Heliostats happen (updated)

There is obviously interest in heliostats.  While I have been a bit preoccupied with other things, and failed to add much new to my blog, the heliostat pages seem to attract the most readership.  So, here is a bit of an update.

I have now had the opportunity to visit the retail areas of Central Park, since their 'hard opening' some weeks ago.  The heliostat mirrors do not appear to be functional yet, so my initial impressions cannot advance our assessment of what they actually do, or how well they do it.  But some aspects of the design do become easier to understand, and therefore if one is so inclined, open to criticism.

The thing that immediately struck me was that there is a big difference between the architectural renderings of the key spaces, and the sensation of those spaces in real life.  The scale of both outdoor and indoor 'public' space is much less expansive that the renderings suggest.  But in particular, the sectional complexity of the shopping spaces turns out to be rather humble in its impact as you move around what is in reality a very small retail mall.

Even more disappointing is that when the heliostat mirrors are finally tracking a beam to the skylight at the top, it's hardly likely it will make a positive difference to the lighting of the central indoor space.  There is a significant 'diffuser' on the skylight: a glass bottomed pond.  The rippling water varies the transmitted light continuously at a rate far greater than the rate at which daylight normally changes.  Normally, one of the arguments for natural light as opposed to artificial is the psychological value of its variability.  But this arrangement goes far beyond the intrinsic subjective value of natural light as opposed to artificial.

I can't convince myself that this is a rigorous technical lighting decision, because of other issues with the general lighting quality.  So, for instance, on going inside the mall, one realizes that the highlighted portions of the interior will be significantly brighter than the adjacent areas, and to balance the user's adaptation levels, quite large amounts of permanent supplementary artificial lighting is required. That lighting is provided by some designerly chandeliers, which even on a cloudy day struggled to achieve any liveliness.  But wait, there is more.

Once one tunes in to the technical issues of the lighting, one questions the material finishes in a different way.  The distribution and modelling characteristics of daylight are everywhere hugely affected by the internally reflected component.  So it comes as something of a surprise that at Central Park there is a cute faux 'timber look', even down to the dark brown planked floor.  The colour and the material are very low reflectance, and literally suck out the diffuse reflections on which better daylight distribution would depend.  And to make things seem almost laughably inept, there are long walls finished in similar materials, taking up major portions of the places where a competent shopping mall would have had shop windows spilling their own light.
 

Genzyme HQ, Cambridge, Ma

I hate sounding unrelentingly negative.  But these few comments go to the heart of my recurring themes.  First, I have a pet project of encouraging people to actually look at the pretty pictures that accompany the spin doctors' press releases. When you do that, you see what I am describing, even in the official photographs of the opening of this aspirational shopping experience. Second, when you take the trouble to tease apart the principles of technical performance, you can more easily find positive precedents for inspiration.  In this case, for instance, the heliostat and reflective chandelier of the Genzyme HQ building in Cambridge Ma. is a much better technical solution to daylight distribution.

Back to the iconic cantilevered frame of the heliostat.  It is remarkably close in every way to the renderings, yet it too undergoes a strange perceptual shift as one walks into the site.  Closer to the buildings than the usual hero shots illustrate, the cantilevered plane closes up the normal sky view between buildings. It is a very counter-intuitive sense of intimacy, and on balance wasn't a good feeling. Certainly from below, the experience is not exhilarating, though it may well be for those privileged to access it from above.  Some time soon, I will take the trouble to photograph the views that don't yet appear on the internet..  But to be fair, I am waiting for the heliostat to be commissioned.  When that happens, I will top up this post.

Other heliostat links:

A nice little review article on DesignBuild Source by Justin McGar here.

A more recent press release, with the image of the whole heliostat that actually includes the motorised primary reflectors on the roof of the shopping centre building.  Click here for the article.

I dread to think how inconvenient it would be for residents looking down if one or more of the lower mirrors' tracking goes awry.  But that is just my paranoia about depending on moving parts!