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Hirvas

New member
Onkos noista Vevor 600W myllyistä kokemuksia?

Lisäys: Katselin youtube videoita tuosta, eikä saanut kyllä hyvä arvosteluja. Voisikohan tuolla kuitenkin boostata tulevaa aurinkojärjestelmää seuraavalla tavalla?

Talon harja etelä-pohjois suunnassa ja pääsääntöinen tuuli lounaasta. Olemme pienen mäen päällä ja peltoja ympärillä, joten kohtuu tuulinen paikka ajoittain. Talon lappeen jyrkkyys rintamamiestalon luokkaa. Tuulihan ahtautuu ja kiihtyy kohti harjaa, kun osuu katon lappeeseen. Lisäksi tuolla nousevalla, vaikkakin loivalla peltorinteellä on tuulta kiihdyttävä vaikutus. Jos tuollaisia laittaisi ihan harjalle, niin tämän "ahtopaineen" luulisi kiihdyttävän myllyyn osuvaa tuulta. Eli, en nostaisikaan sitä korkealle talon päälle, vaan ihan harjalle.

Mites on? Onko hukkaan heitettyä rahaa/fundeeraamista?

No, nyt löytyi virallinen ilmaisu tuolle virtauksen kiihtymiselle katolla, eli orografinen nosto. Tässä hyvää tietoa asiasta. https://www.nachi.org/wind-damage-part3-42.htm

Jutussa mainitaan, että tuuli voi kiihtyä jopa 2.5 kertaiseksi talon katolla tuon ilmiön takia. Tätä ajattelin tuolla myllyn asentamisella ihan harjalle.
 
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upnorthandpersonal

upnorthandpersonal

New member
Don't go with small wind turbines unless you have absolutely perfect conditions. It will be a disappointment otherwise. You're dealing with two fundamental issues:

- The Betz Limit
- The Power in Wind equation

The Betz Limit is basically a theoretical number of the maximum efficiency you can possibly get. At most, only 59.3% of the kinetic wind energy can be used to spin the turbine and generate electricity. Remember this is a theoretical limit; in practice, you're going to be closer to 40%.

The Power in Wind equation is given as:

P = 1/2 x ρ x A x V³

Where:
P = power in Watts
ρ = air density (kg/m³, at about 1.2 at sea level)
A = Swept area of the blades (m²)
V = Velocity of the wind

So, no matter how good your turbine is, you will get in practice at most 40% of the wind energy converted to electricity. To capture the wind energy in the first place, you have two variables to increase (one in your control, the other not): swept area and wind velocity. The smaller you make the turbine, the faster you need to spin to make any meaningful energy. The only variable you control is the swept area, which means making the blades as big as possible. Also notice that the velocity is cubed in that equation, so you'll generate much, much less power at low wind speeds.

In other words, small wind turbines don't work because physics.
 
topspeed

topspeed

Member
upnorthandpersonal sanoi:
Don't go with small wind turbines unless you have absolutely perfect conditions. It will be a disappointment otherwise. You're dealing with two fundamental issues:

- The Betz Limit
- The Power in Wind equation

The Betz Limit is basically a theoretical number of the maximum efficiency you can possibly get. At most, only 59.3% of the kinetic wind energy can be used to spin the turbine and generate electricity. Remember this is a theoretical limit; in practice, you're going to be closer to 40%.

The Power in Wind equation is given as:

P = 1/2 x ρ x A x V³

Where:
P = power in Watts
ρ = air density (kg/m³, at about 1.2 at sea level)
A = Swept area of the blades (m²)
V = Velocity of the wind

So, no matter how good your turbine is, you will get in practice at most 40% of the wind energy converted to electricity. To capture the wind energy in the first place, you have two variables to increase (one in your control, the other not): swept area and wind velocity. The smaller you make the turbine, the faster you need to spin to make any meaningful energy. The only variable you control is the swept area, which means making the blades as big as possible. Also notice that the velocity is cubed in that equation, so you'll generate much, much less power at low wind speeds.

In other words, small wind turbines don't work because physics.
Klikkaa laajentaaksesi...

Ongelma pienissä on ns Reynoldsin luku...isompi on aina tehokkaampi...yleensä.
 
topspeed

topspeed

Member
upnorthandpersonal sanoi:
Don't go with small wind turbines unless you have absolutely perfect conditions. It will be a disappointment otherwise. You're dealing with two fundamental issues:

- The Betz Limit
- The Power in Wind equation

The Betz Limit is basically a theoretical number of the maximum efficiency you can possibly get. At most, only 59.3% of the kinetic wind energy can be used to spin the turbine and generate electricity. Remember this is a theoretical limit; in practice, you're going to be closer to 40%.

The Power in Wind equation is given as:

P = 1/2 x ρ x A x V³

Where:
P = power in Watts
ρ = air density (kg/m³, at about 1.2 at sea level)
A = Swept area of the blades (m²)
V = Velocity of the wind

So, no matter how good your turbine is, you will get in practice at most 40% of the wind energy converted to electricity. To capture the wind energy in the first place, you have two variables to increase (one in your control, the other not): swept area and wind velocity. The smaller you make the turbine, the faster you need to spin to make any meaningful energy. The only variable you control is the swept area, which means making the blades as big as possible. Also notice that the velocity is cubed in that equation, so you'll generate much, much less power at low wind speeds.

In other words, small wind turbines don't work because physics.
Klikkaa laajentaaksesi...


Kyllä pienet toimii aivan hyvin...ne vaan eivät ole useinkaan kannattavia koska kwh hinta on korkea hyvin toimivalla laitteella. Hyvin toimivia laitteita on vähän ja ne maksaa kosolti...Hipar lopetti juuri koska pomo kuoli.
 
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