مطالعه مقایسه ای پیشرفت های فنی در صرفه جویی انرژی در یک مدل سرمایه محصول

We analyze the hypothesis about the effectiveness of energy saving technologies to reduce the trade-off between economic growth and energy preservation. In a general equilibrium vintage capital model with embodied energy saving technical progress, we show that positive growth is only possible if the growth rate of the energy saving technical progress exceeds the decreasing rate of the energy supply.

Fossil fuel – more precisely petroleum and its refinery products – is an essential input in all modern economies. It has been argued that the limited availability of this basic input and the stabilization of greenhouse gases concentration call for a reduction of fossil fuel consumption. However, the reduction in petroleum consumption could have a negative impact on economic growth and development through cutbacks in energy use (Smulders and de Nooij, 2003). Therefore, there is a clear trade-off between energy reduction and growth. Some authors (see, for instance, Carraro et al. (2003)) suggest that this trade-off could be less severe if energy conservation is raised by energy saving technologies. In this paper, we re-examine the exhaustion problem of fossil fuel. In particular, we study the previous trade-off in a general equilibrium framework with energy saving technical progress. This model based on Boucekkine et al. (1997), considers an economy with exogenous energy saving technical progress embodied in the new equipment. As Baily (1981) observes, technical advances are typically incorporated to the economy through investment. Therefore, the old capital goods get less and less efficient over time, which might well induce the firms to scrap them (obsolescence). In our economy, we assume that different vintages of capital coexist in each period. Since new vintages are less energy consuming, firms may decide to replace the oldest and less efficient vintage. Indeed, if we model the idea of minimum energy requirement to use a machine by assuming complementarity between capital and energy inputs, finite scrapping time is optimal (Boucekkine and Pommeret (2004)). This idea is implemented in our paper, and it is consisted with the empirical evidence put forward by Hudson and Jorgenson (1974), or Berndt and Wood (1975). Our model incorporates two new elements with respect to the standard framework. First, we assume embodied technical progress in contrast to the typical neoclassical specification of neutral and disembodied technical progress. Second, we consider a vintage capital model, with endogenous scrapping decision. The standard models consider homogenous and infinitely lived capital stock. We perform a comparative study to contrast constant and decreasing returns to scale, for two possible scenarios: constant (optimistic) and decreasing (pessimistic) exogenous energy supply. We find that, under the assumption of existence of a balance growth path defined by constant growth rate of all the endogenous variables and constant scrapping age, constant returns to scale1 achieves positive long run growth if the growth rate of the energy saving technical progress exceeds the decreasing rate of the energy supply. The paper is organized as follows. In Section 2, we describe the general case model, with the representative consumer’s problem and the rules that depicts both the optimal investment and the scrapping behavior of firms. The balanced growth path is presented in Section 3, where we show the necessary conditions for its existence in both constant and decreasing returns to scale. Finally, some concluding remarks are considered in Section 4.

We analyzed the hypothesis about the effectiveness of energy saving technologies to reduce the trade-off between economic growth and energy preservation. In order to incorporate the role of technology replacement, we developed a general equilibrium model, where the output is produced by a vintage capital technology with endogenous scrapping rule. New vintages obsolete old machines because of their lower energy requirements. Constant and decreasing returns to scale are distinguished to develop a comparative study. Under constant returns to scale and optimistic context (constant available energy supply), long run growth is possible (Proposition 1). In this case, the (exogenous) growth rate of the economy equals the (exogenous) growth rate of energy saving technical progress. However, considering a more realistic situation of gloomy scenario (decreasing available energy supply), our economy only can achieve long run growth if the growth rate of the energy saving technical progress excess the decreasing rate of the energy supply (Proposition 2). Here, the growth rate of our economy is given by the difference between the growth rate of energy saving technical progress and the decreasing rate of the energy supply (i.e., γ−γesγ−γes). Furthermore, when we assume decreasing returns to scale, the economy achieves balanced growth path only for the gloomy case; nevertheless, our economy does not exhibit growth in the long run. However, we could escape from the decreasing returns to scale incorporating additional elements such as learning-by-doing, human capital, subsidies, etc. The constant scrapping age and the reduced availability of energy (which affects the economy through the energy prices and the minimum energy requirements) explain our results in both constant and decreasing returns to scale. We found some empirical values for the growth rate of energy saving technical progress (γγ) and the decreasing rate of the energy supply (γeγe). About γγ, the work of Azomahou et al. (2004) finds an annual growth rate of energy saving technical progress for the USA around 1.9%. As to γeγe, the Uppsala Hydrocarbon Depletion Study Group (Uppsala University) forecasts (up to 2050) an annual decreasing rate of oil supply around 1.8% for the total world.14 In conclusion, we could have compatibility between economic growth and energy preservation adopting energy saving technologies. However, the growth rate of the energy saving technical progress has to be greater than the decreasing rate of the energy supply to ensure a positive long run growth. Since in our model energy saving technical progress is exogenous, an interesting extension is considering that the economy endogenously decides the growth rate of energy saving technical progress. An R&D sector of energy saving technologies could be a good way to study this problem.