For most building and facility managers, maintaining comfort and reducing energy and capital equipment costs is high on their list of priorities. Achieving this involves identifying and resolving equipment issues that can negatively impact building efficiency, thus reducing comfort, increasing operating costs and capital expenditure.
Today, the pursuit of an energy-efficient infrastructure, is forcing organizations to explore ways to efficiently reduce energy waste and corporate carbon footprints. As such, they can no longer afford to dismiss the untapped energy and facilities savings that exist across their building portfolios.
What is Adaptive Energy Management (AEM)?
Since HVAC systems take up a large part of a building’s energy consumption, it stands to reason that facility managers should look for ways to make sure that their HVAC systems are running as efficiently as possible, in order to reduce energy use.
In a bid to lower energy usage, and save costs, some facility managers set, non-standard higher temperature setpoints both when their buildings are occupied and unoccupied. However, this neither saves money nor energy. Doing so actually places more stress on the system since it ends up working outside of its original design criteria, failing to ever make occupied setpoint during peak heat periods, leading to increased wear and tear, even more energy usage during peak demand times, and more equipment breakdowns, hot calls, truck rolls and maintenance costs.
To reduce energy spend, facility managers need to understand load shifting and thermal mass cooling and how they can leverage these concepts to maximize building efficiency.
What is Load Shifting?
Raising the setpoints by an extreme amount, > 4 - 5 degrees, when the building is unoccupied isn’t a good idea because, not only does your HVAC system continue to work even harder during peak periods to reach the occupied setpoint, the building also stores up additional heat throughout the night.
During the day, cooling units have to work extremely hard to achieve the occupied setpoint. However, it never reaches this point because the building was allowed to overheat during the night and HVAC systems do not have the cooling capacity to quickly overcome the initial heat load stored in the thermal mass of the building.
Load shifting isn’t about increasing the intrinsic efficiency of the RTU (rooftop air conditioning unit). It, however, reduces the heat load on the building and shifts dealing with the majority of the remaining heat load to a more efficient time, when it’s cooler outside.
You should start the system up early and/or run it periodically overnight (when energy costs are low) to reduce the heat stored in a building’s thermal mass, making it easier to achieve the setpoint when the building is occupied during the day.
What is Thermal Mass Cooling?
If your building overheats during the night, no amount of cold air coming from your RTU is going to make a difference. This is because the RTU only cools the air coming down and does nothing about the heat energy contained in the beams, floor slab, metal girders, and supports of the building.
Essentially, the core objective of thermal mass cooling is to use the building itself to reject heat energy. The building is used as a “battery” of sorts to store cold energy during the night (when loads on the HVAC system is low because of the cooler night air and energy is cheap).
The process of thermal mass cooling is a core concept in Adaptive Energy Management. AEM focuses on cooling the building infrastructure and contents down so they can be used to store “cold” energy, enabling it to overcome radiant sun energy during the day.
For part 2 of this post series, click here.
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