Net metering in Arkansas

[ToddT]

Arkansas has nice net-metering rules. Essentially, any electricity generated by renewable resources can be fed back into the grid at a 1:1 rate. Not avoided cost. KWH out, kwh in. We can generate a credit from month to month. Renewable energy includes biomass and biofuels. I currently run my company off-grid and am working on cogen for process heat. Most of my electricity comes from a diesel generator running on veg-oil based fuels (biodiesel and others). I have also been working with biomass gasification for the past six years.

I want to install a generator at the house, running on used cooking oil and/or biomass gasification. My plan is to run it during the winter, generating more power than needed and creating a credit with the power company. I'll also capture the exhaust and coolant heat for home heat. I also have some solar hot water panels as well. What are some options for connecting to the grid at 7kw to 12kw? Use a rectifier to convert it to DC and then come back through an inverter/controller for grid quality power? Ideally, I want to be able to have power during outages as well.

Any suggestions on the grid intertie options?

[ToddT]

My house was built in 1925 (pier and beam, frame house) and currently has a really old natural gas central heating system. The AC portion is likewise pretty old. My plan is to rip out the A-coil from the air conditioning as well as the gas heater chamber and install a liquid to air heat exchanger instead. Hot water/glycol will come from generator coolant, exhaust heat, solar panels and/or a waste oil heater made from Murphy's Machines (long time reader of the infopop.biodiesel forum). I could also install an outdoor wood fired heater.  I have already bought window units to use in lieu of the central AC.

I have Changfa style generators: 7.5kw, 8kw and 12kw.
 
I already have a stainless steel rectanglular open top tank approximately 134 to 150 gallons which I plan on using as a common reservoir. Pumps would be used to circulate coolant through the heat exchangers in the various sources of heat. Another pump would be used to circulate that hot glycol through the exchanger in the central heating system.

Could the existing A-coil from the central air system be adapted to handle hot glycol? I also have a couple of spare automotive radiators if they would help.

I've been told that I'm too far south (only 20 miles from the Louisiana border) to use radiant floor heating. I'd love it and have good access in the crawlspace below. But, I can see our temperature swings could be tough. It may turn off bitterly cold for a few days but then turn around and call for air conditioning a couple of days later. Do any forum members have experience with radiant under-floor heating in the South?

[ToddT]

Something else I've considered is setting up two generators: one creating AC power for use during outages and one generating DC current to make it easier to do net-metering. I have a 7.5kw as well as an 8kw Chinese horizontal diesel generator. Heck, I have even bounced around the idea of using an old Lincoln SA 200 "pipeliner" gasoline driven DC welder to make straight DC power.

[glort]

I want to install a generator at the house, running on used cooking oil and/or biomass gasification. My plan is to run it during the winter, generating more power than needed and creating a credit with the power company.

Best you read this before discussing the idea further.

http://www.microcogen.info/index.php?topic=3265.msg36462#msg36462

[mike90045]

Something else I've considered is setting up two generators: one creating AC power for use during outages and one generating DC current to make it easier to do net-metering. I have a 7.5kw as well as an 8kw Chinese horizontal diesel generator. Heck, I have even bounced around the idea of using an old Lincoln SA 200 "pipeliner" gasoline driven DC welder to make straight DC power.

For DC, it's a 3 phase motor/generator driving a rectifier diode bank, and then into a standard Grid Tie Inverter.

AC for your private island, whatever floats your boat.   

I'd consider one of the hybrid inverters, that can do both grid-tie, or run off batteries. Xantrex, Outback and SMA have hybrid models.

[LowGear]

As always, I'm with bob g.

And when one of you finds a legal, utility approved and transparent way to hook my Witte up to the grid Please Let Me Know.  One blind alley after another has been my experience for about five years now.

Casey

[ToddT]

Without a doubt, I want to do it in full compliance. No desire to do otherwise. Few around here understand net-metering with a solar system. Forget thinking about running a generator. The US Forestry Service has a wood gasifier driving a 25kw generator set up for net-metering but that is big enough to do syncing of the power. In talking with Woodward controls, I find anything smaller just can't maintain a constant speed sufficient to stay connected with the grid.

I've considered some of the hybrid systems that allow AC input. Some say I'll need a complete bank of batteries. Some say only one. I understand the idea is to convert to DC and back to AC through a grid-compatible inverter-controller. I have a feeling the controller syncs with the grid and puts out AC that is safe for the grid.

For sure, I'd never think of running a motor backwards or something like that. Above board all the way. As for the SA200, my only thought there was that it would generate a DC current that an inverter-controller could handle.

[vdubnut62]

Todd, you have only scratched the surface,  and to net-meter legally...... well from the "Upper Echelon"  on this forum it's just impossible  and too dangerous with out spending thousands of dollars on special grid-tie inverters,  alternators, three phase generator heads, huge battery banks, arcane anti-islanding circuitry and the like.  Oh, and using an induction motor for generating power is not a redneck undertaking, it's a perfectly valid method of generating power. You do, however, need to reference Bill Rodger's excellent book on the subject, it can be purchased at the  link here:    http://www.utterpower.com/products/books/

This is my opinion only, and does not necessarily reflect the opinion of the Moderators or members of this or any other forum.
Ron.

[mike90045]

As always, I'm with bob g.

And when one of you finds a legal, utility approved and transparent way to hook my Witte up to the grid Please Let Me Know.  One blind alley after another has been my experience for about five years now.

Casey

Witte - generator - Charge Controller - 48VDC  battery bank (100ah for each 1Kw export/usage) - XW 6048 inverter (6Kw, stackable ) - smart meter - Grid.
  Needs city electrical permit, needs utility company buy-in / approval.   Stick a solar panel on the roof, and claim it's solar power, not engine.

[vdubnut62]

And when you claim solar power, and are using the genny and you are inspected, you are still in violation.
Ron.

[ToddT]

I have Bill Rogers' book. Man, talk about going over my head! I design chemicals and processes for a living. Reading that book just showed me how much I DON'T know about electricity. That said, I have a feeling that the only way to get our utility provider to sign off on an installation would be to use recognized off-the-shelf hardware from recognized providers in the renewable energy field. UL approval would go a long way.

And yes, I've thought about having a minimal amount of solar at least to get some tax credit. As for running a generator, our net-metering rules are written to accept biomass as a fuel. So long as it ties in to the grid in sync and has the required disconnect relays for when the grid goes down, I'm pretty sure I can get the green light.

In the past, talking to the inverter/controller manufacturers didn't get too far. They are into solar and frankly, the market demand is so small for running generators on renewable energy, I can't blame them for spending a lot of time on it.

Thanks for your suggestions, Mike. I'll check out the hardware you listed. Well, except for the Witte. I'm in oil country and would love to find an old Arrow or similar gas engine from the old days running pumps in the oilfields. I can remember hearing them all through the nights when camping out as a boy in the mid-'60s. Most were scrapped when there was a big push to go electric drives. And of course, a gasifier to run the engine on woodgas. But, that's for another day.

Thanks for your help, guys.

[glort]

When I was in a place that allowed it and didn't contravene any laws or moral standards.....

I set up an induction motor on a diesel engine running veg oil and ran it as a generator.  Wired it up in Wye and a put the Ac through a bank of 3 Bridge rectifiers I built as I didn't have a 3 phase type handy.  Ran the genny up to just under the voltage rating of the caps and connected up a commercial solar  grid feed inverter.

I had a little work in getting the caps right to hold the excitation on the motor when the inverter loaded it to the grid but once I had that sorted, it worked well.

If  a person who lived where this was allowed and complied with every relevant law, code, moral standard and other red tape were to  use a proper solar inverter as a grid interface, that will take care of the grid power standard requirements. It will condition the power to the proper phase and voltage, provide grid disconnect in event of power failure and all the other things they do in order to allow them to be in compliance when hooked up to solar panels as is widely allowed.
What you power them with is basically irrelevant ( technically speaking of course) as long as it is within the parameters the inverter requires.

This is not complicated or difficult to do.  I can't see why it could also not be done with a regular generator that was either single or 3 phase.  A bridge rectifier would convert the AC to DC to power the inverter which would take care of everything from there.
From what I understand, there are many regulations, codes and specifications for having a non grid connected stand alone generator on your own property.  Thankfully, every single person that owns and operates one of these has it complied to the absolute letter of the law because you never see any discussion of regulations or people talking about the sins of having any non compliant units. As such, these units, where allowed, would be suitable for connecting to solar inverters and net metering or back feeding.

Of course with the myriad of laws that are basically impossible to satisfy in a lot of places, you couldn't even think about doing this without creating some ethical violation so putting it into practice would be out of the question and should be put from ones mind completely should you live in these places. 
If however, theoretically,   some lawless terrorists wanted to set something up in their back shed to reduce their power bill, they could do so without causing any problems with the grid or compromise it's safety down the line. They may even be crafty and set up some sort of system where they could unplug  their setup or re wire it so that if an inspector should turn up out of the blue as they do to every home 10 times a year, they would have some deniability.
  If they were discovered however, they would no doubt be dragged out of their homes and shot in the street no matter where they lived and condemned to eternal damnation for their sins so no one should ever do anything like that.   

[DRJensen]

I looked into net metering here in florida and in order to comply, your system be accepted and approved it has to be installed by a licensed contractor (absolute BS in my opinion). There is a minimum size for the solar array and multiple other restrictions. I work for a large utility and perform work on electrical systems from 120 VAC to 4160 3 phase. I have no issue wiring the system to code but it must be done by a contractor before the utility company will buy into it. All the red tape involved makes this a real headache and paying a contractor 3 to 5 times what the system really would cost just isn't worth it at this time. Once the price of solar starts coming down it may be worth it and then I can run my little yanny on waste ATF and earn credits with the power company to offset the summer power bills. Why does everything have to be so damn difficult!!!!!

[LowGear]

The problem I'm having with the XW6048 is all the bells and whistles.  How many of the add ons and which ones do I buy?

The real advantage of the Xantrex is the 48 volt operating voltage.  My SMA wants about 300 VDC which is a lot trickier to generate.

If I trade inverters then I have to rewire my solar panels.  My array is 3 by 6.  The other one is 3 by 4.  Biting the bullet hurts.

"If it were easy, everyone would do it."  (you can quote me on that.)  Oh, and "Nice stuff cost more!"

Casey

[mike90045]

The XW system NEEDS the SCP (system control panel) and it's REALLY nice to get the Conext ComBox monitor.  The Combox lets you upgrade the XW firmware, and adjust most of the settings. The SCP lets you adjust ALL the settings, but no upgrading. Grrr!!!

With a wireless router and a 7"android tablet, you can use the combox to monitor and control the system.

Also, getting a Midnight solar E-Panel for the XW greatly simplifies the wiring, it has monster DC breaker, buss bars and all the goodies (I don't remember if it has the AC side breakers with it, or if they are options)

And some DC source and whatever makes the DC.