Hybrid Solar Photovoltaic and Wind Energy System Team

Benton Lake National Wildlife Refuge, Fish and Wildlife Service, Montana

Point of Contact

Kathleen Burchett
(406) 727-7400


The 25.4 kW hybrid solar photovoltaic (PV) and wind energy system at Benton Lake National Wildlife Refuge (NWR), located on the western edge of the northern Great Plains in Montana, is the first of its kind in the Mountain-Prairie Region.  In November 2009, Fish and Wildlife Service (FWS) installed 15.4 kW of grid-tied pole-mounted single-axis adjustable solar PV panels and a 10 kW grid-tied horizontal axis Bergey wind turbine to reduce electric consumption at the already super-insulated, energy-efficient headquarters building.  The impact on energy consumption was remarkable.  In FY 2010, these integrated renewable energy systems accomplished a 93 percent decrease in purchased electricity consumption for the headquarters building and a 33 percent reduction in energy intensity from the field station's FY 2003 baseline, with a cost savings of approximately $4,000 per year, an energy savings of 121 million BTUs, and 25 MT of greenhouse gases avoided in CO2e.


Established by Executive Order in 1929 as a refuge and breeding ground for birds and covering 12,383 acres (19 square miles), Benton Lake NWR is located on the western edge of the northern Great Plains, near Great Falls, Montana. The gently rolling terrain of the Refuge is dominated by native shortgrass prairie and surrounded on three sides by mountain ranges. The main marsh on the Refuge has been subdivided into eight impoundments by a series of dikes and water control structures, which enables water management and provides a diversity of habitat types. Approximately 240 species of birds have been recorded on the Refuge and 90 are known to nest on the Refuge. Other wildlife includes 28 different species of mammals and several species of reptiles and amphibians. Despite its name, Benton Lake is actually a 5,000 acre shallow wetland created by the last continental glacier thousands of years ago.

Benton Lake National Wildlife Refuge Wind Turbine and Solar PanelsThe remarkable 25.4 kW hybrid solar photovoltaic (PV) and wind energy system (pictured right) at Benton Lake NWR is the first one of its kind in the Mountain-Prairie Region. The Service took a sustainable, whole-building approach to reduce the carbon footprint in the 4,220 square-foot headquarters and office building. The building is less than 10 years old, is super insulated, completely weatherized, and has operable low-e windows. Passive solar energy strategies were incorporated into the building design. The building is conditioned by high efficiency natural gas-fired forced air furnaces with ENERGY STAR condensing units. In FY 2010, the Refuge completed a lighting retrofit to replace T-12 fluorescent lights and magnetic ballasts with T-8 fluorescent lights and electronic ballasts, occupancy sensors, and LED exit lights. An energy audit completed in 2009 by Northwestern Energy, identified energy conservation measures and evaluated renewable energy opportunities. In addition, the audit identified this location as a good wind and solar site, using data from the National Renewable Energy Laboratory.

The short winter days are typically windier than the long days of summer. It was determined that a meteorological tower to gather preliminary wind data was unnecessary. Based on the audit findings, the Refuge implemented a hybrid solar PV electric and wind turbine system in November 2009, at a cost of $218,600, funded by the American Recovery and Reinvestment Act of 2009 (ARRA). In all, 15,400 Watts of grid-tied pole-mounted single-axis adjustable solar PV panels and a 10 kW grid-tied horizontal axis Bergey wind turbine were installed to reduce purchased electric consumption at the Refuge headquarters. Electricity is used for lighting, air conditioning, and the plug load -- outlets, computers, printers, etc. Natural gas is used for building heating and hot water. In 2009, building electricity consumption was 41% of the total energy consumed, and natural gas was 59% of the total energy consumed.

Results and Achievements

The impact on energy consumption of the hybrid solar PV-wind energy system is quite remarkable. In FY 2010, a 93% decrease in purchased electricity consumption for the Headquarters Building and a 21% reduction in energy intensity (BTU per gross square feet) from FY 2009 for the entire Benton Lake field station were accomplished. Further, energy intensity decreased by 33% from the field stations FY 2003 baseline. This amounted to an energy savings during FY 2010 of 35,423 kWh (35.4 MWH), or 121 MMBTUs. Assuming a 20-year life, the estimated lifecycle energy savings is 2,420 MMBTUs, and the estimated lifecycle renewable energy production would be 708 MWH.

The 93% decrease in electricity consumption resulted in a savings of $3,894 per year in electrical costs in 2010 from the previous year, from not quite a full year of operation. The estimated differential payback for the project is 55 years. However, the Service anticipates that the payback period will be much less than originally calculated with a full year of operation and the increasing costs of fossil fuels. We anticipate additional savings, noting the wind turbine was not on line for a month during this period. Using the energy savings of 35,423 kWh in 2010, and a unit cost of $0.15 per kWh, the total estimated total energy cost saved in 2010 for a full year of operation would be $5,313.

The 35.4 MWH of renewable electricity generated by the hybrid system would result in a reduction of approximately 25 metric tons of greenhouse gases emissions yearly. Concerns about the wind turbines affects on local bird and bat populations were diminished by positive results from a 3-year study of a small horizontal axis wind turbine at Eastern Neck NWR, Maryland. Although the local utility, Northwestern Energy, does not provide rebates, they 1) signed an interconnection agreement with the Refuge, and 2) installed a digital electric meter that will run backwards if the system produces more power than the facility consumes. As both renewable energy systems are grid-tied, there is no need to install a battery system, and the grid essentially is used as the battery. This strategy has the additional benefit of reduced use of natural resources. New design-build procedures (FAR 36.3) using a Multiple-Award-Task-Order-Construction (MATOC) contract were used for the process. As such, the prime contractor was MCS Environmental, Inc., of Missoula, Montana, and the sub-contractor was Alternative Energy Systems, LLC, of Great Falls, Montana. Since the system went online, occupant comfort in the building has increased without sacrificing electrical availability.


This project serves as a model illustrating the feasibility of renewable hybrid solar PV and wind energy systems. It represents a new approach to Service renewable energy design and construction, embracing renewable energy and paving the way for installation of similar systems. The project team proved that an integrated hybrid renewable energy system could work efficiently and effectively to reduce the carbon footprint at a field station. The team did not take the easy path of inaction and the same old-school standard practices. They demonstrated energy and environmental leadership.

Based on the sterling example of this successful renewable energy project, other NWRs have expressed interest in installing their own hybrid renewable energy systems as an alternative to fossil fuels. Several local business establishments and the Cascade County Road Department have inquired about the installation and the potential use of this type of system at their locations. In addition, the new system has been an excellent public relations tool for the Refuge since its installation. The Refuge has developed a small display in the headquarters building praising the benefits of renewable energy and the outstanding results achieved. This project received an Energy and Water Management Award from the Federal Energy Management Program. It was publicized with press releases, a local media campaign, and on various websites that are read by all Service employees, Friends groups, and outside stakeholders.

Benton Lake National Wildlife Refuge Electrical Panel - The large box on the right is the inverter for the wind turbine and the smaller boxes on the left are inverters for the solar panels.
Benton Lake National Wildlife Refuge Electrical Panel - The large box
on the right is the inverter for the wind turbine and the smaller
boxes on the left are inverters for the solar panels.