An Original Approach Combining CFD, Linearized Models, and Deformation of Trees for Urban Wind Power Assessment

Jan Konopka,Andreas Matzarakis,António Lopes

doi:10.3390/su10061915

Abstract

Wind energy is relevant to self-sufficiency in urban areas, but the accuracy of wind assessment is a barrier to allowing wind energy development. The aim of this work is to test the performance of the Griggs-Putnam Index of Deformity of trees (G-PID) over urban areas as an alternative method for assessing wind conditions. G-PID has been widely used in open terrains, but this work is the first attempt to apply it in urban areas. The results were compared with CFD simulations (ENVI-met), and finally, with the linear model WAsP to inspect if deformed trees can offer acceptable wind power assessments. WAsP (meso-) and ENVI-met (micrometeorological model) showed similar results in a test area inside the University of Lisbon Campus. All trees showed a deformation with the wind direction (S and SE). The mean G-PID wind speed for all trees was 5.9 m/s. Comparing this to the ENVI-met simulations results (mean speed for all trees was 4.25 m/s) made it necessary to adapt the index to urban terrains by reducing each Index Deformation class by about ~2 m/s. Nevertheless, more investigation is needed, since this study is just a first approach to this integrated methodology. Also, tree species and characteristics were not taken into account. These questions should be addressed in future studies, because the deformation of trees depends also on the tree species and phytosanitary conditions.

Highlights

In times of uncertainty related to climate change, the reduction of anthropogenic emissions of greenhouse gases to mitigate global warming and the use of renewable energies, such as solar and wind power energy, are alternative solutions to the consumption fossil fuels and nuclear power [1,2]
Looking at the wind flow characteristics in mesoscale urban areas, statistics show in a study concerning the wind speed modification in summer due to urban growth in Lisbon that the wind speed at 10 m height in the city is up to 30% lower than in open terrain [5]
Recent research [11] proposed a U-DTM methodology to assess wind power viability in a location to the west of the city of Lisbon. In line with these kinds of techniques, the methodology we propose in this research combines biomonitoring (G-PID: wind data through observation of wind-driven tree deformation [12,13]), linear (WAsP), and CFD (ENVI-met) modeling for the assessment of wind power potential in urban environments, where wind data is difficult to obtain

Summary

Introduction

In times of uncertainty related to climate change, the reduction of anthropogenic emissions of greenhouse gases to mitigate global warming and the use of renewable energies, such as solar and wind power energy, are alternative solutions to the consumption fossil fuels and nuclear power [1,2]. To achieve this “energy revolution”, it is important to know the potentials (energy payback, GHG decrease, etc.) and the limitations (energy supply system, storage, etc.) of new energy systems [2]. Wind power could be one of the best options for producing sustainable energy systems, especially near windy coastal areas like the city of Lisbon [4]

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Discussion

Conclusion