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Organic solar cells that can be painted or printed on surfaces are increasingly efficient, and now show promise for incorporation into applications like clothing that also require them to be flexible.
The Rice University lab of chemical and biomolecular engineer Rafael Verduzco has developed flexible organic photovoltaics that could be useful where constant, low-power generation is sufficient.
The research appears in the American Chemical Society* journal Chemistry of Materials._
Organic solar cells rely on carbon-based materials including polymers, as opposed to hard, inorganic materials like silicon, to capture sunlight and translate it into current. Organics are also thin, lightweight, semitransparent and inexpensive.
While middle-of-the-road, commercial, silicon-based solar cells perform at about 22 percent efficiency, the amount of sunlight converted into electricity, organics top out at around 15 percent.
The field has been obsessed with the efficiency chart for a long time Verduzco said. There's been an increase in efficiency of these devices, but mechanical properties are also really important, and that part's been neglected.
If you stretch or bend things, you get cracks in the active layer and the device fails.

Verduzco said one approach to fixing the brittle problem would be to find polymers or other organic semiconductors that are flexible by nature, but his lab took another tack. Our idea was to stick with the materials that have been carefully developed over 20 years and that we know work, and find a way to improve their mechanical properties he said.
Rather than make a mesh and pour in the semiconducting polymers, the Rice researchers mixed in sulfur-based thiol-ene reagents. The molecules blend with the polymers and then crosslink with each other to provide flexibility.
The process is not without cost, because too little thiol-ene leaves the crystalline polymers prone to cracking under stress, while too much dampens the material's efficiency.
Testing helped the lab find its Goldilocks Zone.
If we replaced 50 percent of the active layer with this mesh, the material would get 50 percent less light and the current would drop Verduzco said. At some point, it's not practical. Even after we confirmed the network was forming, we needed to determine how much thiol-ene we needed to suppress fracture and the maximum we could put in without making it worthless as an electronic device.
At about 20 percent thiol-ene, they found that cells retained their efficiency and gained flexibility.
They're small molecules and don't disrupt the morphology much Verduzco said. We can shine ultraviolet light or apply heat or just wait, and with time the network will form. The chemistry is mild, fast and efficient."

The next step was to stretch the material. Pure P3HT (the active polythiophene-based layer) started cracking at about 6 percent strain Verduzco said.
When we added 10 percent thiol-ene, we could strain it up to 14 percent. At around 16 percent strain we started seeing cracks throughout the material.
At strains higher than 30 percent, the material flexed just fine but became useless as a solar cell. We found there's essentially no loss in our photocurrent up to about 20 percent he said. That seems to be the sweet spot.
Damage under strain affected the material even when the strain was released.
The strain impacts how these crystal domains pack and translates to microscopic breaks in the device Verduzco said. The holes and electrons still need paths to get to the opposite electrodes.
He said the lab expects to try different organic photovoltaic materials while working to make them more stretchable with less additive for larger test cells.
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These innovations see us interacting with smart buildings, lighting our way with photosynthetic lamps, sporting shoes without footprints, and living in tiny cabins made of construction waste. The innovative minds behind all of these sustainable solutions have found unique ways to make the world a little bit better.
Here is our series of Tomorrow you will…

…interact with a smart building
In the German town of Esslingen, near Stuttgart, a new kind of structure is being built. “Milestone” is a 6,500m² office building like no other; its partially mirrored façade does a lot more than just keep out the weather. Milestone is covered in photovoltaics and QR codes that provide information on the town’s history, people and landscape, and within its dedicated smartphone app, you’ll see a kind of pixelated map of the area, with each pixel carrying different information on stories of the city and its inhabitants.

…get light from a plant
The Living Light by Dutch designer Ermj van Oers is an off-grid lamp that harvests its energy through the photosynthetic process of a houseplant. The process is quite simple; the naturally-occurring bacteria, which break down the organic matter produced from photosynthesis, release electrons and protons which flow from the anode compartment to the cathode, producing electricity (okay, it’s a lot simpler than it sounds!).
The lamp is touch-activated through contact with the leaves. The healthier the plant, the more energy you’ll receive back!

…wear clothes made from repurposed CO2
The “shoe without a footprint” is the latest demonstration of making products from pollution. Together with energy firm NRG, New York firm 10xBeta has designed shoes that are made primarily from a custom polymer material that captures CO2 emissions during production. To make the sneaker, the effluent is captured and cooled, and the CO2 in it is separated out.
That substance then becomes the base of a chemical that’s used to create the polymer (or plastic) that forms the shoe’s supportive foam.
The minimal product will probably not make it to the market anytime soon, but it sure opens new perspectives on the aesthetics of environmentally friendly products.

…live in construction waste
UK architecture firm Invisible Studio designed and built this mobile prototype for just £20,000 using a combination of construction waste and locally grown unseasoned timber. Named “Trailer” by its inventors, the 430-square-foot building is made from recycled materials; all of the joinery is from plywood offcuts, including the two staircases, the doors were sourced from a skip, and the building is insulated with scavenged insulation.
The project aims to provide a super low cost, versatile, usable space that could act as a kit of parts for any self builder to improvise around or easily adapt.

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In early February, Chinese workers began assembling a soaring red-and-white transmission tower on the eastern edge of the nation's Anhui province. The men straddled metal tubes as they tightened together latticed sections suspended high above the south bank of the Yangtze River.
The workers were erecting a critical component of the world’s first 1.1-million volt transmission line, at a time when US companies are struggling to build anything above 500,000 volts. Once the government-owned utility, State Grid of China completes the project next year, the line will stretch from the Xinjiang region in the northwest to Anhui in the east, connecting power plants deep in the interior of the country to cities near the coast.
The transmission line will be capable of delivering the output of 12 large power plants over nearly 2,000 miles (3,200 kilometers), sending 50% more electricity 600 miles further than anything that’s ever been built. (Higher-voltage lines can carry electricity over longer distances with lower transmission losses.) As one foreign equipment provider for the project boasts, the line could ship electricity from Beijing to Bangkok, which, as it happens, only hints at State Grid’s rising global ambitions.
The company initially developed and built ultra-high-voltage lines to meet the swelling energy appetites across the sprawling nation, where high mountains and vast distances separate population centers from coal, hydroelectric, wind, and solar resources. But now State Grid is pursuing a far more ambitious goal: to stitch together the electricity systems of neighboring nations into transcontinental “supergrids” capable of swapping energy across borders and oceans.
These massive networks could help slash climate emissions by enabling fluctuating renewable sources like wind and solar to generate a far larger share of the electricity used by these countries. The longer, higher-capacity lines make it possible to balance out the dimming sun in one time zone with, say, wind, hydroelectric, or geothermal energy several zones away.
Politics and bureaucracy have stymied the deployment of such immense, modern power grids in much of the world. In the United States, it can take more than a decade to secure the necessary approvals for the towers, wires, and underground tubes that cut across swaths of federal, national, state, county, and private lands, on the rare occasion when they get approved at all.
A long-distance interconnected transmission grid is a big piece of the climate puzzle says Steven Chu the former US energy secretary, who serves as vice chairman of the nonprofit that State Grid launched in 2016 to promote international grid connections. China is saying ‘We want to be leaders in all these future technologies’ instead of looking in the rear-view mirror like the United States seems to be doing at the moment.
But facilitating the greater use of renewables clearly isn’t China’s only, or even primary, motivation. Transmission infrastructure is a strategic piece of the Belt and Road Initiative, China’s multitrillion-dollar effort to build development projects and trade relationships across dozens of nations. Stretching its ultra-high-voltage wires around the world promises to extend the nation’s swelling economic, technological, and political power.

23,000 miles of wires
State Grid is probably the biggest company you’ve never heard of, with nearly 1 million employees and 1.1 billion customers. Last year, it reported $9.5 billion in profits on $350 billion in revenue, making it the second-largest company on Fortune’s Global 500 list.
State Grid is already the biggest power distributor in Brazil, where it built its first (and still only) overseas ultra-high-voltage line. The company has also snapped up stakes in national transmission companies in Australia, Greece, Italy, the Philippines, and Portugal. Meanwhile, it’s pushing ahead on major projects in Egypt, Ethiopia, Mozambique, and Pakistan and continues to bid for shares in other European utilities.
A lot of Chinese companies are very ambitious in spreading overseas says Simon Nicholas, a co-author of a report tracking these investments by the Institute for Energy Economics and Financial Analysis, a US think tank. “But State Grid is on another level.”
State Grid was created in late 2002, when the government broke up a massive monopoly, the State Power Corporation of China, into 11 smaller power generation and distribution companies. That regulatory unbundling was designed to introduce competition and accelerate development as the nation struggled to meet rising energy demands and halt recurrent blackouts. But State Grid was by far the larger of two resulting transmission companies, and it operates as an effective monopoly across nearly 90% of the nation.
In 2004, the Communist Party handpicked Liu Zhenya the former head of Shandong province’s power bureau, to replace the retiring chief executive of State Grid. Liu, a savvy operator with a talent for navigating party politics, almost immediately began to lobby hard for ultra-high-voltage projects, according to Sinews of Power: The Politics of the State Grid Corporation of China by Xu Yi-Chong, a professor at Griffith University in Australia.
Lines capable of sending more energy over greater distances could stitch together the nation’s fragmented grids, instantly delivering excess electricity from one province to another in need, Liu argued. Later, as China came under growing pressure to clean up pollution and greenhouse-gas emissions, State Grid’s rationale evolved: the power lines became a way to accommodate the growing amount of renewable energy generation.

From the start, critics asserted that State Grid was pushing ultra-high-voltage transmission primarily as a means of consolidating its dominant position, or that the new technology was an expensive and risky way of shoring up rickety energy infrastructure.
But Liu’s arguments won out: early projects were approved and built, and party leaders soon prioritized ultra-high-voltage technology in China’s influential five-year plans.
The company at first collaborated closely with foreign firms developing transmission technology, including Sweden’s ABB and Germany’s Siemens, and it continues to buy some equipment from them. But it quickly assimilated the expertise of its partners and began developing its own technology, including high-voltage transformers as well as lines that can function at very high altitudes and very low temperatures.
State Grid has also developed software that can precisely control the voltage and frequency arriving at destination points throughout the network, enabling the system to react rapidly and automatically to shifting levels of supply and demand.
The company switched on its first million-volt alternating current line in 2009 and the world’s inaugural 800,000-volt direct current line in 2010. State Grid, and by extension China, is now by far the world’s biggest builder of these lines. By the end of 2017, 21 ultra-high-voltage lines had been completed in the country, with four more under construction, Liu said during a presentation at Harvard University in April.
Collectively, they’ll stretch nearly 23,000 miles and be capable of delivering some 150 gigawatts of electricity, roughly the output of 150 nuclear reactors.
At the end of last year, China had poured at least 400 billion yuan ($57 billion) into the projects, according to Bloomberg New Energy Finance. After a slowdown in new project approvals during the last two years, China’s National Energy Administration said in September that it will sign off on 12 new ultra-high-voltage projects by the end of 2019.
The fact of the matter is, the Chinese are the only ones seriously building it at this point says Christopher Clack chief executive of Vibrant Clean Energy and a former researcher with the US National Oceanic and Atmospheric Administration. In a study published in Nature in 2016, Clack found that using high-voltage direct-current lines to integrate the US grid could cut electricity emissions to 80% below 1990 levels within 15 years

Going global
In late February of 2016, Liu walked to the lectern at an energy conference in Houston and announced an audacious plan: using ultra-high-voltage technology to build an energy network that would circle the globe.
By interconnecting transmission infrastructure across oceans and continents, in much the way we've intertwined the internet, the world could tap into vast stores of wind power at the North Pole and solar along the equator, he said. This would clean up global electricity generation, cut energy costs, and even ease international tensions.
Eventually, our world will turn into a peaceful and harmonious global village, a community of common destiny for all mankind with sufficient energy, blue skies, and green land he said.
Of course, such a global grid won’t happen. It would cost more than $50 trillion and require unprecedented, and unrealistic, levels of international trust and cooperation. Moreover, few nations are clamoring for these kinds of high-voltage lines even within their boundaries.
A handful of countries already exchange electricity through standard transmission lines, but efforts to share renewable resources across wide regions have largely gone nowhere. Among the notable failures is the Desertec Industrial Initiative, an effort backed by Siemens and Deutsche Bank a decade ago to power North African, Middle Eastern, and European electricity grids with solar power from the Sahara.
But State Grid’s global grid plan is basically a sales pitch for its long-distance transmission lines, promoting them as a fundamental enabling technology for the clean-energy transition. If all the company ever achieves are the opening moves in the vision of global interconnectivity, and it develops regional grids connecting a handful of nations, it could still make a lot of money.
Notably, at a conference in Beijing the month after Liu’s speech, the company signed a deal with Korea Electric Power, Japan’s Softbank, and Russian power company Rosseti to collaborate on the development of a Northeast Asian “supergrid” connecting those nations and Mongolia.
Softbank boss Masayoshi Son had proposed a version of the supergrid independent of State Grid back in 2011, after the Fukushima nuclear catastrophe underscored the fragility of Japan’s electricity sector.
Kenichi Yuasa a spokesperson for the conglomerate, said feasibility studies completed in 2016 and 2017 showed that grid connections between Mongolia, China, Korea, and Japan, as well as a route between Russia and Japan, are both technically and economically feasible.
We, as a commercial developer, are ready to execute the projects and would like to deliver tangible progress before Tokyo Olympics in 2020 he said in an e-mail.
In a response to inquiries from MIT Technology Review, State Grid disputed the argument that the broader global interconnection plan won't happen, or that its driving motivations are primarily financial and geopolitical.
The great success of UHV technology application in China represents a major innovation of power transmission technology the company said in a statement. "_tate Grid would like to share this kind of technological innovation with the rest of the world, addressing a possible solution to vital concerns for humankind for example, environmental pollution, climate change, and lack of access to electricity supply._

Cleaning up or cleaning up?
In fact, though China has built far more ultra-high-voltage lines than any other country in the world, its own grid is still something of a mess. The country is struggling to efficiently balance its power production and demand, and to distribute electricity where and when it is needed. One result is that it isn’t making full use of its existing renewable-power plants. A recent MIT paper noted that China’s rates of renewable curtailment, the term for when plants are throttled down because of inadequate demand, are the highest in the world and getting higher.
Part of the problem is that it’s easier and more lucrative to use “predictable electrons” from sources like coal or nuclear, which provide a constant stream of electricity, than the variable generation from renewables, says Valerie Karplus, former director of the Tsinghua-MIT China Energy and Climate Project. Mandatory quotas for fossil-fuel plants and provincial politics also distort allocation decisions, she adds.
Less than half of the ultra-high-voltage lines built or planned to date in China are intended to transmit electricity from renewable sources, according to a late-2017 report by Bloomberg New Energy Finance.
Getting the most out of wind, solar, and other intermittent sources will require rethinking how to make grid operations more flexible and responsive Karplus said in an e-mail.
Despite its purported green ambitions, State Grid itself has resisted the broader market reforms that would be necessary to lessen China’s dependence on fossil-fuel plants. All of which raises questions about the company’s commitment to cutting greenhouse-gas emissions, and how much the long-distance lines will really help to clean up power generation elsewhere.
Tellingly, State Grid’s main target markets are in poor countries where fossil-fuel plants dominate and Chinese companies are busy building hundreds of new coal plants. So there’s little reason to expect that any ultra-high-voltage lines built there would primarily carry energy from renewable sources anytime soon.
I haven’t seen anything that would make me think this is part of a green-development initiative says Jonas Nahm who studies China’s energy policy at the Johns Hopkins School of Advanced International Studies. I think State Grid just wants to sell these things anywhere and dominate with its own standards over those developed by Siemens and other companies.
He believes State Grid’s broader ambitions are tied to the Belt and Road Initiative, through which China’s state banks are plowing trillions into infrastructure projects across Asia and Africa in an effort to sell Chinese goods and strengthen the country’s geopolitical influence.
Building, owning, or operating another nation’s critical infrastructure, be it seaports or transmission lines, offers a particularly effective route to exercise soft and sometimes not-so-soft power.
This is really a battle over the developing world Nahm says.
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Stanford electrical engineer Shanhui Fan wants to revolutionize energy-producing rooftop arrays.
Professor Shanhui Fan and postdoctoral scholar Wei Li atop the Packard Electrical Engineering building with the apparatus that is proving the efficacy of a double-layered solar panel.
*The top layer uses the standard semiconductor materials that go into energy-harvesting solar cells, the novel materials on the bottom layer perform the cooling task._
Today, such arrays do one thing, they turn sunlight into electricity. But Fan’s lab has built a device that could have a dual purpose, generating electricity and cooling buildings.
We’ve built the first device that one day could make energy and save energy, in the same place and at the same time, by controlling two very different properties of light said Fan, senior author of an article appearing Nov. 8 in _Joule.*
The sun-facing layer of the device is nothing new. It’s made of the same semiconductor materials that have long adorned rooftops to convert visible light into electricity. The novelty lies in the device’s bottom layer, which is based on materials that can beam heat away from the roof and into space through a process known as radiative cooling.
In radiative cooling, objects, including our own bodies, shed heat by radiating infrared light. That’s the invisible light night-vision goggles detect. Normally this form of cooling doesn’t work well for something like a building because Earth’s atmosphere acts like a thick blanket and traps the majority of the heat near the building rather allowing it to escape, ultimately into the vast coldness of space.

Holes in the blanket
Fan’s cooling technology takes advantage of the fact that this thick atmospheric blanket essentially has holes in it that allow a particular wavelength of infrared light to pass directly into space. In previous work, Fan had developed materials that can convert heat radiating off a building into the particular infrared wavelength that can pass directly through the atmosphere. These materials release heat into space and could save energy that would have been needed to air-condition a building’s interior. That same material is what Fan placed under the standard solar layer in his new device.
Zhen Chen, who led the experiments as a postdoctoral scholar in Fan’s lab, said the researchers built a prototype about the diameter of a pie plate and mounted their device on the rooftop of a Stanford building. Then they compared the temperature of the ambient air on the rooftop with the temperatures of the top and bottom layers of the device. The top layer device was hotter than the rooftop air, which made sense because it was absorbing sunlight. But, as the researchers hoped, the bottom layer of the device was significant cooler than the air on the rooftop.
This shows that heat radiated up from the bottom, through the top layer and into space said Chen, who is now a professor at the Southeast University of China.

What they weren’t able to test is whether the device also produced electricity. The upper layer in this experiment lacked the metal foil, normally found in solar cells, that would have blocked the infrared light from escaping.
The team is now designing solar cells that work without metal liners to couple with the radiative cooling layer.
We think we can build a practical device that does both things Fan said.
Shanhui Fan is the director of the Edward L. Ginzton Laboratory, a professor of electrical engineering, a senior fellow at the Precourt Institute for Energy and a professor, by courtesy, of applied physics. Postdoctoral scholars Wei Li of Stanford and Linxiao Zhu of the University of Michigan, Ann Arbor, also co-authored the paper.
The research was supported by the Stanford University Global Climate and Energy Project, the National Science Foundation and the National Natural Science Foundation of China.
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We need buildings in which to live, but crafting those buildings is making it harder to live on this planet. As much as 10% of global carbon emissions come from the production of concrete.
One ton of CO2 is generated by making one ton of cement, which is made from limestone and a few other things heated to an extremely high temperature.
But what if concrete could generate its own energy? The era of photovoltaic concrete may be getting closer. Photovoltaics, which work by converting light to energy via semiconducting, are starting to migrate from solar panels into the building materials themselves.

In November 2017, Swiss firm LafargeHolcim the world’s largest cement maker, and Heliatek a German solar-panels company, debuted photovoltaic concrete panels at French construction fair Batimat, according to Architizer.
These panels are concrete with built-in ultra-think solar panels that can be delivered as is on site. The companies say that a typical 10-story commercial building covered in 60% of these panels would generate about 30% of its annual energy requirement.
Researchers from ETH Zurich university have also developed their own ultra-thin, sinuous material in which layers of heating coils and solar cells are built into the layers of concrete.

This technology is notoriously complicated. In 2016, Tesla debuted photovoltaic solar-roof tiles that looked better than the regular tiles that sit on the roofs of most American houses. But more than two years later, very few of them have actually been installed, partially due to complications with the manufacture and also reportedly due to the “aesthetic concerns” of Elon Musk.
The company has now promised a large-scale rollout of the tiles in 2019.
Getting photovoltaic concrete ready for actual commercial building work will probably be no easier.
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A regular shop-bought mushroom has been turned into an electricity generator in a process scientists hope will one day be used to power devices.
The “bionic mushroom” was covered with bacteria capable of producing electricity and strands of graphene that collected the current.
Shining a light on the structure activated the bacteria’s ability to photosynthesise, and as the cells harvested this glow they generated a small amount of electricity known as a “photocurrent”.
The fungi supported this process by providing the bacteria with viable surface on which to grow as well as nutrients to stay alive.
The research, published in the journal Nano Letters, is part of a wider effort by scientists to understand how biological machinery can be hijacked and put to good use.

In this case, our system, this bionic mushroom, produces electricity said Professor Manu Mannoor an engineer at Stevens Institute of Technology who led the research.
By integrating cyanobacteria that can produce electricity, with nanoscale materials capable of collecting the current, we were able to better access the unique properties of both, augment them, and create an entirely new functional bionic system.
Professor Mannoor and his team found that bacterial cells lasted several days longer when placed on living mushrooms compared to other bases.
Cyanobacteria are known among bio-engineers for their ability to generate small jolts of electricity, but until now it has been difficult to keep them alive in artificial conditions.
By creating a “hybrid system” that encourages the mushrooms and bacteria to collaborate, the scientists think they have solved this problem.

The systems were created by 3D printing an electronic ink containing strands of graphene, and then following this with a bio-ink containing the bacteria onto the cap of the mushroom.
When light shone was on the mushroom, the bacteria began to photosynthesise and a tiny current of about 65 nanoamps passed into the network of graphene.
While the scientists think an array of these mushrooms would be enough to power something like an LED light, they are still way off powering larger electronic devices.
With this work, we can imagine enormous opportunities for next-generation bio-hybrid applications said Professor Mannoor.
For example, some bacteria can glow, while others sense toxins or produce fuel.
_By seamlessly integrating these microbes with nanomaterials, we could potentially realise many other amazing designer bio-hybrids for the environment, defence, healthcare and many other fields.&
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Researchers have invented a liquid isomer that can store and release solar energy.
The team has solved problems other researchers have previously encountered.
The discovery could lead to more widespread use of solar energy.
In the last year, a team from Chalmers University of Technology, Sweden, essentially figured out how to bottle solar energy.
They developed a liquid fuel containing the compound norbornadiene that, when struck by sunlight, rearranges its carbon, hydrogen, and nitrogen atoms into an energy-storing isomer, quadricyclane. Quadricyclane holds onto the energy, estimated to be up to 250 watt-hours of energy per kilogram, even after it cools and for an extended period of time. For use, it's passed through a cobalt-based catalyst, at which point the energy is released as heat.
The team's research could be a breakthrough in making solar energy transportable and thus even more usable for meeting real-world energy needs.
What's more, the team has been adjusting the molecular makeup of their fuel so that it doesn't break down as a result of storage and release cycles. It can be used over and over again.
We've run it though 125 cycles without any significant degradation according to researcher Kasper Moth-Poulsen.
As a result, the scientists envision a round-trip energy system they call MOST, which stands for Molecular Solar Thermal Energy Storage.

The MOST system
In the MOST system, the liquid runs through a concave solar thermal collector that has a pipe running across its center. The collector focuses sunlight on that pipe, and the fuel running through it, causing the transformation of norbornadiene into quadricyclane. The charged fuel then flows through transparent tubing into storage tanks, or it can be diverted and shipped elsewhere for use. Says Moth-Poulsen in the Chalmers press release, "The energy in this isomer can now be stored for up to 18 years. And when we come to extract the energy and use it, we get a warmth increase which is greater than we dared hope for."
To release the fuel's energy, it's passed through the catalyst in which a chemical reaction occurs to convert the fuel back into liquid whose temperature has been boosted by 63°C or 145°F. So, for example, if the fuel goes into the catalyst at 20°C, it comes out at 83°C. In this form, the fluid can be used for heating a home or business, or be used in any other system reliant on heated liquid.
You could use that thermal energy for your water heater, your dishwasher or your clothes dryer MIT's Jeffrey Grossman tells NBC MACH.
There could be lots of industrial applications as well.

This last year has been a key time
The first iteration of the Chalmers fuel was revealed about a year ago, and in the intervening months, the researchers have been working toward the robust behavior they're now seeing, even beyond achieving that remarkable 18-year storage potential. "We have made many crucial advances recently, and today we have an emissions-free energy system which works all year around," says Moth-Poulsen.
Though other researchers have experimented with similar uses for norbornadiene, their fuels broke down after just a few cycles before their research was abandoned. Those earlier fuels also didn't hold the energy very long.
The Chalmers team also originally had to mix their isomer with flammable toluene. Now, however, they've worked out a way to use the isomer without dangerous additives.

Storing solar energy
As the world moves to renewable energy, solar energy has proven to be among the most attractive: Sunlight is free and releasing its energy produces no pollution or harmful effects. One remaining limiting factor has been finding ways of storing solar energy that are as clean as solar energy itself.
Much work is being down with batteries, but it's difficult to produce power cells without using toxic materials. The MOST system offers an exciting new angle to pursue.
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The warning from the world's top climate scientists that carbon dioxide (CO2) will need to be removed from the atmosphere to limit global warming to 1.5 degrees Celsius is both a due and dire recognition of the great task in front of us. What must not be forgotten, however, is the hope that our forests provide.
The Intergovernmental Panel on Climate Change (IPCC) has said limiting global warming to 1.5C is not only achievable but also critical, given the previously underestimated accelerating risks for every degree of warming beyond that target.
It has also suggested that the amount of carbon dioxide removal (CDR) that will be needed can be limited by significant and rapid cuts in emissions, but also reduced energy and land demand to a few hundred gigatonnes without relying on Bioenergy with Carbon Capture and Storage (BECCS).

This means forests and land use can and must play a key role in efforts to achieve 1.5 degrees, but governments and industry too often overlook why improved forest protection, as well as forest restoration, are crucial alternative solutions to risky CDR technologies such as BECCS.
While greenhouse gas emissions from agriculture and the destruction of forests and peatlands contribute heavily to climate change, the growth and restoration of forests can contribute significantly to reducing the concentration of CO2 in the atmosphere.
Recent research suggests that forest protection and restoration, together with other "natural climate solutions", can provide over one-third of the climate mitigation needed between now and 2030.
The IPCC has estimated that between 100 and 1,000 gigatonnes of CO2 will need to be removed from the atmosphere to meet the Paris goals. It has been broadly agreed that the most important natural "carbon sinks" are the world's forests. To limit climate change, we must urgently adopt an holistic approach to forest and peatland protection.
This means deforestation must be halted and our remaining forests well protected, intact forests must be kept away from logging and other destructive activities, the management of used forests must change and where land is available, it must be restored with natural forests.
To allow these natural climate solutions to thrive, wildland fires, most of which are sparked by human activities and contribute to global warming, must also be reduced. The tragic and wide geographic spread of wildfires across Siberia, Europe and California during the northern hemisphere summer is a stark reminder of the threat climate change poses to our forests.

Our forests are our only natural and tested "technology" to lessen the impacts of climate change and protecting them will bring benefits that untried carbon removal technical solutions do not.
Forest protection will help communities adapt to climate change and support their livelihoods. Fires, droughts, floods, storms and their impacts can also be reduced, biodiversity protected, freshwater-cycles maintained and soil erosion prevented.
By accepting that our lands and forests are primarily needed to feed people, protect nature and protect the climate, rather than as resources for profit, areas for industrial agriculture, livestock or coal mining for example in Germany's Hambach Forest, we can turn the tide against global warming.
The IPCC report identifies different pathways to limiting global warming to 1.5C, most of which are dependent to varying degrees on the deployment, future availability and success of more technological, but so far unproven, approaches to CDR, and, in particular, BECCS.
Deployment of BECCS would involve massive upscaling in intensive production of monoculture crops or tree plantations, leading to increased loss of natural habitats and biodiversity, threatening indigenous peoples, small farmers and local communities, squeezing land needed for food production and increasing water demand and agrochemical pollution.
Bioenergy without carbon capture and storage is contributing to, rather than helping mitigate, climate change and there exists great uncertainty around the technical feasibility, safety, sustainability and cost of long-term geological carbon storage.

This is why we need to act on the IPCC report and re-appraise the way we view our forests. One-third of the global forest area has already been cleared for arable land, grassland, settlements and roads in the last millennium.
We can halt and reverse this trend by ending the expansion of agricultural crops, particularly for bio-energy and animal feed, into natural ecosystems. We must also embark on a dramatic change to our agricultural practices, embracing ecological agriculture and shifting to a diet less reliant on meat to reduce emissions from livestock.
What is required is bold action from governments and industry to commit to forest protection and restoration while upholding the rights of indigenous people. By seizing the opportunity now to restore deforested areas and opt against false solutions such as BECCS, we can ensure our forests fulfil their critical role.
Home to millions of people, our forests offer us a path towards climate mitigation, but we have no time to waste.
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A closer look at materials that make up conventional solar cells reveals a nearly rigid arrangement of atoms with little movement. But in hybrid perovskites, a promising class of solar cell materials, the arrangements are more flexible and atoms dance wildly around, an effect that impacts the performance of the solar cells but has been difficult to measure.
In a paper published in the Proceedings of the National Academy of Sciences, an international team of researchers led by the U.S. Department of Energy's SLAC National Accelerator Laboratory has developed a new understanding of those wild dances and how they affect the functioning of perovskite materials.
The results could explain why perovskite solar cells are so efficient and aid the quest to design hot-carrier solar cells, a theorized technology that would almost double the efficiency limits of conventional solar cells by converting more sunlight into usable electrical energy.

Piece of the puzzle
Perovskite solar cells, which can be produced at room temperature, offer a less expensive and potentially better performing alternative to conventional solar cell materials like silicon, which have to be manufactured at extremely high temperatures to eliminate defects. But a lack of understanding about what makes perovskite materials so efficient at converting sunlight into electricity has been a major hurdle to producing even higher efficiency perovskite solar cells.
It's really only been over the last five or six years that people have developed this intense interest in solar perovskite materials says Mike Toney a distinguished staff scientist at SLAC's Stanford Synchrotron Radiation Light Source (SSRL) who led the study.
As a consequence, a lot of the foundational knowledge about what makes the materials work is missing. In this research, we provided an important piece of this puzzle by showing what sets them apart from more conventional solar cell materials. This provides us with scientific underpinnings that will allow us to start engineering these materials in a rational way.

Keeping it hot
When sunlight hits a solar cell, some of the energy can be used to kick electrons in the material up to higher energy states. These higher-energy electrons are funneled out of the material, producing electricity.
But before this happens, a majority of the sun's energy is lost to heat with some fraction also lost during the extraction of usable energy or due to inefficient light collection. In many conventional solar cells, such as those made with silicon, acoustic phonons, a sort of sound wave that propagates through material – are the primary way that this heat is carried through the material. The energy lost by the electron as heat limits the efficiency of the solar cell.
In this study, theorists from the United Kingdom, led by Imperial College Professor Aron Walsh and electronic structure theorists Jonathan Skelton and Jarvist Frost, provided a theoretical framework for interpreting the experimental results. They predicted that acoustic phonons traveling through perovskites would have short lifetimes as a result of the flexible arrangements of dancing atoms and molecules in the material.
Stanford chemists Hema Karunadasa and Ian Smith were able to grow the large, specialized single crystals that were essential for this work. With the help of Peter Gehring, a physicist at the NIST Center for Neutron Research, the team scattered neutrons off these perovskite single crystals in a way that allowed them to retrace the motion of the atoms and molecules within the material. This allowed them to precisely measure the lifetime of the acoustic phonons.
The research team found that in perovskites, acoustic phonons are incredibly short-lived, surviving for only 10 to 20 trillionths of a second. Without these phonons trucking heat through the material, the electrons might stay hot and hold onto their energy as they're pulled out of the material. Harnessing this effect could potentially lead to hot-carrier solar cells with efficiencies that are nearly twice as high as conventional solar cells.
In addition, this phenomenon could explain how perovskite solar cells work so well despite the material being riddled with defects that would trap electrons and dampen performance in other materials.
Since phonons in perovskites don't travel very far, they end up heating the area surrounding the electrons, which might provide the boost the electrons need to escape the traps and continue on their merry way Toney says.

Transforming energy production
To follow up on this study, researchers at the Center for Hybrid Organic-Inorganic Semiconductors for Energy (CHOISE) Energy Frontier Research Center led by DOE's National Renewable Energy Laboratory will investigate this phenomenon in more complicated perovskite materials that are shown to be more efficient in energy devices. They would like to figure out how changing the chemical make-up of the material affects acoustic phonon lifetimes.
We need to fundamentally transform our energy system as quickly as possible says Aryeh Gold-Parker who co-led the study as a Ph.D. student at Stanford University and SLAC.
As we move toward a low-carbon future, a very important piece is having cheap and efficient solar cells. The hope in perovskites is that they'll lead to commercial solar panels that are more efficient and cheaper than the ones on the market today.
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Researchers at Kanazawa University report in the journal Organic Electronics documents a new method for controlling the orientation of conducting molecules in organic solar cells that results in the enhanced light adsorption and performance of the cells.
Solar cells are a cost-effective, alternate source of energy. A subtype of these, organic solar cells make use of organic polymers inside the cell. Using these polymers makes the cells light-weight and increases their flexibility.
Organic solar cells are produced by two different chemical methods: dry processing and wet processing, with the latter being a faster method. There are several parameters used to assess the efficiency of solar cells with absorption of light and transportation of charge being widely used.
A prevailing problem with the structure of organic cells is that molecules in the active organic layer responsible for light absorption and charge transport tend to face both towards the edges of cells, as well as towards the light absorbing substrate. Maximizing the number of molecules facing the substrate, however, is the key to maximising absorption and conductivity of the cell.
Scientists have modified the dry processing method to achieve such an orientation, but it has not been possible with the wet method. The research team led by Tetsuya Taima at Kanazawa University, is the first to successfully do so.

The premise of their method is the introduction of a copper iodide (CuI) layer between the active molecules and the substrate. In their study, the researchers used a film of active molecules called DRCN5T and coated them onto either CuI/PEDOT: PSS (30 nm)/indium tin oxide (ITO) mixed substrates, or substrates without the CuI layer. The ratio of substrate facing to edge facing DRCN5T molecules was then compared between both. Subsequent high-resolution imaging revealed that the CuI containing cells had active molecules with a ten times higher substrate facing orientation, along with enhanced light absorption. The researchers attributed this altered orientation of the molecules to strong chemical interactions between the DRCN5T and CuI atoms. To further confirm this, DRCN5T molecules with bulky side chains that do not interact with CuI were used, and a higher substrate facing ratio was not seen.
This is the first study that effectively demonstrates a method of producing such efficient organic solar cells using the wet processing method. Besides saving time, the wet method also results in larger film areas.
This technique is expected to greatly contribute to the development of organic thin film solar cells fabricated by wet processing in the future conclude the authors. Their approach paves the way for producing high-performance solar cells faster.

Solar cells: Also known as photovoltaic (light creating voltage) cells, these devices convert light energy into electrical energy. The working principle of a photovoltaic cell consists of three steps. The absorption of light (sunlight or artificial light), results in the formation of electron-holes (exitons) pairs. These pairs are then separated, and electrons are carried through an active conducting layer, into electrodes, resulting in the creation of a charge. This phenomenon is also known as the photoelectric effect.
In traditional solar cells, the conducting material is silicon. Organic photovoltaic cells usually have organic polymers in place of silicon. Solar cells connected in parallel, make up solar panels.
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