Getting the most from your PV Panels


I wanted to run all lights, a power-hungry laptop (something I only discovered after I started), medium-sized fridge, wireless router, solar production & power consumption monitoring equipment, and battery charging for laptop, cellphone, camera and power drill. Could I do all this off one 150W PV panel (costing about R1700)?  Be patient, this is an unfolding story 🙂

This is an incremental experiment.  Starting off with “What is the most I can achieve for the least cost, and what lifestyle changes are necessary to achieve that?”  And then growing the solar installation to cater for what many regard as normal living.

Since I was starting at the height of summer, commonsense told me that a horizontal panel would be just fine, I “plonked” my panel on the almost flat and not-too-sturdy roof of a small outbuilding, using the rather pricey but rock-solid brackets from ExSolar, who were horrified by my plan.  But this was my temporary solution whereas they always fix panels that will last the lifetime of a sturdy roof.

150 watt panel

What was great for December and January, wasn’t great for February and March, and electricity production was getting worse.  The sun’s angle was changing and the panel was getting less direct rays, apart from diminishing Solar Insolation.

Solar Insolation is the amount of electromagnetic energy (solar radiation) reaching the surface of the earth. Basically that means how much sunlight is shining down on us.  It varies with the seasons.

[table “” not found /]

Info from Solar Electricity Handbook.  Click here for their nifty tool to calculate your needs.

So, with flat panels in winter, I would only be producing about 25% of what I was achieving in mid-summer.  By changing the panels’ angle, I can achieve double the power that a flat panel will achieve in winter.

The best year-round angle for panels that are fixed is about 56 degrees but, since I want to maximise every bit of technology I have, I decided to go with completely variable angles throughout the year.  Of course, if I could track the sun throughout the day it would be even better, but that was too much of a complication.

And so, here was my solution:

Tilting bracket for PV panels
Some 3mm aluminium angles, two stainless steel solid rods found in the off-cuts bin, and some nuts and bolts.
It’s ready for the second PV panel.

Again this is a temporary solution, because I may do something completely different when I go to four panels, which will see me through winter and many more appliances.

Finding Solar Noon

You will lose a few percent of your panels’ full potential if it doesn’t face true north (not magnetic) and even more if the vertical angle to the sun is not optimal for the time of year. You can either get that right or just throw more money at technology.

So where does one start?

There are many websites to choose from but one example is suncalc.net where you can type in your location or drag the map until your exact location is in the centre of the screen.  For Stellenbosch it shows that solar noon is at 12:42 at this time of year.  It varies day by day.

Finding solar noon -- click on the map to go to the actual site
Finding solar noon — click on the map to go to the actual site to find your Solar Noon, and other data.

Once you’ve got the time of your Solar Noon, it time for the test.  The easiest way is to get the cap of an aerosol spray and glue that onto a piece of white cardboard.

Easy and cheap way to pinpoint your Solar North and the best angle for your PV Panel
When your PV panel is correctly orientated to True North, the aerosol cap won’t cast any shadow to the left or right.
(I’m slightly out because I didn’t calculate for the slight slope of the roof.)
In the right hand pic, you’ll see the shadow above the aerosol cap when the cardboard lies against the panel.
That means the angle is wrong: the panel was set up at the end of March and it needs to be raised for winter settings.

Is the PV Panel working well?  A Multimeter (about R180) shows readings at the MTTP Power Controller from the PV Panel at 17.6 volts — 19.9 volts for most of the day.

This panel seems to perform far better than I expected in overcast weather.  It does drop to about 15 volts — 17.5 volts on very overcast, grey days. There was one Friday afternoon recently during a really big storm, when it went really dark, and the panel produced no power for about 30 minutes. So, I’m feeling optimistic about winter!


Leave a Reply

Your email address will not be published.