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environment, power, and society for the twenty-first century: the hierarchy of energy
howard t. odum 2007 to read next
energy basis for man and nature
howard t. odum, elizabeth c. odum 1976 to read next
energy
eugene odum
on the cycle of energy as a principle for understanding living processes
shift in a national virtual energy network
zhenci xu et al. 2019
http://dx.doi.org/10.1016/j.apenergy.2019.03.099
energy leaves its environmental footprint home.
In this month's journal Applied Energy, MSU researchers examine China's flow of virtual energy -- the energy used to produce goods and products in one place that are shipped away. What they found was that virtual energy flowed from less-populated, energy-scarce areas in China's western regions to booming cities in the energy-abundant east.
In fact, the virtual energy transferred west to east was much greater than the physical energy that moves through China's massive infrastructure investment, the West-To-East Electricity Transmission Project. China is a powerful model of energy use, having surpassed the United States. In 2013, nearly 22 percent of global energy use occurred in China.
Conserving energy and managing its accompanying environmental impacts are a growing concern across the world, and it is crucial to take a holistic look at all the ways energy is used and moved," said Jianguo "Jack" Liu, Rachel Carson Chair in Sustainability of MSU's Center for Systems Integration and Sustainability (CSIS). "Only when we understand the full picture of who is producing energy and who is consuming it in all its forms can we make effective policy decisions."
Virtual energy is considered critical to avoiding regional energy crises since commodities traded from one location to another include virtual energy. This means the importing area can avoid expending the energy to produce the imported commodities. The paper "Shift in a National Virtual Energy Network" examines how a region's energy haves and have-nots meet economic and energy needs by acknowledging energy is tightly wound around economic growth and demand.
The researchers are first to focus on energy use after the 2008 global financial crisis, seeing how economic desperation can have a big, not always obvious, impact on energy -- and the pollution and environmental degradation that can accompany its use.
"China, like a lot of places across the globe, has an uneven distribution of energy resources, and China also is developing quickly," said the article's first author Zhenci Xu, an MSU-CSIS PhD student. "We wanted to understand the true paths of energy use when economic growth kicks into gear after a financial crisis. Eventually, all the costs of energy use, including environmental damage and pollution, have to be accounted for, and current policies focus primarily on physical energy, not virtual energy."
The researchers found a persistent flow of total virtual energy from energy-scare to energy-abundant provinces increased from 43.2% in 2007 to 47.5% in 2012. Following the framework of metacoupling (socioeconomic-environmental interactions within as well as between adjacent and distant places), they also discovered after the financial crisis, trade was taking place between distant provinces -- trade that came with energy's environmental footprint.
The authors note these types of analyses are needed across the globe to guide policies that hold the areas that are shifting their energy consumption to appropriately contribute to mitigating the true costs of energy.
•Virtual energy transferred from energy-scarce to energy-abundant provinces in China increased.
•Changes in flow pattern of China’s virtual energy network since the financial crisis were revealed.
•Most provinces had more distant virtual energy trade than nearby virtual energy trade.
•Virtual energy flowing from west China to east China was greater than physical energy through the WTEETP.
Energy is one of the most fundamental resources for humans and nature. Virtual energy transfer is considered one potential mechanism to alleviate energy shortages and support socioeconomic development in energy-scarce regions. However, little research has explored the change in flow pattern of national virtual energy trade since the 2008 global financial crisis. To fill this knowledge gap, we choose China’s interprovincial virtual energy transfer network as a demonstration, since China is the world's biggest energy consumer and features a starkly uneven spatial distribution of energy resources. Surprisingly, the total virtual energy transferred from energy-scarce to energy-abundant provinces increased from 43.2% to 47.5% from 2007 to 2012. In particular, the virtual oil which transferred from energy-scarce to energy-abundant provinces grew from 51.5% in 2007 to 54.0% in 2012. The percentage of provinces that transferred a greater amount of total virtual energy than was consumed internally increased from 23.3% in 2007 to 36.7% in 2012. Unexpectedly, the total virtual energy flowing from west China to east China was much greater than physical energy transferred through the West-To-East Electricity Transmission Project (WTEETP). This study suggests that it would be interesting to study patterns of interactions of virtual energy networks in other countries.
energy theory of periodic economic growth
adrian bejan et al. 2020
http://dx.doi.org/10.1002/er.5267
posits that recessions emerge as a natural feature of physics, rooted in the time-dependent movement of spreading over an area.
“This theory sheds light on common questions such as whether or not history repeats itself or if the economy is stable or not,” said Bejan. “These are questions that can find answers from physics. There exist universal mechanisms that give rise to laws governing the growth of economics. And the answer to sustaining that growth lies in innovation.”
Bejan’s conclusion combines the ideas behind two previous papers detailing the prevalence of S-curves in all corners of life and the direct link between economics and fuel consumption.
In 2011, Bejan predicted that the growth of innumerable spreading phenomena over time follows the shape of an “S curve” otherwise known as the sigmoid function, and that this phenomena is a result of the constructal law that he penned in 1996. For example, a bottle of milk spilled on the floor will have a small initial footprint, followed by a rapid finger-shaped expansion across the kitchen’s tiles, followed by a final phase of slow creep. This same history of slow, fast, slow can be seen in chemical reactions, population growth, the adoption of new technology and even the spreading of new ideas.
Several years later, Bejan tied together economics and physics, showing that physics accounts for the proportionality between a nation’s gross domestic product and its annual consumption of fuel. “Pushing requires power, and power requires fuel, whether it is food that powers the human body or gasoline that powers cars,” said Bejan. “And the amount of fuel consumed by a nation is directly related to its economic growth. So really, physics and economics are two sides of the same coin.”
In his new work, Bejan replaces the concepts of power with the concepts of economics including money, savings, time and bubbles. He shows that, given the ability to produce excess power and lend it to others as money, the flow of money being spent to push things around a given area looks exactly like the flow of power being used for the same purpose.
“The ability to save and lend, for money to flow between neighbors across the globe, is a chain reaction,” said Bejan. “Thus economic development as a whole is a chain reaction, and the physics of that phenomenon is detailed in this paper.”
Putting the two concepts together, Bejan shows that the “S” curve of the economic productivity of a commodity clashes with the linear curve of investment. At first, the S curve is below the line, and the investment is a speculative ray of hope. After time, the S curve moves above the investment line and generates prosperity and promise. But as the adoption or usefulness of that commodity, idea or invention wanes, the S curve reaches its plateau and it inevitably crosses back to the wrong side of the investment line.
This is when economic downturns strike. But while Bejan says this event is inevitable for anything and everything that is bought and sold, it doesn’t mean that the entire economy has to take a nosedive.
“Everything that spreads has a finite life, and if you don’t do something to postpone that precipice, then you will fall over the cliff,” said Bejan. “But a market that is free is capable of generating new S curves on top of new S curves. So as long as people are being innovative and creative and bringing large enough new S curves to the picture, the general trend of economic growth can continue.”
abstract This article shows that the sudden end of economic expansion (movement, wealth) emerges as a natural, physical feature of the spreading movement, which has access to power (money), freedom to morph, and power storage (savings) for future movement on even greater areas. The movement is driven by power generation, which is interspaced with power savings on the same area. The theory is constructed systematically from the physical basis of economics concepts (money, savings, time, and bubbles) to a physics model that accounts for the time‐dependent spreading of movement on an area. Previous study has shown that physics accounts for the proportionality between the annual wealth (GDP) of a population and the annual consumption of fuel to generate power for that population. The present theory extends this view to the more realistic situation where every movement in society (wealth and fuel consumption) is time dependent.
phenological synchronization disrupts trophic interactions between kodiak brown bears and salmon
william w. deacy et al. 2017
dx.doi.org/10.1073/pnas.1705248114
Climate change is altering the seasonal timing of biological events, effectively rescheduling the potential interactions among species. We know specialist consumers suffer when they fail to synchronize with their prey; however, little is known about how generalist consumers respond to phenological shifts across multiple food resources. This reshuffling may create novel temporal overlap between foods that were once separated in time. We examined how a generalist consumer, the Kodiak brown bear, responded when two key foods, red elderberry and sockeye salmon, became synchronized. Bears switched from eating salmon to elderberries, disrupting an ecological link that typically fertilizes terrestrial ecosystems and generates high mortality rates for salmon. These results demonstrate an underappreciated mechanism by which climate-altered phenologies can alter food webs.
Climate change is altering the seasonal timing of life cycle events in organisms across the planet, but the magnitude of change often varies among taxa [Thackeray SJ, et al. (2016) Nature 535:241–245]. This can cause the temporal relationships among species to change, altering the strength of interaction. A large body of work has explored what happens when coevolved species shift out of sync, but virtually no studies have documented the effects of climate-induced synchronization, which could remove temporal barriers between species and create novel interactions. We explored how a predator, the Kodiak brown bear (Ursus arctos middendorffi), responded to asymmetric phenological shifts between its primary trophic resources, sockeye salmon (Oncorhynchus nerka) and red elderberry (Sambucus racemosa). In years with anomalously high spring air temperatures, elderberry fruited several weeks earlier and became available during the period when salmon spawned in tributary streams. Bears departed salmon spawning streams, where they typically kill 25–75% of the salmon [Quinn TP, Cunningham CJ, Wirsing AJ (2016) Oecologia 183:415–429], to forage on berries on adjacent hillsides. This prey switching behavior attenuated an iconic predator–prey interaction and likely altered the many ecological functions that result from bears foraging on salmon [Helfield JM, Naiman RJ (2006) Ecosystems 9:167–180]. We document how climate-induced shifts in resource phenology can alter food webs through a mechanism other than trophic mismatch. The current emphasis on singular consumer-resource interactions fails to capture how climate-altered phenologies reschedule resource availability and alter how energy flows through ecosystems.
volcanic suppression of nile summer flooding triggers revolt and constrains interstate conflict in ancient egypt
joseph g. manning et al. 2017
dx.doi.org/10.1038/s41467-017-00957-y
dust outpaces bedrock in nutrient supply to montane forest ecosystems
s. m. aciego, et al. 2017
dx.doi.org/10.1038/ncomms14800
bioaerosol generation by raindrops on soil
young soo joung, zhifei ge, cullen r. buie 2017
dx.doi.org/10.1038/ncomms14668
temporal variation in pelagic food chain length in response to environmental change
rocio i. ruiz-cooley et al. 2017
dx.doi.org/10.1126/sciadv.1701140
hydrothermal vents trigger massive phytoplankton blooms in the southern ocean
mathieu ardyna et al. 2019
http://dx.doi.org/10.1038/s41467-019-09973-6
the first observed evidence of iron from the Southern Ocean's depths turning normally anemic surface waters into hotspots for phytoplankton -- the tiny algae that sustain the marine food web, pull heat-trapping carbon dioxide out of the air and produce a huge amount of the oxygen we breathe. "Our study shows that iron from hydrothermal vents can well up, travel across hundreds of miles of open ocean and allow phytoplankton to thrive in some very unexpected places," he said.
Kevin Arrigo, a professor of Earth system science and senior author of the paper, called the findings "important because they show how intimately linked the deep ocean and surface ocean can be."
Mysterious blooms
Phytoplankton need iron to thrive, and that limits their abundance in vast swaths of the ocean where concentrations of the nutrient are low. But when conditions are right, phytoplankton can also grow explosively, blooming across thousands of square miles in a matter of days.
That's what Ardyna noticed recently as he looked at data recorded in 2014 and 2015 by a fleet of floating robots outfitted with optical sensors in the Southern Ocean. More than 1,300 miles off the coast of Antarctica and 1,400 miles from the African continent, two unexpectedly large blooms cropped up in an area known for severe iron shortages and low concentrations of chlorophyll, an indicator of phytoplankton populations.
Massive blooms in this region could only be possible with an influx of iron. Ardyna and Arrigo quickly ruled out the ocean's most common sources, including continental shelves, melting sea ice and atmospheric dust, which were simply too far away to have much influence.
That led them to suspect that the nutrient must be welling up from below, possibly from a string of hydrothermal vents that dot a mid-ocean ridge 750 miles from where the massive blooms had inexplicably appeared. To help test their hypothesis, they recruited an international team of collaborators specialized in various aspects of oceanography and modeling.
"It has long been known that hydrothermal vents create unique and profound oases of life," Ardyna said. Until recently, scientists generally believed those nourishing effects remained fairly local. But a growing amount of evidence from computer simulations of ocean dynamics has hinted that iron and other life-sustaining elements spewed from hydrothermal vents may in fact fuel planktonic blooms over much wider areas.
However, direct measurements have been lacking.
In the Southern Ocean, that's partly due to the remote location, extreme cold and rough seas, which make it difficult to study up close or collect accurate data. "Your sensors have to be in the right place at the right time to see these blooms," Ardyna said. "Satellites can underestimate intensity or miss them altogether because of bad coverage or strong mixing of the water column, which pushes phytoplankton down too deep for satellites to see."
Clues from space, floating robots
To track the flow of particles from the vents on the mid-ocean ridge, the scientists analyzed data from satellites measuring chlorophyll and from autonomous, sensor-laden buoys known as Argo floats. As they dive and drift along ocean currents, some of these buoys detect chlorophyll and other proxies for phytoplankton biomass. "The floats give us precious and unique data, covering a large section of the water column down to 1,000 meters deep during an entire annual cycle," Ardyna said.
The scientists couldn't directly measure iron in the water, but instead analyzed measurements of helium collected by scientific cruises in the 1990s. The presence of helium signals waters influenced by hydrothermal vents, which funnel large amounts of primordial helium from beneath Earth's crust.
The chlorophyll, phytoplankton and helium data suggest that a powerful current circling Antarctica grabs nutrients rising up from vents. Two turbulent, fast-moving branches of the current then shuttle the nutrients eastward for a month or two before serving them like a banquet to undernourished phytoplankton. Together with the arrival of spring sunshine that phytoplankton need for photosynthesis, the delivery triggers a massive bloom that can likely absorb and store significant amounts of carbon from the atmosphere, said Arrigo, who is also the Donald and Donald M. Steel Professor in Earth Sciences.
Over time, the blooms drift eastward toward the current racing around Antarctica and fade as sea creatures devour them. "We suspect these hotspots are either consumed or exported to deep waters," Ardyna said.
Each bloom lasts little more than a month, but the mechanisms that trigger them are likely to be more common in the global ocean than scientists previously suspected.
"Hydrothermal vents are scattered all over the ocean floor," Ardyna said. Knowing about the pathways that bring their nutrients up to surface waters will help researchers make more accurate calculations about the flow of carbon in the world's oceans. "Much remains to be done to reveal other potential hotspots and quantify how this mechanism is altering the carbon cycle."
abstract Hydrothermal activity is significant in regulating the dynamics of trace elements in the ocean. Biogeochemical models suggest that hydrothermal iron might play an important role in the iron-depleted Southern Ocean by enhancing the biological pump. However, the ability of this mechanism to affect large-scale biogeochemistry and the pathways by which hydrothermal iron reach the surface layer have not been observationally constrained. Here we present the first observational evidence of upwelled hydrothermally influenced deep waters stimulating massive phytoplankton blooms in the Southern Ocean. Captured by profiling floats, two blooms were observed in the vicinity of the Antarctic Circumpolar Current, downstream of active hydrothermal vents along the Southwest Indian Ridge. These hotspots of biological activity are supported by mixing of hydrothermally sourced iron stimulated by flow-topography interactions. Such findings reveal the important role of hydrothermal vents on surface biogeochemistry, potentially fueling local hotspot sinks for atmospheric CO2 by enhancing the biological pump.
critical impact of vegetation physiology on the continental hydrologic cycle in response to increasing co2
léo lemordant et al. 2018
http://dx.doi.org/10.1073/pnas.1720712115
skillful empirical subseasonal prediction of landfalling atmospheric river activity using the madden–julian oscillation and quasi-biennial oscillation
bryan d. mundhenk et al. 2018
http://dx.doi.org/10.1038/s41612-017-0008-2
climatology of atmospheric river interactions with the southeastern united states coastline
neil debbage, paul miller, shaina poore, kaitlin morano, thomas mote, j. marshall shepherd. a 2017
10.1002/joc.5000
overview of the arkstorm scenario
united states geological service 2010
of2010-1312_text.pdf
the coming megafloods
michael d. dettinger and b. lynn ingram 2013
ComingMegaFloos4.pdf
causes of extreme ridges that induce california droughts
haiyan teng, grant branstator 2017
dx.doi.org/10.1175/JCLI-D-16-0524.1
tropospheric waveguide teleconnections and their seasonality
grant branstator, haiyan teng 2017
dx.doi.org/10.1175/JAS-D-16-0305.1
walkable city: how downtown can save america, one step at a time
jeff speck 2012 9780374285814
low-temperature conversion of carbon dioxide to methane in an electric field
kensei yamada et al. 2020
http://dx.doi.org/10.1246/cl.190930
“To recycle carbon dioxide into methane, an established industrial method involves the reaction of hydrogen and carbon dioxide using a ruthenium-based catalyst at temperatures of 300 to 400 degrees Celsius, but this method limited how much and when methane could be produced since it requires such high temperature,” Sekine says. “Additionally, operation at low temperatures was demonstrated to be favorable to improve carbon dioxide conversion and increase the amount of methane produced.”
In this newly-developed method reported in Chemistry Letters, carbon dioxide can be converted into methane more efficiently and quickly in the 100 degrees Celsius range.
“This method involves a reaction of nanoparticles called cerium oxide with carbon dioxide in presence of ruthenium catalyst with an electric field,” explains Sekine. “The results show that the catalyst exhibited high and stable catalytic activity for converting carbon dioxide to methane through hydrogenation with the electric field.”
abstract CO2 methanation was conducted at low temperatures with an electric field. Results show that 5 wt %Ru/CeO2 catalyst exhibited high and stable catalytic activity for CO2 methanation with the electric field. The kinetic investigations and in-situ DRIFTS measurements revealed that Ru/CeO2 catalyst promoted CO2 methanation and Ru at the Ru–CeO2 interface (low-coordinated Ru sites) contributes to the reverse water gas shift reaction at low temperatures in the electric field.
coherent modulation of the sea-level annual cycle in the united states by atlantic rossby waves
francisco m. calafat et al. 2018
http://dx.doi.org/10.1038/s41467-018-04898-y
the detection of rossby-like waves on the sun
scott w. mcintosh, william j. cramer, manuel pichardo marcano, robert j. leamon 2017
dx.doi.org/10.1038/s41550-017-0086
your money or your life? the carbon-development paradox
steinberger, jk 2020
http://dx.doi.org/10.1088/1748-9326/ab7461
Growing consumption of energy and fossil fuels over four decades did not play a significant role in increasing life expectancy across 70 countries.
New research, led by the University of Leeds, has quantified the importance of different development factors to improvements in physical health on an international scale.
Because a country’s energy use is highly correlated with life expectancy at any single point in time, it has generally been assumed that growth in energy use is required for increases in life expectancy.
However, the findings of the new research revealed an unexpected paradox. Whilst energy and fossil fuel emissions were indeed strongly correlated with life expectancy at any single point in time, over a long period they were not found to be closely linked.
Between 1971 and 2014, increases in carbon emissions and primary energy use per person accounted for at most a quarter of the improvements in international life expectancy. International life expectancy improved by 14 years overall, meaning that expanded fossil fuel use and ensuing emissions accounted for less than 4 of these years.
Increases in energy use were, however, tied to 90% of growth in national incomes, measured as Gross Domestic Product (GDP) per person.
In the context of the climate crisis and the need to dramatically reduce global energy use, these findings provide reassurance that countries could improve their citizens’ lives without requiring more energy consumption.
The research was published today in Environmental Research Letters.
Lead author Professor Julia Steinberger, from the University of Leeds, said: “Increased use of fossil fuels and primary energy may have helped make countries richer, but it was not responsible for much improvement in human health.
“Our results directly counter the claims by fossil fuel companies that their products are necessary for well-being. Reducing emissions and primary energy use, while maintaining or enhancing the health of populations, should be possible.”
Co-author Dr William Lamb, from the Mercator Research Institute on Global Commons and Climate Change (MCC), said: “In terms of achieving the Sustainable Development Goals, the challenge is to provide affordable, reliable, and clean energy for all, while ensuring that people enjoy open and equitable opportunities to cover their basic needs, such as nutrition, health care, education, safe water, clean air, among others.”
Co-author Dr Marco Sakai, from the University of York, said: “We have to recognise the dual emergency that we face as humanity today. We need to not only stop climate change as soon as possible, but we also need at the same time to bring billions of people out of poverty across the world. Now we have evidence that we don’t need to keep injecting fossil fuels into our economies or pursuing everlasting economic growth to face this dual emergency.
“So the question essentially comes down to this: should our societies be prioritising fossil-fuelled economic growth, or instead use clean energy to prioritise people’s lives?”
The researchers also found that the growth in a country’s income — its gross domestic product (GDP) per person — was only responsible for a minor portion of improvements in life expectancy — at most 29%.
Conversely, a different measure of the economy that removes the differences in the cost of living across countries, called purchasing power parity (PPP), was more closely tied to life expectancy over the 44-year period. Increases in PPP were tied to over half of the increases in life expectancy over the study period.
On this point, Dr Sakai said: “What this suggests is the importance of eradicating extreme levels of inequality within and across countries. Solving this dual challenge does not require adding more stuff in our economies, but prioritising wellbeing and distributing existing resources more equally.”
The research was led by the University of Leeds along with Mercator Research Institute on Global Commons and Climate Change, Germany, and the University of York.
Development paradox
Previous research has established that there is a close correlation between a country’s energy use and its average life expectancy at any one point in time.
However, the researchers used a new analysis method, called Functional Dynamic Composition, to understand how energy use, the economy and well-being, change over time, to establish the extent to which they are influencing each other.
Their new method cannot show causality, only association. However, a lack of association is evidence of a lack of causation.
The findings suggest that prioritising economic growth and burning increasing amounts of fossil fuels are not going to lead to significant improvements in human lifespan. Instead development efforts should focus directly on wellbeing goals such as satisfying human needs, including healthcare, good nutrition, and safe dwellings powered by clean energy.
Dr Lamb said: “The implications of this for the climate crisis are profound: rapidly decreasing emissions, even through reductions in energy use, need not be catastrophic in terms of our well-being, so long as human needs, such as food and household electricity, are prioritised.
“In short, this research shows we need to prioritise human well-being and acting on climate change over economic growth, because more fossil fuels do not lead to healthier lives.”
What does improve wellbeing?
Whilst total primary energy use and carbon emissions accounted for a small proportion of improvements in life expectancy (26% and 22% respectively), a separate measure, residential electricity, accounted for 60% of the wellbeing improvements.
Residential electricity provides a measure of the amount of high quality and versatile energy being used directly within households.
The final development indicator included in the analysis was a measure of nutrition — the amount of calories per person in a country’s food supply. Food supply was found to account for 45% of wellbeing improvements — despite itself only growing by a modest 18% during the period covered by the study.
Professor Steinberger said: “At this moment in history — when we are overconsuming and destroying environmental systems, whilst simultaneously trying to bring billions out of poverty to a good standard of living — it is vital that we re-orient our priorities so that people and planet can prosper as one.
“In terms of policies and politics, we need to face the reality that feeding fossil fuels to the economy is far less beneficial to human development outcomes than directly satisfying human needs.”
megaflash lightning extremes
world meteorological organization 2020
public.wmo.int/en/media/press-release/wmo-certifies-megaflash-lightning-extremes
estimation of global final stage energy-return-on-investment for fossil fuels with comparison to renewable energy sources
paul brockway et al. 2019
http://dx.doi.org/10.1038/s41560-019-0425-z
An enduring argument for the ongoing use of fossil fuels is their high energy return on energy investment. This refers to the ratio of how much energy a source such as coal or oil will produce compared to how much energy it takes to extract.
Previously, the estimated ratios for energy return on investment (EROI) have favoured fossil fuels over renewable energy sources. Oil, coal and gas are typically calculated to have ratios above 25:1, this means roughly one barrel of oil used yields 25 barrels to put back into the energy economy. Renewable energy sources often have much lower estimated ratios, below 10:1.
However, these fossil fuel ratios are measured at the extraction stage, when oil, coal or gas is removed from the ground. These ratios do not take into account the energy required to transform oil, coal and gas into finished fuels such as petrol used in cars, or electricity used by households.
A new study, co-authored by scientists from the Sustainability Research Institute at the University of Leeds, has calculated the EROI for fossil fuels over a 16 year period and found that at the finished fuel stage, the ratios are much closer to those of renewable energy sources -- roughly 6:1, and potentially as low as 3:1 in the case of electricity.
The study, undertaken as part of the UK Energy Research Centre programme and published today in Nature Energy, warns that the increasing energy costs of extracting fossil fuels will cause the ratios to continue to decline, pushing energy resources towards a "net energy cliff." This is when net energy available to society declines rapidly due to the increasing amounts of "parasitical" energy required in the energy production.
The researchers emphasise that these findings make a strong case for rapidly stepping up investment in renewable energy sources and that the renewables transition may actually halt -- or reverse -- the decline in global EROI at the finished fuel stage.
Study co-author Dr Paul Brockway, an expert in energy-economy modelling at the School of Earth and Environment at Leeds, said: "Measuring energy return on investment of fossil fuels at the extraction stage gives the misleading impression that we have plenty of time for a renewable energy transition before energy constraints are a concern.
"Those measurements are essentially predicating the potential energy output of newly-extracted sources like crude oil. But crude oil isn't used to heat our homes or power our cars. It makes more sense for calculations to consider where energy enters the economy, and that puts us much closer to the precipice.
"The ratios will only continue to decline because we are swiftly reaching the point where all the easily-accessible fossil fuel sources are becoming exhausted. By stepping up investment in renewable energy sources we can help ensure that we don't tip over the edge."
Study co-author Dr Lina Brand-Correa, an expert in the social aspects of energy use on the Living Well within Limits (LiLi) project at Leeds said: "There is too much focus on the initial economic costs of transitioning to renewable energy.
"Renewable infrastructure, such as wind farms and solar panels, do require a large initial investment, which is one of the reasons why their energy return on investment ratios have been so low until now.
"But the average energy return on investment for all fossil fuels at the finished fuel stage declined by roughly 23 per cent in the 16 year period we considered. This decline will lead to constraints on the energy available to society in the not-so-distant future, and these constraints might unfold in rapid and unexpected ways.
"Once the renewable infrastructure is built and dependency on fossil fuel decreases, the energy-return-on-investment for renewable sources should go up. This must be considered for future policy and energy infrastructure investments decisions, not only to meet climate change mitigation commitments but to ensure society continues to have access to the energy it needs."
abstract Under many scenarios, fossil fuels are projected to remain the dominant energy source until at least 2050. However, harder-to-reach fossil fuels require more energy to extract and, hence, are coming at an increasing ‘energy cost’. Associated declines in fossil fuel energy-return-on-investment ratios at first appear of little concern, given that published estimates for oil, coal and gas are typically above 25:1. However, such ratios are measured at the primary energy stage and should instead be estimated at the final stage where energy enters the economy (for example, electricity and petrol). Here, we calculate global time series (1995–2011) energy-return-on-investment ratios for fossil fuels at both primary and final energy stages. We concur with common primary-stage estimates (~30:1), but find very low ratios at the final stage: around 6:1 and declining. This implies that fossil fuel energy-return-on-investment ratios may be much closer to those of renewables than previously expected and that they could decline precipitously in the near future.
effect of cu–sn–se liquid phase on grain growth and efficiency of cztsse solar cells
se‐yun kim et al. 2020
doi.org/10.1002/aenm.201903173
experimental demonstration of energy harvesting from the sky using the negative illumination effect of a semiconductor photodiode
masashi ono et al. 2019
http://dx.doi.org/10.1063/1.5089783
In contrast to leveraging incoming energy as a normal solar cell would, the negative illumination effect allows electrical energy to be harvested as heat leaves a surface. Today's technology, though, does not capture energy over these negative temperature differences as efficiently.
By pointing their device toward space, whose temperature approaches mere degrees from absolute zero, the group was able to find a great enough temperature difference to generate power through an early design.
"The amount of power that we can generate with this experiment, at the moment, is far below what the theoretical limit is," said Masashi Ono, another author on the paper.
The group found that their negative illumination diode generated about 64 nanowatts per square meter, a tiny amount of electricity, but an important proof of concept, that the authors can improve on by enhancing the quantum optoelectronic properties of the materials they use.
Calculations made after the diode created electricity showed that, when atmospheric effects are taken into consideration, the current device can theoretically generate almost 4 watts per square meter, roughly one million times what the group's device generated and enough to help power machinery that is required to run at night.
By comparison, today's solar panels generate 100 to 200 watts per square meter.
While the results show promise for ground-based devices directed to the sky, Fan said the same principle could be used to recover waste heat from machines. For now, he and his group are focusing on improving their device's performance.
abstract We experimentally demonstrate electric power generation from the coldness of the universe directly, using the negative illumination effect when an infrared semiconductor diode faces the sky. Our theoretical model, accounting for the experimental results, indicates that the performance of such a power generation scheme is strongly influenced by the degree of matching between the responsivity spectrum and the atmospheric transparency window, as well as the quantum efficiency of the diode. A Shockley-Queisser analysis of an ideal optimized diode, taking into consideration the realistic transmissivity spectrum of the atmosphere, indicates the theoretical maximum power density of 3.99 W/m2 with the diode temperature at 293 K. The results here point to a pathway towards night-time power generation.
nighttime photovoltaic cells: electrical power generation by optically coupling with deep space
tristan deppe, jeremy n. munday 2020
http://dx.doi.org/10.1021/acsphotonics.9b00679
developing prototypes of these nighttime solar cells that can generate small amounts of power. The researchers hope to improve the power output and efficiency of the devices.
Munday said that the process is similar to the way a normal solar cell works, but in reverse. An object that is hot compared to its surroundings will radiate heat as infrared light. A conventional solar cell is cool compared to the sun, so it absorbs light.
Space is really, really cold, so if you have a warm object and point it at the sky, it will radiate heat toward it. People have been using this phenomenon for nighttime cooling for hundreds of years. In the last five years, Munday said, there has been a lot of interest in devices that can do this during the daytime (by filtering out sunlight or pointing away from the sun).
Generating power by radiating heat
There’s another kind of device called a thermoradiative cell that generates power by radiating heat to its surroundings. Researchers have explored using them to capture waste heat from engines.
“We were thinking, what if we took one of these devices and put it in a warm area and pointed it at the sky,” Munday said.
This thermoradiative cell pointed at the night sky would emit infrared light because it is warmer than outer space.
“A regular solar cell generates power by absorbing sunlight, which causes a voltage to appear across the device and for current to flow. In these new devices, light is instead emitted and the current and voltage go in the opposite direction, but you still generate power,” Munday said. “You have to use different materials, but the physics is the same.”
The device would work during the day as well, if you took steps to either block direct sunlight or pointed it away from the sun. Because this new type of solar cell could potentially operate around the clock, it is an intriguing option to balance the power grid over the day-night cycle.
abstract Photovoltaics possess significant potential due to the abundance of solar power incident on earth; however, they can only generate electricity during daylight hours. In order to produce electrical power after the sun has set, we consider an alternative photovoltaic concept that uses the earth as a heat source and the night sky as a heat sink, resulting in a “nighttime photovoltaic cell” that employs thermoradiative photovoltaics and concepts from the advancing field of radiative cooling. In this Perspective, we discuss the principles of thermoradiative photovoltaics, the theoretical limits of applying this concept to coupling with deep space, the potential of advanced radiative cooling techniques to enhance their performance, and a discussion of the practical limits, scalability, and integrability of this nighttime photovoltaic concept.
heat flowing from cold to hot without external intervention by using a “thermal inductor”
a. schilling et al. 2019
http://dx.doi.org/10.1126/sciadv.aat9953
Cooling below room temperature
The results of a recent experiment carried out by the research group of Prof. Andreas Schilling in the Department of Physics at the University of Zurich (UZH) appear at first sight to challenge the second law of thermodynamics. The researchers managed to cool a nine-gram piece of copper from over 100°C to significantly below room temperature without an external power supply. "Theoretically, this experimental device could turn boiling water to ice, without using any energy," says Schilling.
Creating oscillating heat currents
To achieve this, the researchers used a Peltier element, a component commonly used, for example, to cool minibars in hotel rooms. These elements can transform electric currents into temperature differences. The researchers had already used this type of element in previous experiments, in connection with an electric inductor, to create an oscillating heat current in which the flow of heat between two bodies perpetually changed direction. In this scenario, heat also temporarily flows from a colder to a warmer object so that the colder object is cooled down further. This kind of "thermal oscillating circuit" in effect contains a "thermal inductor." It functions in the same way as an electrical oscillating circuit, in which the voltage oscillates with a constantly changing sign.
Laws of physics remain intact
Until now, Schilling's team had only operated these thermal oscillating circuits using an energy source. The researchers have now shown for the first time that this kind of thermal oscillating circuit can also be operated "passively," i.e. with no external power supply. Thermal oscillations still occurred and, after a while, heat flowed directly from the colder copper to a warmer heat bath with a temperature of 22°C, without being temporarily transformed into another form of energy. Despite this, the authors were also able to show that the process does not actually contradict any laws of physics. To prove it, they considered the change in entropy of the whole system and showed that it increased with time -- fully in accordance with the second law of thermodynamics.
Potential application still a long way off
Although the team recorded a difference of only about 2°C compared to the ambient temperature in the experiment, this was mainly due to the performance limitations of the commercial Peltier element used. According to Schilling, it would be possible in theory to achieve cooling of up to -47°C under the same conditions, if the "ideal" Peltier element -- yet to be invented -- could be used: "With this very simple technology, large amounts of hot solid, liquid or gaseous materials could be cooled to well below room temperature without any energy consumption."
The passive thermal circuit could also be used as often as desired, without the need to connect it to a power supply. However, Schilling admits that a large-scale application of the technique is still a long way off. One reason for this is that the Peltier elements currently available are not efficient enough. Furthermore, the current set-up requires the use of superconducting inductors to minimize electric losses.
Established perceptions challenged
The UZH physicist considers the work more significant than a mere "proof-of-principle" study: "At first sight, the experiments appear to be a kind of thermodynamic magic, thereby challenging to some extent our traditional perceptions of the flow of heat."
abstract The cooling of boiling water all the way down to freezing, by thermally connecting it to a thermal bath held at ambient temperature without external intervention, would be quite unexpected. We describe the equivalent of a “thermal inductor,” composed of a Peltier element and an electric inductance, which can drive the temperature difference between two bodies to change sign by imposing inertia on the heat flowing between them, and enable continuing heat transfer from the chilling body to its warmer counterpart without the need of an external driving force. We demonstrate its operation in an experiment and show that the process can pass through a series of quasi-equilibrium states while fully complying with the second law of thermodynamics. This thermal inductor extends the analogy between electrical and thermal circuits and could serve, with further progress in thermoelectric materials, to cool hot materials well below ambient temperature without external energy supplies or moving parts.
nonreciprocal control and cooling of phonon modes in an optomechanical system
h. xu et al. 2019
http://dx.doi.org/10.1038/s41586-019-1061-2
"This is an experiment in which we make a one-way route for sound waves," said Harris, a Yale physics professor and the study's principal investigator. "Specifically, we have two acoustic resonators. Sound stored in the first resonator can leak into the second, but not vice versa."
Harris said his team was able to achieve the result with a "tuning knob" -- a laser setting, actually -- that can weaken or strengthen a sound wave, depending on the sound wave's direction.
Then the researchers took their experiment to a different level. Because heat consists mostly of vibrations, they applied the same ideas to the flow of heat from one object to another.
"By using our one-way sound trick, we can make heat flow from point A to point B, or from B to A, regardless of which one is colder or hotter," Harris said. "This would be like dropping an ice cube into a glass of hot water and having the ice cubes get colder and colder while the water around them gets warmer and warmer. Then, by changing a single setting on our laser, heat is made to flow the usual way, and the ice cubes gradually warm and melt while the liquid water cools a bit. Though in our experiments it's not ice cubes and water that are exchanging heat, but rather two acoustic resonators."
Although some of the most basic examples of acoustic resonators are found in musical instruments or even automobile exhaust pipes, they're also found in a variety of electronics. They are used as sensors, filters, and transducers because of their compatibility with a wide range of materials, frequencies, and fabrication processes.
abstract Mechanical resonators are important components of devices that range from gravitational wave detectors to cellular telephones. They serve as high-performance transducers, sensors and filters by offering low dissipation, tunable coupling to diverse physical systems, and compatibility with a wide range of frequencies, materials and fabrication processes. Systems of mechanical resonators typically obey reciprocity, which ensures that the phonon transmission coefficient between any two resonators is independent of the direction of transmission1,2. Reciprocity must be broken to realize devices (such as isolators and circulators) that provide one-way propagation of acoustic energy between resonators. Such devices are crucial for protecting active elements, mitigating noise and operating full-duplex transceivers. Until now, nonreciprocal phononic devices3,4,5,6,7,8,9,10,11 have not simultaneously combined the features necessary for robust operation: strong nonreciprocity, in situ tunability, compact integration and continuous operation. Furthermore, they have been applied only to coherent signals (rather than fluctuations or noise), and have been realized exclusively in travelling-wave systems (rather than resonators). Here we describe a scheme that uses the standard cavity-optomechanical interaction to produce robust nonreciprocal coupling between phononic resonators. This scheme provides about 30 decibels of isolation in continuous operation and can be tuned in situ simply via the phases of the drive tones applied to the cavity. In addition, by directly monitoring the dynamics of the resonators we show that this nonreciprocity can control thermal fluctuations, and that this control represents a way to cool phononic resonators.
reversing the direction of heat flow using quantum correlations
kaonan micadei et al. 2019
http://dx.doi.org/10.1038/s41467-019-10333-7
"Correlations can be said to represent information shared among different systems. In the macroscopic world described by classical physics, the addition of energy from outside can reverse the flow of heat in a system so that it flows from cold to hot. This is what happens in an ordinary refrigerator, for example," Serra told.
"It's possible to say that in our nanoscopic experiment, the quantum correlations produced an analogous effect to that of added energy. The direction of flow was reversed without violating the second law of thermodynamics. On the contrary, if we take into account elements of information theory in describing the transfer of heat, we find a generalized form of the second law and demonstrate the role of quantum correlations in the process."
The experiment was performed with a sample of chloroform molecules (a hydrogen atom, a carbon atom and three chlorine atoms) marked with a carbon-13 isotope. The sample was diluted in solution and studied using a nuclear magnetic resonance spectrometer, similar to the MRI scanners used in hospitals but with a much stronger magnetic field.
"We investigated temperature changes in the spins of the nuclei of the hydrogen and carbon atoms. The chlorine atoms had no material role in the experiment. We used radio frequency pulses to place the spin of each nucleus at a different temperature, one cooler, another warmer. The temperature differences were small, on the order of tens of billionths of 1 Kelvin, but we now have techniques that enable us to manipulate and measure quantum systems with extreme precision. In this case, we measured the radio frequency fluctuations produced by the atomic nuclei," Serra said.
The researchers explored two situations: in one, the hydrogen and carbon nuclei began the process uncorrelated, and in the other, they were initially quantum-correlated.
"In the first case, with the nuclei uncorrelated, we observed heat flowing in the usual direction, from hot to cold, until both nuclei were at the same temperature. In the second, with the nuclei initially correlated, we observed heat flowing in the opposite direction, from cold to hot. The effect lasted a few thousandths of a second, until the initial correlation was consumed," Serra explained.
The most noteworthy aspect of this result is that it suggests a process of quantum refrigeration in which the addition of external energy (as is done in refrigerators and air conditioners to cool a specific environment) can be replaced by correlations, i.e., an exchange of information between objects.
Maxwell's demon
The idea that information can be used to reverse the direction of heat flow -- in other words, to bring about a local decrease in entropy -- arose in classical physics in the mid-nineteenth century, long before information theory was invented.
It was a thought experiment proposed in 1867 by James Clerk Maxwell (1831-1879), who, among other things, created the famous classical electromagnetism equations. In this thought experiment, which sparked a heated controversy at the time, the great Scottish physicist said that if there were a being capable of knowing the speed of each molecule of a gas and of manipulating all the molecules at the microscopic scale, this being could separate them into two recipients, placing faster-than-average molecules in one to create a hot compartment and slower-than-average molecules in the other to create a cold compartment. In this manner, a gas initially in thermal equilibrium owing to a mixture of faster and slower molecules would evolve to a differentiated state with less entropy.
Maxwell intended the thought experiment to prove that the second law of thermodynamics was merely statistical.
"The being he proposed, which was capable of intervening in the material world at the molecular or atomic scale, became known as 'Maxwell's demon'. It was a fiction invented by Maxwell to present his point of view. However, we're now actually able to operate at the atomic or even smaller scales, so that usual expectations are modified," Serra said.
The experiment conducted by Serra and collaborators and described in the article just published is a demonstration of this. It did not reproduce Maxwell's thought experiment, of course, but it produced an analogous result.
"When we talk about information, we're not referring to something intangible. Information requires a physical substrate, a memory. If you want to erase 1 bit of memory from a flash drive, you have to expend 10,000 times a minimum amount of energy consisting of the Boltzmann constant times the absolute temperature. This minimum of energy necessary to erase information is known as Landauer's principle. This explains why erasing information generates heat. Notebook batteries are consumed by heat more than anything else," Serra said.
What the researchers observed was that the information present in the quantum correlations can be used to perform work, in this case the transfer of heat from a colder to a hotter object, without consuming external energy.
"We can quantify the correlation of two systems by means of bits. Connections between quantum mechanics and information theory are creating what is known as quantum information science. From the practical standpoint, the effect we studied could one day be used to cool part of a quantum computer's processor," Serra said.
abstract Heat spontaneously flows from hot to cold in standard thermodynamics. However, the latter theory presupposes the absence of initial correlations between interacting systems. We here experimentally demonstrate the reversal of heat flow for two quantum correlated spins-1/2, initially prepared in local thermal states at different effective temperatures, employing a Nuclear Magnetic Resonance setup. We observe a spontaneous energy flow from the cold to the hot system. This process is enabled by a trade off between correlations and entropy that we quantify with information-theoretical quantities. These results highlight the subtle interplay of quantum mechanics, thermodynamics and information theory. They further provide a mechanism to control heat on the microscale.
a droplet-based electricity generator with high instantaneous power density
wanghuai xu et al. 2020
http://dx.doi.org/10.1038/s41586-020-1985-6
low-frequency kinetic energy contained in waves, tides, and even raindrops are not efficiently converted into electrical energy due to limitations in current technology. For example, a conventional droplet energy generator based on the triboelectric effect can generate electricity induced by contact electrification and electrostatic induction when a droplet hits a surface. However, the amount of charges generated on the surface is limited by the interfacial effect, and as a result, the energy conversion efficiency is quite low.
In order to improve the conversion efficiency, the research team has spent two years developing the DEG. Its instantaneous power density can reach up to 50.1 W/m2, thousands times higher than other similar devices without the use of FET-like design. And the energy conversion efficiency is markedly higher.
Professor Wang from CityU pointed out that there are two crucial factors for the invention. First, the team found that the continuous droplets impinging on PTFE, an electret material with a quasi-permanent electric charge, provides a new route for the accumulation and storage of high-density surface charges. They found that when water droplets continuously hit the surface of PTFE, the surface charges generated will accumulate and gradually reach a saturation. This new discovery helped to overcome the bottleneck of low charge density encountered in previous work.
Unique field-effect transistor-like structure
Another key feature of their design is a unique set of structures similar to a FET, which is a Nobel Prize in Physics winning innovation in 1956 and has become the basic building block of modern electronic devices nowadays. The device consists of an aluminium electrode, and an indium tin oxide (ITO) electrode with a film of PTFE deposited on it. The PTFE/ITO electrode is responsible for the charge generation, storage, and induction. When a falling water droplet hits and spreads on the PTFE/ITO surface, it naturally “bridges” the aluminium electrode and the PTFE/ITO electrode, translating the original system into a closed-loop electric circuit.
With this special design, a high density of surface charges can be accumulated on the PTFE through continuous droplet impinging. Meanwhile, when the spreading water connects the two electrodes, all the stored charges on the PTFE can be fully released for the generation of electric current. As a result, both the instantaneous power density and energy conversion efficiency are much higher.
“Our research shows that a drop of 100 microlitres (1 microlitre = one-millionth litre) of water released from a height of 15 cm can generate a voltage of over 140V. And the power generated can light up 100 small LED light bulbs,” said Professor Wang.
He added that the increase in instantaneous power density does not result from additional energy, but from the conversion of kinetic energy of water itself. “The kinetic energy entailed in falling water is due to gravity and can be regarded as free and renewable. It should be better utilized.”
Their research also shows that the reduction in relative humidity does not affect the efficiency of power generation. Also, both rainwater and seawater can be used to generate electricity.
Facilitates the sustainability of the world
Professor Wang hoped that the outcome of this research would help to harvest water energy to respond to the global problem of renewable energy shortage. “Generating power from raindrops instead of oil and nuclear energy can facilitate the sustainable development of the world,” he added.
He believed that in the long run, the new design could be applied and installed on different surfaces, where liquid in contact with solid, to fully utilize the low-frequency kinetic energy in water. This can range from the hull surface of ferry, coastline, to the surface of umbrellas or even inside water bottles.
abstract Extensive efforts have been made to harvest energy from water in the form of raindrops1,2,3,4,5,27, river and ocean waves28,29, tides9 and others10,11,12,13,14,15,16,17. However, achieving a high density of electrical power generation is challenging. Traditional hydraulic power generation mainly uses electromagnetic generators that are heavy, bulky, and become inefficient with low water supply. An alternative, the water-droplet/solid-based triboelectric nanogenerator, has so far generated peak power densities of less than one watt per square metre, owing to the limitations imposed by interfacial effects—as seen in characterizations of the charge generation and transfer that occur at solid–liquid1,2,3,25 or liquid–liquid26,18 interfaces. Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminium electrode. We show that spreading of an impinged water droplet on the device bridges the originally disconnected components into a closed-loop electrical system, transforming the conventional interfacial effect into a bulk effect, and so enhancing the instantaneous power density by several orders of magnitude over equivalent devices that are limited by interfacial effects.
power generation from ambient humidity using protein nanowires
xiaomeng liu et al. 2020
http://dx.doi.org/10.1038/s41586-020-2010-9
generate power even in areas with extremely low humidity such as the Sahara Desert. It has significant advantages over other forms of renewable energy including solar and wind, Lovley says, because unlike these other renewable energy sources, the Air-gen does not require sunlight or wind, and “it even works indoors.”
The Air-gen device requires only a thin film of protein nanowires less than 10 microns thick, the researchers explain. The bottom of the film rests on an electrode, while a smaller electrode that covers only part of the nanowire film sits on top. The film adsorbs water vapor from the atmosphere. A combination of the electrical conductivity and surface chemistry of the protein nanowires, coupled with the fine pores between the nanowires within the film, establishes the conditions that generate an electrical current between the two electrodes.
The researchers say that the current generation of Air-gen devices are able to power small electronics, and they expect to bring the invention to commercial scale soon. Next steps they plan include developing a small Air-gen “patch” that can power electronic wearables such as health and fitness monitors and smart watches, which would eliminate the requirement for traditional batteries. They also hope to develop Air-gens to apply to cell phones to eliminate periodic charging.
Yao says, “The ultimate goal is to make large-scale systems. For example, the technology might be incorporated into wall paint that could help power your home. Or, we may develop stand-alone air-powered generators that supply electricity off the grid. Once we get to an industrial scale for wire production, I fully expect that we can make large systems that will make a major contribution to sustainable energy production.”
Continuing to advance the practical biological capabilities of Geobacter, Lovley’s lab recently developed a new microbial strain to more rapidly and inexpensively mass produce protein nanowires. “We turned E. coli into a protein nanowire factory,” he says. “With this new scalable process, protein nanowire supply will no longer be a bottleneck to developing these applications.”
The Air-gen discovery reflects an unusual interdisciplinary collaboration, they say. Lovley discovered the Geobacter microbe in the mud of the Potomac River more than 30 years ago. His lab later discovered its ability to produce electrically conductive protein nanowires. Before coming to UMass Amherst, Yao had worked for years at Harvard University, where he engineered electronic devices with silicon nanowires. They joined forces to see if useful electronic devices could be made with the protein nanowires harvested from Geobacter.
Xiaomeng Liu, a Ph.D. student in Yao’s lab, was developing sensor devices when he noticed something unexpected. He recalls, “I saw that when the nanowires were contacted with electrodes in a specific way the devices generated a current. I found that that exposure to atmospheric humidity was essential and that protein nanowires adsorbed water, producing a voltage gradient across the device.”
abstract Harvesting energy from the environment offers the promise of clean power for self-sustained systems30,31. Known technologies—such as solar cells, thermoelectric devices and mechanical generators—have specific environmental requirements that restrict where they can be deployed and limit their potential for continuous energy production3,4,5. The ubiquity of atmospheric moisture offers an alternative. However, existing moisture-based energy-harvesting technologies can produce only intermittent, brief (shorter than 50 seconds) bursts of power in the ambient environment, owing to the lack of a sustained conversion mechanism6,7,8,9,10,11,12. Here we show that thin-film devices made from nanometre-scale protein wires harvested from the microbe Geobacter sulfurreducens can generate continuous electric power in the ambient environment. The devices produce a sustained voltage of around 0.5 volts across a 7-micrometre-thick film, with a current density of around 17 microamperes per square centimetre. We find the driving force behind this energy generation to be a self-maintained moisture gradient that forms within the film when the film is exposed to the humidity that is naturally present in air. Connecting several devices linearly scales up the voltage and current to power electronics. Our results demonstrate the feasibility of a continuous energy-harvesting strategy that is less restricted by location or environmental conditions than other sustainable approaches.
needle-like structures discovered on positively charged lightning branches
b. m. hare et al. 2019
http://dx.doi.org/10.1038/s41586-019-1086-6
In contrast to popular belief, lightning often does strike twice, but the reason why a lightning channel is 'reused' has remained a mystery. Now, an international research team led by the University of Groningen has used the LOFAR radio telescope to study the development of lightning flashes in unprecedented detail. Their work reveals that the negative charges inside a thundercloud are not discharged all in a single flash, but are in part stored alongside the leader channel at Interruptions. This occurs inside structures which the researchers have called needles. Through these needles, a negative charge may cause a repeated discharge to the ground. The results were published on 18 April in the science journal Nature.
Needles
"This finding is in sharp contrast to the present picture, in which the charge flows along plasma channels directly from one part of the cloud to another, or to the ground," explains Olaf Scholten, Professor of Physics at the KVI-CART institute of the University of Groningen. The reason why the needles have never been seen before lies in the 'supreme capabilities' of LOFAR, adds his colleague Dr Brian Hare, first author of the paper: "These needles can have a length of 100 meters and a diameter of less than five meters, and are too small and too short-lived for other lightning detections systems."
Low Frequency Array (LOFAR) is a Dutch radio telescope consisting of thousands of rather simple antennas spread out over Northern Europe. These antennas are connected with a central computer through fiber-optic cables, which means that they can operate as a single entity. LOFAR is developed primarily for radio astronomy observations, but the frequency range of the antennas also makes it suitable for lightning research, as discharges produce bursts in the VHF (very high frequency) radio band.
Inside the cloud
For the present lightning observations, the scientists have used only the Dutch LOFAR stations, which cover an area of 3,200 square kilometers. This new study analyzed the raw time-traces (which are accurate to one nanosecond) as measured in the 30-80 MHz band. Brian Hare: "These data allow us to detect lightning propagation at a scale where, for the first time, we can distinguish the primary processes. Furthermore, the use of radio waves allows us to look inside the thundercloud, where most of the lightning resides."
Lightning occurs when strong updrafts generate a kind of static electricity in large cumulonimbus clouds. Parts of the cloud become positively charged and others negatively. When this charge separation is large enough, a violent discharge happens, which we know as lightning. Such a discharge starts with a plasma, a small area of ionized air hot enough to be electrically conductive. This small area grows into a forked plasma channel that can reach lengths of several kilometers. The positive tips of the plasma channel collect negative charges from the cloud, which pass through the channel to the negative tip, where the charge is discharged. It was already known that a large amount of VHF emissions is produced at the growing tips of the negative channels while the positive channels show emissions only along the channel, not at the tip.
A new algorithm
The scientists developed a new algorithm for LOFAR data, allowing them to visualize the VHF radio emissions from two lightning flashes. The antenna array and the very precise time stamp on all the data allowed them to pinpoint the emission sources with unprecedented resolution. "Close to the core area of LOFAR, where the antenna density is highest, the spatial accuracy was about one meter," says Professor Scholten. Furthermore, the data obtained was capable of localizing 10 times more VHF sources than other three-dimensional imaging systems, with a temporal resolution in the range of nanoseconds. This resulted in a high-resolution 3D image of the lightning discharge.
Break
The results clearly show the occurrence of a break in the discharge channel, at a location where needles are formed. These appear to discharge negative charges from the main channel, which subsequently re-enter the cloud. The reduction of charges in the channel causes the break. However, once the charge in the cloud becomes high enough again, the flow through the channel is restored, leading to a second discharge of lightning. By this mechanism, lightning will strike in the same area repeatedly.
Scholten: "The VHF emissions along the positive channel are due to rather regularly repeated discharges along previously formed side channels, the needles. These needles appear to drain the charges in a pulsed manner." This is a totally new phenomenon, adds Professor Joe Dwyer of the University of New Hampshire (US), third author of the paper: "Our new observation techniques show copious amounts of needles in the lightning flash, which have not been seen before." And Brian Hare concludes: "From these observations, we see that a part of the cloud is re-charged, and we can understand why a lightning discharge to the ground may repeat itself a few times."
abstract Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends—called positive and negative leaders1. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30–300-megahertz frequency band2,3,4,5,6,7,8 that can be remotely sensed and imaged with high spatial and temporal resolution9,10,11. Positive leaders propagate more continuously and thus emit very little high-frequency radiation12. Radio emission from positive leaders has nevertheless been mapped13,14,15, and exhibits a pattern that is different from that of negative leaders11,12,13,16,17. Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders9,12,16,18,19,20, which may lead to current pulses that both reconnect positive leaders to negative leaders11,16,17,20,21,22 and cause multiple cloud-to-ground lightning events1. The disconnection process is thought to be due to negative differential resistance18, but this does not explain why the disconnections form primarily on positive leaders22, or why the current in cloud-to-ground lightning never goes to zero23. Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures—which we call ‘needles’—that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.
vanadium disulfide flakes with nanolayered titanium disulfide coating as cathode materials in lithium-ion batteries
lu li et al. 2019
http://dx.doi.org/10.1038/s41467-019-09400-w
A lithium-ion battery charges and discharges as lithium ions move between two electrodes, called an anode and a cathode. In a traditional lithium-ion battery, the anode is made of graphite, while the cathode is composed of lithium cobalt oxide.
These materials perform well together, which is why lithium-ion batteries have become increasingly popular, but researchers at Rensselaer believe the function can be enhanced further.
"The way to make batteries better is to improve the materials used for the electrodes," said Nikhil Koratkar, professor of mechanical, aerospace, and nuclear engineering at Rensselaer, and corresponding author of the paper. "What we are trying to do is make lithium-ion technology even better in performance."
Koratkar's extensive research into nanotechnology and energy storage has placed him among the most highly cited researchers in the world. In this most recent work, Koratkar and his team improved performance by substituting cobalt oxide with vanadium disulfide (VS2).
"It gives you higher energy density, because it's light. And it gives you faster charging capability, because it's highly conductive. From those points of view, we were attracted to this material," said Koratkar, who is also a professor in the Department of Materials Science and Engineering.
Excitement surrounding the potential of VS2 has been growing in recent years, but until now, Koratkar said, researchers had been challenged by its instability -- a characteristic that would lead to short battery life. The Rensselaer researchers not only established why that instability was happening, but also developed a way to combat it.
The team, which also included Vincent Meunier, head of the Department of Physics, Applied Physics, and Astronomy, and others, determined that lithium insertion caused an asymmetry in the spacing between vanadium atoms, known as Peierls distortion, which was responsible for the breakup of the VS2 flakes. They discovered that covering the flakes with a nanolayered coating of titanium disulfide (TiS2) -- a material that does not Peierls distort -- would stabilize the VS2 flakes and improve their performance within the battery.
"This was new. People hadn't realized this was the underlying cause," Koratkar said. "The TiS2 coating acts as a buffer layer. It holds the VS2 material together, providing mechanical support."
Once that problem was solved, the team found that the VS2-TiS2 electrodes could operate at a high specific capacity, or store a lot of charge per unit mass. Koratkar said that vanadium and sulfur's small size and weight allow them to deliver a high capacity and energy density. Their small size would also contribute to a compact battery.
When charging was done more quickly, Koratkar said, the capacity didn't dip as significantly as it often does with other electrodes. The electrodes were able to maintain a reasonable capacity because, unlike cobalt oxide, the VS2-TiS2 material is electrically conductive.
Koratkar sees multiple applications for this discovery in improving car batteries, power for portable electronics, and solar energy storage where high capacity is important, but increased charging speed would also be attractive.
power of internal martial arts & chi combat & energy secrets of ba gua tai chi & hsing i
bruce frantzis 1998 9781583941904
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thomas sherman 2018
the biological foundations of organizational behavior
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karate science: dynamic movement
j. d. swanson 2017
burn out: the endgame for fossil fuels
dieter helm 2017
earth-shattering events: earthquakes, nations, and civilization
andrew robinson 2016
