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New membrane enables us to harvest 'osmotic' energy from water
You've likely heard of solar energy, but what is osmotic energy?
- Osmotic power plants harvest energy from the difference in pressure or salinity between salt and freshwater using a semi-permeable membrane.
- One of the major challenges for this kind of renewable energy, however, has been developing effective and durable membranes.
- Now, new research demonstrates a durable and effective membrane that could significantly improve osmotic energy collection.
By now, everybody has heard of solar and wind energy. You're probably familiar with hydroelectric energy as well, and maybe even geothermal energy. But few are familiar with osmotic energy.
Osmotic energy plants are fairly rare as one of the key components in their use — a semi-permeable membrane — tends to break down, requiring frequent replacement and driving up operational costs. Now, new research has uncovered a better, more durable membrane that may lead to significantly better returns for this kind of renewable energy.
What exactly is osmotic energy?
An image taken inside of the world's first osmotic power plant at Tofte, Norway, 2009. The project has since been shelved due to its high operating costs, highlighting the need for better, more efficient technology.
POPPE, CORNELIUS/AFP via Getty Images
Osmotic energy takes advantage of the differences in pressure and salinity between fresh and seawater to generate electricity. Its only waste product is brackish water, which is simply water that is saltier than freshwater but less so than seawater. While it doesn't generate large amounts of energy compared to other renewable energy sources, it is remarkably consistent. The energy derived from wind turbines and solar panels fluctuates tremendously with the weather, time, and local climate, but osmotic energy works more or less the same year-round wherever fresh and saltwater meet.
Osmosis, in general, is the process by which liquid moves from a dilute to a concentrated solution through a semi-permeable membrane. It occurs in your body all the time, as its critical for fundamental biological processes.
Osmotic power plants typically use one of two major techniques. In pressure-retarded osmosis (PRO), freshwater is gathered in one tank while saltwater is kept in another. In between, a membrane separates the two. This membrane has special properties that only permit freshwater to pass through, but not saltwater. As a result, the freshwater is drawn through the membrane, diluting the saltwater in the corresponding tank but also raising the pressure. From this pressure, we can derive energy.
The other technique, reverse electrodialysis osmosis (RED), takes advantage of the fact that saltwater contains more positive and negative ions than fresh water. Normally, these ions would travel into the freshwater, balancing out the solution. But when harvesting osmotic energy, a membrane can selectively allow only the positive or negative ions to pass through, turning tanks of salt and fresh water into a kind of battery that passively generates electricity.
Inspired by bone and cartilage
But the reason why we don't see more of either of these plants is because of the membrane. Osmotic membranes are delicate and must retain specific characteristics in order to remain semi-permeable. Exposed to the elements, they tend to degrade over time.
Recent research described in the journal Joule presents a new, durable membrane inspired by bone and cartilage that lasts. This membrane would be used in RED applications.
Bone is a very strong material, but it doesn't permit the transportation of ions, while flimsier material like cartilage permits ions to pass through easily. A membrane for osmotic energy would require both strength and the ability to transport ions.
Using this as inspiration, the researchers developed a membrane consisting of layers of boron nitride and aramid nanofibers. Boron nitride had shown promise in previous membranes but tended to develop cracks over time. To address this, the researchers investigated the use of a class of synthetic fibers frequently used in Kevlar: Aramid nanofibers. By layering boron nitride and the aramid nanofibers, the researchers had developed a material that was sturdy enough to last while remaining flexible and efficient in transporting ions.
The researchers found that not only does this generate power to a similar degree as commercial RED osmotic power plants, but it also performs for a remarkably long time. They cycled the membrane 20 times, observing its efficiency over the course of 200 hours, and found no drop in performance whatsoever.
Moreover, the membrane can function well in a wide range of pH and temperatures. Other membranes only perform well under specific conditions and need to be regularly replaced, increasing the amount of energy they require to be maintained. Implementing a more durable, longer-lasting membrane in a power plant would mean in effect that the plant could generate more power, as it would require less energy to maintain.
While the study only served as a proof of concept, it does show that we're getting better and better at addressing the problems with renewable energy. Not only that, but it highlights how much energy available to us is out there — so long as we're willing to think creatively and look in the right places. With any luck, we might start to see more osmotic energy plants operating at the mouths of the world's rivers.
A Mercury-bound spacecraft's noisy flyby of our home planet.
- There is no sound in space, but if there was, this is what it might sound like passing by Earth.
- A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
- Yes, in space no one can hear you scream, but this is still some chill stuff.
First off, let's be clear what we mean by "hear" here. (Here, here!)
Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.
All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.
Image source: European Space Agency
The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.
Into and out of Earth's shadow
In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.
The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."
In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."
When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.
The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.
BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.
MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.
Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.
Research suggests that aging affects a brain circuit critical for learning and decision-making.
As people age, they often lose their motivation to learn new things or engage in everyday activities. In a study of mice, MIT neuroscientists have now identified a brain circuit that is critical for maintaining this kind of motivation.
Why not just divide the United States in slices of equal population?
- Slicing up the country in 10 strips of equal population produces two bizarre maps.
- Seattle is the biggest city in the emptiest longitudinal band, San Antonio rules the largest north-south slice.
- Curiously, six cities are the 'capitals' of both their horizontal and vertical deciles.
Sweeping re-alignments<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYwMTAwOC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYyMzU3ODA1NH0.u_5xakBvkYwgPtiwLU3z-1e082hBeqwS4Rl1uiJqdF4/img.png?width=980" id="23ff1" class="rm-shortcode" data-rm-shortcode-id="24a5b6ec251a11f3ed7aaefc205dde17" data-rm-shortcode-name="rebelmouse-image" alt="Printed in March 1812, this political cartoon was drawn in reaction to the newly drawn state senate election district of South Essex created by the Massachusetts legislature to favor the Democratic-Republican Party candidates of Governor Elbridge Gerry over the Federalists. The caricature satirizes the bizarre shape of a district in Essex County, Massachusetts, as a dragon-like "monster". Federalist newspaper editors and others at the time likened the district shape to a salamander, and the word gerrymander was a portmanteau of that word and Governor Gerry's last name." />
The original cartoon of the 'Gerry-Mander', published in 1812 in the Boston Centinel.
Image: Elkanah Tisdale (1771-1835), Public Domain.<p>One way for a political party to manipulate the outcome of elections is to 'gerrymander' electoral districts: manipulate their boundaries to increase the likelihood of a favorable outcome (see also #<a href="https://bigthink.com/strange-maps/53-ever-been-ger..." target="_blank">53</a>).</p><p><span></span>The term is almost as old as the United States itself, and the practice continues to disfigure the electoral map to this day. Perhaps these maps can serve as the inspiration for a radical solution. </p><p><span></span>They show the contiguous United States (i.e. without Alaska and Hawaii) sliced latitudinally and longitudinally into ten straight-bordered bands of varying size, so that each contains exactly 10 percent of the population. </p><p><span></span>Although certainly not intended as a reflection on electoral redistricting, it's tempting to see these sweeping re-alignments of the U.S. as a suggestion with some potential in that direction. </p>
United Strips of America<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYwMTA4MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzE1MjQ1MX0.WpISo-g15B5O3qXbHXHf-7lQtAainpO7zPuizXWFOGs/img.jpg?width=980" id="d6656" class="rm-shortcode" data-rm-shortcode-id="72ed7c905283f9979ec0f82d451ad261" data-rm-shortcode-name="rebelmouse-image" alt="Reddit user curiouskip used U.S. Census population data to divide the 'Lower 48' into deciles (ten equal parts), each representing about 30.8 million people. Each decile is consigned its most populous city as 'capital'." />
The contiguous United States, divided into horizontal and vertical deciles.
Image: u/curiouskip, reproduced with kind permission.<p>Reddit user curiouskip used U.S. Census population data to divide the 'Lower 48' into deciles (ten equal parts), each representing about 30.8 million people. Each decile is consigned its most populous city as 'capital'.</p><p><span></span>Looking at the top map, which divides the U.S. into 10 longitudinal strips, we see</p><ul><li>Seattle rules the northernmost slice of territory. It is the broadest, and therefore also the emptiest one.</li><li>The Chicago, Omaha, New York City and Indianapolis strips complete the northern half of the country. And indeed: 50 percent of the population occupies roughly one half of the country, from north to south.</li><li>The dividing line between the top and bottom halves of the country runs from just north of the San Francisco Bay to halfway across the Delmarva Peninsula.</li><li>Capital cities of the southern strips are San Jose, Charlotte, Los Angeles, San Diego, and Houston.</li><li>The Houston Strip is divided into two non-contiguous areas. Florida maintains its panhandle, albeit much reduced. </li></ul><p>The bottom map shows the U.S. divided latitudinally into 10 bands of equal population. </p><ul><li>San Jose and Los Angeles both retain their capital status, this time of the two westernmost strips.</li><li>San Antonio is the main city of the Big Empty, more than twice as wide as the second-broadest band.</li><li>The dividing line between America's eastern and western half, population-wise, is far off-center: it skirts the eastern edge of Chicago, making the western half much bigger than the eastern one.</li><li>Houston, Chicago, and Indianapolis also remain the largest cities in their respective bands.</li><li>Further east, Jacksonville and Philadelphia get to rule over their strip of America, while Charlotte and New York City keep winning, both vertically and horizontally.</li></ul><p>Redistricting a country into zones of equal population – and that being your only criterium – will create districts that are randomly diverse, and perhaps also, at least in this case, unmanageably large. </p><p>However, mixing up the political map with a bunch of straight lines as the only instrument is something that has been considered before. Usually, the objective is the wholesale removal of age-old divisions. <br></p>
Perfectly square departments<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYwMTEzOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwOTQyMzIwOH0.kYuf58g0bjsPL9DGPq5PycZ7PDJMnItT0rfrPonOP3k/img.jpg?width=980" id="89a68" class="rm-shortcode" data-rm-shortcode-id="5b81a43e785997bb1f11f72548659a9f" data-rm-shortcode-name="rebelmouse-image" alt="\u200bCh\u00e2ssis figuratif du territoire de la France partag\u00e9 en divisions \u00e9gales entre elles, proposition annex\u00e9e au rapport du 29 septembre 1789 \u00e0 l'Assembl\u00e9e nationale de la commission dite Siey\u00e8s-Thouret" />
France divided into 80-odd geometrical departments: failed proposal by Jacques-Guillaume Thouret (1790).
Image: Centre historique des Archives nationales – Atelier de photographie; public domain.
European Pie<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYwMTQ0Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTE5NDE3OX0.dPcY1tkO7nwkx6IX98Sleh7AmBpDnwlcJLfC_Z-WBlY/img.jpg?width=980" id="b35d7" class="rm-shortcode" data-rm-shortcode-id="84509a9425e13c0dd8fbe00df28a197e" data-rm-shortcode-name="rebelmouse-image" />
In this rather outlandish proposal, continental Europe's 24 cantons center on Vienna.
Image: PJ Mode Collection of Persuasive Maps, Cornell University.<p>And in 1920, an anonymous author – possibly the Austrian P.A. Maas – proposed slicing up Post-World-War-I Europe as a pie, into 24 slices that would center on Vienna's St. Stephen's Cathedral. Each of those slices would be made up of a wide and random variety of linguistic, ethnic, and religious groups – and that would be the point: the better to unite them all into one massive superstate (see also #<a href="https://bigthink.com/strange-maps/a-bizarre-peace-proposal-slice-europe-up-like-a-pie" target="_blank">851</a>).</p><p>Needless to say, both plans never left the drawing board. Would a proposal for the longitudinal and/or latitudinal redistricting of the U.S. have more traction? <br></p>
Coast-to-coast precedents<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYwMTIwOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDM2OTE0OX0.52UjcA_YD9Y9UB9_hoSctI_xBrRDALZ2DRLkIo9a8RM/img.jpg?width=980" id="10784" class="rm-shortcode" data-rm-shortcode-id="1999808ea21e11162fdb9181c3912753" data-rm-shortcode-name="rebelmouse-image" alt="Illustration of the Connecticut Charter boundary, 1662" />
Putting the 'connect' into Connecticut: the Nutmeg State extending from the Pacific to the Atlantic.
Image: Connecticuthistory.org<p>Well, for one, coast-to-coast polities have some pedigree in America's past: some of the first colonies had claims that extended from the Atlantic all the way to the Pacific. </p><p>If history had gone entirely the way Connecticut would have wanted, the state would include such inland cities as Detroit, Chicago, and Salt Lake City, and extended to what is now the northern part of California.</p><p>Is such geopolitical weirdness reasonable or feasible today? Absolutely not. But in its randomness, would it be it as unfair as gerrymandering? </p><p><em><br></em></p><p><em>Decile maps of the contiguous United States reproduced with kind permission by u/curiouskip; found <a href="https://www.reddit.com/r/dataisbeautiful/comments/ijyn7p/oc_us_population_deciles_by_latitude_and_longitude/" target="_blank">here</a> on <a href="https://www.reddit.com/" target="_blank">Reddit</a>.<br></em></p><p><strong>Strange Maps #1054</strong></p><p><em>Got a strange map? Let me know at </em><a href="mailto:firstname.lastname@example.org">email@example.com</a><em>.</em></p>