Title: Horticulture Science Lesson 43 Controlling the Greenhouse Climate
1Horticulture Science Lesson 43Controlling the
Greenhouse Climate
2Interest 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.
3Interest 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.
4Student Learning Objectives
- Describe methods of heating greenhouse
structures. - Contrast major greenhouse cooling and ventilation
systems.
5Student Learning Objectives
- Discuss how energy curtains are used to maintain
greenhouse temperatures. - Analyze greenhouse climate controls.
6Terms
- analog controls
- computer controls
- computerized environmental management systems
- energy curtains
- environmental controls
- fan-and-pad cooling system
- fog system
7Terms
- hot water heat system
- infrared heating system
- polyethylene tubes
- short-day curtains
- steam heating system
- thermostats
- unit heaters
- vents
8What 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.
9What 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.
10What 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.
11What methods are used to heat greenhouse
structures?
12What 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.
13What 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.
14What 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.
15What 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.
16What 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.
17How 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.
18How are energy curtains used to maintain
greenhouse temperatures?
19How 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.
20What 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.
21What 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.
22Review/Summary
- What methods are used to heat greenhouse
structures? - What are the major greenhouse cooling and
ventilation systems?
23Review/Summary
- How are energy curtains used to maintain
greenhouse - temperatures?
- What are the common greenhouse climate controls?