Sleeping Bear Dunes National Lakeshore, North Manitou Island
Department of the Interior
National Park Service
Empire, Michigan

North Manitou Island is a 15,000-acre wilderness area in Lake Michigan. In addition, the island is home to a separate, 52-acre, National Historic Landmark site. The Landmark contains several historic structures that serve as an administrative area.

Each year from May 15 to November 15, the island plays host to some 10,000 hikers, campers, birdwatchers, and other outdoor enthusiasts. Before installation of the photovoltaic (PV) hybrid system that now supplies the island's electricity, visitors and staff contended with noise and air pollution caused by three 30-kVA diesel generators. In addition to the air and noise pollution of the generators, the transport of fuel to the island by boat also posed the threat of an accidental spill. According to the maintenance foreman, Paul LaValley, even a small amount of fuel spilled in a lake or at an isolated location can necessitate a difficult and costly clean up. Diesel and propane used for cooking also had to be stored on the island, which created some safety concerns.

In collaboration with the U.S. Department of Energy and Sandia National Laboratories, the National Park Service invested $190,000 in the hybrid-PV system that now provides 85% of the island's energy needs. The system consists of a 10-kW PV array, installed in three subarrays; a 2400-Ah battery bank at 120 V (sufficient for five cloudy days); a 15-kW inverter to convert 12 V DC to 120 V or 240 V AC power; and controllers and switchgear needed to optimize the system's functioning and backup. Diesel generators are required occasionally, especially from Labor Day to November, and they continue to supply about 15% of the island's energy needs.

A hybrid system such as this, consisting of PV arrays, battery banks, and diesel generators, is especially useful in an area not served by the conventional electric-power grid. It provides power 24 hours per day, and reduces the noise and air pollution caused by the diesel generator system by 85%. The hybrid system will also save $2,500 per year in diesel fuel costs as well as the costs of transporting fuel to the island.

The NPS staff on North Manitou Island have been using the PV-hybrid system for three years. They believe it is a system that could and should be used throughout the Park Service as a way to conserve and protect the National Parks. The system also educates visitors and encourages them to be more environmentally conscious in their own homes.