Wide-range spectral measurement of radiative properties of commercial greenhouse covering plastics and their impacts into the energy management in a greenhouse

Controlling a greenhouse microclimate requires energy consumption for heating and cooling the greenhouse inside air. The radiative heat transfer process inside a greenhouse depends on the spectral radiative properties of different components especially on the greenhouse covering material. There is a lack of information about the precise spectral radiative properties of the available commercial plastic sheets used as greenhouse covers. In this research, the spectral radiative properties of several commercial greenhouse covers are measured in a wide wavelength range from 0.2 to 28 μm. The measured properties are then used in a developed model to simulate the indoor climate of a greenhouse. In the developed model, the covering material is treated as a semi-transparent medium, the soil surface is considered as partially reflective surface, and the inside air is assumed as an absorbing-emitting medium. Finally, under a specific hourly climate conditions, the impacts of using different commercial covers on heating and cooling load demands are investigated. The measured total solar transmittance was 70.3–92.1% and the long wave transmittance was 18.1–61.8% for selected samples. The results indicated that using the appropriate covering plastic reduced the annual cooling load by 9.8% and heating load by 6.3%.