The Pearl River Tower in Guangzhou, China is designed to be the most energy efficient supertall skyscraper in the world. Some key energy efficient design features include wind turbines and solar panels integrated into the building, a double and triple glazed facade, radiant cooling systems in the ceilings, and a building shape that channels wind to the turbines. Early results indicate the tower will use an AC system 80% smaller than conventional skyscrapers and the turbines may generate up to 4% of the building's power needs through wind energy harnessing.

1. Pearl River Tower, Guangzhou, China A Case Study by … Namita Kandeyang Khuketolu A. Kibami Sujitesh Pillay

2. A Brief Introduction… Location… Guangzhou, China Architect… Gordon Gill, SOM (Skidmore, Owings and Merrill) Height… 310 m (1017 ft) No. Of Floors… 71 Floor area… 212,165 m2 (2,283,725 sq ft) Use… Office and conference Distinction… Designed to be the most energy efficient super tall tower in the world

3. Innovative Structural Techniques… The 71-story, 2.3-million square-foot tower, when finished, will be the most energy efficient super-tall tower ever built, and a milestone along the way to energy independence, and not having to rely on the city's infrastructure for power. The building has been designed to include wind turbines and solar collectors, photovoltaic cells, raised floors ventilation, and radiant heating and cooling ceilings. Even its location is designed to take advantage of wind and solar patterns in the region. It is south facing and features funnel style breaks in the facade that focus wind on integrated internal wind turbines. It has integrated photovoltaic panels that — along with the energy from the turbines — keep the heating, ventilation and air conditioning systems energized. There are also motorized louvers on the facade of the building that rotate to keep the building cool and provide fresh air ventilation. Although the building still isn't finished, it has already racked up several accomplishments including being the largest radiant-cooled office building in the world, the most energy efficient super-tall building in the world and a towering (no pun intended) example of China’s goal to reduce the intensity of carbon dioxide emissions per unit of GDP in 2020 by 40 to 45 percent as compared to the level of 2005.

4. Cooling from above, air from below…

5. Of all the elements in pearl river tower’s energy efficient design, the radiant cooling system is the biggest energy saver. In this system water flows through ceiling panels and provides cooling from there. The system will be the largest radiant cooling system in the world.

6. Energy-Efficient Walls The tower incorporates a double skin curtain wall on the northern and southern facing facades – which is essentially a pair of glass “skins” separated by an internally ventilated eight-inch air corridor that acts as insulation against temperature extremes. Instead of transferring through to the interior of the building, heat from the sun is trapped in the cavity and rises to heat exchangers on the equipment floors where it can be used for passive dehumidification and supplying hot water. The east and west elevations will feature a triple glazed facade with external shades and automated blinds within the glazing cavity. Meanwhile, solar panels on the roof of the building provide power to perforated metal window blinds inside the glazing cavities that automatically track the sun and open and close to minimize solar heat. These systems help the Pearl River Tower to cut its cooling needs and let it use an air conditioning system 80 percent smaller than those of comparable conventional skyscrapers. Solar collectors integrated into the building facades also transform the sun’s energy into usable AC current. Other eco-friendly elements contributing to the building’s energy efficiency include under floor ventilation air, daylight harvesting and a ceiling system that incorporates chilled water piping to cool rooms by natural convection and radiation heat transfer. The building was also meant to have a geothermal system, but the site didn’t generate enough warm ground water for it to work.

7. Solar Electrical Generation… The Pearl River Tower uses both “Building Integrated Photovoltaics (BIPV)” and wind power to meet the energy demands of the building. The BIPV will be incorporated exclusively on the south façade of the building. Since photovoltaics provide no benefits at night and limited benefits on overcast days, an intensive wind turbine system has been incorporated into the building.

8. Wind Electrical Generation… What makes this building stand out is its unique integration of wind turbines into the maintenance levels of the building and the sculpting of the building form to channel wind through those openings. Vertically, the building profile is pinched at two points corresponding to mechanical floors for the building. The openings and curvature also relieve stress from wind loads.

9. Darreius Rotors… Unlike traditional wind turbines which are only 10 – 20% efficient at capturing the energy of the wind propelling them. Darreius rotors are 35% efficient at capturing the energy of the wind and are the type incorporated in the Pearl River Tower. Darreius rotor Typical wind turbine

10. Integrated wind power The pearl river tower’s wind design is based on a small turbine (almost 10 feet or 3 m in diameter) by English manufacture quiet revolution. Each of the designs four turbines has a rated performance of 10,000 kWh per year. Air is pulled through the building, accelerating the speed of the wind by more then 2 times and increasing it’s power potential by a factor of 8. Turbines are estimated to provide 1% of the buildings energy need.

11. The shape of the building is designed to ensure the wind turbines will generate power in relatively mild winds from multiple directions. Wind studies conducted by SOM have predicted the turbines will speed up the wind’s velocity two-and-a-half times. Tested in winds up to 140 mph, the turbines are expected to generate up to four percent of the building’s power requirements and will be used to dehumidify the building. Its distinctive sculpted body is designed to direct wind to the pair of funnel-like openings at its mechanical floors, which are located roughly one third and two thirds of the way up the building. As the wind flows through it pushes the building’s integrated wind turbines to generate power for the building’s heating, ventilation and air conditioning systems.