evaporation

Harvesting Fresh Water From Ocean Air | Earth Wise

January 19, 2023 By EarthWise Leave a Comment

Roughly three-quarters of the world population has access to a safely managed water source. That means that one-in-four people do not have access to safe drinking water. Even in the wealthy United States, persistent drought in the west is creating problems in places like Phoenix, Arizona.

Water is plentiful on Earth but more than 99% of it is unusable by humans and many other living things because it is saline, frozen, or inaccessible. Only about 0.3% of our fresh water is found in the surface water of lakes, rivers, and swamps.

There is an almost limitless supply of fresh water in the form of water vapor above the oceans, but this source is untapped. Researchers at the University of Illinois have been evaluating the feasibility of a hypothetical structure capable of capturing water vapor from above the ocean and condensing it into fresh water.

Existing ways to obtain fresh water like wastewater recycling, cloud seeding, and desalination have met only limited success and present various problems with regard to cost, environmental impact, and scalability.

The researchers have proposed hypothetical large offshore structures measuring 700 feet by 300 feet to capture water vapor that is continually evaporating from the ocean in subtropical regions. Their modeling concluded that such structures could provide fresh water for large population centers in the subtropics. Furthermore, climate projections show that the amount of water vapor over the oceans will only increase over time, providing even more fresh water supply.

This is only a theoretical study at this point, but the researchers believe it opens the door for novel infrastructure investments that could address global water scarcity.

**********

Web Links

Researchers propose new structures to harvest untapped source of fresh water

Photo, posted June 28, 2009, courtesy of Nicolas Raymond via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Lithium Mining And Andes Ecosystems | Earth Wise

October 28, 2022 By EarthWise Leave a Comment

A remote region in the high Andes straddling the borders between Argentina, Bolivia, and Chile has become known as the Lithium Triangle. The area has become the focus of a global rush for lithium to make batteries for electric cars. The global demand for lithium is expected to quadruple by 2030 to 2.6 million tons a year.

According to the U.S. Geological Survey, more than half of the world’s lithium reserves are dissolved in ancient underground water within the Lithium Triangle. The cheapest way to extract the lithium is to pump the underground water to the surface and evaporate it in the sun to concentrate the lithium carbonate contained in it.

Every ton of lithium carbonate extracted using this cheap, low-tech method dissipates into the air about half a million gallons of water that is vital to the arid high Andes. The process lowers water tables and has the potential to dry up lakes, wetlands, springs, and rivers. Hydrologists and conservationists say the lithium rush in Argentina is likely to turn the region’s delicate ecosystems to deserts.

The global drive for green vehicles to fight climate change has the potential to be an ecological disaster in this remote region of South America and for the indigenous people who live there.

The environmental impacts are not an inevitable price for the transition to electric vehicles. First of all, there are alternatives to lithium. Both zinc and nickel are potential substitutes in rechargeable batteries. But, there are also ways of obtaining lithium that are less destructive than evaporating the metal from saline ecosystems. It is up to battery manufacturers, automakers, and financiers to start demanding lithium from sources that are less environmentally destructive.

**********

Web Links

Why the Rush to Mine Lithium Could Dry Up the High Andes

Photo, posted September 25, 2015, courtesy of Nuno Luciano via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Prospects For Floating Solar | Earth Wise

October 10, 2022 By EarthWise Leave a Comment

Countries are trying to figure out how to get enough energy from solar and wind generation to completely decarbonize their economies. According to some estimates, nations might have to devote between half a percent and five percent of their land area to solar panels to get the job done. Half a percent is about the amount of the U.S. that is covered by paved roads. While there is lots of open land in many parts of the country, covering it with solar panels might not be acceptable to farmers, conservationists, or other interested parties.

One way to deploy more solar panels without using up land is the use of floating solar panels. Floating photovoltaic systems – also known as floatovoltaics – are becoming increasingly common, especially in Asia. This year, China installed one of the largest floatovoltaic systems in the world on a reservoir near the city of Dezhou.

Floating solar panels stay cooler and run more efficiently than those on land. The panels also help prevent evaporation from their watery homes and the shading they provide also help to minimize algal blooms. Solar installations on reservoirs generally puts them near cities, making it easier to feed power into urban grids.

On the other hand, floating solar systems need to be able to withstand water and waves and are generally more expensive to build than land-based systems.

At present, the installed global capacity of floating solar is only about 3 gigawatts, compared with more than 700 gigawatts of land-based systems. However, reservoirs around the world collectively cover an area about the size of France. Covering just 10 percent of them with floating solar could produce as much power as all the fossil-fuel plants in operation worldwide.

**********

Web Links

Solar Takes a Swim

Photo, posted March 7, 2019, courtesy of Hedgerow INC via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Death Valley Flooding | Earth Wise

September 13, 2022 By EarthWise Leave a Comment

Furnace Creek in Death Valley is the driest place in North America. Its average annual rainfall is under two inches. On August 5th, a thousand-year rainfall event dropped 1.46 inches of rain – about three-quarters of a year’s precipitation. The all-time record for a single day is 1.47 inches, set in April 1988. The storm did break the record for the most rain ever recorded in August, which averages just over a tenth of an inch of rain for the entire month.

The flash flood washed debris over roads, swept away and buried cars, knocked a water facility offline, damaged buildings, and stranded about a thousand visitors and staff in Death Valley National Park. By the next day, the flood water had mostly receded, and stranded visitors could be escorted out of the park by National Park personnel.

Death Valley sits at 282 feet below sea level. If it were not for the extremely arid climate there, Death Valley would likely be filled with water. However, humid air masses traveling east from the Pacific Ocean have to cross four mountain ranges before they reach the desert valley. Those air masses lose their moisture in the form of rain on the western slopes of the mountain, leaving a dry area, or rain shadow, on the eastern sides. By the time the air masses reach Death Valley, they are bone dry. On rare occasions, the lowest spot in the valley fills with water forming a wide, shallow lake, known as Lake Badwater.

The extreme heat and aridity of Death Valley evaporates the temporary lake quickly, returning the valley to its usual state. Furnace Creek still holds the record for the highest air temperature ever recorded: 134 degrees Fahrenheit.

**********

Web Links

Death Valley Flash Flooding

Photo, posted April 7, 2021, courtesy of Matthew Dillon via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Floating Solar | Earth Wise

June 7, 2022 By EarthWise 1 Comment

The largest floating solar array in Europe, 12,000 panels sitting on top of the Alqueva Reservoir in Portugal – will come online in July. Installing floating solar arrays, which are sometimes called “floatovoltaics”, produce renewable energy while shielding significant expanses of water from the sun’s heat. These dual benefits have led to floatovoltaic projects in multiple countries around the world.

The city of Cohoes, in New York’s Albany County, has proposed an 8,000-panel floating solar array on the city reservoir. Federal funding of $3 million for the project was obtained by local Congressman Paul Tonko and, in May, utility National Grid donated $750,000 towards the project. Engineering work will shortly be underway on the 3.2 megawatt grid of solar panels.

The city of Cohoes pumps its drinking water supplies from the Mohawk River into the 10-acre, manmade reservoir. The surface of the water is the largest undeveloped open space in the city. Such reservoirs constitute prime sites for solar arrays since the space cannot be used for other purposes. In addition, covering the water’s surface with the solar panels greatly reduces evaporation and helps to inhibit the growth of algae.

There are currently only 14 floating solar arrays in the U.S. and all of those are privately owned. The Cohoes municipal array will be the first of its kind. There are nearly 500 reservoirs in New York State and 24,000 nationwide that could be sites for floating arrays. Drought-stricken Western reservoirs like Lake Mead and Lake Powell could be ideal locations of solar arrays. Those reservoirs lose huge amounts of water to evaporation. There are estimates that floating arrays could provide as much as 10% of the nation’s electrical needs.

**********

Web Links

National Grid gives Cohoes $750,000 for floating solar array project

Photo, posted August 25, 2010, courtesy of Martin Abegglen via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Low For Lake Powell | Earth Wise

November 2, 2021 By EarthWise Leave a Comment

Lake Powell is the second largest reservoir by capacity in the United States. It straddles the border of southeastern Utah and northeastern Arizona and was created by the Glen Canyon Dam, completed in 1963. The reservoir serves as a bank account of water that is drawn upon in times of drought and has made it possible to weather extended droughts by sustaining the needs of cities, industries, and agriculture in western states. Hydroelectric power by the dam’s eight generators provides electricity to seven states.

As a result of the protracted drought in the west, the water levels in Lake Powell have reached the lowest point since 1969. As of September 20, the lake held only 30% of its capacity and federal managers started releasing water from upstream reservoirs to help keep Lake Powell from dropping below the so-called minimum power threshold which is the water elevation that must be maintained to keep the dam’s hydropower turbines working properly.

With the entire Lower Colorado River water system below 40% of capacity, Bureau of Reclamation recently announced that water allocations in the U.S. Southwest would be cut over the next year. The Colorado River basin is managed to provide water to millions of people including those in San Diego, Las Vegas, Phoenix, and Los Angeles.

Successive dry winter seasons over the past two years along with a failed 2020 summer southwestern monsoon, have led to the lowest precipitation levels on record in the Southwest going at least as far back as 1895. With warm temperatures, reduced snowpack, and increased evaporation of soil moisture, most of the American West suffers from persistent and widespread drought.

**********

Web Links

Lake Powell Reaches New Low

Photo, posted June 28, 2021, courtesy of the USFWS – Mountain Prairie via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Floating Solar In New York’s Capital Region | Earth Wise

June 8, 2021 By EarthWise Leave a Comment

We have previously talked about installing solar arrays on the surface of bodies of water. The idea is especially attractive in places like Japan where land resources are scarce. There are several floating solar installations in the UK and the idea is starting to catch on elsewhere as well.

It is quite possible that the largest municipally owned floating solar array may get built in the city of Cohoes in New York’s Capital Region if a project under consideration for federal funding moves forward.

The proposal is for an installation of 8,000 solar panels to cover about 2/3 of the 10-acre Cohoes reservoir. Cohoes has wanted to erect a solar installation to generate power for its buildings but needed to find suitable vacant land. The 10-acre manmade reservoir could be an excellent location for a floating solar array.

Cohoes would be the first community in the US to build and own a floating array on a manmade reservoir and could serve as a model for municipalities across the nation. Such a project makes additional use of land that is already municipal property. According to the city, the 3.2-megawatt array would generate over 4 million kilowatt hours of electricity per year, saving the city $300-350,000 annually.

Cohoes is seeking $4.59 million in federal funding to support the project and has the support of U.S. Representative Paul Tonko for possible inclusion in the 2022 federal budget.

Apart from generating electricity, putting solar panels on the surface of a reservoir reduces evaporation, lowers algae growth, and actually improves solar panel performance because of the cooling effect of the water.

**********

Web Links

Cohoes reservoir could be a floating solar power pioneer

Photo courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Better Solar Evaporator | Earth Wise

May 21, 2021 By EarthWise Leave a Comment

Water security is a serious global problem. Nearly 1.5 billion people – including almost half a billion children – live in areas of high or extremely high water vulnerability. Less than 3% of the world’s water is fresh and demand for it is rising with increasing population growth, urbanization, and growing water needs from a range of sectors.

Researchers at the University of South Australia have developed a promising new technique that could help reduce or eliminate water stress for millions of people. The technique uses highly efficient solar evaporation to obtain fresh water from seawater, brackish water, or even contaminated water. According to the researchers, their technique can deliver enough daily fresh drinking water for a family of four from just one square meter of source water.

Solar evaporation has been the focus of a great deal of effort in recent years, but it has generally been found to be too inefficient to be practically useful. The new technique overcomes those inefficiencies and can deliver fresh water at a fraction of the cost of existing technologies like reverse osmosis.

The system utilizes a highly efficient photothermal structure that sits on the surface of a water source and converts sunlight to heat, focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the liquid. The technique prevents any loss of solar energy and even draws additional energy from the bulk water and surrounding environment.

The system is built entirely from simple, everyday materials that are low cost, sustainable, and easily obtainable.

The technology has the potential to provide a long-term clean water solution to people who can’t afford other systems, and these are the places where such solutions are most needed.

**********

Web Links

Sunlight to solve the world’s clean water crisis

Photo, posted November 13, 2016, courtesy of Steve Austin via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Potential For Solar Canals In California | Earth Wise

April 29, 2021 By EarthWise Leave a Comment

California’s network of almost 4,000 miles of aqueducts is the world’s largest water conveyance system. It serves the state’s Central Valley which produces a quarter of America’s food. About 20% of the nation’s groundwater demand is pumped from Central Valley aquifers.

A recent study by the University of California Santa Cruz and UC Merced has determined that covering these aqueducts with solar panels could be an economically feasible way to advance both renewable energy and water conservation. California’s aqueducts might more properly be called canals because they are located at ground level.

The concept of solar canals has been gaining increasing interest around the world as the changing climate leads to more droughts in many regions. Placing solar panels above the canals can shade them to help prevent water loss through evaporation. In addition, some types of solar panels can work better situated over canals because the cooler environment improves their operation. In addition to the increased solar panel output and the water evaporation savings, shade from solar panels could help control the growth of aquatic weeds, which are a costly canal maintenance issue.

Spanning canals with solar panels can be accomplished either by using steel trusses or suspension cables, either of which is more expensive to build than ordinary ground-mounted solar panel supports. But the research study showed how the benefits of solar canals combine to outweigh the added costs for cable-supported installations.

Apart from the economic benefits of a solar canal system, producing solar energy in the canal system could eliminate the use of 15-20 diesel-powered irrigation pumps, helping to reduce air pollution in a region with some of the nation’s worst air quality.

Solar canals could be a real winner.

**********

Web Links

New analysis shows potential for ‘solar canals’ in California

Photo, posted July 23, 2015, courtesy of Lance Cheung / USDA via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Caspian Sea And Climate Change | Earth Wise

January 22, 2021 By EarthWise Leave a Comment

According to the National Oceanic and Atmospheric Administration, global sea levels have been rising over the past century, and the rate has increased in recent decades. Sea levels are currently rising about one-eighth of an inch every year.

Sea level rise is caused primarily by two factors related to climate change: the added water from melting glaciers and ice sheets, and the expansion of seawater as it warms. While climate change is causing global sea levels to rise, higher temperatures in other regions are having exactly the opposite effect. The water levels are falling.

According to researchers from the University of Bremen in Germany, the Caspian Sea is a perfect example of how a body of water will change. While it is named a sea due to its size and high salinity, the Caspian Sea is actually a lake. In fact, it’s the largest lake in the world. Its largest inflow is the Volga River and it has no natural connection to the ocean. Its water level is determined by the proportional influences of inflow, precipitation, and evaporation. Climate change is causing increased evaporation, which leads to a declining water level.

According to the research team, the water level of the Caspian Sea could fall by 29 to 59 feet during this century.

The Caspian Sea is surrounded by Kazakhstan, Turkmenistan, Iran, Azerbaijan and Russia. It’s an important regional water reservoir, and a biological and commercial center.

The researchers hope the Caspian Sea will be used as an example in scientific research to assess the vulnerability of other regions to falling water levels.

**********

Web Links

Climate crisis is causing lakes to shrink

Photo, posted October 31, 2016, courtesy of Amanderson2 via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Extreme Heat And Humidity | Earth Wise

June 15, 2020 By EarthWise Leave a Comment

On hot, sticky summer days, one often hears the expression “it’s not the heat, it’s the humidity.” That isn’t just an old saw; it is a recognition of what might be the most underestimated direct, local danger of climate change. Extreme humid heat events represent a major health risk.

There is an index called “wet-bulb temperature” that is calculated from a combination of temperature and humidity data. The reading, which is taken from a thermometer covered in a wet cloth, is related to how muggy it feels and indicates how effectively a person sheds heat by sweating. When the wet-bulb temperature surpasses 95^o Fahrenheit, evaporation of sweat is no longer enough for our bodies to regulate their internal temperature. When people are exposed to these conditions for multiple hours, organ failure and death can result.

Climate models project that combinations of heat and humidity could reach deadly thresholds for anyone spending several hours outdoors by the end of this century.

Dangerous extremes only a few degrees below the human tolerance limits – including in parts of the southwestern and southeastern US – have more than doubled in frequency since 1979. Since then, there have been more than 7,000 occurrences of wet-bulb temperatures above 88^o, 250 above 91^o, and multiple reading above 95^o. Even at lower wet-bulb temperatures around 80^o, people with pre-existing health conditions, the elderly, as well as those performing strenuous outdoor labor and athletic activities, are at high risk.

More research is needed on the factors that generate extreme wet-bulb temperatures as well as the potential impacts on energy, food systems, and human security.

**********