The effect of climate change on wind resources in South Africa

University of PretoriaGraduate School of Technology Management (Energy Institutional Research Theme)

Lynette Herbst

Energy Postgraduate Conference 2013

Rationale• South Atlantic and South Indian Ocean high pressure systems

have been reported to increase (Jury, 2013)

• Poleward shift of westerly wind system in Southern Hemisphere observed (Rouault et al., 2009)

• These changes may affect mean wind velocity over South Africa

• Possible implications for wind energy industry

Aim & Objective• Aim:

To determine whether energy production from wind resources will change in the 21st century

– Objective:To establish the change in annual energy production and

power density under the influence of climatic variability in two locations in South Africa.

How will a change in the mean wind velocity affect energy production in Alexander Bay and Calvinia?

Methods• Two locations (Alexander Bay and Calvinia) within

the WASA (Wind Atlas of South Africa) domain was selected for analysis in WAsP 11

• WAsP (Wind Atlas Analysis and Application Program): wind power industry standard PC-software for wind resource assessment and siting of wind farms

• Areas selected– close to proposed sites for wind farm

development

Methods contd.

• Roughness/contour map,• Observed wind climate and• Wind turbine generator files

combined in WAsP 11 to calculate wind resource

Process carried out for Alexander Bay and Calvinia with observed and ‘future’ data sets

Methods contd.• Shuttle Radar Topography Mission (SRTM) elevation data

employed in generation of WAsP compatible contour maps

Methods contd.

• ‘Roughness’ refers to land cover/friction wind encounters as it moves over surface

• Google Earth image used as background image to map roughness

• Areas of different roughness demarcated, and roughness lengths (z0 (m)) specified

Methods contd.• Monthly observed climate data downloaded from

WASA website for Alexander Bay and Calvinia• MS Excel files concatenated to create single files

containing whole year data• Future data created by assuming 10% increase in

10m mean wind velocity in 2081-2100 based on work of McInnes et al. (2011)

• 10m mean wind velocities were converted to 60m winds with Hellman’s exponential law (Bañuelos-Ruedas, 2011):

Results: Calvinia

2010-10 to 2012-09 2081-2100

• Tested for significant difference with Mann-Whitney U test at a 95% confidence level

• U > critical value (42)• Therefore, no significant difference in annual energy

production and power density between current and future scenarios

Results: Alexander Bay

2010-10 to 2012-09 2081-2100

• U > critical value (42)• Therefore, no significant difference in annual energy

production and power density between current and future scenarios