The ‘axial flux’ Permanent Magnet Generator

 Our 'axial flux' turbines are specifically designed and built to extract maximum power from modest wind speeds (cut-in speed of 3m/s) with maximum efficiency and minimum complexity. The turbine alternator’s direct-drive configuration has been developed to absorb any amount of power that the blades can deliver at any given wind speed over its total operating range. Its 3 blades are hand-carved from seasoned African hardwood and profiled with an aerofoil cross-section to obtain the maximum energy from the wind. This ensures the rotor will rotate at 7 times the speed of the wind speed (tip-speed factor 7). The axial flux wind turbine has been primarily developed for 12-volt battery charging, and ideally suited for use with an inverter to convert the 12, 24 or 48-volt battery direct-current (DC) into main 230/240-volt alternating-current (AC).

The Clean Energy Company fabricates 3 turbines sizes and blade diameters 1.8-metres (350watts), 2.4-metres (800watts), and 3.6-metres (1,000 watts).

   

Our turbines are built with strength and durability to withstand abuse (natural and man-man). They can operate in the harsh conditions in Mozambique where they will be pushed to their limits. Because of their simple back-to-basics design, they can be locally maintained and repaired without complication.   

Technical specifications:

Blade diameter:

1.8m

2.4m

3.6m

Peak Power rating:

350 watts

700 watts

1,000 watts

Mean wind speed: 3m/s

12 kWh

22 kWh

49 kWh

Mean wind speed: 4m/s

30 kWh

54 kWh

122 kWh

Mean wind speed: 5m/s

53 kWh

93 kWh

210 kWh

Mean wind speed: 6m/s

74 kWh

131 kWh

296 kWh

Mean wind speed:  7m/s

92 kWh

164 kWh

369 kWh

Cut-in wind speed:

3.0m/s (blade tip speed 21m/s).

Optimal wind speed:

10m/s (blade tip speed 70m/s).

Alternator design:

Multi-pole (ceramic magnet) rotor.

Electrical Output:

3-phase AC (bridge rectified to DC).

Blade construction:

Wood.

Number of blades:

3.

Speed/power control:

Side-furling gravity-return yaw system.

Configuration:

Upwind rotor, off-set tail furling.

Max design wind speed:

45m/s.

Recommended tower:

8-12 metres.

Each turbine is individually tailored and built from locally available metal sourced from local supply networks to suit site and user specifications. We use an African heavy metal fabrication techniques (welding, hammering and grinding) to ensure our turbines will last for 10-15 years with minimum maintenance. Eventually if something does break through long-term fatigue or abuse, repair can be easily carried out using the many widely-available local repair facilities. Our Zero Waste (cradle-to-cradle) principle gives the local fabrication of turbines true sustainability.

 

The rotor blades are hand-carved from seasoned hardwood, an excellent material due to its strength, workability, and excellent fatigue properties. Our local team of highly experienced 'Fundis' (professionals) produce all our sub-components, including our wooden rotor blades. They are an essential part of our network of local suppliers we support and encourage. For example, our blades are crafted by Twaire (a master Fundi), his four carpenters and three young apprentices. Our team are true innovators when it comes to integrating local fabrication techniques, RE thinking and appropriate technology.

       

 

 20 May, 2010