The Catch-22 of energy storage

In particular, we can’t use batteries or chemical energy storage systems, as they would lead to much worse figures than those presented by Weißbach et al.  Hydroelectricity is the only renewable power source that is unambiguously viable.  However, hydroelectric capacity is not readily scaled up as it is restricted by suitable geography, a constraint that also applies to pumped hydro storage.

This particular study does not stand alone.  Closer to home, Springer have just published a monograph, Energy in Australia,³ which contains an extended discussion of energy systems with a particular focus on EROEI analysis, and draws similar conclusions to Weißbach.  Another study by a group at Stanford² is more optimistic, ruling out storage for most forms of solar, but suggesting it is viable for wind.  However, this viability is judged only on achieving an energy surplus (EROEI>1), not sustaining society (EROEI~7), and excludes the round trip energy losses in storage, finite cycle life, and the energetic cost of replacement of storage.  Were these included, wind would certainly fall below the sustainability threshold.

It’s important to understand the nature of this EROEI limit.  This is not a question of inadequate storage capacity – we can’t just buy or make more storage to make it work.  It’s not a question of energy losses during charge and discharge, or the number of cycles a battery can deliver.  We can’t look to new materials or technological advances, because the limits at the leading edge are those of earthmoving and civil engineering.  The problem can’t be addressed through market support mechanisms, carbon pricing, or cost reductions.  This is a fundamental energetic limit that will likely only shift if we find less materially intensive methods for dam construction.

This is not to say wind and solar have no role to play.  They can expand within a fossil fuel system, reducing overall emissions.  But without storage the amount we can integrate in the grid is greatly limited by the stochastically variable output.  We could, perhaps, build out a generation of solar and wind and storage at high penetration.  But we would be doing so on an endowment of fossil fuel net energy, which is not sustainable.  Without storage, we could smooth out variability by building redundant generator capacity over large distances.  But the additional infrastructure also forces the EROEI down to unviable levels.  The best way to think about wind and solar is that they can reduce the emissions of fossil fuels, but they cannot eliminate them.  They offer mitigation, but not replacement.

Nor is this to say there is no value in energy storage.  Battery systems in electric vehicles clearly offer potential to reduce dependency on, and emissions from, oil (provided the energy is sourced from clean power).  Rooftop solar power combined with four hours of battery storage can usefully timeshift peak electricity demand,³ reducing the need for peaking power plants and grid expansion.  And battery technology advances make possible many of our recently indispensable consumer electronics.  But what storage can’t do is enable significant replacement of fossil fuels by renewable energy.

If we want to cut emissions and replace fossil fuels, it can be done, and the solution is to be found in the upper right of the figure.  France and Ontario, two modern, advanced societies, have all but eliminated fossil fuels from their electricity grids, which they have built from the high EROEI sources of hydroelectricity and nuclear power.  Ontario in particular recently burnt its last tonne of coal, and each jurisdiction uses just a few percent of gas fired power.  This is a proven path to a decarbonized electricity grid.

But the idea that advances in energy storage will enable renewable energy is a chimera – the Catch-22 is that in overcoming intermittency by adding storage, the net energy is reduced below the level required to sustain our present civilization.