Area students design and build solar heaters to warm greenhouse
What do you get when you combine wood, window glass, a space blanket, aluminum cans, black paint and a 25-foot dryer duct?
A homemade solar furnace, of course.
This summer, 20 youth between the ages of 14-17 from around the region have been busy designing and building solar furnaces at Camp Rabideau, an old Civilian Conservation Corps camp located south of Blackduck.
The solar energy project began earlier this year when Blackduck High School won a solar furnace design competition funded with a grant from the University of Minnesota Clean Energy Resource Teams.
Area schools were invited to take part in a solar energy education project, where participating schools arranged teams to research, design and build a passive solar air heater. The heaters were judged by engineers with Rural Renewable Energy Alliance, headquartered in Pine River.
Blackduck's winning solar model is now being used as a template for youth at Camp Rabideau's summer youth programs.
The youth program was given $300 by RREAL to build four 6-4-by-4-foot solar heaters that can be used to heat the greenhouse at Camp Rabideau. Heating the greenhouse would extend the growing season by several months, allowing for more food to be grown.
The student workers are paid through funds generated from the Bemidji WorkForce Center and the Rural Minnesota Concentrated Employment Center. So far, the students have made six solar furnace prototypes, or "experimental heaters," each one built a little differently from the next.
"The students got together and designed different solar heaters based on the recommendations from RREAL and the Blackduck students," said youth instructor John Parmeter. "We've been testing the amount of heat daily."
At around noon Tuesday, one of the solar heater thermometers read 133 degrees Fahrenheit. Another read 93 degrees.
"We have one that consistently tops out at 240 degrees or better," Parmeter said. "One started at about 64 degrees and when the sun came out shot up to 240 degrees in five seconds. Now that's heat."
According to Parmeter, there's still work to be done before the group completes the final four solar heaters using the donated materials. The group's mission is to find a model that produces the most heat.
Building solar furnaces from scratch is not easy. It takes a lot of dumpster diving and a few visits to a recycling center, according to Parmeter. All of the solar heater prototypes built by the youth workers are made from donated recycled materials.
While the heaters may look a little bit like over-sized display cases holding zig-zagged tubes, they do the job.
Parmeter said one heater generated so much heat the group had to redo the silicone glue and replace it with silicone tolerant of temperatures 1,600 degrees Fahrenheit and higher.
"We came back and the window had slid off its box because it melted," Parmeter said. "That silicone was supposed to hold in 75 degrees up to 600 degrees."
Once the four solar heaters are complete, the group plans to heat the greenhouse using a unique method.
A large container of rocks will be placed into the ground inside the greenhouse, Parmeter said. The heat from the four solar heaters will filter into the container of rocks throughout the day. At night, when the outside temperature cools, the heat from the rocks will radiate inside the greenhouse and keep it warm.
Parmeter said the solar heaters will be used March through May and then September through the first part of December.
"One of our biggest ideas to think of is how we're going to place the four heaters right next to each other and connect them so the air runs from one to the next without having one overheat," Parmeter said.
Parmeter said he is most proud of how creative the students have been with the project.
One student, he said, came up with the idea to build a frame around the glass panes to make it easier to open the furnace in case something needs to be fixed inside.
Another student thought of the idea to arrange the dryer duct tubing vertically, instead of horizontally, to create a better heating flow pattern.
"They know about convection," Parmeter said. "We've more than doubled the heating temperatures of the Blackduck students' model."
For weeks the students have worked in teams measuring, marking and cutting materials, and finding answers to big questions.
But beyond the physics of the project, Parmeter said, the main purpose of the work program isn't to learn math or science.
"The whole idea here is to have teamwork, develop leadership skills and give them work skills," he said. "It's giving them an idea about what it's like to work towards a goal."
Mary Nipp, an AmeriCorps volunteer contracted with the U.S. Forest Service, said she is proud of what the kids have accomplished.
"The kids are proud and their parents are proud of them," Nipp said. "They are going to step into the future with all this experience."