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A man reacts to a shaft of intense sunlight reflected from the glass windows of the new "Walkie Talkie" tower in central London.

A man reacts to a shaft of intense sunlight reflected from the glass windows of the "Walkie Talkie" tower in central London.

Photograph by Leon Neal, AFP/Getty Images

Roff Smith

for National Geographic

Published September 4, 2013

The "Walkie Talkie Building," a name Londoners have given a distinctively shaped skyscraper near Saint Paul's Cathedral, has been in the news this week after reflected sunlight from its mirrored facade melted the side mirrors and panels on a Jaguar XJ parked on a nearby street.

So how on Earth does a skyscraper melt a car?

In a nutshell, it does so by using the same principles a Boy Scout might use to start a fire with a magnifying glass—by concentrating a beam of sunlight on a point.

But at 20 Fenchurch Street, London's hottest new address, instead of a lens being used, it is the concave flank of a 37-story skyscraper covered with 355,000 square feet (33,000 square meters) of highly reflective south-facing glass. It is a coincidence of shapes and materials, say physicists, that is ideally suited to focusing a tremendous amount of solar energy on a small area and generating a lot of heat—enough to melt the plastic coatings on the side mirror of an expensive sports car, fry an egg, blister a bicycle seat, or burn a hole in a doormat, all of which are reported to have occurred in the hot spot beneath the Walkie Talkie.

"This is exactly the same principle that was used to light the Olympic torch last year," said Simon Foster, a physicist at London's Imperial College. "They used a reflective parabolic bowl to focus the sun's rays on a point and lit the torch."

Foster added, "Archimedes supposedly used this bit of physics to set fire to the Roman fleet more than 2,000 years ago. Funnily enough, only two months ago I was demonstrating this very thing to a group of schoolkids, using a cardboard parabola covered with tin foil, and showing them how you could fry eggs with the sun."

 

 A man reacts to a shaft of intense sunlight reflected from the glass windows of the new
Sunlight is reflected off of the "Walkie Talkie" building.

Photograph by Leon Neal, AFP/Getty Images

 

Unintended Consequences of Building Design

What does seem to be new, however, is the idea of building a £200 million ($312 million) skyscraper with highly reflective concave sides.

"Plain flat surfaces produce no focusing, so it is unsurprising that most skyscrapers have stuck to that design," said Chris Shepherd, a physicist at the Institute of Physics in London. "Outward curves, like those on London's Gherkin Building, defocus the rays, but the concave surfaces of the new Walkie Talkie Building will focus the rays and produce the unfortunate consequences that are being reported." (Related: Las Vegas building burns tourists.)

And those are many. The effect lasts about two hours per day, during which heat detectors have measured surface temperatures as high as 199°F (93°C) on a black plastic case and 225°F (107°C) on the seat of a bicycle that had been left in the "hot spot." That's easily enough to warp PVC plastic, which has a melting point of about 212°F (100°C). The air temperatures along the affected part of the street have been estimated at up to 122°F (50°C).

"It was too hot for me to want to stay down there very long," said Foster.

Fortunately for the shops, businesses, motorists, and pedestrians in the area, the skyscraper-induced solar heat wave is likely to last only two to three weeks, by which time the sun will have shifted in the sky and no longer be so focused by the concave facade onto the street below—that is, until the same time next year.

By then, the building's owners hope to have found a cure.

27 comments
Tom Kilpatrick
Tom Kilpatrick

they forgot to mention in this article that the architect had a previous problem with this particular piece of physics, but he didnt learn from his past mistakes...

Lis Lay
Lis Lay

Just put up a bunch of solar panels that follow the path of the sunlight and collect the heat energy?

C ODonnell
C ODonnell

Atlantic City casinos have started boardwalk fires for years.

William Jimenez
William Jimenez

A las mejores mentes se le cuelan "pequeños" detalles.

Luis Danilo Diaz Vecino
Luis Danilo Diaz Vecino

EL APROVECHAMIENTO DE LA LUZ SOLAR SERIA UN FENOMENO MUNDIAL EN SU  IMPLEMENTACION, PERO QUE OCASIONARIA  ¿UN SOBRECALENTAMIENTO MAS ALTO  AL QUE VIVIMOS ACTUALMENTE POR SU MAL MANEJO?

Thomas F.
Thomas F.

Difficult to believe that the architects didn't think in advance of the possible effects...

ZEINEB MESSAOUDI
ZEINEB MESSAOUDI

En hiver ça sera idéal; ça aidera contre les dépressions saisonnières, et réchauffera certains os douloureux!. 

Kevin Scott
Kevin Scott

They should build a bunch of these buildings and make a concentrated solar power plant.

A little unrealistic, but that would be really cool to have the building of a city be used to make a power plant.

Ryan Coxey
Ryan Coxey

Worlds worst neighbor... his house actually melts your car and burns your customers! and there is nothing you can do about it.

Sue Emanovsky
Sue Emanovsky

They should pay attention. They could have stumbled on a way to heat buildings without fossil fuels.

dinkster stuff
dinkster stuff

It should have been pretty easy to find the focal point or just face the building a different direction.

R. Gong
R. Gong

As is known to all, solar energy, such as solar magnetic energy, is in a way harmful to human beings. It can commit accidents and injuries, even some uncomfortable symptoms in human bodies. It should be taken more and more seriouly that the light pollution is impeding our health of life.

George Stiller
George Stiller

Solar energy is a moving entity. As the day progresses that searing beam of light off the Walkie Talkie building will move, possibly interrupting an office or store down the street. All the more reasons to have shades on those dark green or blue eGlass windows that are as transparent as clear glass to brightness and glare problems such as this.

George Stiller
George Stiller

Solar energy is a moving entity. As the day progresses that searing beam of light off the Walkie Talkie building will move, possibly interrupting an office or store down the street. All the more reasons to have shades on those dark green or blue eGlass windows that are as transparent as clear glass to brightness and glare problems such as this.

Vincent Wang
Vincent Wang

the architect might calculate the concave reflection very accurately, and buiders also did their job precisely, but well-done job really "cost" a lot more than delinquency.

Yeo Jian
Yeo Jian

@Lis Lay Solar Panel generate electricity base on the light intensity, ambient temperature and more. Higher temperature doesn't mean more energy can be generated, in fact it will reduce the efficiency of the solar panel because the temperature is above the operation temperature. Different quality of solar panel can sustain better in higher temperature, one example is gallium arsenide, which are used in satellite's solar panel. It is very example to produce, so it is unwise to actually install solar panels there considering such lighting condition wouldn't last long!

Bryony Taylor
Bryony Taylor

@Kevin Scott well that is quite similar to what they do for power plants at the moment with concave mirrors. but have a few solar panels on the from of that building where the hot spot is and that's a decent start :)

Nuna Yobiznis
Nuna Yobiznis

@Kevin Scott They already have those.  It's called a heliostat.  They have a very large scale one in Spain called the Solar Project (or PS10).  Although it's not in the city :)

Ahmad Cerial
Ahmad Cerial

@Kevin Scott your idea may not seem far feteched, any thing is possible, the technology is right there. 

Ahmad Cerial
Ahmad Cerial

@Kevin Scott i study in nanotechnology field, iam a student at CPH university. We recently in our curse made a nanofilm, of conductive, and transpararent nano-material that could one day used to make cheap solar energy-panels, it is organic, we could one day, (let us hope that day comes) paint this thin nano material on our huge skyscrapers, transperant as they are, they could power a whole skyscraper, change city living forever. Powering a skyscrapper would be no problem. Still not graduated from university, but when that day happens, my one goal is to make this happen.

Still improving my english.. 

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