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SAIDI

German grid keeps getting more reliable

So much for renewable energy destabilizing the German grid: Yesterday, Germany’s Network Agency published the SAIDI figure for 2014, showing that the number of downtime minutes fell to an all-time low.

It’s getting hard to count the minutes of power outages in Germany. And it’s getting hard to improve the figure.

As recently as 2006, Germany had 21.53 minutes of power outages, as counted in the SAIDI metric (report in German). That number has now fallen to 12.28 minutes as of last year, according to the official statistics from the Network Agency (website in German). Since 2009, the figure has hovered around 15 minutes, so this decrease of around 2.5 minutes represents a considerable improvement.

To get an idea of how good the German grid is, we need an international comparison.

SAIDI
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EnergyTransition.de

Above, we see that Germany and Denmark have the most reliable grids by far in Europe. The Danes also have around 40 percent wind power, whereas the Germans have roughly 17 percent wind and solar combined. The share of these two energy sources is relevant because they react to the weather, not to grid events; they are not dispatchable and are therefore commonly held to be a danger to grid reliability, at least among critics of the Energiewende.

Italy also has roughly the same amount of wind and PV as Germany does, and its grid performance has improved since 2006. Likewise, wind and solar taken together are now the largest source of electricity in Spain, and that country’s SAIDI figure improved tremendously (but note that the data are only available for 2006-2011, PDF).

Correlation is not causation, however. Just because these countries have fewer minutes of downtime does not mean that solar + wind are the reason. Rather, as a report from the CEER explained in 2013, other improvements have been made to the grid, specifically the use of underground cables rather than overhead lines.

While solar + wind are therefore not the main cause for lower downtime minutes, clearly high levels of fluctuating renewable energy are possible with extremely low SAIDI numbers.

Note that SAIDI does not include natural disasters, so storms that cause blackouts are not included in the figure. Likewise, the outage must last at least three minutes, a criterion for which the metric has been criticized; after all, less than three minutes of downtime can be quite disruptive in the production sector.

(Craig Morris / @PPchef)