South Korea

Agrivoltaics for broccoli, cabbage

Image: Chonnam National University

Scientists in South Korea have combined PV generation with vegetable farming and have found that solar array shading provides favorable results for crops such as broccoli and cabbage.

From pv magazine

A research team at Chonnam National University in South Korea has looked at how solar power generation could be combined with broccoli and cabbage cultivation. The team found that the shading provided by a PV facility could improve the quality of crops.

Broccoli and cabbage need to be grown in places that receive full sun, which means between six and eight hours of sunlight per day, or very light shade. A lack of sunlight could result in thin, leggy plants.

“Because of its low light saturation points, broccoli may be a suitable crop to maximize famer’s profits and energy security through an agrivoltaic system,” the scientists said. “However, to date, there is limited information on the performance of brassica crops in agrivoltaics.”

The scientists built their agrivoltaic system with bifacial modules at a height of 3.3 meters. They achieved an average power generation per day of 127 kWh during the testing period. They claimed that their approach demonstrated the technical and economic viability of the proposed agrivoltaic solution.

“We found that the taste and the quality of the broccoli were not lower than those of a reference field without the solar array,” they said. “We also found no significant change in functional ingredients and metabolites that affect taste.”

The PV installation caused a significant reduction in the light hitting the crops, which in turn resulted in an improvement of their color.

“The color of broccoli is an important property that goes beyond appearance quality and is involved in consumers’ desire to purchase,” the scientists said.

They said that presence of the PV system reduced the agricultural yield by around 20%, compared to the reference field without solar. However, they said that the income generated by the solar array could more than compensate for such losses.

“The annual economic benefit from solar power was 10.4 times more than the broccoli production benefits,” the scientists said. “Therefore, farmer benefits will increase as they are cultivated in agrivoltaics compared to open field.”

The researchers presented their findings in “Agrivoltaic Systems Enhance Farmers’ Profits through Broccoli Visual Quality and Electricity Production,” which was recently published in Agronomy.

“In terms of land use efficiency, agrivoltaic is a good means of producing energy and food in Korea, which is a highly mountainous area,” they said.

Author: Emiliano Bellini

Perovskite microcells for solar windows

Photograph of a mosaic-patterned colored solar window with four different colors. Image: Seoul National University, nature communications, Creative Commons License CC BY 4.0

Developed by Korean scientists through a novel lift-off-based patterning approach based on swelling-induced crack propagation, the perovskite PV device achieved an open-circuit voltage of 1.16 V, a short-circuit current density of 22.5 mA/cm2, and a fill factor of 77%. With the microcells, the researchers also built a first prototype of a solar window which they claim has vivid colors and high color purity.

From pv magazine

Researchers in South Korea have developed perovskite microcells with a power conversion efficiency of 20.1% that can be used in colored solar windows.

The devices were built with a novel lift-off-based patterning approach based on swelling-induced crack propagation.

“The swelling-induced lift-off method allows the fabrication of a flat, uniform, crystalline, and patterned perovskite film without defects such as fracture or partial delamination,” the scientists explained. “In addition, the simultaneous lift-off patterning of the perovskite layer and electron transport layer (ETL) minimizes interfacial defects.”

In the process, the perovskite film was deposited by spin-coating on layers made of poly(methyl methacrylate) (PMMA) and polyimide (PI) that were prepatterned via oxygen plasma etching. A top silicon oxide (SiO2) layer is utilized as an etch stop layer for the dry etching of PMMA/PI layers and is finally wet-etched using a buffered oxide etchant (BOE).

After cracks propagate along the edge, the PI/perovskite layers are detached from the substrate without any fractures or partial delamination of the patterned films on the substrate.

“During the prepatterning of the PMMA/PI layers, the substrate becomes hydrophilic owing to oxygen plasma. Thus, the perovskite precursor can be spread over the entire substrate,” the scientists said, noting that this step allows the deposition of a perovskite film with a uniform thickness, a flat surface, and conformal coverage.

Schematic exploded view of the colored solar window with the metal–insulator–metal (MIM) resonant structure. Image: Seoul National University, nature communications, Creative Commons License CC BY 4.0

The micro cell was built with an insulation layer deposited on the ETL to prevent a direct contact between the ETL and the hole transport layer (HTL (violet). The insulation layer was then patterned and etched to expose the ETL inside the microcell area. The perovskite layer was deposited and patterned after the deposition of the HTL and top electrode.

The scientists tested 458 perovskite microcells with a diameter of 100 μm and an electrode area of 9 mm2 and found that the champion device, under standard illumination conditions, the cell achieved an efficiency of 20.1%, an open-circuit voltage of 1.16 V, a short-circuit current density of 22.5 mA/cm2, and a fill factor of 77%. The microcells also showed a light utilization efficiency of 4.67 and a color rendering index of 97.5 %.

With this PV device, the researchers also built a first prototype of a solar window which they claim has vivid colors and high color purity. The window was fabricated with metal–insulator–metal structures and moth-eye-inspired nanostructures.

The microcell design is introduced in the paper Perovskite microcells fabricated using swelling-induced crack propagation for colored solar windows, which was recently published in nature communications. The research team includes academics from the Seoul National University, the Institute for Basic Science (IBS), and the Gwangju Institute of Science and Technology.

Author: Emiliano Bellini

Giant floating solar flowers offer hope for coal-addicted South Korea

Floating solar panels on the surface of Hapcheon Dam in South Korea. The project can generate enough to power 20,000 homes, according to Hanwha Solutions. Image: SeongJoon Cho/Bloomberg

From Bloomberg

[SEOUL] More than 92,000 solar panels in the shape of plum blossoms, floating on the surface of a reservoir in South Korea, offer a vision of how land-scarce developed nations can overcome local resistance to giant renewable-energy projects.

The 17 giant flowers on the 12-mile-long (19 km) reservoir in the southern county of Hapcheon are able to generate 41 megawatts (MW), enough to power 20,000 homes, according to Hanwha Solutions, which built the plant.

It’s one of the biggest floating solar plants in the world, and it’s in a nation that has been a laggard in adopting renewable energy, even though South Korea’s industrialised economy relies heavily on imported fossil fuels.

“South Korea needs a massive amount of renewable energy to meet its climate target, and floating solar can be a part of the solution”, because it faces less opposition from residents and doesn’t use land, said Kim Jiseok, a climate and energy specialist at Greenpeace Korea.

At a commissioning ceremony for the plant in November, South Korea’s President Moon-Jae in said floating solar can help the nation reach its goal of becoming carbon neutral by 2050 with the potential to add 9.4 gigawatts (GW), or the equivalent of 9 nuclear reactors.

Floating solar arrays have been gaining traction, especially in Asia, from nations like South Korea and Singapore where most available land for large-scale solar farms is already given over to buildings or agriculture.

Thailand built the world’s largest hydro-floating solar hybrid system on the Sirindhorn reservoir last year, and Singapore has started a 60-megawatt-peak plant on its Tengeh Reservoir. India plans to complete its huge 600 MW plant above the Omkareshwar dam by 2023.

“Floating solar is increasingly a popular option in countries such as South Korea, where land regulations and pricing, as well as local opposition, has made it increasingly difficult to build utility-scale projects,” said Ali Izadi-Najafabadi, a BloombergNEF analyst. “For water-reservoir owners, floating solar is doubly attractive as it adds a new revenue stream, while at the same time reducing evaporation.”

Floating projects typically benefit from an easier connection to the power grid, either via an existing link from a hydroelectric plant or because the reservoir is close to an urban area. Photovoltaic panels can also help restrict algae blooms, while the water helps keep panels cool in hot climates, increasing their efficiency.

They are costlier to build, though. Due to the need for floats, moorings and more resilient electrical components, floating systems are considered about 18 per cent more expensive than land-based ones, according to the World Bank.

Hapcheon shows how reservoir-based systems can help overcome one of the biggest obstacles to expanding renewables in developed nations – the not-in-my-backyard mentality of local residents.

The Hapcheon Dam was built in the late 1980s during the military dictatorship of Chun Doo-hwan, with villagers forcibly evicted in order to promote hydropower and irrigation. Sixty-four-year-old Cho Jaesung remembers catching fish and swimming in the river as a child, before the valley and his village was submerged.

Local investors

The reservoir is now managed by state-run Korea Water Resources and when the floating power plant was proposed, Cho and other residents were given the chance to invest. Some locals were also offered jobs during construction, in an area where the average age is almost 60.

“We really didn’t have a choice when the dam was built over 30 years ago, but it was nice to be part of the nationwide transition from the start this time,” Cho said in an interview. “The project also provides an extra bit of money for older folks in the neighbourhood, who mainly depend on their children.”

About 1,400 residents collectively have invested 3.1 billion won (S$3.4 million), or about 4 per cent of the total cost, expecting to receive a 10 per cent annual return over 20 years. It was the community that requested the panels be arranged in the shape of blossoms to make the site more visually appealing.

The arrays use Hanwha’s latest technology, specially adapted for water, with greater resistance to humidity and heat, according to the company. Hanwha, Korea’s biggest producer of photovoltaic modules, is now working on a 63-megawatt floating plant on Goheung Lake in the south of the country, which would be the nation’s biggest.

“We see a huge potential in the global floating solar market as more countries adopt the technology,” said Shin Hyungseob, general manager at Hanwha Solutions, which produces panels under the brand Q Cells. “We’re hoping to export the modules.”

Solar’s overall share of generating capacity will rise as countries strive to meet carbon goals and floating panels are set to benefit, Wood Mackenzie said in a report.

While solar is South Korea’s leading renewable energy source, with 21 gigawatts, the nation will need at least 375 gigawatts to reach net zero, according to the Green Energy Institute.

“Even with the help of floating-solar plants, South Korea has a long way to go and little time to tackle the climate crisis,” said Greenpeace’s Kim. “If we don’t speed up the deployment of renewable energy now, we’re going to miss the deadline.”