permeable

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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Web Links

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

New Membranes For Carbon Capture

October 2, 2019 By EarthWise Leave a Comment

Drastically reducing the amount of carbon dioxide being emitted into the atmosphere is an essential goal in the effort to mitigate the effects of climate change. While the ultimate solution is to avoid combustion of fossil fuels by the use of clean alternative energy sources, that transition will take time – possibly more time than we have. As a result, there is a great deal of effort underway to develop techniques for capturing the carbon emitted by fossil fuel combustion and either recycling it or storing it.

There are multiple ways to capture carbon emissions, but the ultimate goal is to find a technique that is both inexpensive and scalable. One promising technique involves the use of high-performance membranes, which are filters that can specifically pick out CO2 from a mix of gases, such as those coming out of a factory smokestack.

Scientists at a Swiss laboratory have now developed a new class of high-performance membranes that exceeds the targeted performance for carbon capture by a significant margin. The membranes are based on single-layer graphene with a selective layer thinner than 20 nanometers – only about 40 atoms thick. The membranes are highly tunable in terms of chemistry, meaning that they can be designed to capture specific molecules.

The membranes are highly permeable – meaning that they don’t impede gas flow too much – but highly selective. The CO2/N2 separation factor is 22.5, which means that 22.5 times more nitrogen can get through the membrane than carbon dioxide.

The work is just at the laboratory stage at this point, but it is a very promising step towards developing a practical scheme for keeping carbon dioxide from escaping from power-plant and factory smokestacks.

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Web Links

Next-gen membranes for carbon capture

Photo, posted December 28, 2010, courtesy of Emilian Robert Vicol via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.