REMOTE TELECOMMUNICATIONS AT SCHOOL HOUSE PEAK

Background
Members of the Yurok Tribe of northwestern California wanted reliable telephone service. But in their remote reservation deep in the Klamath River Valley, installing a telephone system was no easy task. Far from main phone lines and cell phone repeaters, the most reliable way to supply phone service was via a series of microwave transmitters that relayed telephone signals. A key repeater station in the chain was located on top of Schoolhouse Peak in Redwood National Park, miles from the nearest power lines. Power for the station was provided by a photovoltaic (PV) system. But PV panels alone could not provide adequate power during Humboldt County's long, dark rainy winter season, and the National Park Service does not permit fossil fuel-powered generators inside the park. Therefore, an alternative source of back-up power was needed. A fuel cell filled the bill.
Click to see maps of the area or the view from Schoolhouse Peak through the seasons

Application
The microwave repeater was located at a fire watchtower (shown at right--the large dish is for the microwave signal) and drew a continuous load of 100 Watts. During the day, the repeater was powered by solar panels (visible on the south face of the tower), and the excess energy was stored in batteries. Over long periods of cloudy weather when there was not enough sun and the batteries ran down, the fuel cell generator turned on and provided power for the microwave repeater.

System Description
The fuel cell system, shown below at right, was located inside the watchtower. The fuel cell stack itself, visible at the center of the system, was a relatively small 34-cell unit. When the fuel cell was running, it generated enough power to run the microwave repeater and its parasitic loads. It was fueled by hydrogen gas stored in 12 industrial gas cylinders that were manifolded together. The hydrogen gas cylinders were refilled by truck after about 1000 hours of operation, approximately 2 months in the winter. In the summer, the PV array carried most of the load.

System Operation
The system first went online in October 1999. It ran without incident for 3,239 hours over 229 days. The stack ultimately failed when high ambient temperatures caused the stack to overheat, developing a cross-leak. An improved and rebuilt stack was subsequently installed and operated for 3,836 hours over 269 days. The stack was again replaced in June 2002. In all, the system logged over 8,000 hours of run-time. The stack operated at a net efficiency of 49% (Lower Heating Value) and consistently maintained the system batteries at a minimum of 50% state of charge. In May 2002, the Yurok Tribe added 8 solar modules to the PV array and replaced the battery bank. Shortly thereafter, they added a police radio repeater to the system, significantly increasing the electrical load. In May 2003, land line telephone service was installed at the upper reservation, making the microwave repeater system obsolete. The photovoltaic system and batteries were considered sufficient to support the police radio repeater without additional backup, so the fuel cell stack was retired from service.

Advantages
This fuel cell generator was an important technological advance compared to the gasoline-powered generator that would have traditionally been used in this type of application. A gas generator requires fossil fuels and produces air and noise pollution during operation. If gasoline fuel should leak, it is toxic to soil and water. On the other hand, the fuel cell requires hydrogen gas and produces only pure water and electricity during operation. If hydrogen fuel should leak, the gas, which is lighter than air, would escape harmlessly into the upper atmosphere, rather than poisoning the soil or water in the park. The Schoolhouse Peak fuel cell was nearly 50% efficient in the conversion of fuel energy to electricity, while a gasoline-powered generator is only about 15% efficient. And a gas generator makes a lot of noise (similar to a lawn mower), whereas the fuel cell ran quietly and cleanly, emitting absolutely no noise or air pollutants into the pristine environment of Redwood National Park.

SERC Director Peter Lehman inside the hydrogen gas storage shed