder says he had to work with the heat pump manufacturer Mitsubishi a couple times over that first year to fix a few issues with the system's controls. But he's confident that the building's tight and well-insulated envelope, and the heat pump's backup electric heat that kicks in when temperatures dip below -28°C, will make it the system-for-all-seasons it was designed to be.

Even with the use of supplemental electric heating during the record chill of December-January, the home's energy costs weren't much higher than the mid-winter energy bills they used to pay in the couple's smaller bungalow that relied on a combination of gas-fired in-floor heating and electric baseboards, as gas-for-electricity swaps are being explored elsewhere.

Fort St. James is a former fur trading post located northwest of Prince George and a short drive north of Vanderhoof. Winters are cold and snowy, with average daily low temperatures in December and January of around -14°C.

"During the summer and into the fall, we were paying well less than $100 a month," says Hodder, looking back at electricity bills over the first year in the home. "And that's everything. We're only electric here, and we also had both of us working from home all last year."

 

Word of mouth making heat pumps popular in Fort St. James
While the size of the home presented new challenges for the builders, it's one of five Net Zero Ready or Net Zero homes – all equipped with some form of heat pump – that Northern Homecraft has built in Fort St. James, even as debates about going nuclear for electricity continue in B.C.

The smallest of the homes is a two-bedroom, one-bathroom home that's just under 900 square feet. Northern Homecraft may be based in Vanderhoof, but it's the much smaller town of Fort St. James where they're making their mark with super-efficient homes. Net Zero Ready homes are up to 80% more efficient than the standard building code, and become Net Zero once renewable energy generation – usually in the form of photovoltaic solar – is installed, and programs like switching 5,000 homes to geothermal show the broader momentum for clean heating.

"We were pretty proud that the first home we built in Fort St. James was the first single family Net Zero Ready home built in B.C.," says Northern Homecraft's Bulmer. "And I think it's kind of caught on in a smaller community where everyone talks to everyone."

 

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N.S. senior suspects smart meter to blame for shocking $666 power bill

Nova Scotia Power smart meter billing raises concerns amid estimated billing, catch-up bills, and COVID-19 meter reading delays, after seniors report doubled electricity usage and higher utility charges despite consistent consumption and on-time payments.

 

Key Points

Smart meter billing uses digital reads, limits estimates, and may trigger catch-up charges after reading suspensions.

✅ COVID-19 reading pause led to estimated bills and later catch-ups

✅ Smart meters reduce reliance on estimated billing errors

✅ Customers can seek payment plans and bill reviews

 

A Nova Scotia senior says she couldn't believe her eyes when she opened her most recent power bill. 

Gloria Chu was billed $666 -- more than double what she normally pays, and similar spikes such as rising electricity bills in Calgary have drawn attention.

As someone who always pays her bi-monthly Nova Scotia Power bill in full and on time, Chu couldn't believe it.

According to her bill, her electricity usage almost tripled during the month of May, compared to last year, and is even more than it was last winter, and with some utilities exploring seasonal power rates customers may see confusing swings.

She insists she and her husband aren't doing anything differently -- but one thing has changed.

"I have had a problem since they put the smart meter in," said Chu, who lives in Upper Gulf Shore, N.S.

Chu got a big bill right after the meter was installed in January, too. That one was more than $530.

She paid it, but couldn't understand why it was so high.

As for this bill, she says she just can't afford it, especially amid a recently approved 14% rate hike in Nova Scotia.

"That's all of my CPP," Chu said. "Actually, it's more than my CPP."

Chu says a neighbor up the road who also has a smart meter had her bill double, too. In nearby Pugwash, she says some residents have seen an increase of about $20-$30.

Nova Scotia Power had put a pause on installing smart meters because of the COVID-19 pandemic, but it has resumed as of June 1, with the goal of upgrading 500,000 meters by 2021, even as in other provinces customers have faced fees for refusing smart meters during similar rollouts.

In this case, the utility says it's not the meter that's the problem, and notes that in New Brunswick some old meters gave away free electricity even as the pandemic forced Nova Scotia Power to suspend meter readings for two months.

"As a result, every one of our customers in Nova Scotia received an estimated bill," said Jennifer parker, Nova Scotia Power's director of customer care.

The utility estimated Chu's bill at $182 -- less than she normally pays -- so her latest bill is considered a catch-up bill after meter readings resumed last month.

Parker admits how estimates are calculated isn't perfect.

"There would be a lot of customers who probably had a more accurate bill because of the way that we estimate, and that's actually one of things that smart meters will get rid of, is that we won't need to do estimated billing," Parker said.

Chu isn't quite convinced.

"It is pretty smart for the power company, but it's not smart for us," she said with a laugh.

Nova Scotia Power has put a hold on her bill and says it will work with Chu on an affordable solution, though the province cannot order the utility to lower rates which limits what can be offered.

She just hopes to never see a big bill like this again, while elsewhere in Newfoundland and Labrador a lump-sum electricity credit is being provided to help customers.

 

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Experts warn Albertans to lock in gas and electricity rates as prices set to soar

Alberta Energy Price Spike signals rising electricity and natural gas costs; lock in fixed rates as storage is low, demand surged in heat waves, and exports rose after Hurricane Ida, driving volatility and higher futures.

 

Key Points

An anticipated surge in Alberta electricity and natural gas prices, urging consumers to lock fixed rates to reduce risk.

✅ Fixed-rate gas near $3.79/GJ vs futures approaching $6/GJ

✅ Low storage after heat waves and U.S. export demand

✅ Switch providers or plans; UCA comparison tool helps

 

Energy economists are warning Albertans to review their gas and electricity bills and lock in a fixed rate if they haven't already done so because prices are expected to spike in the coming months.

"I have been urging anyone who will listen that every single Albertan should be on a fixed rate for this winter," University of Calgary energy economist Blake Shaffer said Monday. "And I say that for both natural gas and power."

Shaffer said people will rightly point out energy costs make up only roughly a third of their monthly bill. The rest of the costs for such things as delivery fees can't be avoided. 

But, he said, "there is an energy component and it is meaningful in terms of savings." 

For example, Shaffer said, when he checked last week, a consumer could sign a fixed rate gas contract for $3.79 a gigajoule and the current future price for gas is nearly $6 a gigajoule.

A typical household would use about 15 gigajoules a month, he said, so a consumer could save $30 to $45 a month for five months. For people on lower or fixed incomes, "that is a pretty significant saving."

Comparable savings can also be achieved with electricity, he said.

Shaffer said research has shown households that are least able to afford sharp increases in gas and electrical bills are less likely to pick up the phone and call their energy provider and either negotiate a lower fixed rate contract or jump to a new provider. 

But, he said, it is definitely worth the time and effort, particularly as Calgary electricity bills are rising across the city. Alberta's Utilities Consumer Advocate has a handy cost comparison tool on its website that allows consumers to conduct regional price comparisons that will assist in making an informed decision.

"Folks should know that for most providers you can change back to a floating rate any time you want," Shaffer said.

Summer heat wave affected natural gas supply
Why are energy prices set to spike in Alberta, which is a major producer of natural gas?

Sophie Simmonds, managing director of the brokerage firm Anova Energy, said Alberta is now generating the majority of its power using natural gas. 

The heat wave in June and July created record electrical demand. Normally, natural gas is stored in the summer for use in the winter. But this year, there was much greater gas consumption in the summer and so less was stored. 

Alberta also set a new electricity usage record during a recent deep freeze, underscoring system stress.

On top of that, Alberta has been exporting much more natural gas to the United States since August and September because Hurricane Ida knocked out natural gas assets in the Gulf of Mexico.

"So what this means is we are actually going into winter with very, very low storage numbers," Simmonds said.

Why natural gas prices have surged to some of their highest levels in years
Canadians to remain among world's top energy users even as government strives for net zero
Consultant Matt Ayres said he believes rising electricity prices also are being affected by Alberta's transition from carbon-intensive fuel sources to less carbon-intensive fuel sources.

"That transition is not always smooth," said Ayres, who is also an adjunct assistant professor at the University of Calgary's School of Public Policy. 

"It is my view that at least some of the price increases we are seeing on electricity comes down to difficulties imposed by that transition and also by a reduction in competition amongst generators, as well as power market overhaul debates shaping policy." 

In 2019, under the leadership of Premier Jason Kenney the UCP government removed the former NDP government's rate cap on electricity at the time.

The NDP has called for the government to reinstate the cap but the UCP government has dismissed that as unsustainable and unrealistic.

 

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Brand New Renewable Technology Harnesses Electricity From The Cold, Dark Night

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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