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Saturday, July 28, 2012

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Cutting edge: A Yamazaki Mazak Corp. (left) worker strolls near the entrance building and air inlet channels connected to the company's underground factory. KYODO PHOTOS


Geothermal benefits become clear underground

Chunichi Shimbun

A pyramid-shaped, 5-meter-high glass building stands on the hilly forest terrain of Minokamo, Gifu Prefecture.

News photo
A passageway cools air as it comes down from the surface.

This is the entrance to a laser processing machine assembly plant operated by Yamazaki Mazak Corp., one of the large machine tool manufacturers based in Aichi Prefecture.

Accessible by elevator, the factory is 11 meters underground and covers an area of 10,000 sq. meters.

Built in 2008, it is believed to be the largest underground factory in the world.

While the temperature above is a sweltering 35 degrees, the factory maintains a moderate 26. The workers, in white uniforms, look comfortable as they assemble the machines.

The temperature doesn't often have to be adjusted regardless of the season, thanks to the use of geothermal energy, which creates a "natural air-conditioning system" that eliminates the need for air conditioners or heaters.

At around 10 meters underground, the temperature is about 15 degrees in Japan. It remains relatively constant all year long, meaning it's cooler than above ground in summer and warmer in winter.

This temperature difference is used as a source of heat energy, such as in heat pump technology where water flows down a pipe from the ground level that is heated using geothermal energy.

For Yamazaki Mazak, the original idea behind building an underground factory was to reduce the amount of dust in the air to just 5 percent of what it would be above ground. Optical components such as lenses and mirrors are crucial to laser processing machines, but they get dusty and dirty easily. Placing the assembly underground means there would be less exposure to airborne particles.

The company achieved its goal, but then after the Great East Japan Earthquake in March 2011 it started getting more public attention for a different reason. By putting the factory underground, Yamazaki Mazak managed to reduce its electricity bill, including for air conditioning, by a staggering 90 percent.

This success in energy conservation led to greater awareness of the benefits of geothermal systems. In the first three months following the earthquake, the number of visitors to the factory increased by 50 percent, most of them coming from manufacturing companies.

In the case of the Yamazaki Mazak factory, hot summer air enters the inlet channel and travels 500 meters through a 70-cm-wide, 5-meter-tall passageway, which cools the air sufficiently before it reaches the factory rooms. The heat from the factory rooms is in turn released into the air outside through ventilation outlets. This keeps the interior temperature below 28 degrees.

The factory does have air conditioners, but they are used only when necessary and only in the design room, where most of the workers are. The plant relies solely on ventilators the rest of the time.

In winter, the temperature outside falls below zero, but the factory remains a comfortable 18 degrees. Over the course of a year, the company uses 84 percent less energy on air conditioners and heaters than comparable factories above ground.

"Some of our workers who suffered from allergy and hay fever symptoms say their conditions have eased. Even without air conditioners, the air is fresh and cool. It is so pleasant that sometimes I feel as if I am in the highlands," said Yamazaki Mazak Vice President Norihiko Shimizu, who was involved in constructing the facility from the start.

Despite the many benefits, one problem remains with building an underground factory — it is extremely costly. Although Yamazaki Mazak tried to reduce the digging work by making use of the hilly terrain, total construction costs still came to ¥3.5 billion, almost 20 percent more than a similar factory above ground.

Making up for the extra construction cost through reduced electricity bills is going to take 20 years. Shimizu said most visitors grow hesitant when they hear about the huge building tab.

"But we had decided to focus on producing the highest quality of products possible. It has become our company's advantage since it is not something that other companies can copy," he explained. "It is very likely that we will build our next factory underground as well."

This section, appearing Saturdays, features topics and issues from the Chubu region covered by the Chunichi Shimbun. The original article was published July 19.

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