AC drive in heating, ventilation and air conditioning (HVAC) applications
Abstract: The majority of HVAC applications where ac drives are used are fans, pumps and compressors. Applying ac drives for fans, pumps and compressors, energy saving is large. 40% of all energy in Europe and North America is consumed in buildings. Thus energy consumption by buildings is dramatically reduced with AC drives.
In heating, ventilation and air conditioning (HVAC) applications, the main processes are related to heating, cooling, drying and circulating air. Supporting processes are mostly related to taking the extra heat out of the building, or providing additional heat energy to the building.
The majority of HVAC applications where ac drives are used are fans, pumps and compressors.
Ac Drives for Fans and pumps of HVAC applications:
Using ac drives to control the fan or pump output rather than using dampers, vanes, valves or on/off control brings substantial energy savings, if the required output is less than nominal most of the time.
Ac drive controls the speed of the pump and fan by changing the electrical energy supplied rather than damping the air- or water flow. It is like reducing the speed of a car by pressing less on the accelerator instead of using the brake to slow down the speed. The payback time of an ac drive here is typically one year or less.
Other benefits of using ac drive to control the speed of fan or pump in HVAC applications are:
1. Smooth ramp up and down causes less stress to the mechanics of fans and pumps and to air ducts and water piping.
2. Slowing down the speed rather than damping the output will result in lower noise levels.
3. Tuning the heating, ventilation and air conditioning (HVAC) system during and after the commissioning is easier when the flexibility of an ac drive is used
Ac Drives for Compressors of HVAC applications:
Compressors in heating, ventilation and air conditioning (HVAC) are often used in chillers for cooling water, which again is used for cooling air. Utilising ac drives in compressor applications will potentially bring energy savings compared to on/off control.
Energy savings are achieved by optimising the system setup of compressor, chilled water circulation and condenser water circulation. The optimum set point for chilled water temperature and condenser water temperature is based on outdoor and indoor temperature and humidity.
Energy savings
The energy savings are most effectively achieved by tuning the system rather than optimising individual functions.
The ac drive gives the flexibility of tuning the setup of the system to operate in the most energy efficient operational point.
Other benefits with ac drive include:
- Reduced number of starts and stops reduces the wear of the compressor.
- The piping and mechanics are stressed less in ramp up or down situations.
- Reduced noise level in low load situations.
- Possibility to use high speed compressors.
Summary
40% of all energy in Europe and North America is consumed in buildings. The biggest share of this energy is consumed in Compressors in heating, ventilation and air conditioning (HVAC) applications. With the rising energy cost and concerns about the CO2 levels and global warming, it is crucial to use all means available to reduce the energy consumption in HVAC applications. The savings potential is large.
The key thing is to start looking more at lifetime costs of heating, ventilation and air conditioning (HVAC) system, where energy cost plays a big role, rather than the initial investment in HVAC system. For example, 90 per cent of the lifetime costs of the pump or fan is energy.
