## Vertical Wind Turbine

Description

This win turbine is a simple one. Just four vanes on a turntable. The vanes are set at an angle of 45 degrees to the diameter at that point. The vanes form an aerofoil that pulls the turntable round by creating a partial vacuum on the "top" surface of the vane like the wing of an aircraft.

Like a glider the aspect ratio (height to width) 10:1 and the aerofoil flat with rounded leading and trailing edges..

The power it generates depends on the velocity of the air and the volume and density of air the turbine sweeps per second. The effect of the turbine is too cool the air but not change the velocity.

Power calculation:

The density of air is about 1.2 kg/m3 so if the turbine is 20 meters high and 20 meters in diameter (area 400 meters2 and if the velocity is 1 meter/second the volume swept per second is 400 m3 the mass is therefore 1.2 x 400 or 480 Kg. at 1 m sec the kinetic energy is (1/2)mv^2  or 240 Joule so the maximum power will be 240 watt.

At 10 meters per second wind speed the kinetic energy will be 240x100 watt or 24000 = 2.4 KW.

The power goes up as the square of the linear dimension so if the size is 50 meters x 50 meters the area will be 2500 and with a wind speed of 10 meters per second the power will be 250KW.

The material would be shiny like burnished brass or brushed aluminium so they glitter in the sun or green anodised aluminium for normal use. They could also be made from timber.

The generator needs to be a fairly simple direct drive generator or alternator with lithium storage and regulators to give continuous power. An inverter could be used to generate 250 volts AC.

Location

The design relies on minimum disturbance to air flow so should be on the ground. The rotation speed will be the same as the wind speed.

Environment

The wind downstream will be cooled by the sweeping and since 400 m^3 of air looses 240 Joule the temperature drop will be 400 m^3 x 1.2 kg/m3 x 100.35 J /Kg / K x delta T=240 Joule

So the drop in temperature will be 240/(400x1.2x100.35)=0.00049 K. This is caused by the drop of entropy as it passes through the turbine vanes.

Wind Farms

For high powers several rows of turbines would not disturb the flow of air, they would just cool it down.  a 1 degree drop of temperature will generate 400 x 1.2 x 100.35 Joules = 48168 Joules this is for 1 m/sec wind speed so the power would be 48.168 KW for 2040 windmills in a column a farm of 2040x2040 would generate 98.262 MW. This would occupy a space of 25x2040x2040 meters 104.04 Km^2 that is with a 5 meter separation between each mill for servicing.  They could be made taller, doubling the height would double the power. Since the power increases with the square of the wind speed the 10 meter/sec gives 100 times the power. So for this wind farm the power would be 9826.2 MW or for 40 meter tall turbines this comes to 19.652.4 GW.

Note

The design has been around prior to the 20th century and dates back 8000 years as it is mentioned in ancient texts including the “Cuneiform Bible” where they were used along side the hanging gardens of Babylon creating a land “flowing with milk and honey”. The water turbines lifted water in Archimedes spirals up to the high terraces and provided swimming in lotus water beds in a series of levels. The previous bucket brigade was operated by slaves but they kept falling of their ladders and died so King Nekabnezer used machines. The windmills provided power to lift water and replace treadmills. It was a source of wonder and the Jews wanted it so they invaded, but because the machines had no spirit so they broke them and they lost the milk and honey.

Here is an image of the vertical axis windmill in use and turning:

http://www.youtube.com/watch?v=OaVDvRaGcuE