Sunday, 21 April 2013

The sky isn't falling, but I'm clueless

















Just a quick update: the penthouse apartments in Jean Nouvel's apartment block, known as Central Park 1 in Sydney, have gone on sale this weekend, offered to buyers locally and marketed also in our increasingly affluent and outward looking Asian region.

But I am not a real estate agent, my interest continues to be the question of just what exactly will the much-vaunted heliostat do?  The image above is from the advertisement, and is just a bigger version of the same rendering I used in my previous post about the subject.

Up till very recently, try as I might, I couldn't find a single reference on-line or otherwise accessible to the average punter, that answers my original question: just how does the winter sun in the middle of the day actually get to the bits of the cantilevered frame, which then are supposed to reflect it down the shaded southern facade (remember, this is the southern hemisphere)?

That changed, slightly, when the company contracted to do the feasibility study and construct the heliostat, local firm Kennovations, released a single page promo/case study.  You still have to be a detective to even begin to figure out what is actually proposed.  Let me try to help, while we all wait with bated breath for the chance to see it in action.

Image: Kennovations
The image at the left is clearly from a 3D analysis of ray-traced reflections.  Not labeled for date or time of day, it doesn't by itself demonstrate a lot, except that such modelling has actually been done.  I wouldn't expect otherwise.

It turns out the consultants are Device Logic, who otherwise specialise in design, installation and commissioning of tracking systems for utility scale solar power plants.

Clue 1:  The rays shown, both directly from the sun, and arriving via the cantilevered frame, are directed at the rooftops of the podium, and of the 'West Building', not at the south face of the taller 'East Building'.

Clue 2:  All along, had we read it carefully, the description of project had said:
"The heliostat incorporates an innovative system of fixed and motorized mirrored panels designed to capture sunlight and redirect it into the retail atrium and onto the landscaped terraces."  

Why did we jump to the conclusion that it was supposed to be a Clayton's solar access in winter for the south facing apartments?

Because every other residential building approved in Sydney has to try to arrange such solar access to 70% of all apartments, under the local model code which gives effect to a State Environmental Planning Policy known as SEPP65.  My consultancy practice is almost entirely devoted to helping architects go through the gymnastics of achieving that compliance.

Now that you are in that frame of mind, you probably look at the renderings slightly differently.  I can't help wondering what the occupants of  the apartments on several floors under the cantilever will think of looking into its underside, and losing the light from the sky?  But look more carefully.

Image: Kennovations
Clue 3:  The cantilevered frame shown in the other images is protruding much more from the facade than the one in the top picture.  I wouldn't immediately jump to the conclusion that the 3D renders are cheating.  Mind you, it's either that, or the frame is motorised to protrude further at key times.  If the latter, I definitely wouldn't like to live under it.

Clue 4:  Now look more carefully at the technical description finally available in the Kennovations pamphlet.  It says:
"Kennovations is contracted to Watpac to Design and Construct  the 42 x 6.2sqm Sun Tracking Heliostats (on the rooftop), the 320 x 1.5sqm Reflector Panels (suspended beneath the main cantilever)."
Hold it!  What does that say? 42 big 6.2sqm heliostats on what rooftop?  Is that what those things are on the West Building roof?  If so, what are they lighting?  If not, why has noone mentioned them before?  Unfortunately, I have no clue that helps me out with answering those questions.

Image: Kennovations
So, now that you are thoroughly confused, but like me, keen to keep going with this game of Cluedo, try this one.

Clue 5:  Thenext image also comes from Kennovations.  It looks like a full scale mock-up of the reflectors.  Is it?  If so, where is it?  I'd love to see it.  Because looking at it, I am even more mystified how the heliostat will work.

In desperation, let's try my favourite trick of analysis.  I call it 'semantic opposites'.  In other words, if something just doesn't want to make sense, look at it the other way around.

Clue 6:  What if the things on top of the 'West Building' are reflectors pointing upwards? Watch architect Bertram Beissel wave his hands around about half-way through this video, produced by the Sydney Morning Herald on-line, then finally, you may find on the Kennovations Portfolio Projects page this well hidden linked graphic different from any previously available.

Now I only get anxious about looking down from my apartment onto an array of mirrors reflecting an optical image of the sun upwards.

I think I am getting close to solving the mystery.  But I think it might be best if I have the patience to  answer all those questions by seeing the real thing - relatively soon, if it's true that the new owners of the penthouses are  able to move in come June 2013.  Keep the fingers crossed that it hasn't all been a monumental con-trick.

For the clues, read:
Kennovations One Central Park Heliostats and Reflectors Case Study here.
Gizmag Cantilevered residential heliostat takes shape in Sydney linked here.

For anyone really interested, there are further technical snippets to be found here. The links include a short amateurish video of wind tunnel testing at CPP's huge boundary layer wind tunnel at St. Peters, Sydney.

EDIT:
Jeremiasz Sieczko has posted an excellent reworking of this attempt to unravel the mystery of the heliostat geometry.  It was too long for a comment, so I have posted it as an independent article length post at Clued in on the heliostat.

 

 

2 comments:

Anselm Jed Liu said...

In Central Park 1, architects proposed to bring daylight into the south by using heliostats and reflectors, which haven't been used before in architecture. But does it really work?
The system of heliostats and reflectors in Central Park 1 is somewhat similar to that in the concentrating solar power. They both work by tracking sunlight on treated mirror and redirecting it into another direction. However, they are not the same system in that the concentrating solar power system collects the concentrated temperatures by focusing the heat onto a small plate to generate electricity, whereas in Central Park 1, the 'light redirecting system' merely redirects ordinary sunlight to the reflector. Even though they are different in this way, both systems share a high reliance on motorised light catching reflectors. As a result, in the sense of light catching and reflecting, the system sounds viable.
Nevertheless, the viability of the Central Park 1 system should be examined in another way. The site of Central Park 1 is next to UTS, which is among tall buildings. Will the heliostats be able to gain enough sun light easily for redirection? If not, is it wasting money to install those innovative materials in this apartments? In the rendering images, it doesn't show the tall building next to the heliostats. So will the tall building affect sunlight catching for reflection? Definitely yes! If there is no reflected daylight, chances are that the apartment on the south will be shaded off daylight by the cantilever on the top. In fact, whether it is rewardable to make it cantilever and to put on such innovative materials is still questionable.
Moreover, since the system of reflector-heliostat is based on daylight(direct/diffusive), without special treatment, the mirror image in this story would be the light source itself, no matter it is the 'luminous' sky or even worse, the sun. In other words, looking into those reflectors and heliostats is approximately the same as looking directly into the sky, which is unpleasant and potentially harmful to one's eyes.
Another issue that the system gives rise to is the maintenance of the cantilevered reflectors. Raining season with hailstorms in Sydney is a tough for these reflectors. According to the Heliostat Reflector report done by Google, glass reflector can resist up to 25mm large hailstones, which is marble-sized. If the hail kinetic energy increases by 9 times, the exposed reflectors might crack. Therefore, it is critical to strengthen the reflector itself and to provide a good maintenance to prevent further accidents.
Reference:
http://www.redrok.com/concept.htm http://www.google.org/pdfs/google_heliostat_reflector_design.pdf http://designbuildsource.com.au/capturing-the-sun-integrating-heliostats-into-buildings

Joshua Angsono said...

While i have to admit that the rendering looks amazing, and the idea of using a heliostat to get the sun into the apartments and to the park are quite out of the box, I find myself questioning the practicality and the effectiveness of the heliostat.

From your article, we know that heliostat follows two steps, first it reflected the sunlight from the west building to the second heliostat at the rooftop. Then, it got reflected again to the building and to the park. I find this to be very interesting and would love to see how it works out, because most of the heliostat that i’ve seen such as the Power Plant in Seville Spain uses only one (but big) heliostat. But this also means that the heliostat depends on each other to work.

The maintenance of the heliostat is also an issue that we should be thinking about. Since heliostats are essentially mirrors, would it need a lot of maintenance to keep it clean and working effectively throughout the year? And what about the maintenance for motorised panel, to get the most from the sun, i assumed there would be a lot of motorised panel, especially on the first heliostat.

From the pictures I looked at, I assumed that the reflected sun from the heliostat is very directional. That means the amount of sunlight that hits the park and apartment are only as much as the amount of mirror from the second heliostat, which is not a lot considering the amount of area it’s supposed to light up.

And from the pictures that i’ve seen (attached below), the effects of the light from the heliostat are quite strong but only to the dimension of the mirror of the heliostat. So I am wondering how the effect of the light will affect the park.



Reflected Light from the heliostat
Image:
http://assets.inhabitat.com/wp-content/blogs.dir/1/files/2012/03/house_reflection-e1330627363733.jpg
http://www.iwilltry.org/b/wp-content/uploads/2007/07/heliostat_7_office_inside-225x300.jpg
http://www.iwilltry.org/b/wp-content/uploads/2007/07/heliostat_6_office_outside-225x300.jpg

Taken from these articles:
http://inhabitat.com/easy-to-use-sunflower-heliostat-provides-up-to-500-watts-of-sun-energy-for-homes/
http://www.iwilltry.org/b/projects/build-a-heliostat-for-solar-heating-and-lighting/