22 replies to this topic

[ToddT]

While this isn't specifically GEK related, I hope y'all won't mind the thread. My goal is to help folks get energy independent. Many states have net-metering available so we can in essence, use the grid as our battery. Make more electricity than we need, feed it into the grid for now and use it later. The end result is hopefully a monthly electric bill for nothing more than some taxes and fees. No kwh used.

Easier said than done.

I've found that generators over 20kw can be controlled with automatic governors to stay in sync with the grid. Power monitors watch the grid and the local genset. When the two are in sync for a split second, they connect and from then on, the computer speed control (electronic throttle valve) keeps the local genset in sync with the grid.

But, the hardware manufacturers tell me this won't work below 20kw due to the smaller sizes of the engines. I can see their point. It would be like running the cruise control at 30mph... always searching for the right speed and fluctuating between wide open and coasting. Maybe a heavy flywheel engine like a Lister or Arrow would work. In any case, the best I can figure for those situations is to borrow some technology from the solar and wind market. That means taking AC power, rectifying it to DC current, then invert it back to AC in a grid-compatible condition (frequency, voltage, phase). However, that market doesn't go much over 3.5kw to maybe 5kw. Stacking these units would run the cost through the roof... as in tens of thousands of dollars.

Any suggestions? I spoke with some power conditioner manufacturers and after explaining it a couple of times, they can see where their hardware can take our AC power and electronically manipulate it to meet the grid. At least their stuff is slightly less than $10,000.

The other thing I've been thinking about is that a "store bought" genset will have an engine and generator head engineered for a specific fuel. The general rule of thumb in the woodgas world is to cut the horsepower by 35% or more. That means right out of the box your generator isn't putting out as many kwh as you paid for. Plus, if we have to buy power conditioning equipment in order to connect to the grid, we're likely wasting some power conditioning hardware already installed by the generator manufacturer.

What about buying components and putting together a system designed for woodgas operation? Start with a gasifier designed to run a specific engine. Then buy a generator head based on the horsepower that engine is running on woodgas. From there, take the raw AC current and send it through the power conditioning equipment that in turn cleans it up and gets it in sync with the grid. It seems a bank of capacitors could give us a small buffer for momentary fluctuations in power output.

I know that one way or another we can connect smaller generators to the grid. It's just that the market for this specialty application is so small, the manufacturers haven't responded to it yet. Therefore, there is no "off the shelf" solution available. Therefore... we need to create our own shelf. Suggestions?

[Dutch John]

Hello Todd,

Perhaps we should view this in a broader prospect: Woodgas for electric power generation in general.

The very, very first question you should ask yourself is: how much wood can I get, log, transport and chip or chop. How much does that cost in money and labour. Is it worth the fuzz. It is a question mostly saved for later, when there is no way back.

When I drive for an hour, I need 2-3 sacks of wood. Over a year that is a huge pile. Logging and splitting by hand will take you a few days to gather this pile. Chipping asks for an expensive machine. Chopping for many days. Sure some handymen like Wayne Keith make their own chopper, but at the moment he is one of very few who actually did.

When I mow the lawn for an hour, I use 3 double handful of chips. The fun/woodconsumption ratio is way higher than on driving!

Back to electric power by wood. In my opinion there are several solutions, but if cost efficiency is taken in account, heat recovery (CHP) is a must. Otherwise you are generating very expensive power. Only if the power is needed for emergency or you have enough time and money to waste, you can skip the heat recovery.

If you want to earn money with power backdelivery, small applications will not be effective and small ones tend not to be very reliable. Unless you have no big customer in the neighbourhood that wants the buy the heat from your several 100 kWe setup, it is a no-go. Not even to mention where to get the wood from.

A GEK can deliver enough power to generate a few kWe. Enough for most homes. The corresponding 8-10 kW thermal heat fits also. You could connect the unit to the grid, using it as a huge battery. But I'm not so sure if the small bit you deliver back will pay for all the fancy controls you need to get it safe and sound. An synchonous generator needs a lot of expensive fuzz for automatic coupling to the grid. An a-synchonous not, but it has the disadvantage that cannot selfsupply; it needs the grid.

So many decisions to make. I made mine. The above mentioned 1-2 kWe installation. Running in wintertime in the late afternoon and evening when we need most heat and electricity. And for emergency. No coupling to the grid. No fancy electronic controls, just a switch to choose between grid and generator. No auger feed, just day batches. But with heat recovery from engine and ready gas. Gas generator fully insulated. And of course the Pyrocoil.....

Regards,
DJ

[ToddT]

Thanks for the reply. And yes, I've considered the rest of the scenario including feedstock supply. Living in the deep south, we have plenty of wood available. Storm debris alone would power a gasifier for years... of course with the appropriate stock prep.

For sure, the cogen side is critical. Why waste heat? Along those lines, I've been looking at absorption cooling as an alternative to electricity-hungry air conditioning. I talked with a guy just last week who has one of the old style gas air conditioners. We need cooling about two or three times as much as we need heating.

I've heard from two or three sources that 1.2kw per hour is the average household consumption in the United States. Not peak demand... but 24/7, 365 days a year. Maybe one route to take is to get a solar system that can accept AC input (many can take in AC or DC). Use the inverter/controller from the solar system to tie to the grid.

Considering the grid intertie hardware and the process control equipment required on the generator, what do you feel would be the smallest generator that could be realistically connected to the grid? We "can" do just about anything but what's reasonable? I've seen a 25kw installation but that was at a research facility. Again, don't consider the feedstock. Assume that is already taken care of.

[bchovnick]

The Weberke generator we use is 5.5kW has an electronic governor and has no problem staying right on the 1800 RPM mark using syngas. I'm sure we don't get 5.5 kW, but we certainly stay in phase.

[randymax]

i am glad you asked the question as it is also my interest as well.
i don't know of this book but it might be of interest to you.

http://www.utterpowe.../home_power.htm

[Steve Unruh]

Hi ToddT
You have actually answered many of your own questions as long as you do stick to the stated core value of your quest, "My goal here is to help people get energy independent." Drifting from this into a "Storm Damaged Reclaimation'',"Waste to Power","I want to contribute to the new Green Smart Grid movement", "I want to save money on my power bill money" are all different concepts that will drive you into different solutions.
Personal info from me and a combined 4000 member input off of three alt-energy site confirms the minimal/planned North American house hold electrical usage to be an hourly base line of 1kWe to 7kWe that can have peaks of 5kWe to 15kWe depending on water heating/cooking/washing-drying/AC loads.
Of the 4000 those who remove these heating/cooling loads from the electrical supply, they have found they do not even need a grid tie-in at all and enjoy the greatest independence. But they must be physically fit enough, smart and self-reliant enough to fuel, operate and maintain all of thier systems for thier total daily needs. This will always be a specific site specific build up solution requiring thousands of hours and/or dollars to build and design and then hours daily input to operate. Fuel/labor economy will be the #1 cost/expense factor.
Of the majority of the 4000 like Dutch John and me use a home power system to back up the Grid and reduce their daily Grid energy usage we still have independence in the form of the manual control of the mandatory grid tie transfer switch. This can be a total system when bought new as low as $5000. USD solution - used, traded skilled for less. Literally a person in a wheelchair with thought and design could operate this. Still when in use will require a daily input in hours to fuel and maintain. So I have working down to 1 hour a day for space wood heating labor and am working toward a matching daily 1 hour for self generated electrical supply. Fuel/labor daily input is my #1 design factor.
How do we compare Dutch John? Bruce Chovnick?
Of the handful in the 4000 who have chased down and sometimes captured an elusive home power net-metering grid tie-in (to use as a battery/to save money) IF DONE LEGALLY, they have usually had to spend an additional $15,000. USD for the permits, engineering, inspections and certifed/approved equipment. They will never see a payback in these costs.  AND NOW AS A REGISTERED SUPPLIER THEY HAVE SOLD THIER INDEPENDENCE AWAY.
So says this guy who has stood down in a ditch overseen by a man with a gun, another man with a court order as I forced to chop out a 40 year old, 3 foot (1 meter) section of personal water well supply line to our two house "illegal water service" so we could only then use the monopolistic "inspected/certified' public water supply. If we had never hooked into them 2 years prior as a water supply back up to our own well. . . . some decisions cannot be reversed. In the end we won back the ability to use our "well water for gardening purposes only".
Regards
SteveU.

[ToddT]

Thanks for the book suggestion, Randymax. I bought the CD last year but misplaced it. I ordered the book and the CD tonight... really looking forward to checking it out.

[katana0182]

I'm not sure of this, but I've done some research in this area, so I hope I'm not talking complete nonsense. This being said, this may not be fully correct, so don't assume it is...

It appears to me that the least complex home power systems are those that are isolated from the grid (for obvious reasons). Next in simplicity are backup-only systems without net metering. Next comes net metering systems with no backup capability. The highest complexity home power system is one with both backup capability AND net metering.

A key thing with most net metering setups is that you throw your lot in with the power company in terms of blackouts, most of the time, unless you're willing to pay for some very sophisticated equipment. And, in the event of a blackout, problems may occur with engine-powered generators due to their large number of moving parts - thus leading to a potential upset of the engine or generator if there's a sudden blackout. Small-scale solar panels, wind, and hydro are much better at this sort of thing.

On top of that, if you're thinking of a joint net metering/backup solution - the equipment comprising it has to be smart enough to recognize the signs of cascade collapse of the grid and disconnect from it prior to that collapse occurring, or else the engine/generator may be damaged and you might lose your backup due to the large number of moving parts in the engine/generator rapidly decelerating. (Or you can use a very robust engine and genset, perhaps the gaseous fuel equivalent of an OEM Lister CS - maybe one of those Arrow Oilfield Engines - nice, nice piece of kit, that - with an overspeed trip, and a torque interconnection that will disconnect in an orderly fashion if there's too much torque put on it by the generator.)

In addition, with net metering, the system has to be smart enough not to reconnect to the grid prior to power being restored, and to only provide power to your home.

Grid collapse takes place as a process like this:
1. Usually, the independent system operator (ISO) can detect the signs of byzantine failures in the grid leading to cascade collapse, and shed loads (rolling blackouts) to maintain grid stability, but sometimes it can't.
2. In this case, the grid interties begin manually or automatically breaking up the grid into individual pieces to protect the power plants in a process called grid islanding, where individual power plants are assigned to loads sized to them.
3. If the interties don't break up promptly, and it takes usually a definite period of time for them to do so, then the power plants have to island themselves - disconnect from all external loads by tripping their turbines - and this results in an emergency power plant shutdown.

With an AC generator on the grid, you're a power plant, albeit a small one. Thus, your system has to be able to promptly "island" your home from the grid,  if there's say, a frequency disruption or a massive grid undervolt, or else damage can be done to an improperly equipped generator. The reason for this is that if the grid dramatically and suddenly undervolts, and your generator is running at full speed, without automatic islanding, your generator is "just another brick in the wall" - along with every other power plant, or at least those that don't automatically or manually island for their protection. Your generator will therefore try to power the entire grid. It will be unable to do so, and will come to a sudden halt very rapidly. This could cause damage.

Further, your equipment has to be smart enough not to connect back to the grid UNTIL full power is restored. This is to prevent your local linesman from getting electrocuted if you're putting electricity on the local loop while the grid is down. This has happened before with home generators, when people plug them into an outlet without any sort of grid isolation switch.

But there is good news. Equipment is out there that's smart enough to do this. For example, Xantrex makes a series of solar inverters that can rely on inputs from batteries, solar panels, generators, and the grid, while facilitating net metering. However, it's costly, and it's optimized for the solar market. I'm not certain whether it can even use an AC source to feed into the grid, too... I think it can only use solar or battery only to feed in. You might have to rectify the generator output then feed the DC into the inverter and pretend it's a solar panel array. This will cause loss of efficiency, as both inversion and rectification are power-negative, of course.

Also, though the Xantrex solution is modular and scalable, it's meant for low wattages, so multiple units are required if you have a generator bigger than a few thousand watts. It can scale up to 3 units, for a total of 9000 - 12000 watts, if I remember correctly, with each unit being $2500 each, base - though there are lots of accessories I believe you need to buy.

If you were thinking about doing a DIY solution, I'd have to guess that there's little to no chance that your power company will allow it - as they don't want their linesmen getting electrocuted, and they don't want to be liable for your equipment getting all fudged up in the event of a grid collapse. Suffice it to say that you might be be up to your neck in red tape, getting permits for permit applications, and approvals for certifications of listing permits, if you don't use a stock solution like the Xantrex.

To save you money, what you might consider is a mode-switched setup, where you can either power your home by the generator, or by the grid, but not both at the same time; you might switch between the two by manually activating a switch, or the like.

[jimmason]

thank you all for this thread.  its a critical one.  sorry i've been absent.  it is difficult to keep up at the moment.  please carry on without me.

there are several gek owners exploring grid tie installations for net positive metering.  where this is legal, the numbers can work out very attractively for a relatively small scale gasification system.  guy robinson and don larson are pursuing this with focus in minnesota.  guy, post your things here, will ya!  skip in hawaii has similar goals.  tony prats in spain also.

remember that the basic gek unit can be made to do around 20-25kwe, assuming a relatively open void space fuel, and using a larger reduction bell than we deliver stock.  for $2400, this is somewhat like buying solar pv panels at 10 cents a watt.  add all the other heated augers, pyrocoil and electronics and you are still at 20 cents a watt.    

of course this is a very apples to oranges comparison, and the gek is not yet a turnkey and go solution, and the raw peak watt rating of pv is not terribly relevant to cumulative power generation over a 24/7 cycle, but nonetheless, the numbers suggest the tremendous potential of low tech steel tanks with some esoteric configuration and approximations of fire inside of them.  the end economics of this scenario are deeply attractive, and with upfront costs that do not require a mountain of govt supports to make it go.  this of course is why i do this.  when we get all the details worked out here, it will be difficult to keep it all from going viral.

however, the grid tie is more difficult than pv.  or rather, pv generallly creates so little wattage that the grid tie is not that significant of issue in relation to the raw panel cost, and can tolerably be handled with inverters.  when looking at 10s of kw of inverter capacity, costs get rather significant.  the xantrex solution above is about the best, and it is about $500/1kw.  there are larger grid tie only systems that support commerical size installations, but the price point seems about the same.

at one point i built a 33kw off grid system that also could be grid tied with the basic xantrex sw5548 inverters.  it was two stacked on each leg, then hacked internally to be maintained in parallel 3 phase orientation.  we ran the shipyard/allpower labs facility off grid for six years on the resulting "powertainer".  17,000lbs of batteries for 5000amp/hrs at 48vdc of reserve.  see here: http://www.flickr.co...57594062314269/

in short, you do not want to do the above.  it works, we could start 15hp lathes and mills on inverters, and weld till berkeley issued us yet another citation, but it was a giant hassle.  (nonetheless, i still have the batteries.  anyone want them?)  smaller battery based off grid systems are more tolerable, but batteries are always a difficult proposition, and require a level of care similar to troubled teenagers.  the grid is vastly simplier if you have it and can use it.  but of course there are other pleasures to be had by doing it all off grid.  i personally loved being fully off grid in the middle of a city, doing things far beyond what one should really try to do off grid.  nonetheless, it was a joy not always shared by others who had to use the system.

in principle, a grid tie with a spinning generator is not difficult.  you can do it with a lightbulb and two wires to find the match between legs before you throw the switch.  bruce jackson is currently giving a good primer of this scenario over on the wood gas list.  see here: http://tech.groups.y...s/message/22031    the protection logic to prevent islanding is not difficult.  and the danger to linemen is way overstated and mostly a ruse of the power companies to make grid tie more difficult.  the problem in all this is doing it legallly and generating the needed ancillary paper.

todd, i would like to hear more specifics about the power condition eq you are finding in the $10-15k range.  if such will support the 50-100kw range, it starts to be price attractive.  i haven't found any good small scale automated synchro scope and protection equipment.  synchro scope is the term for how this is usually done properlly manually.  guy robinson and you aparently have.  do tell the secrets.  

there has not been much market to date to do this at a small scale.  many of us need it and wish there was a market here already.  assembling the best currently available products would be highly helpful.  at some point we may go and make this device specifically for the under 100kw genset scenario.  but in general govt certification scares me, and i will always try to roll that stone last.

the capstone microturbine is the closest parallel problem and they chose to do it with an inverter grid tie.  they also chose to do many things at a very high price point, mostly to generate press on their exotic equipment and thus juice their stock price, but nonethelss, they came up with a very impressive rectified alternator to inverter to many flavors of ac grid tie out.  we have one sitting in our shop and it looks like this was a capstone rolled solution.  it was not an already existing product, sadly.

so what else is out there?  it would be great to assemble a more specific list of equipment options here.  can those who have links post them?

jim

[ToddT]

By the way, the states that allow net-metering have very specific rules... with good understanding. It is crucial that our genset disconnect from the grid when the grid goes down. Otherwise, we could put an unsuspecting lineman at risk of electrocution. This happened in my town a few years ago during an ice storm. Somebody connected a portable generator to the house. Then a worker went out to work on the downed line and was killed. No need to repeat that tragedy.

I've found some solar inverter/controllers that allow AC as well as DC input. This will be my research project for the week and I'll keep y'all posted.

Jim, I found one power conditioner equipment provider who at first didn't think his stuff would work but when I explained it a little further he said it should work. His equipment was $8900 for about 12kw to 15kw... if I remember correctly. Again, I'll nail down some ideas and post an update.

[JayMart]

I looked into some aspects of this a few months ago, so I don't remember all
of the specifics. Most grid connections require a series of about 6 relays. These relays include under-voltage (27), over-voltage (phase to ground) (59), over-voltage (zero-sequence) (59G), over/under frequency (81), sync'd phase (25), and an ac directional overcurretn (67) or directional power (32).
In addition overcurrent relaying is needed (either 50/51 or a 50/51G). I found 2 or 3 vendors that provide an all-in-one solution for these realys for around $1000. With the use of an induction motor/generator, the phase should lock to the line.

The other solution is to use inverters. Honda uses these on their smaller generators and even allow you to daisy-chain them together, syncing the phase of all of the inverters.

Just throwing out another data point

[HHO BASTER]

JayMart said:

I looked into some aspects of this a few months ago, so I don't remember all
of the specifics. Most grid connections require a series of about 6 relays. These relays include under-voltage (27), over-voltage (phase to ground) (59), over-voltage (zero-sequence) (59G), over/under frequency (81), sync'd phase (25), and an ac directional overcurretn (67) or directional power (32).
In addition overcurrent relaying is needed (either 50/51 or a 50/51G). I found 2 or 3 vendors that provide an all-in-one solution for these realys for around $1000. With the use of an induction motor/generator, the phase should lock to the line.

The other solution is to use inverters. Honda uses these on their smaller generators and even allow you to daisy-chain them together, syncing the phase of all of the inverters.

Just throwing out another data point

Could i use a UPS, i just got a 1500 watt one for free, it uses large gell batteries but if i feed it 12 volts from a truck alt would that do it

Thanks Gary

[katana0182]

I read my local power company's docs on interconnection.

I'm in Massachusetts, and they're pretty good about net metering, and interconnections, and stuff like that. Probably one of the easier states to work in on distributed generating.

It isn't that bad, especially if you're using approved equipment, you're in a decent location, and you aren't trying to throw too much power out there at once.

What I'm looking at is here, if you want to download it.

So here's the process...
-------------------------
The easiest solution is use the "short form" (= 1040 EZ, single page, minimal fee). To do this, you have to stay under 10 KW if you're single-phase and use an inverter.  If you're three-phase, you have to stay under 25 KW and use an inverter. If you use an inverter, it has to have passed UL 1741 ("Inverters, Converters, and Charge Controllers for Use in Independent Power Systems").

If you pass under the "short form", interconnection costs are trivial, unless you're in an area that has a really obsolete grid. This isn't common.

The "short form" process takes 15 days in my state, Massachusetts.
-------------------------
Otherwise, you have to use the "long form". There's the 'short' "long form" and the 'long' "long form". The 'long' "long form", you don't want to go there, probably. But the 'short' "long form" is worth considering...
-------------------------
The 'short' "long form" (= 1040A) is still pretty easy:

To use the 'short' version, your equipment has to qualify under 1 of the following:
*you're using an engine-generator listed under UL 2200 ("Stationary Engine Generator Assemblies")
*you're using an inverter listed under UL 1741 (greater than 10/25 kw, otherwise, you get to use the "short form")
*your facility or equipment has certification from a nationally recognized testing lab that it's in compliance with IEEE 1547/1547.1 ("Interconnecting Distributed Resources with Electrical Power Systems")
*your facility or equipment that has been previously approved for interconnection in California or New York, in compliance with those state's standards.

Then, somebody from the utility reviews your plan - it has to meet 4 additional criteria:
*Starting Voltage Drop (applicable to synchronous generators only, inrush current limited)
*Fault Current Contribution (not more than 10% of max fault current on 3-phase circuit potentially contributed by generator, won't cause circuit to exceed 85% of short circuit interrupting capacity on either 3 or 1 phase, and if on 1-phase, total generating capacity won't contribute more than 2.5% of short circuit interrupting rating for 3-phase circuit)
*Service Configuration (isn't single phase AND has more than 20 kVA generating, if on 240 v center tap neutral, won't cause variance more than 20% over transformer rating)
*Transient Stability (won't exceed 10 MW except for special locations near substations)

If it fails the 4 criteria test, then there's a $1250 Supplemental Review charge, to determine if there are workarounds that can be made. If the facility passes the 4 criteria test, or the Supplemental Review test, then it can move on to see how much they'll have to modify their lines to interconnect you.

This probably won't be much, especially if you're already on 3 phase service, for the kind of loads we're talking about.

The 'short' long form has costs in the low thousands (1K - 3K), but it's probably doable for a single person operation in a decent location. You might have to get a 3-phase connection, but you can become a generating plant.
-------------------------
The 'long' long form...forget about it, unless you've got a sizable commercial line of credit. With no personal guarantee, lol. ;-)
-------------------------

So the conclusion that I'd draw is that this is doable. Especially for 10 KW or under, with an inverter. If it's over that, then some work might be required, but it's still doable with a UL listed generator and a three-phase connection.

If Team GEK wants to roll it's own custom solution, so to speak, some help from an electrical engineer who can stamp plans, and a power company (or a municipal utility, probably a lot more flexible) willing to work with you could be the keys to getting that first certification in New York or California. Then, it might be clear sailing ahead.

Go for it.

[claybj]

We have been quoted around $11,500 for a grid tie system that load balances the grid w/ our 30kW gek-350chevy unit.  Basically, if our unit isn't providing enough "power", the Grid picks up the slack.  The problem inherrent with maintaining consistent power/speed with this type of gek-350 configuration is being tackled w/ voltage regulation.  Inconsistent engine speed is offset w/ voltage regulation to match the grid.

This configuration is quite a bit more expensive than DIY, but we put out power at far less than the $.11 our utility charges.

We've put our meters on a myriad of ICE gensets and it is literally impossible for them to maintain consistent electrical power with ICEs w/o the use of AVRs.  The idea that you're going to achieve exactly what the utility requires by maintaining 1600rpm or 1800rpm with ONLY a gek & ICE combo is a dream.

GEK users... making power for consumption isn't that difficult.  We spend hours looking into the truly difficult "problems" like the chemistry of various biomass types and the physics of how an imbert "works".  Compared to that, making power for consumption by business, residence or grid is a walk in the park.

“No great discovery was ever made without a bold guess.”
-- Isaac Newton

[claybj]

Let me make one more comment.

In order to make the most of a GEK-ICE combo, you need to dump all power to a customer or the grid.  This is the biggest problem for creating an off-grid system to run a house or business.  The GEK-ICE combo must be tuned for maximum output, or you'll waste a huge percentage of biomass/fuel, thereby making the power you create more expensive than simply paying the local utility.

[oldchuck]

This is a very helpful and informative thread. Please continue.

[ToddT]

What did you find worked to match the frequency between the grid and your local genset. The electrical engineers I've spoken with say that is the big issue.

Some have said to run the generator at slightly above 1800rpm (for 60Hz application) and essentially dump the excess voltage, I assume through the AVR.

Can you give us any more details about the setup they proposed?

[claybj]

Todd...  I would love to give you an answer but I can't.  We are looking at a wide variety of AVRs for our unit presently.  We're seeking an AVR with the widest voltage adjustment range that doesn't cost an arm and a leg.  Plainly, if engine speed drops too low exceeding the maximum voltage drop supported by the AVR you've got problems.  Finding an AVR that can handle the maximum fluctuations of our GEK-ICE combo is critical.  Cost is always important.  I'll keep the board updated on our progress.

[jpoteet]

Hello Everybody,

I have yet to get a GEK, but am currently tied to the grid with an induction generator (fancy term for used single phase squirrel cage motor I bought used for $60).  It is very easy to bring online, and I actually adjusted the governor speed on my stationary diesel using only an ammeter.  As RPM increases above rated unloaded speed (e.g. 1800 or 3600 RPM depending on motor), the motor turns into a generator and is automatically synchronous with the line because the line is what energizes the fields.  Don't spin the motor too fast or it will generate too much current and the thermal breaker will trip (if it has one -otherwise motor will burn up).

Induction generators are widely used in wind turbines, but they have to have special controls there to ensure they are spinning fast enough that they act as generators instead of motors (which defeats the purpose and draws power from the grid to turn the windmill as a fan instead.)  With an internal combustion motor GEK combo that can be governed to a minimum RPM, this type of setup should be a piece of cake.  If total speed control isn't possible, perhaps match combustion engine hp to motor hp to ensure good results.

Only drawback I have so far is large single phase motors aren't that common - I'm running a 5hp with fairly low power factor (.56) so can only push back actual power of 2.25kw.  I'm currently looking into higher power factor or running 3ph motor adapted for single phase grid.

Hope this helps everybody.

[jpoteet]

Hi Everybody,

Just wanted to let you know that I recently upgraded my induction generator grid tie system.  The new generator is a 3 phase 10HP squirrel cage motor with internal wiring in the star (Y) configuration.  Power factor is increased from .56 on my old unit to .81, resulting in much greater efficiency in addition to the increased size.  My GEK is still in production so I'm running off vegetable oil for now.

I tried many different configurations to make use of the third phase on my single phase service, but eventually settled for using only 2 wires, which allows for 2/3 power in a star configuration.  Unit is very easy to bring online and is capable of pushing up to 5kw back into the line as registered by the meter (closer to 6kva apparent power).  Now, my meter runs backward most of the time and I can run the generator less often.  I'm grid connected in California and so far the power company hasn't said anything to me.  I'm careful not to generate more than I use though, and I am careful about safety.  As long as there isn't any capacitance connected to the generator (including run capacitors commonly found on some motors), the unit takes itself offline in the event of a power failure.  Unit is always in phase even if rpm varies somewhat so it's easy to live with.  Voltage is also automatically regulated by the line, but maximum current needs to be monitored to prevent burning up the generator.  And I only spent $150 for this second hand motor - probably a savings of over $10k compared to other solutions.....