The mayor of Hangzhou City in east China's Zhejiang Province, speaking at a global mayors' dialogue held in the city on Wednesday, advocated good city governance and development toward a sustainable future by telling the story of how the city's Qiandao Lake has got transformed into a clean and lucrative local signature spot.
The event, first edition of the Global Mayors Dialogue with the topic of urban governance and sustainable development, was attended by mayors and representatives from 24 cities in 15 countries and regions, along with representatives of envoys to China and relevant Chinese government departments.
At the dialogue, Yao Gaoyuan, the mayor of Hangzhou, said that Qiandao Lake, located in the city's Chun'an County, is actually an artificial lake built during the construction of the Xin'an River Hydropower Station. Like dazzling gems,1,078 islands dot the lake and thousands of smaller ones are scattered across it. Hence, the lake has earned the name of "Qiandao Lake," which literally means "Thousand Islands Lake" in Chinese.
The mayor noted that the lake was once poorly protected and misused simply for industrial development, but the advice from Chinese President Xi Jinping, serving as chief of the Zhejiang provincial committee of the Communist Party of China back then, has changed the area's focus on water governance. Xi emphasized the importance of finding the delicate balance between economic growth and environmental protection to keep harmony between humanity and nature.
"In the early 1980s, the development and protection of the Qiandao Lake went through detours. In an effort to boost the local economy, industrial parks were established on the lake's shores, focusing on low-end manufacturing, and aquaculture was also developed on the water surface. This extensive development approach somewhat impacted and polluted the lake's water body to a certain extent," said the mayor.
"In 2005, during Xi's tenure in Zhejiang, he visited Chun'an for research and proposed a shift in the area's development approach. He emphasized the importance of leveraging the ecological value of the Qiandao Lake. He said, 'We must not let the 450,000 people of Chun'an hold a golden bowl but beg for food.' Since then, Chun'an has set a development strategy that relies on the water resources," Yao said.
The lake water's quality has gotten significantly improved since the materialization of the Lucid Water-Lush Mountain theory, which the president proposed on his inspection tour in Zhejiang's Yucun village in August 2005, calling lucid waters and lush mountains invaluable assets comparable to the gold and silver of legend. The successful cultivation of a household brand of mineral water using the lake's water-- Nongfu Spring demonstrates that environment-friendly industries have became a driver of the local economy.
"Hangzhou adopted two key approaches. The first was to foster an environment-friendly bottled water industry. Last year, just the water beverage companies alone generated over 100 million yuan (about 14 million U.S. dollars) in tax revenue and resulted in sales of over 14 billion yuan (about 2 billion U.S. dollars). The other approach was to tap into the ecological tourism potential of the lake's pristine water resources. Last year, Chun'an County received 12 million tourist visits to the Qiandao Lake, which is equivalent to the size of the population of Hangzhou. These 12 million tourist visits brought in 17 billion yuan (about 2.4 billion U.S. dollars) in tourism revenue. By embracing the Lucid Water-Lush Mountain theory, not only can we protect the local ecology, but we can also boost the local economy, and most importantly, bring wealth to local people," said Yao.
Hangzhou mayor shares experience in turning lake water into "gold mine"
Major breakthroughs by Chinese scientists have laid the foundation for a future where space-based solar power stations are capable of wirelessly transmitting energy to Earth and spacecraft, though significant engineering problems remain.
A research team from Xidian University in northwest China's Shaanxi Province has made significant progress on the Sun Chasing project, or "Zhuri" in Chinese. The team has developed a ground-based test system for wireless power transmission that can charge multiple moving targets at the same time.
In recent tests, the system achieved a wireless power transmission efficiency of 20.8 percent from direct current to direct current over a distance of 100 meters. It delivered 1,180 watts of power. The team has also built a wireless charging system for drones. In a test, a drone flying at 30 kilometers per hour was able to receive 143 watts of stable power from 30 meters away.
A space solar power station works exactly as its name suggests: a huge array of solar panels placed in orbit. It would collect sunlight in space, where the sun always shines, and then convert that energy into microwaves or lasers to beam down to Earth or directly to satellites and spacecraft. This could address two significant issues: supplying uninterrupted power for space missions and alleviating energy shortages on the ground.
"The construction of space solar power stations could become a major undertaking in the future. One potential benefit is access to a virtually unlimited power supply. Because energy can be collected continuously in space 24 hours a day, electricity could be supplied on an uninterrupted basis," said Fan Guanheng, an associate professor at the School of Mechano-Electronic Engineering at Xidian University.
"Secondly, it could reduce our dependence on fossil fuels, thereby lowering carbon emissions and helping protect the environment. Thirdly, it could support the development of charging infrastructure in space and enable wireless microwave charging for spacecraft, changing the way power is supplied to space vehicles," the professor added.
In 2018, the research team launched the first phase of the Sun Chasing project to build a ground test system. By June 2022, they had completed the world's first full-link, full-system ground validation system for a space solar power station. Now, the team has moved to phase two. The goal now is to solve the challenges of generating high power in space and transmitting it efficiently over long distances.
According to Duan Baoyan, an expert at Xidian University and an academician of the Chinese Academy of Engineering, recent breakthroughs include improving the efficiency of solar energy collection and conversion, increasing the precision of microwave beam control to reduce energy loss, and making the transmitting and receiving antennas smaller and lighter, which is critical for space application.
The team has also solved the problem of how to power multiple moving targets at once using a single transmitter. This means that in the future, one space power station could potentially supply electricity to several satellites or ground vehicles at the same time, Duan said.
Despite the advances in ground-based validation, a series of technical challenges must still be overcome before the technology can be deployed in space.
"The first issue that needs to be addressed is the adaptability of components to the space environment, as conditions in space are completely different from those on Earth, including radiation exposure and extreme temperatures. Another challenge involves the deployment and retraction design of transmitting and receiving antennas. We also need to develop thermal management systems to cope with extreme temperatures and temperature fluctuations in space. These are all areas where further breakthroughs are needed," said Qian Sihao, an associate professor at the School of Mechano-Electronic Engineering at Xidian University.
"We have now completed the development and validation of a ground-based test system, and our next step is to carry out in-orbit wireless microwave power transmission," Fan said.
With ground validation complete, the team now turns its attention to overcoming the harsh realities of space, aiming to demonstrate in-orbit wireless power transmission and bring the vision of orbital solar energy closer to reality.
Space-to-earth solar power moves closer to reality although hurdles remain: scientists
