We have used a thermoelectric cooler and a coldness-recovery device (CRD) for summer air conditioning of a train carriage. The coldness-recovery device is a countercurrent heat exchanger. This air-conditioning system is described in terms of a heat-exchanger network for which we have developed computer software (GOLAM2-R). We have simulated six different control scenarios for the energy system. Use of the coldness-recovery device produces a higher COP than an increase of the Peltier coefficient for the thermoelectric cooler or an increase of the insulation thickness of the train-carriage wall.