Performance evaluation of a variable speed DC compressor

Direct current compressors are strong candidates to be employed in energy-efficient refrigeration systems, especially for renewable energy powered units, as these compressors do not require additional components such as a power inverter that an alternative current compressor would require. This study represents experimental performance analysis of a direct current type refrigeration compressor implemented in a 79 L refrigerator. Energy usage reduction and operational improvement potential of the direct current compressor via variable speed operation were investigated. Experiments were carried out at variable speed operation and four different constant speed operation modes of the compressor. Temperature, pressure, and power input measurements were obtained every 30 s. The experimental data were analyzed in terms of energy and exergy efficiencies. The comparison showed that variable speed operation of the direct current compressor can be much more efficient than constant speed operation of the direct current compressors, especially at higher speeds.

► The energy efficiency of refrigerators is improved by varying the speed of a DC compressor.
► Utilizing solar energy in refrigeration systems is considered.
► Determination of optimum speed for variable speed DC compressors is discussed.
► Variable speed DC compressor can have higher thermal and exergy efficiency.