Life cycle of a wind turbine

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Life cycle assessments of a windmill, from cradle to grave. What about the environmental impact?

Windmill

While the Earth’s resources are dwindling, and we are seeing significant fluctuations in raw material prices, the world’s population is growing—and thereby also the number of people living the life of the Western world, contributing to sky-high energy consumption levels. Therefore, circular economy is one of the hottest topics to be focusing on at the moment.

Proponents of circular economy believe, among other things, that we need to replace the throw-away mentality with the cradle-to-grave principle. Products must be repairable or upgradable and materials reusable.

This attitude places great demands on manufacturers, as they need to focus on environmental improvements at all stages of a product’s life.

Holistic approach

Life cycle assessments are one of the methods companies can apply to form a general view of how to benefit from making their products more sustainable.

Life cycle assessments are carried out by registering all environmental impacts associated with the production, maintenance, and disposal or recycling of a product. This is a holistic approach, analysing all stages of the product’s life.

DTU has been leading the way within this area since the 1990s. Stig Irving Olsen, Associate Professor in the Quantitative Sustainability Assessment division at DTU Management Engineering, has been involved since the very beginning, and he is currently witnessing a growing interest in life cycle assessments. Not least among decision-makers:

“The EU Commission is planning on using this method in connection with the Product Environmental Footprint initiative, which is aimed at developing a harmonized method for calculating how products affect the environment,” he says.

Companies have also discovered how they can make use of life cycle assessments—both as a development tool and in their branding.

Wind turbine lifespan

One of these companies is Siemens Wind Power, which completed a long-term project last year aimed at preparing a so-called Environmental Product Declaration (EPD) of four different types of wind turbines. Therefore, they carried out life cycle assessments to analyse the energy consumption associated with the production, installation, maintenance, and disposal of four different sizes of onshore and offshore wind turbines.

One of the major questions Siemens Wind Power was trying to find the answer to was the extent of the return on investment in terms of energy produced for each of the four wind turbine types over the approx. 25 years in operation—all factors considered.

Tine Herreborg Jørgensen, Senior EHS Specialist at Siemens Wind Power and project manager, says:

“The overall objective was to demonstrate to both our customers and to politicians the high level of sustainability of the energy produced by wind turbines compared to fossil fuels. We also wanted to take a closer look at which parameters we can adjust to become even more sustainable in future,” she says.

Therefore, Tine Herreborg Jørgensen asked DTU for help—more specifically Alexandra Bonou, who is a PhD student at DTU Management Engineering.

An average wind turbine

Analyses of four types of Siemens wind turbines

Wind turbine G 2.3 MW
located onshore, 100 per cent ROI in less than five and half a months and produces 47 times more energy than it consumes.

Wind turbine D 3.2 MW
located onshore, 100 per cent ROI in terms of energy in less than four and half a months and produces 57 times more energy than it consumes throughout its operating life.

Wind turbine G 4.0 MW
located offshore, 100 per cent ROI in terms of energy in the course of ten and a half a months and produces 23 times more energy than it consumes.

Wind turbine D 6.0 MW
located offshore, 100 per cent ROI in terms of energy in the course of nine and a half a months and produces 33 times more energy than it consumes.

The aim was, among other things, to create four ‘average’ wind turbine cases based on knowledge and data from various experts in the organization which they could use for carrying out their analyses.

“The structure of a large, multinational company such as Siemens is actually perfect for performing this type of analyses due to the large amount of data just waiting to be collected. The challenge is, on the other hand, to say stop, because you can just keep on going,” says Alexandra Bonou.

Motivating factor

The life cycle assessments of the four different types of wind turbines have now been carried out, and the results of the project team showed, among other things, that an average 6 MW Siemens offshore wind turbine has returned the investment in terms of energy after nine and half a months, and that it produces 33 times more energy than it consumes in the course of its approx. 25 years in operation.

This means that an offshore wind farm with 80 wind turbines of the same type will reduce the level of CO2 in the atmosphere by 45 million tonnes during its operating life compared to fossil fuels.

 

live-cycle-stages_størreLife cycle assessments are carried out by registering all environmental impacts associated with the production, maintenance, and disposal or recycling of a product.

The calculations include all stages of the product’s life, from the acquisition of raw materials to the disposal of the product at rubbish tips or recycling the product.

It is a very time-consuming, scientific process requiring extensive knowledge of all influencing factors throughout the life of a product and the ability to conduct extensive calculations based on the collected data.

A series of norms have been developed to ensure that life cycle assessments are carried out in accordance with standardized principles and frameworks.

Adapted from article by Signe Gry Braad, Dynamo – DTU’s quarterly magazine in Danish.

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