Systems, Sites and Building (Sparkman)

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Bus Stop Update 10/26/2010

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Over the weekend, I scripted an optimized canopy for our bus stop project. Our site is located near Alderman Library/Special Collections with a tree that blocks southern exposure (see previous post). We have decided to stick with the site, as it poses challenges of solar gain and heating during the winter.

A primary function of our bus stop is to provide an underground space for commuters to shower. We will capture water, heat, and energy for our showers with a large bus stop canopy (heated water will be stored in cisterns). Since peak commuter times occur in the morning and evening, the canopy is optimized for solar gain at low altitudes from east and west—when the tree is not blocking solar exposure (the “peak azimuth” is represented in blue on my “solar optimization” diagrams below).

I chose a simple saddle form to optimize solar gain in the mornings and evenings (one half of the canopy is optimized for morning, and one half is optimized for evenings). Due to its curvature, a simple saddle will perform much better than a flat surface (a flat surface can only be optimized for southern exposure, which is blocked by a tree anyway). To optimize the surface throughout the year, I scripted a Grasshoppper component that compares the four “control points” of a simple-saddle shape to the sun’s azimuth and altitude for mornings and evenings throughout the year  (see the diagrams of “solar optimization” below).

Another advantage of a simple-saddle is constructability: it’s edges are all straight lines. Our canopy would be a rigid (about 1′ thick) panelized system comprised of three layers: a top layer of thin film photovoltaics (for energy capture), a middle-layer of thin tubing (we would pump water through the tubing and heat it by solar gain), and a bottom-layer of a reflective surface (which would reflect the sun back up into the tubing and solarvoltaics, maximizing our gain). The simple saddle is also an optimized shape for collecting rain water. We would collect water with cisterns at the canopy’s lower edges.

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Written by csparkman

October 26, 2010 at 5:39 pm

Posted in Uncategorized

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