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Greenhouse climate model optimises yield

Measurements show that the climate inside a greenhouse can vary considerably. Reducing the variations leads to higher yields, improved quality and lower heating costs - also in greenhouses with active ventilation. TNO is working on a model that identifies local differences in flows, temperature, humidity and concentrations of substances, and invites entrepreneurs to participate in the development process.

Plant production in a greenhouse depends mainly on the amount of light and on temperature, humidity and CO2 levels. There are systems for controlling and coordinating all these factors. The effect of such measures has major consequences for the profitability of horticulture firms. Growers already invest heavily in climate systems and climate control, but don't always see an optimum return on their investment. The main problem is the lack of information on how sunlight, wind, plants and systems influence the local climate in a greenhouse. TNO researcher Leonard Baart de la Faille: "When greenhouses are modified or when new ones are built, detailed information is often lacking, simply because the tools don't exist. Decisions are often made on the basis of smoke tests that can assess air flows reasonably well in quantitative terms, but no more than that."

Greater insight

TNO is working with businesses to develop a Greenhouse Climate Model that models the relationship between air flows, temperature, and concentrations of substances such as moisture and CO2. The Greenhouse Climate Model has two functions:

  1. It is a design tool for horticulture greenhouses. The tool mathematically tests innovations and enables variants to be easily compared. In the longer term, it forms the basis for an application that every greenhouse designer will make use of.
    It is the first step towards a control model for greenhouses. The challenge is to create an acceptable climate in all parts of a greenhouse, and to do so efficiently and using as few sensors and actuators as possible. This can only be done with a control system based on a model such as the Greenhouse Climate Model. As a first step, the model is already being used to advise growers, for example if excessive concentrations of hazardous substances accumulate. The technique can also be used in other types of building, such as factories.

User-friendly

Baart de la Faille explains that the model is user-friendly and produces calculations quickly: "That is why it is being made and validated specifically for large horticulture greenhouses. It is based on strict tolerances for air temperature, humidity and CO2 levels, and for PAR, NIR and FIR radiation that influence growth and temperature conditions. These tolerances, like the influence of the plant on the climate, vary widely from crop to crop, and also need to be modelled. We already know that the principle is an applicable one, and we are working on the further development of the model. We're doing this in collaboration with interested companies, and we would welcome the involvement of additional companies. They will be able to stay up to date with the latest developments and quickly incorporate the model in their processes."

Leonard Baart de la Faille MSc

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