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Energy-Conscious Planning and Zoning . |
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3.2.3 Aids
for the Study of Sunlight Conditions
Horizontoscope A simple but very useful aid for the preparation of images showing buildings at an existing location is the "Horizontoscope" developed by TONNE and produced by the Institute for Daylight Technology in Stuttgart (see Figure 3/13a and Figure 3/13b): The Horizontoscope consists of a Plexiglas half-sphere with a level, equally transparent bottom, which can be placed on a diagrammatic disk as shown in Figure 3/10. At the location to be examined, the device is held horizontally by means of an integrated compass. When viewed from above, the reflective half-sphere then shows the building picture in polar projection. In this way the building picture is reflected on the underlying diagram, allowing an immediate evaluation of the sunlight conditions. These shading diagrams can
of course also be produced with appropriate programs when
digital plans are available. The computing model SHADOW has been
developed specially for the assessment of shortwave radiation (sunlight)
in a model area. It can be used both for studies in urban areas
and for issues of land climatology or agrarian meteorology, as
the program takes into consideration the topography of the land
in addition to the arrangement of shading objects. Computer Simulation Programs More intricate aids are necessary for the assessment of sunlight conditions in complex built-up areas. For this purpose, GORETZKI (1990) developed a computer model (GOSOL) as a basis for energy simulations, which makes possible the assessment of the solar-energy characteristics of a planning concept as well as its spatial depiction. The program, which runs on the PC platform, is arranged as a drafting instrument with a CAD interface. Up to 700 trees (with monthly variations in shading) and 700 predefined buildings with a total of up to 5400 walls and 3200 windows can be placed in the model. The solar radiation energy for each of these buildings is calculated in hourly intervals for each month, divided into reflective, diffuse, and direct radiation. Inclination and orientation of window surfaces as well as their shading from vegetation, neighboring buildings, and landforms are taken into consideration and quantitatively registered. Based on the local climatic data the heating requirements, solar heating contribution, and the remaining heating energy needs are reported for the entire planned area as well as for each building on the basis of building characteristics. Planning variants can thus be compared quantitatively in light of their energetic characteristics, allowing individual buildings or groups of buildings with inefficient sunlight conditions to be identified. Figure 3/14 shows as a result of such a calculation a shadow diagram for a specified time. In the Figure 3/15 the solar gain is given for the same investigated buildings. In the "Solar booklet - maesures for urban planning - (GOETZKI P., Maass I., 2002) edited by the Ministry of Economics Baden-Württemberg shows with a lot of examples the possibilities of a energy-conscious planning and zoning. Study of Shading on Models If a physical model of planned buildings or developments is constructed for wind tunnel studies (see Chapter 4.2) or other purposes, this raises the possibility of a shading study by means of illuminating the model. A strong light source functions as the sun, for which the geometric relationships relative to the chosen day and hour must correspond to the actual position of the sun. The resultant shading pictures are then documented photographically and evaluated. Figure 3/16 from LOHMEYER et al. (1992) shows a sketch of the local situation where an extensive new development (depicted in black) is planned. The position labeled as point 6 corresponds to the picture in Figure 3/11. The effects of the indicated development, depicted from the perspective of an affected location, can now be examined in the shading portrayal of Figure 3/17a and 3/17b in a spatial context relative to a specific date (here: 2.5 hours after sunrise in the middle of December). |
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| Fig. 3/13b: Horiozontoscope | |||
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| Fig. 3/14: Depiction of the shadows created by a group of buildings via computer simulation for 15 March, 15:00 (GORETZKI, 1989) | |||
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| Fig. 3/15: Computer simulation for determining the solar energy gains of a group of buildings (GORETZKI, 1989) | |||
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| Fig. 3/16: Layout plan for a shadow model (at the same time also for a wind tunnel model), cf. Fig. 3/11 and 3/17; (from: LOHMEYER et al., 1992) | |||
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| Fig. 3/17a: Shadow simulation (current state); about 2.5 hours after sunrise (on 15 December) (from: LOHMEYER et al., 1992) | |||
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| Fig. 3/17b: Shadow simulation (planned state); about 2.5 hours after sunrise (on 15 December) (from: LOHMEYER et al., 1992) | |||
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