Like any manufactured item, there is an environmental cost to the manufacture of renewable energy hardware. Wind turbines, for example, require considerable raw material inputs and energy to create the final product. In an effort to quantify these inputs, Danish turbine manufacturer Vestas undertook a life cycle assessment of their latest wind turbine.

What they found, according to their research, is that one of the company's V90, 3.0 MW offshore wind turbines has to generate electricity for approximately 6.8 months before it produces as much energy as is used during the manufacturing lifetime. This, they say, means the turbine model earns its own worth more than 35 times during its energy production lifetime.

Furthermore, compared to the V80-2.0 MW offshore wind turbine, the 6.8 months constitutes an improvement of approximately 2.2 months over the lower capacity model.

If installed on a good site, the V90-3.0 MW wind turbine will generate approximately 280,000 MWh in 20 years - thus sparing the environment the impact of a net volume of approximately 230,000 tons of CO2, as compared to the figures for energy generated by a coal-fired power station.

Both examples were the results from a life cycle assessment (LCA), which Vestas completed of a V90-3.0 MW wind turbine in 2004.

A life cycle assessment is both a mapping and an evaluation of the potential impact of the wind turbine on the external environment throughout its lifetime. The life cycle assessment for the V90-3.0 MW wind turbine is divided into four phases.

- The production phase, which covers the period from obtaining the raw materials to the completion of the wind turbine

- Transport of the wind turbine components and erection of the wind turbine

- Operation and maintenance throughout the 20-year design lifetime of the wind turbine

- Disposal of the wind turbine.

"The life cycle assessments are used as a natural and important decision-making tool in product development and in the choice of production technology," said Svend Sigaard, President and CEO of Vestas Wind Systems. "With life cycle assessments of our wind turbines, we have an excellent tool to compare the products and estimate how big an advantage our wind power systems are to the environment."

Sigaard said the company now plans to make life cycle assessments of all their wind turbines.