Cases of Study

Net Zero Energy Buildings

Case study: Pearl River Tower, Guangzhou, China

Tall buildings (skyscrapers) typically consume an average of 22.5 kWh per square foot which is equivalent to 242.2 kWh per meter square. This is according to the department of energy DOE, USA, reports for commercial buildings. Based on those numbers of energy consumption it is obvious that a lot of energy is needed for a tower with a total gross area of 2.2 million square feet which in turn increases carbon emissions. So, The crucial role of architects and engineers is to design more sustainable buildings that ensure less energy consumption both real and embodied. The following graph shows where the energy is consumed in the commercial buildings.

The Story of “ Net Zero Energy” building:

Skidmore, Owings, & Merill(SOM), LLP, An Architecture and Engineering firm was hired to design the most efficient super tall building in the world,  by  Guangdong Tobacco Company (GTC)  one of the largest companies in Guangzhou and a part of the Chinese National Tobacco Company. 

SOM’s design for the 71-story Pearl River Tower in Guangzhou, China, was selected in a 2005 competition and completed in 2013. 

The city of Guangzhou, China experiences worse air pollution due to industrial development. The Chinese government set a goal to reduce their carbon emissions by 10% by the year 2010. 

Net Zero Energy Definition:

Each community needs a certain amount of energy for transportation, industry, utilities, and buildings. 

The Project designers of SOM defined the Net Zero Energy  of a new  building as “ a structure that does not require an increase in the community’s need to produce energy” 

Furthermore, they need to keep the power generation stable for the community while the community can expand and grow without needing to consume more fossil fuels. 

This was the initial concept of the design but it changed due to some economic considerations and regulatory challenges like canceling the use of 50 microturbines to generate the remaining power of the building due to regulations of the government of Guangzhou. These regulations do not allow to merge of the excess generated power to the city’s electric grid. 

Despite these design modifications,  The building will be a high-performance and most energy-efficient super tall tower in the world when it is completed as the design team mentioned. This is because of using a variety of sustainable passive and active measures, to reduce the dependency on the city’s electric grid. 

Implementation Approach of the Concept: 

The design team studied the site location to identify possible energy resources both passive and active and took into consideration the key elements of successful high-performance building like:

  • Site Analysis.

  • Building Orientation.

  • Wind Direction.

  • Sun Path. 

The implementation approach has four Independent steps  that would lead to  the net zero-energy including: 

  • Reduction

  • Absorption

  • Reclamation

  • Generation

In this article, we will describe only reduction, absorption, and reclamation because the step of generation is canceled. 

Reduction is associated to reduce energy consumed by main power consumers like Heating, Ventilation, and Air Conditioning system ( HVAC) and lighting system. 

This is done by using :

1. Active double-wall facade for mechanical ventilation also the trapped heat energy by it uses in the dehumidification system.

2. Triple glazed facade at East and West sides.

3. Chilled Radiant ceiling for Air conditioning.

4. Radiant Panel Geometry for the lighting system.

Absorption is associated to increase the use of energy sources available around the building like solar and wind energy. 

This is done by using:

Integrated Solar Photovoltaic (PVs) that are located on the building’s vaulted roof glass and incorporated into the sunshade devices. These PVs provide about 200,000 kWhr/year for the building’s electricity and protect it from solar gain.

PV panels are located on the domed roof.

Vertical Axis Wind Turbines, located on 4 openings at the two mechanical floors.

These 4 openings are designed to accelerate the wind speed by a factor of 2.5 of the average wind speed of 5.3 m/s at a height of 300 m in Guangzhou. This resulted in an 8 times increase in the generated power when compared to turbine installation in an open field.

Four Turbine Funnels with Air streamlines

Daylight Harvesting using daylight response control integrated with an actuated double skin wall system to provide enough natural lights to the building interiors. Meanwhile, the sensors of the day light-harvesting system reduce the levels of the electric lighting to achieve better energy-saving and proper visual comfort.

Reclamation is associated with the reuse of the already added energy in the building to be used over and over again in preheating and cooling of air used in ventilation.

Conclusions: 

  • Pearl river tower is a highly integrated architectural, structural, and mechanical solution.

  • The tower design saves about 30% of energy compared to the Chinese baseline energy code. 

  • The unique shape of the tower draws attention to its VAWT but the most energy-saving is due to the combination of sustainable measures. 

  • The tower enhances thermal comfort, natural lighting, ventilation, and acoustics that improve human productivity. 

  • The tower’s combination of sustainable measures enhanced space-saving by eliminating ductworks, fan coils, insulation, and other items. That reduced the cost of these components.

References: 

References and Links:
[1] Frechette, Roger E. and Russell Gilchrist. “’Towards Zero Energy’ A Case Study of the Pearl River Tower, Guangzhou, China.” (2008).
[2] Tomlinson, Richard, William F. Baker, Luke K.-P. Leung, Shean Chien and Yue Zhu. “High Performance Design Shapes Sustainable Supertall Building.” (2014).
[3] https://www.skyscrapercenter.com/building/wd/454
[4] Pearl River Tower, Guangzhou – Megastructures: China’s Smart Tower – China Engineering Documentary
[5] Building Green – Power Tower