Multiple Xantrex C40's in Series

[(unknown)]

Hi,

 I am currently trying to make a setup for 4 Wind Turbines, what i plan is to have 4 Wind Turbines producing D.C. connected in series, all 4 turbines produce between 48V and 56V and produce between 0A and 26A. I would like to connect all three turbines to a SMA Windy Boy inverter since the inverter works on voltages between 180V and 600V having 4 turbines in series should make the volatge high enough, the problem occurs in the situation when the inverter is disconnected due to a power failure, when this happens the turbines will continue to produce D.C. electric and i need a dumpload to get rid of this, therefore my idea was to connect 4 xantrex in series with each other each with there own dumpload and then connect them in parrallel with the inverter and the way i see it the voltage across each C40 should be the eqivalent of 1/4 of the total volatage going into the inverter. Will C40's work in a setup like this ? I have tried contacting xantrex 1 week ago but have had no reply as of yet hope you can understand what i am trying to do, please say if you cant understand my setup.

Thanks for any help,

Orrin

[Flux]

sounds like a recipe for disaster all round.

Flux

[drdongle]

What if one turbine fails?

[powerbuoy]

First of all, I can see that the Xantrex people will be all excited about your mail since you're telling them that you are using a single inverter (built by their main competitor SMA) for a grid connection and four of theirs for dump load purposes ... that might be the reason for the slow response. That's like riding a Mercedes to a BMW dealer, asking them if they see a problem if you'd use four of their BMWs for trash hauling ... :-)))

I do not know if every inverter has the excact same input impedance,... (I am by all means no expert in inverter circuitry, except for an understanding of the basics), however if they have differences in their input impedance then there will be different voltages across each one of them.

I trust by power failure, you mean "grid loss" , does not the sunnyboy have a provision (relay out put for that condition)? (to switch over to a load bank?)

If you need a dumpload then I suggest something simpler and less expensive E.G. resistors ...

Powerbuoy

[altosack]

Umm, first of all, the Windy Boys I'm aware of can't handle this sort of power (56V x 26A x 4 = 5.8 kW).

Second, diversion controllers only work with a battery system. Without a battery, the voltage will not be stable enough for the PWM (it doesn't test the voltage instantly, in fact, many users have complained when using the Xantrex as a diversion controller because of this reason; MorningStar's TriStars are better in this respect).

Third, if you could connect the controllers in series (please, please, do not try this), this would mean that only one would be able to be grounded, and you would be left high and dry in electrical storms.

For this type of thing you could use a FlexCharge NC25A, which is not a PWM controller, but a 0%/100% (slam/bang) relay controller. Although you can only get nominal 12V/24V/48V systems, it's quite easy to attach the sensor to only 2/4/8 6V batteries in a string (if this is what you have) or use a resistor divider to adjust the input voltage into its range. You then need suitable relays rated for the voltage (and current !) you need to divert.

However, my advice from what you have written (please do not take this the wrong way; I really have your best interest at heart and do not mean to be condescending) is to take yourself to a local renewable energy dealer and follow their advice.

Best of Luck,

Dave

[(unknown)]

Hi,

Thank you all for your quick responses. First I would like to tell you all that I am quite new to all of this as you will probably have realised, and my original idea did seem a bit to good to be true. Therefore could anyone explain to me the best way they can think of connecting 4 Wind Turbines that have 48V to 56V and 0A to 26A as D.C. outputs to a grid tie inverter i would preferably like to use the SMA Windy Boy 3000 (i.e. 3000W maximum input). The problems as I see it are as follows:

1. ) During power failure (grid loss) all the power produced by the turbines needs to be dumped into heating element or something similar to waste the energy produced.
   
2. ) As altosack pointed out above the turbines when running at maximum power produce 5.8kW and this is too much for the inverter and so all the extra power needs to be dumped, you may ask why do this, the answer is that it makes it more cost efficient for my particular setup as 95% of the time the total output will be below 3000W and therefore why pay twice as much for that extra 5% but I am sure most of you will know this already. Obviously if it is impossible or extremely expensive to get around this problem i might as well just buy a the bigger inverter.
   
   

Any ideas on how to get around these problems would be extremely welcome even if it is using completely different components to what I originally planned to use.

I would like to explain how I arrived at my original idea, because in my first post, as I can now see it looks like I have just thought of connecting many parts that look as if they will do the job and not really knowing. The reason is that I did contact the supplier of the Wind Turbines i am planning to get and they told me the best setup they can recommend is having 4 individual setups that are as follows a turbine connected to a Sunny Boy LV (LV stands for Low Voltage and this unit operates between 48V and 60V perfect for the turbines) and then connecting a Xantrex C40 in parallel with the inverter in so that during grid loss it will waste all the energy into a dump load, so you can see why I thought that maybe adding more turbines in series and more C40's in series and using a higher voltage Windy Boy would work. My reasoning for not wanting to make 4 individual systems as they recommend is because of the huge cost of buying the inverters.

Thanks for any help,

Orrin

[TAH]

What kind of windmills are these? If you want the cheapest way to tie four together maybe you could set up a 48 volt battery bank with 4 car batteries and feed the GTI off off of the batteries. All four mills could be tied to the batteries through blocking diodes. The GTI should shut down when the voltage drops. You would need to use some overvoltage setup on the batteries to keep them from blowing up but theat could be done cheaply with a cheap dump load controller.

[dinges]

May I ask what the motivation is for this entire project?

As it looks to me now, you're trying to get rich selling power to the power company. Nowhere I see anything about using the windpower for your own use.

Make a quick investment analysis of it, and it should quickly become obvious that this is negative NPV project (i.e. you lose money, even in the long term).

No doubt you have good reasons for this large project (4 windmills with towers, grid-tied inverters, several inverters as dumploads), would you care to tell us which they are?

[boB]

>>the way i see it the voltage across each C40 should be the eqivalent of 1/4 of the >>total volatage going into the inverter

What do yo mean, connect them in series but each have their own dump load?

Don't quite understand that.

As for adding C40s in series to gain higher voltage, that won't work because

each C40 operates independently of each other on when they switch so the voltage

will not be divided up evenly.  At any one moment, one C40 could be on (input

directly to output) and another C40 could be off (input disconnected from

its output).  C40s operate at a few hundred Hz each I seem to remember.

boB

[(unknown)]

Hi,

I have been looking around on more posts on the site and have found that quite a few people are attempting to do similar things as I am which is really to have a charge controller capable of taking either very high voltages or very high currents.

I will try to explain a little more about what I am attempting to do since it looks like I am trying to sell electricity to the electric board. My dad owns a commercial building which uses about 200,000 units per year and by having 3 or 4 turbines connected in to the mains I hope to slightly reduce the power taken from the grid. The best bit is that my dad business uses more electricity than the turbines can produce therefore i should never actually be exporting to the grid. So basically the way i see it is that currently my dad pays 10p per unit and since I am paying for the turbines I am going to charge him for all the power the turbines produce plus as I live in the UK i get ROC's which basically means I get an extra 3p per unit because i am producing green electric, all in all i get 13p per unit and if i get an average windspeed of about 10mph i should breakeven in 6 years (approx)which i did not think was to bad, of course this depends upon the system not getting stupidly expensive which it sounds like it might do !!.

Some one mentioned using batteries so i have thought of another circuit that might work since my first one clearly would not work it is as follows:

Connect 4 turbines, 3 C40's a 48V Battery and a SMA Sunny Boy 1100 LV all in parallel, the idea was that the turbines would constantly charge the battery/batteries and the inverter would constantly drain the battery/batteries and when the batteries became full the C40's would kick in one by one to divert the power into a dumpload. I also found on this site a similar setup to what I have described:

http://www.oksolar.com/wind/

except they picture only one turbine and only one C40, do C40's work in parallel? I read another post on this site which seemed to conclude that they will but it is not a good idea, does anyone know of a Diversion Controller than can handle 48V to 56V and 0A to 104A? does my idea of using a battery as kind of like a storage cylinder so that the inverter will have more of a constant load seem a good idea? Has anyone got a working setup similar to this I would be very interested to hear from someone that has a definate working solution.

Also the planning application for my turbines passed today therefore I now need to seriously look into getting a viable working solution to this.

[craig110]

I wouldn't want to make use of charging batteries as a dump-load for the simple reason that they can fill up and when they fill up, you're back to essentially not having a dump load.  Think about a multiple-hour grid power outage caused by a pretty strong storm.  At the same time that the grid is out, the turbines would be producing their peak power.  You might have several problems in this situation:

1. - Even if your batteries were normally maintained at a nearly-discharged state (which would shorten their lifespan by quite a bit thus raising your maintenance costs), how long would it take to charge them in high winds?
   
2. - If your batteries were normally kept mostly charged to maximizing their lifespan, the amount of time during high-wind power until they were entirely charged might be very brief.
   
3. - Each battery type has a maximum recommended charging rate.  You might have to have enough battery sets in parallel so that their aggregate maximum charging rate is greater than the high-wind turbine output or else the battery life could be cut short.
   
   

All in all, using batteries like this just feels like a problem (or several) waiting to happen.  How about just connecting a sufficiently large DC heating element to your turbines via an AC relay that closes (i.e. connects the heating element) when the grid's power turns off?  In addition to being a simple, low-cost, and unfillable dump load, with the number of watts you're considering producing the energy cost of energizing the relay nearly 7x24 (to keep the heating element disconnected) would be pretty low.  Frankly, it might even be lower than the total power consumed by a handful of C40s plus the slow power leakage out of a battery bank.

Craig

[Countryboy]

Why does the building use 200,000 Kwh a year?  How is the power consumed?

It is approximately 5 times easier to reduce consumption as opposed to making the energy.

See if you can work out a deal with your Dad where you are a consultant.  You do a walk-through of the facility, and you find ways of reducing his consumption.  See what kind of deal he will pay you, for every Kwh you show him how to save.  See if he will pay you half of his savings, and apply the other half towards energy savings features.  (As that fund grows, you can always apply that money towards solar panels or a wind turbine.)

Not using a Kwh of electric is equal to producing a Kwh.  Yet, finding ways of reducing use is 5 times easier than producing that same amount.

There are undoubtedly a ton of ways to cut electric costs.  Do a walk-through of the facility, and see how many incandescent lights can be replaced with flourescents.  Look at better insulation for exterior walls and rooftop.  See if you can put different portions of the building on timers, which completely shut off electric during hours no one is in those parts of the building.  How many people leave a computer turned on, or leave printers, etc turned on overnight?  Look at options for solar hot water heat on the rooftop.  Look at options for inground tubes that draw cool air from the ground.  (Heck, use the cool air in underground sewer lines.  Blow that cool air thru a radiator and back into the sewer so you don't have to smell it.  Use the cooled radiator to cool the building.)

There are a ton of ways to cut energy use.  After you have reduced unnecessary consumption, then look at ways of generating your own electric.

[TAH]

The batteries would not be a diversion load they would be a buffer in the feed to the GTI. There would be no need for any other inverter, the load diversion would only need a simple device like the one here http://www.hydrogenappliances.com/batteryregulator.html

This could be on one of the batteries on the bank and have it run a larger relay that pulls in a big enough load. This would keep the batteries from overcharging and they would never get drained because the GTI would cut out. Standard car batteries would probably work the best in this kind of setup.