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Giant batteries in the Earth

December 23, 2024 By EarthWise 1 Comment

The wind and the sun are inexhaustible sources of energy, and we are tapping into them to produce electricity at a growing rate around the world. But neither of them is always available when we need them. When the sun isn’t shining and the wind isn’t blowing, they don’t work.

An opposite problem also exists. When our energy needs are low, but it is sunny or windy, solar and wind power are all dressed up with nowhere to go. Energy storage is the answer to both of these problems. When there is excess generation, store the energy for later use. When there is need for energy and not enough is being generated, tap into the energy that is stored.

Giant banks of lithium-ion batteries are the rapidly growing form of energy storage, and they are increasingly providing resilience in the electric grid. But battery storage is short-term energy storage. Even the largest battery banks can only provide a few hours of electricity.

So, there is a real need for “long-duration energy storage” – systems that provide at least 10 hours of backup power and sometimes much more – for the grid to be fully reliable.

Pumped hydro storage, which uses water from elevated reservoirs to drive turbines, has been around for a long time. Historically, this is the largest form of energy storage in the world. Other methods include pumping compressed air into underground caverns or lifting massive blocks into elevated positions. All of these techniques use excess electricity to place things like water, air, or cement into a position where they can be used to drive electrical generators.

The grid of tomorrow will store energy in giant battery banks, but also in the ground, in reservoirs, and in large structures.

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How giant ‘batteries’ in the Earth could slash your electricity bills

Photo, posted March 21, 2024, courtesy of Sandra Uecker/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Capturing hot carbon dioxide

December 13, 2024 By EarthWise Leave a Comment

Decarbonizing industries like steel and cement is a difficult challenge. Both involve emitting large amounts of carbon dioxide both from burning fossil fuels and from intrinsic chemical reactions taking place. A potential solution is to capture the carbon dioxide emissions and either use them or store them away. But this sort of carbon capture is not easy and can be quite expensive.

The most common method for capturing carbon dioxide emissions from industrial plants uses chemicals called liquid amines which absorb the gas. But the chemical reaction by which this occurs only works well at temperatures between 100 and 140 degrees Fahrenheit. Cement manufacturing and steelmaking plants produce exhaust that exceeds 400 degrees and other industrial processes produce exhaust as hot as 930 degrees.

Costly infrastructure is necessary to cool down these exhaust streams so that amine-based carbon capture technology can work.

Chemists at the University of California, Berkeley, have developed a porous material – a type of metal-organic framework – that can act like a sponge to capture CO2 at temperatures close to those of many industrial exhaust streams. The molecular metal hydride structures have demonstrated rapid, reversible, high-capacity capture of carbon dioxide that can be accomplished at high temperatures.

Removing carbon dioxide from industrial and power plant emissions is a key strategy for reducing greenhouse gases that are warming the Earth and altering the global climate. The captured CO2 can be used to produce value-added chemicals or can be stored underground or chemically-reacted into stable substances.

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Breakthrough in capturing ‘hot’ CO2 from industrial exhaust

Photo, posted March 3, 2010, courtesy of Eli Duke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Solar-powered desalination

November 7, 2024 By EarthWise Leave a Comment

People in remote, low-income regions far from the ocean often need to meet their water needs from groundwater and groundwater is becoming increasingly saline due to climate change. Desalination of brackish groundwater is a huge and largely untapped source of drinking water, but there are challenges in making the process efficient and reliable.

Engineers at MIT have developed a solar-powered desalination system that requires no batteries or external power sources and is capable of producing large quantities of clean water despite the variations of sunshine throughout the day.

The system is based on the process of electrodialysis and consists of water pumps, an ion-exchange membrane stack, and a solar panel array. What is unique about it is that it makes use of sensors and a control system that predicts the optimal rate at which to pump water through the system based on the output of the solar panels. As a result, it uses nearly all of the electricity generated to produce clean water and does not need stored or grid-based energy.

The MIT engineers tested a community-scale prototype on groundwater wells in New Mexico over a six-month period. The system harnessed on average over 94% of the electricity generated by its solar panels and produced as much as 5,000 liters of water per day despite large variations in weather and sunlight.

The new renewable-powered, battery-free system could provide much-needed drinking water at low cost, especially for communities where access to seawater and to grid power are limited. The team plans to further test and scale up the system so it can supply larger communities and even whole municipalities with low-cost drinking water.

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Solar-powered desalination system requires no extra batteries

Photo courtesy of Shane Pratt.

Earth Wise is a production of WAMC Northeast Public Radio

Geological thermal energy storage

August 7, 2024 By EarthWise Leave a Comment

The electricity grid is increasingly using solar and wind power. Depending on those two sources requires the ability to store energy to have on hand when the sun isn’t shining and the wind isn’t blowing. Energy needs to be stored away to be used hours, days, or even weeks after it is produced.

Energy storage is booming. California has increased its energy storage capacity tenfold in recent times. One day in April, storage batteries were the largest source of electricity in the state for a period of two hours. But batteries are not the only way to store energy. There are chemical, electrochemical, mechanical, and thermal methods that each has potential advantages and unique features.

A project in Kern County, California, is making use of an abandoned oil field to create a long-term energy storage installation. The plan is to retrofit depleted oil wells to store concentrated solar energy in superheated groundwater for long periods of time. The stored heat can then be used to drive turbines when electricity is needed.

Some 1,200 feet below the surface of the oil field are pockets of permeable sandstone that have been emptied of the oil they previously contained. An array of parabolic mirrors will gather solar energy that will heat silicon oil in an underground loop to 700 degrees Fahrenheit. The oil pipeline will heat up groundwater down below. When electricity is needed, the heated groundwater will be brought to the surface to operate turbines.

There is no new technology involved. The individual aspects have never all been combined before, but the likelihood of success is high. There are lots of depleted oil fields that could be used this way in the future.

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Can a California Oilfield Be Retrofitted to Store Solar Energy?

Photo, posted July 18, 2017, courtesy of John Ciccarelli / BLM via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Shrinking African glaciers

March 27, 2024 By EarthWise Leave a Comment

We don’t usually associate Africa with glaciers, but the continent has had glaciers on its highest peaks for the past 10,000 to 15,000 years. Africa’s glaciers are found in three regions: the Rwenzori Mountains along the border between Uganda and the Democratic Republic of the Congo, Mount Kilimanjaro, and Mount Kenya. At the turn of the 20th century, there were 43 glaciers scattered across 6 peaks within the Rwenzori Mountains. In the intervening years, things have greatly changed.

Since the early 20th century, Africa’s glaciers have shrunk by 90%. Because all these glaciers are close to the equator, they are especially vulnerable to warming. According to a new study published in the journal Environmental Research: Climate, in the last two decades, Africa’s glaciers have lost roughly half their area.

This rapid decrease is alarming to climate scientists because they represent a clear indicator of the impact of climate change. A major factor in the decline of the glaciers is the reduction in cloud cover over the mountains. Sunshine is melting glaciers and turning ice directly into water vapor even when temperatures are below freezing. Reductions in snowfall at the same time means that the melting glaciers are not being replenished.

Scientists believe that the tropical glaciers of Africa may all but disappear over the next 25 years.

Roughly three-quarters of the Earth’s freshwater is stored in the world’s more than 200,000 glaciers. According to scientists, if the world reaches but maintains 1.5 degrees of warming, half of the world’s glaciers could be gone by the end of this century. If the world continues to warm as it has been without slowing down, more than 80% of the glaciers will disappear.

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Africa’s Tropical Glaciers Have Shrunk by 90 Percent, Research Shows

Photo, posted February 26, 2022, courtesy of Ray in Manila via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Moisture swing carbon capture

November 10, 2023 By EarthWise Leave a Comment

As the world grapples with limiting the amount of carbon dioxide in the atmosphere, there is a growing need to capture the carbon dioxide that is emitted as well as preventing it from being emitted in the first place. Carbon capture can be accomplished at the source of emissions (such as power plants) or it can be done by taking it out of the atmosphere. The latter is called “direct air capture”.

It is not at all clear whether direct air capture can be accomplished on a scale that would really make a difference and at an acceptable cost either in dollars or energy expended. But if it can be done that way, it would be a major tool in combatting climate change.

Direct air capture technology generally makes use of sorbent materials whose capacity to capture carbon dioxide and later release it is a function of temperature. The process requires significant amounts of energy to release the carbon dioxide that has been captured.

New research from Northwestern University makes use of the “moisture-swing” technique which uses materials whose ability to capture and release carbon dioxide depends on humidity rather than temperature. While it takes some amount of energy to humidify the volume of air containing the sorbent material, it is very small compared to temperature-driven systems.

There are many groups working with moisture-swing technology, but the Northwestern Group has identified a number of new sorbent materials with superior properties.

The fundamental questions of scalability and cost remain, but moisture-swing is a promising approach to direct air capture. If carbon dioxide can be pulled out of the atmosphere in large volumes, it can be concentrated and stored or converted into useful products.

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Pulling carbon dioxide right out of the air

Photo, posted May 15, 2020, courtesy of James Watt via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Generating Hydrogen From Poor-Quality Water | Earth Wise

September 8, 2020 By EarthWise Leave a Comment

Hydrogen could be the basis of a complete energy system. It could be stored and transported and could be used to power vehicles and to generate electricity in power plants. Proponents of the so-called hydrogen economy contend that hydrogen is the best solution to the global energy challenge. But among the challenges faced by a hydrogen economy is the development of an efficient and green method to produce hydrogen.

The primary carbon-free method of producing hydrogen is to break down water into its constituent elements – hydrogen and oxygen. This can be done in a number of ways, notably by using electricity in a process called electrolysis. A method that seems particularly attractive is to use sunlight as the energy source that breaks down the water molecule.

While there is an abundance of water on our planet, only some of it is suitable for people to drink and consume in other ways. Much of the accessible water on earth is salty or polluted. So, a technique to obtain hydrogen from water ideally should work with water that is otherwise of little use to people.

Researchers in Russia and the Czech Republic have recently developed a new material that efficiently generates hydrogen molecules by exposing water – even saltwater or polluted water – to sunlight.

The new material is a three-layer structure composed of a thin film of gold, an ultra-thin layer of platinum, and a metal-organic framework or MOF of chromium compounds and organic molecules. The MOF layer acts as a filter that gets rid of impurities.

Experiments have demonstrated that 100 square centimeters of the material can generate half a liter of hydrogen in an hour. The researchers continue to improve the material and increase its efficiency over a broad range of the solar spectrum.

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New Material Can Generate Hydrogen from Salt and Polluted Water

Photo courtesy of Tomsk Polytechnic University.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Catalyst For Splitting Water

August 13, 2018 By EarthWise Leave a Comment

Hydrogen is widely considered to be a desirable source of clean energy. It can be used in fuel cells to power electric motors in cars or can be burned directly in internal combustion engines. If it is compressed or converted to liquid, it can be efficiently stored and transported. Most of all, when it is used as an energy source, the only emission it produces is water.

Geothermal Heating

July 27, 2016 By WAMC WEB

Geothermal heat pumps use the heat stored in the earth’s surface to heat homes and buildings. Even in the dead of winter, the temperature not very far below ground remains at a temperature typically in the 50s. Geothermal systems tap into this immense thermal resource. Conversely, this same temperature sink can be used to provide cooling during the summer. It takes electricity to run the heat pumps, but is vastly more efficient than using electricity directly to produce heat or to cool air.

[Read more…] about Geothermal Heating