Technical questions

lhsolar · May 2014

Hello all,

I had a few questions that someone may be able to clear up for me. I am setting up a home sized solar/wind system and want about a 1500w wind turbine.

First, in doing my research it seems that the whole world of wind is exceptionally deceptive. Correct me if I'm wrong. It seems that most of the less expensive (non MPPT) equipment out there just throws a high turbine voltage at the batteries then simply dumps the load when the batteries are full. Since a 12 volt battery will only take about 14.2 volts no matter what, are
they just losing all the voltage between peak and 14.2 volts?

Let me put it in math terms (hypothetical 1500 w turbine @ 100 V max):

Say this turbine is putting out the full 1500 watts @ 100 Volts = 15 Amps

But since the 12 Volt battery bank will only accept 14.2 Volts @ 15 amps we are actually only getting (14.2V * 15A)=213 Watts! And that's peak. Very bad.

I am having lots of trouble finding wind speed vs. voltage graphs for these turbines.

Am I correct in thinking that, with the controllers "they" sell and a 12V system, they are only really getting the 213 watts? Then they advertise the turbines at 1500w when one can only reasonably get 100 watts or so in moderate wind? By the way' I'm going to use an Midnight Solar MPPT.

Second, I am planning on putting a 48 volt battery bank in and am wondering if the turbine must spin up higher to produce 48 volts than it would to produce 12 volts, making it so the wind must be really blowing to even push 48V and killing my low wind performance, or does it produce 48 volts at low RPM?

What is a reasonable estimate of the voltage range of a "48 volt" turbine.

Thanks much!

stephendv · May 2014

Re: Technical questions

The turbine should be specifically built for a given battery voltage. Here's an example of a spec sheet for a 48V turbine: http://www.futurenergy.co.uk/pdf_doc/FE1048U%20(408).pdf

Using an MPPT controller helps a bit because the turbine gets to spin at its optimal speed, but as you can see from the graph, it's the current that increases much more than the voltage.

Cariboocoot · May 2014

Re: Technical questions

Welcome to the forum.

You're not too far off the mark, especially about "world of wind is exceptionally deceptive".

But turbines are Voltage-based power sources and the current comes from Voltage differential, so the output would be higher than the battery Voltage in order to make it charge. Too much higher and it will be a waste of power. That's where MPPT controllers are used to reduce high Voltage from a turbine (good for overcoming resistance in long wire runs) to something closer to proper battery charging Voltage while converting higher V to greater A. You would not put a 100 Volt turbine directly to a 12 Volt system for exactly this reason.

But if the turbine output is around the same Voltage as we would normally see for a solar panel (i.e. 20 Volts or so for a 12 Volt system) the direct connection with dump load controller will work.

How much Voltage a turbine puts out is not just a matter of RPM but also of how it is wound. Think 'electric motor operating backwards'. You can have an AC motor capable of running on either 120 or 240 but spinning at the same speed for either; it's just a matter of changing the wiring inside (parallel windings vs. series).

One of the worst problems with wind turbines are the exaggerated output claims. They leave out little details like 400 Watts in 30 MPH winds. They also might not mention that the thing will fly apart in those winds leaving bits hurled all over the place. When they don't want to give you those graphs that's a clue it's a product to avoid.

Three basic problems with wind power:
1). Site does not have enough wind to be practical. In reality you need sustained, steady, and fairly fast air speed to make any practical power output.
2). Cheap turbines with exaggerated output claims and poor quality.
3). Improper installation where the turbine is not in 'clear air' (too much turbulence so all the wind doesn't go into spinning the turbine).

For most people wind is a lost cause due to these factors. In dollar terms it's often better to spend the money on more solar, or a generator that works in any weather.

BB. · May 2014

Re: Technical questions

lhsolar wrote: »

First, in doing my research it seems that the whole world of wind is exceptionally deceptive.

In general, you are 100% correct.

Personally, I am not a fan small wind (off grid homes), and think that large wind farms create more problems than the solve... In that light, here are the good/bad/ugly links that we post to set the landscape:

Wind Power Links
www.otherpower.com (good forum for DIY Wind Power)
Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
Scoraig Wind "Recipe Book" for DYI Turbines (from Chris Olson... From his 4/11/2013 post)
www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)
Small windpower a scam ? Survey says SO
Truth About Skystream & SWWP
Windmax HY-2000 2kW Wind Turbine (apparently, some vendors don't sell spare parts--just new turbines. However, the owner, Edward has been very happy with its performance from 2010-2012--BB. 5/31/2012)

For the "dark side" of small wind, read these two links (from above):

So far, the only people, on average, that are happy with their systems:

put them on 60-90+ foot towers in good wind conditions (clear of trees, turbulent air, good prevailing winds >12 mph or so at "hub height").
did much of their own installation and servicing. Not many of us have a) the land for towers, and b) the equipment to R&R turbines on these towers with hiring equipment/technicians to do the servicing (additional costs)
don't live in lightning prone area (giant lightning rod bringing strikes into your power system)
have at least two or three independent methods to shut down turbines in high winds (electronic brakes, physical brakes, furling, feathering, etc.)
many have built/flown their own turbines and are capable of doing their own service
have a pretty much full size solar array to provide 9+ months of power and use the turbines for the "dark/windy months" of winter.

Correct me if I'm wrong. It seems that most of the less expensive (non MPPT) equipment out there just throws a high turbine voltage at the batteries then simply dumps the load when the batteries are full. Since a 12 volt battery will only take about 14.2 volts no matter what, are they just losing all the voltage between peak and 14.2 volts?

Yep--Roughly both the alternator's output voltage and current are proportional to RPM. Batteries are (ideally) fixed voltage devices.

If you look the I*V (and Power vs RPM) curve for the alternators ideally would attempt to match the Pmp=Imp*Vmp. That cannot be done when connected to a battery bank.

Let me put it in math terms (hypothetical 1500 w turbine @ 100 V max):

Say this turbine is putting out the full 1500 watts @ 100 Volts = 15 Amps

But since the 12 Volt battery bank will only accept 14.2 Volts @ 15 amps we are actually only getting (14.2V * 15A)=213 Watts! And that's peak. Very bad.

Exactly, a few MPPT solar charge manufactures (and some GT Inverter for Wind Turbine Mfg.) are designing their equipment to do "MPPT" (maximum power point tracking) for wind turbines--Just like they do for solar panels.

A favorite mfg. here that does that is Midnite's Solar with their Classic+Clipper (dump controller) system.

Early testing showed that you could harvest upwards of 3x the turbine's output with MPPT controller vs direct battery bank connection. That was a few years ago, I am sure they have better data now. While we can discuss the details for their equipment here, you will get some more attention on their forum:

http://midnitesolar.com/
http://www.midniteforum.com/index.php

You can use some of the other MPPT controllers on Wind/Water turbines even if they do not explicitly support RPM curve imports and such... However, you have to remember some of the issues:

HAWT (horizontal axis wind turbines) need 100% loading 100% of the time... If you "unload" a HAWT, they can (and will) over-speed and self destruct in high winds
Unloaded Alternators, in many cases, can exceed the input voltage ratings of a "generic" MPPT charge controller--If you have some electrical problem that unloads the MPPT controller, the turbine can over voltage the controller and over speed the turbine and "energetically disassemble".

I am having lots of trouble finding wind speed vs. voltage graphs for these turbines.

Because most of them output near zero useful Watts at less than 10 MPH winds, and maximum power at ~25 MPH--You do not find many places with 25 MPH continuous winds that you would like to live. And many turbines will shut down at >25-35 MPH--So you cannot collect any energy in a heavy wind storm (not that you want to be very close to most wind turbines in heavy winds).

And many, if you do the basic Betz limits calculations that their curves show over 100% (sometimes as much as 3x) the best case possibly wind harvest.

Also some of the available charts are given in kWH per month... And 600 kWH per month in 12 MPH wind sounds great--But you work backwards and see that assumes 12 MPT for 24 hours per day for 30 days per month. Very few wind installations will generate 10-20% of name plate rating in average wind conditions, and many small systems will generate 5% or less of name plate ratings.

Am I correct in thinking that, with the controllers "they" sell and a 12V system, they are only really getting the 213 watts? Then they advertise the turbines at 1500w when one can only reasonably get 100 watts or so in moderate wind? By the way' I'm going to use an Midnight Solar MPPT.

When you have numbers flying around that have no grounding in real life--Who knows what they are really selling. You may get 1.5 kW from a 24 volt turbine in 25 MPH winds--But that is something like 51 amps into a 29 volt battery in Absorb stage charging. It is do-able--But will you see it outside of winter storms--not usually.

Even one of the "best performing turbines" was the Skystream 3.7 meter diameter HAWT could (sometimes) output upwards of 400-600 kWH per month. This was a grid tied wind turbine (no direct to battery option).

However, many folks had problems getting them running and/or keeping them running (you can read the Skystream thread above for the details). Putting a wind turbine+GT Inverter electronics 60' in the air with vibration/wind/sun/rain/ice/lightning is just asking for problems. Add some other issues, and it was just a matter of time until they went out of business.

Second, I am planning on putting a 48 volt battery bank in and am wondering if the turbine must spin up higher to produce 48 volts than it would to produce 12 volts, making it so the wind must be really blowing to even push 48V and killing my low wind performance, or does it produce 48 volts at low RPM?

Some vendors (appear) to wind for specific voltage battery bank... Others will give you a 12/24 volt version and have two difference performance charts. TLG is one vendor that has had some nice things said about their "smaller" systems (do your own research--Links are just for discussion):

http://www.tlgwindpower.com/videos/tlg500_main.htm
12 Volt Battery Environment
24 Volt Battery Environment

See next post...

solarix · May 2014

Re: Technical questions

Not knowing where you are located, but given how much the cost of solar has come down and how the unreliability of wind chargers has gone up, I wonder about the viability of the wind charger business.

BB. · May 2014

Re: Technical questions

Wind Speed MPH +/- 2
Amps into Battery Bank +/- 1.0
Battery Voltage +/- 1
Average Watts

5 MPH
1 Amp
12 Volts
12 Watts

8 MPH
2.5 Amps
12 Volts
30 Watts

9 MPH
3 Amps
12 Volts
36 Watts

11 MPH
4 Amps
12.5 Volts
50 Watts

12 MPH
5 Amps
13 Volts
65 Watts

18 MPH
10 Amps
13.5 Volts
135 Watts

24 MPH
15 Amps
13.7 Volts
205 Watts

28 MPH
20 Amps
14 Volts
280 Watts

30 MPH
25 Amps
14.4 Volts
360 Watts

34 MPH
30 Amps
14.7 Volts
441 Watts

38 MPH
35 Amps
14.8 Volts
518 Watts

45 MPH
40 Amps
14.8 Volts
592 Watts

50 MPH
50 Amps
14.8 Volts
740 Watts

Wind Speed MPH +/- 2
Amps into Battery Bank +/- 0.5
Battery Voltage +/- 1
Average Watts

7 MPH
1 Amp
24.0 Volts
24 Watts

9 MPH
2 Amp
24.0 Volts
48 Watts

15 MPH
5 Amp
24.8 Volts
124 Watts

20 MPH
10 Amps
25.2 Volts
254 Watts

25 MPH
15 Amps
26.8 Volts
402 Watts

34 MPH
23 Amps
27.1 Volts
623 Watts

40 MPH
30 Amps
28.2 Volts
846 Watts

45 MPH
39 Amps
28.5 Volts
1111 Watts

50 MPH
50 Amps
29.8 Volts
1490 Watts

see next post....

BB. · May 2014

Re: Technical questions

What is a reasonable estimate of the voltage range of a "48 volt" turbine.

It is probably not that easy... Questions to ask are "what are your power needs" (voltage/current/watt*hours per day, etc.), what are your winds at hub height (note: fly a kite and find out how high you need your blades to get of of turbulance--Do not try to generate power in turbulant air--It is pretty much impractical), what are the avialable winds in your area (by month/season), etc.

Once you have some basic answers, you can start looking for Off The Shelf or DYI turbines. In general, the turbines are the "cheap part" of wind installations. The cost of the power, cables, electronics, and labor/equipment are the vast majority of the cost for wind.

If you have installations in your area, ask them questions. My "gold standard" is to ask for (at least) monthly kWH numbers for a leat a 1 year period.... See what you get back.

BB. wrote: »

There was one Skystream owner (blog.keepturning.com website long since abandoned) (near Lake Erie?) during the good months, as I remember:

JANES HOUSEHOLD SKYSTREAM kWh RECORD

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

Total

2007

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

175

225

0*

400

2008

98*

292

308
246
228
153
92
84
97
164
246
472
2,480

2009

265
348
244
371
182
86
90
84
250
100
194
131*
2,345

2010

101
130

* December, 2007 - Skystream shut down from software problem with cold and would not restart.
* January, 2008 - Skystream down until the 27th. Produce 98kWh in the 5 days remaining in the month.
* December, 2009 - Skystream shut down several times and would not restart on it's own, production very low for wind speeds.
* January, 2010 - Production very low for wind speeds.
* February, 2010 - Production very low for wind speeds.

-Bill

The above is one of the longest small wind output charts I have seen... Notice that the output is highly variable--much of it based on reliability/turbine issues (I think).

If somebody claims better (peak monthly) numbers than the above with a 3.7 meter turbine, I would have my doubts. And remember that power goes with the square of the turbine diameter... A 1/2 diameter turbine would generate 1/4 the amount of power (assuming all else is the same, which it rarely is).

-Bill

lhsolar · May 2014

Re: Technical questions

For whatever it's worth, we are near Salem Oregon.

mike95490 · May 2014

Re: Technical questions

lhsolar wrote: »

Hello all,

I had a few questions that someone may be able to clear up for me. I am setting up a home sized solar/wind system and want about a 1500w wind turbine.

First, in doing my research it seems that the whole world of wind is exceptionally deceptive. Correct me if I'm wrong. ....

sadly, you are not wrong. I want a wind turbine too, but I've given up on that idea. Just solar & backup generator.

BB. · May 2014

Re: Technical questions

According to this map, Salem Oregon is in between to mountain/hill ranges and has very little wind energy:

http://rredc.nrel.gov/wind/pubs/atlas/maps/chap3/3-05m.html

Oregon appears to have some tax credits:

http://www.oregon.gov/energy/cons/res/tax/docs/wind.pdf

The Oregon Residential Energy Tax Credit Program provides tax credits totaling up to a maximum of $6,000 if you buy a qualifying wind AED, not to exceed 50 percent of the net cost of the wind AED. If the credit exceeds $1,500, the credit will be paid over multiple years with a maximum of $1,500 per year. You claim the tax credits when you file your state income tax.
ODOE requirements for Residential Wind Systems
• These systems must have a minimum annual average wind speed of 10 mph at hub height demonstrated at the wind AED installation site.
• All wind Alternative Energy Devices (wind AEDs) must have a minimum tower height of 70 feet. (A taller tower may be required to obtain proper clearance over obstacles).
• All portions of the wind AED’s rotor disc must be at least 30 feet over any object within a 400 radius of its base. (Tree growth over the next 20 – 30 years should be considered when siting the wind AED).
• A wind AED must produce at least 100 kWh a month on average and 1200 kWh over the course of a year. (We understand that some months are windier than others so we allow production to accrue annually).
• The wind AED must meet industry standards as approved by the department.
If you meet these criteria, take the following steps to receive your tax credit:

Map of Oregon winds speeds 50 meters/165 feet:

http://www.edcoinfo.com/CEDocuments/Downloads_GetFile.aspx?id=359710&fd=0

Do not bother withe the www[dot]windpowermaps[dot]org in the above map... Dead linking going to some sort of random Japanese site parking lot(?).

-Bill

lhsolar · May 2014

Re: Technical questions

So, in trying to decipher the nonsense out there the situation seems to be this: you try to get a wind turbine that starts to put out (in my case) 48 volts when it starts to spin. Any power above that 48 volts you lose forever (just the same as solar panels with a PWM controller, only worse because the wide variation in voltage makes it impossible to match the battery voltage effectively). So right there you lose lots of your juice. How much would depend on the difference between battery voltage and turbine voltage when it's at max. If the difference is only a few volts then no big deal, if it is 50 volts then you loose a huge amount of your power.

The math:

Theoretical 1500 W turbine w/Voltage range of 48-58 Volts

Baseline with a perfect conversion to battery voltage:
1500W/48 Volts= 31.25 Amps

More reality:
1500W/58 Volts= 25.86 amps, pretty good

Bad news: turbine w/ voltage range of 48-108 V
1500W/108 Volts=13.88 A

17.37 Amps totally lost, that's 55.6%, unacceptable in my world considering an MPPT with a dump load should be able to recover that.

So are the manufacturers just not bright enough to realize that you need an MPPT or some sort of dc/dc converter to recover that excess voltage?

Anyone want to throw out a general voltage range for these 10V? 20V? 50V?

Again, am I understanding things correctly?

Cariboocoot · May 2014

Re: Technical questions

You've pretty much got it.

Some manufacturers don't actually give a flaming hippo. If they did there wouldn't be "12 VDC" turbines with "built-in regulator" that try to send a mere 13.8 Volts down 100 feet of 4 AWG wire expecting something to happen at the other end.

Unfortunately power systems have lots of losses in them even for good designs. You try to minimize them as best you can, but you have to draw the line somewhere as it becomes impractical to use huge 4/0 wire inside sealed casings full of liquid nitrogen. Stuff like that.

Incidentally, most 48 Volt systems will charge at around 60 Volts for Absorb, and on the PV side usually have an array of about 70 Vmp. This sort of Voltage range will work for turbines too.

Take a look at MidNite's Classic controller & Clipper. It is the best you can get for turbines these days: http://www.solar-electric.com/misoclchco.html

BB. · May 2014

Re: Technical questions

And for the Midnite product, you are looking at ~$1,600 for a MPPT charge controller plus dynamic load controller by itself.

It is not cheap to get ~3x more power from your wind turbine.

Just to give you an idea of what an Alternator Curve may look like:

http://www.scielo.br/img/revistas/jmoea/v10n1/10f08.jpg

Attachment not found.

In reality, the wind turbine is probably only about 50%-60% efficient at converting shaft torque * RPM into useful electricity. Add a gear box or belts to use a modified automotive alternator on a wind turbine, and you get around 50% mechanical... In power, there are lots of losses and they are usually "acceptable losses", because any more efficiency is either not cost effective, or even possible.

-Bill

lhsolar · May 2014

Re: Technical questions

I was thinking the Midnight Solar "Kid". It is a good price and should handle lots of watts at 48V. The Clipper on the other hand is a tough pill to swallow. $900 for a few resistors, running through a Solid State Relay controlled by some electronics with a few breakers and capacitors in a box is a tough sell considering there's only $125ish in components. That makes the dollars not pencil out in a hurry. Ebay has dump loads by the dozens for way cheaper, can these be used?

BB. · May 2014

Re: Technical questions

I am going to beg off on answering this... The issues are many and not something that (I think) that I can give cookbook answers on.

The links I gave above should have lots of information about the details for designing a system.

www.otherpower.com (good forum for DIY Wind Power)
Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
Scoraig Wind "Recipe Book" for DYI Turbines

-Bill

Cariboocoot · May 2014

Re: Technical questions

lhsolar wrote: »

I was thinking the Midnight Solar "Kid". It is a good price and should handle lots of watts at 48V. The Clipper on the other hand is a tough pill to swallow. $900 for a few resistors, running through a Solid State Relay controlled by some electronics with a few breakers and capacitors in a box is a tough sell considering there's only $125ish in components. That makes the dollars not pencil out in a hurry. Ebay has dump loads by the dozens for way cheaper, can these be used?

The Kid is capable of handling 30 Amps - about 1440 Watts on 48 Volts at minimum Voltage. A 1500 Watt turbine could be too much for it. There would be no margin for error.

The Clipper is a controlled dump load that can be used in conjunction with the Classic controller. If boB wants to argue the economic value with you I'll leave that to him. :roll:

If you don't want to spend the money (and wind power is a lot of 'spending money') You are down to using a PWM controller type being used as a shunt to a dump load. Such as the Morningstar TriStar 45 PWM say, and then you can use the dump load of your choice - and make use of the power for heating water for example.

Note that the NEC requires two redundant such regulating systems to be compliant.

Many of us have thought wind would be a good addition to our systems - right up to when we started running numbers and working out the details. Over-all not a good value for the energy dollar. Ironically it works better on a larger scale.

jcheil · May 2014

Re: Technical questions

Cariboocoot wrote: »

The Kid is capable of handling 30 Amps - about 1440 Watts on 48 Volts at minimum Voltage. A 1500 Watt turbine could be too much for it. There would be no margin for error.

The Clipper is a controlled dump load that can be used in conjunction with the Classic controller. If boB wants to argue the economic value with you I'll leave that to him. :roll:

If you don't want to spend the money (and wind power is a lot of 'spending money') You are down to using a PWM controller type being used as a shunt to a dump load. Such as the Morningstar TriStar 45 PWM say, and then you can use the dump load of your choice - and make use of the power for heating water for example.

Note that the NEC requires two redundant such regulating systems to be compliant.

Many of us have thought wind would be a good addition to our systems - right up to when we started running numbers and working out the details. Over-all not a good value for the energy dollar. Ironically it works better on a larger scale.

I am in the process of doing an "experiment" with wind here in central Florida where our average wind speed is only 10-12mph. BUT, the ONLY reason I am doing it is because I got an 80' tower for free and all the wire I need to run it 200 feet back to my power room and I have a C40 that I am not using and a bunch of extra breakers, etc. So the only thing I have to buy is a dump load and the turbine itself. And I am not going to go crazy on that, perhaps $350 total for a "claimed" 800watt (in 30mph winds) one. If it is as disappointing as I expect, at worst, I'll ebay the turbine, take a bit of a loss and end up with a kick-butt tower for my TV antenna and cell-repeater antenna

BB. · May 2014

Re: Technical questions

Get your HAM License and put an antenna on it?

Just download the test(s) (Tech, General, Extra):

http://www.arrl.org/question-pools

Just print out a copy, highlight the correct answers. Spend a week reading only the correct answers in your free time. Take the test, answering with the first one that comes to mind. Turn in test.

-Bill

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