Energy Efficiency Made Simple Vol IV 2015

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would be 88 – 64 = 24 degrees. The loss due to misalignment is proportional to the cosine of the deviation from normal. Cos24 = 0,9135 which represents a loss of 8,6455%. A simple way around this would be to make a manual adjustment of the panel’s ele- vation occasionally. The system could be syn- chronised daily by returning the array to the vertical position (corresponding to 6:00) after sundown, ready for the next day). Rotation would com- mence at 6:00 facing East.

Test rig construction Figure 2 is a photograph of the test unit. On the right hand is the fixed panel and the rotating panel is on the left. Note the black levelling screws and the red bull’s eye spirit level used to level the rig. All parts were machined on the company’s computer controlled router. The outer frame of the steering mechanism is at a 26 degree an- gle to the (level) base and is rotated by a synchronous one revolution per day motor. The inner frame has provision for adjustment to compensate for the seasonal variations in the sun’s path. The brass pipes provide a means to align the panels at right angles to the sun at 12:08, corre- sponding to our position of 28 degrees East, and pointing due North. In both cases the shadow of the pipe was the size of the pipe base. At this point the motor was started. The motor had been purchased as providing clockwise (CW) ro- tation and we had naively assumed that this referred to the rotation

Figure 3: Connections to a datalogger board.

• Two 12 bit analogue outputs (0 - 10 V out) • RS232 communications port • 4 line character Liquid Crystal Display (LCD) port • Embedded microchip 18F252 processor

System operation The analogue signals were read at one second intervals for one min- ute, then averaged. The same arithmetic was performed for an hour. Finally, the hour totals were added to give a day total. Logging started at 07:00 and continued until sundown. Graphing was performed by the economically priced and easy to use MakerPlot program. All the system power was derived from a battery backed sinewave inverter.

direction looking at the output shaft side. With the publication deadline looming, we discovered that the ro- tation was counterclockwise (CCW). ‘Houston, we have an anomaly!’ We replaced the motor and fortu- nately all was well. The panels were rated at 1,5 V 500 mA, so they were terminated with 2,2 Ohm resistors, giving about one Volt at midday. Both panels provided outputs within 2% of each other. Figure 3 shows the connections to a Techlyn datalogger board. The board provides: • Eight 12 bit analogue inputs (0 - 5 V)

Figure 4: Plot screen. Note the built in averaging function below the meters.

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ENERGY EFFICIENCY MADE SIMPLE 2015