By Marlene Cimons
When the conversation turns to sources of clean renewable energy, evaporation usually isn't the first thing to come up, if at all.
Yet scientists think evaporation from U.S. lakes and reservoirs could generate almost 70 percent of the power the nation produces now. Even better, it could meet demand both day and night, solving the intermittency problems posed by solar and wind.
"Evaporation occurs day and night, all year round," said Ahmet-Hamdi Cavusoglu, a graduate student at Columbia University and lead author of a new study published in the journal Nature Communications that calculated the possible future impact of evaporation as a renewable energy source. "By controlling evaporation, we can store and control the power output, allowing us to potentially provide reliable energy on demand without needing batteries and other energy storage methods."
The evaporation engine sits on a shallow pool of blue water. When water on the surface below evaporates, it drives the flaps to move back and forth. When connected to a generator, that motion produces electricity. Xi Chen
Ozgur Sahin, a biophysicist at Columbia and the paper's senior author, has developed technology that uses spores from the harmless soil-dwelling bacterium B. subtilis to absorb and release water when the relative humidity of the surrounding air changes. At high humidity, the spores take in water and expand, and at low humidity they release water and contract. "In this process, they act like a muscle," he said. "They are highly effective muscles, and it is possible to assemble spores into larger materials that move and generate force when humidity levels change."
The machine, developed by Sahin's lab, controls humidity with shutters that open and close, prompting the spore-coated plastic strips to expand and contract. "When the shutters are closed, evaporation from the water surface raises the humidity level below the shutters, causing spore-coated strips to elongate," he explained. "The movement of the strip opens the shutters, which reduces humidity levels by letting moisture out. The cycle reaches completion when spore-coated strips shorten and close the shutters. Because the process is cyclical, the spore-coated strips repeatedly elongate and shorten."
The moving end of the strips is connected to a generator, which produces the electricity. "We have the technology to harness energy from wind, water and the sun, but evaporation is just as powerful," Sahin said. "We can now put a number on its potential."
The evaporation engine sits on a shallow pool of blue-colored water. When water on the surface below evaporates, it drives the flaps to move back and forth. When connected to a generator, that motion produces electricity. Sahin Laboratory
The technology also has the potential to save water. The study estimated that half of the water that evaporates naturally from lakes and reservoirs into the atmosphere could be conserved during the process, amounting to around 25 trillion gallons annually, or about a fifth of the water Americans consume.
Sahin added that conserving that much water would have little impact on weather patterns. Even if it were deployed at a large scale, his technology would not meaningfully reduce atmospheric moisture that later results in heavy rain because "precipitation and moisture is mostly imposed by the ocean," he said.
Klaus Lackner, an Arizona State University physicist not involved in the study, is developing artificial trees that draw carbon dioxide from the air, in part by using evaporation. "Evaporation has the potential to do a lot of work," Lackner said. "It's nice to see that drying and wetting cycles can also be used to collect mechanical energy."
In computing the potential output of evaporation, the authors confined their calculations to the U.S., where weather station data are readily available, and excluded areas such as farmland, rivers, the Great Lakes and coastlines to avoid errors associated with modeling more complex interactions.
To be sure, the researchers' work is still experimental and confined to the lab. However, "if the technology can be made efficient and scaled to the size of a football field, then widespread use of evaporation as an energy source could be possible," Sahin said. "There are many such bodies of water used by farmers, municipalities and water management agencies," which could provide sources of evaporation in addition to natural bodies of water. Moreover, since many of the materials used are biological and can be easily grown, the machinery likely would not be very expensive, he added.
One of its major advantages is the ability to produce power only when needed. Solar and wind, on the other hand, require backup batteries when the sun isn't shining or the wind isn't blowing. Moreover, batteries aren't cheap, and they often are made of toxic materials.
Harvesting energy from evaporation can cut the amount of water lost to natural evaporation in half, researchers say. Water-strapped cities with growing populations and energy needs could benefit most, including Phoenix, which is served by the reservoir pictured above.Central Arizona Project
"Human electricity demand varies seasonally and daily," Cavusoglu said. "We use more energy during the summer, and we use more energy in the early evening when people get home from work. However, the availability of wind and solar power does not match our demand. This need for energy on demand is important for our daily life, from keeping the lights on in hospitals to letting us stream Netflix at home."
Since evaporation packs more energy in warm and dry weather, drought-prone states like California, Nevada and Arizona could benefit greatly from the technology. "Interestingly, many dry-air areas do have some lakes or large bodies of water," Sahin said. "For example, the Colorado River and the large lakes formed by dams, such as Lake Mead, Lake Mohave, Lake Powell and Lake Havusu."
Still, "if there are no water bodies or other wet surfaces, evaporation will be negligible and this concept will not work," he added. "However, even in that situation, daily variations in relative humidity could be harnessed to generate power."
This turbine engine rotates as water evaporates from the wet paper lining the walls of the engine.Sahin Laboratory
Several years ago, Sahin's lab also developed an evaporation-fueled piston-driven engine that generates electricity causing a light to flash, and a rotary engine that drives a miniature car. The scientists now are working on improving the energy efficiency of their materials, and plan to test their concept on a lake, reservoir, or greenhouse where the technology could both conserve water and create power.
"Today, further expansion of renewable energy technologies faces many technical and non-technical challenges," Sahin said. "A renewable energy technology based on evaporation could nicely complement the existing ones by offering an alternative that might be more suitable in a particular location, or generate power when the other renewable energy technologies can't."
Reposted with permission from our media associate Nexus Media.
EcoWatch Daily Newsletter
By Tiffany Means
Summer and fall are great seasons to enjoy the outdoors. But if you're already spending extra time outside because of the COVID-19 pandemic, you may be out of ideas on how to make fresh-air activities feel special. Here are a few suggestions to keep both adults and children entertained and educated in the months ahead, many of which can be done from the comfort of one's home or backyard.
The coronavirus may linger in the air in crowded indoor spaces, spreading from one person to the next, the World Health Organization acknowledged on Thursday, as The New York Times reported. The announcement came just days after 239 scientists wrote a letter urging the WHO to consider that the novel coronavirus is lingering in indoor spaces and infecting people, as EcoWatch reported.
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By Julia Vergin
It is undisputed that vitamin D plays a role everywhere in the body and performs important functions. A severe vitamin D deficiency, which can occur at a level of 12 nanograms per milliliter of blood or less, leads to severe and painful bone deformations known as rickets in infants and young children and osteomalacia in adults. Unfortunately, this is where the scientific consensus ends.
Where Does the Deficiency Begin?<p>Nobody knows exactly how much vitamin D a person actually needs. The question of when a deficiency starts is correspondingly controversial. However, vitamin D is becoming increasingly popular.Not only is the pseudo-scientific literature on the "sun vitamin" experiencing an upswing, but the number of published studies has also increased enormously in recent years. For example, in 2019 <a href="https://academic.oup.com/edrv/article/40/4/1109/5126915" target="_blank">a study found that</a> Vitamin D is responsible for keeping the skeleton functional and is associated with cardiovascular diseases, type 2 diabetes and various types of cancer. <br></p>
An All-Rounder<p>Vitamin D levels in the body rise and fall according to sun exposure. If sufficient UV rays reach the skin, the body is able to produce the vitamin itself. However, the human body only derives an estimated 10 to 20 percent of its daily requirement from food.</p><p>The vitamin D that we synthesize from sunlight or food is not biologically active at first. Before the kidneys can produce the biologically active form of the vitamin, known as calcitriol, and release it into the blood, some metabolic processes must take place beforehand.</p><p>In addition, many organs have receptors to which the precursor of calcitriol binds. Further, this substance is also present in blood.</p><p>From this precursor, the organs then produce calcitriol themselves, which the body then uses for countless other processes in the body. This form of vitamin D thus regulates insulin secretion, inhibits tumor growth, and promotes the formation of red blood cells as well as the survival and activity of macrophages, which are important for the <a href="https://www.mdpi.com/2072-6643/5/7/2502/htm" target="_blank">immune system.</a></p>
Low Vitamin D, Severe COVID-19 Disease?<p>A research study carried out <a href="https://www.sciencedirect.com/science/article/pii/S2352364620300067?via%3Dihub" target="_blank">at the University of Hohenheim</a> has now established a link between vitamin D deficiency, certain previous diseases, and severe cases of COVID-19.</p><p>According to the study, "there is a lot of evidence that several non-communicable diseases (high blood pressure, diabetes, cardiovascular diseases, metabolic syndrome) are associated with low vitamin D plasma levels. These comorbidities, together with the often accompanying vitamin D deficiency, increase the risk of severe COVID-19 events."</p><p>"This statement is completely correct," said Martin Fassnacht, head of endocrinology at the University Hospital of Würzburg. However, he qualifies that it is a pure association, "i.e. a mere observation that these events occur together.</p><p>Dr. Fassnacht is very critical of the hype surrounding vitamin D, but not because he denies the vitamin serves important functions. However, studies on humans have not been able to show that vitamin D has the healing powers many often propagate.</p><p>Fassnacht says, "If you take a closer look, the hopes that the administration of vitamin D has a healing effect have not been confirmed so far."</p>
Association Versus Intervention Studies<p>Many studies on the vitamin are association or observational studies. "By definition, these studies cannot prove the causal relationship, but only point to mere correlations," said Fassnacht. The physician tries to illustrate this with an example:</p><p>"Imagine two groups of 80-year-olds. One group is spry, active and does sports. If you compare them with another group living in nursing homes, the difference in vitamin D levels will be dramatic. Life expectancy would also be extremely different."</p><p>But to try to explain the difference in fitness by vitamin D status alone is far too simplistic. "Vitamin D levels are a good measure of how sick someone is. But not more," says Fassnacht. </p><p>According to Fassnacht, none of the intervention studies carried out to date -- that specifically examined the effect of vitamin D on various diseases -- has been able to confirm the previous association and laboratory studies or the presumed positive effect of vitamin D.</p>
Further Research Is Needed<p>"If a coronavirus infection is suspected, it is therefore absolutely necessary to check the vitamin D status and quickly correct any possible deficit," said the recommendation of the paper published by the University of Hohenheim.</p><p>"Studies are underway to see whether vitamin D helps in COVID-19 infection, but I personally do not believe that this is really the case," says endocrinologist Fassnacht. Nevertheless, he says it is of course useful to carry out these studies.<br></p><p>"I don't want to rule out that there are actually subgroups of people who benefit from an additional vitamin D dose," he says. After all, this has been proven to be the case with a severe deficit.</p><p>In view of the study situation, Fassnacht does not think much of preventive, nationwide vitamin D substitutes. "My belief that the vitamin helps somewhere is very low. But, of course, I can be wrong."</p>
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Ocean scientists have been busy creating a global network to understand and measure changes in ocean life. The system will aggregate data from the oceans, climate and human activity to better inform sustainable marine management practices.
EcoWatch sat down with some of the scientists spearheading the collaboration to learn more.
Climate models are predicting faster warming of the North Atlantic Ocean, which will shift the Gulf Stream. NASA
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By Jessica Corbett
As a United Nations agency released new climate projections showing that the world is on track in the next five years to hit or surpass a key limit of the Paris agreement, authors of a new study warned Thursday that increasing carbon dioxide in the atmosphere is nearing a level not seen in 15 million years.
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