Engineering better farms
Students design sustainable systems, and hone engineering skills, as they help a community greenhouse grow
By Harlan Spector
In fall 2018, Evan Powell ’18, a mechanical engineering student at Case, set out to solve a challenge common to produce growers in northern climates: What is the most efficient way to heat a greenhouse during winter’s deep freeze?
Powell was part of engineering teams that over two semesters designed and built a heating system for Community Green-house Partners, a sustainable urban farm on Cleveland’s East Side. For their senior projects, the aspiring engineers needed to research, design and build a system on the cheap. They had about $200 to work with, plus whatever Community Greenhouse Partners’ executive director Timothy Smith could kick in.
Their project was to install a “rocket stove,” a high-efficiency wood-burning mass heater for the hard-shell greenhouse. Under the guidance of Sunniva Collins, PhD, an associate professor in the Department of Mechanical and Aerospace Engineering, they studied the heat capacity of oak and other woods, average winter temperatures and days of sunshine, and figured out how much energy would be needed to keep temperatures a comfortable 50 degrees to grow lettuce on the coldest of days.
“We wanted to create a solution that would allow them to grow food year ‘round,” said Powell, who now works as an engineer for a Colorado aerospace company. “We couldn’t use any material we wanted. We had to be creative in our solutions because we needed to trade off efficiency for more readily available and inexpensive materials.”
The rocket stove is an assemblage of horizontal and vertical tubes atop sections of old 55-gallon drums. There are two combustion chambers in the tubing. Temperatures inside the stove reach 2,000 degrees, which heats a bed of pea gravel that acts as a radiator for the greenhouse.
“I run the stove for an hour and the gravel stays hot for three hours,” said Smith, founder of the non-profit farm on the grounds of a former Catholic church at East 65th Street and Superior Ave. “We grew lettuce all winter without using electricity.”
For the past few years, Collins, a friend of Smith’s from their Cleveland Heights High School days, has had her seniors work on sustainable systems for Community Greenhouse Partners. Besides the rocket stove, their hands-on experiences have included developing a rainwater cistern design, a solar-powered irrigation system (using a car battery and solar panel), and an aquaponic system, which involves raising fish and hydroponic plants together in an integrated system (basically, converting fish waste into nutrients for plants).
During a recent tour, Smith pointed out the tanks and gravel beds that make up the aquaponic system. Trout go in one tank, and carp in another. The farm feeds compost to the carp, and feeds carp minnows to the trout.
“The only thing we need to add is water,” Smith said. “We can harvest vegetables and eat the trout. This produces a complete diet. It’s got everything you need to survive.”
Smith finds opportunities for projects that students can do for the farm.
“He came up with a list of two or three we could do every year,” said Collins, who is also president of the Case Alumni Association. “The students take what they are learning in class and apply it to real-world situations. They have to be innovative, thinking about how to do it in a way that is cost effective. I always tell students, assume your budget is zero.”
URBAN FARM, ENGINEERING CLASSROOM
On a sunny but cold February after-noon, mechanical engineering majors Alexander Edwards, Jiahe “Noel” Chen and Ryan Materna converged on the farm between classes. They had come to discuss with Smith their senior capstone project: A plan to heat and cool a 50-foot long greenhouse with geothermal energy.
Their plan entailed digging eight feet into the earth to bury a network of pipes, designing a means of blowing air through the pipes cheaply, and solving intricacies of heat transfer and energy balance.
The students brightened when Smith told them their system, if successful, could help greenhouses everywhere. All three expressed enthusiasm for the hands-on lessons, especially in pursuit of cleaner, more efficient systems.
“Renewable energy is something I’m interested in, so it’s great to see it applied,” Edwards said. “I’m learning a lot about heat transfer, just a lot about sustainability.”
The engineering students are among several hundred Case students who every year help out on assorted community service projects at the three-acre farm. Students who are interested in sustainability are attracted by the farm’s mission to provide organic, locally grown produce at low cost to urban neighborhoods.
The farm surrounds the former St. George Catholic Church, two-and-a-half miles from campus. It’s a collection of hoop houses, a greenhouse, fruit trees, a chicken coop and compost piles. Coming soon will be a vermicomposting pile, where worms will turn food waste into compost to fertilize the many varieties of tomatoes, peppers, herbs, greens and microgreens grown on the farm.
Collins’ students focus on water and electricity because those are the biggest expenses at CGP.
One of the recent projects was the design of a solar canopy that will allow the farm to capture and store energy. A future group of students will work on that. Through the projects, students gain experience in data science, budgeting, deadlines and deliverables.
The process often involves trial and error. On tap for a next group of students is reengineering tank beds of the aquaponic system. Smith said the initial tanks they used shifted in the freezing ground and they also leaked.
“That was an oversight we didn’t expect, so we have to rethink the materials,” Smith said.
TRY, TRY AGAIN
It’s all taken in stride. The farm is a place to experiment with new ideas or recreate old ideas. Designs are sometimes iterations to be improved upon by the next group of engineering students.
“The big takeaway for me was learning to be more service-oriented as an engineer,” Powell said. “We worked to come up with a solution that was scalable, that the farm could reproduce.”
Civil engineering major Madeleine Harris ’18 first heard about Community Greenhouse Partners from Powell, her fiancée. She wanted to be involved.
“I care a lot about sustainability. I saw an opportunity working with them to make tangible differences,” said Harris, who now works as a water and wastewater engineer in Denver.
In 2018, her group of four students designed a rainwater harvesting system to capture water from the roof of the church building in a 100-gallon plastic tank. The system would reduce the farm’s demand for water and also reduce the volume of water flowing into the overburdened storm water system. During heavy rains, Cleveland’s aging wastewater system often experiences combined overflow from storm and sanitary sewers that discharges into Lake Erie.
“Reducing the amount of water that goes into storm sewers is really important, especially in a place like Cleveland,” Harris said.
Her group’s model takes into account the farm’s water needs, the fluctuating cost of purchased water, tank volumes and daily rainfall averages. Their model estimates an annual savings of $640 for the farm using the plastic tank. It also calculated savings using a larger, more expensive and longer-lasting steel tank.
Harris said she hopes all engineering students look at designs through a sustainability lens.
“I think there is a big opportunity to implement components of sustainability on every project,” she said.
The farm’s mission, in addition to growing healthy food, is to make discoveries and share the new knowledge. Smith said the Case students help make that more possible.
“They understand the world is changing and science will show us how to live,” he said. “It’s been a joy.”
Want to shop where Case students help grow the food? Community Greenhouse Partners offers its bounty at several area farmers markets and by delivery. Learn more HERE.
Tim Smith, executive director of Community Greenhouse Partners, and his former high school class-mate Professor Sunniva Collins, on the farm.
Innovations like a rocket stove allow the greenhouse to grow vegetables on the coldest days.
With Tim Smith’s guidance, students Ryan Materna, left, Jiahe “Noel” Chen and Alexander Ed-wards are designing a geothermal heating system for a greenhouse.
Mechanical engineering major Alexander Edwards, left, is interested in designing sustainable power systems.