Analysis
Spatial planning of offshore wind farms: A windfall to marine environmental protection?

https://doi.org/10.1016/j.ecolecon.2009年07月01日3 Get rights and content

Abstract

Wind farms are often planned offshore where wind conditions are favourable and the visual impact is less important. Wind farms have both positive and negative effects on the marine environment. Negative effects include bird collisions, underwater sounds and electromagnetic fields, whilst positive effects constitute functioning as artificial reef and acting as no-take zones for fish, with possible spill-over effects.
This paper presents a spatially explicit framework to analyze effects of wind farms on the marine environment and aims to evaluate how wind farms can contribute to protection of the marine environment through strategic and economically viable location choices.
The functioning and the applicability of the model are demonstrated in a numerical example for the Dutch exclusive economic zone. We find that the careful spatial planning of wind farms is a key factor for profitability and environmental protection, and that, if carefully planned, the environment can benefit from offshore wind farms.

Introduction

Wind energy is one of the current major candidates for renewable energy generation. Compared to fossil fuels it has the advantage that it is CO2 neutral when generating energy. In fact greenhouse gas emissions only take place during the construction, maintenance and decommissioning phases (Lenzen and Munksgaard, 2002). Moreover, if one accounts for the subsidies to other energy sources, and takes current carbon credit prices as a proxy for the damage costs of carbon emissions, wind energy is competitive with regular power sources (The Economist, 2008).
Total wind power installed in the EU by the end of 2007 was 56,535 MW, or 3.7% of its total energy demand (European Wind Energy Association, 2008). This amount is significantly higher then the target set for 2010 by the EU, which was 40,000 MW (European Commission, 1997).
This success story has a flip side: wind farms often meet local resistance. Considerations such as equity, fairness and landscape intrusion lay at the basis of such resistance (Christensen and Lund, 1998, Wolsink, 2000, Ek, 2005, Wolsink, 2007). Moreover, turbines cause noise, shadow flickering, electromagnetic fields and disturbance of animals and habitat, by causing collisions with birds and bats, and acting as barriers against migration and foraging (Burton et al., 2001; Mathew, 2006, Van der Wal et al., 2006). Because these effects vary strongly with location the spatial dimension is pivotal in tradeoffs between wind energy and its environmental effects.
Wind parks are located offshore to avoid landscape intrusion and noise. The offshore environment has other advantages as well, such as stronger and steadier winds and large continuous areas, enabling the establishment of large wind farms. Offshore winds are less turbulent, thus decreasing the fatigue load and increasing the lifetime of the project. Finally the reduced occurrence of wind shear allows shorter towers (Henderson et al., 2002, Mathew, 2006). Disadvantages of offshore wind farms are higher investment costs for foundation, the distance to the main electrical grid, and improved equipment needed because of the harsh environment, which causes quick corrosion and makes maintenance difficult (Henderson et al., 2002, Mathew, 2006).
Ecological effects of locating wind farms offshore can be both detrimental and beneficial. Wind farms negatively affect the marine environment through avian collisions (Exo et al., 2003, Drewitt and Langston, 2006), underwater noise (Koschinski et al., 2003, Wahlberg and Westerberg, 2005, Thomsen et al., 2006) and electromagnetic fields (Gill, 2005, Petersen and Malm, 2006, Öhman et al., 2007). There are positive effects too on local biodiversity as the turbines can act as artificial reefs and no-take zones, and there is evidence of spill-over effects (Petersen and Malm, 2006, Wilhelmsson et al., 2006; Fayram and De Risi, 2007). The impacts on biodiversity and ecosystem functions should therefore be considered in location choice.
Wind farms yield the highest net revenues if located in areas with high wind speeds (which increases energy generation) and areas with low average seafloor depths at closest proximity to the shore (both of which diminish costs).
In this paper we analyze the problem of finding the optimal location for offshore wind farms, by considering both economic and ecological aspects. We develop and use a spatially explicit model that includes energy generation as well as the effects on bird and fish species. The model maximizes the revenues from wind farms under constraints for ecological impacts related to bird collisions and impacts on fish stocks.
Few of the large number of economic and ecological models of spatial planning of offshore wind parks have integrated economic and ecological considerations in one framework. The model of Kooijman et al. (2001) calculates costs based on an engineering model and a GIS module that covers the North Sea. Elkinton et al. (2005) focus on the layout of the offshore wind parks. Planning systems for businesses have been developed by Resoft (2008), Garrad Hassan (2008), EMD (2008) and BMT Renewables (2008). All of these models calculate costs, but none of them consider the effects on species or ecosystems explicitly, although the models of Garrad Hassan, Resoft and EMD include modules for landscape intrusion. Ecological models focus mainly on the effects of wind farms on birds. These include sensitivity maps by Garthe and Hüppop (2004), a turbine specific collision risk model (Tucker, 1996) and a spatial planning model (Van der Wal et al., 2006). Elliott (2002) has formulated a conceptual model but does not quantify relationships. Moreover, none of these models consider economic choices explicitly.
The contribution of this paper is that it considers both spatial economic choices and local ecological effects. We present a modelling framework that spatially allocates offshore wind farms, taking into consideration spatial variations in wind speed, distance to the shore and sea floor depth, and presence and dispersal of bird and fish populations. We demonstrate how the model can be applied to the Dutch EEZ, where concerns of renewable energy, biodiversity and fisheries rank high on the political agenda. The aim of the paper is to illustrate some of the choices faced in spatial planning of offshore wind parks as well as the potential of the model in analyzing this problem.
The paper is organised as follows: the next section presents a more detailed analysis of offshore wind farms and their effects. It continues with the formulation of the model and the illustration of how it can be applied to the Dutch EEZ. Finally, discussion and conclusions are presented.

Section snippets

Integrated assessment of offshore wind farms

Earlier conceptual integrated assessment models of offshore wind energy (e.g. Elliott, 2002) were based on the Drivers-Pressures-States-Impacts-Responses (DPSIR) framework. Another conceptual model, the Scene model, has been suggested by Rotmans (1998), and constitutes the inventory of social, economic and natural stocks and their relations.
We use the framework of Hein (2005) to describe the ecosystem and economic system and their relationships in a more explicit way then the DPSIR framework (

Discussion and conclusions

In this paper we presented a modelling framework to spatially allocate offshore wind farms in order to maximize revenues while accounting for other economic activities, and protecting birds and fish populations (i.e. razorbill and plaice in our example). Four different scenarios were analyzed for the Dutch EEZ, and we conducted a sensitivity analysis.
The analyses show that the allocation of turbines in the Dutch EEZ is quite robust against changes in parameters. Basically two regions are

Acknowledgements

The authors would like to acknowledge the support of the MARBEF network of excellence. We also would like to thank L. Machielse and two anonymous referees for their useful comments on an earlier draft of this paper.

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