Editor's note: As protection of the planet's flora, fauna and resources becomes increasingly important, China Daily is publishing a series of stories to illustrate the country's commitment to safeguarding the natural world.

The term "the cloud" evokes images of something light and ethereal, but the reality of the digital infrastructure that stores our photos, streams our movies, and trains our artificial intelligence models is far more energy-intensive — and hot. Data centers around the globe are voracious consumers of electricity, with a significant portion dedicated to cooling.

In Central China's Hunan province, a visionary project is challenging this paradigm. Beneath the surface of a picturesque lake nestled between mountains in Zixing, Chenzhou city, the water maintains a constant, chilly 8-13 C year-round. This natural asset has been transformed from a mere scenic marvel into the lifeblood of a burgeoning "green data castle" on its shores.

Dongjiang Lake, an artificial reservoir in the Xiangjiang River water system, spans 160 square kilometers with a total storage capacity of 8.1 billion cubic meters. It is a renowned scenic area and serves as a vital source of drinking water to over 2 million people, according to the Sustainable Development Promotion Center in Chenzhou.

A few kilometers away, in the Dongjiangwan area, the Yunchao Dongjiang Lake Big Data Center hosts over 3,800 server racks from the country's top information platforms. To maintain optimal temperatures and prevent malfunctions, the servers are cooled using the lake's cold water. According to local authorities, the center, which started operation in 2017, is one of China's first big data centers fully cooled by natural water.

Traditionally, data centers use compressors, which are also widely used in household air-conditioning, to cool servers — a method that consumes significant power.

To improve the energy efficiency of the industry, in 2014, entrepreneur Lei Jianjun envisioned using natural cold water to cool a data center. After evaluating water resources and construction conditions in multiple locations, Lei and his team chose Dongjiang Lake.

On its shore, they built a big data center, designed to provide data storage, computing and internet access services for the internet and finance industries across the region and beyond.

"We pioneered the direct supply and full natural cooling technology of lake water," said Kuang Bin, an official from the Dongjiang Lake Big Data Industry Development Promotion Center.

After pumping up the lake water, plate heat exchangers and pipelines are used to bring the cold air carried by the water to cool down the equipment, Kuang said, keeping the temperature inside the data center between 18-27 C, which is optimal for the function of the equipment.

The water, after finishing its job in the data center, is returned to the downstream river, with its temperature rising only by 2-5 C, aligning with the river's natural thermal rhythm, Kuang said.

Most importantly, the entire process is pollution-free and does not affect water quality, he added.

"For 99 percent of the year, we rely entirely on lake water," he said. Traditional chillers like compressors are activated only under extreme conditions, such as flooding, when water quality or temperature becomes unsuitable for natural cooling.