grid tie inverter question

Windy

Hi guys, found out that direct drive turbines are the way to go, no more gear box problems.
But I see they are rated at lower amps due to low rpm, so the question is what is the grid tie inverter puts in the grid : amps or watts?

Cariboocoot

Re: grid tie inverter question

Both, because it's power and power is Watts and Watts is Amps * Volts.

But it isn't that simple.

If you are trying to power a GTI such as the Windy Boy the turbine's output has to be in the Voltage range that the inverter requires. The output Voltage will be fixed by the utility grid (and must be in the acceptable range for the inverter). At that point the inverter pushes current to the grid @ that set Voltage.

Windy

Re: grid tie inverter question

This coreless is 5kw rated at 380v 8,5A 5000w
If here the grid is 120v should I find a 120v model? Direct drive generators are the bigger the more volts, u cant find a 5kw under 380v

Cariboocoot

Re: grid tie inverter question

This spec sheet on SMA's Windy Boy may help explain it:
http://www.windandsun.co.uk/media/171083/Windy-Boy-3300-Data-Sheet.pdf

Unfortunately it appears SMA has discontinued their Windy Boy turbine-driven GTI's.

Windy

Re: grid tie inverter question

I was looking at Aurora 6000 which is great too, but my question is Whats better for on grid tie: low amps more volt or more amps low volts mmre watts?

BB.

Re: grid tie inverter question

I am not sure I understand your question...

Think of the GTI as an "automatic transmission" between the Turbine and the Grid... Within the ability of the GT Inverter, it will run the turbine at optimum RPM/Torque and output "Wattage" (power) to the grid.

As Marc types Power=Volts*Amps.... So if the grid voltage is ~212 Volts, the current will rise to transfer the A,BCD amount of watts from the turbine. if the grid voltage is 264 VAC, then the current will be reduced... The Utility meter will still logs A,BCD Watts regardless of the mix of grid voltage/current (power meter, not Amp*Hour meters).

Similar on the Wind turbine (or solar panel side). Maximum Power Point Tracking (MPPT) the GT inverter input will adjust current/voltage to find Pmax (or you program the RPM/Power curve for the Wind Turbine) into your GTI MPPT unit... And it will "shift gears" to get the optimum power out of your turbine (and, hopefully, shut the turbine down if too much wind or other failures).

-Bill

mike95490

Re: grid tie inverter question

Are these turbines producing poly-phase AC, rectified AC-DC, or pure DC ? Then you know what sort of GT inverter to hook onto it.

But the inverter needs some smarts to be able to "brake" or halt the turbine in case the grid goes down, or some other reason, so the turbine does not overspeed and grenade itself. That's going to need an "active brake" so when things are normal, the grid power disengages the brakes. (like air brakes on a truck, positive air pressure keeps the brakes off.)

Cariboocoot

Re: grid tie inverter question

In general terms it is better to have the power as more Voltage and less Amps because that combination suffers less loss in transmission: the higher Voltage better overcomes wiring resistance and the lower current means less heat production.

Windy

Re: grid tie inverter question

Wow guys, im learning so much from you, its great. What do you think about the direct drive generators, coreless and no gear box? They run at lower rpm , right? So for a big 5kw turbine is better to get a 5 blade instead of 3 ?

Cariboocoot

Re: grid tie inverter question

Asking opinions on wind turbines around here .... I think the phrase is "mechanica non grata".

The design per se is not as much of an issue as the result; is the particular unit built well enough to do the job? You may notice that the huge commercial units turn slowly; low RPM's = less vibration problems but more torque problems. Gearing is mass that uses power which has to come from the same wind that you're trying to turn into electricity so technically they are less efficient. Get the scale right and that efficiency drop becomes immaterial due to the benefits. Get the quality wrong and it's just another big piece of junk up a pole.

More blades will start a turbine in lower speed winds and in theory pick up more power. The down side is that they suffer in high speed winds for the same reason. Plus they have more rotating mass. It's never as simple as "this design is best". And engineers notoriously don't like to give direct answers.

If you want to learn from the best about wind turbines check out Hugh Piggott's site: http://www.scoraigwind.com/

It's curious that homemade small turbines are usually better than commercial ones, but homemade PV's are usually worse (and more expensive).

BB.

Re: grid tie inverter question

Gear boxes have friction/losses--So designingork a turbine that does not have have a gear box will usually be more efficient (and if the bearings are done right, should be more reliable/less maintenance).

BB. wrote: »

Add links about wind power:

Wind Power Links
www.otherpower.com (good forum for DIY Wind Power)
Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
Scoraig Wind "Recipe Book" for DYI Turbines (from Chris Olson... From his 4/11/2013 post)
www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)
Small windpower a scam ? Survey says SO
Truth About Skystream & SWWP
Windmax HY-2000 2kW Wind Turbine (apparently, some vendors don't sell spare parts--just new turbines. However, the owner, Edward has been very happy with its performance from 2010-2012--BB. 5/31/2012)
...l

-Bill

Windy

Re: grid tie inverter question

Thanks again for your info!
I saw that xantrex makes grid tie/ off grid inverters and I plan in using 6kw solar and 3kw wind but xantrex are 48v and wind turbine is 220v. Will I have to get something else than xantrex that is 220v input?
My last question is can u connect a 48v inverter input ( but outputs 220v ) with a 220v input/output inverter in the utility grid? To stack them or need to have same voltage?

mike95490

Re: grid tie inverter question

I'm not sure what you mean by "stacking inverters". the XW inverter lines are 24V and 48V, and want to see the AC side in the 240VAC 60Hz (USA, varys by country it's shipped to). You can adapt the AC2 (generator dedicated input) to a pretty wide freq range, and the unit will track it, and charge the batteries - it does not know if it's a windmill, or a genset with a bad governor.

Windy

Re: grid tie inverter question

stacking inverters i mean i want a wind turbine 3kw ( maby 5kw) and 6kw in solar panels and i also want the inverters to be flexible ( on grid but off grid switch too with batt backup).
problem is that xantrex dont make inverters bigger than 6kw and i will need like 12kw inverters and my second issue is that the xantrex is 48v input and the wind turbine is 220v input, will it work?
And my last question is how to connect 2 inverters to the same grid tie without the need of 2 meters?
Do i need 3000w pure sine wave inverters to regulate the turbines 220v into xantrex's 48v?

BB.

Re: grid tie inverter question

Lots of serious questions there:

Windy wrote: »

stacking inverters i mean i want a wind turbine 3kw ( maby 5kw) and 6kw in solar panels and i also want the inverters to be flexible ( on grid but off grid switch too with batt backup).

You are connecting GT Inverters (wind/solar) to the grid directly... And many localities use a break of 10 kW of local generation capacity as the break point between residential (utility mostly leaves you alone) and commercial (a whole bunch more rules/regulations).

Before you buy/install any equipment, make sure your utility, local code inspectors, large enough main panel/street transformer, and such will allow you to install what you want.

problem is that xantrex dont make inverters bigger than 6kw and i will need like 12kw inverters and my second issue is that the xantrex is 48v input and the wind turbine is 220v input, will it work?

Yes, I believe you can parallel several 6 kWatt XW inverters in parallel and feed them with your GT inverters.

Normally, the XW would alter the line frequency when the batteries are full to kick the GT inverters off line (when grid has failed). Your wind-turbine+wind GT must shut down the turbine when batteries are full, and/or you will need to place dump loads on your battery bank (to prevent batteries from overcharging).

And my last question is how to connect 2 inverters to the same grid tie without the need of 2 meters?
Do i need 3000w pure sine wave inverters to regulate the turbines 220v into xantrex's 48v?

Yes, more than likely your Wind GT inverter(s) will have to be sine wave--But I believe that is already a code requirement and you might have a hard time finding a MSW GT inverter (outside of the cheap stuff from China and such).

And the number of meters will also depend on your utility... Some have a single meter that does the billing measures... Other utilities have separate meters (measure your usage, and a second to measure your generation) so they can charge you for the power you generate and use.

This is a "big system"... At some point, you will have to get people/installers involved to properly design and permit your system (as well as install and get signed off).

-Bill

Windy

Re: grid tie inverter question

BB youre the man !
Still have my question with no answer. how can i get a interactive 3000-5000w on grid/off grid 220v input and output the same? do you know one?
because the xantrex is only 48v and the only one i know it goes both ways

this is what im looking at , from 220v to 48v transformers
http://www.alibaba.com/product-detail/CE-approved-AC-DC-rectifier-10A_753970581.html

BB.

Re: grid tie inverter question

I am not really sure what you are asking for...

The link you gave is (from what I could tell) is just a 220 VAC to 48 VDC Battery Bank to 220 VAC UPS system of sorts.

What is it exactly you are trying to accomplish?

It sounds like you want a to connect up Grid Tied solar + wind and back feed the utility.

And if the utility fails, you want the backup XW inverter to switch over to Off Grid Mode (transfer switch opens to utility side) and runs the 120/240 VAC loads off the XW inverter.

You connect the GT inverters to the "protected side" of the XW Inverter and those GT inverters will follow the frequency/voltage set by the XW inverter if off grid mode. The GT inverter will supply an amount of current based on the power available from the panels+turbines (more current from the GT, less current/power from the XW OG inverter).

If the GT inverter current exceeds the load currents, the power starts flowing "backwards" through the XW OG inverter and actually starts charging the battery bank.

So, in the case of what I described, the GT inverters "don't care" about 48 volt battery bank (note that there are 24 volt XW inverters and several other vendors with "hybrid" inverters that can run either in GT mode, Off Grid mode, or even be "back driven" by other GT inverters to recharge the battery bank.

-Bill

Windy

Re: grid tie inverter question

Oh, disregard the bank supply, i will want to have 6v trojans 105 wind at 240 amps each,
my question is if the xantrex is only 48v input can i connect a 220v turbine to it or i need to find a 48v turbine? because i like the flexibility of the xantrex being on grid and off grid also, if i want grid tie only i will get aurora grid tie inverter

If you like you can pm me and ill give u my number, its easier on the phone

mike95490

Re: grid tie inverter question

The XW inverter has 2 different, 240VAC inputs:
AC1 = Grid
AC2 = generator (with relaxed voltage and freq limits) Only one input can be selected at a time.

I now think, that to do what you are asking, would require 2 XW units. ($$ + $$) One to take the AC2 from the windmill, and charge batteries, and the other to take battery power, and feed the grid AC1 with it. A single XW cannot take un-sync wild AC, and push that to the grid, you have to pay the double conversion penalty.

SMA makes a "Windy Boy". I have no idea how it works, I don't have one.

And you will need a DUMP LOAD and BRAKING controller for the windmill, in case the grid goes down and the batteries are full, you have to STOP the windmill, or it will over-speed and grenade itself. I don't like battery dump loads, and prefer to stop the mill from spinning, and save bearing wear. 6Kw of load is a lot of power, and if not managed perfectly, it goes boom!

And the scale of this is so high, you will need a pretty sharp installer to manage this.

Windy

Re: grid tie inverter question

Mike you were very close. :-)
Both windmill and solar panels I want them grid tie, but if the grid goes down or apocalypse comes I want to switch to off grid where it will charge my batteries, I dont plan charging the batteries only when grid is down.
my problem is that the turbine is 220v and xantrex input is only 48v. Solar panels can be arranged easy.
If I get a 48v turbine 3kw im afraid wont make the same power of a 220v. And a 220v turbine if cannot be connected to xantrex then ill go with aurora grid tie and just buy a regular inverter to charge my batteries then?

Now i see you saying xantrex has 220v input, the website I read it said it has 48v input and 220v output, if that was a lie then I dont have tobworry about anything, all problems are solved.

BB.

Re: grid tie inverter question

There is a problem with large systems... The battery bank.

If you want a pair of 6 kW AC inverters and want to run some sort of GT operation with the Hybrid inverter, you are looking at a 1,200 AH @ 48 volt battery bank minimum. Something like a $16,000 (and up) battery bank that will need to be replaced every 5-10 years.

Also, I am not sure you are understanding today's "modern" Hybrid AC inverter-charger... They are fully bi-directional on both the AC power and DC power sides.

They can take AC charging current from the Utility or a Generator. They can recharge the 48 volt battery bank or draw from the battery bank. They can feed power back to the utility (turn your AC meter backwards).

They can, also, when the AC mains fail, run/control a genset. And you can put a Grid Tied inverter on the "protected output" and actually pump energy backwards from the GT inverter (wind/solar/etc.) and recharge the battery bank.

For example:

1) Connect the Wind Turbine (through a rectifier) to the battery bank (48 volt turbine to 48 volt battery bank).
2) Connect the Wind Turbine (through a rectifier) and MPPT charge controller to the battery bank (more efficient) (48-200 VDC+ turbine to MPPT controller to battery bank).
3) Connect the Wind Turbine to a GT AC inverter to the Hybrid inverter's protected output recharge the battery bank (48-400+ volt turbine to 240 VAC protected mains.

And any of the above, if you have excess wind power available, can feed energy back to the grid and turn your AC meter backwards (sell power to the utility).

These are really the electronic versions of an Erector Set... You can do quite a bit with a few major components.

However, I would really try to convince you not to build the above system. It is a) way to big to be cost effective ($100,000's for a full 12 kW capable wind+solar panel system; b) I do not believe that most "store bought" wind turbines are mechanically sound (add a 60-90+ foot tower + electronics + something to lift it to the top of the tower is expensive).

And put all of this together--You are pretty much tied to battery mfg. (replace every 5-10+ years), electronics vendors (replace every 10+ years), wind turbine vendors (inspection/service every year or two), backup genset+fuel to keep the batteries "happy" during bad weather, etc...

If you are looking for something you can maintain and not break the bank--You should figure out the minimum amount of power you need to survive. Many folks do OK on ~3.3 kWH per day system (100 kWH per month) and a 1.5 kW AC inverter with a "modest" battery bank.

There are many different ways to proceed here... But we always want to start with the loads (peak watts, Watt*Hours/kWH per day, seasonal loads, location of installation for amount of sun by season, etc.). The next steps are pretty much cookie cutter math to figure out the basic system.

Very few people can justify flying large wind turbines--And the small ones, are simply not worth it. For most people, solar panels with a backup genset or two and a modest size system is the way to go.

Just to give you an idea of what a headache a large system can be--Read this thread:

Is the system set up right

The poor owner tried to do everything right. Did not skimp by buying cheap stuff. Hired an engineer and installer that should have known what they were doing. And it barely worked.

A 3.3 kWH per day system... That is "doable" by a DIY person who does their research before hand. A system 10x larger--You need to do your research so you know what you want and can oversee those doing the work. These big systems are not something I would recommend for your first venture into off grid solar power.

-Bill