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High-efficiency Low-lift Central Cooling System

High-efficiency Low-lift Central Cooling System Secondary Research

Pacific Northwest National Laboratory investigated the efficiency of electricity use by a prototype low-lift cooling system. In comfort-cooling applications, a higher temperature chilled water supply (60-65 degrees F instead of 50 degrees F) indicates lower lift conditions (or head pressure), which lowers the work required of a compressor. We considered a low-lift chiller the following features:

  • Peak-load shifting by active or passive thermal energy storage
  • Dedicated outdoor air supply with enthalpy heat recovery from exhaust air
  • Radiant heating and cooling panels or floor system
  • Low-lift vapor compression cooling equipment
  • Advanced controls at HVAC equipment and supervisory levels

The analysis shows that significant gains in cooling system efficiency can be achieved. Increases in cooling efficiency for a standard-performance building ranged from 47 percent to 84 percent. For a high-performance building, efficiency improvements ranged from 17 percent to 66 percent. This technology could save 5 average megawatts per year over standard practice in new commercial buildings. However, unless the benefits of low-lift cooling systems are significant compared to their cost premium, it is unlikely that these technologies will find widespread acceptance.

Project Team
BPA: Erik Boyer and Jack Callahan
PNNL: Srinivas Katipamula

2008 - 2010


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