The apparent position of the sun varies throughout the year and throughout the day. Solar panels can be left at the same angle all year round in the worst case. It’s possible, but costly to track the sun across the sky and alter the angle of the panels to get most bang for your solar buck, but it’s generally good enough just to position the panels in a southerly direction and then if possible adjust the elevation – i. e. angle them up and down – as the sun rises and falls in the sky.
In the winter, an angle of about 60 degrees from the horizontal will give you most power and around 40 degrees in the August. In the summer, the sun is virtually overhead, so if your panels are nearly vertical in a winter position, they’ll produce power just not as much as they are capable of. I’ve got an electric car (Tesla) which takes 90KW hours to charge. So, if I use 1KW for 90 hours which is like boiling a kettle solidly for nearly four days and nights or more practically, 5KW during the day, if I don’t adjust the panel angles I’ll eat well into our power budget. I’ll only charge the car during the day when there’s excess power after air on, cooking, pool pump, etc.
I want to glean the maximum power for the lowest cost, so I’m repurposing some linear actuators which are generally used to adjust the backrest on a bed or on a sofa. I’ve found some units that are IP65 rated which means that they’re weatherproof… why they should be waterproof is beyond me but for around £40 from Ebay, I’m not complaining.
These actuators can lift 150Kg each, so are very meaty. The solar charger/inverters that I’m using are from Mppsolar (PIP4048MS) and require at least 48V to work. However, they can use up to 130V in theory. I’m hooking three 24 volt panels in series giving me between 72 and 90 volts, which will help give us some power even when it’s not that sunny as there’ll be sufficient voltage to put some power into the batteries.
I plan on making some simple frames to take 9 panels each as this seems to be the optimum for my plans. The panels weigh about 18Kg each, so with the steel frames it should all come in at under 200Kg. I’m going to hinge the bottom of the frames so that I can use two actuator arms to push or pull the panels to the correct angle.
Aha, I hear you ask. But how do you know what angle to set them to? Well, there is a website called Suncalc.org and if you upload your GPS coordinates or lattitude and longitude, you can download the angle of the sun above the horizon at every minute of the day and set the panel angle accordingly. So long as the planet keeps spinning on its axis and revolving around the sun, it should work. If it doesn’t then we’re all doomed anyway and inefficient solar panels will be the least of our problems!
I’m never keen on moving parts as they do tend to break, so I’ve ordered some laser distance measurement devices (guess where from?) for a couple of quid each to see if I can use a bit of clever maths to determine the panel angle from their distance from the sensors. These little cuties are used in robot vacuum cleaners, so are available in large volumes very inexpensively.
It did occur to me that if two powerful actuators are moving a panel and one fails, then the whole thing could be twisted and broken. So, I’m going to also use the laser sensors to make sure that both panels are moving correctly and if there’s a failure, I’ll get an email telling me which one has failed. Seemples.
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