Lighting for Being.
External lighting design practices for conserving our night sky.
by Mitch Harrison, Electrical Engineer.
Since the ages of antiquity, our ancestors have used the stars to shape our understanding of the cosmos. We’ve traced out the images of gods, navigated unknown seas in the search of new horizons and peered into the origins of the universe using these ancient beacons suspended in the night sky. For millennia, these celestial bodies have been the fire of human wonder. This obsessive inquiry has been a critical driver in the evolution our civilisation. We have taken command of natural phenomena that we find ourselves surrounded by, manifesting all sorts of magical creations. One could arguably point to the stars themselves as being the inspiration behind the seemingly humble streetlight.
Our external lighting landscape has seen a rapid shift over the past decade to remarkably efficient LED (light emitting diode) technology. Greater efficiency and decreasing production costs have brought the cost of lighting within the reach of a much wider community.
The equivalent cost of lighting today is a mere three thousandth of the cost of lighting in the eighteenth century.
With the reduction in the cost of illumination, we are seeing the illumination of more external spaces. This encourages better utilisation of external spaces and assists in fostering a better sense of community after dark. Well-lit external environments not only satiate our desire for nocturnal exploration, but contribute to a safer community through the deterrence of crime.
It’s certainly clear for our wellbeing and security that we should embrace external lighting. However, we must take careful steps to preserve the stellar display over our heads that contributes to our night time experience. A paper published in November 2017 examined the artificially lit surface of the earth from space. The paper concluded that there has been a steady growth in the radiance of artificial light from the earth’s surface (increasing by 1.8% per year from 2012 to 2016).
Artificially lit surface of Earth at night increasing in radiance and extent. Read the full article
The Bortle Scale – used to quantify light pollution – puts Australian cities and suburbs at a level of 7 out of 9 (with 9 being the worst case). Anyone who lives in an urban area will know first-hand the effects that this light pollution has on viewing the stars.
Surprisingly, the study also suggest that even with the leaps and bounds that LED lighting has made in the way of energy efficiency, external lighting systems overall are still consume as much energy as with older technologies. This is likely due to more affordable lighting and increase in GDP (Gross Domestic Product) of developing countries driving the purchase and installation of more lighting.
Fortunately, there are a number of design tools we can use to help us reduce the risk of both light pollution and excess energy consumption. Through careful consideration of light selection, thoughtful design and adherence to relevant standards and guidelines we are able to achieve beautiful lighting designs that are considerate to our night skies.
Light Pollution Map showing New South Wales & Victoria.
Image credit to Jurij Stare, www.lightpollutionmap.info
Common Lighting Fixtures
The most critical aspect of external lighting design that can be deployed to address the concerns of uncontrolled light spill is selection of quality light fittings. While it may be tempting to select lighting on a unit cost basis, more “affordable” fittings tend to produce uncontrolled light spill. Lights fittings that are designed such that the light source within the fitting is shielded provided the greatest control of obtrusive lighting. Selection of unshielded fittings not only results in uncontrolled light spill, but becomes a source of glare in the external space. Similarly to having a torch shine directly at you, large glare sources dramatically reduce how well we are able to see in low lit external environments.
Control of Light Distribution
Current LED optical technologies allow us to design more visually comfortable external lighting installations. Through the use of a variety of optics, we are able to bend and stretch light to our whim. Optical control ensure that light goes exactly where it is needed, eliminating the harmful obtrusive lighting effects that are characteristic of more “economic” external lighting systems.
Careful selection of optical control can also mean less light fittings are required for a given space to achieve the same results, meaning less capital and operational expenditure for more visually pleasing results. A 2015 study by the Lighting Research Centre in New York illustrates how the perception of brightness in an external carpark is more closely related to the uniformity of light distribution than the overall average illuminance of the carpark.
Standards and Guidelines
As engineers, we have at our disposal a number of standards and guidelines to remove the potential for uncontrolled light spill in our external environments. AS4282 – The Control of the Obtrusive Effects of Outdoor Lighting (AS4282) is the primary standard addressing selection, installation and design principles for external lighting systems in Australia.
In addition, organisations such as the Green Building Council Australia (GBCA) recognises lighting designs that limit the uncontrolled emitting of upward light in the Green Star rating system.
There are also a number of organisations that provide resources for lighting designers, developers and the general public who wish to minimise their light pollution. The International Dark Sky Association (IDA) have developed with a number of lighting suppliers a “seal of approval” program for dark sky friendly light fittings.
Programs such as the IDA seal of approval program help designers and end-users make conscious choices in reducing the environmental impacts of our externally lit environments.
So what’s next?
With external LED lighting becoming increasingly more affordable, we are likely to see more external lighting installations to encourage the utilisation of our parks and precincts in a secure manner. To preserve our night skies and minimise the impact of these installations on wildlife it is vital that we approach external lighting design thoughtfully. Through careful design practices and adherence to standards and guidelines available both nationally and internationally, we will be able to marvel at the brilliance of the night sky for many years to come.
