Workshop on Humidity Control Understanding greenhouse physics for improved growth control March 10 th 2015, Stockbridge Technology Centre Introduction “Global player” with local partners iSii iSii
Workshop onHumidity Control
Understanding greenhouse physics for improved growth control
March 10th 2015,
Stockbridge Technology Centre
Introduction
“Global player” with local partnersiSii
iSii
SensorsSensors
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1 Digital climate control
2 Hydroponics
3 Plant sensors
4 Closed / semi closed greenhouse -> “The New Growing”, LED etc.
5 111111111..
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45 years of experience in Horticulture
How to get the optimum growing climate in any type of greenhouse? Every stage has its learning curve
Program of Workshop
○ Discussions about
● How to have better Humidity control on micro climate level
● How does evaporation work?
● How to have better transport of elements?
● How to save energy?
● What’s best to invest in ?
○ But first we need to know something very basic$.
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Translating the needs of the plant into Greenhouse physics to!
http://hnt.letsgrow.com/psychro : Hoogendoorn Psychro App explains Greenhouse Physics
Basic terms of humidity
Relative Humidity
Percentage water vapour to saturize air
RH =AH/MaxH * 100%
Humidity deficit
Deviation between Absolute Humidity
and Maximum Humidity (g/Kg air or g/m3 air)
Vapour Pressure Deficit (leaf-air)
Deficit between Vapour
pressure in plant and
greenhouse air (Kpa)
What is ideal RH or HD? Absolute Humidity: determines dewpoint
Example: AH on your climate computer
Balance : evaporation = export
Source: Peter Geelen Plantmonitoring.NL
Tomato example: AC perforated foil + Energy screen (LS10)
17Source: Peter Geelen Plantmonitoring.NL
Relative Humidity and Humidity Deficit
Source: Peter Geelen Plantmonitoring.NL
Effect of Temperature on humidity values
Source: Peter Geelen Plantmonitoring.NL
Background : humidity control and screening
Greenhouse 20 °C Greenhouse 20 °C
20 °C12 °C
Outside 10 °C
Absolute Humidty in- vs outside Export of humidity
1- By removing it away the micro climate around the plants
○ Maintaining air movement in all local spots where
humidity is being produced
2- By removing it from the Greenhouse air
○ By condensation
● Temperature difference between
air temperature under the screen and glass temperature
○ By ventilation
● Difference of AH in the glasshouse and outside the glasshouse
Working with a Pyrgeo / Irradiation sensor
Prevent: 'cold heads ‘ “goose bumbs”
Incoming vs outgoing radiation on a perfect day
Example Cloudy vs Clear sky
Cloudy sky Clear sky
Example pyrgeo measurement vs plant temperature
Condensation risk in canopy due to irradiation
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Example in Gerbera
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Flower Heart covered
Flower covered
Flower Uncovered
Greenhouse air
Close curtain earlier due to irradiation
Setting example:
How to prevent condensation and lower disease pressure?
○ Priority 1: a uniform climate● Try to have an equal climate everywhere horizontal and vertical
○ Reduce humidity when necessary
1. By condensation on glass/plastic roof
2. By venting or with gap in screen
3. Use fans to bring in outside air
4. By heating with minimum pipe
○ Control fruit temperature
● Heat up at max 1 degree/hour
● Start heating up before sunrise
● Use softsensors to rapidly lower humidity (AH) when needed
Overview of possibilities
○ Source: Presentation Aat Dijkshoorn, KAE , jan 2014
So what’s next?
Source: Presentation Aat Dijkshoorn, KAE, jan 2014
Try to stop using humidity cracks in screens and
Invest in a Measurement box above the screen !
How to start today? Measurement box above the screen.
Greenhouse temperature above curtain
Greenhouse temperature
Outside temperature
RH above curtain
Curtain position
Curtain: deviation above-below curtain
Adapt opening strategy regarding
deviation temperature above-below the screen.
Measurement box above the screen.
Setting example:○ When you just start using physics applied to your
greenhouse humidity controls you have a guaranteed
Return on investment within a day!
○ With small investments you can have a Return on
Investment within a month!
If you have any questions don’t hesitate to ask www.hoogendoorn.nl
Email: [email protected]
Summary