Correct Fan Size/Type to Increase Efficiency

Proper selection of the fan type and size and the design of the overall system can have a significant impact of the system performance and efficiency.

  • Size: Oversized fans is a common issue in fan systems and can be a result of the variable demand conditions or conservative design to compensate for uncertainties (such as increased pressure drop over time or plant expansion). However, oversized fans have higher capital, operational costs, may deliver poor performance and require extra maintenance. Consequently, optimal sizing of the fans in the design stage is a key leverage point for energy efficiency and system performance. For existing systems, however, fan replacement can be too costly. Instead, other possibilities can be explored for size correction. These include decreasing fan speed by using a different motor and fan sheave sizes; installing a variable speed drive, or; by using an axial fan with controllable pitch blades (US DOE, 2003. pp.35-36).
  • Type: Axial and centrifugal fans are the two major fan types and each include a number of different designs with advantages and drawbacks in different applications. Choosing the right type of fan for a given context is important for efficiency, reliability and cost. Consequently, optimal fan types should be selected with proper consideration of factors such as  pressure, airflow rate, efficiency, space constraints, noise generation, drive configuration, temperature range, variations in operating conditions, and tolerance to corrosive or particulate-laden airstreams.

Useful guidance on fan selection and location can be found in the resources listed below. 

Development Status Products

Correct Fan Size/Type to Increase EfficiencyCosts & Benefits

Parent Process: Fan Systems
Energy Savings Potential

This measure is estimated to offer following improvement potentials (UNIDO, 2010):
• 18% for low efficiency base cases;
• 11% for medium efficiency bas cases;
• %2 for high efficiency base cases.

Electrical and primary energy savings potential of this technology for different countries is estimated as following (UNIDO, 2010):

  Final (GWh/y)  Primary (TJ/y)
US 2418 26550
Canada 444 5528
EU 1705 16026
Thailand 180 1810
Vietnam 82 1176
brazil 347 3873
CO2 Emission Reduction Potential

Total emission reduction potential, as kt CO2/y for different countries are estimated as (UNIDO, 2010): 

US 1458
Canada 221
EU 743
Thailand 93
Vietnam 41
brazil 51


Estimated typical capital costs of this measure for different system sizes (S) are:
• US $8000  for S < 37 kW;
• US $15000 for 37 kW < S < 75 kW;
• US $25000 for 75 kW < S < 150 kW;
• US $50000 for 150 kW < S < 375 kW;
• US $100000 for 375 kW < S < 745 kW; (UNIDO, 2010)

Cost of conserved energy, expressed as US $/MWh-saved, in different countries are estimated as following (UNIDO, 2010):

US 81.9
Canada 79.9
EU 89.8
Thailand 56.4
Vietnam 56.5
brazil 53.9

Correct Fan Size/Type to Increase Efficiency Publications

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24, 64-76

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19-24,35, 36,