A data center cooling system includes a cooling liquid supply conduit fluidly coupled between a cooling plant and an air-to-liquid heat exchanger positioned to receive a heated airflow from one or more racks. At least one rack supports a plurality of heat-generating electronic devices. The system further includes a cooling liquid return conduit fluidly coupled between the cooling plant and the air-to-liquid heat exchanger; and a heat transfer module thermally coupled to the cooling liquid supply and return conduits between the cooling plant and the air-to-liquid heat exchanger. The heat transfer module includes a cold side and a warm side, with the cold side thermally coupled to the cooling liquid supply conduit to transfer heat from a flow of a cooling liquid in the cooling liquid supply conduit to the warm side of the heat transfer module, and the warm side including a heat sink.