Design study of a narrow line-width, high power IR-FEL facility has been carried out at NSRRC. This machine is designed to synchronize with the U9 undulator radiation of Taiwan Light Source and therefore provide new opportunity for chemical dynamics and condensed matter research. It has been proposed to use a super-conducting linac to provide a 60 MeV high quality electron beam to drive a 2.5-10 microns FEL oscillator with U5 undulator. Operating this linac in energy recovery mode will also be considered as an option to improve overall system effeciency and reduce heat loss and radiation dosage at the beam dump. Performance requirements and outcomes from this preliminary design study will be reported.