It is a little more complex. There is a distance from the (presumed
flat) mirror such that the angular extent of the mirror is about the
same as that of the sun (1/2 deg). From there out the intercepted flux
decreases, by the square of the distance.
From the birds view, at that distance it sees the whole sun fill the
mirror. Any farther out the image is bigger than the mirror -only part
of the sun is supplying heat.
If the mirrors are curved, then each mirror will have a hot focal point,
but not super hot: again it is limited by the angular extent of the sun
and the mirror. A ideal mirror will project an image of the sun on the
boiler (or bird, if at focus), and the intensity is that of sunlight
multiplied by the square of the ratio of the two angular extents. Maybe
10 or 20 to 1? WAG here.
As Bob points out, the "nimbus" effect strongly suggests that the
designers were aware of a possible problem and made sure mirrors in
standby don't all point at a single point, or even parallel.
Ol' Bab, who was an engineer.
On 4/10/2014 11:06 AM, Bob Cook wrote:
The mirrors would not be focused at one spot when idle. Also it is a
good idea to reduce global warming by directing the light back into
space instead into the ground.
----- Original Message -----
*From:* Jed Rothwell <mailto:jedrothw...@gmail.com>
*To:* vortex-l@eskimo.com <mailto:vortex-l@eskimo.com>
*Sent:* Thursday, April 10, 2014 7:59 AM
*Subject:* Re: [Vo]:Problem with glare at Ivanpah CSP plant
ChemE Stewart <cheme...@gmail.com <mailto:cheme...@gmail.com>> wrote:
Efficiency/85% heat transfer efficiency @ solar boiler/90%
mirror efficiency = 1700 megawatts airborne flux, THAT IS A
GOOD BIRD ZAPPER
Close to the tower it would be. When a bird flies a few meters
away from the surface of one mirror, it is no different than
flying in full sunlight or in sunlight reflected from glass or water.
I do not know at what distance from the tower the beams of light
join together to be brighter and hotter than ordinary sunlight.
I expect birds would not approach the tower because it is so bright.
Millions of birds are killed by smoke from coal plants, and steam
from coal, gas and nuke plants.
- Jed
