SBIR-STTR Award

Plants survive when subjected to the day-to-day vagaries of inconsistent weather, but seldom does an individual plant reach its genetic potential in nature. Consistent, predictable plant growth can be achieved only when environmental conditions are consistent from day to day. Individual environmental parameters can be held steady to provide consistent growth, but integrating and coordinating control of the various environmental parameters will be an effective and less expensive means to optimize total production cost while still ensuring consistent growth and productivity. An improved light and CO2 controller will make production of vegetable, flower, pharmaceutical, and other high value crops more economically attractive in greenhouses (compared with outdoors), encouraging more closed production facilities that can be shielded from potential bioterrorism incidents, and possible contamination by nearby incidents. Finally, a major result of using the proposed control unit is to make natural sunlight much more efficacious in greenhouse crop production, reducing need for supplemental light. This reduces dependence on fossil fuels by providing the same growth with greater reliance on natural light and less need for supplemental lighting to achieve the same plant growth and production. Energy conservation can be considered as the most renewable of all energy resources. OBJECTIVES: This project is to develop a marketable environmental controller to improve the productivity, energy-efficiency and cost-effectiveness of locally produced fresh vegetables and other crops in greenhouses. Plant growth requires light but, in many regions of the U.S., winter cloudiness (or a more northerly latitude) limits greenhouse productivity. Supplementing carbon dioxide makes light more effective and less is required. However, ventilation for temperature control wastes CO2 and supplemental lighting becomes the less expensive alternative. Real-time, adaptive, control that optimizes the combination, yet provides identical plant productivity, has significant value. Our first goal is to validate an algorithm to control the daily light integral and CO2 concentration in a greenhouse where the algorithm will control CO2 concentration and the daily light integral target in the most effective and efficient way. Previous work, based on computer simulations using the algorithm, predict supplemental lighting cost can be reduced by approximately half in cold and cloudy regions such as upstate NY. The project outcome will be a stand-alone controller that permits real time, adaptive, control of the daily light integral and CO2 concentration in commercial greenhouses to grow crops of consistent high quality and size, while significantly reducing electricity required for supplemental lighting. APPROACH: Modify the CO2 delivery system currently serving the CEA greenhouse in which the research will be completed. The CO2 storage and delivery system currently in place requires repair of the CO2 tank refrigeration unit, and CO2 sensor calibration. A properly functioning refrigeration unit is necessary to prevent premature and excessive evaporation of the liquid CO2 and its subsequent loss to the atmosphere. The CO2 sensors in the greenhouse must be calibrated and their accuracy assured prior to the new set of experiments. The crop to be grown will be butterhead lettuce grown in a floating hydroponics system. Lettuce is the crop we know best and was the crop used to develop the DLI/CO2 control algorithm. A production pond for the floating lettuce will be fabricated within the experimental greenhouse. The greenhouse to be used for this research will permit a production pond with a surface area of approximately 300 square feet and 1 foot deep. The pond will be constructed of wood, lined with a 20 mil pond liner, and built on the floor, as would be typical of such systems. Nutrient solution recirculation will be installed to provide a pond recirculation rate of approximately once every four hours. We will instrument one section of the CEA research greenhouse on the Cornell campus. A CO2 sensor, quantum sensor, and air temperature sensors already exist in the greenhouse but a dedicated quantum sensor to measure outdoor solar radiation and outdoor air temperature sensor are not available. They will be installed. A root zone temperature sensor will be installed, as will a dedicated dissolved oxygen sensor, electrical conductivity sensor, and pH sensor. Oxygen (from tanks) will be provided to the root zone, controlled to near 8 ppm (saturation with respect to air at room temperature). The software will be developed in two steps. The first step, to ensure rapid availability for testing in the greenhouse, will be completed on a personal computer. The software platform will be LabVIEW. The next task is to test the first generation program and grow sequential lettuce crops using the DLI/CO2 control algorithm. Seeds will be germinated in a separate seedling area within the Cornell research greenhouse area and grown there for 11 days. At the beginning of day 12, they will be transferred to the floating hydroponics system where they will be grown for an additional 24 days, with respacing on day 21 from seeding. Plant spacing will follow that used in previous research to determine the relationship between DLI and CO2 to achieve the same plant mass at the end of 35 days from seeding. Growth data will include individual and average fresh and dry masses as well as compiled environmental data for each cropping period. At least three crops will be grown to maturity at different times of the year to assess utility of the control algorithm under a variety of weather situations. A stand-alone version of the controller will be designed (on paper). The design will be one basis for submitting a Phase II proposal. Design will include component selection, single-board component layout, and selection of I/O devices, at a minimum

Supplemental lighting is necessary for mid-winter production of greenhouse crops in many climate zones, done in a way that promotes quality, consistency, and marketable quantity. The goal of the proposed work is to achieve a working prototype of a marketable greenhouse environment controller that coordinates the daily light integral and carbon dioxide concentration in plant production facilities in a way suitable for and optimized for installing in commercial greenhouses. Our Phase I software development and testing has prepared us for the next step, to design, fabricate and market test an advanced prototype ready for an anticipated move to market. Relationships between the light integral and CO2 for spinach, basil and arugula, will be developed to expand the knowledge base that underlies the control program to a wide variety of crops. The control program will be enhanced to include a capability to permit greenhouse air temperature to rise by up to 3 C during midday, with lower air temperature later in the day to compensate. Temperature averaging can apply to the times of year when CO2 is of benefit but weather is just warm enough, or the supplemental lighting adds just enough heat, that modest ventilation is required to maintain the blueprint air temperature. OBJECTIVES: The goal of the proposed work is to achieve a working prototype of a marketable greenhouse environment controller that coordinates the daily light integral (DLI, or light sum) and carbon dioxide concentration in plant production facilities in a way suitable for and optimized for installing in commercial greenhouses. Supplemental lighting is necessary for mid-winter production of greenhouse crops in many climate zones, done in a way that promotes quality, consistency, and marketable quantity. Our Phase I software development and testing has prepared us for the next step, to design, fabricate and market test an advanced prototype ready for an anticipated move to market. The proposed controller design will consider costs, hardware reliability, capacity to upgrade, and suitability for installing in the difficult aerial climates of working greenhouses both as a stand- alone plug-in to existing control systems and more importantly for now, as an integrated part of an already robust control system. Commercial production and installation will begin after the Phase II project is completed. Based upon our collaborative relationship with a market leader in greenhouse environmental control systems, we anticipate that our first successful commercialization will be a licensing agreement. APPROACH: Relationships between DLI and CO2 for spinach (Spinacia oleracea), basil (Ocimum basilicum) and arugula (Eruca sativa), will be developed to expand the knowledge base that underlies the control program to a wide variety of crops. Combinations of DLI and CO2 that provide growth comparable to that using ambient CO2 will be selected to develop a relationship in the form previously obtained experimentally for lettuce. This work must be done during winter. Summer experimental activities will focus on continued testing of the evolving control software and hardware in a greenhouse on the Cornell University campus. The control program will be enhanced to include a capability to permit greenhouse air temperature to rise by up to 3 C during midday, with lower air temperature later in the day to compensate. Temperature averaging can apply to the times of year when CO2 is of benefit but weather is just warm enough, or the supplemental lighting adds just enough heat, that modest ventilation is required to maintain the blueprint air temperature. Additional enhancements will be explored, through simulation, to be implemented following our Phase II work. One is to expand the control algorithm to deal with time of day (or, day ahead) electricity rates in addition to on- and off-peak rate schedules. A second will be to quantify the potential benefit of adding a modest amount of air conditioning/dehumidification to a greenhouse to keep vents closed when cooling loads are modest in a strategy to increase the number of hours during a year in which CO2 can be added with net benefit. A third will be to explore adding BACnet communication protocols to the controller capabilities to permit integration of the control with larger buildings such as research institutes, government buildings, and university research facilities, thereby expanding the potential market