When it comes to cooling technology, the biggest selling point today is the environmental factor, especially energy efficiency. But just a decade ago, energy efficiency wasn’t even a consideration in the buying equation.
Remember when most data centre cooling systems were direct expansion (DX) systems? Back then capital cost was the most important selling point. It was all about price.
Electricity consumption and energy efficiency were secondary considerations and the decision making was about financial comparisons and benefits.
Today, it almost seems as if energy efficiency is the only selling point for DX chiller manufacturers.
No data centre designer installs a chiller system without knowing its COP (Coefficient Of Performance).
But environmental considerations are not restricted to energy efficiency. Green considerations aren’t just a selling point but an essential fact of life - energy efficiency and cost savings should go hand-in-hand.
New technology also means there isn’t just a single solution available but a range of options for customers to consider.
One solution is concurrent free cooling. In addition to energy savings generated from reducing the need for DX cooling, concurrent free cooling maximises the part-load efficiencies of components such as EC fans, inverter-driven pumps and centrifugal compressors.
EC fans are up to 50 per cent more efficient than AC fans at part load and by using temperature sensors and sequencer controls cooling can be staged between DX cooling and free cooling. Sites with an air-cooled and free-cooling chiller can use the sequencer to put the free cooling chiller to work when the ambient is low.
Another innovative data centre cooling solution has been introduced by telecommunications company MTN, which launched a concentrating solar cooling plant at its head office in Roodepoort, west of Johannesburg.
The plant generates enough electricity to power 350 average-sized homes. It uses a technology called Linear Fresnel Concentrating Solar Power, which uses heat generated from the sun and has a peak cooling capacity of 330kW.
The project forms part of a worldwide program coordinated by the German Energy Agency. The system is made up of 242 solar mirrors covering an area of 484 square metres. These mirrors track the sun to generate pressurised hot water at 180°C. The hot water in turn powers an absorption chiller that produces chilled water circulated into the data centre for cooling IT equipment.
The mirrors follow the movement of the sun, based on GPS location, orientation and the date and time. This information guides the system to track the sun to concentrate on the central absorber tube where heat is generated.
The absorption chillers employ a lithium bromide water solution, which uses water as the refrigerant. In a special feature entitled “Then and Now” published in the September 2013 edition of CCN, WT Sustainability director Steve Hennessy, said chillers have experienced a quantum leap in efficiency in the last 20 years.
“The biggest change is improvements in chiller efficiencies which has made an important dent in building energy consumption,” he said. “Chillers are usually the single most energy hungry component of a HVAC system so doubling the workload with no increase in energy consumption is pretty impressive.”
While variable speed drives are nothing new, Hennessy said falling prices have made them ubiqitous. “We see them on fans, pumps, chillers and, in the case of the latter, they are a significant factor in the delivery of high efficiencies,”
he said.
“Twenty years ago many in the industry took the view that if loads are high just install more equipment. Back then energy was cheap. Now we question everything.”