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### Topic: Dual axis tracker design (Read 6357 times)previous topic - next topic

#### PeterH

#15
##### Jul 15, 2014, 06:00 pm
1) Yes. The azimuth angle conceptually gives you an arrow along the ground which points towards the sun. The zenith/altitude angle tells you how far the sun is above the horizon. Together, the azimuth and zenith/altitude angles give you the information needed to point towards the sun in three dimensions.
2) Yes, but you need to understand that the zenith angle and altitude angle are two different ways to express the same thing - zenith angle is the angle down from vertical, and altitude angle is the angle up from horizontal.
3) Your English is a bit mangled but if I understand you correctly then yes, this is correct.

If you want to validate your calculated azimuth and zenith/altitude angle then do the calculation for the current time and position, and see whether the result correctly points to the sun.

#### AJITnayak

#16
##### Jul 16, 2014, 06:39 am
Now all points are cleared. How to check Whether postion i calculated is pointing toward the sun.Here iam attaching output xls i got from nrel .

If i am wrong let me know.
AMPS

#### PeterH

#17
##### Jul 16, 2014, 06:43 pm

How to check Whether postion i calculated is pointing toward the sun.Here iam attaching output xls i got from nrel .

If i am wrong let me know.

The zenith and azimuth columns for the rows you highlighted look credible for a position in the southern hemisphere that was within about eight degrees of the equator, with dawn slightly before 06:00 and dusk slightly before 19:00. You could verify them yourself just by checking whether each pair of figures accurately reflects the position of the sun at that time.

#### AJITnayak

#18
##### Jul 17, 2014, 06:06 am
Code: [Select]
`The zenith and azimuth columns for the rows you highlighted look credible for a position in the southern hemisphere that was within about eight degrees of the equator, with dawn slightly before 06:00 and dusk slightly before 19:00. You could verify them yourself just by checking whether each pair of figures accurately reflects the position of the sun at that time.`

is there any software to check it so i can verify answer.
AMPS

#### jremington

#19
##### Jul 17, 2014, 06:40 am
If the sun is shining, check whether the angles point toward it.

#### PeterH

#20
##### Jul 17, 2014, 02:41 pm

is there any software to check it so i can verify answer.

No.

You're thinking about this the wrong way. The way to tell whether the angles you calculated accurately reflect the actual position of the sun is to compare them with the actual position of the sun. Stand outside. See where the sun is. Estimate the azimuth and zenith angles for its actual position. Compare that to the calculated values.

#### AJITnayak

#21
##### Jul 18, 2014, 07:25 amLast Edit: Jul 18, 2014, 11:50 am by AMPS-N Reason: 1
Here i am attaching Excel sheet of my calculation.
Let me know Which part i have  gone wrong.

Altitude angle is consider from below link
http://www.susdesign.com/popups/sunangle/altitude.php

I am subtracting 360-Azimuth if my actual local time going beyond 12 noon. calculation based on
http://www.pveducation.org/pvcdrom/properties-of-sunlight/azimuth-angle

I stay in INDIA, Bangalore region . SO what should i need to consider my angles.
pseudo code
Code: [Select]
`if(hour_angle> 7Am &  hour_angle <12){tracker_des_azimuth=calculated_azimuth;tracker_des_elevation=-(90-altitude);}else{tracker_des_azimuth=360-calculated_azimuth;tracker_des_elevation=(90-altitude);}`

As per me elevation angle are correct. But Azimuth angle converted are wrong i think. Please help me out here

AMPS

#### PeterH

#22
##### Jul 18, 2014, 03:06 pm
Is this different to the data I already checked in Reply #16, and if so, why?

Did you check the results from Reply #16 against the actual position of the sun?

#### jremington

#23
##### Jul 18, 2014, 05:11 pm
If it is too much trouble to go outside and compare your calculated position with the actual position of the sun, compare your results to the results of the NOAA solar position calculator, which works everywhere on Earth: http://www.esrl.noaa.gov/gmd/grad/solcalc/

If the results differ in any significant way, your program is not working correctly.

#### AJITnayak

#24
##### Jul 19, 2014, 06:27 am
I have tested With Nrel code, NOAA data. I found azimuth and zenith angle are almost equal.
Question i am asking here is Which are two  angles need to be considered for dual axis tracker??

If it single axis tracker we consider altitude/ elevation angle to measure angle.

In excel sheet attached .I found That after 12PM the azimuth angle is going to 21 to Directly 360 degree.
Is here angle need to be subtracted like mention in the link
http://www.pveducation.org/pvcdrom/properties-of-sunlight/azimuth-angle

I have output file attached  i got it from controller.

[font=Verdana]NOTE: azimuth. Elevation are almost same with 0.05 degree accuracy. compared to NREL & NOAA data[/font]
AMPS

#### steinie44

#25
##### Jul 19, 2014, 05:07 pm
Looks to me like you're making a solar pointer rether then a solar tracker.

http://en.wikipedia.org/wiki/Solar_zenith_angle

#### AJITnayak

#26
##### Jul 21, 2014, 06:21 amLast Edit: Jul 21, 2014, 11:12 am by AMPS-N Reason: 1
I got all my angle correctly. I am facing problem to convert inclinometer sensor out put.for 360 degree format.
This How i am converting my angle
Code: [Select]
`float  ARDUINO_ANALOG_SCALING =0.00322265625;void Calc_INC_Pos(){  Inc_Sensor90_Value= analogRead(A0);   Inc_Sensor360_Value= analogRead(A1);Voltage90_Value= Inc_Sensor90_Value*ARDUINO_ANALOG_SCALING;  Voltage360_value= Inc_Sensor360_Value*ARDUINO_ANALOG_SCALING;tracker_actual_elevation = 45*  Voltage90_Value - 112.5 ; tracker_actual_azimuth=45*Voltage360_value-112.5;}`

AMPS

#### PeterH

#27
##### Jul 21, 2014, 02:43 pm

I got all my angle correctly. I am facing problem to convert inclinometer sensor out put.for 360 degree format.

I assume you mean you know how to calculate the sun's position in terms of azimuth and zenith/altitude angles.

You don't say what the inclinometer is to be used for. I guess you're trying to measure the zenith/altitude angle of your tracker so that you can use a closed loop feedback controller to steer it to the sun's altitude/zenith angle. Is that correct? If so, you need to know how the values you get from the inclinometer relate to the tracker's zenith/altitude angle. You can establish that just by seeing what readings you get as you physically move the sensor.

I don't see how an inclinometer reading would involve 360 degrees so perhaps I've misunderstood what you're trying to do with it.

#### Dexterbot

#28
##### Jul 21, 2014, 02:56 pm
i build a antena tracker working on one rssi signal ,, why not use a light sensor for tracking the most voltage coming in 2 the solar pannel ,,

i have build in option , for scanning  the stronges analog input voltage , every motor step it wil record the voltages in to the eprom mem , after the sweep it wil go to the strongest position found in memory ,  soem friend uses this for his solar pannel

#### PeterH

#29
##### Jul 21, 2014, 07:29 pm

every motor step it wil record the voltages in to the eprom mem , after the sweep it wil go to the strongest position found in memory ,  soem friend uses this for his solar pannel

Why save them in EEPROM? Surely it's the target position which needs to be persisted, not the instantaneous scan results. For a solar tracker where the answer is inherently changing, I don't see any reason to persist the answer either - after any reset you'd need to rescan anyway to find the new optimum. The scanning approach would also be inferior to using a pair of LDRs to tell you which direction to move towards the optimum, since that avoids needing to continuously hunt to find the optimum as it moves through the day.

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