The challenge in terms of sustainability:
A study by the Borderstep Institute for Innovation and Sustainability has estimated that servers and computer centers consumed approx. 9.7 TWh of power during 2011. In a typical computer center, Borderstep calculates that climate control and UPS systems consume around 40 % of all power used there. As a result, sustainable operations in computer centers also mean integration of green cooling into building services.
The typical situation:
Most computer centers use compression refrigeration for climate control, with high levels of power consumption throughout the entire year. An integrated free-cooling system, however, eliminates the need for power for cooling during winter. Under conditions of low outdoor temperatures, free cooling can completely remove the heat produced indoors. As outdoor temperatures increase, however, operating expenses also rise. The compressor then starts to produce the required cooling. At this point, there are additional possibilities for energy savings, as detailed below.
The solution – sustainable technology:
The savings potential of the Adia-DENCO® results from combination of indirect free, and adiabatic cooling. Adiabatic cooling is especially effective for application in moderate to cold climate zones. At outdoor temperatures below 17 °C, the indirect free cooling of the Adia-DENCO® is sufficient to dissipate the heat load. Additional sources of cooling (adiabatic sources or optional compression refrigeration) do not operate under these conditions. At cool outside temperatures, the EC fans in the outdoor air flow operate in their lower speed range. At outdoor temperatures above approx. 17 °C, the control system adjusts the fan speed and switches the adiabatic cooling on. In this transition zone, the control system uses the respective prevailing water and power costs to determine the point at which support from the adiabatic system is most economical than the use of free cooling alone. This minimizes operational costs.
Adiabatic cooling – i.e., cooling by evaporation – takes place with the Adia-DENCO® in a large double-plate heat exchanger. This heat exchanger humidifies warm outdoor air, which reduces its temperature. The water is directly sprayed onto the plates of the heat exchanger – which leads to high cooling performance and requires little space. By hermetically sealed heat exchange, the dual recuperator then cools the warm return air from the computer center. In other words: the air in the computer center is cooled the whole year in recirculated-air mode, and the air flows are hygienically separated from each other.
Depending on the cooling requirements from the computer center, and only at outdoor temperatures over approx. 29 °C, an optional, integrated, conventional chiller can – as peak-load cooler – support the indirect adiabatic cooling. This solution with chiller can, if requested, also be designed as a backup unit.
The sustainable benefits:
Within the context of the German Act on Renewable Energy and Heat, the Adia-DENCO® enables resource-saving coverage of up to 100 % (depending on location) of the energy required for cooling a computer center – since refrigeration recovery through adiabatic processes is recognized under the Act as a use of environmental heat energy. The potential savings in operating costs are more than 75 % over conventional cooling systems (depending on location). In comparison to a combination of conventional chillers plus free cooling, savings are over 50 %.