The world is addressing the challenge of achieving adequate energy production to satisfy demand at the same time as minimising pollutant emissions. We know that alternative energy sources are essential for achieving a positive balance for the environment. In addition to biomass and solar, wind power is one of the most ecological forms of energy generation. For example, a state-of-the-art offshore wind farm could save up to 45 million tonnes of CO₂.

To analyse and fine tune the environmental performance of its wind turbines, Siemens Wind Power and Renewables  publishes Environmental Product Declarations or EPDs, one for each of the four of the company’s product platforms for both onshore and offshore wind power. The results are based on the life cycle assessments or LCAs of two offshore wind farms with 80 wind turbines and two onshore projects with 20 wind turbines.

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How can payback time be calculated?

The calculation of payback time constitutes one of the fundamental elements of the LCA. It represents the period over which the wind farm must operate in order to generate an amount of energy equivalent to the energy it will consume throughout its life cycle. For an onshore wind farm with an average wind speed of 8.5 metres per second, the payback time for a Siemens wind turbine (SWT-3.2-113 model) is four and half months. This calculation is based on a project with 20 wind turbines, including a 13km grid transmission line. To carry out the calculation, various factors have specifically been taken into account such as the consumption of materials and the costs of manufacturing, installation, operation and maintenance, in addition to dismantling and processing at the end of the life cycle.

The data yielded by the life cycle assessment for Siemens’ offshore wind farms is also convincing. Based on a project involving 80 Siemens D6 wind turbines, over the course of its useful life, the wind farm generates 53 million MWh and results in a saving of 45 million tonnes of CO₂, an amount that could equal the CO₂ absorbed by a 1,286km2-forest over a period of 25 years. This figure corresponds to emissions of just 7g/kWh, compared to the global average emissions of 865g/kWh from energy generation using fossil fuels.