Embodied Energy Analysis of New Zealand Power Generation Systems

Abstract

Embodied energy is the energy consumed in all activities necessary to support a process in its entire lifecycle. For power generation systems, this includes the energy cost of raw material extraction and transportation, plant construction, energy generation and the recycling and disposal stages following actual use. Embodied energy analysis is a crude method of estimating the environmental impacts and depletion of natural resources consequent to a certain process. In effect, the higher the embodied energy of a process, the greater the green house gas emissions and the depletion of the natural resources.

This thesis presents the embodied energy analysis carried out on some New Zealand power plants belonging to various methods of generation, namely, natural gas combined cycle (NGCC), natural gas open cycle (NGOC), wind, reservoir hydro and run of river hydro power plants. The analysis was carried out using a combination of process chain analysis and input output analysis, which are the two fundamental methodologies for embodied energy analysis. It follows the standards set out by the International Organisation for Standardisation 14040 series, and uses some guidelines given in the International Federation of Institutes for Advanced Study workshop on energy analysis methodology and conventions.

From the analysis, it was found that for renewable generation power plants, the exploration and plant construction phase of the lifecycle contributes the largest amount of embodied energy, while for the non renewable power plants, the largest amount of embodied energy is contributed by the plant operation and maintenance phase of the lifecycle. The lifecycle energy payback ratio, which corresponds to the ratio of electrical energy output over the total lifecycle energy input, of the power plants are 96.9, 62.8, 7.96, 0.487 and 0.354 for run of river hydro, reservoir hydro, wind, NGCC and NGOC, respectively. Therefore, the lifecycle performance of renewable electricity generation is superior to non renewable electricity generation. Hence, the environmental impacts and depletion of natural resources from non renewable electricity generation is higher than renewable electricity generation. From the generation methodologies, hydro power plants have exceptional performance characteristics.