The solar array at Natural Bridges has numerous solar modules, some over 20 years old. A solar module is a single framed panel with a power output of 50 to 300 watts, depending on the size and type.

Solar power was first installed at Natural Bridges National Monument (NBNM) in 1980 by a partnership of MIT, the U.S. Department of Energy, and the National Park Service. The photovoltaic system cost $15 million in 1980, today the system would cost approximately $1.5 million, a significant reduction over 20 year.

The system provided uninterrupted, clean electricity for NBNM for 10 years until the battery bank was retired. Unfamiliarity with renewable energy technology and funding limitations of replacing the battery bank resulted in the NPS shutting down the photovoltaic system. NBNM switched to diesel-fired generators to supply electricity to the visitor center, maintenance facilities and employee housing.

A partnership between the NPS, U.S. Department of Energy and the Utah Department of Natural Resources provided funding, solar engineering and technical expertise necessary to restore the photovoltaic system.

Project Description

New charge controller.

In 1993, the NBNM photovoltaic system was down-sized from 100 to 50 kilowatts (kW) with diesel generator backup.

The restoration project added 18 kW of new solar modules, replaced the battery bank with standard off-the-shelf batteries and upgraded wiring.

Identification and installation of energy conservation measures in NBNM facilities reduced the electricity load at NBNM to accommodate down-sizing to the 50 kW system.

An energy audit completed in 1996 identified additional cost-effective energy efficiency measures to reduce electricity, propane and water use. The measures include a lighting retrofit, energy efficient appliances, programmable thermostats, insulation of water heaters and low-flow shower heads. The estimated cost of installing all the recommended measures is $8,600.

The battery room contains batteries installed in 2003, replacing the 1992 batteries.	A new inverter was installed in 2003 as part of a system upgrade. It replaced the twenty-three year old inverter.

Results

Photovoltaic power system restored; currently provides 90 percent of electric power needs for NBNM visitor center, maintenance shop and employee housing.

Estimated savings of $34,000 per year in diesel fuel and maintenance costs associated with operation of diesel generators.

Environmental benefits include a significant reduction of air and noise pollution from the diesel generators. Emissions reductions are estimated to be 170 tons of CO², 2,100 lbs. of NOX, 400 lbs. of SOX and 250 lbs. of CO annually.