Abstract
Different operating conditions and alternatives for treatment and replacement of old 225 kW wind
turbines (WTs) were evaluated from a life cycle perspective from cradle to grave. Indicators were
calculated for primary fossil energy requirements (MJpf/kWhel), CO2 emission (CO2/kWhel) and
economy (€2004/kWhel).
Extending the service life ten years by renovation results in 32% lower primary energy requirements
than if the WT is recycled after 20 years at the end of the technical service life. The primary fossil
energy requirement for electricity production is 2.5 - 4.6 times higher for fossil based electricity
production than for WTs. The energy payback time was calculated to 3.9 months for 225 kW WTs and
to 2.7 months for 2 MW WTs. This means that after 3.9 months electricity production, the WT starts
to generate net electricity.
The CO2 emission for WTs was calculated to 7.2-11 g CO2/kWh, which is 4.6 lower than the average
Swedish electricity mix and 122 times lower than for a coal condensing plant. The highest CO2
emission for electricity generation from WTs was found in the phase of materials production (60-64%
of the total emission) followed by production of WTs (32%). The phases of transportation/disassembly
and renovation/maintenance have relatively low influence, contributing 2-3% and 2-6%.
The monetary costs for electricity production were calculated to be in the range 2.9-5.4 € cents/kWh
(excluding VAT and subsidies). The lowest cost was found for 2 MW WTs and the highest cost for
renovation of 225 kW WTs.
The relative importance of different parameters influence on energy requirements and CO2 emissions
were found to be as follows: (1) service life, wind conditions/conversion efficiency and material
requirement, (2) recycling rate and, (3) transportation distance.
To utilise areas suitable for wind turbines efficiently, it is important to use the most efficient
technologies with highest possible electricity yield. A comparison of the indicators for the different
cases shows that they are pointing in different directions, which makes it possible to optimise WTs in
different ways depending on subjective values. Physical flows of energy, materials and CO2 emission
decrease per unit produced electricity when the service life is extended by renovation. On the contrary,
when the considering a monetary perspective, the costs increase when extending the service life by
renovation since labour costs is highly valued.
The Excel computer model developed in this project can be easily updated in order to evaluate
technological development and different operating conditions of WTs.