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Grid Tie only system - no battery bank


By dlenox, Section Controls
Posted on Wed Nov 14, 2007 at 09:44:34 PM MST
interested in connecting my turbine via grid-tie, not off-grid

All,

I've noticed that it seems that a vast majority of the larger turbines (16 - 20 ft diameter) are used in an off-grid system.  I did not see a lot of people doing a grid-tie system.

In my situation I desire to be connected to the grid, not off-grid.

I have a 17' diameter that I recently built, very similar to DanB's turbine. It used dual 18" rotors each containing 16 of 1-1/2" x 3" x 3/4" N42 magnets, 12 coils using 80 turns of #12 wire (almost 20# copper total), cut-in voltage is 48 volts.

I've been researching the Power One 6000w and Windy Boy 6000 inverters for my grid-tie system. I really desire a simple system in not using a battery bank, but direct connection from my rectified DC into the inverter.

In addition my entire house/shop will be on the circuit with the disconnect switch to the grid, so if the grid goes down or I am switched off the grid that my house/shop will be providing a load to keep the turbine from over-speeding.

I know that the 6000w inverters are overkill, but they also give me room for future expansion with either re-configuring my turbine, or even replacing it with something larger in the future, as well as adding a PV array.

Since I really do not want to use a battery bank there is nothing to keep the voltage 'clamped down' to approx 48 volts, and as wind speed picks up the voltage and current generated should also increase.  But I have not idea as to what the voltage and amperage could be produced by my setup.

I contacted SolaCity.com and they are currently selling the Power-One unit for $3211 which to me sounds pretty reasonable.

So here are my questions:
     - what can I expect to see in output voltage/current
     - comments on batteryless grid-tie system
     - if house/shop load is not sufficient can a dump controller somehow be used to provide additional load for the turbine

thanks,
Dan Lenox
Grid Tie only system - no battery bank | 24 comments (24 topical)

Re: Grid Tie only system - no battery bank (3.00 / 0) (#1)
by wdyasq on Wed Nov 14, 2007 at 03:00:23 PM MST

Dan,

I have a question for you....

Without a battery bank or some sort of storage system, how do you expect to power this house/shop. The interconnection of the grid gives a bit of inductance. With no storage and small or no inductors how is this going to work?

Curious,

Ron
Adventure is just bad planning." -- Roald Amundsen



Re: Grid Tie only system - no battery bank (3.00 / 0) (#2)
by zeusmorg on Wed Nov 14, 2007 at 03:29:42 PM MST

 Most grid-tie only systems rely on being connected to a live grid to give a usable waveform, and shut down when the grid power goes down. They automatically shut down to protect from "islanding" or feeding voltage to the grid which could electrocute an unsuspecting electrical worker. Some do have a battery charger system installed, but I haven't seen one that could be grid tied only and still supply power when the grid goes down. The idea behind grid tie is to feed back your excess power to the grid, and then use from grid when your usage exceeds demand, for an individual this saves money on the battery bank, and also increases overall system losses incurred.
 The only solution i see is either purchasing a grid-tie inverter with battery backup charging, or figure out some sort of automatic switching to use a dc dump load in the event of a grid failure.



Re: Grid Tie only system - no battery bank (3.00 / 0) (#3)
by Ungrounded Lightning Rod on Wed Nov 14, 2007 at 04:32:30 PM MST

Most of us don't do grid-tie-only because it's not a good deal financially.  The cost of building such a system is never recovered in power bill savings (even assuming significant price hikes and lots of "sweat equity" from home-brewing - though wind power MAY come close or even cross over on a very good site).  Meanwhile, if the grid goes down, you're sill out of power.  You'd be ahead to put the money in a mutual fund and use the growth to buy line power.

RE makes economic sense in three situations:

 - A GREAT site where you're building a commercial wind farm.

 - New construction far enough out that the power company will charge you some big bucks for a hookup.  Then you can apply that cost to the up-front costs of an RE system instead and come out ahead.

 - A site with good RE resources, a large load that requires reliable power, and rotten enough grid power that you MUST do a UPS.  Then you can do the UPS using a grid-tie inverter and RE-style battery bank.  Your costs drop to the cost of the generation (mill, panels) plus any excess cost of the RE-style inverter/battery bank versus a purpose-built UPS.

So absent a wind-farm situation a grid-tie only system is a fun hobby or an eco feel-good project, not something financially useful.



Re: Grid Tie only system - no battery bank (3.00 / 0) (#4)
by wdyasq on Wed Nov 14, 2007 at 04:45:52 PM MST

UGL,

Would you quit putting reason into the argument..... Next thing you will be claiming that the individual can't produce power as cheaply in small amounts as the electric companies can in large amounts.

Ron
Adventure is just bad planning." -- Roald Amundsen
[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#5)
by dlenox on Wed Nov 14, 2007 at 05:00:35 PM MST

ULR,

You are right, for the most part this is a fun and 'feel-good' project, if I can get payback with less than a 10yr period then I would be happy.  My goal is mearly to reduce my electric bill to the minimum billing amount, so at best I would save about $130 per month (figuring a $150 electric bill to start with).  But I am not so concerned about the financial aspect as the 'green' aspect.

From my research (correct me if wrong) but the Power-One units advertise themselves as a battery-less system, they state that they can get a 97% effeciency by avoiding batterys all together.  Not only that but if the grid goes down it disconnects but keeps operating on my local house/shop circuit, so it doesn't shut down completely.  I do have a call into Power-One to talk with a technician to verify.

Currently my thoughts were that I would install battery bank if absolutely required, but initially trying to avoid system complexity and costs.

Off grid is not an option for me - period.

Dan Lenox

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#6)
by vawtman on Wed Nov 14, 2007 at 05:16:15 PM MST

Hi Dan,
 Where you from?
 I think the best use of a battery free wind turbine is to heat water.
 Your state will send a pamplet(think thats required)Mine did.Meter spinning backwords would be cool but not much income in the overall scheme.
 An opinion.

 My thoughts are for a large preheater tank(old converted fuel tank)in the basement.

 Why deal with the guberment if you dont have to.

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#9)
by dlenox on Thu Nov 15, 2007 at 06:25:36 AM MST

Ok after re-reading what I wrote it doesn't make any sense.  If the grid-tie inverter disconnects from the grid it would have to have a 2nd output for local consumption...

Dan

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#12)
by ghurd on Thu Nov 15, 2007 at 06:47:32 AM MST

And it would have to have a battery.
G-
Ghurd.info
[ Parent ]


Re: Grid Tie only system - no battery bank (3.00 / 0) (#7)
by Devo on Thu Nov 15, 2007 at 05:07:39 AM MST

I see alot of nay sayers for grid tie , I have to admit I have been thinking that route lately as the cost of a grid tie invertor has come down dramatically the last 5 years. Of course I am not saying you won't have other big charges & regulations just saying it is getting more reasonable.

If the mill is big enough & you get good wind you are both(Ron & UGL) saying grid tie has no way to pay for itself long term is this correct?I am looking for insite as well.I am asking as I value both your opinions & don't want to go down a road that is not feasable.

dlenox I can't help you with the question , but I've seen a 5000 watt grid tie with battery chargeing capability for under 3000 US dollars. If the prices are similar why not add the batteries?

Devo    



Re: Grid Tie only system - no battery bank (3.00 / 0) (#10)
by dlenox on Thu Nov 15, 2007 at 06:27:09 AM MST

Devo,

what system are you referring to?  would like to see what they have to offer, any links?

Dan

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#8)
by thefinis on Thu Nov 15, 2007 at 05:20:57 AM MST

You can do a system without batteries but not with backup power. To get backup power for most homes would require a very large battery bank and a big inverter(or a gas generator). If you build a system with/without batteries then it should be a net metering system as it is one of the only ways a home RE grid tie makes any sense/cents. Do not expect most home RE systems to pay for themselves by selling electricity to the grid only by reducing or recovering costs from electric usage. The electric companies don't want to play that way yet where they send you a check. There are a few exceptions see posts above. There are some areas of the world that have the incentives and price structure to make it work but I don't know of anywhere in the USA that it is happening.

Wish it was better news but if you want backup power use batteries even with grid tie. IF you just want to reduce the electric bill conserve/moderate usage as the best way.

If you want to play and watch the turbine and have lots of investment capital go for grid tie and net metering. It will have a chance to repay the investment but only based on a good wind site, rising electric costs and favorable future gov involvement laws/regulations.

Good luck have fun
Your results may vary

Finis
Texas born and bred



Re: Grid Tie only system - no battery bank (3.00 / 0) (#11)
by dlenox on Thu Nov 15, 2007 at 06:41:01 AM MST

thefinis,

If a grid-tie inverter shuts down due to grid outage, then how does a battery bank help out?  It would seem that you need a 2nd inverter to convert the DC back into useable AC - something does not make sense here.

Maybe the question really is: In a grid-tie system, when the grid goes down (and your inverter essentially shuts down) and your wind turbine is operating, then how do you provide power to your home/shop with a battery bank - with the assumption that your house is wired for AC?

I had previously researched this issue and now I find myself confused

Dan Lenox

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#13)
by TomW on Thu Nov 15, 2007 at 07:09:47 AM MST

dlenox;

If a grid-tie inverter shuts down due to grid outage, then how does a battery bank help out?  It would seem that you need a 2nd inverter to convert the DC back into useable AC - something does not make sense here.

Maybe the question really is: In a grid-tie system, when the grid goes down (and your inverter essentially shuts down) and your wind turbine is operating, then how do you provide power to your home/shop with a battery bank - with the assumption that your house is wired for AC?

I had previously researched this issue and now I find myself confused

Well, for one thing, you can buy Outback inverters that do all of this. But they need batteries to be used if grid failure occurs. Your research must not have been very current because they have sold these for awhile now. Might be worthwhile to check this link and follow it through some for more info:

http://www.outbackpower.com/grid_interactive.htm

Its not rocket science to understand that a backup power capable system will require batteries. Period. End Quote. Thats all I have to say and just go to outbackpower.com and look at the "GFX" series of inverters. I am not affiliated with them, just a satisfied customer with a non grid interactive inverter.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it


[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#14)
by wdyasq on Thu Nov 15, 2007 at 07:26:00 AM MST

It is actually pretty simple if one just looks at the 'bits' and sticks them in place.

Outback and several others make grid-tie battery connected inverters. Someone mentioned  they 'didn't even notice the lights flicker' when they lost grid power, just like a whole house UPS.

To me having pure grid tie is like leasing your 'hot' girlfriend or wife to the local pimp. If the pimp decides to take the source out, nobody gets anything. And, while it cost is yours to feed and maintain the thing. The pimp sells at a high price and gives the one maintaining everything a few coins and calls it an even trade. BUT, the pimp is in control. He tells you when you can use and how to maintain everything.

Good idea ...

Ron
Adventure is just bad planning." -- Roald Amundsen
[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#16)
by marv on Thu Nov 15, 2007 at 10:27:15 AM MST

Dan, Have you checked out this multi-mode 5KW inverter by Power One?
You can connect it to solar, batteries, wind and power generator all at once.
And still benifit from MPPT it offers.
from around 40vdc-500vdc input
I think they also have a voltage clamp and diversion load port.

http://www.power-one.com/resources/AlternativeEnergy/mwius2.pdf

Marv.

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#15)
by Devo on Thu Nov 15, 2007 at 10:05:39 AM MST

This was one I was looking at (just looking) in case the wife reads here-lol...

 http://store.altenergystore.com/Inverters/On-Grid-Off-Grid-Capable-Inverters/2501-5000-Watts/Xantrex -XW4548-InverterCharger/p5955/

But maybe staying with batteries,invertor charge controllers is the best way, I'm not 100% sure just looking at my options as I build turbines,I am also getting a Lister engine in the near future so someday I want to tie it all together...

I almost think I would rather run with-out Grid tie & when you need extra juice kick on the lister...not sure.

Devo



Re: Grid Tie only system - no battery bank (3.00 / 0) (#17)
by dlenox on Thu Nov 15, 2007 at 12:02:46 PM MST

Devo,

This looks like a very nice unit indeed, and price is right inline with what I was looking for.

I had not previously seen this item, gosh there are just so many inverters for sale that looking at all of the specs on them can become overwhelming unless you create a spread sheet.

I also noticed that you could turn off the 'sell' function so that it would not feed power back into the grid, but allow power IN from the grid when your local generated power is greater than it can handle.

It looks like for what I am looking for that a battery bank is required, so I think that I will just accept it and figure it into the system right from the start.

I already have heard too many con's against the SMA Windy Boy so am ruling it out.  It seems that Outback is quite modular, however by the time I added up all accessories that I wanted it was right at the price of the Xantrex which had them built in.

Any body have preferences between Outback, Xantrex?

Dan Lenox

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#18)
by dlenox on Thu Nov 15, 2007 at 12:05:16 PM MST

That should have read "when your demand for power is greater than locally generated"...

[ Parent ]


Re: Grid Tie only system - no battery bank (3.00 / 0) (#19)
by dlenox on Fri Nov 16, 2007 at 02:12:45 PM MST

Devo,

Just found out that the XW4548 is not currently available.  I have talked with two distributors and one said that they don't expect it to be available until 3rd quarter 2008...

I did find out that the XW6048 IS available though.

Dan

[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#20)
by Kevin L on Sun Dec 02, 2007 at 10:26:25 PM MST

Grid tie may make you feel good, but you can save the environment by pumping less CO2 into the environment by reducing your consumption of heating fuels(natural gas, fuel oil, ect). If you live in a cold climate you can use you windmill purely in a dump load situation and dump all the power through baseboard heaters and/or water heaters in your home.  No inverter, no batteries, and you will save more CO2 consumption and money then with a grid tie system. Why reduce payment to Peter(electric) when Paul(gas) is robbing you blind?

[ Parent ]


Re: Grid Tie only system - no battery bank (3.00 / 0) (#21)
by DamonHD on Mon Dec 03, 2007 at 02:41:00 AM MST

It is much better (2x to 3x) to heat with natural gas (methane) than electricity in terms of CO2 per kWh of heat.  In the UK this is roughly mirrored by the retail costs too.

Rgds

Damon
"Once you have licked the windows of freedom your tongue gets stuck."
[ Parent ]



Re: Grid Tie only system - no battery bank (3.00 / 0) (#22)
by JasonPAtkins on Fri Jun 05, 2009 at 08:38:43 AM MST

Any one want to follow up on this on as new development may have arived since this posting?


Re: Grid Tie only system - no battery bank (3.00 / 0) (#23)
by spinningmagnets on Fri Jun 05, 2009 at 09:03:54 AM MST

scottsai has done quite a bit of research into grid-tie in hopes of eliminating a large expensive battery pack, but he is now certain he will want a small battery and back-up generator at a minimum.

[ Parent ]


Re: Grid Tie only system - no battery bank (3.00 / 0) (#24)
by Kid on Fri Jun 05, 2009 at 09:48:13 AM MST

I have a 48v 17' system that I would like to make grid tie only as well and I have not seen much on the posting that are vary clear on this. I was told by DC Power Systems, Inc. (Since virtually all grid-tie small turbines are wound for 200 to 400 VDC, this will be a problem - unless you use a battery bank in the mix). So should I rewind a stator for such voltage or is there a true way of doing this with what I already have?
Kid


Grid Tie only system - no battery bank | 24 comments (24 topical)
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