The top 10 facts about zapping trash with plasma

By Discovery Channel


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The scoop: Plasma is a collection of charged particles that respond to an electromagnetic field (think lightning and the sun). In Florida and California, cities are looking at ways to use plasma to obliterate garbage and use the heat to generate power.

But initial plans in Florida to build the largest plasma arc gasification plant in the world have been scaled back by about 80 percent. And in Sacramento, the proposed plant has been put on hold because of a lack of details about just how much electricity would be produced and how much trash would be gasified by plasma.

But why were folks looking into plasma in the first place? Expert Louis Circeo gives a list of his top 10 reasons for zapping garbage with plasma.

1. It reduces the need for landfills.

Sometimes called "artificial lightning," plasma can have temperatures that can exceed 7,000 degrees centigrade — that's three times hotter than fossil fuels and hotter than the surface of the sun. The plasma arc would instantly convert organic materials into synthetic gas, often called "syngas," and melt inorganic materials, which when cooled, become rock-like and can be sold as construction materials. With no remaining waste to deal with, landfills become obsolete.

2. Existing landfills could be mined for energy.

In many regions of the United States, it would be more cost-effective to take municipal solid waste to a plasma gasification plant for energy production than to dump it in a landfill. When plasma gasification is fully developed, even existing landfills could be economically mined for energy production, environmental cleanup and land reuse.

3. It's energy efficient.

Plasma gasification of 1 ton of average municipal solid wastes would send about 815 Kilowatt-hours of electricity to the grid. This is 20 to 50 percent more electricity to the grid than any other emerging thermal waste-to-energy technology. In addition, this amount of power is over six times the electricity required to conduct the plasma gasification process.

4. It's working in other countries.

Since 2002, two commercial waste-to-energy plasma gasification plants have been operating successfully in Japan. The Mihama-Mikata facility processes 24 tons of municipal sold waste and 4 tons of sewage sludge per day, producing steam and hot water for local use. The Utashinai plant processes up to 300 tons per day of waste and/or automobile shredder residue. This facility produces up to 7.9 Megawatts of electricity, of which 3.6 MW are used to run the plasma torches and the plant, and up to 4.3 MW are sent to the electrical power grid. In Ottawa, Canada, people are evaluating a demonstration facility that is currently processing 94 tons of waste per day, sending 4 MW of power to the grid.

5. It could produce ethanol fuel.

If all the municipal solid waste in the United States was processed by plasma gasification, over 5 percent of the U.S. electrical energy requirements could be produced. This amount of power is equal to the amount of hydropower produced in the United States, or equal to about 25 nuclear power plants. Similarly, the 2007 U.S. Energy Act recommends that "garbage" be used to replace edible foods such as corn to produce ethanol. It was estimated that waste could produce up to 30 percent of the 36 billion gallons of ethanol required by the year 2022.

6. It could produce the most renewable energy.

Plasma processing of municipal solid waste in the United States has the potential to create more renewable energy than the projected energy from solar, wind, landfill gas and geothermal energies combined.

7. It's clean burning.

Because of the high temperatures, the low volume of gas emissions and the dissociation of organic compounds, gaseous emissions from plasma waste processes are much cleaner than from other kinds of gasification or incineration processes.

8. It reduces greenhouse gas emissions.

In landfills, garbage produces methane, a greenhouse gas. But if that garbage were sent to a plasma gasification facility, it would not have a chance to produce methane. What's more, the energy generated could replace energy made at a coal-fired plant. In fact, for every ton of municipal solid waste sent to a plasma gasification facility for power production, 2 tons of CO2 emissions could be reduced from the atmosphere.

9. It gasifies more than garbage.

At least 15 companies in the United States and Canada are actively developing plasma gasification projects. In addition to municipal solid waste, the plants will process industrial waste, biomass, coal, coke and other carbonaceous materials. The plants will produce electricity as well as ethanol, methanol, diesel fuel, hydrogen and other syngas-based fuel products. Construction on some of these facilities is expected to begin in 2009.

10. It has a future.

Plasma gasification could play even more important roles in the fields of clean coal gasification, secondary oil recovery, and oil shale and tar sands recovery processes. Truly. Plasma gasification is an incipient environmental blockbuster, ready to leap ahead of current concepts of waste disposal, energy production and environmental cleanup.

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UK Lockdown knocks daily electricity demand by 10 per cent

Britain Electricity Demand During Lockdown is around 10 percent lower, as industrial consumers scale back. National Grid reports later morning peaks and continues balancing system frequency and voltage to maintain grid stability.

 

Key Points

Measured drop in UK power use, later morning peaks, and grid actions to keep frequency and voltage within safe limits.

✅ Daily demand about 10 percent lower since lockdown.

✅ Morning peak down nearly 18 percent and occurs later.

✅ National Grid balances frequency and voltage using flexible resources.

 

Daily electricity demand in Britain is around 10% lower than before the country went into lockdown last week due to the coronavirus outbreak, data from grid operator National Grid showed on Tuesday.

The fall is largely due to big industrial consumers using less power across sectors, the operator said.

Last week, Prime Minister Boris Johnson ordered Britons to stay at home to halt the spread of the virus, imposing curbs on everyday life without precedent in peacetime.

Morning peak demand has fallen by nearly 18% compared to before the lockdown was introduced and the normal morning peak is later than usual because the times people are getting up are later and more spread out with fewer travelling to work and school, a pattern also seen in Ottawa during closures, National Grid said.

Even though less power is needed overall, the operator still has to manage lower demand for electricity, as well as peaks, amid occasional short supply warnings from National Grid, and keep the frequency and voltage of the system at safe levels.

Last August, a blackout cut power to one million customers and caused transport chaos as almost simultaneous loss of output from two generators caused by a lightning strike caused the frequency of the system to drop below normal levels, highlighting concerns after the emergency energy plan stalled.

National Grid said it can use a number of tools to manage the frequency, such as working with flexible generators to reduce output or draw on storage providers to increase demand, and market conditions mean peak power prices have spiked at times.

 

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Which of the cleaner states imports dirty electricity?

Hourly Electricity Emissions Tracking maps grid balancing areas, embodied emissions, and imports/exports, revealing carbon intensity shifts across PJM, ERCOT, and California ISO, and clarifying renewable energy versus coal impacts on health and climate.

 

Key Points

An hourly method tracing generation, flows, and embodied emissions to quantify carbon intensity across US balancing areas.

✅ Hourly traces of imports/exports and generation mix

✅ Consumption-based carbon intensity by balancing area

✅ Policy insights for renewables, coal, health costs

 

In the United States, electricity generation accounts for nearly 30% of our carbon emissions. Some states have responded to that by setting aggressive renewable energy standards; others are hoping to see coal propped up even as its economics get worse. Complicating matters further is the fact that many regional grids are integrated, and as America goes electric the stakes grow, meaning power generated in one location may be exported and used in a different state entirely.

Tracking these electricity exports is critical for understanding how to lower our national carbon emissions. In addition, power from a dirty source like coal has health and environment impacts where it's produced, and the costs of these aren't always paid by the parties using the electricity. Unfortunately, getting reliable figures on how electricity is produced and where it's used is challenging, even for consumers trying to find where their electricity comes from in the first place, leaving some of the best estimates with a time resolution of only a month.

Now, three Stanford researchers—Jacques A. de Chalendar, John Taggart, and Sally M. Benson—have greatly improved on that standard, and they have managed to track power generation and use on an hourly basis. The researchers found that, of the 66 grid balancing areas within the United States, only three have carbon emissions equivalent to our national average, and they have found that imports and exports of electricity have both seasonal and daily changes. de Chalendar et al. discovered that the net results can be substantial, with imported electricity increasing California's emissions/power by 20%.

Hour by hour
To figure out the US energy trading landscape, the researchers obtained 2016 data for grid features called balancing areas. The continental US has 66 of these, providing much better spatial resolution on the data than the larger grid subdivisions. This doesn't cover everything—several balancing areas in Canada and Mexico are tied in to the US grid—and some of these balancing areas are much larger than others. The PJM grid, serving Pennsylvania, New Jersey, and Maryland, for example, is more than twice as large as Texas' ERCOT, in a state that produces and consumes the most electricity in the US.

Despite these limitations, it's possible to get hourly figures on how much electricity was generated, what was used to produce it, and whether it was used locally or exported to another balancing area. Information on the generating sources allowed the researchers to attach an emissions figure to each unit of electricity produced. Coal, for example, produces double the emissions of natural gas, which in turn produces more than an order of magnitude more carbon dioxide than the manufacturing of solar, wind, or hydro facilities. These figures were turned into what the authors call "embodied emissions" that can be traced to where they're eventually used.

Similar figures were also generated for sulfur dioxide and nitrogen oxides. Released by the burning of fossil fuels, these can both influence the global climate and produce local health problems.

Huge variation
The results were striking. "The consumption-based carbon intensity of electricity varies by almost an order of magnitude across the different regions in the US electricity system," the authors conclude. The low is the Bonneville Power grid region, which is largely supplied by hydropower; it has typical emissions below 100kg of carbon dioxide per megawatt-hour. The highest emissions come in the Ohio Valley Electric region, where emissions clear 900kg/MW-hr. Only three regional grids match the overall grid emissions intensity, although that includes the very large PJM (where capacity auction payouts recently fell), ERCOT, and Southern Co balancing areas.

Most of the low-emissions power that's exported comes from the Pacific Northwest's abundant hydropower, while the Rocky Mountains area exports electricity with the highest associated emissions. That leads to some striking asymmetries. Local generation in the hydro-rich Idaho Power Company has embodied emissions of only 71kg/MW-hr, while its imports, coming primarily from Rocky Mountain states, have a carbon content of 625kg/MW-hr.

The reliance on hydropower also makes the asymmetry seasonal. Local generation is highest in the spring as snow melts, but imports become a larger source outside this time of year. As solar and wind can also have pronounced seasonal shifts, similar changes will likely be seen as these become larger contributors to many of these regional grids. Similar things occur daily, as both demand and solar production (and, to a lesser extent, wind) have distinct daily profiles.

The Golden State
California's CISO provides another instructive case. Imports represent less than 30% of its total electric use in 2016, yet California electricity imports provided 40% of its embodied emissions. Some of these, however, come internally from California, provided by the Los Angeles Department of Water and Power. The state itself, however, has only had limited tracking of imported emissions, lumping many of its sources as "other," and has been exporting its energy policies to Western states in ways that shape regional markets.

Overall, the 2016 inventory provides a narrow picture of the US grid, as plenty of trends are rapidly changing our country's emissions profile, including the rise of renewables and the widespread adoption of efficiency measures and other utility trends in 2017 that continue to evolve. The method developed here can, however, allow for annual updates, providing us with a much better picture of trends. That could be quite valuable to track things like how the rapid rise in solar power is altering the daily production of clean power.

More significantly, it provides a basis for more informed policymaking. States that wish to promote low-emissions power can use the information here to either alter the source of their imports or to encourage the sites where they're produced to adopt more renewable power. And those states that are exporting electricity produced primarily through fossil fuels could ensure that the locations where the power is used pay a price that includes the health costs of its production.

 

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Class-action lawsuit: Hydro-Québec overcharged customers up to $1.2B

Hydro-QuE9bec Class-Action Lawsuit alleges overbilling and monopoly abuse, citing RE9gie de l'E9nergie rate increases, Quebec Superior Court filings, and calls for refunds on 2008-2013 electricity bills to residential and business customers.

 

Key Points

Quebec class action alleging Hydro-QuE9bec overbilled customers in 2008-2013, seeking court-ordered refunds.

✅ Filed in Quebec Superior Court; certification pending.

✅ Alleges up to $1.2B in overcharges from 2008-2013.

✅ Questions RE9gie de l'E9nergie rate approvals and data.

 

A group representing Hydro-Québec customers has filed a motion for a class-action lawsuit against the public utility, alleging it overcharged customers over a five-year period.

Freddy Molima, one of the representatives of the Coalition Peuple allumé, accuses Hydro-Québec of "abusing its monopoly."

The motion, which was filed in Quebec Superior Court, claims Hydro-Québec customers paid more than they should have for electricity between 2008 and 2013, to the tune of nearly $1.2 billion, even as Hydro-Québec later refunded $535 million to customers in a separate case. 

The coalition has so far recruited nearly 40,000 participants online as part of its plan to sue the public utility.

A lawyer representing the group said Quebec's energy board, the Régie de l'énergie, also recently approved Hydro-Québec rate increases for residential and business customers without knowing all the facts, even as Manitoba Hydro hikes face opposition in regulatory hearings.

"There's certain information provided to the Régie that isn't true," said Bryan Furlong. "Hydro-Québec has not been providing the Régie the proper numbers."

In its motion, the group asks that overcharged clients be retroactively reimbursed.

Hydro-Québec denies allegations

Hydro-Québec, for its part, denies it ever overbilled any of its clients, while other utilities such as Hydro One plan to redesign bills to improve clarity.

"All our efficiencies have been returned to the government through our profits, and to Quebecers we have billed exactly what we agreed to bill," said spokesperson Serge Abergel, adding that the utility won't seek a rate hike next year according to its current plans.

Quebec Energy Minister Pierre Moreau also came to the public utility's defence, saying it has no choice but to comply with the  energy board's regulations, while customer protections are in focus as Hydro One moves to reconnect 1,400 customers in Ontario.

The group says the public utility has overbilled clients by up to $1.2 billion. (Radio-Canada)

It would be "shocking" if customers were charged too much money, he added.

"I know for a fact that Hydro-Québec is respecting the decision of this body," he said.

While the motion has been filed, the group cannot say how much each customer would receive if the class-action lawsuit goes ahead because it all depends on how much electricity was consumed by each client over that five-year period.

The coalition plans to present its motion to a judge next February.

 

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U.S. Department of Energy Announces $110M for Carbon Capture, Utilization, and Storage

DOE CCUS Funding advances carbon capture, utilization, and storage with FEED studies, regional deployment, and CarbonSAFE site characterization, leveraging 45Q tax credits to scale commercial CO2 reduction across fossil energy sectors.

 

Key Points

DOE CCUS Funding are federal FOAs for commercial carbon capture, storage, and utilization via FEED and CarbonSAFE.

✅ $110M across FEED, Regional, and CarbonSAFE FOAs

✅ Supports Class VI permits, NEPA, and site characterization

✅ Enables 45Q credits and enhanced oil recovery utilization

 

The U.S. Department of Energy’s (DOE’s) Office of Fossil Energy (FE) has announced approximately $110 million in federal funding for cost-shared research and development (R&D) projects under three funding opportunity announcements (FOAs), alongside broader carbon-free electricity investments across the power sector.

Approximately $75M is for awards selected under two FOAs announced earlier this fiscal year; $35M is for a new FOA.

These FOAs further the Administration’s commitment to strengthening coal while protecting the environment. Carbon capture, utilization, and storage (CCUS) is increasingly becoming widely accepted as a viable option for fossil-based energy sources—such as coal- or gas-fired power plants under new EPA power plant rules and other industrial sources—to lower their carbon dioxide (CO2) emissions.

DOE’s program has successfully deployed various large-scale CCUS pilot and demonstration projects, and it is imperative to build upon these learnings to test, mature, and prove CCUS technologies at the commercial scale. A recent study by Science of the Total Environment found that DOE is the most productive organization in the world in the carbon capture and storage field.

“This Administration is committed to providing cost-effective technologies to advance CCUS around the world,” said Secretary Perry. “CCUS technologies are vital to ensuring the United States can continue to safely use our vast fossil energy resources, and we are proud to be a global leader in this field.”

“CCUS technologies have transformative potential,” said Assistant Secretary for Fossil Energy Steven Winberg. “Not only will these technologies allow us to utilize our fossil fuel resources in an environmentally friendly manner, but the captured CO2 can also be utilized in enhanced oil recovery and emerging CO2-to-electricity concepts, which would help us maximize our energy production.”

Under the first FOA award, Front-End Engineering Design (FEED) Studies for Carbon Capture Systems on Coal and Natural Gas Power Plants, DOE has selected nine projects to receive $55.4 million in federal funding for cost-shared R&D. The selected projects will support FEED studies for commercial-scale carbon capture systems. Find project descriptions HERE. 

Under the second FOA award, Regional Initiative to Accelerate CCUS Deployment, DOE selected four projects to receive up to $20 million in federal funding for cost-shared R&D. The projects also advance existing research and development by addressing key technical challenges; facilitating data collection, sharing, and analysis; evaluating regional infrastructure, including CO2 storage hubs and pipelines; and promoting regional technology transfer. Additionally, this new regional initiative includes newly proposed regions or advanced efforts undertaken by the previous Regional Carbon Sequestration Partnerships (RCSP) Initiative. Find project descriptions HERE. 

Elsewhere in North America, provincial efforts such as Quebec's and industry partners like Cascades are investing in energy efficiency projects to complement emissions-reduction goals.

Under the new FOA, Carbon Storage Assurance Facility Enterprise (CarbonSAFE): Site Characterization and CO2 Capture Assessment, DOE is announcing up to $35 million in federal funding for cost-shared R&D projects that will accelerate wide-scale deployment of CCUS through assessing and verifying safe and cost-effective anthropogenic CO2 commercial-scale storage sites, and carbon capture and/or purification technologies. These types of projects have the potential to take advantage of the 45Q tax credit, bolstered by historic U.S. climate legislation, which provides a tax credit for each ton of CO2 sequestered or utilized. The credit was recently increased to $35/metric ton for enhanced oil recovery and $50/metric ton for geologic storage.

Projects selected under this new FOA shall perform the following key activities: complete a detailed site characterization of a commercial-scale CO2 storage site (50 million metric tons of captured CO2 within a 30 year period); apply and obtain an underground injection control class VI permit to construct an injection well; complete a CO2capture assessment; and perform all work required to obtain a National Environmental Policy Act determination for the site.

 

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Nonstop Records For U.S. Natural-Gas-Based Electricity

U.S. Natural Gas Power Demand is surging for electricity generation amid summer heat, with ERCOT, Texas grid reserves tight, EIA reporting coal and nuclear retirements, renewables intermittency, and pipeline expansions supporting combined-cycle capacity and prices.

 

Key Points

It is rising use of natural gas for power, driven by summer heat, plant retirements, and new combined-cycle capacity.

✅ ERCOT reserve margin 9%, below 14% target in Texas

✅ Gas share of U.S. power near 40-43% this summer

✅ Coal and nuclear retirements shift capacity to combined cycle

 

As the hot months linger, it will be natural gas that is leaned on most to supply the electricity that we need to run our air conditioning loads on the grid and keep us cool.

And this is surely a great and important thing: "Heat causes most weather-related deaths, National Weather Service says."

Generally, U.S. gas demand for power in summer is 35-40% higher than what it was five years ago, with so much more coming (see Figure).

The good news is regions across the country are expected to have plenty of reserves to keep up with power demand.

The only exception is ERCOT, covering 90% of the electric load in Texas, where a 9% reserve margin is expected, below the desired 14%.

Last summer, however, ERCOT’s reserve margin also was below the desired level, yet the grid operator maintained system reliability with no load curtailments.

Simply put, other states are very lucky that Texas has been able to maintain gas at 50% of its generation, despite being more than justified to drastically increase that.

At about 1,600 Bcf per year, the flatness of gas for power demand in Texas since 2000 has been truly remarkable, especially since Lone Star State production is up 50% since then.

Increasingly, other U.S. states (and even countries) are wanting to import huge amounts of gas from Texas, a state that yields over 25% of all U.S. output.

Yet if Texas justifiably ever wants to utilize more of its own gas, others would be significantly impacted.

At ~480 TWh per year, if Texas was a country, it would be 9th globally for power use, even ahead of Brazil, a fast growing economy with 212 million people, and France, a developed economy with 68 million people.

In the near-term, this explains why a sweltering prolonged heat wave in July in Texas, with a hot Houston summer setting new electricity records, is the critical factor that could push up still very low gas prices.

But for California, our second highest gas using state, above-average snowpack should provide a stronger hydropower for this summer season relative to 2018.

Combined, Texas and California consume about 25% of U.S. gas, with Texas' use double that of California.

 

Across the U.S., gas could supply a record 40-43% of U.S. electricity this summer even as the EIA expects solar and wind to be larger sources of generation across the mix

Our gas used for power has increased 35-40% over the past five years, and January power generation also jumped on the year, highlighting broad momentum.

Our gas used for power has increased 35-40% over the past five years. DATA SOURCE: EIA; JTC

Indeed, U.S. natural gas for electricity has continued to soar, even as overall electricity consumption has trended lower in some years, at nearly 10,700 Bcf last year, a 16% rise from 2017 and easily the highest ever.

Gas is expected to supply 37% of U.S. power this year, even as coal-fired generation saw a brief uptick in 2021 in EIA data, versus 27% just five years ago (see Figure).

Capacity wise, gas is sure to continue to surge its share 45% share of the U.S. power system.

"More than 60% of electric generating capacity installed in 2018 was fueled by natural gas."

We know that natural gas will continue to be the go-to power source: coal and nuclear plants are retiring, and while growing, wind and solar are too intermittent, geography limited, and transmission short to compensate like natural gas can.

"U.S. coal power capacity has fallen by a third since 2010," and last year "16 gigawatts (16,000 MW) of U.S. coal-fired power plants retired."

This year, some 2,000 MW of coal was retired in February alone, with 7,420 MW expected to be closed in 2019.

Ditto for nuclear.

Nuclear retirements this year include Pilgrim, Massachusetts’s only nuclear plant, and Three Mile Island in Pennsylvania.

This will take a combined ~1,600 MW of nuclear capacity offline.

Another 2,500 MW and 4,300 MW of nuclear are expected to be leaving the U.S. power system in 2020 and 2021, respectively.

As more nuclear plants close, EIA projects that net electricity generation from U.S. nuclear power reactors will fall by 17% by 2025.

From 2019-2025 alone, EIA expects U.S. coal capacity to plummet nearly 25% to 176,000 MW, with nuclear falling 15% to 83,000 MW.

In contrast, new combined cycle gas plants will grow capacity almost 30% to around 310,000 MW.

Lower and lower projected commodity prices for gas encourage this immense gas build-out, not to mention non-stop increases in efficiency for gas-based units.

Remember that these are official U.S. Department of Energy estimates, not coming from the industry itself.

In other words, our Department of Energy concludes that gas is the future.

Our hotter and hotter summers are therefore more and more becoming: "summers for natural gas"

Ultimately, this shows why the anti-pipeline movement is so dangerous.

"Affordable Energy Coalition Highlights Ripple Effect of Natural Gas Moratorium."

In April, President Trump signed two executive orders to promote energy infrastructure by directing federal agencies to remove bottlenecks for gas transport into the Northeast in particular, where New England oil-fired generation has spiked, and to streamline federal reviews of border-crossing pipelines and other infrastructure.

Builders, however, are not relying on outside help: all they know is that more U.S. gas demand is a constant, so more infrastructure is mandatory.

They are moving forward diligently: for example, there are now some 27 pipelines worth $33 billion already in the works in Appalachia.

 

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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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