A two-dimensional, dynamic finite element model is developed to study the transient characteristics of linear-shaped thermoelectric generators (L-TEG) in this paper. The model considers the effect of an unsteady heat source, which is regarded as a time-varying thermal boundary condition. The temperature-dependent TE material properties are also taken into account. For two loading processes (i.e. heating process and cooling process), we investigate transient TE behaviors of L-TEG under different loading ways and duration of thermal load as well as geometric dimensions of the TE legs, individually. The results indicate that, in heating process, the responses of the power and the absorbed heat to the thermal load present obvious time delay under some certain conditions; in the cooling process, interestingly, an internal heat source emerges in the L-TEG, caused by the delay of thermal diffusion from the hot end of the TE legs to cold end. This heat source renders a heat release from the generator to the ambient. A process relying on its own heat to generate electricity is thus formed. This study further helps the understanding of TE behavior of TE generators in service. (C) 2017 Published by Elsevier Ltd.