Although the electrical loads at each hut are pretty minimal, a few are critical either for safety or for guest comfort: a fire alarm system; water pumps; and a radio system for communication with AMC headquarters, Forest Service personnel, and emergency response units. Other loads include refrigerators, compact fluorescent lights, and small fans to ventilate the composting toilets.
The AMC’s first step into renewable energy came in the early 1980s, when staff members rigged a microhydro setup at Zealand Falls. This makeshift system ran for several years before falling out of use. Staff later swapped out the system’s original 120-volt AC alternator for a 12-volt DC one for battery charging. The microhydro system now puts out a steady 300 W, or 7.2 KWH per day, from May through October.
In the late 1980s, the AMC made the leap to solar electricity, hooking up small PV modules directly to chargers for batteries used by the radios. Small-scale success led to the installation of larger systems at the Mizpah Spring and Madison Spring huts in 1988 and 1989, respectively. Today, all eight huts have PV systems, ranging in size from 340 watts to 900 watts.
Six of the huts supplement their solar electricity with energy from small roof-mounted wind turbines (Southwest Windpower’s Air 303s or the newer AirXs). Roof mounting a turbine is rarely recommended because of noise, vibration, and turbulence issues, and very importantly, the turbine will rarely be high enough above surrounding objects to produce meaningful energy. But for the huts’ extremely windy wilderness settings and the lack of staff with tall-tower and turbine maintenance experience, roof mounts made sense.
All of the huts get significant winds, but none as extreme as those which bear down on the two huts above the treeline in the Presidential Range—Madison Spring and Lakes of the Clouds. In fact, several turbines have been blown off the roof of the Lakes of the Clouds hut, which sits on the rocky shoulder of Mt. Washington, the highest mountain in the Northeast and site of the highest recorded winds on the planet (231 mph). The AMC budgets for an average lifetime of two years for a wind turbine at Lakes, compared to 10 years at a hut like Zealand Falls.
For energy storage, most huts use a bank of deep-cycle, lead-acid batteries. Charge controllers moderate the energy input from the PV modules to prevent battery overcharge. During cloudy weather, propane-powered, 8-horsepower backup generators feed the electrical loads and recharge the batteries with Xantrex inverter/chargers.
Crew members diligently check the TriMetric state-of-charge battery monitors throughout the day, and minimize unnecessary use of electric lights and small appliances. Typically cool weather reduces the energy demand of the highly efficient Sun Frost DC refrigerators. For the better part of the year, the PV and wind systems provide more than enough energy to power the critical hut loads during the summer’s peak visitor season.
In 2006, hut crews started leading guests on “green tech tours” to explain the renewable energy systems and other sustainable technologies, such as the composting toilets, compact fluorescent lighting, and food composting systems. For many visitors, it’s their first exposure to these sustainable technologies and approaches to waste management. “Most people are surprised at how much we do with how little, and how sustainable we are,” notes Pedersen. “They say how they never would have learned about renewable energy technologies if they hadn’t gone to the huts.”
Since the first simple stone hut was built in 1888—just six years after Thomas Edison opened his first power generating station in Manhattan—the hut system has evolved to strike a fine balance between encouraging conservation through recreation, and putting conservation and clean energy generation into real practice. Renewable energy has become an integral part in achieving both. These systems, says Pedersen, “show the AMC’s mission of moving forward, with low impact, while keeping the tradition of the huts alive.”
Jonathan Mingle is a master’s degree candidate in the Energy and Resources Group at the University of California–Berkeley. He is a former Zealand Falls Hut caretaker.
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