A heat exchanger assembly for cooling a heat-generating component, such as a generator or power electronics module, within a wind turbine nacelle comprises a thermoelectric element, such as a Peltier element, having a first section arranged in a first region of relatively high temperature in contact with the heat-generating component or in the vicinity thereof, and a second section arranged in a second region of a relatively low temperature. The thermoelectric element is configured to transfer heat from the first region of relatively high temperature to the second region of relatively low temperature with consumption of electrical energy. A source of electrical energy is provided for the thermoelectric element, and a control unit may be provided for controlling the energy supply in order to control the temperature of the component or surface area cooled by the thermoelectric element. A further cooling element including a so-called heat pipe may be provided to enhance cooling efficiency.