Cooling and Ventilation

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Presentation transcript:

Cooling and Ventilation Unit: The Physical Greenhouse

I. Air Circulation Definition - movement of air within greenhouse

Circulation Importance Uniform air movement Prevent temperature layering

3. better air exchange around plant CO2 H2O 3. better air exchange around plant a. replace CO2 depleted air b. remove high humidity c. reduce temperature of leaf surfaces

Problems Uniform air movement Moving air through plants

Two Circulation Systems Horizontal Air Flow (HAF) Fans placed around the greenhouse The better of the two systems

Circulation: HAF HAF

HAF Placement

Polytube System Located near the peak of the greenhouse Fan located at the end of the greenhouse Long plastic tube with holes in it runs the length of the greenhouse

Polytube Circulation

Polytube and Heating

Polytube – Fresh Air

Reducing Temperature Shading – reduce absorbed energy Accomplished with shade/energy curtains

Reducing Temperature Ventilation Movement of outside air through the greenhouse

Types of Ventilation Natural Ventilation Uses convection currents Ridge vent and side vents Open area Removable side wall Removable roof

Natural Ventilation

Natural Ventilation

Natural Ventilation

Natural Ventilation

Types of Ventilation Motarized Ventilation Minimum – polytube system Mixes warm greenhouse air with cool outside air Maximum Outside air replaces greenhouse air

Maximum Ventilation End Wall Ventilation Side Wall Ventilation Fan located on one end of the greenhouse Vent located on the other end Side Wall Ventilation Fans and vents located on sides

Reducing Temperature Cooling Reducing temperature of the air entering the greenhouse

Cooling Systems Refrigeration Evaporative Cooling Pad and fan High pressure mist/fog

Evaporative Cooling Why does it work? H20(liquid) + Energy(warm air)  H20(gas) + cooler air

Evaporative Cooling Factors determining cooling Temperature: outside air Relative humidity: outside air Temperature: inside air

Evaporative Cooling Factors Determining Cooling air movement shading structure Covering

Pad and Fan System Works with the existing end wall or sidewall ventilation Pad covers the vented area

Pad and Fan System Water is poured through the pad when the system turns on The fans for the circulation system turn on and pull outside air through the pad

Pad and Fan Systems Points to Consider Need to eliminate leaks through pads around pads other areas

Need uniform wetting holes clogged Detergent Algae growth CuSO4 The closer to the pad, the cooler the temperature

High Pressure Mist - Fog A pump, pumps out small droplets of water into the air Creates a fog in the greenhouse Problems Salt deposits Poor air movement

Fog evaporative cooling