The small wind power market features heterogeneous technologies, which promise solutions for different purposes like the supply of off-grid areas or converting buildings to electricity generators. Experience shows that especially the urban use of small wind turbines (SWTs) needs to be assessed carefully. Even though the turbines are already on the market, the following determining question often stays unaddressed: Is the wind turbine able to meet its intended outcome of environmental friendly, renewable energy production? Furthermore, as a precursory requirement: Considering its whole life cycle, is the turbine producing more energy than it consumes?

Although these requirements seem fundamental, studies show that there are many SWTs on the market that do not fulfil these requirements. For instance, an energy payback time of 160.9 years was calculated for a horizontal axis SWT, whereas for big wind turbines the payback time amounts to less than one year. Another study calculated a payback time of 6.5 years for a 250 Watt turbine. Even though, this value is feasible within the life span of a wind turbine, normally assumed to be 15 to 20 years, the value is still very high compared to other technologies such as big wind turbines or photovoltaics.

Due to the high variety in published energy payback time for SWT as well as the heterogeneity of technologies, we conducted Life Cycle Assessments (LCA) of two SWTs. The LCAs were performed according to ISO 414040 covering goal and scope definition, inventory assessment, impact assessment and interpretation. The software open LCA and the EcoInvent database were used. Within the impact assessment the categories total energy demand and global warming potential (GWP100) were used. Furthermore, the energy payback time was calculated. A cradle to cradle approach was used, hence the end of life treatment as well as the transport are included. A horizontal axis SWT with 5 kW nominal capacity as well as a horizontal axis SWT with 0,5 kW nominal capacity were examined. Both turbines showed to produce more energy than they consume over their lifetime when installed at sites with high wind speeds. In contrast, in urban areas, the wind conditions are unsteady and often at very low wind speeds. The 0,5 kW SWT is installed on a suburban site close to Vienna and data for power production, wind speed and direction as well as vibrations are collected. At an urban site in Vienna, currently wind data are collected and will be used to calculate the potential power production, expected to show essentially lower values than the production rate on the suburban site.

The life cycle results will be integrated in a holistic technology assessment, considering ecological and safety issues as well as economic feasibility. First results show that SWTs may be effective at windy sites in suburban areas, but seem to face serious problems in urban use.