An Elaboration on the Design Principles of a Universal-Solar-chart Shadow-plotter

Abstract

To comply with insolation requirements of some countries [1,2], recommendations have been made on several graphical methods for estimating the shadow of a building or its features cast by sunlight on other features or buildings on the drawing paper [3,4]. These methods use a series of graphs for estimating the solar shadow. To many architects, these methods are not easy to apprehend and are time-consuming for implementation. Furthermore, many projection lines will have to be drawn on the drawing paper, causing likely confusion and difficulty in identifying each line. Also, separate sheets of pre-drawn graphs have to be produced for different latitudes. There are now software developed for architects and students [5] to help them design for fenestration and obtain solar shading masks, and for obtaining solar shadows for buildings. In the learning process of a person, however, physical tools do maintain their contribution, and complement learning with the computer software. In pursuing this complementing contribution of the physical tools, a physical universal-solar-chart shadowplotter has been invented. This tool performs as a universal solar chart [6] for relating the latitude, day, apparent solar time, solar azimuth angle, and solar altitude angle, for any latitude selected. Also it enables an efficient plotting of the shadow of an object, such as the corner of a house, cast by the sun light on the ground, when the solar azimuth angle and solar altitude angle are known. In fact, these angles can also be found by the tool. This paper reports on the principles of design and operation of this tool. This tool however is first seen in its patented form [7], which does not contain sufficiently illustration of the principles to the normal architectural science readers. Therefore this paper serves the elaboration purpose.