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Radiative cooling and solar heating from one system, no electricity needed

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Radiative cooling and solar heating from one system, no electricity needed

Passive cooling, like the shade a tree provides, has been around forever. Recently, researchers have been exploring how to turbo charge a passive cooling technique – known as radiative or sky cooling – with sun-blocking, nanomaterials that emit heat away from building rooftops. While progress has been made, this eco-friendly technology isn’t commonplace because researchers have struggled to maximize the materials’ cooling capabilities.

New research led by University at Buffalo engineers makes significant progress in this area.

A study published Feb. 8 in the journal Cell Reports Physical Science describes a uniquely designed radiative cooling system that:

+ Lowered the temperature inside a test system in an outdoor environment under direct sunlight by more than 12 degrees Celsius (22 degrees Fahrenheit).

+ Lowered the temperature of the test box in a laboratory, meant to simulate the night, by more than 14 degrees Celsius (25 degrees Fahrenheit).

+ Simultaneously captured enough solar power that can be used to heat water to about 60 degrees Celsius (140 degrees Fahrenheit).

While the system tested was only 70 centimeters (27.5 inches) squared, it could eventually be scaled up to cover rooftops, engineers say, with the goal of reducing society’s reliance on fossil fuels for cooling and heating. It also could aid communities with limited access to electricity.

“There is a great need for heating and cooling in our daily life, especially cooling in the warming world,” says the study’s lead author Qiaoqiang Gan, PhD, professor of electrical engineering in the UB School of Engineering and Applied Sciences.

The research team includes Zongfu Yu, PhD, University of Wisconsin-Madison; Boon Ooi, PhD, King Abdullah University of Science and Technology (KAUST) in Saudi Arabia; and members of Gan’s lab at UB, and Ooi’s lab at KAUST.

System design and materials key to success

The system consists of what are essentially two mirrors, made of 10 extremely thin layers of silver and silicon dioxide, which are placed in a V-shape.

These mirrors absorb incoming sunlight, turning solar power from visible and near-infrared waves into heat. The mirrors also reflect mid-infrared waves from an “emitter” (a vertical box in between the two mirrors), which then bounces the heat they carry into the sky.

“”Since the thermal emission from both surfaces of the central thermal emitter is reflected to the sky, the local cooling power density on this emitter is doubled, resulting in a record high temperature reduction,” says Gan.

“”Most radiative cooling systems scatter the solar energy, which limits the system’s cooling capabilities,” Gan says. “Even with a perfect spectral selection, the upper limit for the cooling power with an ambient temperature of 25 degrees Celsius is about 160 watts per square meter. In contrast, the solar energy of about 1000 watts per square meter on top of those systems was simply wasted.””

Spinoff company aims to commercialize technology

Gan co-founded a spinoff company, Sunny Clean Water LLC, which is seeking partners to commercialize this technology.

“One of the key innovations of our system is the ability to separate and retain the solar heating and radiative cooling at different components in a single system,” says co-first author Lyu Zhou, a PhD candidate in electrical engineering in the School of Engineering and Applied Sciences. “During the night, radiative cooling is easy because we don’t have solar input, so thermal emissions just go out and we realize radiative cooling easily. But daytime cooling is a challenge because the sun is shining. In this situation, you need to find strategies to separate solar heating from the cooling area.”

The work builds upon previous research Gan’s lab led that involved creating a cone-shaped system for electricity-free cooling in crowded cities to adapt to climate change.

“The new double-sided architecture realized a record local cooling power density beyond 280 watts per square meter. Under standard atmospheric pressure with no vacuum thermal isolation, we realized a temperature reduction of 14.5 degrees Celsius below the ambient temperature in a laboratory environment, and over 12 degrees Celsius in an outdoor test using a simple experimental system,” says the other co-first author, Haomin Song, PhD, a research assistant professor of electrical engineering in the School of Engineering and Applied Sciences.

“Importantly, our system does not simply waste the solar input energy. Instead, the solar energy is absorbed by the solar spectral selective mirrors, and it can be used for solar water heating, which is widely used as an energy efficient device in developing countries,” says Gan. “It can retain both the solar heating and radiative cooling effects in a single system with no need of electricity. It’s really sort of a ‘magic’ system of ice and fir.”

The research team will continue to investigate ways to improve the technology, including examining how to capture enough solar power to boil water, making it suitable for drinking.

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Solar Energy

2 solar projects to supply power for 5 military installations

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2 solar projects to supply power for 5 military installations


2 solar projects to supply power for 5 military installations

by Mike Heuer

Washington DC (UPI) Jun 18, 2024






The Department of Defense is partnering with Duke Energy to provide solar power for five military bases in North and South Carolina.

The DOD announced the power partnership with Duke Energy in which all power produced by two new Duke Energy solar energy facilities in South Carolina will power the five military bases.

The military bases are the Army’s Fort Liberty, the Marine Corps’ Camp Lejeune and Cherry Point Air Station bases, and the Seymour Johnson Air Force Base in North Carolina.

The Shaw Air Force Base in South Carolina also will obtain power from the two Duke Energy solar power plants that are under construction and expected to be operational by September 2026.

“By supporting the construction of new clean, renewable energy, we are enhancing our resilience in support of the warfighter and DOD’s mission,” Brendan Owens, the DOD’s chief sustainability officer, said in a news release Tuesday.

Owens said the two Duke Energy solar arrays will “deliver power exclusively to [the] DOD over the agreement’s 15-year term and contribute to a more reliable and resilient commercial electric grid.”

The DOD agreed to pay $248 million over 15 years to obtain an estimated 4.8 million megawatt hours of carbon-free solar energy from Duke Energy.

The federal government is the nation’s largest user of energy, and President Joe Biden in 2021 ordered federal agencies to achieve 100% carbon-free electricity usage by 2030.

Biden’s executive order requires government officials to ” support the growth of America’s clean energy industry … in ways that are good for taxpayers and communities,” said Andrew Mayock, chief sustainability officer at the White House Council on Environmental Quality.

Duke Energy recently undertook its Green Source Advantage program to provide renewable energy for the five military bases.

“As our large business customers plan for the future, they also have increasingly specific goals around decarbonization,” Duke Energy Vice-President Meghan Dewey said.

Dewey said those goal “require access to renewable energy sources that can support those needs.”

DOD officials agree.

“This project is a great opportunity to assist our military departments and our warfighters in their decarbonization goals,” Air Force Col. Jennifer Neris said.

The Army’s Assistant Secretary for Installation, Energy and Environment Rachel Jacobson said the Duke Energy partnership is “essential for delivering energy resilience for the Army.”

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Argentina starts removing solar panels from Chilean border

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Argentina starts removing solar panels from Chilean border


Argentina starts removing solar panels from Chilean border

by AFP Staff Writers

Santiago (AFP) June 17, 2024






Argentina on Monday began removing solar panels that were installed by accident on the wrong side of its shared border with Chile, after a complaint from Chilean President Gabriel Boric.

In late April, the Argentine Navy inaugurated a maritime surveillance post on the border with Chile, in the Patagonia region of South America.

But the solar panels, which provide energy to that military unit, were set up on the Chilean side of the frontier.

In a statement, the Argentine Navy acknowledged the mistake and said it had “transferred personnel and means to begin the removal of a solar panel installed in the territory of the sister republic of Chile, north of the Island of Tierra del Fuego.”

Earlier in the day, Boric demanded that the panels be removed or Chile itself would do it.

“Borders are not something that can be ambiguous. It is a basic principle of respect between countries and therefore they must remove those solar panels as soon as possible or we are going to do it,” Boric told reporters during a visit to Paris.

Chile and Argentina share a border of about 5,000 kilometers (more than 3,000 miles).

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Chinese Premier Li targets clean energy in Australia visit

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Chinese Premier Li targets clean energy in Australia visit


Chinese Premier Li targets clean energy in Australia visit

by AFP Staff Writers

Sydney (AFP) June 18, 2024






Premier Li Qiang toured a Chinese-controlled lithium refiner in Perth on Tuesday, a sign of his country’s vast appetite for Australian “critical minerals” required for clean energy technologies.

Li ended his four-day visit to Australia with a tour of the low-carbon energy industry in resource-rich Western Australia.

His first stop was Tianqi Lithium Energy Australia, a 51-percent Chinese-owned venture comprising a mine for hard rock lithium ore, and a lithium refinery.

Along with at least a dozen other officials, China’s second most powerful man donned a white helmet during a rainy visit to the facility south of Perth.

The Chinese premier will also view a private research facility for clean energy-produced “green hydrogen” — touted as a fuel of the future to power heavy-duty items such as trucks and blast furnaces.

Australia extracts 52 percent of the world’s lithium, the vast majority of it exported as an ore to China for eventual refining and use in batteries, notably in China’s world-dominant electric vehicle industry.

But despite being a huge Australian customer, China’s involvement in the country’s critical mineral industry is sensitive because of its dominance of global supply chains.

Australia has only recently begun refining lithium rather than exporting the ore.

And the government has announced a strategic plan to develop new supply chains with friendly countries for critical minerals such as lithium, nickel and so-called rare earths.

Earlier this year, the government ordered five China-linked shareholders to sell off a combined 10 percent stake in Northern Minerals, a producer of the rare earth dysprosium.

Such foreign ownership was against Australia’s “national interests”, Treasurer Jim Chalmers said.

About 99 percent of the world’s dysprosium — used in high-performance magnets — is currently produced in China.

China has invested in critical minerals in Latin America, Africa and Australia over the past 10-20 years, said Marina Zhang, associate professor at the University of Technology Sydney’s Australia-China Relations Institute.

Developing supply chains independent of China is “fine and dandy” but unlikely to be achieved even in the short to medium term, she said.

“We are facing a very time-pressing issue that is fighting against climate change — so that issue should be at the centre of the discourse,” Zhang said.

“But unfortunately the Western allies are taking the approach that China’s dominance across the supply chains of critical minerals is imposing national security threats,” she said.

China’s narrative, however, was that it was investing and making a contribution to sustainability and environmental protection, the analyst said.

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