Penn State researchers from theatre arts and horticulture have collaborated with the Office of Physical Plant (OPP) to fine-tune lighting for improved plant growth and energy conservation in greenhouses.
Light-emitting diodes (LEDs) have been used for years because of their energy-efficient properties and theatre arts professionals are well aware of the lighting sources' ability to enhance drama on stage. But now a research grant, secured in 2010, is helping to show how the same lights can have a multi-pronged benefit in greenhouses. As an undergraduate majoring in theatre production, Daniel Frechen noticed how easy it was to create realistic sunrises and sunsets using the extreme control flexibility of LEDs.
The difference in size between plants grown under LEDs (left) and
those grown under traditional lights is noticeable.
Frechen has an agricultural background, and while finishing a minor in horticulture, he began to wonder if blue- and red-wavelength LEDs could benefit greenhouses and plant growth chambers. Frechen's initial Summer Discovery Grant to explore this potential led to a more comprehensive Sustainability Seed Grant, a program administered by Penn State Institutes of Energy and the Environment (PSIEE) in a partnership with Outreach, OPP, the College of Arts and Architecture and the College of Agricultural Sciences.
With Kenyon as lead investigator, the team explored how LED technology could reduce energy consumption in plant growth chambers, which could lead to its use in greenhouses and plant-growth rooms. Traditional growth chambers use power-hungry fluorescent and incandescent lighting or high-pressure sodium and metal-halide. Bulbs often have to be replaced yearly at a high cost. The excess heat from these less-efficient sources has to be removed from the chamber by built-in compressors, and research data was often lost if this equipment turned off for even an hour. Industrial light sources for growth chambers are pretty standardized, and this study examined a totally new approach. The experimental protocol was straightforward. The team retrofitted a growth chamber with LED lighting and ran growth tests with a second "stock" chamber as a control. All aspects of the chamber performance were evaluated, including electricity, heat, cooling, watering, humidity, maintenance and plant growth.
The team anticipated and found great potential savings for both Penn State operations and research. LEDs not only provided substantial lighting savings but also reduced the need for compressor cooling, associated maintenance and watering. Since the chamber lighting runs cooler, there is less evaporation and less stress on the plants. LEDs also will last five to 10 years and need far fewer replacements than the old high-intensity fluorescent and incandescent bulbs.
Even though plants evolved in full sunlight, they don't actually utilize all the wavelengths that sunlight provides. Depending on the plant species, they like blue, medium-red and far-red wavelengths. LEDs can focus the spectrum energy and intensity where it is most beneficial to plant growth. Conventional lighting provides a full spectrum and generates a lot of excess heat, especially in a small growth chamber. Since LEDs can supply only the wavelengths needed, the excess heat is minimized.
LED technology is rapidly evolving and refining. It is in fact, 90 percent more efficient than normal incandescent light-bulb technology.