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How does a wind turbine grid tie?
By force9BOAT, Section Controls Posted on Tue Feb 20, 2007 at 11:59:26 PM MST
Does GT Inverter set the cut-in voltage?

Hello,
My wind turbine is connected to a 24V battery bank. So it spins freely until the voltage reaches 24V cut-in. When a wind turbine is grid tied how is the cut-in voltage set? Is that a function of grid-tied inverters?
Also, can the same GT inverter accept both solar and wind input?
Thanks all,
Rob
P.S. - I'm working on my federal tax return and was pleasently surprised to discover a tax credit for the PV I purchased last year.

How does a wind turbine grid tie? | 12 comments (12 topical)

Re: How does a wind turbine grid tie? (3.00 / 0) (#1)
by jmk on Tue Feb 20, 2007 at 06:01:34 PM MST

I have an Xantrex SW-4024. I can program it to sell power back at what ever voltage or to sell the batteries storage at a certain time of the day to an advantage of peak hour rates. You can set it so anything above 27 volts on your battery bank will go to the grid instead of the dump load or charging the batteries. It doesn't matter if you have solar or wind hooked up to the batteries. If you get rid of the batteries I don't know how it would work with That type of inverter. Instead of grid tieing I like to just put a larger load than my turbine can run on the iverter. With the charger side of the inverter pluged into the grid it will hold the bank at 27 volts when I get wind the charger lets up and lets the turbine work the loads. If there is no wind the charger lets ac slip right by to power the loads. If the turbine is making any percent of the power the charger will use grid power to make up the differance. This way I am not selling to the grid but selling it to a load of my own. The battery stays charged and the dump load hardly goes off unless it is realy windy. Almost all the power the machine - solar make goes to a deducktion of my power bill. You have to make alot of power to make it worth selling power to the grid.
jmk

Re: How does a wind turbine grid tie? (3.00 / 0) (#2)
by ptitchard on Wed Feb 21, 2007 at 05:56:52 AM MST

Hi,
I am no expert but have looking at hooking up my smallwind turbine to a grid tie inverter and doing away with the batteries.
The problem with most inverter designs is firstly they are designed for solar systems and employ a MPPT system which is incompatable with wind turbines.
Secondly the cut in voltage tends to be on the high side ie Windy Boy 139 Volts DC max volts in 600V DC so unless your generator is designed for this voltage they are useless.
There are a few smaller inverters now coming onto the market to address the low voltage wind generators have a look at SWEA UWT-I-250 (http://www.swea.nl)cutin about 26 V Maximum 55 VDC

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#3)
by force9BOAT on Wed Feb 21, 2007 at 10:34:12 AM MST

Thank you for this information. This sounds very intersting. So is the Xantrex simply plugged into a wall outlet then to get AC from the grid? Or is it intigrated into your home fuse box?

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#4)
by craig110 on Wed Feb 21, 2007 at 11:06:25 AM MST

I have an Outback GTI, but I'm sure they connect in the same way. The GTI sits between the line coming into the house and the distribution panel. If it isn't in the middle like this, the GTI can't detect when the grid power has gone down and thus won't be able to know when it can't backfeed current out to the grid. Additionally, being in the middle like this allows for much larger power capacities: If the GTI was merely plugged into a wall outlet then the maximum power that could be fed back would be limited by the amperage of the line feeding that outlet. My Outback can handle 6000 watts (if only I had that many solar panels :-), and it wouldn't be able to do this through an outlet.

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#5)
by force9BOAT on Wed Feb 21, 2007 at 11:17:34 AM MST

Thank you,

Now I understand. I would need to have a licensed electriction install it then.

Rob

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#6)
by Ungrounded Lightning Rod on Wed Feb 21, 2007 at 01:54:37 PM MST

I would need to have a licensed electriction install it then.

Not necessarily. You WOULD need to have the installation permitted in advance and inspected afterward. But if you own your place you can usually do the work yourself.

(But there are a number of government subsidies and tax breaks in many locations, which you might not be able to get unless you have it installed by a licensed contractor of some sort - and HE'd probably have to use a licensed electrician.)

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#7)
by force9BOAT on Wed Feb 21, 2007 at 04:56:29 PM MST

That's good to know about government subsidies. When it comes to touching the mains I would want an electrician anyway. I don't want to get myself killed :>)

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#8)
by jmk on Wed Feb 21, 2007 at 05:02:10 PM MST

You can plug it directly into wall socket if your not going to use much current or not sell back to the grid. I put a 40 amp breaker in my fuse box to run the charger side only. I ran # 6 to the charger I don't believe it is necessary to sell power back to the grid. Mine is set up to just assist my R-E. The inverter is not programmed to sell on mine I have that option off, and am using the charge mode. I only bring in 70 amps at the height of a strong gust, and that is getting dumped into a resistor. I usually don't run it in wind that strong anyway. I work around 10 amps most of the time. I have a 24 volt system too.
jmk
[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#9)
by jmk on Wed Feb 21, 2007 at 05:32:06 PM MST

How many amps your charger side of the inverter will put out has to be programmed. It is calculated by the size of your battery bank. They have a equation chart in the manual. After I figured mine out I set the charger to 16 amps. I think it goes as high as 60 amps. I only have four L - 16 batteries. It will know how many of those 16 amps to use depending on how low the batteries are. It also knows if you have a load running and if it needs to run it. If it does need to run any part of the load it just lets the grid ac go to the load. It also knows if your producing R - E power, and uses every bit of that to keep your loads or batteries at your float voltage. I like to let mine float at 26 volts so I have some battery space to take the highs of the wind instead of the dump load always going off.
If you grid tie that will be totally different. You will need an accessory part for the inverter so it knows when the grid is out so it doesn't feed power back. You have to get another meter usually. If they let you just turn your meter backwards then you will be in a win win situation. If they buy it from you for a percentage of what you buy it from them you lose. Then you might just as well try to use all your power made yourself.
jmk
[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#11)
by force9BOAT on Wed Feb 21, 2007 at 07:47:35 PM MST

Your turbine can put out 70 amps at 24V? Wow, that's a lot. How big is your wind turbine?

Three days ago we had 25mph wind and I saw my machine top out at 16 amps (400 watts). Mine is a 10' turbine. In 25mph wind the tail is furled to the max.

[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#12)
by jmk on Thu Feb 22, 2007 at 05:50:45 AM MST

Yes, in a 30-40 mph gust it hits up 70 amps. It's Hugh's 12 foot turbine. The tail isn't furlling right yet though. I need to make it have a smaller deg on the angle or maybe try 3/8" plywood. I don't know how to make it lighter without building a whole new tail. I screwed up and made my twelve foot test tower the top of my main tower. The top guy wire is in the middle of that because of blade clearance. It makes a bad leverage of six feet to the next tower pipe. Next summer I might have time to put the 12' piece at the bottom, so I can have 15' of leverage to hold the top six foot. What is happening is the top leans about 2" and increases my angle on the furl. This makes it harder for it to pick it up. It does go up with the right wind, but not soon enough to leave it running in strong wind. About 20 mph wind puts it at about 20-25 amps, but the gusts will take it to 30-40 amps. I only have seen 70 once, and 60 about five times. I could see it happen alot but I shut it down in wind above 20 mph. I figure I'll save my machine for another day. With little room in the battery for storage, while running a 250 watt load, and useing a C-40 to control a dump into a 1,000 watt resister I saw 60 amps hold and my C-40 shut off for about 5 seconds. Thank god it turned back on and I shut the turbine off. Now I don't turn it on anymore to see what it will do in stronger wind. Close one, phew!

jmk
[ Parent ]

Re: How does a wind turbine grid tie? (3.00 / 0) (#10)
by craig110 on Wed Feb 21, 2007 at 07:38:31 PM MST

Whether you have to have a licensed electrician install it depends upon your local area. Here in New Hampshire, for example, I can legally do all the installation myself. (It still does need to be inspected, of course.) Just a few miles south in Massachusetts, in addition to the inspection they almost need a licensed electrician come in to change a light bulb. ;-) Bottom line - check with your local authorities before believing any "you have to get an electrician / no you don't" discussions on an internet forum.

[ Parent ]

How does a wind turbine grid tie? | 12 comments (12 topical)

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