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222
General Discussion / Re: How is everyone surviving the cold and snow?
Last post by MaryB -
The short days cut my solar output, but I get gain from snow reflection... not enough to cancel the short days but it helps. Dec thru Feb I see a reduction in output. With my panels at 45 degrees snow tends to slide off. Yep I am at 44.5 north!
223
General Discussion / Re: How is everyone surviving the cold and snow?
Last post by MagnetJuice -
I am fortunate to live where I live. The coldest I’ve seen this winter is -3C. We get a lot of rain here through the winter but to me that’s better than the cold and freezing weather. I hope those living in the southeast US make it through OK. That looks like a really nasty storm.

Spar, for those that have panels close to the ground, it should not be too difficult to build a rack that would pivot, then use an actuator to flip the panels down 30 or 35 degrees. They could be flipped when there is a lot of snow in the way, then moved back after the storm. BigRock and kitestrings have used actuators successfully with their wind turbines.

Stay warm guys.

Ed
225
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: bigrockcandymountain – on
What if all you did was add a very large capacitor (or a few of them) with a resistor in series to limit charge /discharge amps between positive and negative between the ssr and the micro inverter? Would it smooth the dc power enough that the micro would be happy? Would it store enough that when the mppt swept up it would drop a bit of amps and mimic a solar panel?

Funny you mentioned the SSR just when I was getting frustrated with designing my circuit with a MOSFET, and tonight I've been replacing it with a SSR.

I think I have the microcontroller signals figured out.  What's really bothering me now is that I've made some assumption about the inverter and I don't like the way things go bad if I am wrong.  I've been using Falstad's site to simulate this, and it suggests I will be blasting the 0.5 ohm power resistor with brief bursts of 90 amps.   Probably just something I have simulated wrong, but...

To your suggestion BRCM, yup, a big capacitor soaks up a lot of nuisance noise.  You just have to make sure it doesn't drown out the signal you want to measure.  Circuits that combine resistors and capacitors have a "time constant".  If the constant is long (in the electronics world 1 millisecond is long) then the time for the capacitor to charge up is longer than the time for a 1 kiloHertz signal to arrive, and you probably won't measure the signal.  On the other hand, if the capacitor is too small or ineffective, then the microcontroller is measuring pulses and it may pick up the pulse on the Hi during one reading, and on the Lo on the next.  From the microcontroller's perspective, the signal went from on to off, and in a sense, it would be right.  But in another sense it failed to detect what the power resistors are doing.  It missed the next Hi peak which has a different voltage than the last Hi peak, and that was the information it's looking for.  So there's a balance, when Goldilocks finds the right oatmeal.

Quote from: bigrockcandymountain – on
It sounds like a thread hijack when I read through it, but it kind of applies to sparweb's setup too.

Nah, you're forgiven
226
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: bigrockcandymountain – on
...my diversion load is a 500hz 12v signal that goes to a ssr and dumps the 48v battery voltage through an approx 10ohm resistor (water heater element) I assume the 48v comes out of the ssr at 500hz, not exactly as dc.

48v/10 ohms = 4.8 Amps
60v/10 ohms = 6.0 Amps

Hmm surely you'd dump more than that?  I think your WT is bigger than mine is, and I need a 2kW diversion load (and I admit mine turns out to be only 1.8kW).  It may not matter in your case if you're using your batteries most of the time.
228
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: MaryB – on
Feed it thru a rectifier and monitor the DC current via your micro... a full wave bridge with electrolytic has 1.4 times the voltage output so some math involved...

For now, I'm monitoring DC current, which is pulsed.  Where I tap off the power resistors with a voltage divider determines the scaling factor I need to satisfy the microcontroller's ADC input.  I figured out that a 1 to 10 uF capacitor is all I need, and doesn't have too slow a time constant for these devices.
229
General Discussion / Re: How is everyone surviving the cold and snow?
Last post by SparWeb -
When the Germans "went solar", they soon encountered the winter doldrums which get cold and dark, and then sometimes even the wind stops...  ...so they came up with a word for it:  Dunkelflaute

There's always a long Dunkelflaute here, where we get virtually no sun or wind for about a week.  Solar panels covered in snow makes it worse, but there's not even any point brushing them off.  Last December, about Christmas-time, the temps were -20C for a week.

In early January both the weather and I perked up, and I got in a lot of skiing.  Since then, it warmed up, melted the good snow, and turned the rest into ice. So much for skiing around the house.
231
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by bigrockcandymountain -
I looked at your circuit diagram and read the explaination, and I'm trying to picture exactly how it would all work and i think i see some light.  I have "Electronics for Dummies" open in my lap right now.  That helps too. 

I have something I'm wondering about and I'm sure someone will explain to me why it won't work. 


In my case, my diversion load is a 500hz 12v signal that goes to a ssr and dumps the 48v battery voltage through an approx 10ohm resistor (water heater element) I assume the 48v comes out of the ssr at 500hz, not exactly as dc.

If I swapped the water heater element for a grid tied micro inverter it would get fed messy 500hz and would blow something up likely. 

What if all you did was add a very large capacitor (or a few of them) with a resistor in series to limit charge /discharge amps between positive and negative between the ssr and the micro inverter? Would it smooth the dc power enough that the micro would be happy? Would it store enough that when the mppt swept up it would drop a bit of amps and mimic a solar panel?

I get the feeling the magic smoke would come out somewhere, and i don't even have the grid here, so it's all academic.  I just can't picture in my head what would happen, and i was hoping to learn something by asking.

It sounds like a thread hijack when I read through it, but it kind of applies to sparweb's setup too. 

232
General Discussion / How is everyone surviving the cold and snow?
Last post by MaryB -
Second morning of -20f, thankfully the wind died down so the house is warmer! Yesterday's high temp was -9f!

Seems like more normal weather patterns are back, Minnesota usually sees a week or two of deep cold in January/early February then spring starts to creep in...

 
235
Forum News & Announcements / Re: Welcome to FieldlinesForum! Your new Community.
Last post by Xeonpony -
Glad to see the name resurrected, but I still lament of all the lost members from old that shall never be seen again! Hopefully some how you can get the data from the old forum

When I have more time I'll help fill a few sections up, my ewe lambed so have very cute pictures for the farming section.
236
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by MaryB -
Quote from: SparWeb – on
Quote from: Bruce S – on
This looks to be a nice setup, like BRCM I'm curious where you go with these.

Well, slowly, is where I'm going.  Diving into the circuits, I'm afraid of how choppy the signals are to monitor current.  I'm adding various things to smooth it out, so that I don't need a complicated program in the software.

Feed it thru a rectifier and monitor the DC current via your micro... a full wave bridge with electrolytic has 1.4 times the voltage output so some math involved...
238
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by Bruce S -
Quote from: SparWeb – on
At this point, the ideas I'm sharing are partly based on a device I developed with Glen Hurd (aka GHURD) from the old Fieldlines board.  He deserves credit for doing a lot of development work to make a similar device work, which I built and used for years.  It was called an "opportunity diversion load timer", which "sniffed" when the charge controller was running the diversion load, and switched on some kind of DC or AC load that could be used instead.  While the AC or DC load was running, the batteries were being drained thus the need for a diversion load by the charge controller was relieved.  So instead of running a heater in my garage, a heater kept water for our horses thawed in the winter.  This saved me a lot of money and this device paid for itself quickly.

I just wanted to pause and give a shout out to GHURD, wherever you are.  Your ideas live on and I'm still using them.
SparWeb;
He's still kicking. I have a few conversations with him and Tom W, from time to time.
I still have the ones I purchased from him too. I'm currently redoing my little 200Watt solar setup to try out a smallish sand heater setup for our basement media/playroom.
 This looks to be a nice setup, like BRCM I'm curious where you go with these.

Cheers
Bruce S
239
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
A bit more explanation of how the circuit works:
  • Detects when the Charge Controller activates the diversion load resistors by sensing voltage, then closing the relay contacts. Otherwise, this device is dormant and the relay is Open.
  • Once triggered, the device closes the relay, and stays active for a pre-set time, then shuts off.  If the Charge controller is still running power through the diversion resistors, then the device triggers again for another cycle.  The activity cycle can be adjusted.  Let's assume between 15 minutes and 1 hour, for now.
  • The relay only supplies + battery voltage to the DC positive terminal of the microinverter. 
  • The DC negative terminal of the microinverter is grounded through a pair of power resistors, totaling 4.5 Ohms.
  • Even so, the microinverter should begin to activate as soon as the relay closes.  At first the microinverters will not pass any DC current, just measure DC voltage, so it won't see a voltage drop across the power resistors, yet.
  • Microinverters always have a 1- or 5-minute delay before they actually connect to the AC, so the device will just wait in the meantime.
  • While waiting, the gate driver is already active.  What it's doing is cycling the FET on and off across the 4-Ohm power resistor.  I'll explain the reason for this later.
  • Once the Microinverter comes on-line, it will simultaneously connect to DC, admit current through the DC lines, connect the AC output lines, and  start seeking the MPPT point.  Since it's pulling DC through some power resistors, it will detect a voltage drop.
    This is intended because solar panels have a strong voltage drop while current increases.
  • Unfortunately, if only power resistors were used, the MPPT algorithm in the microinverter would measure higher power at ever-increasing current.   Is 10 Amps enough? 10 Amps X 40V is 400W, great.  Is 11 Amps enough? 11 Amps X 39V is 430W, better... and it keeps doing this, until it exceeds its own power rating (and/or catches fire).  Microinverters are designed for solar panels only, and the "knee" of the curve keeps them safe.  I don't believe that the microinverter will self-limit (but maybe it can).
  • To keep the microinverter from blowing itself up, I've introduced a FET shorting across the 4 Ohm resistor.  By doing this, the voltage drop can be controlled and simulated, like a PV panel was there.
What does the FET do?
  • When the FET is on, the current is basically shorted to ground, which is like the typical use of most N-channel MOSFET controls for motors and heaters.  The microinverter will see lower resistance and current can increase.  Left to its own, its MPPT will seek more current to increase power output.  This simulates being on the right side of the knee of the PV Panel I-V curve, increasing current and voltage will drop slightly.
  • When the FET is off, the current admitted by the microinverter is subject to a lot of voltage drop, so much that there is a strong voltage drop.   Now the MPPT algorithm will measure lower voltage and determine that the input power is dropping, thus the current is too high.  This simulates being to the left the knee of the PV Panel I-V curve, where voltage has dropped due to more current.

This the Arduino needs to control the gate of the FET seeking a balance between current and voltage.  This will need tuning so that the characteristics of the microinverter don't set up a "fight" between the microinverter's MPPT algorithm and the Aurduino program I write to manage the same thing.
240
Inverters & Grid Integration / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
At this point, the ideas I'm sharing are partly based on a device I developed with Glen Hurd (aka GHURD) from the old Fieldlines board.  He deserves credit for doing a lot of development work to make a similar device work, which I built and used for years.  It was called an "opportunity diversion load timer", which "sniffed" when the charge controller was running the diversion load, and switched on some kind of DC or AC load that could be used instead.  While the AC or DC load was running, the batteries were being drained thus the need for a diversion load by the charge controller was relieved.  So instead of running a heater in my garage, a heater kept water for our horses thawed in the winter.  This saved me a lot of money and this device paid for itself quickly.

I just wanted to pause and give a shout out to GHURD, wherever you are.  Your ideas live on and I'm still using them.