How do I cut my grill space in half?

I've got a pretty big charcoal grill. The grill space is at least 18" by 36". I'm usually using a whole chimney of charcoal to get the internal temp up to 250F and a chimney and a half to get it closer to 300F. This is great when I'm throwing parties and need lots of food. When it's just me and my girlfriend, I'm not looking to use a lot of charcoal. I'm wondering if there's a more efficient way to get half of the grill up to 350-450. Can I use a divider of some sort to keep only half of the grill hot?