Freeze energy costs by up to 70 per cent
Free cooling is a fast, effective and economic method of utilising low external air temperatures to assist in the cooling of water for industrial temperature control applications or in HVAC (heating, ventilation and air conditioning) system applications. Within industrial temperature control applications a free cooler is installed in series with the chiller system’s evaporator so in lower ambient conditions, partial or 100 per cent free cooling can be achieved.
According to the Met Office, last year the UK experienced some of the lowest temperatures on record during the winter months. Free cooling could have saved many process or HVAC applications thousands of pounds in energy costs. When in low ambient conditions, free cooling methods remove the need to utilise the chiller’s compressors, and utilise the external cold air to cool water through the free cooler, which in turn is used for a process or building’s cooling needs.
There are two main options available to achieve free cooling:
• a chiller working alongside an independent free cooler, and
• a chiller with an integral free cooling coil.
A dedicated independent free cooler is designed to maximise the energy efficiency benefits of a circuit, and is not restricted by the size of a chiller. An independent free cooler has a greater capacity for heat exchange as it is sized to maximise efficiency, enabling a greater area for the transfer of thermal energy.
An independent free cooler is installed in series with the chiller system’s evaporator, so that in lower ambient temperatures, partial or 100 per cent Free Cooling can be achieved, and can result in massive energy savings. This method of operation utilises naturally low ambient temperatures, and in doing so, benefits from a reduction in energy costs which can reach as much as 70 per cent.
By combining a class A energy-efficient scroll compressor chiller with an independent free cooler, maximum savings can be achieved when compared to standard screw compressor chiller.
As the ambient air temperature drops three to five degrees below the required process supply water temperature, 100 per cent free cooling can be achieved and consequently providing an environmentally friendly and cost effective approach to process and HVAC cooling.
Free cooling can be applied to both new chillers and existing systems through the use of free coolers which are uniquely balanced to provide the greatest levels of efficiency at full and partial loads.
Where space is limited, free cooling can be achieved through integral Free Cooling coils. The units are designed to offer high energy efficiency levels in all seasonal conditions and provide a more compact footprint.
Whichever avenue of free cooling is adopted, the benefits remain constant: system reliability as each system monitors temperature and automatically switches from 100 per cent compressor load to partial or total free cooling as climate conditions allow; use of ambient air temperature in place of compressors to facilitate free cooling and savings on running costs; and less wear and tear on chiller components and consequently a reduced life-cycle cost.
Adam Spolnik, director at ICS Cool Energy, discusses a recent project in Cork, Ireland. “Aptus units were installed on the roof of a data centre which allowed the site to utilise the low external air temperatures to send chilled water to the CRAC units (computer room air conditioners) inside the data centre. The free cooling technology is capable of achieving high EERs (energy efficiency ratios) at both full and part load conditions. Therefore working continuously throughout the year, the data centre would only have to run the compressors for approximately 3,000 hours per year with the remaining 5,760 hours just using power to run the pumps and fans.”
High temperatures from the data centre, coupled with low ambient air temperatures mean that the compressors’ running hours are significantly reduced, providing the site with a significant cost saving and helping it to achieve a PUE (power usage effectiveness) of approximately 1.15.
Craig Hodgson, operations manager at ICS Cool Energy in Ireland adds: “A modern data centre operating with a chilled water flow temperature of approximately 15°C could achieve 100 per cent free cooling for eight months of the year (based on the average mean ambient temperatures) and the remainder of the year would offer partial free cooling helping to reduce the load on the chillers. Partial free cooling is achieved when the ambient temperature is approximately 1°C lower than the return water entering the free cooling unit.
“Free cooling can almost double the life expectancy of the chillers by reducing the wear and tear on them, helping lessen life cycle costs. If the free cooling systems were ever to fail, the chillers around the system would still be functioning so there would be no interruption to the process or data centre.”
Adam Spolnik is director at ICS Cool Energy
