A Simple Heliodon System for Horizontal Placed Models

Most probably, all our buildings are affected by sunlight. Hence, the ignorance of the sun's impact results in overheating, glare, and missed opportunities for the positive use of daylight, leading to wasted energy. Heliodon is considered to be a powerful tool that can aid students, professionals, building developers and users to better understand the relationship between the sun's path and its effects on the architectural model(s). Most of the heliodons are relatively expensive and complex in operation. Thus, the need to design and build a simple and relatively inexpensive one emerged. It was proposed to work on this heliodon as a team project in the environmental control class “fall-2016”. The authors put the design concept and introduced a mathematical calculations table to be used with the physical heliodon, while nine students participated in the manufacturing process. The design concept is based on determining the sun's position by converting the Altitude and Azimuth angels to their corresponding measurements on the (X, Y & Z) coordinates (in relation to the observer's location). One light source can be moved on a set of graded tubes assembled in the shape of a wire frame box (thus the X, Y & Z distances could be measured) to simulate the sun's position and its lighting conditions for any latitude, at any time for any chosen day.

1. Introduction 1. Nearly, 40% of the energy produced worldwide is consumed by buildings; this is HTXLYDOHQW WR 0WRH ´million ton oil equivalentsµ SHU RQH \HDU $WWPDQQ ,Q Egypt, 52% of the produced electricity is consumed only by the residential buildings, while 90% of the electric power plants depend on non-renewable energy resources to operate (URL4)(www.moee.gov.eg). Thus, buildings are considered to be one of the main causes of climate change. 6WXG\LQJ WKH VXQ·V LPSDFW RQ EXLOGLQJV LV WKH ILUVW step on the long way of solar-responsive design, where the most important goals are: ƒ The maximum harvesting of winter sun ƒ The optimum control of summer sun ƒ The benefits of the natural daylighting ´7KH natural daylight that a 0.9m × 1.5m window can provide is equivalent to 100 ² 60W LQFDQGHVFHQW ODPSVµ /HFKQHU Hence, the comprehensive understanding of solar geometry and its consequences is necessary for a successful architectural design. Starting from the very early model made by Dufton-Bachett in 1931, passing by that one 55 developed by George Malcolm Beal in 1953(Beal, 1957, and till the most recent models of Lechner 2001 and his successors, heliodons have been considered one of the most powerful tools that can aid students, professionals, building developers and users to better understand the relationship between a building and the sun (Lechner, 2001). Since heliodons have been developed mainly to study the effect of the sunlight on a given building(s) model, three main variables are always the dominant constraints for any heliodon design concept, these variables are: ƒ Latitude determines the relation between the VXQ·V SDWK DQG WKH JHRJUDSKLFDO ORFDWLRQ RQ WKH HDUWK·V VXUIDFH ƒ Day of the year: specifies the declination of the sun on a specific day. ƒ Time of the day: determLQHV WKH VXQ·V SRVLWLRQ between the east and the west (Cheung, 2000). These three variables guide the researcher to REWDLQ WZR DQJHOV WKDW KHOS WR DOORFDWH WKH VXQ·V position (Figure 1). These two angels are: ƒ Altitude (ALT): Measured upwards from the hori]RQ ZKHUH WKH REVHUYHU·V ORFDWLRQ LV DW WKH center of the skydome. ƒ Azimuth (AZI): measured in the horizontal plane from north or south (Szokolay, 2008). Heliodon designs could be classified into two groups, depending on the positions of both of the light source and the building model: ƒ Tilted / moving building model while the light source (s) is either fixed or moving. ƒ Fixed (horizontal) building model while the light source is moving (Cheung, 2011). A quick glance on both of the two types declares that the first type has significant disadvantages: Holding the model in steep angels may result in difficulty in viewing or causing it to slide out of position. Furthermore, it GRHVQ·W VLPXODWH RXU HYHU\GD\ H[SHULHQFH RI WKH sun moving across the skydome. Meanwhile, the fixed building model types are complicated to manufacture and operate, relatively large (for more accuracy) thus, require larger space during operation and / or storage (most of them), and to somehow more expensive (URL3) (www.heliodon.org).

The Need for This Heliodon
Our target in the environmental control class was to encourage the students to build their own heliodon, taking into consideration that it should be easy to understand, can be constructed inside the CIC campus with simple tools, requires a relatively small space during both operation and storage and relatively inexpensive. To achieve the previous goals, the fixed building model type was selected; the concept of converting both of the Altitude and the Azimuth angels to their corresponding (X, Y & Z) FRRUGLQDWHV )LJXUH ´ZLWK D PRYLQJ VLQJOH OLJKW VRXUFH WR VLPXODWH WKH VXQ·V SRVLWLRQµ ZDV chosen. The UPVC pipes and connections were proposed as a construction material for the KHOLRGRQ ´UHODWLYHO\ ULJLG DQG FKHDSµ while the The Altitude angel 5cm thick rigid foam and 5mm thick white cardboard were the materials for the base. Design concept and calculations, supervision and the orientation of the manufacturing SURFHVV ZHUH WKH DXWKRUV· WDVNV ZKLOH WKH construction was accomplished by a group of nine students.

Solar Position Calculations
The authors relied on external software ´6XQ3RVLWLRQµ WR GHWHUPLQH WKH $/7 $=I angels RI WKH VXQ·V SRVLWLRQ IRU DQ\ ODWLWXGH RQ DQ\ GD\ of the year and at any time of the day. Also, to generate the necessary input data to build a calculations table that will be used in the design and manufacturing process of the heliodon(URL5)(www.susdesign.com/sunposition ). The main function of the calculations table is to FKDQJH WKH SDUDPHWHUV RI WKH VXQ·V SRVLWLRQ IURP WKH ´$/7 DQG $=, DQJOHV V\VWHPµ WR WKH coordinates system through a series of HTXDWLRQV 7KH ´6XQ3RVLWLRQµ VRIWZDUH ZDV chosen for two main reasons: ƒ It is comprehensive software, but yet, with an HDV\ LQWHUIDFH IRU VWXGHQWV· LQWHUDFWLRQ ƒ It is open-source software, which can be accessed online easily and freely by students. Table  The  The correction factor for the Azimuth angel: measured in degrees and generated automatically, its value is either (0 or 180) based on the input value of the Zero Azimuth Direction (180 in case of the ZADN=1 and 0 in case of the ZADS =1). Corrected Azimuth angle: measured in degrees and generated automatically based on the input value of the zero Azimuth direction (N or S), the output value of the Azimuth angle correction factor and the output value of the absolute angle. Skydome radius: a pre-set data that is measured in centimeters; its value represents the maximum allowable movement distance of the light source in any direction starting from the KHOLRGRQ·V RULJLQ SRLQW 2EVHUYHU·V SRLQW The distances on the (Z) coordinate: measured in centimeters; it is generated automatically based on the output values of the Altitude angle / Sine and the pre-set value of the skydome radius. The Z Coordinate movement direction: measured in (+) only. The distances on the (Y) coordinate: measured in centimeters, and is generated automatically based on the values of skydome radius projection on the horizontal plane and the Azimuth angle cosine. The Y coordinate movement direction: measured either in (+) or in (-); its values are generated automatically based on the output values of Y coordinate distance, the input values of ZAD (N or S) in addition to the output values of absolute Azimuth angel.

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The distances on the X Coordinate: measured in centimeters; it is generated automatically based on the output values of skydome radius projection in addition to the output values of the distance of Y coordinate. The X coordinate movement direction: measured either in (+) or in (-); its values are generated automatically based on the output values of the distance on the X coordinate, the pre-set values of time, the input values of the ZAD (N or S) in addition to the input value of the original Azimuth angle.

4.1VALIDATION OF THE CALCULATIONS TABLE OUTPUT
To validate the output data that was obtained from the calculations table ´IRU specific latitude DQG D FHUWDLQ WLPH RI D FHUWDLQ GD\µ LW ZDV important to compare it with a reference data for the same variables. The latitude of 30.04 N (Cairo ² Egypt) was chosen and the hours from (6 ² 18) for the longest and shortest days of the year (21st. of June and 21st. of December) were selected for the validation. The output data UHVXOWV ´WKH PHDVXULQJ GLVWDQFHV RQ WKH ; < DQG = FRRUGLQDWHVµ IRU &DLUR ² Egypt at the selected hours on the  (Figure 2).

Heliodon Construction
For the purpose of learning in the environmental control Lab., the skydome radius was selected to EH FP ´WKLV FRXOG EH JUHDWHU RU VPDOOHU according to the available space, the required accuracy and the scale of the model(s) understudyµ 7KH 839& SLSHV ZHUH FXW DQG DVVHPEOHG ´ZLWK FRQQHFWLRQVµ WR FRQVWUXFW D wireframe like box ´D ELW ODUJHU WR DOORZ WKH OLJKW VRXUFH WR PRYH FP LQ WKH WKUHH FRRUGLQDWHVµ DV VKRZQ (Figure 3 & 7). The (Pz1, Pz2, Pz3 & Pz4) pipes were  Output ( ) Output ( ) Output ( ) Pre-set Output ( ) Output ( ) Output ( ) Output ( ) Output ( ) Output ( ) Output ( ) "Degrees" "Degrees" "Degrees" "cm" "cm" "+" "cm" "cm" "+" / "-" "cm" "+" / "-" 006.  -) on the X coordinate and finally (Py) pipe was graded from its midpoint (0 to 100cm & 0 to -100cm) to illustrate the measuring units (+ & -) on the Y coordinate. Bolts (B1, B2, B3 and B4) can be loosened to allow (Px1and Px2) pipes to move freely up and down on the (Pz1, Pz2, Pz3 and Pz4) pipes or can be tightened to fix them in the required Z coordinate position (Figure 4). Bolts (B5 and B6) can be loosened allowing the (Py) Pipe to move feely to the right or to the left on (Px1 and Px2) pipes   or can be tightened to fix it in the required X coordinate position ( Figure 5). A (100W) incandescent lamp was used as a light source to simulate the sunlight rays and it can move back and forth on the (Py) Pipe to reach the required < FRRUGLQDWH SRVLWLRQ DQG VLPXODWH WKH VXQ·V position ( Figure 6). The base was made of 5cm WKLFN ULJLG IRDP EHWZHHQ WZR OD\HUV RI ´ FP ð FP ð PPµ FDUGERDUG VKHHWV be oriented with respect to the four cardinal directions). ƒ Determine the latitude of the building, date of the day and the time of the selected day. ƒ Use the previous constrains as input data in WKH ´6XQ3RVLWLRQµ VRIWZDUH RU DQ\ VLPLODU software) to generate the corresponding Altitude and Altitude angels. ƒ Use all the predetermined constrains and the generated angles as input data in the designed calculations table to generate the corresponding measuring distances on the X, Y and Z coordinates. ƒ Adjust the position of the light source according to the generated measures on ƒ the heliodon. ƒ Plug in the electrical cable, turn on the lamp and observe the effect of the light on the model (Figure 8). ƒ After completing the study turn of the lamp and unplug the electrical cable. ƒ In case of storage for long periods, disassemble the heliodon parts and store it.

Conclusion
The main target of this work was to encourage the students in the environmental control class to participate in the design and the manufacturing of their own heliodon, hence their awareness of both of the solar geometry and the solarresponsive design could be enhanced. This heliodon could be designed and constructed with different scales according to the required accuracy; the available space and budget, and can be disassembled and stored in small space for future use.

Tuning & Future Work
We aim to reconstruct this heliodon system with more durable material (stainless steel pipes), more efficient bracing system and a LED light source instead of the incandescent lamp to give more parallel light rays, thus, a more realistic sunlight simulation. Also, we hope we can make a fruitful collaboration with other engineering specializations to make the system fully operated and controlled by a commuter system.

Acknowledgement
We would like to give special thanks to our diligent students who participated in the construction process: Andrew Ghettany, Mahmoud El-Zayaty, Mohamed Wahba, Mohamed Ezz El-Dein, Mohamed Essam, Mostafa Helal, Omar El-Shahawai, Omar Abd El-Gawad and Ziad Hassan. Also we would like to thank those so special students of the environmental control class ´&RKRUW-µ D OLVW RI WKHLU QDPHV FRXOG EH found on the following link: (URL1)(https://drive.google.com/open?id=0B-bNxtEORp3VTUdWVXlaYldLdVk).