Solar Power

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Keeping with the green theme, I decided to use a solar panel to power the electronics.


The design of the power system is based on the expected power use of the system.  Calculations were based on the information on the Tasman Energy web site. 


Running two controllers at about 100mA constantly at 12v is 1.2Watts.  For 24 hours, thats 28.8 Watt hours.

And two valves, running twice a week for 1 hour using 2A.  This is 96 Watts over a week, or about 0.6 Watt hours.

A grand total of 29.4WH.

Divide the power requirement by 0.7 to allow for power losses, gives 42WH.

I got this from the BOM site.  For Melbourne, it is 5-6 hours average over the year. (3-4 during July)

Dividing the watt hours requirements by the worst case, 3 gives a required solar panel producing 14 Watts.

I purchased a 16Watt Kyocera panel, with an 18Ah battery.  I picked an oversized regulator; because of its features not it size.


Solar Panel

I chose a 16Watt Solar Panel made by Kyocera.  I got it from the Rainbow Power Company.  I chose this panel because it came with a 25 year warranty and a mounting pole and frame.

Because the panel could be mounted on a pole, I used this pole to mount it to the base of my TV antenna on the roof.  There's a picture below.  The pole can't be seen from the photo.  It runs horizontally to the antenna pole and is clamped at right angles.  There was no way I was going to climb back up on to the roof just to take the photo.  When I installed the panel, I hired a roofer's safety harness kit from my local hire place.  I know too many people who have fallen off roofs or tall ladders and seriously injured themselves.  So far no problems.


The regulator is responsible for taking power from the solar panel, charging the battery and running the load.  It is a complicate process; solar panels can generate up to 20 volts in full sunlight, and none at night; batteries will explode if over charged, and damaged if run flat.  The regulator needs to be able to handle these conditions.

I chose the Steca PR1010.  Most solar regulators have all the required features.  I chose the PR1010 because it has an informative LCD.  It shows battery state of charge, voltage, solar current, load current, and it keeps track of Ah in and out.  I got mine from the Solar Shop

I mounted the regulator in the garage out of the elements.  Wire was run through the roof from the panel into the garage.  The regulator is mounted on a bracket at the front of a small shelf.  Behind the regulator sits the battery.  This is shown below.  Click on it to see a larger image; you may be able to make some details on the LCD; the battery is at 81%.


The battery, shown behind the regulator in the photo above, is a 12v 18Ah sealed lead acid battery.  I also got it from the Rainbow Power Company.  The battery cost almost twice that of the regular SLA batteries of similar capacity, but I chose this one because it was designed for "Cyclic Applications".  Fingers crossed it does last, and I wasn't taken by marketing hype.


The panel has been installed for about 5 days.  In that time, it has taken the batteries state of charge from 80% to 100%.  It hasn't rained yet and there is not water in the tanks to test the valves, but I haven't had any glitches yet, but only time will tell.