1. SWT Wind Turbine Generator Range

2. Wind Turbine Output Variables The primary goal for a wind turbine is to: Produce the maximum kWh’s in a given time period at a given location At the most reasonable cost

3. Potential for Higher Efficiency AWEA in 2009 identified 3 main areas: NowPotential Blade design32%42-45% Generators65-80%90-92%* Inverters90+%not much *GMI design efficiencies for the 10, 20 & 40 kW models are 94%, 95.5% and 96.5% respectively, already higher than AWEA’s target for improvement.

4. Key GMI Design Principals To get a higher power to weight generator it is necessary to increase the diameter of the generator which increases the output to the square of the diameter increase. In traditional PMG generators this can be limited by the extra weight imposed by the requirement of increased internal structural re-enforcement. The GMI design turns the generator in on itself resulting in this limiting point being ‘pushed’ further up the scale The result is a lighter weight, smaller, more efficient generator.

5. Generator Models As per the SWT brief, GMI has designed a family of wind turbine generators based on GMI’s core technology, three models are being developed:  G101-10  G102-20  G103-40 To ensure the widest range of applications, these models have been optimised for outputs of 10, 20 and 40 kW. Reflected by the last two digits in the model designation codes

6. Model Propeller Ranges (12m/s wind and 40% efficient props) 5.5-9 m dia 8-13 m dia 11.5-17.5 m dia G102-20

7. Model Output Ranges (12m/s wind and 40% efficient props at various prop diameters)

8. Design Constants Output increases to the square of the diameter increase - OR - Output increases directly proportional to the length.

9. Key Generator Loss Principles There are three key types of generator losses:  Iron Losses  Copper Losses  Friction and Winding Losses

10. Copper Losses Copper losses are related to generator RPM. Copper losses = I squared r r = resistance of windings I = current

11. Iron Loss Principles Are related to the generator rpm and pole numbers Reduction of iron losses leads to a steeper efficiency curve Increasing the generator stack length results in a proportional increase in iron losses Iron losses increase to the square of the rpm Iron losses increase to the square of the number of generator poles

12. Iron Loss Calculation Iron Losses = (frequency/50)^2 x iron quality constant x weight of stator laminations Frequency = (rpm/3000x50) x number of poles/2

13. Overall Loss Principles Practical implementation of these principles in the design process for a generator means: Increasing the efficiency of a generator from 90-95% you need to be able to halve the iron losses To further increase efficiency from 95- 97.5% it is necessary to halve the iron losses again.