ix reducing greenhouse temperature n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
IX. REDUCING GREENHOUSE TEMPERATURE PowerPoint Presentation
Download Presentation
IX. REDUCING GREENHOUSE TEMPERATURE

Loading in 2 Seconds...

play fullscreen
1 / 21

IX. REDUCING GREENHOUSE TEMPERATURE - PowerPoint PPT Presentation


  • 75 Views
  • Uploaded on

IX. REDUCING GREENHOUSE TEMPERATURE. A. temperature regimes range 50-80 deg, stress above 90 deg. Greenhouse effect. B. Temperature in greenhouse determined by:. 1. Solar energy Greenhouse effect: Solar energy- short wave radiation passes through glass

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'IX. REDUCING GREENHOUSE TEMPERATURE' - zarita


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
ix reducing greenhouse temperature
IX. REDUCING GREENHOUSE TEMPERATURE

A. temperature regimes

  • range 50-80 deg, stress above 90 deg
b temperature in greenhouse determined by
B. Temperature in greenhouse determined by:

1. Solar energy

  • Greenhouse effect:
    • Solar energy- short wave radiation passes through glass
    • Thermal radiation- longer waves trapped
  • shading in greenhouse
  • time of year
  • time of day
slide4
2. Exterior ambient temperature

3. Moisture transpired

  • Temperature in empty greenhouse greater than in greenhouse with plants

4. Evaporation of water from soil, walls etc.

c techniques to reduce temperature
C. Techniques to reduce temperature
  • Shading - reduce energy absorbed

a. Shading compound

        • Permanent shade after application
        • Removed Aug – Sept

b. Shade curtain

        • Remove during cloudy weather
2 greenhouse ventilation
2. Greenhouse ventilation

a. Definition

  • movement of outside air through greenhouse

b. Characteristics of ventilation system

1) capacity to reduce temperature

2) uniform temperature

3) automated

4) minimum and maximum ventilation

slide7
c. Time of year
  • Winter ventilation
    • Late fall, winter, early spring:
      • outside air cool
      • Minimum to maximum ventilation usually adequate
  • Summer ventilation
    • Temperature control difficult
      • Shading and ventilation
      • Maximum ventilation
slide8
d. Types of Systems

1) Natural ventilation

  • Establish convection currents
    • Ridge vent and side vents
    • Open area

-40% of floor space

    • Removable side wall
    • Removable roof
slide13
2)Motorized Systems - minimum
  • Mix cold with warm ghs. air
  • Poly tube system with vent
  • Low speed fan with vent
  • One fan or several turned on, with vent

3)Motorized systems – maximum

  • Outside directly into greenhouse
  • Temperature dependent
  • Air flow rate

-3/4 to 1 1/4 air ex. /min

-7-8° rise

slide15
e.Control of Systems

1)Natural ventilation

Manual

Automatic

Thermostat

Computer

2) Motorized ventilation

  • thermostats
  • fan(s) 1 or 2 speed
  • Vents
    • Fully open or closed
    • modulating
slide16
3)End wall ventilation

1) Fans on one end wall

2) Vents on other end wall

3) Fan spacing 25’

4) 1 air exchange/min

slide17
4) Side wall ventilation
  • problem mixing cold air
  • Air exchange rate vs velocity
    • 1 exchange 30’ x 100’

-end wall - 100 ft/min

-side wall - 30 ft/min

  • Fan spacing- max 25 ft