As rapid urban population, global warming, energy consumption, and water supply issues continue to mount, controlled environmental agriculture or CEA is becoming increasingly important amongst growers needing sustainable and readily available crops regardless of location or climate. LESA’s Plant Science team is helping to address these issues by utilizing technology-based approaches that allow for scalable crop production with consistent and more predictable outcomes in greenhouse and vertical farm settings with unique engineered solutions.
Led by Sr. Plant Scientist Elsebeth Kolmos, the team is developing integrated lighting, sensing, and control systems that will utilize machine learning and artificial intelligence to optimize the spectral power distribution of lighting with minimal energy consumption to reduce food waste from improper growth techniques, decease harvest-to-table times, and maximize crop yield for higher-value CEA produce.
What Plants Tell Us – Stress and Biology
According to Dr. Kolmos, ‘plants are experts in sensing and using different wavelengths of light’. She is currently conducting lighting experiments on several varieties of lettuce. One experiment aimed at determining whether LED lights save more energy than traditional fluorescent lights without compromising crop yield or quality control such as changes in appearance, nutrition, and biomass. Another, building on the work started by Lithuanian plant physiologist Jurga Miliauskiene, on the effects of pulsed light ‘doses’ for micro-second periods to indicate whether dark periods in the growth cycle can be increased to save energy. Kolmos’ initial results are generating data that aligns with the available literature likewise indicating increases in plant biomass when compared to constant light with the same dim-light interval (DLI). She notes that at a high frequency level, pulsed lighting can increase the size of baby-leaf lettuce. Kolmos will continue to test more frequencies with different duty factors or dark periods, and analyze the effect on pigmentation and nutritional quality.
Plants have their own unique yet natural responses to various wavelengths of light. Just as there is a direct correlation to plants’ production of chlorophyll and sunlight, plants have an automatic UV avoidance response. If plants become too stressed from various wavelengths, they can change the level of pigment molecules. Pigment is responsible for color quality of fruits and vegetables such as anthocyanin (or red pigmentation) – a desirable color in certain superfoods which have a very rich anthocyanin pigmentation to indicate nutrition. LESA uses a spectrophotometer to quantify biological pigments in assay samples, which indicate how the plant is responding to the light index. If the light index is too high, adjustments can be made during the growth cycle on how much stress is good stress and how much and the plant will change to achieve the desired efficacy. Continuously monitoring the anthocyanin levels can tell researchers and growers alike much about the appropriate light doses and light recipes needed to optimize plant development over the growth cycles.
What We Tell Plants – Light and Location
To create the optimal light doses for plants grown indoors, LESA engineered its own Tunable Irradiant Growth Efficacy Research (TIGER) lighting solution. The TIGER Light is a six-wavelength modular fixture that can flexibly cover a wide range of growth area dimensions and dynamically adjust spectrum and intensity to evoke specific physiological responses from the plants. The modules use a custom Light-emitting Diode (LED) design in which all wavelengths are combined in a single LED package for superb color mixing at any distance from the light source. Due in part to the novel design and supremely efficient color mixing capabilities, the TIGER Light improved outcomes in the plants grown in LESA’s Growth Laboratory. LESA’s lighting engineers are currently working on a full redesign of the TIGER Light, TIGER SHARK (Switching Hardware for Advanced Research Kinetics), that will take it out of the lab setting for more commercial orientation with more customizable capabilities to accommodate different sized growth chambers, specific light dose recipes/algorithms, and a higher-Hertz pulse rate.
The Spectral Acquisition Sensor System or SASSy, measures solar spectrum over a full year (365 days) cycle taking between 180 and 300 measurements per day. It has accumulated 30 GB of data collected since 2019 from the greenhouse at Cornell University in Ithaca, New York. The purpose is to record multiple years to compare year to year, season to season, day to day, time of the day measurements to more fully understand how the solar spectrum changes in the greenhouse through atmospheric correlations to take supplemental lighting and shading from the lab into the greenhouse. To understand precisely when and how much solar supplemental lighting is needed for different crops.
When the team was asked how the solar spectrum changed over time, “no one really knew,” says Rick Neal, LESA’s lead engineer for horticulture lighting solutions. “No one had really been studying it from a technology-based approach, to get the data we could measure the solar spectrum where it was needed – in the greenhouse.”
SASSy can help growers know when supplemental lighting is needed to control what plants see and how they will respond to the varying light intervals and indices over time as it pertains to the collection location. But is just looking at lighting enough to understand the changes in the sky?
The integration of SASSy data into the Lighting and Shading System Implementation (or the LASSI) currently used in greenhouse operations at Cornell, is a robust tool taking still more of the guesswork out of CEA. More than just cloud cover affects light conditions and how to visualize the spectral data overtime. Once integrated with SASSy, the LASSI will be a dynamic control system using spectrally tunable supplemental lighting to hit targets established for each wavelength band measured. LASSI’s supplemental lighting and shade control will correct for conditions such as cloudy vs. sunny days, summer sun vs. winter sun based on photon intensity and weather data from the New York State Mesonet and the local stations (the ones near Ithaca) that feed it, to find correlations on how to implement the right correction.
Those implemented in situ, SASSy, and LASSI allow for sophisticated control over the complex operations of indoor farming. More work is needed but LESA and GLASE (Greenhouse Lighting and Systems Engineering Consortium) researchers are working to ensure that research leads to sound CEA protocols and best practices that enable growers and farmers alike to meet the future farming needs.
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Leah Scott, MBA
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Rensselaer Polytechnic Institute
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Email: scottl2@rpi.edu
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