# Low wind speed energy harvesting using supercapacitor (URGENT)

You need to do the calculations to figure out the amount of energy that will be produced by the wind turbine over, say, 7 days.

It is also essential to know the extreme maximum power that could be generated (presuming the minimum is 0). It would be a complete waste of time designing for low power and then have the system blow up the first time there is a strong gust of wind.

Without this fundamental information none of the rest of the issues can be dealt with properly - including such things as battery size.

If you have an AC output at a too-low voltage why not just use a transformer to increase the voltage?

...R

Can you provide the actual turbine specs. Most importantly, power output vs wind speed, and minimum cut in speed, ie what wind speed is needed to start the turbine spinning. If the Turbine is rated at 1.5 KW, I cant see any role for a supercapacitor, unless its the worlds largest.

Mauried, can you justify your last statement. Why do u say "If the Turbine is rated at 1.5 KW, I cant see any role for a supercapacitor, unless its the worlds largest."?

Thanks

jaysee_:
Why do u say “If the Turbine is rated at 1.5 KW, I cant see any role for a supercapacitor, unless its the worlds largest.”?

How many kWseconds can your supercapacitor hold?

This is beginning to look like a good ol’ XY Problem

…R

If the wind speed is always to low to produce enough current with one turbine, the answer is Z.. More turbines to produce more current. Or better yet obtain a turbine that will produce the needed current at low wind speeds. Is your turbine above the tree line?

Robin2: Without that information it is impossible to make any sensible recommendations.

this is all pre-build engineering. he said he wants to build a wind turbine. he has all the answers he needs already. charge the cap, once the voltage is reached, dump the charge into the battery. repeat once he gets things up and running, after the build, after he has the circuits in place, after he has charged the batteries, only then will he have any of the basic information. but then he will also have the answers. look at the joule thief. simple inductor, high voltage pulse, he could run that all day long into his charger for his batteries. this is not rocket science. there is no need for an Arduino as the basic charger is driven by voltage. one thing I have learned about engineers, they will figure-figure-figure-figure.... and never build anything unless you take the pencil away from them and give them a hammer. no doubt that they would re-size the silk screen to show the exact resistor size and then show the colors and take 2 paragraphs to detail which direction the resistor is placed to get maximum efficiency. and, yes, spend a week researching to figure out which direction the resistor should be wired to get maximum efficiency. this thread should be put out to pasture.

jaysee_: Sorry guys, I had a very busy week and didn't manage to reply.. Thanks for the feedback anyway.

Currently, I am facing a problem in the low current. As all of you aware, the wind speed in Malaysia is approximately 10-12 m/s.. In order to charge up the capacitor, I need at least 20m/s of wind speed. Hence,

Fyi, I charged the battery for 10++ hours and it drains out within half minute on just a very small load. (small fan)

Regards, Jay See

you need more wind not a capacator

I can see where @dave-in-nj is coming from.

But the impression I have gained is that the OP does not understand basic energy physics and is trying to apply a complex and expensive solution in a situation where it may make more sense to not use wind power.

I know someone who bought a 1kW wind turbine (I think from B&Q). I'm sure he had a lot of fun installing but he probably would have got just as much electricity out of it if the generator was connected so it was turned by the head rotating around the shaft.

...R

Hi, I agree with Robin2,

If the OP location windspeed is going to be less than 20 m/s, and usually around 12m/s, then he needs to calculate how much energy is [u]available[/u] at that 10 to 12 m/s.

Then design, locate a turbine that will work at that speed. The amount of power the OP will get depends on the wind speed, not what he wants.

I don't have the calcs, but there are calculator sites on the net that will tell you how much energy is in the wind for various speeds.

Wind turbines are like PV cells, they are not really high efficiency, it just that the energy is free/low cost. There is only so much energy you can pull with wind technology.

Tom.... :)

This thread is very confusing. Initially the OP talks about low wind harvesting then later indicates average wind speeds of 10 ms /sec.

10 ms /sec isnt low wind . Indeed many conventional small wind turbines will be producing close to full output power at that speed, hence why I asked the OP for the Turbine specs. Heres an example of a random 12V 1500 watt Turbine . (nothing magic about it.) http://www.northerntool.com/images/downloads/manuals/40091.pdf

Sect 2 gives the Power output vs Wind speed. At 10 ms/ sec output power is 600 watts and at 14 ms/sec its 1500 watts. A 12 V 1500 watt Turbine will be generating around 125 amps at full output power, so where a supercapacitor goes I have no idea. Most small Wind Turbines generate their maximum rated output at around 10 - 15 ms / sec wind speed, unless they are deliberately designed to be very inefficient , which is possible with small drag type VAWTs which have a very low Betz coefficient.

jaysee_: In order to charge up the capacitor, I need at least 20m/s of wind speed. Hence, I am thinking of building a differential amplifier that can sense the low current.

Why do you need at least 20m/s? As far as I know either the shaft doesn't turn (and there's no way you will get power from it, if that's the case) or it turns at a speed that is not high enough for the alternator to produce a voltage higher than the battery and hence get the electrons flowing. My previous post should detail how to turn this into useful energy. Alternatively, if the wind speed is always low, replace the 3ph rectifier with a diode voltage doubler such as this one:

There's also some widely known issues regarding wind power. Sometimes the problem is not wind speed, but wind turbulence. You should make sure this is not the case.

Hi Guys,

This is the VAWT I'm currently using. But mine output power is only 200W, output voltage 12 (but I'm getting only 3-5V with 30-50mA).

Is this wind turbine suitable for my application?

Thank you.

jaysee_: Is this wind turbine suitable for my application?

I don't recall that you have ever told us what is the range of wind speeds where your turbine is located. It is not just the min and max that matter, but also the time-weighted average energy. (Energy varies as the square of the wind speed).

...R

Robin2: I don't recall that you have ever told us what is the range of wind speeds where your turbine is located. It is not just the min and max that matter, but also the time-weighted average energy. (Energy varies as the square of the wind speed).

...R

Average Wind Speed: East Coast Peninsular Malaysia Jan = 4.5 m/s or 10 mph Feb = 3.5 m/s or 7.7 mph Mar = 3.0 m/s or 6.6 mph Apr = 2.6 m/s or 5.7 mph May = 2.3 m/s or 5.1 mph Jun = 2.0 m/s or 4.4 mph Jul = 2.3 m/s or 5.1 mph Aug =2.2 m/s or 4.8 mph Sep = 2.3 m/s or 5.1 mph Oct = 2.5 m/s or 5.5 mph Nov = 2.6 m/s or 5.7 mph Dec = 4.0 m/s or 8.8 mph

Typically, it takes 7 MPH just to start turning the wind turbine blades. In the USA, a Wind Turbine site should have, at least, one month with 12 mph or more. The full power rating of a Wind Turbines is at 25 mph. So, at 10 mph the Wind Turbine will generate only 6% of rated output.

Maybe, a "Max Power Point" (buck/boost) very high efficiency circuit would help here?

But we need to make sure the Wind Turbine is properly loaded at ALL times to prevent run-away and self destruction by a quick strong gust. And you know that it will eventually happen.

And what happens when a typhoon strength winds arrives ?

Hi Guys,

This is the VAWT I'm currently using. But mine output power is only 200W, output voltage 12 (but I'm getting only 3-5V with 30-50mA).

Is this wind turbine suitable for my application?

Thank you.

VAWT's are LESS efficient than HAWT's. 5 Volts x 50ma = 0.25 watts. Sounds about right. What is your average wind speed? How many watts were you expecting?

casemod: Why do you need at least 20m/s? As far as I know either the shaft doesn't turn (and there's no way you will get power from it, if that's the case) or it turns at a speed that is not high enough for the alternator to produce a voltage higher than the battery and hence get the electrons flowing. My previous post should detail how to turn this into useful energy. Alternatively, if the wind speed is always low, replace the 3ph rectifier with a diode voltage doubler such as this one:

There's also some widely known issues regarding wind power. Sometimes the problem is not wind speed, but wind turbulence. You should make sure this is not the case.

I too am confused with this 20 m/s wind speed. Most wind turbines are already at Full Power at 12 m/s or 25 mph.

How does this doubler circuit affect the "electrical loading" on the generator? Will the increased load on the generator cause the blades to stall? Will the increased load on the generator require an even higher minimum wind speed to start the blades turning?

mrsummitville:
Average Wind Speed: East Coast Peninsular Malaysia

If that is where the OP lives and if those are the correct wind speed values I would not waste money, time and effort on a wind tubine.

I don’t know where the numbers come from but I guess they are measurements at 10 metres above ground on a flat open site (i.e no nearby trees or buildings). If so, the OP’s turbine will probably experience considerably lower values.

…R

mrsummitville: Most wind turbines are already at Full Power at 12 m/s or 25 mph. turning?

Because thy were correctly sited in the first place ??

Robin2: If that is where the OP lives and if those are the correct wind speed values I would not waste money, time and effort on a wind tubine.

I don't know where the numbers come from but I guess they are measurements at 10 metres above ground on a flat open site (i.e no nearby trees or buildings). If so, the OP's turbine will probably experience considerably lower values.

...R

I looked at several cities in Malaysia. ALL of Malaysia has very Low Avg Wind Speed. They do get short periods (hours) of higher winds speeds during the typhoon season. Also, short periods (hours) of Land Breeze and Sea Breeze that could spin a wind turbine. That table came from a Wind Study by a University, done at the eastern shore line Anemometer was 60 feet above the ground and 76 feet above the ocean.

A Wind Turbine with a 10' Diameter Rotor mounted at 60 feet above the ground could recharge a 12 Volt battery with 7 Amps for about 8 Hours per day. For me, this is a about \$1.00 worth of electricity per month. A 1.5 KW Wind Turbine + 60' Tower installed is about \$10,000 So, payback is in 333 Years.

Hi all,

On the whole, Malaysia’s mean annual wind speed is 1.8 m/s. Does this amount of wind speed enough for this application?

Thank you.