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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..
4
3
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$.
9
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
○
Example in Gerbera
○
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