Once you get your first taste of solar power, you want more. You can always find ways to use it. Want 30% more?
Back in the 70s and 80s, when solar modules cost a lot more in dollars and dollars were worth a lot more, equipment choices were far more limited and people were always trying to get more power from their solar panels. Makes sense.
Naturally, if you point your solar panel dead-on at the sun you get the most power, so folks came up with schemes to make the panels point right at the sun automatically! Sounds like a good idea, right? It is pretty easy to do with sensors and motors, but that uses some of the power the panel makes. My former business partner built one for one of his modules, just for fun, and it works fine. A really clever fellow came up with one that has a jug of freon on either side of a panel rack. If the sun peeks around to the west side, the west bottle warms up and the east bottle cools down. The pressure difference can drive a cylinder and the panels are caused to lean a little more to the west, and so on for the rest of the day. Next morning it all leans over to the west. It may sound complicated, but is super simple. The upshot is that by tracking the sun you can get about 30% more power from the panels you already own.
Is it a good idea, though? Well, 30% more power is, sure, but overall? First of all, all the panels and the rack are on a single pole, so it has to be a heckuva pole with lots of concrete to hold it in place. In places, like any coastal zone exposed to hurricanes, it may not be rated highly enough to stand up to the wind. One strike. I priced one tracker and it was over $6000, on sale. Two strikes.
Let’s say you have a fixed-mount 3kw PV array. 30% more is about a kw or about 3 more panels. That costs just over $300 at Sun Electronics. Strike three for the tracker! Maybe you don’t have room for 3 more panels, but want that 30% more power. There’s something for that, too. It is called a Maximum Power Point Tracking (MPPT) charge controller. It costs a bit more than an ordinary charge controller, but it allows the panels to operate at their best output voltage. (I notice that the kits Sun Electronics puts together have MPPT controllers, the good ones.) Here’s how it works. We’ve had rain for the last four days, so my batteries on the 24v system are a little depleted. Let’s say they are at 24 volts and a panel is attached and putting out 8 amps. That current, the amps, is pretty much constant. At 24 volts, those 8 amps will give me 192 watts. With an MPPT controller, though, the panel can operate at its best power voltage (you’ll find that on a label on the back of the panel) of, say, 34 volts. 8 amps at 34 volts yields 272 watts or 41% more at peak time! There are some variables and losses to consider, but you can still figure on around 30% more when all is said and done.
And you didn’t spend thousands of dollars!
Here’s one more way to save with an MPPT controller. If you have a 12 volt system, for cabin or boat, for example, you can use 24 volt modules. How does that help? Look at Sun’s price lists and you will see that 24 volt panels cost about half as much, per watt, as 12volt panels! Maybe even a third as much. Yes, you can use 24 volt panels, even in series, to charge a 12 volt battery bank and save money!
I like the FlexMax series of controllers. They are built like a tank, have all sorts of metering data for display and don’t blow up if you connect too many panels. The FM60 and FM80 are solid gear for a serious system.
Take some of the money you saved by not buying the tracker and buy an MPPT charge controller, some more panels and batteries from Sun Electronics. You’ll revel in your awesome newfound power and still have enough money left over for a nice vacation or to catch up on those pesky bills.
By: Neal Collier
