Awesome! I appreciate the help shortbus.

The wells you have on your property sounds like smaller producing wells than the large unconventional directional wells in the deep shale. I would be interested to see who manufactures those turbines. Also, I am familiar with the "rabbit" concept, but it wouldn't really apply to the larger producing wells as they just push all the liquids right up with the gas.

Keeping this conversation on topic. I will emphasize that I am trying to replace (or at least reduce) the "choke" regulators with a generator. The thought is that the generator can do the job as the "choke" if there is sufficient resistance. The generators resistance would need to be variable. I am still not 100% on how to make it variable, although the article below looks to be on the right path.

http://web.mit.edu/kirtley/binlustuff/literature/wind turbine sys/DFIGinWindTurbine.pdf

 

This is the same as putting a fan in front of a windmill. You are not harvesting energy...........you are just diverting the output.
You are stealing the energy meant to lift...............to generate.

You will have to replace that energy later. And you will have to put more in..........than you took out.

Let's say you have an one hundred foot dam drop feeding a generator. If we divert a stream away and feed a grist mill........are we harvesting energy? No we are not........we just diverted it.

 

OK. Maybe I am wrong, but let me try an example I think is more applicable.

Suppose that a lake is supplying a brewery (I like beer better) and the lake can supply 100 gallons a minute, but the brewery only can consume 50 gallons a minute.

The brewery put a valve/regulator on the supply line in order to accommodate themselves.

What if instead of a valve/regulator they put a generator that is restrictive enough to keep the supply at 50 gallons a minute?

Do they now have free water and electricity?

 

The lake is continuously being filled......or re-charged. Your hole isn't. What ever you use for electricity........is at the cost of beer.
Why is this so hard for everyone to understand?

It's like a battery. It's a certain amount of potential. Only a certain amount. You have to choose what to use it for.

You can't use it twice.

 

Haha. I am sorry this is frustrating for you, but I do appreciate the input and help.

Lets assume the lake is not being continuously filled, and the brewery can only exist for a long as the lake has water in it. Then they have to go find a new spot to brew.

I think that is more applicable to what I am proposing.

Again, in this case the brewery can only use 50 gal./min. while the lake feed in its current setup has the potential to supply 100 gal./min. Instead of wasting the extra 50 gal./min. the brewery decided to install a valve/regulator to slow the flow. Suddenly they come up with the idea to use a restrictive generator instead of a valve that still slows the flow to 50 gal/min, but also powers the brewery.

Sincerest apologies if this scenario still doesn't work, but I am just not seeing how it wouldn't.

 

Generally, natural gas coming directly from a well is 'wet' ... meaning that it contains gasoline and other interesting fractions.
So be sure to have a few fire extinguishers handy.

 

Generally, natural gas coming directly from a well is 'wet' ... meaning that it contains gasoline and other interesting fractions.
So be sure to have a few fire extinguishers handy.

Definitely a concern. Up in the Marcellus it is pretty dry and the choke is currently positioned after the heater/separator so as to not let anything drop out at the choke point.

 

1 + 1 = 2. 2 - 1 = 1. The lake has 10 gal. of water. It will make 10 gal. of beer. The brewery can only make 1 gal a day.......so it will take 10 days.

If you divert any water.....the brewery can't run for 10 days.

You lost beer.

 

The scenario would not diverting any water. The lake flows through a pipeline that can handle 100 gal/min. In that pipeline what water eventually hits the generator/turbine/whateveritisIhaveyettofindout. After the generator/turbine restricts the flow of water enough to get 50 gal/min on the outlet it flows into the brewery for use.

If the brewery didn't have a valve or generator to slow the flow they would still use only 50 gal/min while the other 50 gal/min would be wasted and spilt all over the floor.

 

This beer brewery is ten miles away from the dam. It requires the dam drop (potential) to push water to brewery. If you drop the pressure head.........the water can't get to the brewery. Or you will have to pay to re-pump it. (re-pressurize)

You have no energy to work with in your project. You are stealing potential that is already being used.

You are wasting your time. And the well head pressure potential.

And with that, I will stop wasting my time.

 

Hm, sounds like you are just trying to poke holes in this now that aren't actually relevant. Nevertheless, I appreciate you ending it.

I would like to continue discussions to resolve my original question, as I think the project is plausible.

I would like to determine a setup for a generator that could adjust its resistance based on controller setup. The input variable would ideally be pressure at the turbine outlet which would control how much resistance the generator applied to the flow of gas. Ideally, the more resistance the more electricity generated.

The article below is the most relevant thing I could find. Unfortunately it is a little over my head. Any help is greatly appreciated.

http://web.mit.edu/kirtley/binlustuff/literature/wind turbine sys/DFIGinWindTurbine.pdf

 

I have no knowledge of gas wells (we're still trying to get the general public to accept fracking over here!) but I have to say that Dawsonh4's example makes a lot more sense to me than BR-549's objections. The well is pushing gas out at a higher pressure than the downstream can handle. It is presently regulated using the resistance of restrictor valves. Dawsonh4 wants to replace some of the restriction from the valves by restriction from driving a turbine, which seems perfectly reasonable. In order to maintain a constant downstream pressure given variable upstream pressure, he needs to be able to control the amount of resistance provided by the turbine generator.

The idea of controlling the field current to control the dynamic resistance seems sensible. I don't see a problem here except in one area - and this demonstrates my limited knowledge of fluid dynamics!

If one assumes, for the sake of theory, that the 'turbine' is actually more of a steam-engine arrangement, whereby pressure directly drives the 'piston', then stopping the rotating shaft completely will stop the flow of 'steam' (gas). In a turbine, presumably one could stop the shaft rotating, but the gas can still flow through the turbine. My point is that I am not sure that increasing the resistance on the shaft would actually have a significant effect on the downstream pressure. But somebody else needs to clarify that for me!

 

You might consider using a mechanical governor like on a diesel generator to control an inlet pressure valve. If you are making AC, you probably want 60 Hz anyway.

You gonna run raw natural gas through a turbine for electricity?

The generator doesn't have to be inside the pipeline but, typically the fuel pump for your car uses an open frame motor that is submerged in your gas tank and is cooled by gasoline. No oxygen = no explosion.

 

The generator doesn't have to be inside the pipeline but, typically the fuel pump for your car uses an open frame motor that is submerged in your gas tank and is cooled by gasoline. No oxygen = no explosion.

Not only the fuel pump, which is usually immersed in fuel, but the fuel level sending unit. The sender is most times a open form of a pot, a coil of wire with a carbon brush moving over it, above the fuel level in the airspace when not full.
Never heard of one causing a tank to explode.

 

If one assumes, for the sake of theory, that the 'turbine' is actually more of a steam-engine arrangement, whereby pressure directly drives the 'piston', then stopping the rotating shaft completely will stop the flow of 'steam' (gas). In a turbine, presumably one could stop the shaft rotating, but the gas can still flow through the turbine. My point is that I am not sure that increasing the resistance on the shaft would actually have a significant effect on the downstream pressure. But somebody else needs to clarify that for me!

Or a turbo charger on a engine. The exhaust gas from the engine still flows through the turbo when it's not making 'boost to the intake. The turbo needs to have a larger amount of exhaust gas (close to wide open throttle) before it starts spinning the compressor part of the turbo. Before that happens the exhaust gas still flows through to the muffler, like a normal engine.

 

..............
In a turbine, presumably one could stop the shaft rotating, but the gas can still flow through the turbine. My point is that I am not sure that increasing the resistance on the shaft would actually have a significant effect on the downstream pressure. But somebody else needs to clarify that for me!

Good point.
The device that extracts the energy would need to extract enough energy to significantly reduce the pressure from inlet to outlet, and that could require many turbine stages (such as used for steam turbine generators).
Alternately, a more positive displacement device may need to be used, such a vane or lobe (supercharger) pump operated in reverse.

 

BR-542 has a point that I really think you must consider. I'll describe a system used long long ago in a city far far away (Cincinnati). I was working for G.E. Testing jet engines and their various pieces. One of the tests was to chill the whole engine down to see if it would start. In order to do this, we would flow air through a turbine (supercharger from a B-17) coupled to a water brake (turbine water pump). As we increased the load on the water brake, it took more work to turn the turbine. Since energy (work) is neither created or destroyed (ok... there are some exceptions, like don't try this around a black hole, for instance) it had to come from somewhere. That somewhere was the temperature of the air stream. Using this simple system we could suck enough energy from ambient air to get to -80F.


What you propose is, essentially, the same thing substituting the generator for the water brake. Energy, in this case pressure, will be lost from the stream. It will have to be make up elsewhere as needed. A simple restriction does not decrease the energy in the stream, just the pressure. If there is sufficient surplus in the entire system to make up for that which you are taking with the generator, all well and good. If not, you'll have to pay it back with interest.

 

.....
A simple restriction does not decrease the energy in the stream, just the pressure

A restrictor will reduce the energy of the gas stream the same amount as a turbine would, if the input and output pressures and flow rates are the same.
How could they be different?

 

A restrictor reduces the pressure of the stream under flow. It does not reduce the energy in the stream. If it did, the energy would have to go somewhere. It isn't heat. The potential energy of the plenum is expressed as kinetic in the stream velocity (see Bernoulli) but the energy remains the same. Put a turbine in there and you've got to add energy for things to balance out.

 

A restrictor reduces the pressure of the stream under flow. It does not reduce the energy in the stream. If it did, the energy would have to go somewhere. It isn't heat. The potential energy of the plenum is expressed as kinetic in the stream velocity (see Bernoulli) but the energy remains the same. Put a turbine in there and you've got to add energy for things to balance out.

So the kinetic energy going from a high to a low pressure is converted into useful energy instead of heat.
This just means that the downstream gas will be at a lower temperature than if it went through a restrictor.
The energy to heat the downstream gas back to ambient will be provided by the ambient air around the pipe.
That's where the added energy comes from.