Ángel Jiménez

Large-eddy simulation of spectral coherence in a wind turbine wake

This work is mainly dedicated to the study of the characteristics of spectral coherence of turbulence fluctuations in wind turbine wakes. A computational fluid dynamics (CFD) code has been implemented using a large-eddy simulation (LES) approach, which is thought to be conceptually more suitable for studying the turbulence evolution in a wind turbine wake. Comparisons with experimental data from the Norrekaer Enge II Windfarm, in Denmark, and with an analytical model proposed by Panofsky and Dutton have been performed, and the results are found to be in reasonable agreement with both.

Efficiency of a standard gas-turbine power generation cycle running on different fuels

This paper presents a study of second-law efficiency in a standard Brayton combined cycle power generation, using several paraffinic fuels ranging from methane to heptane. The main objective of the study was to identify a trend with the number of carbon atoms in the compound. In this way, a qualitative criterion can be built to evaluate the properties of poor-quality gas turbine fuels containing significant amounts of C2+ hydrocarbons from the point of view of exergy. This is important in the current energetic scenario, where new blends are being studied as alternative to natural gas for economic, environmental or availability reasons. The results show a decreasing trend in exergetic efficiency with heavier compounds.

Analysis of the behaviour of biofuel-fired gas turbine power plants

The utilisation of biofuels in gas turbines is a promising alternative to fossil fuels for power generation. It would lead to significant reduction of CO2 emissions using an existing combustion technology, although significant changes seem to be needed and further technological development is necessary. The goal of this work is to perform energy and exergy analyses of the behaviour of gas turbines fired with biogas, ethanol and synthesis gas (bio-syngas), compared with natural gas. The global energy transformation process (i.e. from biomass to electricity) has also been studied. Furthermore, the potential reduction of CO2 emissions attained by the use of biofuels has been determined, considering the restrictions regarding biomass availability. Two different simulation tools have been used to accomplish the aims of this work. The results suggest a high interest and the technical viability of the use of Biomass Integrated Gasification Combined Cycle (BIGCC) systems for large scale power generation.