The present invention provides provided a hydroelectric turbine having a stator and a rotor, an array of magnets being fixed to rotor and a corresponding array of coils being fixed to the stator, the turbine further including means for cooling the coils during operation of the turbine, the cooling means preferably taking the form of one or more channels passing through the stator, in close proximity to the coils, in order to allow fluid flow through the channels to cool the coils.