As of my last knowledge update in September 2021, magnetostrictive systems are not commonly used in HVAC (Heating, Ventilation, and Air Conditioning) systems to convert airflow into electricity. Magnetostriction is a phenomenon where certain materials change their shape or dimensions when exposed to a magnetic field.
Typically, in HVAC systems, the conversion of airflow into electricity is not achieved through magnetostrictive methods. Instead, energy harvesting from airflow is more commonly accomplished using technologies like piezoelectric materials or small wind turbines. These methods involve converting mechanical vibrations or kinetic energy from the moving air into electrical energy.
It's possible that developments have occurred since my last update, so I recommend checking more recent sources or academic research to see if there have been any advancements in using magnetostriction for energy harvesting in HVAC systems.