The Tongass National Forest, the Nation's largest national forest, covers a large portion of southeast Alaska. The majority of its sprawling landscape is divided into many remote islands with few roadways. Because of the difficult and complex terrain, Forest Service employees use four barges to create mobile remote work camps. One of the barges—the Chickamin (figure 1)—was procured in 1983.
All of the barges are fitted with two 20-kilowatt (kW) diesel generators. They have a 32- by 85-foot steel hull, a 2,900 square foot, two-story house, and 4-inch-thick walls. Unfortunately, the barges consume a lot of diesel fuel when deployed as remote work camps.
The Chickamin barge was retrofitted in 2003 as a clean energy solution and to address the increasing cost of diesel fuel in the remote islands. The upgraded barge has a solar array that powers most appliances and electronics, a high-efficiency inverter, and a battery bank. These upgrades cover most of the barge's day-to-day electrical needs.
The solar array produces 2 kW of power under optimal conditions. The solar panels (figure 2) charge a 48-volt, 840-ampere-hour battery bank based on a 20-hour rate of discharge. The inverter converts the direct-current (dc) output of the battery bank to alternating-current (ac) output to run various appliances on the barge, such as refrigerators, microwaves, and computers. The inverter has a 95-percent efficiency rating when converting output from dc to ac. The batteries also have a 6-kW generator to augment the system if the solar panels can't keep up with energy demands.
The barge's energy-efficient components include 4-inch-thick walls with an R11 thermal rating (figure 3) and a Toyo heating unit with a 90-percent efficiency rating.
The two 20-kW diesel generators serve as backups for each other when energy demands are high, mainly when cleaning and filtering water or running energy-consuming devices, such as cooking stoves. The diesel generators no longer run continuously with the Chickamin barge's upgrades, reducing fuel consumption by 75 percent. The barge is a leader in the movement toward cleaner energy.
Figure 2—Closeup of the Chickamin barge's
Figure 3—The Chickamin barge's 4-inch-thick walls have an R11 thermal rating.
For more information on the Chickamin or other barges, contact Kenton Bowers, supervisory civil engineer, Tongass National Forest; 907–228–6223, firstname.lastname@example.org.
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