By Lucía García – UCM

During the last decade, city councils have been renovating street lamps, mostly made of sodium vapor, with LEDs with the intention of saving energy.

The main argument that has driven this change has been improving the efficiency of the lamps, however, consumption has increased. Lighting is so cheap that we are generating much more!

Only energy efficiency has been improved while increasing total consumption, which is associated with higher CO2 generation and worsening the environmental impact.

Scientists measure artificial light emissions from the ground in order to study its consequences. Night sky monitoring projects such us TESS photometer network of the Complutense University of Madrid, with almost 300 stations that take measurements every 30 seconds, every night of the year.

Energy could been save while reducing light pollution just by not using energy savings to incorporate more light sources. It is about analyzing not only the efficiency. The power has to be adapted to the use. It is not necessary to use the same lumens in a roundabout, where road safety must prevail, as in a natural park, where animals and plants are affected by the lack of darkness. 

We should keep on mind that on roads, safety is achieved by lighting uniformly, since alternating dark areas with areas of intense light can prevent us from seeing pedestrians or other vehicles well.

Lamps must not blind drivers. Streetlights must illuminate only roads. Aiming light only where it is needed is especially important outdoors, as shining light in other directions is a waste of energy. Light should never be aimed directly upwards, avoiding illuminating the sky.

One way to decrease overall consumption is to reduce usage time by equipping our less traveled streets with presence sensors.

Finally, the appropriate color temperature for each situation must be used. Cold light is more energetic than warm light, so it generates a series of negative consequences that sellers often overlook. White light not only impairs the quality of astronomical observations, but also disrupts the circadian rhythm of living organisms, endangering both human health and that of entire ecosystems.

*This article has been written and translated by one of our collaborators. The original (in Spanish) can be found at: