Hydro Project Looks Skyward for Energy
A solar-powered hydroponic greenhouse is going up at a California high school, thanks in part to an energetic group of students and a grant from a utility.
The greenhouse is being constructed on the grounds of Mt. Diablo High School in Concord, Calif.
Mt. Diablo science teacher Sandy Johnson-Shaw and a University of California-Berkeley environmental science graduate student developed a plan for a solar-powered hydroponic greenhouse. Johnson-Shaw runs Mt. Diablo's health and biotechnology academy, which offers curriculum tailored to students interested in pursuing a career in the health sciences.
Project plans were developed during the 2004 school year. The plans together with a grant proposal written by graduate student Thomas Azwell. were submitted to Pacific Gas & Electric Co. (PG&E). Azwell's proposal featured a hydroponics lab patterned after one originally designed and built by Lou Dee, a recently retired NASA chemist.
The utility agreed to give $5,000 to the project. The money will be used to buy supplies, including the greenhouse and solar panels.
The Rion solar greenhouse measures roughly 16 feet by 9 feet by 7 feet and sits over a cement pad that used to hold bike stands. It was purchased at Costco for $2,400. Costco also donated $100 to the project.
Rion greenhouses, which come in easy-to-assemble kits, were developed in Israel, where water is scarce.
"What's nice about the Rion greenhouse is that there are no tools required," Azwell said. "This allow students to be involved in its assembly."
Once the solar panels are installed, most of the energy needed to run the greenhouse will come from the sun.
The lab is actually part of a larger plant ecology program that Azwell has designed for the school and which includes several sciences, such as chemistry and physics.
"Hydroponics kind of works right into that," Azwell said. "My programs always go beyond just the greenhouse. I add sustainability components such as recycling, food waste collection, and examples of renewable energy."
Plants will grow in several ebb-and-flow, or flood-and-drain, beds that sit atop tables in the greenhouse. The beds, which sit on legs, are anywhere from 6-8 feet long, 2 feet wide and 8-9 inches deep.
The differential in height provides a grade of around 10 percent that allows for the draining of the nutrient solution so that it can be recycled through the sump pump.
Johnson-Shaw's students will be growing mostly vegetables in the greenhouse. As the program progresses the first vegetables produced will be sold at a student-run farmers' market on campus.
"Our other down-the-road goal is that we will be able to supply the vegetables for our on-campus restaurant," she said, which should help generate continuous funding for the program.
Vegetables, which are direct-seeded into the pea gravel, will be grown from seed originally propagated by Azwell in a greenhouse on the UC-Berkeley campus. After that the students will harvest their own seed from plants that are allowed to bolt. The seed will be sprinkled on the top of the pea gravel and worked into the medium by spreading a hand over it.
"It's really important to start from seed, for the lesson it teaches the kids, but also this keeps out any kind of soil-borne diseases. This helps eliminate having to use pesticides," Azwell said.
One particularly interesting aspect about the project, one not found in other closed hydroponic systems, is that some of the nutrients that will be supplied to the plants will be available as worm by-products in leachate form called worm tea.
"What we're trying to do is develop a zero-waste school," Johnson-Shaw said, "where the kids bring their food waste to the vermiculture beds, and the worms will break it down. We'll use the worm castings and worm juice as part of the nutrients."
In addition to the eight macronutrients provided by the worm tea, a seaweed extract that carries with it 8 micronutrients is added to the nutrient tank. Plant trimmings will also be fed to the worms.
Azwell, who built a similar hydroponic system in Southern California, said that it's sometimes difficult to convince teachers of the value of a plant ecology program.
"It seems like extra work to them, but once you get the infrastructure in, such as the greenhouse, next thing you know everyone is curious about what's going on, and the other teachers begin to see the connections to their curriculum and, most importantly, the benefits of hands-on learning for the students."
Azwell and Johnson-Shaw are writing another grant in hopes of being awarded $20,000 by PG&E to purchase a 1-kilowatt solar panel that will greatly increase power into the greenhouse.
"It'll essentially run anything we plug into the plant ecology lab," Azwell said. One item he has in mind is a swamp cooler to keep the greenhouse cool and humid in warmer months.
