Accordingly the number of telecommunication base stations is increasing all over the world. Consequently network operators are looking for smart energy management architecture for their base stations. This presentation addresses more energy efficient cooling strategies in order to reduce this figure. Combining air conditioning and free cooling systems (e.g. extracting fresh air into the envelope for the latter) is one of the promising and well-proven methods to reduce energy consumption in base stations. Furthermore, the potential of employing free cooling in either single zone (IT/electronic equipment and batteries in one envelope), or dual zones (IT/electronic equipment and batteries in two separate envelopes) strategies are investigated.

1. Powering the Software Defined Network
Free Cooling: A Complete Solution on
Reducing Total Energy Consumption for
Telecommunication Base Stations
Ehsan B. Haghighi
ehsanbh1@gmail.com
Thermal Designer

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Contents
• Introduction
• Free Cooling
• Energy and Controlling Model
• System Components and Operation
• Single and Dual Zone Strategies
• Case Studies and Results
• Conclusion

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Introduction
• Cooling traditionally counted for 25-50% of
the total energy consumption in a typical base
station.

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Free Cooling
Extracting fresh air into the shelter

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Source: https://www.dantherm.com/

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Facebook data centre in Luleå, Sweden

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Energy Model
INFSOLENVITCOOL QQQQQ 

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Controlling Model
if TSET <= TO+ΔTlag=> Air Conditioning
if TSET > TO+ΔTlag => Free Cooling

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System Components

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System Operation
Free cooling Air conditioning

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Single and Dual Zone Strategies
Single zone strategy Dual zone strategy

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Case Studies
• A typical BTS with L=4 m, W=3 m, and H=2.8 m
• QIT = 4 kW and QBattery = 0.4 kW (on average)
• UEnv = 1 W/m2K and UBattery = 0.5 W/m2K
• ΔTlag = 2 °C
• Tset = 25 °C for the single zone strategy
• Tset = 25 °C (battery compartment) and Tset = 35 °C (IT/electronic) for
the dual zone strategy
• COP = 2.5 and idle fan power consumption for the main air
conditioning system are assumed to 100 W
• The power consumption for the free cooling unit is assumed to be
80 W on average
• In the dual zone strategy a small air conditioning unit with COP of
2.4 and 75% running time is used to provide the required cooling
load for the smaller zone
• The area for the smaller zone is assumed to be 10% of the area of
the main zone

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Locations
• Copenhagen (Denmark), San Francisco (USA), Shanghai (China) and Dubai (UAE)
• Weather data: ASHRAE handbook

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Copenhagen, Denmark

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San Francisco, USA

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Shanghai, China

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Dubai, UAE

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Results
Cooling System Size (kW)
AC FC
Copenhagen, Denmark 5.0 4.9
San Francisco, USA 4.9 4.9
Shanghai, China 5.5 4.9
Dubai, UAE 6.0 4.8

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Copenhagen, Denmark

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San Francisco, USA

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Shanghai, China

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Dubai, UAE

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Results
Savings (%)
Single Zone Dual Zone
Copenhagen,
Denmark
91 85
San Francisco, USA 94 86
Shanghai, China 53 85
Dubai, UAE 21 68

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Conclusion
• Free cooling is a well-proven method to
reduce total energy consumption in a typical
BTS
• Free cooling can be used in either single or
dual zone strategies
• In hot and warm climate zones dual zone
strategy is recommended