A ‘putty-practically-clay’ vintage model with R&D driven biases in energy-saving technical change

This paper deals with the problem of tackling the adverse effect of output growth on environmental quality. For this purpose we use an intermediate sector that builds ‘putty-practically-clay’ capital consisting of an energy-raw capital amalgam used for final goods production. The putty-practically-clay model is a strongly simplified version of a full putty-clay model, that mimics all the relevant behaviour of a full putty-clay model, but that does not entail the administrative hassle of a full putty-clay vintage model. In addition to this, we introduce an R&D sector that develops renewable- and conventional energy-based technologies. The allocation of R&D activities over these two uses of R&D gives rise to an induced bias in technical change very much as in Kennedy (1964). In the context of our model, this implies that technological progress is primarily driven by the desire to counteract the upward pressure on production cost implied by a continuing price increase of conventional energy resources. Hotelling’s rule suggests that this price rise is unavoidable in the face of the ongoing depletion of conventional energy reserves. By means of some illustrative model simulations we study the effects of energy policy on the dynamics of the model for alternative policy options aimed at achieving GHG emission reductions. We identify the conditions under which energy policy might partly backfire and present some non-standard policy implications.