Advanced wind engineering for a supertall skyscraper that generates its own wind power
The Pearl River Tower is a 71-storey skyscraper located in Guangzhou, China, a port city about 75 miles from Hong Kong. The building was designed with energy conservation as an overriding imperative. It incorporates a range of energy-saving features including a double-skin façade, underfloor air ventilation, and radiant cooling. The tower also harnesses solar and wind energy to reduce the amount of energy it needs to draw from the city’s grid.
One of the tower’s most innovative features is the integration of wind energy generation into the design of the building itself. The building contains four openings – two each on two mechanical floors – that allow wind to pass through the core of the building. Turbines inside the four openings convert wind energy to help meet the building’s electricity needs. The Pearl River Tower’s designers, Skidmore, Owings & Merrill (SOM), engaged us for help optimizing the efficiency of their design and maximizing the energy the building would be able to harvest from its built-in wind turbines.
Our wind engineering team has decades of experience delivering analysis that helps tall buildings perform well in diverse wind conditions. This project was unique because we not only had to develop a rich, detailed understanding of how the wind would act on the tower; we also had to understand and refine the aerodynamics of the building form so as to maximize the energy-production capacity of the building-integrated wind turbines.
Our input helped size and place the turbines and provide recommendations to SOM for turbine selection – considering maintenance, noise and vibration issues. We also used both wind tunnel testing and computational fluid dynamics (CFD) modeling to understand how wind would flow around and through the building. Having gained a baseline understanding of these flows, we began to test various sizes and placements for the four openings, as well as refinements of the tower’s shape, to determine which designs would most efficiently increase the wind’s velocity through the turbines.
In conventional wind turbine installations, the turbines are out in the open and wind can move around the rotors unrestricted. By contrast, the Pearl River Tower’s turbines needed to operate in enclosed spaces within a larger structure. To optimize the efficiency and energy-generating capacity of the turbines in this unusual context, we had to perform testing and modeling to gain deeper insight into a number of factors. One factor was that, in addition to the pressure the wind would exert directly on the turbine, there would be other pressures generated by the overall building form: wind generates buffeting positive pressures on the windward side of the building, and a negative, highly turbulent pressures in the wake that forms on the leeward or downwind side. A second factor was that the enclosed channel had the potential to funnel wind flow through the turbine; this made it possible to boost the turbine’s energy production. Third, a boundary layer would be created at the edges of the channel containing the turbine; we needed to understand the risk that this phenomenon would interfere with the operation of the turbines.
Ultimately, having gained a complete picture of all the various wind effects on the building, including its four open channels and the turbines inside, we were able to work with the designers to create a form that would effectively function as a wind scoop, doubling the velocity of the wind as it reached the turbines. Typical wind speed in Guangzhou at the elevation of the planned turbines is about 9mph; our design directed the wind toward the openings in such a way that the air is sucked through the turbines at a velocity of 18mph. At that velocity, the turbines’ power generation potential was more than amplified eight times that of a stand-alone generator.
The Pearl River Tower has been operating successfully since its completion in 2011. It is generally recognized as one of the most efficient and environmentally friendly tall buildings in the world. It was among the first tall buildings on earth to earn LEED Platinum, the highest level of LEED certification. It’s estimated that the building’s sustainability features cause it to use approximately 30% less energy than other similar structures.
The tower won an Award of Excellence in Sustainable Design from the Structural Engineers Association of Northern California, was recognized by MIPIM Asia, a real estate association, as the Best Innovative Green Building in 2013, and was a finalist for the Council on Tall Buildings and Urban Habitat’s award for Best Tall Building in Asia & Australiasia (2013).