Bank of America Tower
Height — 303.89 m, 76 floors, area — 457,220 sq. m. Towers over Seattle, remaining perhaps the tallest building on the Pacific Northwest coast of the United States.
This skyscraper is the tallest building on the Northwest coast of the United States, offering views of the Space Needle, Puget Sound, Mount Rainier and Northern Cascades.
But in addition, a project was carried out to install one of the largest direct digital control (DDC) systems for automation of a commercial office building in America.
Project Scope
— 4 workstations for operators of the BACtalk automation system from Alerton;
— 4 laptops for workstations;
— 41 BTI building automation controllers;
— 650 Alerton VAV controllers/»field» controllers;
— Over 12,000 control points;
— 2,200 heat pumps;
— 166 supply ventilation systems;
— 200 various exhaust fans;
— 15 boilers;
— 15 heat exchangers;
— 6 cooling towers with 6 sections each;
— 25 circulation pumps.
The Bank of America Tower took three years and cost $200 million to build.
When it came time to select an HVAC system, the building owner had strict requirements — an open automation protocol was required that would support and control such a large facility, and that could be installed in the building they occupied without displacing the occupants.
ATS Automation (ATS) was selected as the integrator to install the Alerton automation system, which is based on the BACnet protocol.
The size of the tower wasn't the only issue ATS faced.
The tower is the largest commercial consumer of electricity, not only because of its office and retail space, restaurants, convenience stores, art gallery and observation deck, but also because of its illuminated walking paths, open 24 hours a day, 7 days a week.
Seattle City Light, the municipal power company, predicted an astronomical peak in electricity consumption equal to the capacity of the proposed hydroelectric dam.
The Tower Automation System (BAS) should have been at the forefront of monitoring and control at any point where energy efficiency reporting was provided.
The tower's enormous height resulted in a significant increase in natural draft pressure in cold weather, which was distributed differentially throughout the entire height of the building.
An air pressure differential occurs when indoor air exits at the top of a building and mixes with outside air entering through an open inlet. The problem was that the exhaust air on the upper floors needed to be cooled while the supply air on the lower floors needed to be heated.
ATS installed Alerton BACnet control systems that integrated all of the tower's systems, including instrumentation control for monitoring and controlling energy use.
The Bank of America Tower project included automation of the heat pumps, air handling units, boilers, heat exchangers that cool the tower, and circulators.
ATS also integrated life safety and fire protection systems. Operator workstations, running on the tower's Ethernet local area network, control all building functions via Alerton's BACtalk® BACnet interface.
In light refraction alone, the Bank of America Tower absorbs more energy than a building two-thirds the size of the tower.
All workstations in the automation system use software that controls the operation of BACnet equipment. Equipment control operators can connect to the internal network to monitor and control the entire system at any point.
Each computer displays a graphical package that includes floor plans and system diagrams.
BACtalk tracks energy consumption (kilowatts per hour).
This allows the tower manager to manage the distribution of energy throughout the building using a single energy consumption meter. The manager can monitor energy consumption by automatically limiting its consumption.
BACtalk also maintains a special log (log5 file) of the building tenants' activity, where any «extra-plan» activity of each tenant is recorded.
The tower equipment manager can view and modify the log5 file before issuing an invoice to the tenant.
Alerton's Bank of America Tower Control Modification project utilized wireless technology throughout its implementation and commissioning.
The open BACnet protocol allowed technicians with laptops to access the automation and control system from anywhere in the tower using equipment that utilized wireless communication standards.
Workstations, also running on the BACnet protocol, can communicate with the building management via the installed local network from any point to perform supervision and control functions. They can evaluate and, taking into account current needs, change the settings.
All this is done from the central control room. ATS was able to solve most of the «stack effect» problems in terms of heating demand by programming the «heat distribution» cycle in the tower heat pump system.
The hydronic system serves 2,200 heat pumps, implementing four closed cycles and one open cycle of the cooling tower.
The total capacity of all five cycles exceeds 367,264.84 liters.
Plastic heat exchangers link the cycles into a single unit, and heat pumps deliver a water flow into the building's cooling cycle.
To overcome the «stack effect,» ATS used heat pumps with the cooling tower valves in the closed position so that the system could re-accept heat energy on the upper floors and significantly reduce the heating requirements of the boilers.
Moreover, pressure monitoring is carried out on each floor.
In the case of the «stack effect», the exhaust air can be removed using mechanical exhaust ventilation.
By measuring the pressure on each floor (in the rest of the building), the system reduces the amount of energy consumed by mechanical exhaust.
This system provides mechanical air supply and exhaust and guarantees a comfortable air supply to the building's tenants.
Along with centralized control of energy monitoring in the Bank of America tower, the equipment manager easily and accurately tracks the path of the energy used and the state of the account for its consumption both as a whole building and for individual tenants.
Today, it consumes about 31,000 megawatt-hours of energy annually, still remaining at the peak of the city's energy consumption.
But thanks to the effective control system, the tower consumes about 3,500 megawatt-hours more energy than another building that is considered the main consumer of electricity in Seattle, but is only 2/3 the size area of the tower.
Information provided by Alerton