Installing shade curtains in a greenhouse may seem counterproductive, but the new computer-controlled system of curtains in the UI greenhouses controls the sunlight, reducing energy and labor costs.
"Before we had the curtains, we had to spray whitewash on the greenhouses every summer to keep the rooms cool, and then every fall we had to take it off," said Ruth Green, a UI plant care facility coordinator who recently retired. "The whitewash itself was an environmentally friendly product but applying it and rinsing it off every year was labor intensive and required special safety measures because it had to be done on high ladders. Whitewash is archaic when compared to today's standards."
Whitewash was applied to diminish the sun's intensity and reduce the interior temperatures. On cloudy days, the rooms became very dark.
An interior view of the shades as they begin to unfurl.
Photo by Debra Levey Larson
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"There was nothing we could do except turn the lights on to compensate for the lack of sun - which used electricity and wasted energy," Green said. "With the curtains, the system monitors the light and room temperature all the time, so on a cloudy day the curtains stay open, using natural light more efficiently. We're not running the electric lights nearly as often. Now we can take advantage of the sunlight and regulate it."
The curtain systems utilize information from a weather station outside the greenhouse that monitors light levels, temperature and humidity, wind speed and direction. Every plant room has a sensor that measures the temperature and humidity inside and a control box in the corridor outside each room that was already turning the lights on and off and regulating the temperature. New modules were installed and a central PC communicates with each of them in the rooms equipped with the curtain system. It reads the data every 10 minutes and automatically adjusts the curtains based on the conditions of the day.
"Researchers who conduct experiments in the greenhouse specify the number of watts per meters squared of sunlight per day that they want, so each room can be programmed for the light intensity required for that specific crop," said Nathan Deppe, plant care facility coordinator. "We have much more control over light levels, which results in higher quality of research, savings on energy, as well as the costs of labor and materials for applying and removing whitewash."
The curtain is made up of alternating stripes of clear material and reflective aluminum strips. In the winter, the curtains act more like a blanket. They close as soon as the sun goes down and/or the lights go off in order to retain the heat.
"All new research facilities have energy shade curtains. They're state-of-the-art greenhouse technology, but they're expensive," Green said. "We already had curtains in 18 of the greenhouse rooms and were fortunate to get an interest-free loan from the UI Student Sustainability Committee to install them in nine more rooms."