Air Cooling Versus Liquid Cooling

I seem to have gone over this a hundred times, but wanted to get feedback from the community. Has anyone out there been able to really make liquid cooling work in their data center considering the additional space utilization and expensive price point.

We've found that liquid cooling vastly more expensive than what we are doing and am curious what some out there might be doing.

For us we've found that high density air cooling (top down, and capped hot/cold row configuration, and overhead air extraction) can get us to a max density of about 10 kW per rack. We use a chilled water system for the additional HVAC needed to get us above the standard 5 kW max, but this is for the air handlers themselves and not chilled water for the in row rack cooling. The problem is the in row chilled water cooling makes us lose a cabinet of space for every cabinet of higher density. For this to work (simple situation) we would need to attain rack densities of at least 20 kW given the loss of floor space.

We use APC Cabinets and infrastructure and even they have said if you try and get about 20 kW with the liquid cooling it becomes problematic. Given these governing characteristics in addition to the overwhelming cost, is anyone out there actually pursuing this in a colocation environment. To me it just doesn't seem to make sense.

Perhaps the cost needs to come down, but even then what are you gaining if it is a 1 for 1 trade off.