German grid reaches record reliability in 2011
On Monday, Germany's Network Agency announced that the German grid only had a downtime of 15.31 minutes, even lower than the already impressive 17.44 minutes of downtime during the period from 2006 the 2010.
Last spring, when the German government resolved to shut down eight of the country's 17 nuclear plants within a week, there was concern about whether the country's grid would remain reliable. Not only did the country avoid a major blackout during the winter, but its availability actually increased over the average going back to 2006, when reporting began.
In 2006, the Network Agency began calculating the SAIDI value (system average interruption duration index), which can be seen on this website in German. The index does not include planned interruptions or downtime due to natural disasters; rather, it only includes unplanned interruptions lasting more than three minutes.
Germany's performance can only be properly appreciated in the context of other countries. As the chart to the left shows, Germany has consistently been the leader among reporting EU member states since it began reporting in 2006. The differences are also not slight, such as 15 minutes versus 20 minutes. Instead, the number of minutes of grid interruptions in other countries (such as France, which had 62 minutes of SAIDI downtime in 2007) is often several times the German level.
Importantly for international readers, the Network Agency reports specific figures for the number of grid operators in Germany: 864 grid operators reported 206,673 grid interruptions on 928 separate grids. These figures clearly show that the German grid is as splintered as those in other countries and is not a monolithic state-driven entity.
Germany clearly demonstrates that a very high level of grid reliability is feasible with a high penetration level of intermittent wind and solar power. Indeed, Denmark, which has an even greater share of wind power in Germany, also has a similarly reliable grid, and as the chart shows above grid reliability in Spain has actually improved dramatically over the past few years even as it ramped up its wind and solar power.
By way of comparison, the United States had a SAIDI of 240 in 2007, which would put the country at the back of the ranking in the chart. It has been estimated, for instance, that grid downtime in the United States costs the US economy around 150 billion dollars a year, equivalent to four cents per kilowatt-hour (see this PDF).