Thermodynamic Principles and Operation of Solar Greenhouses

Solar greenhouses function through precise thermal management of solar radiation.  When temperatures rise inside the greenhouse, surfaces emit long-wave infrared radiation.  The glazing materials (glass or plastic film) contain this radiation by blocking its dissipation to the external environment.

Heat Transfer Mechanics:

Primary heat loss occurs via convection through:

    • Air exchange between interior/exterior

    • Thermal conduction through structural gaps

Countermeasures include enhanced sealing and insulation to minimize these losses.

Diurnal Thermal Cycle:

1.Daytime Operation

    ▫ Incident solar radiation exceeds heat loss → Temperature accumulation

    ▫ Excess heat may require active venting for optimal plant conditions

    ▫ Thermal storage systems can capture surplus energy

2.Nighttime Operation

    ▫ Continuous heat emission without solar input → Cooling phase

    ▫ Insulating layers ("thermal quilts") deployed to reduce heat loss

    ▫ Auxiliary heating (coal/gas systems) supplements during low-sun periods

Material Evolution:

While traditional glass structures remain prevalent, modern greenhouses increasingly utilize:

    • Transparent polymers

    • Fiberglass composites

Enabling diversified designs from simple conservatories to advanced agricultural factories.

Agricultural Applications:

Globally deployed in:

    • Vegetable production (plastic tunnel greenhouses)

    • Advanced cultivation facilities

    • Integrated aquaculture systems

All leveraging the fundamental solar greenhouse effect for year-round production.