A cooling system (200, 300, 400, 500, 600) comprising: a heat exchanger (210, 306, 528, 632) through which a refrigerant flows, and which rejects heat to a fluid; an evaporator (208, 406) configured to evaporate the refrigerant; a first circuit having an expansion device (214, 328, 422, 510, 520, 612); a second circuit having an expansion machine (202, 318, 420, 526, 610, 616) coupled to a first compressor (204, 308, 416, 418, 514, 516, 618) configured to compress the refrigerant to a first pressure, wherein the expansion machine (202, 318, 420, 526, 610, 616) is a first turbine that is rotationally coupled to the first compressor (204, 308, 416, 418, 514, 516, 618) through a shaft, and the expansion device (214, 328, 422, 510, 520, 612) is an expansion valve; a set of valves (218, 220, 222, 322, 324, 326, 424, 426, 428, 508, 522, 524, 604, 606, 608) arranged to direct the refrigerant through the first circuit, the second circuit, or both the first and second circuits based on ambient conditions; characterized by a second compressor (302, 418, 516) configured to, prior to entering the first compressor (204, 308, 416, 514, 618), compress the refrigerant to a second pressure that is less than the first pressure; and a second heat exchanger (212, 404, 504, 506, 620, 622, 624) configured to cool the refrigerant prior to entering the first compressor (204, 308, 416, 514, 618) but after exiting the second compressor (302, 418, 516); further comprising a refrigerant flow circuit that includes: a heater configured to heat the refrigerant; and a second turbine configured to extract energy from the heated refrigerant that exits from the heater, wherein the second turbine is rotationally coupled to the second compressor. a heat exchanger (210, 306, 528, 632) through which a refrigerant flows, and which rejects heat to a fluid; an evaporator (208, 406) configured to evaporate the refrigerant; a first circuit having an expansion device (214, 328, 422, 510, 520, 612); a second circuit having an expansion machine (202, 318, 420, 526, 610, 616) coupled to a first compressor (204, 308, 416, 418, 514, 516, 618) configured to compress the refrigerant to a first pressure, wherein the expansion machine (202, 318, 420, 526, 610, 616) is a first turbine that is rotationally coupled to the first compressor (204, 308, 416, 418, 514, 516, 618) through a shaft, and the expansion device (214, 328, 422, 510, 520, 612) is an expansion valve; a set of valves (218, 220, 222, 322, 324, 326, 424, 426, 428, 508, 522, 524, 604, 606, 608) arranged to direct the refrigerant through the first circuit, the second circuit, or both the first and second circuits based on ambient conditions; characterized by a second compressor (302, 418, 516) configured to, prior to entering the first compressor (204, 308, 416, 514, 618), compress the refrigerant to a second pressure that is less than the first pressure; and a second heat exchanger (212, 404, 504, 506, 620, 622, 624) configured to cool the refrigerant prior to entering the first compressor (204, 308, 416, 514, 618) but after exiting the second compressor (302, 418, 516); further comprising a refrigerant flow circuit that includes: a heater configured to heat the refrigerant; and a second turbine configured to extract energy from the heated refrigerant that exits from the heater, wherein the second turbine is rotationally coupled to the second compressor. a heater configured to heat the refrigerant; and a second turbine configured to extract energy from the heated refrigerant that exits from the heater, wherein the second turbine is rotationally coupled to the second compressor.