Beginners

VARIETY OF WIND TURBINES

There are lots of machines, mechanisms and aggregates which “catch” the wind and convert it into the useful power.

HORIZONTAL AXIS WIND TURBINES (HAWT)
Wind Turbine with horizontal axis of rotation (propellers) are the most widely distributed turbines due to traditions shaped for years of wind power technology development. However all these machines have on serious disadvantage – they “think” before turning their blades (air foils) “on the wind” which direction is changing every second.

Diagram below shows that the swept area of propeller (area covered by blades - basic value for output power calculation), is essentially less than what is shown in manuals of HAWT. 

The calculated efficiency for HAWT is 45% (ideal is 59.3%). In reality propeller generates much less power than listed in manual (in practice the efficiency is 20-30%). Thus HAWT should be installed in the places where the direction of wind is known in advance.

VERTICAL AXIS WIND TURBINES (VAWT)
Wind Turbines with vertical axis of rotation do not have to be oriented on the wind. One of them have the advantage of self-starting on low wind speed (1-2 m/sec) but not widely distributed due to the low efficiency (15-18%):

Another types of VAWTs are not well known as designed not a long time ago. Their theoretical efficiency (59.3%) does not exceed the efficiency of HAWTs, however due to the use of wind incoming from any direction, the real efficiency can be as high as 38%. In some cases the efficiency can be even 42% (ideal horizontal wind flow), independently of quickly changing wind direction.

Today VAWTs can “catch” the gusts of the wind. This advantage in fact increases their efficiency. The more the efficiency, the less the cost of Wind Turbine as the quantity of materials for production is less.

Scientists continue arguing about the advantages and disadvantages of different types of Wind Turbines. The customer should only understand that there are lots of types, classes and modifications of mechanisms converting the motion of wind flow into electric energy as well as there are lots of automobiles of many types, classes and modifications.

One should also understand that different types of Wind Turbines are intended for different conditions. For instance when the wind direction is known, then horizontal axis turbine should be installed. And instead if the wind direction is changing all the time, then the vertical axis wind turbine will be more efficient.

The consumer must know that the Wind Turbine is not a simple household appliance, but it’s a complex aggregate which produces electric energy and needs periodical servicing as any automobile or mechanism.

HOW DOES THE WIND TURBINE OPERATE?
Due to the blowing wind the wind rotor, made of blades mounted between rings, rotates and rolls the rotor of alternator which generates 48VDC electric current with the help of electronic regulator.

Inverter converts 48VDC current to 220/110VAC with 50/60 Hz frequency and gives it out to consumer. Batteries are connected in parallel with the output of alternator and supply the inverter in case when there is no wind.

The output clamps of inverter should be connected with outdoor clamps of consumer household electric net or office interconnection wiring.

WPU self starts on 3.5 m/sec wind gust. At the same time anemometer can show much less speed of the wind. WPU starts generating electric power on 4 m/sec wind speed.

WIND POWER CALCULATION
The table below shows how the energy can be calculated. The simple example is shown for 3 kW (kilowatt) Wind Turbine (the size of swept area is 4 х 6 = 24 square meters) on nominal wind speed 10 m/sec.

The efficiency of wind rotor (real aerodynamic efficiency verified by testing) is 36%.
Make your own calculations changing the appropriate numbers:

Recommendations written in the site will help to make step by step calculations  of Wind Turbine size and number of batteries (see “For advanced”), to forget the monthly electricity bills and unexpected disconnections of grid. This is the main advantage of Wind Turbine when the grid is nearby. If there is no grid, then this calculation is the first step of getting the free electric power.