Technical Report: The Mathematics of Orbital Solar Reflectors
Technical Report: The Mathematics of Orbital Solar Reflectors I. Executive Summary At the time of their original submission to the FCC for launch approval, Reflect Orbital claimed they would be able to deliver illuminances up to 5x that of a full moon (1.6 lux). A...
Spherical Irradiance and Aerosols
Lighting designers will be familiar with the illuminance of a planar surface, which is measured in lumens per square meter (or foot). The irradiance of a planar surface by a germicidal radiation source is conceptually the same, except that it is measured in watts...
Defining Photosynthetic Photon Efficacy
There has been some discussion online and in presentations recently about the issue of photosynthetic photon flux. The argument goes as follows: Photosynthetically Active Radiation (PAR) is somewhat arbitrarily defined as optical radiation within the spectral range...
Designing an Ultraviolet-C Disinfection System
Recent germicidal light sources include UV-C light-emitting diodes and pulsed xenon discharge lamps, but there is a newcomer on the block that has gained considerable media attention: far-ultraviolet excimer lamps. What does it take to design a UV-C disinfection system using far-UV radiation?
Climate-based Annual Daylight Modelling for Greenhouses with Supplemental Electric Lighting
Recent advances in LED-based luminaire design have enabled greenhouse operators to temporally control both the photon flux density and spectral irradiance incident upon the plant canopy.
Greenhouses and Light Pollution
Supplemental electric lighting for greenhouses may be essential for extending the growing season in northern climates, but it comes with a not-so-hidden cost: environmental light pollution. The consequences of this pollution may range from irate neighbours in rural...
Ultraviolet Disinfection for Consumers
In these unfortunate times, it seems that everyone is looking for ways to help with the COVID-19 crisis. From a lighting designer’s perspective, one solution is obvious: ultraviolet radiation. We have known about the disinfectant properties of ultraviolet radiation...
Circadian Lighting – An Engineer’s Perspective
Ian Ashdown, P. Eng, FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 19/11/14. Whether you call it “circadian lighting,” “biologically effective lighting” or some other name, the principle is the same: the color and intensity of light can be used to...
Light Transmittance through Greenhouse Glazing
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 18/10/01. Look at a greenhouse manufacturer’s product specifications and you will see that the light transmittance of single-pane clear glass is typically 88 to 91 percent....
Far-Red Lighting and the Phytochromes
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published 18/06/04. Most LED grow lights feature blue and red LEDs whose peak wavelengths – approximately 450 nm for blue and 660 nm for red – have been chosen to coincide with the spectral...