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State Capitol Building Retrofitted With Geothermal Heat-Pump System

March 31, 2015
The state aimed to increase the energy efficiency of the complex’s buildings while incorporating renewable-energy solutions.

In 2003, the Colorado Capitol Complex in Denver was slated for a major renovation and restoration by the Colorado Department of Personnel & Administration (DPA).

The Colorado State Capitol building.

“Some of the HVAC infrastructure in the complex was more than 80 years old, and the system at large was generally overdue for an upgrade,” Lance Shepherd, manager of design and construction programs for the DPA’s Office of the State Architect, said.

According to Shepherd, the state also aimed to increase the energy efficiency of the complex’s buildings while incorporating renewable-energy solutions.

“Under the Renewable Portfolio Standard, Colorado is requiring the use of 30 percent renewable-energy deployment by 2020,” Shepherd said. “The mechanical-system-upgrade portion of the building’s restoration needed to reflect this as well.”

The DPA worked with Chevron Energy Solutions (CES) to plan a series of upgrades and improvements totaling approximately $30 million applied across the Colorado Capitol Complex, including the governor’s residence, the Colorado Department of Revenue building, and the Colorado State Capitol building. In addition to the HVAC-system updates, the plan included energy-efficient lighting systems, energy-management systems, water-conservation measures, building-envelope retrofits, removal of outdated equipment, and asbestos abatement.

For the State Capitol building, the team designed a hybrid mechanical system. A more-than-200-ton geothermal heat-pump system was integrated with a 10-kW solar photovoltaic system, as well as new and existing ancillary HVAC equipment, such as boilers and air-handling units.

The HVAC-system design called for nine water-to-air and water-to-water heat-pump units from  ClimateMaster: four 1.5- to 5-ton horizontal and vertical Tranquility 16 Compact (TC) Series units, four 3- to 5-ton horizontal and vertical Tranquility 30 Two-Stage (TT) Series units, and one 3-ton Tranquility Modular Water to Water (TMW) Series unit, all with EarthPure HFC-410A refrigerant. The 23-ton heat-pump system provides heating and cooling throughout the building.

One of a system of nine water-to-water and water-to-air heat pumps from ClimateMaster that are part of the Colorado State Capitol's new and highly efficient heating and cooling system.

The network of heat pumps was integrated with an open-loop geothermal system utilizing the Arapahoe Aquifer, located approximately 900 ft below the State Capitol building.

The first phase of installation began in the fall of 2010, when 900-ft supply and return boreholes were drilled into the aquifer. Water (moving through stainless-steel piping set in the boreholes) is pumped between the building and the aquifer at up to about 350 gpm.

“The ground side of the geothermal system pumps water drawn from the underground aquifer, piping it up through a heat exchanger, and then returning it back to the aquifer,” Lou Grounds, sales engineer for Ace Mechanical Equipment, which supplied the heat-pump units, said. “This results in providing consistent indoor temperatures of 65 degrees through the HVAC system by either heating the source water—which is coming from the building—in the winter or cooling it in the summer.”

Once drilling was complete, CES oversaw installation of the high-efficiency heat pumps, which replaced split units and other outdated HVAC equipment, throughout the building. A new pumping system was installed in the building’s sub-basement to serve the heat pumps.

Grounds said installation went well.

“When you’re negotiating historic spaces, especially with newer equipment, it’s not always a guarantee that things will go smoothly,” Grounds said. “The ClimateMaster units were extremely easy to install and were tested and up and running very quickly.”

From submittal preparation, review, and approval through installation and startup, the project time line was approximately 12 months and continued even during the state’s legislative sessions. In addition to being one of only a few structures of its kind to incorporate geothermal heating and cooling, Colorado’s State Capitol building became the first facility to receive LEED for Existing Buildings (LEED-EB) certification from the U.S. Green Building Council and the first LEED-certified state capitol.

Total project costs totaled $6 million, $4.6 million of which came from a U.S. Department of Energy grant under the American Reinvestment and Recovery Act. The remaining $1.4 million came through state-funded certificates of participation and a lease-purchase agreement with CES.

Since coming online during the summer of 2013, the geothermal heat-pump system has generated substantial savings. During the first year of operation, $95,000 in utility-bill savings was achieved. Savings are estimated to increase by about 3 percent annually, reaching $165,000 by 2029. Payback on the geothermal system is estimated to be 10 years.

“By tapping into the steady temperatures below the earth’s surface, we were able to heat and cool the Capitol building with a reliable and clean source of renewable energy at a reduced cost to the people of Colorado,” former Colorado Gov. Bill Ritter, who currently is the director of the Center for the New Energy Economy at Colorado State University, said.

Jeff Holland, owner of Ace Mechanical Equipment, added, “This project is a terrific example of how ClimateMaster geothermal heat-pump equipment can help engineers and owners convert a historic, high-profile building with an old, antiquated HVAC system into a modern, high-efficiency, comfortably conditioned building while achieving LEED points in the process.”

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