Hi! I'm working on a project where we are building a windturbine from the bottom up. Myself and a colleague are designing a double stator axial flux generator for our turbine. Our requirements are that we deliver about 10 W at nominal rotation speed. It's a direct axis driven generator propelled by a VAWT. The issue that has been bothering us is how we determine the size of the generator. We found some rather advanced articles on the back-torque of the machine but are still a bit lost. So to put our concerns into a question. What is a common design parameter that makes a generator too heavy/too light to drive? Thanks in advance!