It looks like Dracaena fragrans 'Massangeana' - one that hasn't formed a woody trunk yet. The reason it's wilting during the day is the sunlight - these plants do not appreciate direct sun. Dappled sunlight (like that beneath a tree canopy) is okay, but not full on sunlight. If you can, move it somewhere it gets bright daylight, but no direct sun, or very little sun, maybe just an hour at the end of the day. If you have no place out of direct sun, then try to arrange some shading for it. The other possible causes are temperature fluctuation, they prefer a stable temperature always above 17 deg C, and possibly excessive wind exposure. Hopefully there's a drainage hole in the bottom of that pot too...