Sustainable Tall Building Design: Pearl River Tower

Sustainable Tall Building Design

A brief case study of the Pearl River Tower in Guangzhou, China

Objectives

This interactive lesson provides an overview of the sustainable tall building design as applied to the Pearl River Tower, and answers the following questions:

• What makes buildings "tall"?
• What is the LEED standard?
• What sustainable design technologies does the PRT feature?
• What is a "zero-carbon" building?

Overview

When completed in 2013, the Pearl River Tower set a benchmark for the ecological design of supertall towers, which are commonly defined as occupied buildings higher than 300 meters (984 feet). According to SOM, the architecture firm that designed the building, this 71-story tower is the "result of careful site research that incorporated the latest green technology and engineering advancements in order to harvest wind and solar energy." What inspired SOM most was the opportunity to do a completely carbon-netural, or "net-zero" bulding. What this demanded was a design approach that was not only uniquely local and form driven, but also performance based.

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Energy Performative Design

These considerations formed a simple set of principles as the basis for what the architects deemed ‘energy performative design’. Namely, these were four interdependent strategies to reduce, absorb, reclaim, and generate energy for the building, The ultimate goal was to achieve carbon neutrality, or ‘net zero energy’ as it’s commonly referred to.

Sustainable Technologies

From this jump off point, the architects considered how to integrate a series of sustainable and engineering elements into the design, each of which would enhance the building’s overall energy efficiency. A substantial part of this strategy would include the use of a double curtain wall system and high performance façade, as well as state-of-the-art wind turbine technology, photovoltaics, radiant celings, and daylight harvesting among others. Together these tools allowed the architects to achieve LEED Platinum status for the Tower.

Putting the Wind to Work

Early on, SOM looked to a variety of analytical and advanced energy modeling tools to set the highest benchmarks for how well they expected the building to perform. During testing, it became apparent that Guangzhou’s local climatic conditions should play a key role in the design approach— especially wind.

Wind played a role not only in terms of energy performance, but at the conceptual level. In fact it was essential for all of the building’s systems to have a degree of interdependency, to avoid superfluous architectural detailing. So by putting the wind to work, SOM was able to come up with leaner design for the architectural and engineering solutions.

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Putting the Wind to Work

From a structural perspective, these illustrations show how vortex shedding around the sides, and over the top of the building, creates a large pocket of negative pressure on the leeward side of the building. So by allowing air to pass through the building at upper and lower openings, designers were able to reduce differential pressure from front to back, while forces on the building are, in turn, reduced. This approach is sustainable from a structural standpoint, in that it allows for a reduction in the quantity of steel and concrete to maintain the building’s stability.

Wind Turbine Generators

Together these characteristics were vital to the implementation of wind turbine generators. The shaped inlet on the right picture, which SOM ended up using, proved to increase velocity by two-an-a-half times. This also the architects to take advantage of the fluid dynamic shaping, and decreased pressure drop, into the turbine as wind passes through, including the pressure differential experienced between the front and back of the building.

Double Skin Facade

From wind and solar behaviors, SOM then considered the advantages of a double envelope for the building, which would accommodate venting and solar shading devices within the cavity. The transparency of the wall brings aesthetic benefits as well.

But functionally it allows control over daylight into the space, along with infiltration of moisture and air into the interior. At the same time it reduced solar heat at the building’s perimeter, where spaces are typically occupied, and improved the building’s thermal performance during seasonal changes.

Glazing and Solar Shading

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Automated Blinds

These solar-responsive controls are in turn integrated with motorized blinds on the exterior wall. On he left you see them fully extended; but they are intended to open, close or angle at 45 degrees. Their position determined by a photocell that tracks sun position, and connects to the building management system, which then activates the blind position to ensure occupancy comfort from both solar gains and glare.

Radiant Cooling & Floor-Fed Ventilation Systems

The architects' commitment to this type of exterior enclosure for the Pearl River Tower was its potential to serve as an internally ventilated double wall system. At the bottom left one can notice the clear tempered glass panel with a low-E coating, which can be easily opened for maintenance. At the same time these panels complement the interior walls that mechanically ventilate every floor.

Improved Net-to-Gross Area

These systems also played a significant part in allowing both the architects and developers to improve the net-to-gross area of the building. As an example, the elimination of fan rooms, and reduction of air shaft sizes, meant that the core area was further reduced. Specifically, this meant a reduction of the building’s “floor-to-floor” height from 4.2 meters to 3.9 meters, which resulted in about 8% less core per floor, thereby increasing the building’s revenue potential. A conventional system would have made this approach impossible.

Improved Net-to-Gross Area

Furthermore this didn’t compromise the floor-to-ceiling height within the space, and reduced exterior envelope costs. This is equivalent to a savings of about five stories of construction, or adding a little over nine thousand square meters of space. Naturally the economic benefits from this are susbstantial. In fact, due to decreased energy and capital costs, as well as revenue generated by additional floor space and efficiency, it was estimated the tower would: Return initial investment costs in about 20 years, and begin to pay back on these costs within four to six years.

For more information on SOM, click here:

Toward Zero-Carbon

From the inception of "energy performative design", SOM applied a consortium of sustainable design technologies to achieve one of the world's first "carbon-neutral" supertall buildings. Together these included an array of solutions that could optimize system efficiency and commissioning:

• Energy reduction through double wall high performance glazing;
• Radiant floors and other high efficiency equipment and lighting
• Reclamation through heat recovery strategies
• Natural ventilation and integrated PV’s to absorb energy
• Fuel generation using on-site microturbines

Additional Information

To watch a documentary on the design and construction of the Pearl River Tower, click below: