Some engineering design projects click, hum or make no sound at all. Lettuce Turnip the Beet may be the first at Rice University to gurgle.
“The pumps are always going,” said design team member Dominique Schaefer Pipps. “The water never stops moving, keeping the plants alive.” The punningly named Team Lettuce Turnip the Beet has designed and built what is known technically as a “produce cultivation machine,” which resembles an oasis of greenery at Rice’s Oshman Engineering Design Kitchen (OEDK).
Sprouting from tiers of PVC pipes are lettuce, garlic and other vegetables, grown hydroponically — that is, without soil — and kept fresh by a pump circulating 55 gallons of water. The project was commissioned by a “zero-resource house” on the campus of Chalmers University of Technology in Gothenburg, Sweden. Previously, Chalmers partnered with another Rice team to create BioBlend, a variation on the in-sink garbage disposal that separates food waste from water and simplifies the composting process.
“The emphasis is on using as few resources as possible, using little energy and wasting nothing,” said Sanjiv Gopalkrishnan. He and Schaefer Pipps, along with team members Jared Broadman and George Dawson, are all seniors in mechanical engineering at Rice.
The team achieved its goal to produce sufficient food to make one salad per week for one year, all in an apartment environment. The original prototype was built last November after two months of brainstorming. It’s a much bulkier, space-consuming model and has been moved outdoors to a fenced-in area behind the OEDK. It remains overgrown with sprawling tomato plants, broccoli and Swiss chard.
“We wanted to minimize power consumption and environmental impact, but maximize nutritional content and yield,” Dawson said. “The machine should coexist with humans in a rather small living environment. Noises, lights and smells shouldn’t interfere with the sleep cycle or life in general, and basic maintenance should be kept simple.”
According to the team, the device consumes about 900 watts, about as much power as a microwave or medium window air conditioner, and runs off one outlet even after replacing fluorescent lights with LED growing lights to improve the health of plants farther away from the fixtures.
The new prototype stands 8 feet tall, but its wooden frame and six levels of vinyl pipes are nearly flush with the wall. The biggest change is using square rather than round plastic pipes, which have a larger internal surface area and move more water. The frame is held together with pegs and friction and uses no glue or nails; the entire device weighs around 70 pounds.
George Dawson, a member of Lettuce Turnip the Beat, a senior engineering design team at Rice University, works on its hydroponic garden. The team's initial goal was to produce sufficient food to make one salad per week for one year in an apartment environment.
“That makes transporting it easy. We have to get it to Sweden. This is like Ikea for toddlers, with really big parts,” Broadman said.
The team will install sensors to automatically monitor pH levels, nutrients, temperature and other factors before the device is installed in Sweden. The current setup uses one reservoir but the students expect a multiple-reservoir system, each with varying levels of nutrients, could permit fine-tuning the nutrient requirements of various plants.
The team is advised by Matthew Elliott, a lecturer in mechanical engineering, who said, “My job is easy. We meet once a week for updates. The students have taken care of everything.”