New transparent airgel for better solar power plants


It is modular, easy to deploy and can generate process heat up to 1,300 degrees Fahrenheit. This is the terrain of a new concentrating solar power system fitted with heat-trapping tiles in the form of a transparent, sponge-like airgel. The ultimate goal is to clean up fossil fuels from hard-to-decarbonize areas of the industrial sector. Now where are all these people who thought that the concentration of solar energy was a dead end?

Focus solar energy on anyone: the report of my death was …

Concentrated solar power systems are designed to provide heat, not electricity. They work by collecting ambient sunlight from many different points, usually from a set of specialized mirrors or a series of long troughs. The concentrated light is focused on a central point in the case of mirrors, or long tubes in the case of troughs. The heat is then transferred to a transportable recirculating fluid such as molten salt or specialized oil.

Typically, the hot fluid is then used to boil water to generate steam. In turn, the steam is used to run turbines to generate electricity. This begs the question of why not just use solar cells to directly generate electricity and ignore everything related to steam generation. After all, steam adds more infrastructure, more complexity, and more costs.

This was the basic argument made by critics of concentrating solar technology in the early years. However, one of the attractions of concentrating solar energy is the angle of energy storage. Once the circulating fluid is heated, it can potentially stay hot for hours, allowing a steam plant to continue producing kilowatts long after the sun has set.

… an exaggeration

Despite a deluge of criticism, the US Department of Energy began promoting the concentration of solar power as a showcase of US clean energy know-how throughout the Obama administration. The Department of Energy continued to carry the torch for further technological improvements during the administration that followed the Obama administration and has since been replaced by the Biden administration. The projects included exciting initiatives in the area of ​​supercritical carbon dioxide and other innovations aimed at enabling solar power to compete mano-a-mano with fossil fuels for control of the country’s electricity grid.

It is all well and good to decarbonize the activity of electricity production, but it still leaves wide open the field of heat for industrial processes.

Earlier this year, the Department of Energy’s National Renewable Energy Laboratory analyzed the numbers and highlighted the need to do something about the heat of industrial processes, such as paper mills and other industrial processes that require heat. the heat.

“Fossil fuels account for about 87% of all manufacturing fuel consumption in the United States, which is essentially the same as four decades ago,” NREL observed, stressing the need for a strategic approach.

Ironically enough, a good deal of this manufacturing fuel use is related to petroleum refining. Based on 2014 figures, NREL estimates that the petroleum industry is by far the largest user of industrial process heat fuel, with 2 to 1/2 times the second largest user.

By counting down oil refineries in order of size, NREL ranks the largest users of process heat such as paper mills (except newsprint), cardboard mills, iron and steel manufacturing, industrial products basic chemicals and ethyl alcohol production. Together with petroleum, these sectors account for about half of all industrial process heat used in the United States.

A new life for the concentration of solar energy

Among other solar technologies, the new NREL report indicates that the concentration of solar systems that deploy parabolic collectors could be the key to an effective strategy for decarbonizing industrial processes.

“PTC technology, when combined with energy storage (TES), not only has the greatest opportunity in terms of distribution over geography and time, but also in terms of applicable IPH requirements, ”enthuses NREL, adding that“ PTC with TES represents the displacement of nearly 2,500 billion Btus of combustion fuels, corresponding to 137 million metric tons of CO2, or about 15% of all industrial combustion CO2 emissions.

All this to say that improvements in parabolic dish technology could significantly reduce emissions from industrial energy users.

This is where the new airgel comes in. Last week, the University of Michigan announced it was deploying a $ 3.1 million Department of Energy grant for the development of a new “transparent solar airgel” for use in solar power plants. with trough concentration.

“Parabolic displacement power plants, currently the most widely deployed solar thermal technology, use a kind of half mirror tube to focus sunlight on receiving tubes carrying a circulating fluid. This fluid absorbs heat and transports it for storage or use, to generate electricity or to produce fuels and other chemicals, ”the school explains.

The problem is that conventional trough systems do not heat the circulating fluid enough to power many industrial processes. With the help of special coatings, they can reach around 1,000 degrees Fahrenheit, allowing them to cover some industrial use cases, but many more remain intact, which is why the researchers are looking for aerogels and other new, more durable coatings. and more efficient.

A love letter from NASA to Earth

Given that the United States dominated the early years of the global solar industry through its space program, it is fitting that the University of Michigan research team took inspiration from the ceramic aerogels used in the shuttle. spatial.

An airgel is an extremely light and porous material. Clays and polymers are among the materials commonly used in the manufacture of aerogels. To get a full picture of what’s going on with aerogels, NASA invites you to imagine making gelatin from powder and water, then removing all the water while allowing the gelatin to retain a solid shape and structure, without moving, that is.

Both NASA and the Department of Energy are very interested in aerogels because of their superior insulating qualities, which is why they appeared on the outside of the space shuttle, among other uses.

The trick is to let in the most sunlight for the most effective heat gain, while preventing the most heat from escaping. The team worked with AeroShield Materials Company to develop their new transparent airgel tiles, sized for use in a standard four-meter parabolic trough.

Sustainability is also a factor. With the help of the company Forge Nano, the airgel tiles have a special very thin coating that prevents them from degrading or cracking at high temperatures.

The team is confident that the new airgel will allow parabolic solar power systems to heat circulating fluid up to 1,300 degrees Fahrenheit. They are also considering a modular and scalable system that could be widely deployed on industrial sites.

Next steps for concentrating solar energy

With the new funding in hand, the team will be able to build a pilot scale demonstration system. The plan also includes developing manufacturing strategies that improve efficiency and reduce costs.

In addition to the $ 3.1 million for the demonstration model, the team also won a $ 300,000 grant from the Department of Energy to identify materials that provide an even more efficient balance between gain and heat. heat loss for concentrating solar systems.

It looks like the solar industry is about to enter the era of transparency. In addition to transparent aerogels for concentrating solar systems, photovoltaic technology is also getting a makeover.

Follow me on Twitter: @TinaMCasey.

Photo: “A sun-transparent airgel is placed in a device that will apply an atomic-thick coating for use in solar thermal power plants. Image credit: Evan Dougherty / Michigan Engineering.

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