The Turby concept

The necessity for renewable energy

– Large wind turbines

-

public issues

– Photo

-

V

oltaïcs

-

not economical

– Small wind turbines

-

attractive, but need height

– Height essential

-

but expensive

Use available height

BUILDINGS

Urban Turbines

Design criteria

Safety

Good price / performance ratio

•

Good efficiency

•

Low cost of manufacturing

•

Low additional costs for transport and erection

•

Maintenance free

No impacts

•

vibrations

•

noise

•

flickering / shade

Fundamental choices

AXIS:

Horizontal (HAWT) or Vertical (VAWT) ?

•

VAWT mechanically simpler

•

aerodynamically more complex

ROTOR:

Impulse type or aerodynamic ?

Impulse type (Savonius)
-

extracts energy in the direction of the flow

-

Ș

theoretical

< 19 %

Aerodynamic (lift) type rotor
-

extracts energy perpendicular to the flow

-

Ș

theoretical

< 59 %

Turby is an aerodynamic VAWT

VAWT: Basic principle

• Angle of attack [

Į] :

– Blade speed (rotational speed x radius) & Wind speed

–

Į < 15

0

: ENERGY;

Į > 15

0

STALL

• To prevent stall:

Blade speed > 3-4 x wind speed

Blade speed

Wind

Angle of attack

App

are

nt w

ind

Rotating rotor "sees"
a rotating wind

The best known VAWT: Darrieus

• Rotational speed same over length of

axis

• Radius varies

• Blade speeds varies

• Near shaft: STALL

vibrations

• In middle

Į § 0

0

noise

• In between: lift

energy

• Little effective use of rotor surface

Turby’s solution

• Constant radius

• Uneven number of blades

• Blades twisted to smoothen

the effects change of wind
direction

Turby meets design goals

Safety

Survival wind speed > 55 m/s

Kevlar inlay - blades may crack but will not shatter

2 independent brake systems / vibration control

Price / performance

Good efficiency

Few systems

Easy transportation and installation

Maintenance free

Impacts

Nearly vibration free

Noise level 70 dB(A) at 5 m distance

Small blades matte finish

Yield

Available wind energy

•

Macro

average wind speed in the area

•

Micro

roughness of the terrain

•

height

•

increase in wind speed over obstacles

•

undisturbed wind flow from all directions

Properties of the windturbine

•

Efficiency

•

Suitability for local conditions

•

turbulence

•

temperatures

•

snow and icing

Yield II

• Effect of

average
wind
speed

• Effect of

height

Annual yield - average w indspeed

0

1

2

3

4

5

6

7

8

4

4,5

5

5,5

6

6,5

7

v wind average [m/s]

MWh

Annual yield - height

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0

10

20

30

40

50

60

70

80

height of tower

kW

h

Yield varies with area and height

Annual yield - height and roughness length for the Netherlands

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0

10

20

30

40

50

60

70

80

height of tower [m]

yi

e

ld

[

k

W

h

]

Each of these 100 lines
represents a 1% area of
the Netherlands

Wind speed range

0

500

1000

1500

2000

2500

3000

0

5

10

15

20

wind speed

h /

W

0

50

100

150

200

250

300

350

400

450

500

kW

h

wind speed distribution

power curve

energy production [kWh]

Effect of direction

0%

2%

4%

6%

8%

10%

12%

14%

0 t/m 4 m/s

5 t/m 12 m/s

> 12 m/s

totaal

A free flow from all sides is important

Wind over buildings

• above

the roof.

• near centre

of roof

• undisturbed flow

from all sides

• Wind speeds 1,2 – 1,4 x higher! > 2 x more energy

Local conditions

0

4

8

12

16

20

24

28

-15

-10

-5

0

5

10

15

20

25

30

35

Temperature [C]

W

in

d

sp

eed

[

m

/s]

De Bilt
Eelde
Vlissingen

Status

•

Turby concept

August 2000

•

Windtunnel tests 2001

•

Full scale prototype

March 2002

•

Testing – engineering

2002 / 2003

•

Final prototype

January2004

•

Prototype series 24 units

7 installed

2004

Experience:

• No breakdowns, no safety issues

• No adverse impacts

Preparing for commercialization:
• Fine tuning the software
• System dynamics

roof – pole - turbine

A very early adapter

Number ONE

ĺ

ĸ

On the roof

Other installations

A computer representation