Refrigeration compressors powered by direct current (DC) electrical energy have traditionally been relegated to mobile refrigeration systems, where batteries or vehicle alternators are the source of power. The number of DC compressors produced today for the worldwide market is tiny when compared to the number of AC compressors, mostly reciprocating, rotary, and scroll types largely used in refrigerated appliances and air conditioners. But a recent development, the emergence of solar power and to a lesser extent fuel cells has provided added lift to the entire field of portable power. The result is that mobile refrigeration and portable cooling have been re-energized (both metaphorically and figuratively) creating new opportunities for innovative appliances that do not rely on grid power.