Comparing the environmental impacts of offshore and onshore wind farms with the life cycle analysis method: The example of Turkey

Today, with increasing energy demands, interest in renewable energy sources has increased globally. In this context, wind energy systems stand out among renewable energy sources with their efficiency and increasing investment rates. Globally, wind energy installation, which was approximately 200 gigawatts (GW) in 2010, has exceeded 1000 GW by 2023. Although Turkey is a country surrounded by seas on three sides and onshore wind power plants are widespread and operated, there are no offshore wind power plant investments and installations on its coasts yet. However, the Ministry of Energy and Natural Resources has set the offshore wind energy investment target as 5 GW for 2035, and Hoşköy, Bozcaada, Bandırma and Karabiga have been identified as suitable regions. Within the scope of this thesis, the environmental impacts of onshore and offshore wind turbines that can be located at different depths have been evaluated and comparatively analysed by Life Cycle Analysis (LCA) method. The analysis was carried out in different impact categories on the basis of unit energy megawatt/hour (MWh) generated. The research focussed on the wind power plant investments in Karabiga offshore and Karabiga onshore areas in the Marmara Sea, which have been declared suitable by the ministry. LCA was applied with midpoint and endpoint methods for 3 MW and 5 MW onshore, 5 MW shallow offshore and 6 MW deep offshore wind turbines. During the environmental impact comparisons, the environmental impacts of onshore and offshore wind farms are quite different depending on their location and the equipment used. In addition, the comparison of offshore wind farms at different sea depths provides different environmental impact results. In the most general result of the study, according to the apparent, midpoint and endpoint environmental impact analyses, the environmental impacts of material extraction-processing, construction-transportation and operation-maintenance were taken into consideration. In this context, according to the midpoint approach, the highest potentials that appear in the analyses made in the 6 MW deep-sea wind turbine are, respectively, global warming 1.63E+01 kg CO2 eq/MWh, terrestrial acidification 3,05E-01 kg SO2 eq/MWh, freshwater eutrophication 4,43E-02 kg P eq/MWh, marine eutrophication 1,79E-02 kg N eq/MWh, human toxicity 9,70E+01 kg 1,4-DB eq/MWh, photochemical oxidant formation 1,18E-01 kg NMVOC eq/MWh, particulate matter formation 1,34E-01 kg PM10 eq/MWh, terrestrial ecotoxicity 1,02E-02 kg 1,4-DB eq/MWh, freshwater ecotoxicity 2,01E+01 kg 1,4-DB eq/MWh, marine ecotoxicity 1,73E+02 kg 1,4-DB eq/MWh, agricultural land occupation 5,61E-01 m2a eq/MWh, urban land occupation 6.64E-01 m2a eq/MWh, natural land conversion 3.75E-03 m2 eq/MWh, metal depletion 4.09E+01 kg Fe eq/MWh, fossil depletion 3.91E+00 kg oil eq/MWh. Other high potential values are ozone depletion 7,72E-02 kg CFC eq/MWh for 5 MW shallow offshore wind turbine and ionising radiation 3,46E+01 kg kBq U235 eq/MWh for 5 MW onshore wind turbine. When the values normalised according to the endpoint approach are weighted and reduced to a single indicator, the highest values are photochemical oxidant formation 8.98E-06 pt, ionising radiation 8.78E-03 pt for 6 MW deep offshore wind turbine, respectively, terrestrial acidification 1.97E-03 pt, freshwater eutrophication 4.76E-03 pt, terrestrial ecotoxicity 1.71E-02 pt, freshwater ecotoxicity 1.46E-02 pt, marine ecotoxicity 4.22E-02 pt, agricultural land occupation 1.87E-01 pt, urban land occupation 1.28E-02 pt, natural land conversion 6.05E-04 pt. In addition, the highest values for 3 MW onshore wind turbine are human health global warming 4,16E-02 pt, ozone depletion 4,52E-07 pt, human toxicity 3,31E-03 pt, climate change ecosystems 4,63E-03 pt and fossil depletion 4,37E-02 pt, respectively. The other highest impact is particulate matter formation from 5 MW onshore wind turbine 1.59E-02 pt.