Comparison of Photometric Quantities and Photon Quantities of Light Sources for Interior Green Wall Illumination


Interior green walls which are vertical greenery systems inside buildings are gaining popularity due to their environmental, economic and social benefits. Different from exterior green facades, interior green walls usually receive natural light in a limited manner, resulting in a relatively low photosynthesis rate, which hinders plant growth. For this reason, a supplementary lighting system is often required for providing the interior green wall with necessary quantity of light. Light is usually quantified as the electromagnetic radiation visible to a human eye. Since most lighting products are developed for human applications, the quantity of light is conventionally expressed in lux, which is a photometric unit based on the luminous sensitivity of the human eye. Plants however have an entirely different response to light from the human eye. For the study of plant growth, light is usually quantified by the number of photons which is highly related to the rate of photosynthesis. To demonstrate whether the lighting system of an interior green wall is appropriately designed for facilitating photosynthesis of the plants, the most reliable way is to evaluate the photosynthetic photon flux (PPF) of the light sources. The higher the PPF value per watt, the more efficient the light source is for plant growth. However, few lamp manufacturers provide this technical information. This paper investigates the relationship between photometric quantities and photon quantities of various light sources that are commonly found being applied for interior green wall illumination with the aid of a calibrated spectrophotocolorimeter.

Author Information
R.T.H. Ng, The Hong Kong Polytechnic University, Hong Kong
H.D. Cheung, The Hong Kong Polytechnic University, Hong Kong
M.Y. Chan, The Hong Kong Polytechnic University, Hong Kong

Paper Information
Conference: ACSEE2015
Stream: Energy: Renewable Energy and Environmental Solutions

This paper is part of the ACSEE2015 Conference Proceedings (View)
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Posted by James Alexander Gordon