Energy Consumption of Chillers Reduced by 9.6%

Background

There are three fresh water cooled chillers (900TR in total) and two heat pumps (200TR in total) providing chilled water and hot water to a high technology building.

There are three fresh water cooled chillers (900TR in total) and two heat pumps (200TR in total) providing chilled water and hot water to a high technology building. Ozonation was also used to disinfect that water due to bacteria accumulation. Mineral scale deposit and biofilm were coated on the tubes which required annual tube cleaning to restore the cooling power. The ozonation device required high maintenance costs and shut down occasionally due to malfunctions.

In order to improve the energy efficiency of chillers and heat pumps and maintain the disinfection power when the ozonator was not working, Hydropath technology was installed. The condenser tubes were cleaned and inspected before activating the Hydropath device (Picture 1).  During the test, the ozonation system (the ozonator, air dryer, air compressor, and water pump) were not operated in order to evaluate only the Hydropath performance.

Result

After one year of operation without pre-cleaning of the condenser, biofilm was not detected and existing scale in most area was dissolved as indicated in Picture 2. A sample of the remaining deposit on the tubes was collected and submitted to MRC of Hong Kong Polytechnic University for SEM/EDX analysis. Result shows a high concentration of silicon in a form of silica scale which cannot be dissolved unless higher concentration of acid is used.

Despite some silica scale remaining on the tubes’ surface, the results from the demonstration were successful. There was a 9.6% reduction of energy consumption by chillers and heat pumps, and the ozonation system was discontinued. The investment was paid back in 20 months.

An additional benefit of the installation is the improved condensing water quality with total bacteria count and Legionella count controlled well below the limit.

 
       Water Cooled Chiller

       Water Cooled Chiller

                Heat Pump

                Heat Pump

            Ozonation System

                                        Day 1 - Condenser Tubes cleaned before Hydroflow - Picture 1

                                        Day 1 - Condenser Tubes cleaned before Hydroflow - Picture 1

                                                     1 Year of Operation -   CONDENSER TUBES  - PICTURE 2

                                                     1 Year of Operation -   CONDENSER TUBES  - PICTURE 2