Abstract
AbstractGreenhouse cladding materials are an important part of greenhouse design. The cladding material controls the light transmission and distribution over the plants within the greenhouse, thereby exerting a major influence on the overall yield. Greenhouse claddings are typically translucent materials offering more diffusive transmission than reflection; however, the reflective properties of the films offer a potential route to increasing the surface albedo of the local environment. We model thermal properties by modeling the films based on their optical transmissions and reflections. We can use this data to estimate their albedo and determine the amount of short wave radiation that will be transmitted/reflected/blocked by the materials and how it can influence the local environment.
Highlights
In recent decades the use of greenhouses for the growth of a variety of plants and crops has become more wide spread as they offer better weather resilience, pest control and improved yield qualities during off season growth periods
The materials used must maximize the transmission of photosynthetically active radiation, but thermal build up in the tunnels is problematic both in terms of welfare of the workforce and because crop yields generally reduce as temperature increase.[3]
In this article we examine the optical transmission and reflection data for several commercial materials/ films that differ in the light transmission, reflection, and diffusivity, as well as examine a film that offers noticeable impact on the near infrared (NIR) wavelengths
Summary
In recent decades the use of greenhouses for the growth of a variety of plants and crops has become more wide spread as they offer better weather resilience, pest control and improved yield qualities during off season growth periods. Doughty et al.[20] simulated how the use of crops with different albedos impacted on the local temperatures of the region Their observations showed that at low latitudes between ±30 there was less impact on the shortwave radiation reflectivity compared to higher latitudes >30. UV–Vis–NIR data were obtained on a Cary 7000 Universal Measurement Spectrophotometer equipped with an internal diffuse reflectance accessory (DRA) attachment This latter attachment was used to obtain Spectra for films normal to the incident light beam over a wavelength range of 200 nm – 2500 nm. The zero baseline measurement was performed by removing the reflectance cap on the DRA and allowing passage of the light beam directly through the integrating sphere section This results in a low level of reflection being detected from inside the sample compartment, in the NIR wavelength region. Samples were examined as is, without any coating, at room temperature under low vacuum conditions (0.45 Torr) at accelerating voltages of 12.5–20 kV
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