JINAN — Amid the frigid winter of the Yellow River estuary, resident Xing Yan enjoys the warmth at home where his orchids thrive. This comfort is not provided by a boiler, but by harnessing geothermal energy found almost 2 kilometers beneath the surface of the Earth.

Xing lives in Niuzhuang township of Dongying in East China's Shandong province. Deep beneath the seemingly ordinary town lies a powerful heat source where water temperatures reach as high as 85 C.

Upon entering the town's heating facility, an immediate surge of warmth can be felt, thanks to a huge plate heat exchanger in operation. A heat exchange takes place between hot water of 82 C and cold water, resulting in water with a temperature of about 60 C being sent to the town's heating pipelines.

The geothermal heat from underground is transformed into clean energy that benefits local residents and supports industries, turning Niuzhuang into a warm, smog-free town.

Geothermal heating is used in all 13 urban residential compounds of the township, three rural residential areas and more than 60 institutions in Niuzhuang. This 750,000 square meters of heated space represents 98 percent of the town's total area, and benefits over 7,000 households, or around 22,000 people.

The system helps save 34,000 metric tons of standard coal annually and reduces carbon dioxide emissions by approximately 80,000 tons.

As a clean, renewable energy source derived from heat within the Earth, geothermal energy's greatest advantage is its stability. Unlike wind or solar power, it is unaffected by external factors such as seasons, climate or day-night cycles. At the greenhouses of Shandong Shuangfu Flowers Co, located in the town, moth orchids grow healthily year-round in an environment maintained at about 26 C.

Li Binghai, general manager of the company, said its heating costs dropped by 15 yuan per sq m after switching to geothermal heating, making it 25 yuan per sq m cheaper than coal heating.

"The geothermal system provides a stable temperature for our greenhouses, which cover 100,000 sq m, saving us more than 1 million yuan ($143,500) annually in energy costs," he said.

"Geothermal heating not only cuts costs but also enhances stability," Li said, adding that winter heating is a major challenge for flower cultivation in North China.

In the past, coal heating caused temperature fluctuations, requiring constant manual monitoring. Now, with geothermal heating, the temperature can be controlled via smartphone, extending the flowering period of moth orchids and providing stable conditions for developing new varieties. The company exports flowers to countries including Vietnam, Russia and Uzbekistan.

Shang Xinjian, director of the town's construction service center, said Niuzhuang is a demonstration model for the multi-tier utilization of geothermal heat.

Hot water around 80 C is extracted from 1,950 meters underground, with heat exchange equipment then used to warm residential compounds via this source.

The temperature of the tailwater drops to around 50 C, which is routed to the modern agricultural industrial park to heat greenhouses used for growing flowers, fruits and vegetables. Finally, the cooled tailwater is re-injected underground via wells, completing a closed-loop system that conserves both heat and water, according to Shang.

In China, geothermal energy, a stable and controllable form of renewable energy, has been developed for large-scale deployment and diversified applications.

According to figures from the China Geological Survey, hydrothermal geothermal resources in the country are equivalent to 1.25 trillion tons of standard coal, while the annual exploitable amount is equal to 1.86 billion tons of standard coal. China has led the world for many years in terms of the utilization of geothermal energy.

In Niuzhuang, plans are being made for using geothermal energy in the drying of agricultural products and in aquaculture, helping to establish a complete industrial chain that integrates high-end farming, breeding, processing and leisure.

"The underground treasure trove of geothermal energy will bring more warmth and opportunities to our town," said Song Ke, deputy Party chief and government head of Niuzhuang.

Xinhua