In reply to Jeffrey Metcalf.

Please allow me to chime in on this.

I do have experience with close coupled cooling. We identified years ago that the power density increases would lead to a day when forced-air cooling would no longer be practicable. I had several spaces where there just was no good solution to the heat load.

The rear-door evaporator (heat exchanger) captures the heat from the air before it leaves the cabinet so no hot air exists anywhere within the data hall. Since we no longer have to move air mass across the room to and from bulk evaporators, the cost of infrastructure to support higher heat density levels has been reduced to parity, even as low as 6kW. We calculate the comparative cost per unit power will be much less at heat loads above 6kW up to at least 30kW. While the forced air model may not even be able to achieve that density.

The server fan speed ramp up was troubling for us until we got away from the forced-air model. Because there is much less hot/cold air combination, most of our server fans are running slower, quieter and consuming less power. The only hot air leakage is within the cabinet but that has been reduced since the heat exchanger has a fan pulling the air from the cabinet.

It took us awhile to work through it all but now we think this system is actually much less complex than forced air. All the airflow problems have been eliminated thus operation is substantially simplified. As an added benefit our efficiency improved.

We were able to avoid many space related problems. We delayed or eliminated moving to larger buildings and space expansion projects. Even if these system cost much more to build, it would still be a relative bargain.

We have also worked to optimize our power distribution as well. Once we abandoned the status quo, we were able to find ways to deliver more power per cabinet for half the money, with less loss.

There is definitely no free lunch. I would say that if you double the size of your facility, you would have to nearly double the length of fiber and other cable runs, those are crazy expensive. You can double a list of other items too; super structure, fire suppression, taxes, insurance, roof to leak, cleaning, lighting, foot steps to perform maintenance, and rent.

I do encourage power densification as a cost savings strategy.