Grid-Tied Inverter - Guidance please

[WA3PYI]

Greetings All,

I am considering installing some sort of RE system at my home.  We live on a small farm that used to be an operating dairy farm in rural Pennsylvania where it is not really considered to be great for sun nor wind - but I guess we have to work with what we have.  We burn firewood (excuse me - I mean we use biomass for heat) and I have been making and using biodiesel for over 3 years now.  My motivation quite honestly is not to be "green" or eco-friendly but financial - I just want to save a few bucks and be ready in case some terrorist country wants to test their highly enriched uranium here in the USA.  Our electric company's rate caps will expire at the end of this year and rates are expected to take a huge jump.  In our area the Skystream 3.7 wind turbine has been popping up quite a bit but that option seems way overpriced (about $12-$15,000 installed).  

I have been researching other grid-tied alternatives and I believe a better system than the Skystream can be built for less.  I would like a system that could be expanded to include wind and solar as funds allowed.  I would also like a system that would be able to work even when the grid is down (which rarely happens but I want to be prepared).  We have a 240V well pump that I would like to include to run when the grid is down and I've calculated that about 5000-8000 watts should be plenty to run all the basics.  Since the inverter is the heart of any system I am trying to pick that item first.  Based on my criteria I think that I need a system that can be grid-tied and supports batteries.  After digging around on the internet for a while I've found a couple that look like good possibilities.  I've picked 48V for my battery voltage since that seems to be a good choice for working with either solar or wind.  I'm looking at either the Outback GVFX3648 in a 7200 watt configuration (like here:

http://www.wholesalesolar.com/inverter-system/outback-power-flexware-solar-power-center-2564892.html

or a Xantrex XW6048 (like here:

http://www.xantrex.com/xw/

Am I going in the right direction or are there some things that I've left out in thinking through all this?  I know there will be a lot of extra parts beyond just the inverter that will be needed. I have an engineering degree and am not afraid to put together a system myself - I just need a little guidance from those who have already gone down the same road.

Thanks!

[Roger Stafford]

Hi I,m new too, but have a xantrex 6048 and when the wind gen (17ft otherpower design) production drops in variable winds the inverter goes into standby, Then the wind picks up and production rises fast the inverter has a 20 second delay before it goes back into the sells mode. This causes the voltage to go up and starts dumping power and-or trips my auto shutdown .Please read my posts for other problems I have been haveing. The latest is a fried stator. I think the 20 second delay  was part of the cause as well as not furling. I'll be back in Arkansas in march to fix the furling and stator.  I'm not saying not to buy a xantrex just check the outback for delays comeing out of standby. wish you lots of luck in your RE endivers.

Roger

[GaryGary]

Hi,

There are some example grid-tie with battery backup systems here:

http://www.builditsolar.com/Projects/PV/pv.htm#Grid%20Tie%20+%20Battery

The Rockriver one is a bit hard to read, but has a lot of detail on how the system was designed and put together.

If you have not yet discovered Home Power magazine, they are a great resource -- I think they still have a $10 digital subscription that gets access to all the back issues.

I just put in my system, and decided to go with grid-tie only -- you can see how much simpler and lower maintenance it is, but the price is losing power when the grid goes down:

http://www.builditsolar.com/Projects/PV/EnphasePV/Main.htm

Gary

[WA3PYI]

Roger, Thanks for the info about the Xantrex.  Too bad they don't let you change some of the parameters so this could be avoided.  Something like: [Stay on batteries and continue to sell to grid until batteries are 50% discharged. When batteries are over 50% discharged-stop selling to grid.  Let wind turbine charge batteries.  When batteries are at 100% start selling to grid again.]  Seems like something like this would provide some hysteresis buffering.  I've also read on this board where the Outback system has less overall cost when you factor in all the other parts needed besides just the inverter.

Gary, great site!  It will take me a while to dig through it but looks like lots of real world experiences - Thanks

How do the Otherpower wind turbines compare to some of the other stuff that I see out on the web.  Some websites selling wind turbines seem a bit too good to be true such as:

http://www.beawindhog.com/

and

http://www.missouriwindandsolar.com/

The Otherpower design seems more realistic and conservative and even the complete kits seem resonably priced.

[ghurd]

"a bit too good to be true"

Yup.  2,000W out of a car alt with 80" dia metal versions of PVC blades is 'optimistic'.

And I won't mention anything about 12,000W from a Long-Lasting car alt.

Maybe that's just me.

G-

[ibeweagle]

have installed 2 systems from wholesale solar and are simple to do and so far great reviews for outback products cheers Mike ibeweagle@hotmail.com GVFX systems so can do grid or off grid depends on utillity Red tape and cost of grid tie hoops to jump through have not grid tie but have the abillity too, tested on 220 volt plainer 18 amps two GVFX3528s 24 volt system did great ran all day off grid

[WA3PYI]

Which is better to hook up the Outback GVFX to a 220V system?  A single GVFX inverter is a 120V inverter and it looks like the systems from Wholesale Solar use 2 of them phased locked together to provide 220V.  But I see Outback makes a nice 2:1 autotransformer to step up a 120V system to 220V.  Are there advantages/disadvantages to using the 2:1 autotransformer or does phase locking 2 units work just as well?