We looked into this for a while for some of our products and even filed some ip (such a waste of time).  We were doing it with thermopiles on our vents and using a buck and boost.  It worked for heating well, maybe well enough for cooling, but was price prohibitive (would up retail 50% at least).  <a href="https:&#x2F;&#x2F;flair.co" rel="nofollow">https:&#x2F;&#x2F;flair.co</a>