Wind turbines with many small generators

russ_watters
Mentor
Actually, what we are looking for is the rating point (yes, it is at an unusually high speed), since the article gives the power output for, but as far as I can tell, not the associated wind speed. It does say, however:
...each Wind Tree can produce an average of 3.1 kW of power, 280 days of the year, enough to power 15 streetlights.

Although traditional wind turbines can generate 5-6 kW, their large size means they require strong winds to get moving, meaning they generate power for fewer days a year. Also, their huge size - towering up to 120 feet (36 meters) tall with the blade rotary diameter of up to 43 feet - means many find them an unattractive option. In comparison the Wind Trees are a rather petite 36 feet (11 meters) high and 26 feet (8 meters) wide.
Without the wind speed for the rating point (unless someone can find it...?), it is hard to know for sure, but here is a turbine rated for 5 kW at 22 mph wind speed, with a diameter of 20 ft.

http://www.saferwholesale.com/Aero-...IlrY2ChPC11z70VFogXM20cfwmH6GOOrM3BoCparw_wcB
Also:
Each Tree costs $36,500 (€29,500) The turbine I linked costs$10,000. So you can buy three of them for the cost of one Wind Tree. We can't know for sure how they compare without the rating point for the Wind Tree, but for less than a third the price for the Wind Tree's 5-6 kW you can get one conventional turbine to generate 5 kW while sweeping-out less area. Or buy three for the same price as a Wind Tree.

When designing a wind turbine all things are possible. Costs are a grey area and many companies ride the gravy train and art has no realistic attachment to value. I would think to much money is spent to save to little electricity. Example why not put a bigger leaf on top of the light pole. Instead of supplying power for 15 streetlights you have power for 72 or a branch with 4 or 5 for that matter. There are many better options to chose from than the tree imo.
Imo the tree was a government funded project so money and cost were not the objective.
Actually, what we are looking for is the rating point (yes, it is at an unusually high speed), since the article gives the power output for, but as far as I can tell, not the associated wind speed.
The rating point is relative, if you modify blade length, size or configuration the rating point is adjusted. The blade size and angle determines your cut in speeds. Its like a engine a 1000cc vs 1500cc vs a 2000cc motor.
Take the unit that you like for example,
-change the angle of attack of the blade and the rating point will change
-make the blade longer will change the rating point
A turbine will turn at 1 m/s but the generator will produce a 5v @ 100 W ( the numbers are for example purposes only) when it turns at 5 m/s it generates 110v @ 3kW and at 6 m/s it produces 115v @ 5kW, at 7 m/s 180v at which point the power generated is useless and is dumped and the wind turbine tilts.
Because of the aerodynamic effects of the blades, propeller racing can be avoided under all circumstances. (its a quote from the unit you are interested in) This is not possible with current engineering technology available. A mechanical system has to be employed, the turbine blade pitch must be adjusted to prevent propeller racing, thus making the blade smaller or the unit must be furled. There are techniques where a flexible blade is used. Or the generator is used to power an electrical brake system, a major stress to the system.
The turbine that they are selling you. It seems it is a fixed single wound motor. It does not have a gearbox. I would rather look for a dual or triple output wound motor that switches between windings at various speeds that crating a larger window of useful output. (Im sure they must be available, again it is one of my designs and might not be produced in the industry)
A triple wound motor ideally would the produce electricity over a wider range of wind conditions. At 3 m/s 110v @ 1kW , change windings at 5 m/s 110v @ 5 kW and change windings at 8 m/s @ 15kW. The generator side can get very complex with regard the windings and configuration and this will increase the performance 10 fold.
I have looked at a few website selling wind turbines none have impressed me so far, they are all selling a great idea incorrectly packaged. As this industry is extremely complex they are marketing an extremely average system (almost a backyard invention and very basic imo)
Lets break down what they are selling you, I will use top of my head figures here
a 5kW generator @ $1000 a propeller and hub @$ 500
a tail fin @ $200 a mounting @$ 100
slip ring @ $200 Charge controller @$ 500 if that is included in the $10k costs still to come mast and guy ropes @$ 2000
Inverter @ $1200 Batteries @$ 100 ea
and an electrician for a few hours
im sorry about the rant but I could go on for hours, as long as we have companies selling fancy words, wind power will get a bad name. It is not the wind thats the problem, its how we use it. And as long as silly trees get funded with tax money and the market is full of bad systems I will continue to pull my hair out.
omg can believe im posting this, lol

mfb
Mentor
Why is so little effort put into small power wind turbines.
If you have the wind (which clearly Zeynal has) irrespective of the blade size power can be produced. Small turbines with a low cut in speed are available and have proven to be efficient. Correctly placed and installed they have a higher efficiency than the big MW generators.
Many costs don't scale well to smaller turbines. A 5 MW generator does not cost 5000 times as much as a 1 kW generator, the power electronics doesn't scale with a factor of 5000, installing 5000 smaller turbines costs more than a single large one, and so on.

1 kW of continuous power generates annual revenues of ~40€/MWh * 1 kW * 1 year = 350 € (give or take a factor of 2 depending on market details), the 1 kW peak turbine will produce less. To get cost-neutral over 10 years (so you can finally start earning money at some point), the whole system including installation and maintenance has to be cheaper than 3500 €. Every inspection is a serious cost factor.
It gets a bit better for 5 kW, but for 5 MW costs just scale better.

billy_joule
With present systems on offer I tend to agree. Towers are frightfully expensive. That is why the units I am working on are low velocity roof mounted models. 5 x 1kW turbines excluding the towers makes the pricing very attractive. I think the price range will be about $350 - 500 each = max$ 2500 per 5 kW. The electrical installation and equipment, controllers, inverter and batteries will basically stay the same as the standard 5 kW system. As batteries are also a major cost, the time frame harvesting power is important as it can reduce the amount of batteries needed. It is also important to note that with every change in voltage results in a 20% loss of energy and this information is not published by the turbine suppliers, so in basis their 5kW will only provide 3.2kW of useful power. 220v > 24v >220v each phase based on a 80% efficiency on average. This loss is usually blamed on the wind. As its represented that a wind turbine is 40% efficient for example, the truth is the turbine is 60% efficient and current loss by converting the power is a staggering 40%. Another reason for losses is wind > electricity > heat, the 40% efficiency loss rears its head again. I don't think there are heating turbines on the market yet, but imagine how that will help your heating and electric bill.
1 kW of continuous power generates annual revenues of ~40€/MWh * 1 kW * 1 year = 350 € (give or take a factor of 2 depending on market details), the 1 kW peak turbine will produce less.
We need to look at how we consume our electricity. In effect we have all our eggs in one basket, all appliances are based on 220v even if they don't need it. A large percentage of electricity that we use wastes electricity, your downlighters are normally 12v, your computer is 12v, your Laptop is 19v, your TV 5 to 20 v, now add up all the 20% PF losses, that is power you are not using but you are paying for it. Wastage of transformed electricity could be as high as 15 or 20% of your monthly bill. As I said in an earlier post, we need to change our mentality and life style to effect the proper changes, imo its a pointless exercise to spend money on renewables while you are contributing to the problem, the source needs to change inline with the solution. ( If you understand what I mean.)
I suppose what im trying to say, we need to change the way we consume power for it to be effective. If your minus the 20% + 20% efficiency to your 10 years, the payback will be reduced to 6.4 years, that makes a nice difference to the bottom line.
Hope my calculations are correct, please check them, lol

mfb
Mentor
It is also important to note that with every change in voltage results in a 20% loss of energy
Only if the electronics is really, really bad. Even a laptop charger reaches 80% or more with multiple internal conversion steps.
As its represented that a wind turbine is 40% efficient for example, the truth is the turbine is 60% efficient and current loss by converting the power is a staggering 40%.
There is no 60% efficient wind turbine. And even if there would and if the generator would be 100% efficient (it is not), 40% loss would leave at most 36% total efficiency.
Another reason for losses is wind > electricity > heat, the 40% efficiency loss rears its head again.
Electric heating is basically 100% efficient. There is no energy lost to heat ;). A heat pump can reach an even higher efficiency.
Wastage of transformed electricity could be as high as 15 or 20% of your monthly bill.
What do you suggest as alternative? A separate wind turbine and a house-wide grid for every possible voltage some device might need?

256bits
Gold Member
So in theory it will produce 1kW minus Beltz law and only 0.59kW would be available. But lets not debate about windspeed

At 10m/s 600 w is the power of the moving wind.
Theoretical Betz limit is 59% of that, or 354 w.

For a real windmill, efficiency might be 80% of that or 283 w. extracted as useful power.

With increased wind speed, efficiency of the machine will drop, but since power within the wind increases as V3, and extracted power can also increase, but only if the generator, usage devices, or storage devices can use it. If not, then the rotor speed has to be scaled back, or the excess energy dumped.

With decreased wind speed, efficiency also drops and so does power within the wind. - a double whamy.

billy_joule
Only if the electronics is really, really bad. Even a laptop charger reaches 80% or more with multiple internal conversion steps.There is no 60% efficient wind turbine. And even if there would and if the generator would be 100% efficient (it is not), 40% loss would leave at most 36% total efficiency.
Electric heating is basically 100% efficient. There is no energy lost to heat ;). A heat pump can reach an even higher efficiency.
What do you suggest as alternative? A separate wind turbine and a house-wide grid for every possible voltage some device might need?
Short answer is Yes, a 12v and 220v (or something similar) should be standard imo, if we don't stop wasting we will continue overproducing to compensate and we pay for it.
With LEDs there is no reason why lighting should be 220v.
With specially wound generators 12 and 220v is possible (multi taps) generators can supply almost any voltage required.
Understand any power your inverter supplies is 40% less than generated (less but complicated 220>12 = 20% loss, 12> 220v = 20% loss = 37% loss in total and rounded to 40%)
Only if the electronics is really, really bad. Even a laptop charger reaches 80% or more with multiple internal conversion steps.There is no 60% efficient wind turbine. And even if there would and if the generator would be 100% efficient (it is not), 40% loss would leave at most 36% total efficiency.
Electric heating is basically 100% efficient. There is no energy lost to heat ;). A heat pump can reach an even higher efficiency.
What do you suggest as alternative? A separate wind turbine and a house-wide grid for every possible voltage some device might need?
When transforming electricity up or down there is a loss in efficiency, most PF is between 80 and 90%. So your 5kW unit produces 5kW 220v, goes to a transformer and reduced to 12v, only 4kW is received by the batteries, the loss over the transformer is 1kW, that is stored in the batteries, then the 12v is inverted to 220v again another 20% loss. This is all losses we can prevent.

256bits
Gold Member
I have always wondered why they don't have a row of propeller followed by a row of Savonius turbines.

Savonius turbines are only about 30% efficient, and if the wind has already had say, 50% of its power extracted ( an efficient propeller ) upwind, that leaves only 15% available that can be extracted with the 2nd row.

At 10m/s 600 w is the power of the moving wind.
Theoretical Betz limit is 59% of that, or 354 w.

For a real windmill, efficiency might be 80% of that or 283 w. extracted as useful power.

With increased wind speed, efficiency of the machine will drop, but since power within the wind increases as V3, and extracted power can also increase, but only if the generator, usage devices, or storage devices can use it. If not, then the rotor speed has to be scaled back, or the excess energy dumped.

With decreased wind speed, efficiency also drops and so does power within the wind. - a double whamy.
Agree, wind turbine are extremely complicated with current technology, it all looks so easy until you do it. And the salesmen make it sound to good to be true

mfb
Mentor
Short answer is Yes, a 12v and 220v (or something similar) should be standard imo, if we don't stop wasting we will continue overproducing to compensate and we pay for it.
With LEDs there is no reason why lighting should be 220v.
You cannot distribute 12 V over a city-sized power grid, losses in the cables will ruin that. It would be possible to have a central converter instead of many smaller ones, but I don't think that outweighs the additional effort of more cables everywhere.
Understand any power your inverter supplies is 40% less than generated (less but complicated 220>12 = 20% loss, 12> 220v = 20% loss = 37% loss in total and rounded to 40%)
It is not. Also, why should the generator output be transformed like that?

billy_joule
Im not good at the quotes thing so I hope you dont mind a straight answer.
q1
agreed, but lets keep national grid and home grid separate otherwise the convo gets very confusing
We are talking about wind generators for home use, so lets stay within the house.
q2
every transformation of electrical current suffer hysterisis and eddy current losses, magnetic and resistance losses, approximate efficiency is 80 to 90% so the resultant loss is 10 to 20%. each time electricity flows through a transformer. (its why Edison lost the lighting contract, lol)
Also, why should the generator output be transformed like that? same reason we don't only make 4" nails.
a multi wound generator operating 12/220v - 12v would provide lighting power at 0 losses (technicaly) it is rectified and feed into the batteries with 0 loss, the lights consume it with 0 loss, net effect is you have saved 0.6kW of power generated.
lets assume 1kW of power is used by the lights, 220v transformed to 12v inverted to 220v the 1kW is needed by the lights, the generator must supply 1.6kW @ 220v to have the 1kW output for the lights.
1.6 x 0.8 = 1.28kW to the batteries and 1.28 x 0.8 = 1.02kW supplied to the lights
from the equation you can see a bigger battery bank is needed to power the lights

mfb
Mentor
220v transformed to 12v inverted to 220v
Well, no one would do such a thing.

http://www.saferwholesale.com/Aero-...IlrY2ChPC11z70VFogXM20cfwmH6GOOrM3BoCparw_wcB
hats the unit Russ was looking at.
the specs provided
Specifications
• Power: 5KW
• Rated Rotated Speed: 200
• Rated Wind Speed (mph): 22
• Max Voltage: 7KW
• Output Voltage: 220v NOTE! TURBINE GENERATION
• Start Up Wind Speed (mph): 6.7
• Operating Wind Speed (mph): 6-55
• Security Wind Speed (mph): 110
• Height Of Tower (ft): 30
• Weight Of Top Section (lbs.): 630
• Output Controller System: Charger Inverter NOTE! CHANGING GENERATOR 220V TO 12V FOR THE BATTERIES
• Capacity & Quantity Of Battery (reference): 12V 200AH 18pcs NOTE! STORAGE OF THE GENERATOR POWER
the 12 /220v Invertor is not included with their system, its an optional extra.
By the way it is normal, all turbines (well most boats etc use a 12v generator) produce a higher voltage, needs thinner cables than 12v

mfb
Mentor
By the way it is normal, all turbines (well most boats etc use a 12v generator) produce a higher voltage, needs thinner cables than 12v
Corollary: Conversion losses are lower than losses in cables.
Also, you could put batteries in series to get 220 V (still needs AC/DC conversion of course) if it would help.

The picture im trying to paint is this,
Our electrical system is a Heath Robinson affair, they are antiquated and out dated for the new wave generation equipment we use. All current systems were designed and developed in the 1900s a long time before semi conductors and electronics. We have bound ourselves to the system and struggle to accept the inevitable. The same as the old die hards in there 1950s Cadillac that needed lead fuel. I am not saying the generation or the distribution systems in place are wrong. It is us the home owners that refuse to budge we are bound by institutions who have not kept up with technology, they keep adapting and adapting instead of rectifying the source.
Changing of electricity after your mains supply to any other voltage costs you money, my estimates are between 1 and 3kW of power is wasted per hour in the average house hold every evening, so lets say 4hrs x 1kW = 4kW (using the minimum) x 365.25 = 1461 kW per household per annum 0.4 euro (was the price mentioned I think) 584 euro wasted just in lighting costs wasted. To change just the lighting has a major impact on your bill.

Corollary: Conversion losses are lower than losses in cables.
Also, you could put batteries in series to get 220 V (still needs AC/DC conversion of course) if it would help.
Yes that is possible, haven't looked at 220/220 invertors tbh ( never thought of that )
I'm only designing the turbine and generator atm so haven't looked at storage or invertors as yet.