Growing in the upper level of the wooden tower is a profusion of tomatoes, lettuce, radishes, peppers and spinach, all glowing purple in the red and blue light from the LEDs. Then the lights begin to flicker. “What did you do?” asks senior Brian DeKock, a member of Senior Design Team 2: HydroTower. “I just touched this,” answers teammate Jacqueline Kirkman. “You touched it!” echoes Nathan Meyer, another of the team’s engineers. “Wait until Brandon sees it.” As the lights continue to flicker, and the team swarms the tower to solve the problem, Brandon Vonk, the team member who tends the LEDs, arrives. “What happened?” he asks. They explain. “You touched it?” he asks Kirkman. “I told you not to touch it.” Then, Brenton Eelkema arrives. “What happened?” he asks.

It’s April, and team HydroTower has come a long way toward realizing its Senior Design Project: a fully automated home garden system that uses hydroponics, a method of growing plants without soil. The tower currently takes up a lot of room in the team’s cubicle in the Prince Engineering Design Center, and scattered all over the space are the pieces of HydroTower that need further realization: the welter of tubing that brings the plants their nutrients, the sensors that will monitor the plants’ nutrient intake, the microcontroller that will monitor the entirety of the growing process. Also crowding the cubicle is a couch, a computer, a couple of whiteboards covered with calculations, scattered boards, components, wires, sheets of plastic and, sometimes, a pizza.

To construct a hydroponic farm that can fit into a corner of the average kitchen, Team 2—composed of mechanical engineering concentrators DeKock and Kirkman and electrical concentrators Meyer, Eelkema and Vonk—has had to explore not just engineering, but chemistry, plant physiology, physics and a little bit of business. “We think our project should win the liberal arts award,” Eelkema commented.

“This is an ambitious project that requires insights not only in science and engineering, but also in getting the business case right,” said Team 2’s adviser, engineering professor Steve VanderLeest. “It also provided a good opportunity for developing multidisciplinary skills.”

HydroTower began as many Calvin Senior Design Projects do. It was an idea, and it wasn’t anybody’s favorite. Team 2 formed last May as the members’ junior semester came to a close. Traditionally students choose the other students who will collaborate with them throughout their senior year. “Some of it is, ‘Who do I work well with?’” DeKock said.

As the group disbanded for the summer, it pledged to brainstorm senior design ideas online. “Everyone has their favorite project that they wanted to do,” said Kirkman: a camera for the wing of a search-and-rescue plane, a targeted sprinkler, remote-control cars.

On the bottom of Team 2’s list was an idea for an automated hydroponic farm. It was based on an article that Eelkema had read, which proposed building a skyscraper in Chicago devoted to large-scale, hydroponic urban agriculture. As other pet projects died off, the vision of the hydroponic farm grew in the team’s collective imagination.

The deadline for Senior Design Teams to choose their projects landed a week after school started in September. Team 2 decided on HydroTower, and for the remainder of the month, the students mapped out the project, setting milestones, goals and objectives.

In October, the team researched hydroponics, learning about the floating, misting, and flood-and-drain (ebb-and-flow) methods of growing. They visited Mud Lake Farms, a Hudsonville, Mich., purveyor of hydroponic lettuce and herbs.

Then they planned: their HydroTower would be constructed of a 20-by-32-by-32 inch base unit, to house the electronics and plumbing, and two open growing levels, each measuring 24 by 32 by 32 inches. The unit would operate on an ebb-and-flow system, and it would irrigate the plants and dispense nutrients automatically.

The team designed HydroTower to appeal to urbanites interested in local agriculture. “Our slogan is ‘Feeding people more efficiently through hydroponics.’ That’s at the root—ha!—of what we do,” Kirkman said. The team hoped the project might eventually be used in the developing world.

Also in October, the team began growing its first radishes and soybeans in cups for later transplantation into the tower.

In November, Team HydroTower broke the project into components, and each student engineer took one. DeKock would construct the tower. Kirkman would engineer the water and piping. Vonk would create the LED system, using only red and blue lights because those are the only colors of the spectrum that plants absorb. Meyer would program the microcontroller that controls the LED lighting, the pump and valves, and the touch-screen user interface. And Eelkema would create the pH and electroconductivity sensors that handle nutrient control—a system, the team emphasized, that sets HydroTower apart from other hydroponic farms.

“The sensors would input into a microcontroller, which would then use algorithms to decide which nutrients need to be replenished,” Eelkema explained. “The only problem with that is the biology and chemistry research is far more advanced than we have time to cover. Right now I am shooting for a best guess that I know won’t kill the plants.”

For help with areas outside the students’ engineering expertise, they consulted with other Calvin departments. Chemistry professor Douglas Vander Griend helped with the nutrient-control system. Biology professor David Dornbos schooled the team on plant nutrition.

Every facet of HydroTower presented challenges, the team said. “We knew there were parts we underestimated,” DeKock said.

“It’s actually really complicated,” Kirkman agreed, “and we’re learning more than we anticipated.”

In November, the team faced its first industrial review, where it got advice about scheduling and having escape plans in case things didn’t work. That month Eelkema presented HydroTower at Elevator Pitch, one of Calvin’s entrepreneurial competitions. He won $300, and the team added it to the project budget.

During December, team HydroTower put together a design report and a business plan and made its final presentation for first semester. “We also had a no-contact rule over Christmas to give everyone a well-deserved break,” Kirkman said.

In January, the students were mainly occupied with interim classes, though Eelkema, Vonk and Meyer worked on controls while DeKock and Kirkman built a square version of HydroTower.

The tower’s original circular design wouldn’t fit well into a corner. The problem with a square design, said DeKock, is keeping things square: “Jacqueline and I don’t have lots of building experience, so keeping things built to specifications can sometimes be difficult.” Another challenge was keeping the electrical and water systems separate so that the system doesn’t short out.

In February, the team attended meetings on communication and trust—a standard part of the department’s team management strategy—and the students reflected back on first semester. “The hardest thing, really, is communication between the mechanicals and the electricals,” Kirkman said of working on the team. “Sometimes you have similar words and contexts, but you’re talking about two different things.”

It was in February that team HydroTower began to engineer in earnest. Kirkman and DeKock installed the drainage slope and waterproofed the first grow level, and Kirkman and Vonk researched electrode sensing and tested ultraviolet-visible spectroscopy as a viable option for the nutrient system.

At that point, their adviser stepped in. “Professor VanderLeest told us we had to stop researching things and start implementing,” Kirkman said. Team members rely on VanderLeest to keep them focused on the larger picture when they want to obsess on components, she said. “He has really high standards.”

In March, Kirkman built the tower’s water reservoir mixer and pumping system. Meanwhile, Vonk was dealing with the LEDs’ tendency to throw light not only down, but sideways. “This was causing a lot of our light to be wasted towards the side of the HydroTower rather than having all the lights go to the plants,” he said. Vonk engineered the LEDs to function as a Fresnel lens, which focuses light on a smaller area.

The team transplanted the plants into the first grow level of HydroTower, and lights, ventilation, and water feeding were programmed to run off Meyer’s microcontroller. The team went on spring break, and the plants survived. Even in its rudimentary form, the system worked.

That month the team also faced its second industrial consultant review—where it faced grilling from engineering and business professionals—and came out of it feeling like the project was in good shape.

Also in March, Kirkman presented HydroTower at BizPlan, another Calvin entrepreneurial contest, and took the $600 second prize, and the team rolled it into the budget.

By April, although HydroTower had developed a leak in a bulkhead (fixed by epoxy), all facets of the project were humming along. DeKock and Kirkman built and painted the steel frame for the base unit. Vonk began making progress on the power supply. Eelkema finished building the sensors.

And Meyer continued programming the microcontroller to allow a touch-screen user interface and safety systems. “The possible complications of using this system mainly include designing it … so that it is always safe in any type of failure, such as a power outage,” he said. “Another design challenge is to control all of the systems using the limited resources of the microcontroller.”

The second grow level was under way. The base unit, with all its valves, power supply and electrical components, was being installed. The nutrient design system was moving toward final design and installation.

Then the LEDs started blinking. It happened in mid-April, minutes before Team 2 went into a second professional review, but the students weren’t thrown by either the meeting or the lights. “We’ve made this presentation so many times,” Eelkema explained.

Ten minutes later, with three professional engineers sitting opposite in a North Hall classroom, Eelkema commences presenting. The panel interrupts with questions. One of the panelists questions the necessity of the students’ LED system. The team members give various answers. Then Vonk steps forward, clicks to a PowerPoint slide and explains the mathematics behind the lights: “We’ve normalized the area under the sun’s photosynthetic spectral curve in order to model the sun for our plants,” he says. There’s a silence.

“You answered the question. Good for you,” a panelist says. Ten minutes after that, the students are in the hall, greeting the Senior Design Team waiting to present. “How was it?” asks one of the incoming students. DeKock sighs, and Eelkema wrings imaginary tears from his eyes.

Back at the cubicle, HydroTower is still blinking red and blue, and the team re-commences fiddling with it. They’ll continue refining the tower until the annual Senior Projects Night, held Saturday, May 7, 2011, in the Engineering Building. The event is the capstone of the senior design process, and every team dresses up to welcome the public, including family and friends, and present their work. That prospect is daunting, said DeKock. “I mean, if you have a paper, an exam, you get that graded and handed back and put it in your back pocket and forget about it,” he said. “We have to put on a suit and stand in front of this.”

Team 2 doesn’t know what will become of HydroTower. One of their reviewers counseled having the unit redesigned and selling it as a luxury item—and marking it way up. The team says it will think about it. Most of them have jobs lined up or they’re fielding offers. And they anticipate an upcoming conflict: They all want the HydroTower. “It will be the big team fight at the end,” says Kirkman. “Our rock-paper-scissors,” added DeKock.