Lake water tames data center heat

An internationally adopted key metric for data center efficiency is power usage effectiveness, or PUE, calculated by dividing total energy entering a facility by the energy used solely for IT equipment. A lower PUE indicates better efficiency, meaning less energy is spent on overheads like cooling and lighting, with a PUE of 1 being the optimal figure.

According to the Uptime Institute Global Data Center Survey 2024, the industry average PUE for data centers worldwide stands at 1.56, meaning that for every watt powering a server, an additional 0.56 of a watt is consumed in overheads.

Through its eco-friendly cooling system, the Dongjiang Lake center achieves an annual average PUE under 1.2. Compared to a data center with a PUE of 1.5, it saves more than 25 percent more energy, according to data from the center.

However, the center still faces pressure to reduce electricity costs while enhancing its green credentials, said Tang Ling, director of the center. To tackle this challenge, the center has explored ways to deploy more renewable energy resources.

Photovoltaic panels have been installed on the rooftops of the center's buildings, converting sunlight into clean power, feeding directly into operations. The center is also working on research projects to integrate more wind and photovoltaic power from nearby areas into its grid, Tang said.

To enhance energy efficiency, innovations at the center extend beyond cooling.

In 2021, the center launched a waste-heat recovery demonstration project with local government and research teams from institutions like Hunan University and Central South University in Changsha. Instead of discharging warmed lake water directly back to rivers, the project aimed to collect and reuse excess heat produced by the cooling process.

In 2023, the team developed a system to capture waste heat from the return side of the water pipelines used for cooling servers and put it into operation. This recovered thermal energy is used for winter heating in the data center's office area.

"Compared to traditional heating solutions, this system provides a 50 percent energy saving," Tang said.