someone plz suggest me some project on how to conserve energy through mechanical ways...in AC

i hope you mean(AC= Air conditioner )
make an efficient circuit breaker (for switch off the system) when live load is not present..
or make efficient controller for ergonomic conditioning
Increasing the efficiencies of insulation in various places in your home (reduce leak of heat)
or do some thing to improve efficiencies of compressor motors

---

or RECYCLE rejected HEAT AC to clothes-dryer through an appropriate filter ,or water heater....etc