Concept Generation and Selection
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Design Requirements for All Prototypes:
Due to size limitations of how big we can construct the prototypes, all prototypes will be a scale model of one of the smallest Wal-mart buildings. Wal-Mart was chosen as our warehouse like building, because their are thousands of them worldwide and their interior is like a storage warehouse.
First a scaling factor had to be calculated, and to find this we used the material which would be the limiting factor in our prototypes: the thickness of the prototype insulation. Since the smallest insulating material we could find was 3/32in cork roll, that will be used as our prototypes insulation. The average wall of a warehouse like building has insulation of R14, which is generally 3.5in thick. So by using the thickness of the insulation of our prototype and the average insulation of the walls of an average warehouse, our scalling factor for both the insulation thickness and R-value became approximately 0.024.
The small Wal-Mart we have chosen to model has interior dimensions of 30,000sq ft with 25ft ceilings. So by using the scaling factor which we calculated, that would make the interior dimensions of our prototype to be approximately 4.5ft x 4.5ft x 0.6ft.
All Prototypes must also be equiped with a heating/cooling system with will be able to keep the interior prototype at approximately room temperature (70 degrees F), and an internal temperature measurement system which would allow the interior temperature to be recorded every 10 minutes without the prototype being opened.
Design Requirements for Only Passive Prototype:
The stationary refelective panels of the passive prototype must be set to the optimum angle to allow the solar radiation to be reflected in the summer and absorbed in the winter. The picture below shows how during the summer the solar radiation is comming in at a steeper angel than in the winter, so based on the average sun angles of the Flagstaff, AZ area for Spring/Summer and Fall/Winter our team found this optimum angle to be 43 degrees.
Source: http://physics.weber.edu
Design Requirements for Only Active Prototype:
The reflective panels must rotate throughout the day to either reflect or allow aborption of the maximum amount of solar radiation. This will be achieved by creating a program which will rotate the panels every few minutes to a new angle. How much the angle of the panels changes every few minutes will depend upon the sunrise and sunset angle for the Flagstaff, AZ area, and the average sunrise and sunset times.
By using the sunrise/sunset angle and times, the program can be used to move the panels at a certain interval a set amount of degrees so that as the day goes on the angle of the panes will, theoretically, follow the sun.
Chosen Internal Temperature Measurement System:
The fully automatic internal temperature measurement system was shown to be the best system design out of the three that were created. This system will use a digit thermosat that will be able to send the temperature reading of the interior the prototypes to the A/C control system.
Chosen Heating/Cooling System:
There were three heating/cooling systems which were designed and researched; however, in the end, our team chose an automated air system. This system will blow either hot or cold air based on the measurement of the interior temperature of the prototype. The heating/cooling system itself will not directly use the internal temperature measurement but instead a control system will be used to turn on and off the heating or cooling air flow.
Control Systems:
Two audrino boards will be used to control the following systems: the motors attached to the reflective panels for the active roof prototype and the heating/cooling system.