Space, Time, and Size Dependencies of Greenhouse Gas Payback Times of Wind Turbines in Northwestern Europe

Abstract

The net greenhouse gas benefits of wind turbines compared to their fossil energy counterparts depend on location-specific wind climatology and the turbines’ technological characteristics. Assessing the environmental impact of individual wind parks requires a universal but location-dependent method. Here, the greenhouse gas payback time for 4161 wind turbine locations in northwestern Europe was determined as a function of (i) turbine size and (ii) spatial and temporal variability in wind speed. A high-resolution wind atlas (hourly wind speed data between 1979 and 2013 on a 2.5 by 2.5 km grid) was combined with a regression model predicting the wind turbines’ life cycle greenhouse gas emissions from turbine size. The greenhouse gas payback time of wind turbines in northwestern Europe varied between 1.8 and 22.5 months, averaging 5.3 months. The spatiotemporal variability in wind climatology has a particularly large influence on the payback time, while the variability in turbine size is of lesser importance. Applying lower-resolution wind speed data (daily on a 30 by 30 km grid) approximated the high-resolution results. These findings imply that forecasting location-specific greenhouse gas payback times of wind turbines globally is well within reach with the availability of a high-resolution wind climatology in combination with technological information.

Greenhouse Gas Savings Potential under Repowering of Onshore Wind Turbines and Climate Change: A Case Study from Germany

“…Depending on WTT, median GPBTWT varies from 4.9 (interquartile range of 4.1 to 6.7 months) to 8.0 months (interquartile range of 6.7 to 10.8 months), with WTT4 exhibiting the lowest median values of 4.9 months under RCP8.5 and 5.0 months under RCP4.5. The presented GPBT values are in accordance with the findings from an earlier study [17], which calculated a GPBT of 1.8 to 22.5 months (mean: 5.3 months) for wind turbines in northwestern Europe. Since the differences in climate change scenario-related GPBT WT are extremely small, they are not considered to affect the repowering strategy in this study.…”

“…Based on AEY WT of the repowerable wind turbines, GPBT WT was calculated. It quantifies the time required until GHG savings of a wind turbine exceed GHG emissions originating from the wind turbine's life cycle [17]:…”

“…It was calculated for WTT1-WTT4. By applying the regression model reported in a previous study [17], GGA WTT was determined as a function of D and h hub :…”

“…The CO 2,eq emissions of wind turbines during their service life can be quantified by a life cycle assessment (LCA). LCA is used to evaluate the environmental impacts of a technology or service considering all resources and energy required during all stages of wind turbines' life cycles [1,17].…”

“…A certain amount of time is required until the GHG savings of a wind turbine replacing conventional power plants exceeds GHG emissions originating from the wind turbine itself. This time is called greenhouse gas payback time (GPBT) [17,27]. Only after this time, a wind turbine contributes to net GHG emission savings.…”