A staged complementary pressure swing adsorption system and method for low energy fractionation of a mixed fluid. Two beds in a four-column PSA system are selective for component A, and another two columns are selective for component B. The cycle creates an intermittent A and B product, using the purge effluent from the complementary product fed at an intermediate pressure. This intermittent product is used as purge gas for low-pressure purged elsewhere in the cycle using appropriate storage tanks. The use of an intermediate pressure in this cycle enables continuous production of purified component A and B without the use of compressors. Columns may also be configured to enable pressure to equalize between complementary columns.