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State building shows North Dakota’s commitment to efficiency

Large windows on the north face of Century Center wed aesthetics and efficiency by bringing natural light into the office building. (Photo courtesy of Steve Silverman, Grand Forks, N.D.)

The mission of North Dakota’s energy efficiency and renewable energy programs is to promote energy conservation and efficiency, encourage renewable energy use and development, control operating costs and win awards.

The last two are results rather than goals that have come from energy efficient building projects like the Century Center building built by Workforce Safety & Insurance to house its main insurance operations and five other state agencies. “The anticipated cost of heating and cooling a much larger facility with natural gas definitely shaped our choice of technologies,” admitted Energy Program Manager Kim Christianson.

As for the awards, Christianson and WSI Facility Manager Curt Zimmerman recently submitted an application to designate the Century Center an Energy Star building. Although not directly related to the office building, the Energy Efficiency Forum’s 2002 Governor’s Leadership Award recognized the commitment that made the project possible.

Century Center biggest state building to use geothermal system
“The Commerce Department is a big supporter of geothermal technology, and this was a good opportunity to put it to work on a large-scale application,” said Zimmerman.

At almost 116,500 gross sq. ft., the Century Center building is the largest North Dakota office building to use a geothermal heating and cooling system. Other state buildings equipped with geothermal technology include the Missouri River Correctional Facility, the visitor center at Sakakawea State Park, a Job Service North Dakota service center in Bismarck and the State Historical Society at Pembina, N.D. The State Buildings Energy Conservation program awarded grants to many of those installations.

The Century Center project received $34,600 from the program to cover a portion of the incremental system costs and the cost of engineering fees related to the geothermal site testing. “We wanted to make sure the system was a good fit for the building,” Zimmerman said.

 

With 286 geothermal wells connected to 11 zone pumps, the Century Center building is the largest application of geothermal heating and cooling in a North Dakota public building. (Photo courtesy of Workforce Safety & Insurance)

The system consists of 216 heat pumps controlling the temperature throughout the building and providing snow melting capabilities for the north side sidewalk. There are 11 zone-circulating pumps that circulate water to 286 geothermal wells that are divided into 22 zones. The zone-circulating pumps are programmed to stagger on and off, one at a time, according to demand.

When the coolant in the heat pump loop dips below 45 degrees F, or rises above 75 degrees, one or more of the pumps kicks on. “By cycling on demand, the zone-circulating pumps are able to transfer heat from the geothermal zones and transfer it to the building heat pump loop,” said the facilities manager.

When the heat pump loop is between the temperature parameters, the zone pumps shut off and the temperature is maintained by transferring the heating/cooling loads within the building, so the building balances itself.

As a result, the heating and cooling systems experience no hard seasonal switchovers, Zimmerman added. He also cited low maintenance as another advantage of geothermal technology.

Heat recovery system improves heating, cooling loads
Century Center’s air handling system works with the geothermal system to make heating and cooling even more efficient.

Located in the fifth-floor penthouse, the unit continually draws outdoor air into the building during occupied hours, and switches the direction of the air flow every 90 seconds during operating hours. Fresh air passes over stationary aluminum plates and the heat is transferred by exhausting indoor air over the same plates every 90 seconds. In the winter, the plates warm the outdoor air, reducing the amount of energy needed to heat the fresh air. The system works in reverse during the summer when exhausted indoor air cools the fresh air that is being brought into the building. Zimmerman estimates that the system is 80 to 90 percent efficient, and with only one moving part, requires minimal upkeep.

Controlling the HVAC equipment is an Andover software-driven energy management system. In addition to controlling the temperature on a room by room basis, the system manages the geothermal well pumps and generates activity reports. “Monitoring a system really helps to control electricity consumption,” Zimmerman observed, noting that, “The system took some tweaking to get the maximum efficiency from it.”

Technology, nature team up for efficient lighting
Lighting, a big electricity consumer in any office building, is managed by a programmable lighting control system with low-voltage lighting switches and relay panels. The Century Center system flashes building lights at 6 p.m. to warn occupants and then shuts off the non-emergency lights five minutes later. “Employees can keep their lights on by flipping the switch off and on once,” said Zimmerman. “The warning repeats every two hours.”

Outdoor lighting is on the control system, too. At 10 p.m., lights in the outlying parking lot switch off automatically.

Using natural light not only reduces electricity costs, it improves employee morale and the look of the building. The architect joked that in the old building, many offices had posted “tornado shelter” signs outside the door. In Century Center, the north face includes a large glass curtain wall which houses breakrooms and employee work areas. A large glass atrium in the facility’s south side permits employees to access the third and fourth floors from the middle of the building.

Total construction cost for the Century Center building was just under $11 million. Energy saving features added approximately $100,000, most of which paid for drilling wells for the geothermal system, said Zimmerman.

He estimates that the payback on the features will be five to seven years “That estimate may not have included avoided maintenance costs,” he added. Not bad for a public building that will be saving workers compensation premium dollars for many years to come, and not surprising for a state that is planning for its energy future with programs today. As Zimmerman put it, “It takes long-term energy savings to manage long-term energy costs.”