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Inside Microsoft's European Cloud Hub

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A hot aisle containment corridor under construction in the Microsoft data center in Dublin, Ireland. The containment system using a fixed structure, with the cabinets housed in a fitted opening in the side. The hot aisle enclosure has a entrance (green end door) for admin access. (Photo: Microsoft)

DUBLIN, Ireland -  If there's a poster child for Ireland's ideal climate for free cooling, it would be the huge data center in Dublin that powers Microsoft's online services in Europe. The average annual temperature ranges between 23 and 80 degrees F (-5 to 27 degrees C), allowing Microsoft to use free cooling - the use of fresh air to cool servers - year-round under normal operating conditions.

“Free cooling” - also known as air-side economization – allows facility owners to dramatically reduce the amount of energy used in cooling. Chillers, which are used to refrigerate water, are widely used in data center cooling systems but require a large amount of electricity to operate.That allows Microsoft to use less energy than in its data centers in some other areas of the world, operating at a Power Usage Effectiveness (PUE) of 1.17 in its newest data halls.

To take full advantage of the cool climate, the Microsoft data center is designed to perform as a giant air handler.  Cool outside air comes into the facility through intakes on the rooftop air handers, and then flows through a duct system into the data center. The air moves through the servers, and exits in the hot aisle, where it is contained and vented through a plenum that returns it to the air handlers.

These photos over an overview of the path the air follows as it makes its way through the Microsoft Dublin facility:

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The Microsoft Dublin data center went live in 2009, when more than 303,000 square feet of space was put into operations. A second phase was added in 2012. The building totals 550,000 square feet. (Photo: Microsoft)

An aerial view of the Microsoft data center in Dublin showing the rooftop air handler units atop the first phased of the facility, as well as the vacant roof space available for additional air handlers as the remainder of the facility is built out .

An aerial view of the Microsoft data center in Dublin showing the rooftop air handler units atop the first phase of the facility. (Photo: Microsoft)

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These rooftop air handling units drive cooling system for the Microsoft Dublin data center. These units take outside air and draw it into the data center for use in the air conditioning system. This practice, known as “free cooling” or air-side economization, – allows facility owners to dramatically reduce the amount of energy used in cooling. (Photo: Microsoft)

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THese louvers can be open and closed to control the flow of fresh air into the Microsoft data center. Once the air enters the facility, it passes through filters (at right) to ensure that particulates don't enter the server area. (Photo: Microsoft)

Unfinished data hall at Microsoft DB 4 data center shows hot aisle containment units (note that the plenum goes all the way to the ceiling) ready for server racks to be positioned against the containment area.

This new data hall at Microsoft's facility in Dublin shows hot aisle containment units (note that the plenum goes all the way to the ceiling) ready for server racks to be positioned against the containment area. (Photo: Microsoft)

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Here's a view inside the contained hot aisle, where warm air exits the rear of the servers and exits through the top of the data hall. It can either be vented to the outside, or in winter months can be mixed with incoming fresh air to regulate the temperature in the server hall. (Photo: Microsoft)

A diagram of the air economization (free cooling) system at the new Microsoft data center in Dublin, Ireland (click for larger version of image)

A diagram of the air economization (free cooling) system at the new Microsoft data center in Dublin, Ireland (Graphic: Microsoft)

For more details on Microsoft's push to improve the performance and efficiency in Dublin, see our feature story, Squeezing More Efficiency Out of Microsoft's Cloud.