My friends's father has a small supermarket and he has a cold room he'd like to light up with as many lumen per watt as possible so the heat will be minimal. I've been considering the Cree XLamp XM-L2 and the HLG-120H 120W Single Output Switching Power Supply.

I'd like to make this for him and connect 16 PCS of the Cree XM-L2 in each lamp fixture then hook it up with a suitable driver. I am not good at this but I'd like to learn much more. Can I just put the LEDs in series and get the 48V driver?

Remember that my friend's father would like as little heat and as much lm/w as possible from this fixture, he needs 4 fixtures and I am keen on doing a perfect job for him.