Economizers, often mentioned in association with “free cooling”, are used in a building’s air systems to maximize the use of “free” cold air outside the building, instead of using mechanical cooling to achieve indoor temperature setpoints.
Economizers, often mentioned in association with “free cooling”, are used in a building’s air systems to maximize the use of “free” cold air outside the building, instead of using mechanical cooling to achieve indoor temperature setpoints. In this project, CopperTree was engaged to work with an energy efficiency partner to help analyze a government building in Australia. This particular building had already been optimized for energy efficiency over several years, and presented very little “low hanging fruit” left to further optimize the building’s energy consumption. The building’s Air Handling Units already featured an economizer sequence, which would open the outdoor air dampers to 100% when the outside air temperature was less than the return air temperature from within the building. What wasn’t so obvious, is that temperature is not the only consideration when seeking “free cooling”. Sometimes there is more to the story.
CopperTree’s Kaizen software was used to examine whether the economizer sequence being used in the building was as efficient as it could be. Kaizen’s calculation power was used to take disparate sensors from within the building’s systems and calculate the indoor enthalpy of the return air from the building’s indoor zones. That indoor enthalpy was then compared to a calculated outdoor air enthalpy performed by Kaizen, and the difference in the 2 enthalpy measurements was used to determine when the delta of indoor and outdoor enthalpy required mechanical cooling for dehumidification, regardless of the traditional economizer sequence’s conclusions, since that was only factoring in the delta in air temperature between outside and inside the building. The result was a recommendation for a new economizer sequence that would take into account the difference in enthalpy and recommend the outside air dampers only be opened to a minimum position for ventilation when the conditions show the enthalpy difference was greater than a given threshold.
The changes resulted in thousands of dollars in reduced energy and a significant amount of avoided emissions. These types of counter-intuitive results are common when using a powerful analytics engine like CopperTree’s Kaizen software.
