Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

petronila (Electrical) (OP)
25 Feb 13 13:51
Dear All

Some customer is speaking about reduce the power in one wind generator,the history is the wind generator is equiped with squirrel cage induction motor that works like generator. the think is this people only need generate 100 KW and the wind generator can generate 300 KW. Is not possible to do mechanical modifications.

I know could be possible install some resistance in order to "burn" power but really this issue is new for me the other idea is replace the motor by one of 100 kw but with exacly sizes (frame ) and same shaft diameter.

How to do it??

All inputs are wellcomme


Thanks and regards


Carlos
MiketheEngineer (Structural)
25 Feb 13 17:07
Feather the props somewhat??
Compositepro (Chemical)
25 Feb 13 19:16
It should also be pointed out that it is not the generator that determines the power output it is the wind speed and size of propeller. If you don't load the prop, brake it, or feather it, it will speed-up until it is destroyed.
msquared48 (Structural)
25 Feb 13 20:43
Can you backfeed the extra energy into the power grid?

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

Skogsgurra (Electrical)
26 Feb 13 2:21
Structural and chemical seem to be the motor/generator experts nowadays. Can't you read? Petronila says: "Is not possible to do mechanical modifications"

We are used to Mike's answers. And we do not like them. Has Mike lured otherwise competent members to dabble outside their expertise?

What if I started giving "advice" in chemistry or bridge-building?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

petronila (Electrical) (OP)
26 Feb 13 4:09
Hello msquared48

Is not possible to backfeed extra energy, thats the real problem, we need to waste that extra energy. For it I was speaking about the resistance connection in order to do some current divisor or something like that.

Quote: "It should also be pointed out that it is not the generator that determines the power output it is the wind speed and size of propeller", Thanks Compositepro but in this case the wind generator is designed to take the wind speed like a primotor, blades speed up and moves a gearbox, gearbox moves the generator and then you have electric energy, all overspeed could be detected by PLC protection and generator will be disconected, of course if you have a terrible wind you could have an overspeed, but usually the wind farms are calculated by previus study that take account the wind conditions.


Regards


Carlos
LionelHutz (Electrical)
26 Feb 13 8:32
I'm with Compositepro, the turbine needs to be loaded at all time. Your response about disconnecting the generator during an overload makes no sense. The turbine blades should never be able to overload the generator and you should never drop the load off the generator during high wind and high output conditions. You have to put brakes on or rotate the blades out of the wind if you want to stop generating.

Could you explain how the whole power system is being build so that you ended up with a cutoff level of exactly 100kW? I'm assuming this is some sort of islanded system?

I'd want to look at the turbine feeding storage and the storage powering inverters if the power required is 100kW. I don't know how you could successfully match wind turbine to power usage on a 1:1 ratio with a direct connected turbine.
petronila (Electrical) (OP)
26 Feb 13 10:14
Hi LionelHutz

This wind generator don´t belogs to one interconected system, not inverters, not step up transformers, is only a wind generator that will feed some load and is not synchronized with others wind generators. Think in small village very away from big power station, but located in a windy place, that people needs only 80 KW so 100 KW is OK, the problem is the available wind genearator is 300 KW, so what to do with 200 KW? they can´t share energy with no body and they are looking for a economic but technical solution. The blades are fixed and can´t be redirectioned to regulate power (no mechanical modifications are possible).


A possible solution could be Rewind the generator to 100 KW but controling the speed, this is essencial, output is related to the slip an a good control of load via speed could be the key that will avoid generator overloading.

Thanks for the inputs

Regards

Carlos
Strong (Mechanical)
26 Feb 13 10:56
How about electric resistance heating of a large water tank? The hot water can be used for cleaning and heating.

Walt
DRWeig (Electrical)
26 Feb 13 12:03
Man, this one has kept me awake. I've designed a few induction generator systems for waste energy recovery (gas pressure, steam, natural water flow). However, I have always had a heavy power grid available to back-feed.

First, a few curiosity questions: How is the induction generator excited? Is there an existing generator powering your small islanded "grid," or do you have another method? What sets the frequency other than the speed of your wind turbine? How is the voltage regulated?

I hate to think about wasting 200 kW on a regular basis. Figure out something useful. Strong's suggestion is good if you have a use for that much hot water. Irrigation pumps? A brightly-lit park? Lionel's suggestion about storage batteries? Pump uphill to make a new lake?

You can always get a resistive load bank, as you have suggested. No matter what you choose, the controls would be quite a challenge for me. The load bank will need to be 300 kW, so that it can dissipate the full power of the generator in the event that all the end users turn their switches off.

I wish I had more time to spend on this one. I'll be watching this thread.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

iop995 (Electrical)
26 Feb 13 13:26
300kW is maxim load accepted by generator and don't mean that if your load is 100kW, difference of 200kW must be diverted / sended to another loads. Power consumption is imposed by load value not by generator power capability. You need to regulate excitation of induction generator to keep frequency and voltage as stable posible.
LionelHutz (Electrical)
26 Feb 13 13:47
You are talking about a windmill with no mechanical speed controls. I don't see how you'll successfully run a wind turbine with an induction generator as the only power source and maintain anything close to a fixed voltage and frequency. I would not expect a wind turbine with an induction generator to work as more than say 15% of the "grid" capacity. In other words, I'd want to see >1.5MW of load on your "grid" all powered from stable generation sources before adding this wind turbine.

An induction generator wind turbine requires a stable grid to fix the voltage and frequency as well as maintain speed regulation on the turbine.

You do understand that with wind the power varies by the wind speed cubed. A small change in wind speed causes a large change in the available output power. How would you ensure the load is able to track the available power?

If the generator is always too powerful then you should be looking at modifying it. Either cut down the blades or change their pitch or simply replace them to lower the power produced.
petronila (Electrical) (OP)
26 Feb 13 17:49
Thanks to all for the inputs
I am not an expert in wind genertion matters, and I am not discussing about your inputs the informtion that you are receiving is the feedback from the customer and I see maybe the customer are not providing clear information. I am going to ask him more about the grid.

Maybe could be good if you cn share some information about this induction generators( Some papers)

Thanks again

Carlos
waross (Electrical)
27 Feb 13 1:38
There is too much mis-information and too little basic knowledge of generator theory here to try to sort out. There are a few things that may help such as adding a disk to block some of the blade area or better, turning the unit out of the wind based on the loading, but we have been stymied by the prohibition on mechanical changes.

Quote:

You need to regulate excitation of induction generator
Great idea. Do you have a diagram??
bye

Bill
--------------------
"Why not the best?"
Jimmy Carter

iop995 (Electrical)
27 Feb 13 5:41
To control excitation of IM need to use indirect methods as there are not direct acces to do that. IM may be self-excited by a capacitors bank or may use an external source. Some details may be found at http://www.nrel.gov/docs/fy00osti/26713.pdf or even more in google "self excited induction generator".
Using IM as generator and in not grid connected mode, need also a so called "load controller"; a practical example may be found here http://ludens.cl/Electron/picelc/picelc.html
waross (Electrical)
27 Feb 13 12:30
Yesterday was a long day.
I apologize for my short answer, petronila.

Basic generator types:
1. Load dependent;
This may be a standby generator, an islanded prime power generator or a swing generator. The controls monitor the frequency and control the power into the prime mover so that the power in equals the power out plus losses.

2. Fixed load;
Many large grid generators are run in fixed load mode. The load dispatch center will contact the generator operators and dictate the amount of power they desire from each site. Some plants will be designated swing generators and will adjust the power into the grid to compensate for small load changes. When large load changes are trending the fixed load generator operators will be instructed to change output accordingly.
Conventional generators are capable of operation in either load dependent or fixed load mode. However some prime movers and power sources are better suited to fixed load operation. The efficiency at low power levels is also a factor in the load control commands issued to a fixed load grid generator.

3; Fuel availability mode.
This mode is generally used to reclaim energy from waste or unused sources and the generator output depends on the availability of fuel for the prime mover.
This may be a "Run of the River" hydro plant, a turbo generator using the steam from a recovery boiler, land-fill gas recovery, or other uses of otherwise wasted energy.
These generators are typically connected to a larger system which is capable of absorbing all the power generated. Somewhere in the larger system there will be a swing generator which, in addition to compensating for load changes, will compensate for the changes in the input to the grid from the fuel available generator.

Controls:
Typically alternators are tightly frequency controlled by the governor or by connection to the grid and voltage controlled by an Automatic Voltage Regulator (AVR).

An induction generator has no controls. The frequency is controlled by the grid. The voltage is speed dependent. The excitation current is drawn from the grid. Capacitors may be used to supply the excitation current but they do not control the excitation, they divert the excitation current so that it is supplied by the capacitors rather than from the grid.

A wind turbine typically is connected to a system that will accept the total output. This may be a grid, large or small, or a battery bank or other means of storing energy. If you have a geographical feature that may be dammed to create a reservoir, pumped storage may be an option.

Wind energy is generally a fuel availability source. Running an induction generator islanded in fuel availability mode presents two non trivial issues.
A> Controlling power output.
B> Controlling voltage and frequency.

A, Power; you must either limit the power in by feathering the blades, spoiling, changing the angle of attack, braking or diverting the wind. Alternately you may generate full power and waste the excess.
Boiling water may be the best option. Boiling not heating! Based on a 200 kW load test years ago, I would suggest something in the order of 1000 gallons a day up in smoke or steam. Someone else do the math please.
You may not be able to generate in a light wind, and you will probably have to somehow stop the turbine in very strong winds.
Wind turbines are not suitable for prime power except for very small systems where a battery bank to store energy is feasible.

B, Controls; Well perusal of a couple of links shows that the ELC is intended for micro-hydro and not recommended for wind applications. It may be adaptable.
Does your Induction generator include a rectifier and inverter package? That is probably the only feasible way to control frequency and voltage from an induction generator driven by a wind turbine.
Rewinding the induction generator. Then it would take much less wind to overload and destroy the generator. If the wind energy captured by the blades exceeds the capability of the generator by very much the generator may be overloaded and destroyed, the turbine may overspeed and self destroy or both.
This project may not be possible with the available funds.

Bill
--------------------
"Why not the best?"
Jimmy Carter

ScottyUK (Electrical)
28 Feb 13 3:15
Hi Bill,

Many wind generators are dual-feed induction machines. There some good explanations turned up by Google. I think it is an interesting design of machine.

I think Carlos' problem may be difficult to resolve without either mechanical alterations to the machine to modify its capability to extract power from the wind, or provision to export into a larger system or dump the excess power generated into a load bank. If there is another method of dealing with this I'm interested to learn.
LionelHutz (Electrical)
28 Feb 13 8:30

Quote:

with squirrel cage induction motor

Yes, it's an interesting design but it's not present here.
ScottyUK (Electrical)
28 Feb 13 12:05
Yes, I'm aware of that. That's why the comment was addressed to Bill, not to Lionel...
LionelHutz (Electrical)
28 Feb 13 13:02
I'm not sure what your point was mentioning it at all in this thread. That design is no more suitable for the application in question than an induction generator is.
MikeHalloran (Mechanical)
28 Feb 13 15:06
No, I'm not _that_ Mike, but this may sound like one of his:

If you aren't allowed to change anything, the only remaining sensible course of action is to stay the hell away from the damn thing on windy days, let it blow itself up, and replace it with a properly designed machine with properly designed controls.



Mike Halloran
Pembroke Pines, FL, USA

waross (Electrical)
28 Feb 13 19:36
Can't we all be friends?? I appreciate the heads up from Scotty.
I am trying to compose a more tactful message than Mike's but I do agree.
If there is no chance to modify an unsuitable piece of equipment there may be no chance of success.
Wind turbines without some sort of energy storage are not a good choice for islanded applications.
I would like to help but even with modifications this application may fail as an islanded unit.

Bill
--------------------
"Why not the best?"
Jimmy Carter

Helpful Member!  LiteYear (Computer)
1 Mar 13 0:13
Nervously I offer another point of view, based on actual experience designing a new squirrel cage induction motor small wind turbine from generator to electrical load.

Quote:

other idea is replace the motor by one of 100 kw but with exacly sizes (frame ) and same shaft diameter

Wont work unless the blades are redesigned. The power comes from the blades, which if designed to extract 300kW will just overpower a 100kW motor.

Quote:

of course if you have a terrible wind you could have an overspeed, but usually the wind farms are calculated by previus study that take account the wind conditions
It's not true that the wind study prevents overspeed. Instead the wind study determines average wind speeds so the majority operation of the turbine can be optimised and yield can be estimated. The only constant with wind is that it changes. There will always be a higher wind event, and all turbines need a high wind shutdown function.

Quote:

If you aren't allowed to change anything, the only remaining sensible course of action is to stay the hell away from the damn thing on windy days

No one ever said you couldn't change anything, just that mechanical modifications aren't available. Working within those parameters, I suggest the following:

First determine whether it is a fixed speed or variable speed turbine. You suggest there's no inverter so it's more likely to be fixed (ie. must provide a fixed electrical frequency), but that's not a given.

If fixed, options are probably limited to bleeding off the additional power. Because there is only a small operating speed range, there is very little scope for limiting the power generated by the blades. Therefore, to maintain the same turbine availability (uptime) you must be prepared to consume 300kW. If you only have 100kW of guaranteed load, you need to dedicate 200kW more. Plenty of options as already suggested (heat water, pump uphill, etc.) but the best solution really depends on a heap of details we don't have.

Alternatively, if lower availability can be tolerated (relying on turbine shutdown function) less dedicated load can be used. Note however that the trade off is steep. Roughly speaking, even if you have 250kW load available for a 300kW turbine, expect it to be shutting down regularly on windy days. The wear on the shutdown device must of course be considered.

If the turbine is variable, there is another method available. By regulating the speed of the blades the turbine can be pulled off its maximum power point curve by lowering the tip speed ratio (TSR) early in the power curve. This has to be done very conservatively to ensure there is enough load to stall the blades, so there is a large hit on overall yield, but at least it allows operation in higher wind speeds.
Helpful Member!(2)  SparWeb (Aerospace)
1 Mar 13 1:58
Carlos,
The problem as you state it is a tricky one! I have built many wind turbines, but I've never had a problem like yours! The scope of the problem goes well beyond the electrical generator, though.
All of my projects have been off-grid, battery powered systems, so you can view my advice in that context.
I did, however spend years modifying and testing the turbines I built, in order to properly match up the rotor power taken from the wind with the power curve of the generator. It's been a difficult but interesting task, done a lot by experimentation.

I would like to know what type of wind turbine you have. I have to rule out Nordex, Lagerwey, Enercon or even a very small Vestas, which have pitch-controlled blades. Wind turbines are all very different inside, so the advice you are being given may be relevant or irrelevant, but we can't be sure. You mentioned a gearbox, so that also eliminates the Enercon. I'm surprised that the blades have fixed pitch, because most turbines greater than 40-ft (15m) diameter rely on blade pitch control to regulate their speed in some way, and yours must be much bigger than that to have a 300kW rating. We also haven't figured out yet what the central problem is... we can try guessing but it depends on the electrical grid on your island. Also wondering what the rated maximum power output of the turbine is supposed to be, rather than what peaks you are actually experiencing. Perhaps there is already a problem in the speed regulation system?

If I were to guess, the rotor is about 100 feet (30m) in diameter. Almost all turbines of that size have pitchable blades or blade-tips for speed control, despite what you say. Trying to re-tune a blade pitch control system is unlikely to have an adequate effect, and more likely to render the machine unsafe if done in the field by trial-and-error.

Something else to bear in mind: You report 300kW peak output power. That is electrical power output at maximum load, from the generator. Depending on the generator, it could be anywhere from 70% to 90% efficient, so actually, the input power to the generator shaft is closer to 400kW. Ignoring gearbox efficiency, then there is 400kW of mechanical power arriving at the shaft of the rotor blades. This is exactly in line with what I'd expect from a 100-foot diameter rotor in a 25 mph (13m/sec) wind. If you were to de-rate the generator to 100kW, but you don't do anything to the blades, then when the next storm comes, the rotor blades will deliver 400kW to their shaft, the gearbox will dutifully deliver 400kW to the generator shaft, and the generator will absorb about 150kW of it...

Leaving the rest of the power, 250kW, to be converted into heat and acceleration. Either the brakes will melt or the blades will fly off when they exceed 200 RPM.

You can't just chop the tips off of the blades, especially if they are fitted with tips that change pitch for over-speed control. If it is true that the blades are of fixed pitch, then maybe the notion of shortening each blade by 30 feet is plausible, but hard to take seriously.

So I advise against "de-rating" your wind turbine, without being prepared for major modifications and a considerable engineering effort. It is not a simple generator switch-out job. If you change one thing, the consequences upon other parts could be catastrophic if you don't change them, too. By the time you get the whole thing sorted out you could have purchased a 100kW wind turbine!!

Often, there are governments, social agencies, and investors who contribute to pay for the cost of a wind turbine installation. They expect a return on their investment. Cutting the output of the turbine by 67% will make the time for them to recover their investment triple. They will not be happy with you.

It might be cheaper, easier, and safer, to sell the 300kW turbine, and buy a 100kW unit if that's what you really need.


STF

petronila (Electrical) (OP)
1 Mar 13 12:40
Hello Spar Web,

Thanks for your inputs, is good have an aerospace point of view and more comming from one designer.

Trick, obcourse is a trick, we can´t control the blades, we know the best option is one 100 kW wind turbine but unfortunatelly the costumers buys somme of this wind turbines and due to country laws the wind geneartors can´t generate more than 100 kW and power output most be limited.

Our company is not specialized in wind turbine designs, we are electro-mechanical company, mainly electric motor repair shop, the costumer is interested in one solution for the problem and we think in one cheap solution, that one is burn the amount of power.


Thanks and a Purple Satr for the inputs.

Carlos
SparWeb (Aerospace)
1 Mar 13 14:12
There are a number of strategies for using up the excess power from a supply. Rather than wasting it as heat, though, you may find a way to do useful work with the excess power, rather than directing it to the grid. Pumping water comes to mind. If a nearby town uses electricity to pump water to a reservoir, maybe you could make a deal with them, to allow your excess energy to be used for that purpose.

What seems to escaped this entire discussion is that Carlos's customer has an excess of something valuable! A win-win arrangement can be found by following economic forces, rather than technological ones.

STF

racookpe1978 (Nuclear)
1 Mar 13 14:58
What you need to understand is that wind generators usually have a service factor (average actual delivered power/nameplate power rating) of 17-21%, with today's very large units able to 21% - 23% since they are taller and get better winds higher off the ground. So more than 80% of the time they cannot even generate their rated output -=> and for many, many hours of time when they DO generate some measurable power, it is not nameplate rated power but only 50 to 70% of that rated power.

Therefore, the fact that you "might, sometimes, for short periods of times" have to dump a a portion of your power to stay under the delivery limit of 100 KW is really a very small problem: Based on all wind turbines world wide, perhaps much less than 1/10 of the time is your wind turbine going to even approach nameplate power!

Therefore, you will need the ground-based electric dump resister bank, and will find it cheapest to build, requiring almost no maintenance cost, and you will find in use that it actually comes into play "wasting" power very very seldom. Because, even if it only happens 20% of the time, that extra power MUST be dumped before it hits the local grid. Now, what you could do as an (expensive!) option is feed a AC-DC converter from that resister bank and charge large DC batteries when the grid is overloaded. But you will face large and long-term battery and service unit maintenance and weekly charging procedures to avoid damaging - to the point of fire, flooding (of acid) and failure - the batteries.
waross (Electrical)
2 Mar 13 0:25
My wind turbine research, for a couple of projects that were abandoned when reality set in, and one expensive failure that I was not involved with but that I was aware of was about 10 or more years ago. At that time the accepted figure for average power developed as a percentage of nameplate rating was 15%. The newer, very large machines access more stable wind patterns but for a 400 kW induction motor turbine, I expect that the average power is closer to 15%. Other than that I agree with you racookpe1978

Bill
--------------------
"Why not the best?"
Jimmy Carter

LiteYear (Computer)
3 Mar 13 16:48

Quote (racookpe1978)

Therefore, the fact that you "might, sometimes, for short periods of times" have to dump a a portion of your power to stay under the delivery limit of 100 KW is really a very small problem: Based on all wind turbines world wide, perhaps much less than 1/10 of the time is your wind turbine going to even approach nameplate power!

This is a common misconception for those that haven't worked on wind turbines. If it really were a very small problem, manufacturers would lower the rating of the turbine, dump power for short periods, and have a much higher service factor. In fact, the low service factor is not by choice or dumb design - wind is just a hugely variable power source. There's a cubic relation of power to wind speed, which means you have to design the turbine for much higher power levels than its normal output.

The reason that large turbines have a higher service factor has less to do with their height and more to do with their inertia. The larger inertia smooths out the huge variations in input power so the peaks are not so much a problem. At the smaller end of the scale (most of my experience is with a very light 5kW turbine) you don't get the benefits of inertia and you hit peak power regularly, if fleetingly. At 100kW you'll be somewhere in between.

If a (fixed speed) turbine is rated at 300kW, you need to be able to load 300kW on the generator. Please put some faith in SparWeb's experience. All is not as it first seems with wind turbines!
racookpe1978 (Nuclear)
3 Mar 13 22:31
True, true. You need to be able to load that 300 KW on to the generator.

But the Original Poster's problem is that he cannot send that (potential) 300 KW to the local grid. it will get generated, but he cannot send it on and MUST get rid of it.

Therefore, he must dump the electric load to a assured, guaranteed reliable "dump" EVERY time it begins to exceed 100 KW.

my point was (is) that the feared loss of power is not going to happen very often because few windmills ever get to their rated capacity very often, when they get to near their rated capacity it is not for very long periods of time, and what power is generated at the rated capacity can be readily "lost" without a significant economic penalty. Like an oil refinery's flare - which has to be kept "uselessly" burning energy so it is immediately available to flame off dumps in the event of an accident - there are simple economic penalties that sometimes you just have to accept.

(Then again, one could (should) argue that windmills for ANY location that can be connected to the grid, are not economically competitive and they are being built now strictly for their national tax base rebates to the builder, erector, and fund politician's interest groups.
LionelHutz (Electrical)
4 Mar 13 8:26
Before worrying about loading the wind turbine the problem of this wind turbine with an induction generator seemingly being the only source or the main source on this "grid" needs to be addressed. There is no point planning on load dump equipment when the whole thing is going to fail.
Helpful Member!  waross (Electrical)
4 Mar 13 10:01
I'm with Lionel. I understand that this is an islanded application. A wind generator without storage is a bad choice. An islanded wind generator with an induction generator is a really bad choice. An islanded wind generator with an induction generator and no mechanical changes allowed ----- my vocabulary fails me.

Bill
--------------------
"Why not the best?"
Jimmy Carter

racookpe1978 (Nuclear)
4 Mar 13 11:46
I don't know enough about static inverters operating in a isolated environment to tell, so I will ask it openly hoping for criticism: If he had two (conventional) generators, load-sharing between the two becomes "balanced" depending on the frequency curves of the two and the amount of load, right? The "grid" in our regular world forces the frequency, but here - with only two generators - that assumption would not be true, correct?

So, if he is on an island, running a single static generator, the electronics of the static generator control the frequency (just like they do in my house when I am on my battery backup system during a blackout) because there is nothing else to hook up to. Could he reset a static inverter do do the following? His windmill is generating AC power now, so he buys a AC-to-DC two-way static converter, and hooks the DC side to a battery. In normal running, the windmill's AC generator and the battery's dc-to-AC inverter would share the load. His battery is charged when possible, but is usually kept near a float discharge.

In event of an overcharge (when he needs to dump power) the DC side continues to charge the battery, but at a higher rate than a trickle charge. In the event of a power failure, or loss of wind ! power during a calm or during over-speed of the wind, the DC battery drains down and the inverter carries the whole load.

It would be more expensive, but doesn't that give him a more reliable total system? Now, in very high winds, he loses all power - since the windmill can't be kept turning in excess winds. in high but less-than-rated capacity winds, he loses power to a resister. In no winds, he loses power because nothing can be generated from the windmill.
LiteYear (Computer)
4 Mar 13 21:21
Yeah that'd be fine. Typically called a hybrid system with AC backbone. But if the batteries are full and the loads are still only 100kW then you still have the problem of dumping the other 300kW.
OperaHouse (Electrical)
5 Mar 13 3:34
This is just another example of my theory that, "The customer is always wrong." When given any problem one should assume at least one third of the facts given are incorrect. If a customer could actually gather the correct information, they could solve their own problems.

Now we have a second issue, "Jumping to conclusions." A "consultant" trying to formulate a solution before gathering information. Nothing is really known at this point. Perhaps I missed the usual first step, "contact the manufacturer." We are lead to believe this mill has existed for a while and hasn't destroyed itself. And just how does the customer know they have excess power? Does it seem reasonable that someone makes a 300KW turbine that can't protect itself?. Is the customer off by three zeros? Did they get this off ebay with no instructions? I think someone is pulling your leg. All this bandwith would be better spent on an imaginary internet girlfriend.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close