Integrating renewable energy into electricity grids on a large scale creates some new technical challenges. Currently, electricity grids are balanced through supply-side management mechanisms. The intermittent nature of renewable energy production makes it difficult to adjust supply to demand, however. Energy storage is one of the tools that can be used to keep grids balanced in this kind of scenario. As part of a PhD research project conducted at CEA-Liten, a tool was developed to help grid managers determine the best energy storage solution for a given energy mix for different time horizons.
The PhD candidate conducting the research started from an analysis of seven years of intermittently-produced electricity production and consumption data, breaking it down into different time horizons from one hour to one year. The tool developed can take a description of the energy system and recommend the best storage solution to balance the grid for a given time horizon. For short-term needs, the best kind of storage turns out to be the solution with the highest yield, even if it is more expensive to purchase. For long-term needs, however, costs very rapidly go up, making more affordable storage solutions the better choice, even if they do not offer the highest yields. If intermittency is low, the ideal storage solution could be not to store energy at all and, instead, to "oversize" the production equipment—or to use a combination of several solutions if multiple time horizons need to be addressed.
In all cases, effective grid balancing involves managing nuclear, hydro, and gas power plant production, which was not factored into this study. A new study of the benefits of coupling electricity grids with heat networks and thermal heat storage systems is planned, however.