Energy Saving and Acoustical Optimization - Fan Retrofit for Existing Installations
1.4 Retrofit and Upgrading Existing Fan Installations
Estimations show that energy consumption of fans with electric drives will rise from 344TWh in 2005 up to 560TWh until 2020 within the EU. This corresponds to the energy production of roughly 140 large power plants (4 TWh per power plant). With improving the fans there is a chance for energy saving up to 34TWh until 2020. This corresponds to a reduction of the CO2-emission of 16 million tons per year or 8.5 power plants.
More than 50% of the existing Climate- and Air Conditioning units in offices or industrial buildings are older than 25 years. During this period there was a noticeable increase in efficiency of modern fans related to optimizations of electric motors and improvements on the aerodynamic side.
The biggest potentials for energy saving lies in the replacement of antiquated fans and an adapted control-strategy that can deliver “tailored ventilation” based on the needs of the people who live or work inside the building. Replacing inefficient components is one way to improve existing units and typically much cheaper than buying a new Climate- or Ventilation unit. Therefore Retrofit of fans increases the lifetime of existing units for many years. As the replacement is done within the existing building environment usually no additional licenses are needed from public authorities for these projects.
A second way is to replace modules within the units that may have more functions integrated then just ventilation.
Retrofit itself will not only have a positive impact on environment and the financial expanses of companies, with the new and improved control function of the fans it will also increase the comfort for users and at the same time there is a chance to decrease noise level.
The presentation will show approaches to improve the energy efficiency and the acoustical behavior of fans in different applications. On the one hand there is room for improvement with regard to the electric drive (electric motor)
• Motor optimization: Replacement of AC-motors with energy efficient EC-motors. EC-motors use electronical commutation and permanent magnets to reduce losses within the motor
• Today’s EC-motors have different Control functions. Speed control can be used to decrease power consumption (Power consumption Pe ~ Speed n³).
On the other hand aerodynamic optimization leads to higher overall efficiency and better noise values of fans
• Centrifugal fans: Change from inefficient forward curved blowers to fans with backward curved impellers. Fans with forward curved impellers have high losses during conversion of dynamic pressure into static pressure. Fans with backward curved impellers have much lower dynamic losses as static pressure is already generated within the impeller. With an additional scroll housing the dynamic energy of backward curved fans can be further reduced to reach best efficiency values.
• Typical losses for axial fans are the kinetic energy at the outlet of the fan and the swirl created by the rotation of the fan. Increasing the outlet area (diffuser) will reduce the outlet air velocity, guide vanes can reduce the swirl. Both will reduce losses and therefore improve efficiency.