In recent years, the HVAC industry has witnessed the evolution of three distinct approaches to advancing energy efficiency. For decades, the industry focused on improving full-load efficiency before the current shift to part-load efficiency standards for equipment. Today, new part-load rating methods better account for how equipment operates at off-design conditions when loads vary hour by hour. The next stage in the evolution of building energy efficiency will focus on whole building efficiency for facilities.
This first installment of a two-part series will examine the evolution of equipment-efficiency standards from full to part load and their relationship to whole-building efficiency. The second article will look at how HVAC technologies are advancing to modulate capacity to match variations in building loads, a major factor in improving whole-building energy performance.
Continued Energy Savings Predicted
The energy performance of buildings is expected to improve significantly in the decades ahead. From 1980 to 2009, for every percent of growth in U.S. commercial building space, primary energy consumption grew by 1.19%. The U.S. Energy Information Administration estimates, however, that from 2009 to 2035, every percent of growth in space will increase energy consumption by only 0.79% — a 33% improvement in energy savings.
That raises the question: How will those predicted energy savings be obtained?
Considering that approximately 40% of the energy in commercial buildings is consumed by HVAC equipment, it's reasonable to conclude that mechanical system efficiency will have to improve substantially to achieve those results. Consequently, HVAC equipment designers must look for new solutions to old challenges. To improve the efficiency of mechanical equipment, system designers face the perennial thermodynamics problem: how to move heat from one place to another using the least amount of energy.
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