How to detect location of a person in a room in the most cost efficient methord

Hello every one.. i am new to this forum and really want some advice from you guys..
how can i detect the location of a person in a room? i am presently designing a controller for a air-conditioner that con detect the location of a person in a room and thus change the fin direction for effective cooling. how do i know the location of the person? also it is a low cost device.. so i cant use costly methords like LCD floor boards or pizo electric pressure sensors.. so plz someone .. any idea??

 

How about an IR thermal sensor /motion detector?
Have it scan the room to detect the hot spot.
Here is a commercially available unit that is often used an an intrusion detector:
http://www.optexamerica.com/productpage.aspx?l1=1&l2=&id=42

Human presence is normally detected by movement of the warm body.
In your case, the warm body would be stationary while the movement would be the physical rotation of the unit (scanner)
The fin alignment could be mechanically coupled to the scanner.

 

yeah thanks man.. the module will be costly for the project i want to make but still it gave a good idea.. thanks again