US Army: Fort Huachuca, AZ


Federal government mandates require the nation’s military facilities to reduce the amount of their energy consumption by 30% by 2015; new or refurbished buildings must reduce fossil fuel use by 55% (from 2003 levels) by 2010, and 80% by 2020. 

The U.S. Army Corps of Engineers contracted Nextek Power Systems to install a Direct Coupling® DC Microgrid in the water chemistry lab of the south chiller plant at Fort Huachuca, AZ, in a demonstration project designed to illustrate progress towards the above goals, as well as to evaluate the potential for larger installations in the future.

Ft. Huachuca is located 50 miles southeast of Tucson, and receives, on average, 6.0 to 7.0 kWh/m2/day via solar energy throughout the year, placing it at the upper end of the solar energy reception spectrum in the United States. It is  in a region of high potential for the development of solar energy. 

In typical microgrid installations, DC power generated from renewable sources is inverted to AC current to access the grid, then rectified back to DC for use in the load. Each conversion incurs energy losses ranging from 3% to 30%.


Direct Coupling® technology utilizes DC-compatible equipment that eliminates the need for multiple energy conversions. By regulating the solar array and the power to the load, power loss in the system is reduced, which translates to energy cost savings.

Existing photovoltaic panels were also employed. The solar array produced between 60 – 120 VDC through a Maximum Power Point Tracking Controller to a constant output voltage for distribution through a Power Server Module. The input of the PSM combines DC from the photovoltaic system with the bidirectional functionality of a battery backup/storage unit and AC from the grid.


The DC photovoltaic system successfully powered the facility, completely eliminating the use of grid-supplied AC power since its installation, and showed significant energy cost savings if installed base-wide.

  • No AC grid power has been consumed since the installation of this project, in July 2011
  • ROI break even point: 3.13 years
  • Energy and efficiency savings: $3,000/year (25,000 sf)
  • Reconfiguration Savings: $1.7 million (25,000 sf)
  • DC Microgrid system efficiency: 97% for DC input
  • Reduced risk of electrical shock by replacing 110 VAC lighting system with safer, low voltage 24 VDC system.

Download the US Army Facility Case Study PDF