Lowering PUEs to save energy

“PUE is calculated by dividing the total power in a data centre by the amount of energy being used by the IT equipment. For example, a PUE of 1 means that all power going into the data centre, is being used to power the IT equipment.

“In order to measure PUE accurately, we calculate the breakdown usage, which allows us to gauge the results of optimisation efforts. We monitor energy usage with a power profile for each rack within a data centre. A power system in a data centre is a critical element in the facility’s infrastructure, as it enables us to determine how much energy is being used in certain areas.

“As energy costs continue to rise, it is becoming more critical to optimise overall energy efficiency and reduce power costs. Therefore it is essential to employ procedures which will keep a data centre’s energy efficiencies on track, and coincide with the Code of Conduct on Data Centre Energy Efficiency. There are a few simple and low cost options which can help businesses reduce a data centre’s energy costs and improve performance, from switching off idle servers, to managing the airflow. Here, we explore a number of options.

Switching off idle servers
“In many data centres, between 5% and 15% of servers are no longer needed for the whole data centre to function, and could be turned off completely. While this isn’t as simple to do as it sounds, even taking small steps and testing this in a controlled environment would benefit the data centre and start to show considerable cost savings. For larger data centres, energy savings of up to 20% can be achieved by doing this.

Turning up the heat
“By turning up the thermostat you can extend equipment life expectancy. It also gives you more time to react in the unlikely event of a cooling system failure. In recent years, server operating costs have generally surpassed acquisition costs; this may make the preservation of hardware less of a priority over cutting operating costs.

Free Cooling
“Free Cooling is one of the best technologies to use to improve energy efficiency, especially during the colder months. The technology utilises cold outside air temperatures, allowing an external chiller to reduce or even stop its compressors from working, and cool the data centre with cold air from the ambient environment.

“Internal CRAC (computer room air conditioning) units featuring Free Cooling technology as well as external independent free coolers can be installed to work alongside a data centre, offering savings of up to 70% and PUEs of 1.1.

Reusing data centre heat in office spaces
“Energy savings can be doubled, by allowing hot air exerted from data racks to heat up office spaces in the colder months. Often the heat generated from a data centre, will provide more than enough heat to replace a traditional heating system.

Airflow management
“Airflow management is an essential part in data centre management, as it ensures separation between hot and cold air; any temperature fluctuations could result in data racks overheating and cause potential downtime.

“Contained cold aisles prevent air from mixing and can be managed with perforated floor tiles for cool air to filter up through the floor, and into the front of the data racks. Other options to separate the air include plastic sheet curtains which can be hung over the front of the racks to contain the cold aisle, and sheet metal placed in front of empty rack space to prevent hot air from mixing.”