NightTec, a German company dedicated to the latest advancements in “light recycling,” offers a wide array of useful glow-in-the-dark products for general consumers and businesses alike: Construction helmets, dog leashes, lampshades, wall paint, and fasionable rave accoutrement.

And then there's NightTec Leuchsteine paving stones. As part of the "Eco-Green" product series developed in partnership with manufactuerr Kann, the company is keen on highlighting the energy-saving potential of phosphorescent crystal-embedded concrete pavers that appear white during the daylight hours and emit a subtle blue or green glow for as long as 10 hours once the sun goes down (or the lights go out).

As reported by EcoBuilding Pulse, NightTec believes the glow-in-the-dark technology has the potential to save a staggering 212 million megawatt-hours of electricity annually based on the estimate of future building renovations in Germany "that require illuminating materials.” That's pretty dramatic. At the very least, NightTec's somewhat eerie glowing concrete stones take the trip-and-fall-related danger out of after-hours landscaping projects.

So how exactly does this solar cell-free, afterglow-based technology work?

All NighTec® products are storing light when exposed to natural or artificial light. After this charging phase the stored light is re-emitted when the NighTec® material is exposed to darkness. This way the old light was recycled into new light and new light was emitted.
And, as mentioned, it's all about the phosphorescence:
The effect of afterglow lighting is that of phosphorescence.' This is often is confused with 'fluorescence.' This term was named based on the element of 'phosphorous,' which has a natural afterglow observed by the alchemists in the 17th century and so named. The element phosphorous is not used in phosphorescence nowadays. With phosphorescence, the luminescent materials charge themselves in UV- or black light and then illuminate in the dark. In public this effect is often called 'glow in the dark.' Our luminescent materials do not contain any phosphorous either.
More in the costumer-filmed video below (the voice-over is in German but the product shots need no translation).

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

'Light recycling' pavers save energy, prevent stumbling around in the dark
NightTec Leuchsteine concrete paving stones from Germany start to glow once the sun goes down.