Scheduled for completion in 2009, the 71-story, 2.3-million square-foot tower will be the most energy efficient supertall tower ever built, claims SOM.
In fact, there were rumors this building was going to be a “net-zero” building, i.e. it would produce as much energy as it consumed on an annual basis. Unfortunately, this relies on being able to “run the meter back”, or sell energy back to the grid at times when the building is producing more energy than it is consuming. The infrastructure and laws in Guangzhou do not yet allow for this, and therefore the key on-site microturbine co-generation system was scrapped. However, SOM did design the building to allow for the microturbine to be installed as Gaungzhou updates their grid policies.
Despite the fact that the building won’t be truly net-zero-energy, it will still be a showcase project for energy efficiency and onsite generation, both to China and the world. SOM made energy efficiency the core of their design, and designed the entire building around this goal. As Roger Frechette, Chief MEP Engineer of SOM told us at Greenbuild,
“Form for the sake of form is no longer good enough. Form now has to be apart of the performance of the building. The whole building should be built as a single unit that has a better level of performance than we’ve seen before.”SOM’s design process really took Mr Frechette’s principles to heart, using a four-pronged, whole systems approach to get to net-zero energy use:
Source: Architectural Record case study (good source for more info on the specifics of the building design)
1) Reduce- use “negawatts” as the primary energy source
2) Reclaim- take the waste from various processes and use it as inputs for other processes
3) Absorb- take advantage of the local climate for wind, solar, daylighting, etc
4) Generate- meet whatever energy needs remain with microturbines and co-gen
The building’s unique shape allows it to harness wind power more effectively. Tall buildings act as a sail, with wind pushing against them. In standard buildings, the designers use more concrete or steel to stiffen up the core to withstand the wind force. In the Pearl River Tower, by contrast, the openings on the side of the building allow wind through, which has the dual effect of relieving pressure on the building and driving wind turbines mounted in the throat of the openings. According to SOMs calculations, this design also reduces the sway at the upper portion of the building, allowing for less material to be used while still maintaining safety and comfort levels, reducing the building’s embodied energy that I keep harping on (please note however that the designers did not take advantage of this, but theoretically could have). The Pearl River Tower also uses building integrated photovoltaics (BIPVs) embedded in the glass curtain wall to produce energy.
Unfortunately, these systems can’t power the building on their own. Together, these technologies provide less than 10% of the buildings power. But the developer wanted them because they served as a powerful symbol. As Mr Frechette recounted:
“I asked the developer what he thought about the wind turbines. The developer asked, “do they spin?” and I said they did, and he said, “then I like them.”He added that Guangzhou is a city of 15 million people and wind turbines on wind building won’t begin to dent the overall energy use, but hopefully other developers and owners will see these working wind turbines as a symbol. If every owner did this, it really would start to make an impact.
Given all the cool features and the incredible energy efficiency, this building must have cost a fortune, right? Not so. The building cost an extra 100MM RMB ($15MM) to build. Based on average construction prices for Class A office in China, this equates to ~10% premium.
SOM claims the investments in energy efficiency have a payback of 4.8 years. Not bad for a building a building that will have a lifetime of at least 50 years.
Why were the designers able to get so much energy efficiency with so little additional upfront cost? Because they tunneled through the cost barrier! This building is a great example of how proper whole-systems thinking can add value, both environmentally and economically.
SOM turned the conventional design model on its head. Instead of starting with a design that meets code and then slapping green features on as the budget allowed, they started with a design that was net-zero-energy and then removed the more expensive green features (ie microturbine co-gen) to get to the point that their budget allowed. They also smartly designed the building so that the microturbine co-gen can be added in the future as policy or economics change.
Radiant cooling was a cool example of how whole-systems thinking can add serious double bottom line value (good intro to radiant cooling). Radiant cooling uses significantly less space than more typical variable-air volume cooling while providing the same (or even higher) levels of comfort and less energy. Because the radiant cooling system uses less space, SOM was able to design five more floors into the building! That results in about a 7% increase in rentable floor area, which pays for the more expensive radiant cooling system. So radiant cooling not only provided better comfort with less energy, but also paid for itself through extra rentable space. That’s powerful stuff.
I don’t want to sound like I’ve drunk too much SOM Kool-Aid, but the design process is pretty exemplary. However, they are not the first to do this though, Bill Reed, RMI and other visionaries have been talking about the deeply integrated net-zero design approach for years. But SOM is one of the first to take this cutting-edge approach and apply it to such a landmark building. And for that, they deserve our kudos.