The pages in the Wind Intermittency section, explain the problem and present conclusive data explaining the nature of the problem and the magnitude. The conclusions can be summarized as:
- Wind fluctuations in a single country span the range from 5% to 80% of installed capacity because of weather coherence over large areas.
- Similar fluctuations exist in adjacent countries on the 1- 5 day timescale.
- Storage of sufficient power to cover 3 days of wind power off is not possible with existing technology, at least in countries with large wind capacity and low hydro capacity.
- To compensate for these fluctuation, fossil fuel capacity of magnitude roughly equal to the wind power capacity is needed.
- Import/exports can only help the situation in a particular country when adjacent countries have large hydro capacity or fossil fuel capacity available to provide the compensation.
Another limiting factor for wind power is the inflexibility to cover demand variations. The magnitude of these variations are presented in the pages of the Demand Variations section where its is shown that:
- Demand variations between summer nights and winter days are up to a factor 2 in some countries.
- In countries with little hydro generation capacity these variations are compensated for essential with variations of fossil fuel generation.
The evaluation of current carbon dioxide emissions show:
- Countries with > 20% wind+solar generation have typically 200-400 gCO2 equivalent/KWh.
- Countries with > 50% nuclear+hydro generation have < 200 gCO2 equivalent/KWh.