Lets say I have an existing solar power system. If I want to add a wind turbine or I get more solar panels, is it as easy as just attaching the new sources of energy to my charge controller (in series or parallel) or is it more involved than this?

I want to start with a small system, one panel. But I want to be able to easily add more sources, like other panels or wind turbines. I want to make sure that I make the correct choices now, before I buy any equipment, to allow for easy extensibility.

  • What size system are you planning on at first, and what would you like to scale to and add in the meantime? Nov 6 '17 at 17:28
  • I want to start with a 100W solar panel. I then want to add on a wind turbine. My ultimate goal is to continue to add more battery and generation till I can power my whole house. Start small but end up big. Nov 6 '17 at 18:08

If you have a single-string MPPT charge controller, then you should not even think of trying to combine your two generators (i.e. PV array and wind turbine) onto a single input and feeding that in.

The voltage produced by most simple (i.e. cheap/beginner/entry-level/DIY) wind turbines varies with wind speed. If you combine this in series with your PV array you could easily exceed the maximum input voltage of your charge controller and pop it. If you combine it in parallel then the voltages will always be different and you'll end up with seriously reduced combined output (although no damage to your panels and not much risk of damage to your turbine).

One way to improve this is to get a multi-string MPPT charge controller. Feed in your PV array on one string and your wind turbine on the other string. The two are isolated from (and hence would not interfere with) each other. You would need to size the controller for the maximum possible voltage and current that either generator could possibly produce, or risk it going pop. The output from each generator would get optimised independently before being fed into the batteries.

As good as a multi-string MPPT charge controller may be, you need to keep in mind that most of them are designed to accept the output from PV arrays. One good thing about solar panels is that (once the batteries are full) the charge controller can simply stop accepting power from them and nothing will happen to the panels (they will not be damaged). The same cannot be said about wind turbines.

Cheap/beginner/entry-level/DIY turbines can't just turn themselves off when their output is no longer needed. The power has to go somewhere or it can result in the turbine itself being damaged (by increased angular velocities). Thus most turbine charge controllers have a shunt — an alternate circuit (e.g. a hot water heater) that surplus power can be diverted to (dumped into) when the batteries are full.

More expensive/smarter wind turbines have electronics that monitor the current flow and adjust blade angles (or perform other tricks) so as to reduce power generation when the energy is not needed.

Although some hybrid solar/wind charge controllers do exist, there aren't many of them, they are more expensive, and they will not scale with your needs (unless you spend several thousand dollars and ridiculously over-spec your controller on Day 1).

In my opinion, you are better off keeping the two systems distinct. Have a dedicated wind controller (with shunt) for your turbine, and a dedicated PV controller (with no shunt) for your array. Feed them into different batteries/circuits/loads, and if one system fails at least you have the other one as a backup.

What you want to do is easy if you have $20-30,000 to spend and never plan on upgrading. It's much harder to do on a small budget, very difficult to scale in any meaningful way, and you really need to appreciate that wind power and solar power are two entirely different beasts that need to be handled and tamed in different ways.

  • This is the right answer, but takes a while to get there -- could likely be shortened, and a few headings/bullets would be helpful. Probably worth noting that wind turbines for a single home very rarely make economic sense.
    – LShaver
    Nov 8 '17 at 11:50
  • Thank you for the detailed response. I will follow your advice with the two controllers. But now I have the same question with regards to two controllers powering the same battery pack? Can two controllers feed the same battery pack and what should be taken into account. I can create a new question for that. Nov 8 '17 at 15:15
  • As LShaver said, wind turbines rarely make economic sense in a domestic context. I'd suggest thoroughly and carefully investigating the wind energy potential for your site, and see if you can afford a large enough turbine to make it financially viable. If not, then you can remove wind from consideration and your question becomes moot — you'll just be left with a straight-forward solar setup.
    – Tim
    Nov 9 '17 at 9:53

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