Variable Refrigerant Flow: Demonstration of efficient space conditioning technology using variable speed drives

Variable refrigerant flow, or VRF, systems are popular in Japan for buildings' space conditioning needs, but have a very small market penetration in the United States. These systems are energy efficient and provide considerable comfort to occupants. Highly efficient motors, variable speed drive system and controls are the heart of the VRF technology. This paper provides research conducted by the Electric Power Research Institute (EPRI) of the U.S. by installing a VRF system within nine of the offices at its Knoxville, Tennessee building. The system was relatively easy to install and retrofitting was not an issue. The system provided individual cooling and heating to each office; it was very quiet and operated very well under partial load conditions. Survey conducted by EPRI found that occupants preferred the VRF system over the existing ducted space conditioning system. For a given amount of cooling at an equivalent external temperature, the VRF system exhibited 20-40% reduction in energy consumption, while improving occupants' comfort at the same time. The paper also provides brief update on the motor and drive technology used by the VRF system; this is the under pinning technology for energy efficiency.