# Simeti Wind Turbine

#### txt29

##### Senior Member.
A client of mine asked me for a consultation about an investment into wind energy, where a seemingly very attractive technology was presented to him. It is a 5kW, small, compact, safe and efficient wind turbine by a Czech company Simeti Wind Energy. They claim many advantages: low weight of the equipment, return of investment in 4 years, long service life min. 20 years, minimum requirements for operation and maintenance, no noise and non-vibratory technology, etc. (specification page / PDF).

Immediately after seeing the presentation leaflet, comparing their small turbine with 3 vertical blades of 2.4m² of inefficient design, to the classical wind turbine with the diameter of 8m and giving the output of 5kW at the wind of 12m/s, I've advised the client to keep away. However, his supplier of PV panels (honest business) insisted that the company is well referenced, founded by well-known and smart scientists, working on military projects, and having numerous installations, among others in Scotland, Antarctide, etc. I did not want to argue without hard numbers, hence I went home and tried to put them together.

First of all the design of the turbine, some photos and a presentation video:

The power of wind can be calculated by the following formula (https://en.wikipedia.org/wiki/Wind_power#Wind_energy)

P = ½ ρ A v³

Ρ = density of air. At sea level and at 15 °C air has a density of approximately 1.225 kg/m3 (https://en.wikipedia.org/wiki/Density_of_air)

A = swept area 5m² (the swept area of the Simeti turbine is in the best case very close to the double of the blade size of 2.4m² - see image simeti02.jpg and simeti06.jpg)

V = wind velocity 12m/s (see image simeti01.jpg)

P = ½*1.225*5*12³ = 5292 W

The maximum power a wind turbine can extract from the wind is given by Betz's law (https://en.wikipedia.org/wiki/Betz's_law) - it is 59.3%.

5292 W * 0.593 = 3138 W

So ~3kW is the theoretical maximum any wind turbine of these dimensions could reach at this wind velocity. Simeti claims the power output 160% of this theoretical maximum. Practically, the power can be only a fraction of this theoretical maximum, though. Even the best and the most efficient wind turbines achieve up to 80% of the Betz limit at peak in ideal conditions.

The turbine of Simeti is a vertical axis wind turbine. By design it is a Savonious wind turbine with flat blades (https://en.wikipedia.org/wiki/Savonius_wind_turbine). Their advantage is the simplicity and reliability, not the efficiency. The range of the power coefficient values for the conventional Savonius rotors is between 10% and 25%. (Review of savonius wind turbine design and performance by M.Zemamou, M.Aggour, A.Toumi).

In numbers, it means the Simeti turbine, instead of the claimed 5kW, could give maximally the power of some 300 - 800 W (at the efficiency of 10% to 25%).

I am sending the link to this thread to the Simeti Company too, so that they can advocate their stand, or correct me if I misinterpreted some facts, or gave wrong information.

Also, after digging the web, there is a much more detailed Russian web site of Simeti at http://ett-simeti.ru/

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Let's have a look also at the other parameters given by Simeti on their website, and on their leaflets. Among others, they claim the return of investment in 4 to maximally 10 years [homepage, Q&A]. They claim the same return of investment also on the page designed for their Czech customers.

I do not know the exact current price of the turbine, but it looks like it was sold for 375,000 CZK (approx. \$19,000) [source]. Electricity from windpower sells for ~2 CZK (~\$0.10) per kW in Czech Republic. At a constant full power output of 5kW, it would indeed raughly cover the cost in about four years. The problem is that the average wind velocity in Czech Republic, on mountains and 10 meters above the ground, is barely 4m/s, which is three times less than the nominal wind of 12m/s. The energy of wind drops with the cube (third power) of velocity. Three times slower wind, means 27 times less power.

Even if the turbine was really capable of the output of 5kW at 12m/s (which is far above the theoretical maximum), it would only give the average output of 185W in the conditions of Czech mountains (much less in low altitudes). You would need to run it for 117 years to cover the cost. And it would have to harvest the wind energy also at low velocity wind, which is not the case (the specification tells the starting wind velocity is 1.6m/s).

Now, the Betz's limit for a turbine of these dimensions is just around 3kW. That translates into the return of investment in ~200 years (at 4m/s). As shown in the previous post, the true power output would be rather ~300-800W at 12m/s. At 4m/s it would be ~11-30W. That woud give the return of investment in ~3300, resp. in ~1200 years.

I found out that the Simeti wind turbine is also part of the Alfons Mobile Power Station (http://www.alfons-container.com/). It is made or marketed by another Czech company. I did not find yet whether Mr. Milata is also on the panel of the company, or whether they just buy the turbines from him. In 2015, they marketed the container for military and/or for rescue/disaster operations for example in Turkey, during the ISDEF trade fair in Israel , or during the AMEC NATO Days in Czech Republic

I did not check the other parameters of the container (PV panels, diesel generator, battery system,...), but on the first look I do not see anything as blatantly suspicious as the Simeti wind turbine.

What is strange, is that althought the wind turbine still figures on all their videos and on the photos, and a second wind turbine is still offered as an option, the main wind turbine disappeared from the specification already in 2016:

A video still presenting the container including the Simeti wind turbine:

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