Rice University engineering students develop 'greenhouse' for city-dwellers

Vegetables are part of a healthy diet, but urban apartment dwellers in some places around the world don’t have regular access to them. A group of Rice University senior engineering students set out to remedy that for their capstone design project.

Team Växthus — mechanical engineering students Mary Bao, Mike Hua, Jack Kaplan, Harrison Lin and Colin Losey and electrical engineering student Lingbo Chen — has developed an automated, modular, indoor greenhouse to provide high-throughput food growth aimed at young professionals in urban settings.

“This allows them to grow fresh produce, everything from leafy greens to herbs to root vegetables,” Lin said.

Växthus (Swedish for greenhouse) was developed for the HSB Living Lab at Chalmers University of Technology in Gothenburg, Sweden. The lab is a residential community of 29 apartments for students and visiting researchers, all of whom are involved in finding solutions for more sustainable living. The Living Lab partnered with Rice on a previous project to develop a device to simplify composting at home.

The Rice students said their greenhouse project furthers that mission by enhancing city life.

The team worked at Rice’s Oshman Engineering Design Kitchen and was advised by Matthew Elliott, a lecturer in mechanical engineering, and Gary Woods, a professor in the practice of computer technology and electrical and computer engineering. Its goal was to produce an efficient and attractive prototype small enough for an apartment. The result is a wood-paneled greenhouse with a clear acrylic front. “I think we did really well, thinking about how it would feel as an outside user,” said Hua. “We wanted to create a product that made the user interface easy.”

The greenhouse is a soil-based rather than hydroponic system. That allows users to grow a greater variety of vegetables, as hydroponic systems don’t have the space for the deep-root systems that vegetables like carrots require.

The fully automated Växthus design controls lighting and watering with a closed-loop system. Moisture, temperature and humidity sensors collect data and send it to a touchscreen display, with on and off switches for water and light. When the soil is dry, the greenhouse releases water for the plants. When it senses that the soil’s moisture level is fine, it turns off. The team added manual controls so users can override the automatic functions.

A pump system lets water drip from the ceiling to mimic rain and reclaims it from the drip tray below. “Any excess water will percolate through into the tank below,” Kaplan said. That allows the device to recycle water.

During the design phase, the team grew kale and herbs, and now has carrots and radishes growing in the greenhouse.

The team is building two more of the devices and will ship them to Sweden, and in June it will install them at the Living Lab, where residents and researchers will continue testing the units, tweaking the automated system as necessary and growing different vegetables.