from the world's big
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.
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Construction of the $500 billion dollar tech city-state of the future is moving ahead.
- The futuristic megacity Neom is being built in Saudi Arabia.
- The city will be fully automated, leading in health, education and quality of life.
- It will feature an artificial moon, cloud seeding, robotic gladiators and flying taxis.
The Red Sea area where Neom will be built:
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Frequent shopping for single items adds to our carbon footprint.
- A new study shows e-commerce sites like Amazon leave larger greenhouse gas footprints than retail stores.
- Ordering online from retail stores has an even smaller footprint than going to the store yourself.
- Greening efforts by major e-commerce sites won't curb wasteful consumer habits. Consolidating online orders can make a difference.
A pile of recycled cardboard sits on the ground at Recology's Recycle Central on January 4, 2018 in San Francisco, California.
Photo by Justin Sullivan/Getty Images<p>A large part of the reason is speed. In a competitive market, pure players use the equation, <em>speed + convenience</em>, to drive adoption. This is especially relevant to the "last mile" GHG footprint: the distance between the distribution center and the consumer.</p><p>Interestingly, the smallest GHG footprint occurs when you order directly from a physical store—even smaller than going there yourself. Pure players, such as Amazon, are the greatest offenders. Variables like geographic location matter; the team looked at shopping in the UK, the US, China, and the Netherlands. </p><p>Sadegh Shahmohammadi, a PhD student at the Netherlands' Radboud University and corresponding author of the paper, <a href="https://www.cnn.com/2020/02/26/tech/greenhouse-gas-emissions-retail/index.html" target="_blank">says</a> the above "pattern holds true in countries where people mostly drive. It really depends on the country and consumer behavior there."</p><p>The researchers write that this year-and-a-half long study pushes back on previous research that claims online shopping to be better in terms of GHG footprints.</p><p style="margin-left: 20px;">"They have, however, compared the GHG emissions per shopping event and did not consider the link between the retail channels and the basket size, which leads to a different conclusion than that of the current study."</p><p>Online retail is where convenience trumps environment: people tend to order one item at a time when shopping on pure player sites, whereas they stock up on multiple items when visiting a store. Consumers will sometimes order a number of separate items over the course of a week rather than making one trip to purchase everything they need. </p><p>While greening efforts by online retailers are important, until a shift in consumer attitude changes, the current carbon footprint will be a hard obstacle to overcome. Amazon is trying to have it both ways—carbon-free and convenience addicted—and the math isn't adding up. If you need to order things, do it online, but try to consolidate your purchases as much as possible.</p><p>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>
Building a personal connection with students can counteract some negative side effects of remote learning.
- Not being able to engage with students in-person due to the pandemic has presented several new challenges for educators, both technical and social. Digital tools have changed the way we all think about learning, but George Couros argues that more needs to be done to make up for what has been lost during "emergency remote teaching."
- One interesting way he has seen to bridge that gap and strengthen teacher-student and student-student relationships is through an event called Identity Day. Giving students the opportunity to share something they are passionate about makes them feel more connected and gets them involved in their education.
- "My hope is that we take these skills and these abilities we're developing through this process and we actually become so much better for our kids when we get back to our face-to-face setting," Couros says. He adds that while no one can predict the future, we can all do our part to adapt to it.
Chronic irregular sleep in children was associated with psychotic experiences in adolescence, according to a recent study out of the University of Birmingham's School of Psychology.