Baoshan energy park uses geothermal pumping system

By Zhang Qian  |   2009-1-13  |     NEWSPAPER EDITION

HANGING food above cool water in a well used to be one of the most popular ways to keep it cool in summer, and so did blocks of ice for ice boxes in the days before refrigerators that ran on electricity.

Now that old approach - using the constant temperature of underground water - is again being used today for air conditioning.

The idea of the small well has been enlarged to more than 10,000 square meters in northern Shanghai's Baoshan District.

In an energy conservation center in Baoshan, you can see a line of round holes in the wall of the conference hall.

It's air conditioning for the Shanghai International Energy Conservation and Environmental Protection Park.

It blows out warm air in winter, cool air in summer.

This new environmentally friendly air conditioning consumes little electricity (some equipment uses electricity) and does not generate pollution.

The secret lies under the 3,500-square-meter lawn in front of the building, according to Ye Ying, director of the Economic Committee of Baoshan District and a research fellow at the China Academy of Management Science.

Just a few months ago, the area was bare earth. More than 200 small connecting wells, 6-10 centimeters in diameter, were being drilled to a depth of around 85 meters.

One end of a U-shaped tube goes into one hole and comes up through another hole. The tubes are filled with water and heated in the earth.

At the surface, the tubes are connected with a compressor, a condenser, an evaporator and other equipment that raises and distributes warm water and air.

Everything is linked to rooms in the building through other pipes.

Together this represents one of the most environmentally friendly air-conditioning systems in the world ?? a geothermal heat pump, or geo-exchange system.

A geothermal heat pumping system draws energy from the ground where the temperature is stable between 10-16 degrees Celsius, and warms air for rooms.

Despite the name "geothermal heat pump," the energy comes from ground that is heated by the sun, not the earth's core that is far deeper. The local climate determines the temperature of the ground.

"The temperature of underground water and soil won't be influenced by changing weather," says Ye. "Even though it is below zero centigrade on the surface, the soil in the deep area keeps warm. So we borrow some zero-cost heat from the earth."

The tubes buried in the earth under the lawn are kept warm and the water inside is recycled.

Clean surface water of normal temperature flows to the deep layer of the earth through the tubes, exchanges heat with the soil there and travels back to the surface again.

The water in the heat exchange system is used to create warmer air that is blown into rooms at comfortable temperatures in summer and winter.

The geothermal heat pump at this energy conservation park (Phase 1) provides heat for structures within the 19,000-square- meter area, including the conference center, exhibition center and an office building.

It provides cold water of 7-12 centigrade in summer and warm water of 40-45 centigrade in winter to the air-conditioning system, which helps keep the temperature of the air-conditioned rooms below 26 centigrade in summer and above 18 centigrade in winter.

Regardless of the weather above ground, the system works effectively.

"Ordinary household air conditioners may not work when the temperature is below freezing, but a geothermal system can still keep the room at about 20 degrees Celsius and prevent freezing," says Ye.

The engineers added a cooling tower, usually absent in other geothermal heat pumping system. With the cooling tower, says Ye, people can control the temperature of the air sent to the room as accurately as a regular thermostat.