18 May 2017

O.3.7.1 Combined Liquid Chiller and Heat Pump Systems for Data Centre Cooling with High-Temperature Heat Recovery

Due to the accelerating use of the Internet, telecom equipment and other network-based services, the number of large-capacity data centres is showing an accelerating growth rate. There are currently more than three million data centres globally, and the electricity consumption of these centres is substantial. Relatively few computer cooling systems are based on free (natural, renewable) cooling or apply high-efficiency heat recovery systems. However, there is a strong trend towards “green data” centres with minimum primary energy use and low greenhouse gas emissions. Since low- and medium-temperature heat recovery systems have rather limited applicability, different cooling technologies with energy efficient high-temperature heat recovery have been developed and utilized the recent years. These include single-stage, two-stage, cascade and compression/-absorption (hybride) liquid chiller and heat pump systems with ammonia (R717), ammonia-water (R717/R718), R134a or HFO-1234ze as working fluids as well as CO2 (R744) liquid chillers and heat pump water heaters. Examples of some of these eco-friendly state-of-the-art technologies are found in Norway, and include a 800 kW single-stage ammonia (R717) system at the Norwegian University of Science and Technology (NTNU), Trondheim, and a 350 kW CO2 (R744) system at the University Hospital in North-Norway, Tromsø.