Importance of Visualizing
What a Design Really Looks Like

By TK NG

             If you start off a design on plan, you should figure out at the same time what it really looks like, such as producing the side elevations, or using computer visualization tools (e.g. Building Information Modelling – BIM) to generate 3D or walk-through images, etc. to help assess its practicability.

2.         Taking rooftop photovoltaic (PV) panel installation in Hong Kong as an example, Figure 1 shows the layout designs of PV panels (in blue) on the upper roofs of two similar buildings A and B with different orientations.  The panels should all be tilted at about 22 degree (approximate latitude of Hong Kong) facing south in order to capture the most amount of sunlight the whole year round for maximizing the electricity yield.  For Building B, the PV panels can no longer be placed side by side in a straight line but are offset in order to fulfil the aforesaid tilting angle and direction criteria.

Figure 1

3.         At first glance, the panels in both buildings seem to be lying on a single plane when viewing from the top, but it is not the case for Building BFigure 2 is the East elevations of the two buildings and you can see that the PV panels in Building B are actually staggered.

Figure 2

4.         In the case of Building A, unobstructed sunlight can be received by each PV panel when the sun rises from the East and sinks to the West, since all the panels are located on the same plane.  Please refer to Figure 3 for illustration of the sun path and the shadow of the PV panels cast onto the upper roof.

Figure 3

5.         For Building B, when the sun moves from East towards West before noon, each PV panel would only cast its shadow onto the upper roof (Figure 4 refers).

Figure 4

6.         When the sun moves to the West in the afternoon, each PV panel begins to cast part of its shadow onto the one to its east, i.e. on its right side.  The shadow of each panel would stretch out as the sun gradually descends towards the horizon, making the panel being partially shadowed by its neighbour less and less effective in generating electricity, or even unable to function at all.  Figure 5 is an illustration of the shadow problem encountered in Building B.  The solution is to line up the PV panels in two or three rows with adequate separation to prevent mutual shadowing between them.

Figure 5

7.         Without going through the process of design visualization, which can be done through conventional drawing practices, use of computer tools or even mental processes, possible inadequacy would stay with a design without being noticed until at a late stage.  Abortive works, additional cost and/or time may then be incurred.

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