[RD (OP)]

http://www.dailymail.co.uk/news/article-2407002/Londons-Walkie-Talkie-skyscraper-forces-passers-shield-eyes-blinding-light-reflected-windows.html

http://www.dailymail.co.uk/news/article-2409073/Walkie-Talkie-melted-Jag-Londons-Fenchurch-Street-skyscraper-melts-businessmans-car.html

[CliffordK]

Apparently the archetects in London hadn't heard of the Vdara Death Ray. 

The Vdara Hotel was opened in 2009, although, perhaps the problems of the Death Ray wasn't noted until the summer of 2010. 

However, the Walkie Talkie Building was in the early stages of construction in 2009 and 2010.  It is inexcusable that the construction wasn't re-evaluated in light of the Las Vegas fiasco.  I'd hate to see a major redesign after the core was laid in 2012, but it still would have been better than waiting until they start blasting people's cars, or perhaps offices across the street.

It appears as if the Vdara building used a simple linear curved mirror shape, while the Walkie Talkie building design has a true single point parabolic mirror design to give a much tighter focus to its "death ray". 

Had they designed a concave face to the North, and convex faces to the other directions, there would not have been an issue.

[RD (OP)]

Apparently the archetects in London hadn't heard of the Vdara Death Ray.

It's the same architect for both buildings (!) ...

Employees have called the phenomenon the "Vdara death ray" ... The architect, Rafael Viñoly, also designed the "Walkie-Talkie" skyscraper which has been dubbed the "Walkie-Scorchie" due to a similar problem.

https://en.wikipedia.org/wiki/Vdara#Solar_convergence_or_.22death_ray.22

Ania Gzik, an insurance worker, said she couldn't believe how hot the spot became when the light was reflected and plans to warm up there when winter comes

http://www.dailymail.co.uk/news/article-2407002/Londons-Walkie-Talkie-skyscraper-forces-passers-shield-eyes-blinding-light-reflected-windows.html

When winter comes the track of the hot-spot will  follow a different path.

[David Cooper]

It should be renamed the Solar Cooker.

The problem won't go away in winter - it'll start cooking the rooms on the first floor later in the year, and then the second floor, etc., so they'll have to put up a huge screen of something that won't burn. Frosted glass would stop the burning problem entirely, but you'd get no view through the windows, so realigning all the windows to make them all parallel to each other looks like the only sane option.

[CliffordK]

I suppose the question is how bad the effect is.  In some senses, it sounds like it is nice to have a little artificial sunlight in the perpetual shade down on the street. 

Nonetheless, there are negative effects of it.  being flashed with a very bright light when driving can cause a momentary decrease in visual acuity.  And, as they've discovered damage to vehicles (what about harming kids or pets in the vehicles)?  I suppose London has such a surplus of street parking that it is fine to eliminate a few parking spots.  A traffic jam might even be uncomfortable for a person without AC.

As the sun drops, the spot will rise into the adjoining office buildings.  In a sense it is nice to have some sunlight, but it makes computer screens hard to read, and can be distracting.  Why should the neighbors have to install sunshades and block their own view because of a neighbor?

Since it is the same architect/architectural firm that designed the building in Nevada, undoubtedly they should have been aware of the potential issues at least during the early construction phase in London, and should have had a meeting with property owners, developers, city officials, & neighbors at that time. 

If this proves to be a significant issue, no doubt there will be a lot of people pointing fingers, and I have no doubt there could be lawsuits and people loosing their jobs.

Thankfully they are wanting to house insurance companies in the car cooker.

[Bored chemist]

They have done this sort of thing before
http://www.nottinghamplayhouse.co.uk/about-us/sky-mirror/

[RD (OP)]

They have done this sort of thing before
http://www.nottinghamplayhouse.co.uk/about-us/sky-mirror/

It's artwork and pigeon pest-control combined  [] ...

A £900,000 mirror sculpture destined for a square in Nottingham, UK, will have to be shielded to prevent it focusing the Sun's rays and barbecuing passing birds.

http://www.newscientist.com/article/dn495-barbecue-wings

[CliffordK]

Contrary to media speculation Sky Mirror does not pose any danger to the
public or pigeons in the form of a barbecue ray.

A £900,000 mirror sculpture destined for a square in Nottingham, UK, will have to be shielded to prevent it focusing the Sun's rays and barbecuing passing birds.

Hmmm, it sounds like the two sources need a bit of collaboration.

£900,000 for an 18 foot piece of stainless steel?
I am definitely in the WRONG business.

It is big though. 

I wonder where the focal point for the walkie talkie building is, and how tight of a focal point it actually produces.  If it actually produces something like a 2 square meter focal point (the size of a window), then the heat and potential for damage could be high.  And, it may not show up until sometime later in the year, and if in the winter, perhaps not for a couple of years.  The articles I'm seeing indicate that the problem is only of short duration, but it is unclear if that is only short duration at ground level.  The tighter focal area may only be achieved at roof level.

This article claims being able to fry an egg in the hot spot, as well as a fire being started by the tower.

We'll see if the excitement settles down over time, and becomes just a passing novelty, but I can foresee an expensive remediation.  Perhaps adding horizontal louvers to the outside of every window pane (imagine a million pigeon roosts).

I would charge the architectural firm nearly 100% liability for the remediation (even consider tearing down the building), as they had prior experience with curved reflective window surfaces, and yet apparently did nothing.  Of course, in the modern world, that means they carry no liability, and the insurance company foots the bill.

[alancalverd]

Not sure how big the offending building is, but a crude parabola say 100 m high by 50 m wide will receive around 1 MW solar input at lunchtime. If you reflect 75% of that into a 1 square meter focus (not difficult, using ordinary builders' and glaziers' equipment to align and construct the building) you could easily barbecue a car.   

[evan_au]

Anish Kapoor's Sky Mirror sculpture was also on display at the Museum of Contemporary Art in Sydney.
As the morning sun rose over the Opera House, it scorched a browned path through the lawn - despite a sprinkler hose spraying cooling water around it.
And rather than knocking birds out of the sky, the seagulls actually seemed to enjoy it...

[evan_au]

Museum of Contemporary Art, in Sydney

[alancalverd]

My mother was intrigued by a line of tiny holes that appeared in her curtains. Turned out to be burn marks from the sun shining through her collection of glass paperweights. This is the principle of the traditional sunshine recorder and the Civil Defence nuclear burst triangulator.

So art is at last imitating science.
 

[CliffordK]

How much of light is reflected by a single pane of glass?  I'm sure there are many factors including whether it has a privacy coating. 

If the building has about 30 panes x 30 panes, that gives about 900 panes of glass.  If they would all be focused on a single focal point, that would be 900 suns x the reflectivity. 

The amount of sunlight reflected may depend on the angle.  With a very clear window glass, it may only be a couple of percent.  With a mirrored glass, perhaps up to 50% or more.

One may be able to just change either the vertical or the horizontal angles of the windows to break up the reflection, and limit the multipliers.. 

Another solution to the problem might be to get as clear as possible of windows for the building.to limit the amount of sunlight reflected by each pane.

[CliffordK]

My mother was intrigued by a line of tiny holes that appeared in her curtains. Turned out to be burn marks from the sun shining through her collection of glass paperweight

Hopefully she moved the paper weights.  Tiny holes may be annoying.  A fire would be a tragedy.

[RD (OP)]

... Turned out to be burn marks from the sun shining through her collection of glass paperweights.

Fishbowls too ...

[Bored chemist]

How much of light is reflected by a single pane of glass?  I'm sure there are many factors including whether it has a privacy coating. 

If the building has about 30 panes x 30 panes, that gives about 900 panes of glass.  If they would all be focused on a single focal point, that would be 900 suns x the reflectivity. 

The amount of sunlight reflected may depend on the angle.  With a very clear window glass, it may only be a couple of percent.  With a mirrored glass, perhaps up to 50% or more.

One may be able to just change either the vertical or the horizontal angles of the windows to break up the reflection, and limit the multipliers.. 

Another solution to the problem might be to get as clear as possible of windows for the building.to limit the amount of sunlight reflected by each pane.

About 4% is typically reflected
http://en.wikipedia.org/wiki/Fresnel_equations
But that's for visible light. Some windows have a coating that deliberately reflects near 100% of the  infra red so you could end up with 100s of KW pe square metre.
The real solution isn't to try to reduce the reflectivity of the glass (which isn't possible over a really wide bandwidth) but to educate designers and architects so they don't do stupid things.
Ripple surfaced glass would pretty much solve the problem, but that would rather spoil the view from inside the building.

[evan_au]

A small tweak on the 4% visible-light answer from BC: A similar amount of light is reflected from the far side of the pane of glass (ie the glass-to-air transition), so the total reflection from a pane of non-coated glass is closer to 8%.
It may be even higher for double-glazed windows.
But I agree that most of the energy of sunlight is in the Infra-Red part of the spectrum.

[CliffordK]

Only one Tacoma Narrows Bridge collapsed.  The second one is still standing today, and the engineers around the world seemed to have learned the lesson.

Architect Rafael Viñoly designed two curved buildings with similar solar reflection issues.

He is now claiming that it isn't his fault, and is blaming everyone else.  They were built back to back, but once the Nevada issues were realized, the Walkie Talkie building was in early enough stages of construction that it could have been fixed.

Apparently it is a tourist attraction.  But, I have to wonder how soon until it will get old for businesses across the street to have scaffolding and sunshades erected to prevent them from overheating as well as loosing parking.  And, the hot spot will rise above street level shortly, but blasting into the buildings may not be pleasant either.

A building should be a "good neighbor".  One option is to require 100% remediation of the problem.

Lowering the reflection of the glass?  What about flat black paint?

They could still tear off and rebuild the entire facade.

Blaming the problem on Global Warming?  Hmmm....

[RD (OP)]

What about bowed (curved) glass windows ? ...

 [ Invalid Attachment ]
http://www.trendir.com/archives/001608.html

Cost an arm and a leg though.

[Bored chemist]

convex windows are less of a problem for two reasons, they would only focus light from a source inside the room- and the sun is outside. Also, they would focus it to a line, not a point.


" engineers around the world seemed to have learned the lesson."
Not entirely
http://en.wikipedia.org/wiki/Wobbly_bridge#Resonance