Science Centres: Energy

Tackling wind variability

One of the most critical issues for energy generation is reliability of supply. Rainfall, and hydropower generation, has a marked seasonality in New Zealand, which is overcome somewhat if water can be stored in lakes or reservoirs. The strength and consistency of wind can also be seasonal and often the highest wind speeds occur when rainfall and stream flows are lowest.

Such happy symmetry suggests some parts of the country are well suited to a mixture of wind and hydro generation.

But the wind also blows more on some days than on others. Those fluctuations pose challenges for the national grid. For example, very short term surges in wind generation might push transmission lines over their safe operating limits and cause other stability problems. If a large cluster of wind farms experiences a calm day, it takes time to gear up supplementary stations.

All this highlights the need for good information on conditions at potential wind energy sites. NIWA produces such information from suitable combinations of existing and purpose collected data. NIWA’s National Climate Database includes hourly wind speed and direction information for many sites (cliflo.niwa.co.nz). NIWA has also produced a wind speed data CD. It contains estimates of long-term monthly and annual wind speed statistics on a national 0.05° latitude/ longitude grid, in a form suitable for importing into a Geographic Information System.