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

owen_aowen_a Registered Users Posts: 20 ✭✭
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.

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.

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?).

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.

Thanks,
Owen.

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,656 ✭✭✭✭✭
    owen_a wrote: »

    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.

    Owen, These cheap small grid tie inverters are difficult to recommend any type of use, including that for which they are intended. They don't carry a UL or ETL rating and if the power company knows you are using one they can turn off your power! If you have a digital meter you may also be charged for any electric you are trying to back feed into the grid. If your insurance company knows about the inverter, well who knows... but if you intend to use one you might go ahead and drop your insurance, since I'm sure wiring a non-code compliant energy source into your wiring will make your insurance null and void...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • owen_aowen_a Registered Users Posts: 20 ✭✭
    BB. wrote: »
    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.

    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.
    BB. wrote: »
    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 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.

    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)?

    Thanks,
    Owen.
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    One of the other characteristics of a versatile charge controller for wind operation (such as the Midnite Solar classics) is that instead of doing a sweep to find the tentative maximum power point (which would have to be slow enough for the speed of the turbine to stabilize at each new load step) it can measure the no-load voltage briefly (getting in effect the turbine speed, since the voltage output is unregulated) and then setting the current to a value from a table of voltage and current values customized to a particular wind turbine's performance.
    The safety load (protecting against overspeed and over voltage) is a separate unit in that case, namely the Midnite Solar Clipper.
    SMA SB 3000, old BP panels.
  • MGarMGar Registered Users Posts: 14 ✭✭
    owen_a wrote: »
    I have a 300W 24VDC Wind Turbine
    I would only be concerned with the wind turbine over-volting-reving.. All you need is a zener diode and a Solid State Relay or Big mosfet. Just make sure to have at lest 2 times the duty, like a 40 amp DC-DC (3-32v 5-220v). it should be ~>$10.
    When the voltage rise's to the zener voltage plus ~3 volts it will short out the + and - of your wind turbine, you also should have or build a resistor if needed (output side) 1 ohm?.
    The Relay should take about 2.5 mA. to turn on.~3 volts. 5/2000=.0025 but you really should measure one.
    should work with a 2k resistor (minus 5 volts from your choice) and your max voltage (30 volt?) 5 watt zener, and put a protection zener from + to - on the input like any thing >5v to 24v.
    Maybe this is not 100% correct but here is is: The 2K resistor is to protect the zener diodes it hooks up to the positive wire and then the zener is in series to the input positive +
    .
    A protection zener diode hooks up on the input side from + to - if you max voltage is lower than 32 volts you don't need it. Don't forget the 2k resistor limits all current of zeners.
    So if you want to short at ~32 volts with a 2k 1 watt (or greater if volts are more than 40) resister (it needs 5 volts for 2.5 mA plus the 3 volts=8 ) a (32-8 ) 24 volt 5 watt zener diode should turn on the SSR at ~32 volts, hope i got that right...
    Maybe there is a simpler way?
  • owen_aowen_a Registered Users Posts: 20 ✭✭
    Hi,

    I'm just reviving this thread again since I'm looking into improving my current system. If I understand Bill correctly, If I keep the current TS-MPPT-60 as is, but have a Dump Load controller connected to my battery bank, and the output going to some sort of load, then wouldn't the batteries be always charging? What if the dump load is let's say 500Watts, and my solar array is charging at 200Watts because it's a very dull day, would the Dump Load controller compensate and only dump less than 200Watts into the "load" so that the batteries can charge fully again?

    Thanks,
    Owen
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,032 ✭✭✭✭✭
    It will shunt current to the load when the V set-point voltage is reached. Read the manual for both the mppt and the electronics you will use as a dump load controller. When set-up correctly you will not over charge your battery bank. You really do not want to be over cycling batteries in a 24 hour period either. Absorb charge them once a day max and they will last a long time.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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