Joshua Tree National Park's Commitment to Solar Still Going Strong

April 1, 2002

Joshua Tree National Park's 7.2 kilowatt PV system serves the Cottonwood area Timothy Kehrli
Joshua Tree National Park's 7.2 kilowatt PV system serves the Cottonwood area.

President Franklin D. Roosevelt established the Joshua Tree National Park in 1936 to protect significant examples of the Mojave and Colorado Desert ecosystems. Until 1998, diesel-powered generators were the primary source of power to sustain operations at the remote Cottonwood visitor use area and employee housing facility located in the southeast portion of the Park. In 1998, the Park replaced two 32-kilowatt diesel generators with a 21-kilowatt photovoltaic (PV) power array system and a 30-kilowatt propane backup generator that now totally support the electrical power needs of the Cottonwood area. Since this first PV installation was complete, more systems have been added to the Park, and an end to continuing installations does not appear in sight.

The most recently-completed PV system is a grid-tied system at the North Entrance station. It consists of a 2.4-kilowatt PV system and a 2.5-kilowatt Xantrex/Trace Sun Tie inverter. This system will offset most of the energy use of the entrance station.

Another recently-installed system is the PV hybrid power system for the well that serves the Cottonwood area. It consists of approximately 7.2 kilowatts of PV capacity, an AeroVironment Universal Solar Pump Controller, and a back-up, propane-fired electric generator. This system provides most of the power for the well pump.

A 30-to-60 kilowatt grid-tied system for the Oasis Visitors Center is now in the conceptual design stage. The system will consist of Building Integrated PV (BIPV) with a grid-tied inverter. The BIPV will be installed on the existing artifacts storage and GIS buildings, reducing their cooling load. A large waterproof PV roof structure will be built over the maintenance yard to allow for storage of equipment and supplies and provide a gathering area for Joshua Tree personnel. The anticipated completion date for this project is late-summer 2002.

Despite a theft last summer at the Park's Indian Cove Amphitheater that cost the Department of the Interior $6,000 in PV panels, Joshua Tree National Park continues to be a national model for its use of off-grid solar powered PV systems. All new PV systems at Joshua Tree are now welded or riveted on to make them theft-resistant, allowing concentration to shift from theft worries back to adding more solar.

Joshua Tree National Park has been a recipient of a Federal Energy and Water Management Award, as well as a Federal Energy Saver Showcase Award for its dedication to PV installation.

For more information, please contact Otto VanGeet of the National Renewable Energy Laboratory at 303-384-7369 or