Dump Load options for Morningstar TS-MPPT-60? With Wind Turbine & Solar Panel

owen_a wrote: »

Hi,

I have a Morningstar Tri-Star MPPT 60A charge controller to charge my battery up. My idea was to use an automatic diversion controller, however I liked the Ethernet feature on the tri-star MPPT-60A, so I went ahead and bought this controller..

This is my problem. I have a 300W 24VDC Wind Turbine - Yes that's right, DC, not AC. I also have a 100W solar panel that is 12VDC. I'm waiting to get four 300W solar panels so I can wire them up in a Series/Parallel configuration to get my ~24VDC.

You can get a "cheap" PWM type charge controller with Dump Load operating mode. Set your MPPT controller to charge at ~14.7 volts. And the dump controller to "turn on" at ~15.0 volts.

For most people, they simply do not get very much energy from their wind turbine systems (between tower too short, units not meeting spec., and breaking after a few months or year out in the weather).

I have a 400W Grid-Tie inverter, and I can upgrade based on my "future" system so it can handle about 2kW. I want to have it so once the battery is charged, it will divert the solar array/panel and Wind Turbine to the Grid-Tie inverter so I can benefit on lower mains supply power consumption. The problem is, I'm not sure if this controller can handle diversion, which to my knowledge, it does not.

You connect the GT Inverter's DC input to a Dump Controller. That will work. However, it may not be unreliable (i.e., utility power goes down, your dump controller cannot dump power to dead power mains). Also, GT inverters typically wait 5 minutes of good AC and DC power to "turn on"--So, you are sort of unregulated DC power for ~5 minutes.

In general, a GT inverter is not a "reliable and safe" dump load. So, you should have a second Dump system as backup.

And specifically, I have seen few UL/NRTL Listed 400 Watt GT inverters--And many are of questionable reliability and safety.

Second, most utilities (and building departments) require a permitted GT power system and Net Metering agreement with the Utility to legally sell back power.

One solution is to manually change it over via a rotary switch, however this will require manual maintenance, something that I'm trying to avoid to benefit lower power consumption on the house when I'm away from home, etc.

Another solution is to build a circuit that monitors the battery voltage, and if it's higher than 12.7V, then use a mechanical relay to divert the Solar/Wind turbine to the grid tie inverter , essentially connecting the Solar Array and Wind Turbine in parallel (Is it ok to do this?).

Yep, possible.
Legal? Perhaps not.
Safe? Perhaps not.

I'm open to suggestions and I'm really looking forward to getting this resolved. I don't mind buying a hybrid controller just as long as it's a reasonable price and nothing too expensive.

Hybrid inverters are not cheap. And many times, by the time you buy Listed Equipment and Building/Utility permits/insurance, small Net Metering systems may not make much sense.

-Bill

owen_a wrote: »

I'm not sure what you mean by this in terms of wiring them together. Do you mean feeding the MPPT controller through the cheap PWM one? I'm not sure that will work since it requires a battery to operate the controller, which is how it charges (through the same wires) anyway? Also, there is no voltage on the PWM controller on the input side, so the MPPT controller wouldn't be able to get powered.

I think I might manually wire it for switches, so I manually switch the solar array / wind turbine to the dump load. And when I know I'll be using the batteries, switch them back.

You connect the output of the pv MPPT controller to the battery bank +/- terminals. Connect the Wind turbine to the +/- battery terminals (no charge controller), and connect the Dump Load controller input to the +/- battery terminals and the output of the dump controller to the Resistor Bank connections.

The PV MPPT controller works as normal. The wind turbine dumps all available current into the battery bank (unregulated). And if the battery bank is fully charged (~15 volts), then the dump controller turns on and starts discharging the battery bank to the resistor load (dump load, shunt load, or diversion load--all mean the same thing).

I live in the UK, and my wind turbine isn't even higher than the house roof. It's mounted on the side of the garage, and has houses surrounding it, yet when the wind blows, that generates a good 300W+, even in 15-20MPH winds.

Wow--That is really good. Not many people have that kind of performance.

Question...

Since I have this controller, it states "Hybrid (PV + Secondary energy source)" - top left icon under where it says "TriStar MPPT" with a wind turbinem plug and the sun.

I'm presuming that I can connect my 24VDC wind turbine to the charge controller in parallel with my solar panel? And the controller should regulate it to 13-14V (to whatever my absorption/float voltage are set to)?

OK--This gets a bit complicated. MPPT controllers automatically (or through a look up table) set the "optimum voltage" (Voltage Maximum Power) for the device supplying the energy. For Solar panels that is Vmp... For Alternators/generators, it is based on the RPM, voltage, and current state. For example a wind turbine may output 4 amps at 12 volts and 3 amps at 24 volts--48 watts vs 72 watts--The Alternator is able to send more Power (watts) at higher voltage/lower current/higher RPM (just a made up example).

So, you can use a MPPT controller between the PV array and the Battery Bank (good reasons to use a more expensive MPPT controller). And you can use a second MPPT controller between the wind turbine alternator (and rectifier) and the battery bank to "optimize" the harvest energy from the turbine (a good MPPT controller may increase your harvest by 2-3x over a direct Alternator -> battery bank setup). You should not (normally) connect a PV array and Wind turbine (rectifier) output together in parallel--The MPPT controller will not usually give you an optimum output (Vmp for the solar panels will probably be different than Vmp for the alternator).

HOWEVER--You can have other issues. Horizontal Axis Wind Turbine (HAWT) need the load of the alternator+battery bank to keep from over speeding (a HAWT will over speed in high winds with no alternator loading and can self distruct). So, the MPPT controller cannot regulate (turn of battery current) for a HAWT as the turbine can over speed with no loads.

But there are MPPT controllers designed to manage wind turbines directly (dump excess current to a resistor bank, shunt the turbine output into a dead short, etc.). And turbines can furl, feather, rpm limit too...

So, you need to look at the wind+charger+battery bank+loads as an entire system and make sure that all is designed to work well together.

-Bill