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Question on wind generators and power company

viper

Titanium
Joined
May 18, 2007
Location
nowhereville
We will be buying a chunk of land soon for a shop in a rural area and had planned to assemble a couple large (maybe 100-200kw) wind generators mostly to supply our shop and other stuff but wondering how this could be connected to the local transmission lines and "if" they buy the KWs, what rate that might be? We have Westar Energy in Kansas. I seem to remember a max amount they would buy back or something.

I was also interested to learn who governs what regarding power quality, installation and such? If I understand commercial WGs, they just go off line if wind is not high enough even though they spin? They are made to internal regulate voltage over a certain rpm so no need for inverters, batteries and all that?
 
The simplest wind generator is an induction motor.

it is self regulating, because if you drive it a little faster than synchronous speed, it will generate when connected to the grid, while absorbing as much power as you have.

This works because the 'grid" is "stiff", meaning that it won't change voltage much if at all, even when you dump in power. So the "generator" will take in as much power as the prop can supply (in a correct design), and dump it onto the grid without allowing the prop to go faster.

The prop pitch can be adjusted to achieve correct speed in many different wind conditions, and also to avoid trying to absorb too much power, which might overstress something mechanically or electrically, or possibly cause the "generator" to break down the torque and overspeed, which causes electrical and mechanical problems.

No need for anything but some means to control the electrical connection, and to bring the motor up to approximate speed by motoring before letting much wind power through.

Laws? They vary by state. Despite any law, the powerco can make it hard for you by for instance requiring a particular very expensive automatic safety switch, even though others might also work. Nobody will spend 10 to 50 grand on a connection switch without having serious power to put in. Plus, there are all sorts of IEEE standards on what needs to happen, and how, in case of power failure, etc.

And, in the end, you may pay for power at retail, but sell it at wholesale, meaning you lose out.

best idea is to generate to offset your own usage, and never put any net power out on the lines.
 
Your position is well taken on hooking to the power co. I guess our only real reason for looking at it was a way to recoop our investment in the generator. They are NOT cheap and I bet even if we build one, it will hurt quite a bit in cost.


So you are saying most of the commercial units are simply induction motors with means of variable blade pitch to adjust the synchronous speed? I also wondered about the height of the unit relative to the FAA guide lines.
 
Wind Power

One thing to remember is you, as an individual will not win. Typically the power companies will pay a little under what it costs them to generate power. In Texas the power companies not only discount the purchase they make all the other customers pay for the income they loose by not generating the power they purchase.. Maybe you should consider going off the grid and generate your own power which would require large storage battery capability.

JRW
 
I think our thoughts were that if we connected to local 3ph and then "sneaky pete" hooked up to them, we should be able to bring the consumption to a stand still plus be able to have power when we do not have wind. Not sure if I mentioned this would be for our machine shop so we will need some real power. Not sure if batteries and a VFD could do it.

I am open to anything and if the thing could charge all night and keep us going all day, there we go. Guess I might need to talk with the power company and see how bad they will screw me for power. I understand what you are saying though; why not store the power in batteries than give it to the PC for peanuts...
 
Your position is well taken on hooking to the power co. I guess our only real reason for looking at it was a way to recoop our investment in the generator. They are NOT cheap and I bet even if we build one, it will hurt quite a bit in cost.

The motor is fairly cheap, but the gearbox, tower, and prop will be more expensive.

So you are saying most of the commercial units are simply induction motors with means of variable blade pitch to adjust the synchronous speed? I also wondered about the height of the unit relative to the FAA guide lines.

Yes, essentially...... although they are probably optimized for use as induction generators.

The pitch is really to keep blades set to put in power, because you have to "push" the motor faster than synchronous in order to generate. So in light winds, blades are flatter for higher rotation speed, in strong winds they are set more in-line with wind.

if you do that wrong, you will have a huge motor-driven fan, not a generator!

The FAA stuff I don't know about. The blades extend above the fixed tower, which makes lights an interesting issue.
 
What an I missing here? You guys keep talking about batterys, batterys are D C everything in my shop uses A C, and I bet its the same in your shop. That is one of the problems with wind power, no way to store it for when the wind is not blowing. you can't just switch a power station on and off as the wind comes and goes, it can take days to ramp a power station up to full power output.
 
Net metering laws and other stuff...

Okay, first of all, if you're talking about putting up two 100-200kw wind turbines, AND you want to be able to market your power back to the utility company, better to save the investment of two, and just put up one turbine of at least 1.5Mw. The biggest investment starts with the foundation and power handling infrastructure.

Next, read up on your state's utility laws- look for 'renewable energy' references. Virtually every state has some sort of provision for granting tax incentives for a utility company's sale of electricity SOURCED from renewable generation... meaning, hydroelectric, wind, solar, geothermal, etc. This is why many electric utility companies have installed a few wind turbines, but MOST will simply BUY power from hydroelectric authorities and managed 'wind farms'. They re-sell this power, and claim their credit.

Next... realize that by attempting to connect to the utility grid for purpose of putting IN power, that makes you an "Independant Power Producer"... you're an electric utility company. That means your utility company now becomes YOUR customer for those times when you HAVE power to sell, and you become THEIR customer when not. Your utility company probably has a substantial host of 'rules', and unless your state has passed 'net metering' laws, they'll highly discourage having you as both a supplier AND customer.

Net Metering- that's when the utility company lets you 'hook in' your generation system using a 'simplified' system, in both electrical technique, and in business policy. If you have a turbine that provides substantial power say... three days a week... for that three days, your meter will turn backwards... and in the other days, it will spin forwards (perhaps not physically, but that's the concept). In effect, you only wind up paying for what you USE, because when not, you're offsetting your use by what you put back. Net metering in this fashion facilitates a more-palatable business scenario for utility companies simply because they're absolved from having to differentiate between what you've supplied, and what you've used... and furthermore, they're usually 'more free' to get your power at a more profitable cost to THEM... this is primarily because many regulations allow RENEWABLE POWER prices (on the live-utility markets) to be a little bit, and sometimes alot higher than fossil or nuke.

It also makes it easier for utilities to make simple billing- you pay for what you use, and what you generate in excess, gets sold as regular utility elsewhere, and the power-value gets 'banked' for the times when you need it back.

Now, if you want to use that free wind, can put down enough coins to buy a 20kw+ turbine and it's foundation, you can bypass all the garbage and simply make best use on-your-own.

How?

By converting it to something you can either use immediately, or store later. Yeah, batteries come to mind, but when you've got a windy day, and the batteries are charged, you'll end up losing out on good opportunity.

So how?
First... set up your shop so that you can transfer SOME of your electric loads from utility power to the wind turbine. Preferably steady loads, 'cause you'll have steady winds.
Next, put it where it'll count the most. Let's say it's wintertime... wind is blowing, and you're burning natural gas, propane, heating oil... whatever... Instead of doing that, have the generator run a big resistive heater... heat water to warm your shop floors... and in turn, save money on fossil fuels. Let the turbine run your lights at night, and during the heat of summer, run the blowers and compressors of your air-conditioning system. Again, put these (all but resistive water heaters) on transfer switches, so you can switch back to utility mains when there's no breeze.

What you'll find, is that you'll get the highest full-load use of your wind power, when it's most available... not in dealing with selling back electricity, but by reducing the purchase of fuels. By side-stepping a whole mess of regulations, policies, and investing in a whole bunch of ridiculously expensive switchgear, metering equipment, insurance, and paperwork, your gross investment will be much lower, and you'll be making best use of every last watt your turbine can generate.
 
The foregoing is an excellent idea.

it is really too bad that it will not work both ways.... standalone or grid-tied, at choice..

At least it will not work with an induction generator. They REQUIRE to be connected to the grid in order to generate, because the grid provides the "field" or magnetic input to the generator. The wind provides the power to overspeed the motor and allow the "back EMF" to push power into the grid.

But without the grid, the generation is lost. Yes, you CAN make a self-excited induction generator. But the frequency reference from the grid is lost, and the voltage regulation is tricky, speed and frequency dependent, etc, etc.

So to do that, you need a more conventional generator, and batteries etc and/or an inverter to make AC from DC, or make stable AC of a usable frequency.

The induction generator is rather efficient, in large sizes, but the AC to DC and back to AC system is rather poor in efficiency by comparison. To say nothing of the added complexity.

if you DO want to sell power back, net metering or whatever, you will, with the DC plan, need a "grid tie inverter" (GTI), which makes the 3 phase AC.

However, the "GTI" also SHUTS DOWN if the grid goes down, that is a prime PowerCo requirement to prevent "islanding" and danger to linemen. It also prevents problems due to slamming the line back on at a random phase that may not agree with the GTI. That is programmed into the GTI controls. Many, like Cutler-Hammer, have no provision for switching modes, they are one or the other, a GTI or a standalone, different programs in the controller.

You will then need to re-program it to be a stand-alone inverter to use power locally, then re-program again to return to grid-tie usage.

So you are better off to decide to JUST make power locally, for yourself, as described above. That means some form of tightly controlled generation of AC, NOT the fickle winds..... likely AC from turbine to DC to AC again through an inverter.
 
I will agree with you JST, double conversion of the power does not make efficiency sense. We are in process of designing a new shop in the country and plan was to make provisions in the floor heat system to both heat water electrically and with an oil burner. Either way, we know climate controlling 12,000ft year round can prove costly so investing in wind energy might be a smart investment.

However, I am still wondering about what the power company "should know"??? If their meters will not even register return power, I would tie in and protect the system with the GTI. I will say I am NOT looking to create a hazard here but as long as what I do is safe practice, I see it as a way to reduce or nearly eliminate my bill.

I can just add more electric devices that would normally be gas like a home furnace. Problem is big wire is DAMN expensive anymore. In regards to the structure, We are structural engineers by degree and have some good ties in commercial construction so was really thinking the vertical mast and concrete base should be a walk in the park. I have not put ANY numbers together but was hoping we could get that portion built for under 10K. It may be cheaper to buy a head though. Any ideas on where to shop for those??
 
There is a shop at Iowa State University, Iowa energy center. They have done work on wind energy power generation with people that want to just lease the space for a turbine, own the trubine and sell power and people that want to own the turbine, use some of the power and put some on the grid.
http://www.energy.iastate.edu/renewable/wind/

They have worked with projects that the owner wants to just sell power to utilities. The tough part about that is that a utility is bound by law to buy the cheapest source. Because wind power is unpredictable as to when it is available, it is priced at the cheapest per unit all the time. About 3 1/2 cents / kwh.

Also, projects where the owner buys a considerable amount of power and wants to generate some or most of his own power. That is called "net metering". Because you can't predict when you will have wind and excess power and when you need more power than you can generate. The utility takes the power when you have excess and gives it back when you don't have enough. The good thing about net metering is that if you have put kwh's on the line, you can get the same amount back whenever you need. So, if you put power on the line that is worth 3 1/2 cents / kwh and you need power when it is worth 12 cents, it is just a trade of kwh's. The energy center has worked with hog confinement owners that need fans all the time. The turbine produces power at different times than the need for power so the net metering works pretty good.

Turbines are a high capital investment. The supply demand thing right now makes it a sour time to be buying. There are tax credits available that an individual can't use very well. A lot of projects are owned jointly by an organization that can use the tax credits better.
 
As far the efficiency, it is lower, but it beats nothing, you know. I'd be more concerned about the complexity.

The nice thing about the induction genny is that it pretty much quits if the grid quits. That resolves most issues of "islanding" and hazard to linemen. If you have a high local load, it might actually generate for a while at least, and that might be an issue, as the frequency may wander off etc.

If you were not overly concerned about rules and suchlike city slicker garbage, you might put up an induction wind genny sized for your load, and use the power without telling anyone about it. But you'd want to be darn sure that the power goes down with the grid, or that you are safely disconnected. Otherwise there would likely be trouble.
 
I wouldn't...

I wouldn't hook any kind of generation into the utility without letting 'em know, and without jumping through the hoops and setting up everything to do so.

It's not a matter of if... it's a matter of when... They WILL find out about it, and when they do, they'll pull your meters, and possibly even drop the wires, and rightfully so- they could have maintenance activity going on at ANY time... you can't be there to babysit it all the time, and when things go wrong, they get out-of-hand really quick. If injury or death occured, you'd essentially lose everything to an 8x8 grey box with bars on the windows.

Really, the best energy-use concept, is to run a self-exciting gen-head (say, one that was liberated from a blown-up genset), and feeding resistive heating and simple lighting loads, and saving the other costs. In doing so, the system is largely irrelevant to the frequency and voltage output... you're just turning the electricity into heat, so no serious 'regulation' is necessary... just mechanical energy transferred to electric, then to thermal. Stone simple, no safety hazards, and it puts every ounce you can capture... into good use.

To give you a rough idea of what you'll get... put up a 10kw homemade windmill, and if you can make the blades put in enough power to the genhead, that every 10kw will take over for about a 50kbtu furnace. If you're burning gas, but the electric one is running full-zoot, the savings will be simply that the gas furnace sits idle during high-wind times.
 








 
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