How to convert normal inverter into Solar inverter?  

you don't need to buy a solar inverter by selling yours old normal inverter at cheaper price.. actually you can convert into solar inverter with introduction of solar panel and charge controller (prefer automatic)..
here we converted our normal inverter (880VA ups and 12V 150AH battery) into solar inverter by using solar panel 330watt 24Volts DC and solar charge controller..
converstion controller:
Take a look at this LUMINOUS SHINE 2420 PWM Solar Charge Controller on Flipkart
dl.flipkart.co...
solar panel:
Luminous BIS Certified Polycrystalline 330 Watt Solar Panel For Home With PID Resistance Technology and Severe Weather Resilience (24 Volt) amzn.eu/d/7wQiiUf
Bgm courtesy BEN SOUNDS