The Benton County Government Center is saving $22,500 a year, thanks to a news DDC system and more efficient lighting.
FOLEY—In just one year the Benton County Government Center was able to dramatically reduce its energy use, thanks to new fluorescent lamps and a new control system and variable frequency drives for its air handling system. The 40,000 square-foot facility cut its electrical use by 32 percent and natural gas use by 33 percent from its pre-project consumption. Actual savings: $22,500 per year.
Jim Whitcomb, Benton County property management director, knew the building’s heating, ventilation, and air conditioning (HVAC) system was greatly in need of improved energy control. His view was reinforced when the building’s Minnesota B3 energy benchmarking rating showed its energy use at more than twice what a new building of the same size and function would use.
In 2010, when energy funding became available from the Energy Efficiency and Conservation Block Grant (EECBG) program, Whitcomb jumped at the opportunity. He applied for and received the grant from the Minnesota Department of Commerce. The EECBG funding was provided by the American Recovery and Reinvestment Act of 2009, stimulus funding designed to save energy and create jobs.
New controls allow night, weekend setbacks. Typical for buildings constructed in 1973, the building’s 10 air handling units were regulated by a simple pneumatic control system. Unfortunately this system did not have the capacity for night and weekend temperature setbacks or to vary the airflow to meet changing needs within the building. The pneumatic controls were replaced with a direct digital control (DDC) system. Additionally, variable frequency drives were added to the fan motors of each air handling unit. The DDC system easily enabled night and weekend temperature setbacks, so heating and cooling loads could be reduced when the building was not in use.
The system, in combination with the variable frequency drives, allows fan motor speed to be adjusted to deliver only as much air as is needed to condition and ventilate. It also enables optimizing discharge temperatures seasonally for each of the air handlers based on the individual needs in each building zone. A concern to consider when converting a pneumatic control system to DDC is training operators. However, this was not an issue for Benton County because several of their buildings have had DDC systems for many years.
Of the new HVAC system, Whitcomb says, “We hear fewer complaints, there is less fluctuation in our temperatures during business hours, and it is great to have night and weekend setbacks optimized for savings.”
The energy savings have been extraordinary. In just one year, rather than using twice the energy of what a new building of the same size and function would use, it uses only three-fourths as much. Figure 1 below, from the B3 database, shows the dramatic savings in gas. B3 Benchmarking (see story below) helped demonstrate the need for and benefits of the new energy upgrades. Another convenient energy tracking tool used by many facility managers to compare the performance of their buildings to others throughout the nation is the ENERGY STAR Portfolio Manager.
Figure 1. The Minnesota B3 Benchmarking graph shows the weather-normalized projected natural gas use with a dashed line and the actual use with the red bars. The difference between the projected and actual gas use demonstrates a decrease of 33 percent from 2009 to 2012. Weather-normalized values provide the most accurate measure of the energy project and compare building performance from year to year independent of weather variations.
Simple lighting change provides big savings. The EECBG-funded project included changing out more than 4,000 32-watt fluorescent tubes with 25-watt tubes in the Government Center and three other county buildings. Just by changing the bulbs saves 21 percent of the lighting energy for each fixture. For this reason Minnesota electric utilities often provide rebates for even this simple change. “We have received no complaints,” said Whitcomb of the lighting change. “That is a good indication that people are happy with the lighting.”
The combination of DDC system and fluorescent tube change outs contributed to electrical savings for the Government Center of 24 percent in 2011 and 32 percent in 2012 compared to the 2010 baseline.
Resources for public building projects. Counties, cities and other public entities seeking energy improvements are encouraged to consult with their local electric or gas utility. Utilities can help with building assessments and may provide rebates for energy efficiency improvements. The Minnesota Department of Commerce, Division of Energy Resources (DER) provides support to local government units, state agencies, school districts, and institutions of higher learning that are seeking energy efficiency and renewable energy measures. Contact DER at firstname.lastname@example.org to discuss which of its energy efficiency programs can be of help.
The U.S. Department of Energy’s Building Technologies Office also provides helpful resources for building retrofits, including “The Advanced Energy Retrofit Guide for Office Buildings.” For more on energy efficiency, contact the DER Information Center at email@example.com or 800-657-3710.
Minnesota B3 Benchmarking is an energy tracking system for public buildings in Minnesota, including state, local government, and public school buildings. It provides the tools to manage your buildings, improve your building portfolio efficiently, and monitor the improvements.
Benchmarking simply means that the energy consumption for a particular building is compared to the energy it should be using. Identifying those buildings that are using more energy than they should is extremely important because high-energy-using buildings are most likely to have the greatest cost-effective savings potential. The B3 tool is provided by the Minnesota Department of Administration and the Minnesota Department of Commerce, with funding from all utilities in the state supporting the effort.
To add your building to the database, go to http://www.mnbenchmarking.com and click on “Contact Us.” For information on how to view your building’s energy data, contact the Minnesota Department of Commerce, Division of Energy Resources at firstname.lastname@example.org.