Horticulture Science Lesson 43 Controlling the Greenhouse Climate - PowerPoint PPT Presentation

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Horticulture Science Lesson 43 Controlling the Greenhouse Climate

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Title: Horticulture Science Lesson 43 Controlling the Greenhouse Climate


1
Horticulture Science Lesson 43Controlling the
Greenhouse Climate
2
Interest Approach
Ask the students what would happen to greenhouse
plants if there were no greenhouse heating or
cooling systems. Try to lead their thinking to
both excessive heat and extreme cold conditions,
and request the students to clearly state their
thoughts and reasons.
3
Interest Approach
Then have the students develop a list of ways
greenhouses are heated and another list of ways
greenhouses are cooled. Compile class lists on
the chalkboard, whiteboard, or overhead for all
to see. When the students have finished with
their lists, state the objectives of this lesson.
4
Student Learning Objectives
  • Describe methods of heating greenhouse
    structures.
  • Contrast major greenhouse cooling and ventilation
    systems.

5
Student Learning Objectives
  • Discuss how energy curtains are used to maintain
    greenhouse temperatures.
  • Analyze greenhouse climate controls.

6
Terms
  • analog controls
  • computer controls
  • computerized environmental management systems
  • energy curtains
  • environmental controls
  • fan-and-pad cooling system
  • fog system

7
Terms
  • hot water heat system
  • infrared heating system
  • polyethylene tubes
  • short-day curtains
  • steam heating system
  • thermostats
  • unit heaters
  • vents

8
What methods are used to heat greenhouse
structures?
  • The ability to heat greenhouses is important on
    cold, cloudy days and at night.
  • Solar energy on sunny days is often enough to
    keep a greenhouse warm, even in cold weather.
  • There are several different methods used to heat
    greenhouses.

9
What methods are used to heat greenhouse
structures?
  • 1. Hot water heating systems are the trend in
    modern greenhouses.
  • A hot-water heating systems involve heating water
    in a boiler and pumping the hot water through
    pipes located in the greenhouse.
  • The pipes are often placed under the benches.
  • These systems have low maintenance and deliver
    even heat.
  • 2. Steam heat involves boilers that bring water
    to a boil the resulting steam flows through
    pipes in the greenhouse.
  • Steam heat is not as even as hot-water heat.

10
What methods are used to heat greenhouse
structures?
  • 3. Small greenhouses are often heated by unit
    heaters.
  • Unit heaters heat air within the units and then
    blow the air throughout the greenhouse.
  • Polyethylene tubes attached to the units help to
    evenly distribute the airflow.
  • Unit heaters are inexpensive but cost more to
    operate than other systems.
  • Unit heaters are commonly used as backup systems.

11
What methods are used to heat greenhouse
structures?
12
What methods are used to heat greenhouse
structures?
  • 4. Infrared heating systems produce heat energy
    that is absorbed by plants, media, and benches.
  • Infrared heating systems do not heat the air.
  • Since these systems must be placed at the peak of
    the greenhouse, they are best suited for high
    greenhouse structures so the energy can radiate
    throughout the house.

13
What are the major greenhouse cooling and
ventilation systems?
  • To maintain optimal temperatures for plant
    growth, it is important to be able to keep the
    greenhouse cool when outside temperatures are
    warm or when the sun is shining.
  • Sophisticated cooling and ventilation systems
    have been developed for this purpose.

14
What are the major greenhouse cooling and
ventilation systems?
  • The number one cooling system used today is the
    fanandpad cooling system, which is based on
    evaporation of water.
  • Cellulose or aspen pads at one end of the house
    are kept wet, while fans at the other end of the
    house pull outside air through the pads.
  • Air entering the house is cooled as water in the
    pads evaporates.

15
What are the major greenhouse cooling and
ventilation systems?
  • A less common cooling system is the fog system.
  • Fog systems involve an atomizer that produces
    water vapor.
  • The flash evaporation of this water cools the
    greenhouse.

16
What are the major greenhouse cooling and
ventilation systems?
  • Natural cooling is made possible with vents,
    which consist of panels that open and allow air
    exchange with the outside.

17
How are energy curtains used to maintain
greenhouse temperatures?
  • The use of energy curtains in modern greenhouses
    helps to maintain temperatures and reduce heating
    and cooling costs.
  • Energy curtains are automated systems using
    fabrics that can insulate a greenhouse at night
    and shade the crops during the day.
  • The curtains are installed from gutter to gutter,
    and they are opened and closed by computerized
    systems.

18
How are energy curtains used to maintain
greenhouse temperatures?
19
How are energy curtains used to maintain
greenhouse temperatures?
  • Short-day curtains are similar to energy
    curtains.
  • The function of shortday curtains is to provide
    darkness that will simulate a short-day effect.

20
What are the common greenhouse climate controls?
  • Climate controls give the grower the power to
    control temperatures within the greenhouse.
  • Environmental controls are devices used to turn
    greenhouse systems on and off, including heating
    and cooling systems.
  • Thermostats are low cost and easy to install
    environmental controls.
  • 1. On-off thermostats control fans, heaters, and
    vents with the change of temperatures.
  • 2. Proportioning thermostats provide continuous
    control of systems with the change of temperature.

21
What are the common greenhouse climate controls?
  • Analog controls use proportioning thermostats to
    run amplifiers and electronic circuitry.
  • The heating and cooling operations are
    integrated, resulting in better performance than
    provided by just a thermostat.
  • Computer controls use microprocessors to make
    complex judgments based on information from a
    number of sensors.
  • Computerized environmental management systems,
    although expensive, are accurate and can control
    all the automated systems together.

22
Review/Summary
  • What methods are used to heat greenhouse
    structures?
  • What are the major greenhouse cooling and
    ventilation systems?

23
Review/Summary
  • How are energy curtains used to maintain
    greenhouse
  • temperatures?
  • What are the common greenhouse climate controls?
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