When I last used them, max output was 480 J/t IIRC, but I'm not sure about the J to RF conversion at the time. It was fairly recently, with default configs.However, according to the wiki a wind turbine generates a maximum of 200 J/t, which equals 80 RF/t according to the conversion rate I found. Thus I'd need 125 of them for 10 KRF/t.
Still, with that conversion ratio it's perhaps a bit unpractical if 10k RF/t is needed.