Capacity factor and generator power per swept rotor area

[PierreB]

@PierreB

From the website:

The TWT-11 produces ~15,000 kWh per year - enough to cover most of a Northern European farm or rural home - 13× more energy per kg of material than traditional small wind.

@dougselsam

In a good wind site (roughly an 11–12 mph or 5 m/s average wind speed), a Bergey Windpower Co. Excel 10 wind turbine produces between 13,600 and 18,000 kWh per year. Under optimal conditions with higher average winds, production can reach up to 25,000 kWh per year. [1, 2, 3]

The Bergey weighs about what, maybe 500 kg? What’s that, about twice what the kiteX turbine weighs? This would mean the more accurate statement would be 2x more energy per kg of material than traditional small wind.

“2x more energy per kg of material”: it is right.

@dougselsam

It seems you may be confusing energy production per kilogram, and energy production per square meter of swept area.

Right.

@PierreB

I would say about 5x by taking account of rotor loading between 234 W/m² (Bergey) and 45 W/m² (KiteX).

It is about swept area.

The higher capacity factor is achieved with a lower rotor loading (W/m²) as wanted by KiteX, so according to the power/swept area ratio, not directly the power/mass ratio. But both power/swept area and power/mass ratios are relevant means to partially assess efficiency.

Also: this comment where KiteX is compared to another 5 kW wind turbine of comparable mass but smaller size and operating with higher winds (nominal wind speed of about 12 m/s, compared to only 7 m/s for KiteX).