Energy Efficient Demonstration Proves Powerful in Home Retrofits
NREL recommendations demonstrate substantial savings for the Navy.
When Navy officials handed NREL a tough assignment, two NREL building engineers headed to Guam—hot, humid, and beautiful, where homes are built to handle typhoons and potential cyclones.
Residential building engineers Lieko Earle and Bethany Sparn needed to identify the most cost-effective ways to retrofit homes in more energy efficient ways.
With aggressive goals to reduce facility energy use by 37.5% from 2003 to 2020 and ensure that 50% of Navy and Marine Corps installations are net-zero energy, the Department of Defense (DoD) wanted to quickly reduce electricity use in military housing.
Go Big or Go Home
"When offered the opportunity, Lieko and Bethany chose to 'go big or go home,' suggesting comprehensive retrofits rather than a more incremental approach," said Jeff Dominick, NREL principal investigator of the Navy project. "Lieko and Bethany wrote a compelling demonstration proposal and assembled a project team that included key Navy stakeholders at the regional and Naval Base Guam installation levels."
The duo had to move quickly to apply their residential buildings research experience. Their team had roughly a year to choose representative homes, install various technologies, gather data before and after the retrofits, and provide recommendations based on their results. The focus was to reduce loads related to water heating and whole-house cooling. In late 2012, the demonstration site selected was Naval Base Guam in Apra Harbor, which has 1,369 houses for its active-duty Navy and family members.
"Typically when we evaluate a home, we look at all the possible changes," said Earle. "With this retrofit, the process was simplified because we couldn't alter the concrete construction of the buildings, so the list of things we could consider was more limited."
Small-Scale Demonstration, Large Return
The team employed a building energy simulation tool developed at NREL, called Building Energy Optimization (BEopt) with EnergyPlus, to identify the most cost-effective packages to increase whole-house energy efficiency. Eight homes were selected to participate in the demonstration, and based on the analysis, the technologies installed included high-efficiency air conditioners and air handlers, internet-connected programmable thermostats, low-flow shower heads, and heat pump water heaters. A few homes also got in-line dehumidifiers.
"In all eight homes, electricity use was monitored at the end use before and after the retrofits to measure differences in daily energy consumption," said Sparn. "Results showed that these technologies have the potential to save the Navy millions."
Given Naval Base Guam's high electricity rates of $0.50 per kilowatt hour, the efficiency upgrades in the eight homes are projected to save $120,000 over the next 10 years, or $15,000 per home. With this net savings, the projected payback is less than 3 years. The biggest savings relate to the air conditioning units and replacing electric water heaters with heat pump water heaters.
"The Navy has adopted the higher efficiency water heating and space cooling technologies for its future procurements," said NREL Project Manager Gene Holland. "Since the Navy pays the residential electricity bills for its housing, this could save the Navy lots of money and improve its carbon footprint."
New air conditioning units are replaced in each house at Naval Base Guam every eight years. With 288 units replaced last year alone, this potentially equates to more than $4 million in savings over the next 10 years.
This NREL project is one of eight demonstrations supporting DoD in Hawaii and Guam that are focused in three categories: energy efficiency, renewable energy, and energy systems integration.
Benefits Beyond the Navy
Earle and Sparn's team success may offer benefits beyond the Navy. Heat pump water heaters have not yet been widely adopted on Guam, and NREL's Guam-based contractor team now has hands-on experience with the technology. In addition, both NREL and the Navy are members of the Government of Guam Energy Task Force. Results will be shared with other members of the task force, accelerating the adoption of these commercially available technologies.
To learn more about the demonstration projects, download the Naval Facilities Engineering Command Hawaii and Guam Energy Improvement Technology Demonstration Project reports at nrel.gov or visit NREL's Department of Defense Energy Programs.
—Written by Linh Truong