c a s e S t u d y P e a r l R i v e r T o w e r How Far Can You Go?

B y K y r a e P s t e i n

G uangzhou, China, has leaped the hurdle of energy-efficient buildings with a single bound,

moving into a new era of efficient super-tall towers.

The port city of 6.6 million, about 100 miles from

Hong Kong, will soon have a new symbol of prog-

ress — a 71-floor office tower using wind turbines,

photovoltaics and about 60% less energy than

an ANSI/ASHRAE/IESNA Standard 90.1-2004,

Energy Standard for Buildings Except Low-Rise

Residential Buildings base case.

2 2 H i g h Performing Buildings Winter 2008Left Depiction of Pearl River Tower

Skidmore, Owings & Merrill LLP B u i l d i n g A t a G l a n c e

Building Name Pearl River Tower Location guangzhou, China Size 2.3 million ft² Started 2006 Completed estimated 2009 Use office Building Cost Estimated $12 million more than a building designed to meet the minimum requirements of Standard 90.1 Distinctions Designed to be the most energy-efficient super-tall tower in the world

B u i l d i n g T e a m

Owner CNTC Guangdong Tobacco Company Architect Skidmore, Owings & Merrill LLP (SOM) SOM Project Team MEP roger Frechette, P.E., project engineer, SOM’s director of sustainable engineering Architecture russell Gilchrist, project architect, SOM’s director of technical architecture Structural William Baker, P.E., FASCE, Skidmore, Owings & Merrill LLP SOM’s structural engineering partner Management tom Kerwin, FAIA, SOM’s Pearl River Tower is designed to be the most energy-efficient super-tall tower managing partner in the world. Wind Engineering Consultant Rowan Williams Davies & Irwin Inc. (RWDI) RWDI Project Team The Pearl River Tower, which will building code, which in the last few Ray Sinclair, Ph.D; Duncan Phillips, be the corporate headquarters for the years has become, in some cases, Ph.D.; Glenn Schuyler, Ph.D. CNTC Guangdong Tobacco Company, more stringent than Standard 90.1. Other Key Players was first designed as a carbon-neutral It still is expected to be the most Guangzhou Design Institute tower. But permitting (a lack of energy-efficient super-tall tower in the net-metering laws for commercial world, according to project engineer buildings) and cost issues whittled Roger Frechette, director of sustain- the efficiency predictions to a not- able engineering at Skidmore, Owings unimpressive 58% less than Chinese & Merrill LLP (SOM).

Winter 2008 H i g h Performing Buildings 2 3 All of this, Frechette said, can be carbon-neutral tower building?” said Building-Integrated done cost effectively. The project, as Frechette. “Even though the current Power Generation currently designed, costs $12 mil- design is not carbon neutral, we’ve set Wind power — integrated into the lion more than a building designed a very high bar and we’re doing some- design of the building — is one of to meet the minimum requirements thing that hasn’t been done before. the tower’s distinct features. The of Standard 90.1 — all of which can We hope that we, and others, can building has four large openings in be recovered in about five years learn something from this process and the envelope, two on each of the two due to reduced energy costs and the maybe someone can beat that mark.” mechanical floors, which house four increased retail and office space that The bar is high, and many of the small wind turbines. smaller HVAC equipment freed up. building features are creating a stir Guangzhou’s typical wind speed “We wanted to know: how far can even now, two years before the tower is usually a fairly mild 9 mph at that we go? Is it really possible to create a is scheduled to begin operations. elevation, but the air is literally pulled

C ooling from a B o v e , A ir from Below

Of all the elements in the Pearl River Tower’s A ventilation system is still necessary energy-efficient design, the radiant cooling to bring in air for breathing; the system system is the biggest energy saver. In this designed will deliver necessary ventilation system, water flows through ceiling panels underneath floors that are already raised to and provides cooling from there. provide room for cable. In this design, swirled Frechette says that the team looked to diffusers bring a supply of fresh outside-only Germany for this technology — it is rarely used air into the space and help to mix the air. in North America and is unusual in China. This “once through” approach to ventilation Another record-breaker, the system will be the improves the health of the building by reduc- largest radiant cooling system in the world. ing the risk of occupant exposure to airborne Because cooling is delivered by water viruses and odors. instead of air (and no heating is necessary “We have a building that takes outside air, Skidmore, Owings & Merrill LLP in the tropical climate), the system does not filters it, puts it into the building and then need to move air to cool the building. This vents it from the building,” said Frechette. Radiant cooling panels in the ceiling provide saves the energy needed to run that equip- “Conventional buildings use recirculation to cooling; ventilation air is delivered from ment and the money to buy and maintain it. cool or heat air because the air has already below the floor.

been cooled, and it saves energy. We aren’t using air for cooling, so the small quantity of air we bring in from the outside, for breathing, is not that expensive or difficult to cool.” Because there is no need for large volumes of air and minimal fans, the shafts that run vertically through the building are smaller, saving space that can be used for office and/or retail space. These systems also are quieter than the conventional design. A typical office floor in a United States building would be designed to have noise levels around 30 to 40 NC (noise criteria scale) — it’s difficult to get levels lower than that due to VAV boxes, fan Skidmore, Owings & Merrill LLP coil units and mechanical room fan and/or Air space between the two layers of the façade traps heat, which is vented out of each compressor noise. Modeling shows that Pearl floor before it can radiate into the space. River Tower occupants will enjoy spaces that are a quiet 25 NC.

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The Pearl River Tower’s wind design is based relationship, Frechette said. Air is pulled on a small turbine (almost 10 ft or 3 m in diam- through the building, accelerating the speed eter) by English manufacturer Quiet Revolution. of the wind by more than two times — and Each of the design’s four turbines has a rated increasing its power potential by a factor performance of 10,000 kWh per year. of eight. SOM pulled in the largest wind engineer- For this site, models showed that average ing and consultancy in the world to help wind speeds of 9 mph (4 m/s) will speed up them with testing and modeling for the wind to as fast as 18 mph (8 m/s) when they are design — Canadian firm Rowan Williams sucked through the building openings. Davies & Irwin Inc. (RWDI). “In essence, one wind turbine located in RWDI’s models helped to size and place the one of the openings could theoretically pro- turbines and provided suggestions to SOM duce the energy of eight turbines somewhere O wings & M errill LL P S kidmore, for selecting turbines —considering maintain- else,” said Frechette. “So, this building has Pearl River Tower design ability issues, noise, and vibration issues. power comparable to 32 turbines.” was based on a turbine One of RWDI’s tasks was to model wind The turbines are estimated to provide 1% of by Quiet Revolution. potential. Power potential for wind is a cubed the building’s energy needs.

through the holes in the envelope by (about 2% of the building’s needs). and finally to the building’s wall the negative pressure on the leeward The wind and photovoltaic systems receptacles. Energy is lost along south side, accelerating winds to not only reduce the amount of elec- every step of the way, making that speeds of about 18 mph. tricity needed from the power grid to energy pathway about 30% efficient. Modeling and wind tunnel test- operate the building, but also create Generating electricity at the site ing show this design has a power a more efficient system altogether. where it will be used reduces the potential capacity of nearly 15 times SOM’s initial design also included losses that come from handling more than a typical stand-alone wind the capability of producing power and distributing it. According to generator — in this case about 1% of on-site using microturbine technol- Frechette, the Pearl River Tower the tower’s power needs. ogy. Conventionally, power generation systems, with heat recovery, would The design was based on using four starts at the power plant, sends elec- be able to use about 80% of the small wind turbines manufactured tricity along lines to a transformer, energy that is produced, much more by Quiet Revolution, which have a efficient than “importing” electricity capacity of 10,000 kWh per year. from the utility. SOM also is taking advantage of the tropical sun, using two kinds of solar Multipurpose Double electric panels on the east and west Wall Façade façades. At the crown of the tower, With 71 floors of glass exposed to the design calls for photovoltaic (PV) tropical sun, one key element to technology integrated into more than reducing cooling load and the energy 16,000 ft2 (1500 m2) of the façade associated with it is the façade itself. glass itself. Another 16,000 ft2 (1500 SOM and their Canadian subcon- m2) of PV will be mounted onto the tractor Rowan Williams Davies & fixed solar shading feature on the Skidmore, Owings & Merrill LLP Irwin Inc. (RWDI) used modeling west façade. and wind tunnel testing to find the Four openings in the façade house the In all, the tower’s PV technology wind turbines and reduce pressure on the façade that would fit the structure will have a 300,000 kWh capacity tower structure. and design intent.

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D51476asjl_707170a.indd 1 6/20/07 5:24:41 AM L e s s o n s L e a r n e d

With more likely still to come, Frechette and Sinclair already have a list of lessons learned. Early Involvement First, said Frechette, to create a truly high performance building it is critical to assemble all of the primary stake- holders of the project at the very beginning of the design process to obtain full buy-in before proceeding. He lists the stakeholders as the design team, consultants, contractors, city officials, local utilities, as well as the owner. As an example, one major stumbling block during the design process was the fact that the local electric utility would not allow, or did not have the policies in place, to allow the owners to sell power to the grid (net metering). This problem was not discovered until well into the design process and was one of the major factors in not meeting the carbon neutral goal. Design Team Balance another lesson is the importance of the makeup of the design team. The proper balance of individuals is important to achieve what Frechette calls “pragmatic innovation.” “We have all seen intriguing design con- cepts that are never seen through to fruition due to the impracticality of the detail,” he said. “For innovation to be fully realized on a major project, the design team must be made up of individuals who can dream of what might be possible, working in concert with individuals who are grounded with years of practical no-nonsense experience. This pairing of personalities leads to fully attain- able, realizable innovations.” Double Façade sinclair points out that

the double façade design is not for every O wings & M errillLL P S kidmore, building. The systems require a significant At the crown, PV technology is integrated into the façade glass. amount of engineering and particular conditions — they are not an automatic silver bullet for high performance buildings, though the Pearl River Tower design is a good application of the technology. CFD Modeling He also emphasizes that Most buildings have a single vented out of the building, before it high performance can sometimes mean exterior façade, but the Pearl can radiate into the space, by fans “highly complicated”: “As buildings become River design has an insulated drawing air from a slot at the bottom more sustainable and use less energy to move more air, the air tends to migrate in exterior layer (two pieces of glass of the glass on each floor. natural ways with less velocity,” he said. sealed together) and an inside The air is drawn into the mechani- “That means flows are weak and will slosh layer — with air space sandwiched cal room where it can be released around. Higher levels of CFD modeling are in between the two layers. When from the building if it’s hot air, or required. We found that was an important consideration.” heat from the sun warms the air in used to draw humidity out of the the space between the layers, it is space with a heat exchanger. In

2 8 H i g h Performing Buildings Winter 2008 essence, it’s a solar-powered with the local Guangzhou Design dehumidification system.RWDI ’s Institute to take the lead on the Wind and photovoltaic systems reduce modeling helped optimize the airflow assembly of training manuals, and the amount of electricy needed from needed to size the dehumidification the owner plans to hire an experi- the power grid to operate the building. system and airflow, and found that enced firm to operate the building. an estimated few hours of running But, according to Frechette, the the system after a shut down will unique systems being implemented remove moisture from the space and actually should decrease the amount prevent condensation on the radiant of operation and maintenance effort ceiling panels. required, compared to a convention- Automated shading devices, ally designed building. For example, integrated into the façade on the the radiant ceiling systems, serving north and south exposures, will be the office floors, eliminate the need integrated in the active double-wall for VAV boxes and fan coil units, enclosure. These devices will be minimizing maintenance and opera- operated by a daylight-responsive tions tasks such as changing filters, control tied into an energy manage- cleaning coils, repairing damper ment system and will optimize the actuators, and responding to com- amount of daylight and heat being plaints about fan and air noise — not delivered to the space. to mention the frequent requirement RWDI project manager Ray of balancing and rebalancing air sys- Sinclair, Ph.D., helped model the tems as tenants move in and out of flow of air from the façade through the building. the building. With automatic shad- ing and the façade’s airflow design, Looking to the Future modeling shows that the inside of Though the project has been a chal- the façade will never get hotter than lenge, Frechette said he has found about 80°F, and that glare will not it to be exciting and very reward- impair the comfort of the occupants. ing. He hopes that the technologies “We modeled all of the factors that included in the tower design will affect heat transfer and heat moving become more mainstream, and that through the cavities,” said Sinclair. the project will encourage other kidmore, O wings & M errill LL P S kidmore, “Then, we optimized the amount of designers to consider high perfor- air moving through the cavity, and mance technologies. we showed that you could achieve “We’re in the middle of an environ- comfort at the perimeter of the space mental crisis that largely has to do

even in worst-case solar times of the with carbon emissions,” Frechette Skidmore, Owings & Merrill LLP day — while still maintaining views said. “Even architects and engineers and daylight.” need to be reminded that buildings produce more emissions than indus- a B o u t t h e A u t h o r Operations and Maintenance: try or transportation. We need to Is It Easy to Work? challenge ourselves to take this on, Kyra Epstein is a technical writer who A high performance building requires and we hope this project is a baby has worked with the National Renewable Energy Laboratory (NREL), Architectural attention even after the design is step in the right direction.” Energy Corporation, and LOHAS implemented and the building is Or maybe a giant, 71-story leap in (Lifestyles of Health and Sustainability). operational. The SOM team partnered a single bound. •

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