Builders of Tokyo Skytree, the 65 billion yen ($656 million) broadcast tower almost double the height of the Empire State Building, say they aim to make their mark on more than just the Japanese metropolis’s skyline.
A combination of heat pumps and water tanks for its district heating and cooling systems aims to reduce carbon emissions as much as 48 percent compared with similar projects without a centralized system, said Shinichiro Konno, the managing director of a company that helped develop Skytree.
The complex, the world’s largest broadcasting tower at 634 meters (2,080 feet), reflects pressure to conserve energy across Japan since the tsunami triggered by an earthquake in March 2011. That disaster led to a meltdown at the Fukushima Dai-Ichi nuclear power plant, prompting the shutdown of all except two of the country’s 50 atomic reactors.
“Having a central system for heating and cooling increases efficiency,” Konno, an executive at Tobu Energy Management Co., which is a unit of Tobu Railway Co., said in an interview. “We’ve installed highly efficient machines that use Japanese technology.”
Tokyo Skytree, which was under construction before the earthquake, has the first district heating and cooling plant in the nation using a ground-source heat pump.
Opened to the public in May 2012, the broadcast tower has become the newest landmark in Tokyo, eclipsing the 333-meter Tokyo Tower. Dubai’s Burj Khalifa is taller than Tokyo Skytree, which towers over the Empire State Building’s 381 meters, according to the Council on Tall Buildings and Urban Habitat.
Since opening, the broadcasting tower had attracted about 5.5 million visitors by the end of March 31, according to a statement by Tobu and two other companies. Operators had initially expected 4 million visitors for the same period.
The heating and cooling systems at Skytree produce and distribute hot and cold water to the tower as well as shops, restaurants and offices in the 10.2 hectare area, located 5 kilometers (3 miles) northeast of Tokyo’s central train station, Konno said.
Mitsubishi Heavy Industries Ltd., Ebara Refrigeration Equipment & Systems Co. and Kobe Steel Ltd. supplied heat pumps and centrifugal chillers to produce heated and chilled water.
Four water tanks inside the plant augment the area’s energy efficiency, Konno said. The 16-meter tanks allow operators to store cold and hot water produced at night when off-peak electricity rates are lower and then to use the water in daytime when demand is higher.
Tokyo Skytree is among 141 areas in Japan authorized to distribute heat under the country’s Heat Supply Business Act, according to the Japan Heat Supply Business Association.
District heating and cooling is widely used around the world. As of 2009, Russia had 173,100 kilometers of underground pipes used in such systems while China had 110,490 kilometers, according to Euroheat & Power, an organization promoting district heating and cooling. Japan had 736 kilometers of underground systems, the organization’s research shows.
“It is not widely used outside Tokyo,” said Yoshiyuki Shimoda, an environmental engineering professor at Osaka University. “This is something that can only be introduced when there is large demand for urban development and there is a plan for large-size development,” he said in a phone interview.
Instead of setting up cooling and heating systems for individual buildings, a central plant is built with boilers, heat pumps and refrigeration facilities to produce hot and cold water, which is distributed through pipes.
Skytree’s systems, which cost about 4 billion yen, are estimated to use 44 percent less primary energy a year compared with having individual systems for the area covered by the project, according to Konno.
Heat pumps draw heat from the air, the ground or water. The use of ground-source heat pumps is increasing in Japan, according to the Ministry of the Environment. The number of sites that installed such devices jumped 43 percent to 207 in 2011 from the year before, bringing the total number of locations to 990.
Ground-source heat pumps are suitable for small buildings and homes as they extract less heat than devices using the air or water, according to Shimoda.
“Skytree is getting lots of attention so it is a good place to raise the profile of ground-source heat pumps for a wider use,” the professor said.