Complex sentence: The Betz limit is based on an open disk actuator; if a diffuser is used to collect additional wind flow and direct it through the turbine, although more energy can be extracted, the limit still applies to the cross-section of the entire structure.
Split into simpler sentences: The Betz limit is based on an open disk actuator; if a diffuser is used to collect additional wind flow and direct it through the turbine, more energy can be extracted. The limit still applies to the cross-section of the entire structure.