They are a key element of grid modernization; mass storage for variable generation that's a byproduct of capital investments already being made for transportation.
...from 2010 to 2012, a two-year period encompassing the March, 2011 Fukushima catastrophe and Germanys subsequent decision to turn off 29% of its nuclear power production (reducing reactor output from 140.6 terrawatt-hours in 2010 to 99.5 TWh in 2012), Germany actually held constant its use of fossil fuels to make electricity.
How did German society make up for the 41.1 TWh drop in reactors electricity generation? Numerically, it was simple:
German solar-photovoltaic generation grew from 11.7 TWh to 28.0 TWh (a rise of 16.3 TWh).
Wind generation grew from 37.8 TWh to 46.0 TWh (a rise of 8.2 TWh).
Total consumption of electricity fell by 16.4 TWh (from 610.9 TWh to 594.5 TWh), despite GDP growth.
(Figures are based on data from Bundesministerium für Wirtschaft und Technologie, Statistisches Bundesamt, Arbeitsgruppe Erneuerbare Energien-Statistik (AGEE-Stat).)
Why Official Nuke Plant Cost Estimates Are Like Campaign Promises
11/21/2013 by Charles Komanoff
http://www.carbontax.org/blogarchives/2013/11/21/why-official-nuke-plant-cost-estimates-are-like-campaign-promises/