New Developments September 2017

Is this a good time to talk about climate change? Experiencing extreme weather events can make people modestly more likely to support policy measures to help communities adapt to climate change. The effect on people’s attitudes is not only small but only lasts about a month. But the world measured in the study may no longer be the one we are living in. The researchers only looked at how the frequency of extreme weather affects attitudes, not the severity. Yet the most extreme weather events may affect people’s psychology over a longer period.

A Washable, Stretchable Solar Cell For Clothes and Awnings Engineers have made a new solar cell that works well even after being washed. The stretchable, water-resistant cells could be used to make clothes that can power wearable devices and sensors. They could also lead to power-generating awnings, shades, and tents. Thin, flexible solar cells made of organic polymers are less efficient, but are easy and cheap to manufacture. This has made them attractive for large-area, flexible devices, especially as scientists have in recent years improved their efficiency and longevity; organic solar cells can degrade when exposed to water and oxygen. They went from efficiencies of 2 percent in 2007 to over 8 percent in 2016.

“Keeping warming to 1.5 degrees just went from impossible to very difficult” Previous carbon budget calculations have underestimated the amount of carbon dioxide emitted due to human activities so far. This set up slight – but significant – discrepancies between computer climate models and temperatures in the real world. Emissions will have to decline in a straight line to 0 over the next 40 years. Or, if we can’t cut emissions that fast, we’ll have to employ carbon capture technologies to achieve negative emissions during the later portion of that period. However, current promises that nations have made under the Paris Agreement won’t be sufficient to limit warming to 1.5° C – a well-known gap, at least among climate scientists. The new calculations suggest that nations would have to make their 2030 emissions targets about 10% lower than they currently are (and then continue to cut emissions sharply after that) in order to hit the 1.5° C mark.

Americans may finally be ready to look at a carbon tax While policymakers in the US have generally looked at taxing carbon emissions warily because it carries political risk, the idea has recently gained backing among Republican policymakers. In February, an international research group called the Climate Leadership Council–founders of which include senior conservative leaders and corporate giants like BP, Shell, and ExxonMobil– released a report emphasizing how a carbon tax is more consistent with conservative principles of free-market solutions and small government. The group’s carbon dividends idea is to initially charge $40 per ton of carbon dioxide produced, resulting in about $200 billion per year. This amount would go up over time. The revenue would be paid out in tax-free dividends to US families, boiling down to about $2000 annually for a family of four. The vast majority of 80 percent supported developing clean energy like wind and solar, and improving roads, bridges and other infrastructure. More than 70 percent supported using the money to help displaced coal industry workers, and 66 percent support paying down the national debt. Between 45–60 percent support reducing federal income taxes, assisting low-income communities vulnerable to climate change; paying a climate dividend to all households in equal amounts; and helping all communities prepare for and adapt to global warming. Higher average household income increased the likelihood of supporting a carbon tax.

Scientists can calculate how much climate change individual oil companies are responsible for Roughly one-quarter of global warming can be traced to carbon emissions from less than two-dozen companies, according to research published last week in Climatic Change. It builds on a 2014 study that traced nearly two-thirds of all industrial carbon dioxide emissions between 1880 and 2010 to just 90 companies, including 83 fossil fuel producers and 7 cement manufacturers. Their calculations also suggest that the top 90 carbon producers are responsible for nearly half of the increase in global average temperature and between one-quarter and one-third of sea level rise over that period. Looking forward, recent emissions from the 90 largest carbon producers will drive nearly two-thirds of the additional sea level rise expected by 2040, they found. Just three companies – Chevron, ExxonMobil, and BP – are responsible for nearly 6% of sea level rise. “Strikingly, more than half of all emissions traced to carbon producers over the 1880-2010 period were produced since 1986,” the researchers write.

China just built a 250-acre solar farm shaped like a giant panda A new solar power plant in Datong, China, however, decided to have a little fun with its design. China Merchants New Energy Group, one of the country's largest clean energy operators, built a 248-acre solar farm in the shape of a giant panda. The first phase, which includes one 50-megawatt plant, was completed on June 30. A second panda is planned for later this year. Called the Panda Power Plant, it will be able to produce 3.2 billion kilowatt-hours of solar energy in 25 years, according to the company. That will eliminate approximately million tons of coal that would have been used to produce electricity, reducing carbon emissions by 2.74 million tons.

How safe are critical infrastructures from hacker attacks? As wind turbines are often scattered across large areas, they cannot be entirely controlled via cables. "Mobile telephony networks have to be used for the last mile of the control," says David Rupprecht, PhD student and participant in the Bercom project. Reliable monitoring of such facilities is important to, for example, maintain control over the generated energy volumes. If they are higher than the consumed energy volumes, the power grid overloads and an outage may occur. Attackers can interfere with the system by authorising surplus electricity production while overriding the system's safety measures. The result: None of the ten tested mobile phones alerted its user to an unencrypted data exchange. When it came to authentication, on the other hand, only one phone failed the test; the other nine identified fake messages and did not authorise their reception.

Firebricks offer low-cost storage for carbon-free energy Firebricks, designed to withstand high heat, have been part of our technological arsenal for at least three millennia, since the era of the Hittites. The researchers' idea is to make use of excess electricity produced when demand is low -- for example, from wind farms when strong winds are blowing at night -- by using electric resistance heaters, which convert electricity into heat. These devices would use the excess electricity to heat up a large mass of firebricks, which can retain the heat for long periods if they are enclosed in an insulated casing. At a later time, the heat could be used directly for industrial processes, or it could feed generators that convert it back to electricity when the power is needed. The demand for industrial heat in the U.S. and most industrialized regions is actually larger than the total demand for electricity. And unlike the demand for electricity, which varies greatly and often unpredictably, the demand for industrial heat is constant and can make use of an extra heat source whenever it's available, providing an almost limitless market for the heat provided by this firebrick-based system.

Electricity prices are determined a day in advance, with a separate price for each one-hour segment of the day. This is done through an auction system between the producers and the distributors of power. Distributors determine how much power they expect to need during each hour, and suppliers bid based on their expected costs for producing that power. Depending on the needs at a given time, these prices can be low, if only baseload natural gas plants are needed, for example, or they can be much higher if the demand requires use of much more expensive "peaking" power plants. At the end of each auction, the distributors figure out how many of the bids will be needed to meet the projected demand, and the price to be paid to all of the suppliers is then determined by the highest-priced bid of all those accepted for that hour. But that system can lead to odd outcomes when power that is very cheap to produce -- solar, wind and nuclear power, whose actual operating costs are vanishingly small -- can supply enough to meet the demand. Then, the price the suppliers get for the power can be close to zero, rendering the plants uneconomical.

Coatings needed for concentrating solar power Next-generation concentrating solar power (CSP) plants require high-temperature fluids, like molten salts, in the range of 550-750 degrees Celsius to store heat and generate electricity. At those high temperatures, however, the molten salts eat away at common alloys used in the heat exchangers, piping, and storage vessels of CSP systems. New research at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) is aimed at mitigating corrosion levels in CSP plants with nickel-based coatings. To commercially use molten salt mixtures containing sodium chloride, potassium chloride, and magnesium chloride, the corrosion rate in the storage tanks must be slow -- less than 20 micrometers per year -- so that a concentrating solar power plant can achieve a 30-year life. Bare stainless steel alloys tested in a molten chloride corroded as fast as 4,500 micrometers per year. Gomez-Vidal applied different types of nickel-based coatings, which are commonly used for reducing oxidation and corrosion, to stainless steel. One such coating, with the chemical formula NiCoCrAlYTa, showed the best performance so far. It limited the corrosion rate to 190 micrometers per year -- not yet at the goal but a large improvement compared to the uncoated steel by a 96% reduction in the corrosion rate.

Advanced lithium-ion and metal-air batteries Yang's group developed a battery cathode created from a thin-film alloy of nickel sulfide and iron sulfide. That combination of materials brings big advantages to their new electrode. On their own, nickel sulfide and iron sulfide each display good conductivity. Conductivity is even better when they're combined, researchers found. They were able to boost conductivity even more by making the cathode from a thin film of nickel sulfide-iron sulfide, then etching it to create a porous surface of microscopic nanostructures. These nanopores, or holey structures, greatly expand the surface area available for chemical reaction. Quality lithium-based batteries can be drained and recharged about 300 to 500 times before they begin to lose capacity. Tests show a battery with the nickel sulfide-iron sulfide cathode could be depleted and recharged more than 5,000 times before degrading. Metal-air batteries, fuel cells and other energy storage and conversion applications rely on chemical reactions to produce current. In turn, those reactions need an efficient catalyst to help them along. Precious metals including platinum, palladium and iridium have proven to be efficient catalysts, but their high cost and poor stability and durability make them impractical for large-scale commercialization. Researchers in Yang's group led by Wenhan Niu, Zhao Li and Kyle Marcus developed a new process for creating a catalyst with a substrate of graphene, a highly conductive two-dimensional material with the thickness of a single atom. The electrocatalyst is safer and more stable than the volatile compounds found in lithium batteries, and can function in rain, extreme temperatures and other harsh conditions. And without the need for precious metals, it can be manufactured more cheaply.

Realistic projections of economic growth and carbon emissions Between 2008 and 2015, the United States was able to reduce carbon emissions while enjoying limited economic growth. But in a recent commentary, John Deutch, who has worked with the energy departments of several presidential administrations, urges cautious optimism. He explains the country experienced a short-term decoupling of emissions and economic growth that models suggest won't sustain in the future or be enough to prevent climate change. Planned reductions in energy use and carbon intensity are welcome and likely irreversible, but the reductions as currently planned will not be enough to avoid the oncoming impact of climate change. Some of the remaining options are for policies to change, for technology to rapidly improve so energy is used more efficiently to power a country's economic activity, or for investment in how the world can adapt to climate change.

Defects in next-generation solar cells can be healed with light the team made a perovskite-based device, printed using techniques compatible with scalable roll-to-roll processes, but before the device was completed, they exposed it to light, oxygen and humidity. Perovskites often start to degrade when exposed to humidity, but the team found that when humidity levels were between 40 and 50 percent, and the exposure was limited to 30 minutes, degradation did not occur. Once the exposure was complete, the remaining layers were deposited to finish the device. When the light was applied, electrons bound with oxygen, forming a superoxide that could very effectively bind to electron traps and prevent these traps from hindering electrons. In the accompanying presence of water, the perovskite surface also gets converted to a protective shell. The shell coating removes traps from the surfaces but also locks in the superoxide, meaning that the performance improvements in the perovskites are now long-lived. "We've seen an increase in luminescence efficiency from one percent to 89 percent, and we think we could get it all the way to 100 percent, which means we could have no voltage loss -- but there's still a lot of work to be done."

Solar-to-fuel system recycles CO2 to make ethanol and ethylene Scientists have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant advance in the effort to move toward sustainable sources of fuel. The researchers did this by optimizing each component of a photovoltaic-electrochemical system to reduce voltage loss, and creating new materials when existing ones did not suffice. Among the new components developed by the researchers are a copper-silver nanocoral cathode, which reduces the carbon dioxide to hydrocarbons and oxygenates, and an iridium oxide nanotube anode, which oxidizes the water and creates oxygen. Because carbon dioxide is a stubbornly stable molecule, breaking it up typically involves a significant input of energy. "Reducing CO2 to a hydrocarbon end product like ethanol or ethylene can take up to 5 volts, start to finish," said study lead author Gurudayal, postdoctoral fellow at Berkeley Lab. "Our system reduced that by half while maintaining the selectivity of products."

Energy harvested from evaporation could power much of US In the first evaluation of evaporation as a renewable energy source, researchers find that US lakes and reservoirs could generate 325 gigawatts of power, nearly 70 percent of what the United States currently produces. Though still limited to experiments in the lab, evaporation-harvested power could in principle be made on demand, day or night, overcoming the intermittency problems plaguing solar and wind energy. One machine developed in his lab, the so-called Evaporation Engine, controls humidity with a shutter that opens and closes, prompting bacterial spores to expand and contract. The spores' contractions are transferred to a generator that makes electricity. Researchers estimate that half of the water that evaporates naturally from lakes and reservoirs into the atmosphere could be saved during the energy-harvesting process. In their model, that came to 25 trillion gallons a year, or about a fifth of the water Americans consume.

Wearable solar thermoelectric generator created Engineers have introduced a new advanced energy harvesting system, capable of generating electricity by simply being attached to clothes, windows, and outer walls of a building. This new device is based on a temperature difference between the hot and cold sides. The temperature difference can be increased as high as 20.9 °C, which is much higher than the typical temperature differences of 1.5 to 4.1 °C of wearable thermoelectric generators driven by body heat. The research team expects that their wearable solar thermoelectric generator proposes a promising way to further improve the efficiency by raising the temperature difference. A thermoelectric generator (TEGs) refers to a device that converts waste heat energy, such as solar energy, geothermal energy, and body heat into additional electrical power. A wearable solar thermoelectric generator has an open-circuit voltage of 55.15 mV and an output power of 4.44 μW when exposed to sunlight.

Fully renewable India in 2050 can take a shortcut to emission-free future The suggested renewable energy system works mainly on solar energy and batteries. Solar photovoltaics is the most economical electricity source and batteries satisfy the night-time electricity demand. In addition to covering India's electricity demand for power, the system simulation also covers for seawater desalination and synthetic natural gas in three decades. The monsoon period in India is the only time of the year when solar power is reduced. In the renewable system the lack of solar power would be compensated with increased wind and hydro resources as well as solar power from less monsoon affected neighbouring regions via power lines. The proposed system is cheaper than India's current system, which runs primarily on coal. The cost of electricity in the renewable system would be 3640 Indian rupees (52 euros) per megawatt-hour (MWh) in 2050 when only the power sector is taken into account. When the demand for seawater desalination and industrial gas sectors are taken into account, the cost is 3220 Indian rupees (46 euros) per MWh. In comparison, the cost of the current system is 57 euros per MWh. The total investment needed would be around 3380 billion euros.

A sustainable future powered by sea This project uses submerged turbines anchored to the sea floor through mooring cables that convert the kinetic energy of sustained natural currents in the Kuroshio into usable electricity, which is then delivered by cables to the land. "Surprisingly, 30% of the seashore in mainland Japan is covered with tetrapods and wave breakers." Replacing these with "intelligent" tetrapods and wave breakers, Shintake explains, with turbines attached to or near them, would both generate energy as well as help to protect the coasts. "Using just 1% of the seashore of mainland Japan can [generate] about 10 gigawats [of energy], which is equivalent to 10 nuclear power plants," Professor Shintake explains. "That's huge." They are also built to be safe for surrounding marine life -- the blades rotate at a carefully calculated speed that allows creatures caught among them to escape.

Astonishing time limit for ultrafast perovskite solar cells set Researchers have quantified the astonishingly high speeds at which future solar cells would have to operate in order to stretch what are presently seen as natural limits on their energy conversion efficiency. The study, which investigated photovoltaic devices based on a type of materials called perovskites, suggests that these could achieve unprecedented levels of super-efficiency. But to do so, they will need to turn sunlight into electrons and then extract these as electrical charge within just quadrillionths of a second -- a few "femtoseconds," to give them their scientific name. The amount of electrical energy that can be extracted from a hot carrier cell, relative to the amount of light absorbed, could potentially match or even break an energy efficiency rate of 30%. In rough terms, this is the maximum energy efficiency that solar cells can conceivably achieve -- although standard silicon cells typically have efficiencies closer to 20% in practice. While silicon cells are about a millimetre thick, perovskite equivalents have a thickness of approximately one micrometre, about 100 times thinner than a human hair. They are also very flexible, meaning that in addition to being used to power buildings and machines, perovskite cells could eventually be incorporated into things like tents, or even clothing. For a brief moment after they are created, the electrons are moving very quickly. However, they then start to collide, and lose energy. Electrons which retain their speed, prior to collision, are known as "hot" and their added kinetic energy means that they have the potential to produce more charge. The study found that electron collision events started to happen between 10 and 100 femtoseconds after light was initially absorbed by the cell. To maximise energy efficiency, the electrons would thus need to reach the electrode in as little as 10 quadrillionths of a second.

Small scale energy harvesters show large scale impact The production of nano-scale devices has drastically increased with the rise in technological applications, yet a major drawback to the functionality of nano-sized systems is the need for an equally small energy resource. To address this, researchers have been modeling new piezoelectric energy harvester technology at the nano-scale level. The research team studied nonlinear vibrations and voltage based on nonlocal elasticity theory, which states that a point stress is dependent on the strain in a region around that point. Using this theory, they could derive nonlinear equations of motion with straightforward solutions. Their results showed that adding a nanobeam tip mass and increasing the scale factor would increase the generated voltage and vibration amplitude, hence increasing energy output. Modeling micro- and nano-scaled piezoelectric energy harvesters (PEHs) was also able to reveal just what impact size effects had on the output they could expect. The researchers found that the error of neglecting size is significant when comparing macro and micro PEHs. Neglecting various size effects resulted in lower estimations of PEH vibrations.

Sensible driving saves more gas than drivers think A new study has quantified the impact speeding and slamming on the brakes has on fuel economy and consumption. Aggressive behavior behind the wheel can lower gas mileage in light-duty vehicles, which can equate to losing about $0.25 to $1 per gallon.

Step towards better 'beyond lithium' batteries One approach to develop batteries that store more energy is to use "multivalent" metals instead of lithium. In lithium-ion batteries, charging and discharging transfers lithium ions inside the battery. For every lithium ion transferred, one electron is also transferred, producing electric current. In multivalent batteries, lithium would be replaced by a different metal that transfers more than one electron per ion. For batteries of equal size, this would give multivalent batteries better energy storage capacity and performance. The team showed that titanium dioxide can be modified to allow it to be used as an electrode in multivalent batteries, providing a valuable proof of concept in their development. The scientists deliberately introduced defects in titanium dioxide to form high concentrations of microscopic holes, and showed these can be reversibly occupied by magnesium and aluminium; which carry more than one electron per ion.

A solar cell you can put in the wash Scientists from RIKEN and the University of Tokyo have developed a new type of ultra-thin photovoltaic device, coated on both sides with stretchable and waterproof films, which can continue to provide electricity from sunlight even after being soaked in water or being stretched and compressed. The work could lead to sensors that record heartbeats and body temperature, for example, providing early warning of medical problems. In the past, attempts have been made to create photovoltaics that could be incorporated into textiles, but typically they lacked at least one of the important properties -- long-term stability in both air and water, energy efficiency, and robustness including resistance to deformation -- that are key to successful devices. For the present work, the members of the research group developed extremely thin and flexible organic photovoltaic cells, based on a material called PNTz4T, which they had developed in earlier work. They deposited the device in an inverse architecture, which they had previously developed, onto a 1-um-thick parylene film. The ultra-thin device was then placed onto acrylic-based elastomer and the top side of the device was coated with an identical elastomer, giving it a coating on both sides to prevent water infiltration. The elastomer, while allowing light to enter, prevented water and air from leaking into the cells, making them more long-lasting than previous experiments. The researchers then subjected the device to a variety of tests, finding first that it had a strong energy efficiency of 7.9 percent, producing a current of 7.86 milliwatts per square centimeter, as the current density was 13.8 milliamperes per square centimeter at 0.57 volts, based on a simulated sunlight of 100 milliwatts per square centimeter. To test the durability, they subjected it to compression, and found that after compressing by nearly half for twenty cycles while placing drops of water on it, it still had 80 percent of the original efficiency.

Developing roads that can generate power from passing traffic Engineers are working on smart materials such as 'piezolectric' ceramics that when embedded in road surfaces would be able to harvest and convert vehicle vibration into electrical energy. It currently costs around 15p a kilowatt hour to power a street lamp. Therefore 2,000 to 4,000 lights can cost operators -- which in the UK tend to be local authorities, or the Highways Agency for motorways and trunk roads -- approximately between £1,800 and £3,600 per day. Researchers say the cost of installing and operating new road energy harvesting technology would be around 20 per cent of this cost.

Engineers develop tools to share power from renewable energy sources during outages A team of engineers has developed algorithms that would allow homes to use and share power from their renewable energy sources during outages by strategically disconnecting these devices, called solar inverters, from the grid. The algorithms work with existing technology and would improve systems' reliability by 25 to 35 percent. If you think you can use the solar panels on your roof to power your home during an outage, think again. During an outage, while your home remains connected to the grid, the devices that manage your solar panels are powered down for safety reasons. In other words, this permanent connection to the grid makes it impossible for homeowners to draw on power generated by their own renewable energy resources. The innovation here is the algorithm's capability to prioritize distribution of power from renewable resources during an outage. The equations take into account forecasts for solar and wind power generation as well as how much energy storage is available, including electric vehicles, batteries and so on. The algorithm combines that information with the amount of energy that the residents are projected to use as well as the amount of energy that a cluster of homes can generate. The algorithm could also be programmed to include a priority function, based on different parameters. For example, customers who are willing to pay more could get priority to get power during an outage. Or customers who generate more energy than they produce during normal operations would not lose power during an outage. More importantly, the algorithm could give priority to customers who are in urgent need of power, because they use life support equipment, for example. The algorithms work with existing technology but they require each home to be equipped with circuit breakers that can be remotely controlled -- and these devices are not yet widespread. Utilities also would have to install advanced communications methods that allow the power systems in a residential cluster to talk to one another.

Advanced material developed for ultra-stable, high capacity rechargeable batteries With the growing demand of these battery systems, researchers are turning to more sustainable, environmentally friendly methods of producing them. One such method is to use organic materials as an electrode in the rechargeable battery. Organic electrodes leave lower environment footprints during production and disposal which offers a more eco-friendly alternative to inorganic metal oxide electrodes commonly used in rechargeable batteries. The structures of organic electrodes can also be engineered to support high energy storage capabilities. The challenge, however, is the poor electrical conductivity and stability of organic compounds when used in batteries. Organic materials currently used as electrodes in rechargeable batteries -- such as conductive polymers and organosulfer compounds -- also face rapid loss in energy after multiple charges. To overcome these limitations, Prof Loh and his research team synthesised a novel organic compound 3Q (π-conjugated quinoxaline-based heteroaromatic molecule) that has up to six charge storage sites per molecule in an effort to enhance its conductivity and energy retention.

Supercharging silicon batteries Looking for better materials, silicon offers great advantages over carbon graphite for lithium batteries in terms of capacity. Six atoms of carbon are required to bind a single atom of lithium, but an atom of silicon can bind four atoms of lithium at the same time, multiplying the battery capacity by more than 10-fold. However, being able to capture that many lithium ions means that the volume of the anode swells by 300% to 400%, leading to fracturing and loss of structural integrity. To overcome this issue, OIST researchers have now reported in Advanced Science the design of an anode built on nanostructured layers of silicon -- not unlike a multi-layered cake -- to preserve the advantages of silicon while preventing physical collapse. Layers of unstructured silicon films are deposited alternatively with tantalum metal nanoparticle scaffolds, resulting in the silicon being sandwiched in a tantalum frame.

Newly-discovered semiconductor dynamics may help improve energy efficiency The most common material for semiconductors is silicon, which is mined from Earth and then refined and purified. But pure silicon doesn't conduct electricity, so the material is purposely and precisely adulterated by the addition of other substances known as dopants. Boron and phosphorus ions are common dopants added to silicon-based semiconductors that allow them to conduct electricity. But the amount of dopant added to a semiconductor matters -- too little dopant and the semiconductor won't be able to conduct electricity. Too much dopant and the semiconductor becomes more like a non-conductive insulator. The scientists were able to capture X-ray images of what happens at the atomic level inside a semiconductor. They used tiny chips of cadmium sulfide for their semiconductor "base" and doped them with copper ions. Instead of wiring the tiny chips for electricity, they generated a flow of electrons through the semiconductors by shooting them with a powerful blue laser beam.

Cooling system works without electricity Radiative sky cooling is a natural process that everyone and everything does, resulting from the moments of molecules releasing heat. You can witness it for yourself in the heat that comes off a road as it cools after sunset. This phenomenon is particularly noticeable on a cloudless night because, without clouds, the heat we and everything around us radiates can more easily make it through Earth's atmosphere, all the way to the vast, cold reaches of space.