The Many Flavours and Languages of Energy Storage

 
It is becoming increasingly clear that from the global need for energy storage solutions a wide variety of practical solutions will emerge. The fast charging, energy dense battery/capacitor technologies that are ideal for an autonomous drone will be vastly different from the technology that allows us to store excess renewables from one season to the next. Equally the hydrogen that runs my Toyota Mirai (I wish!) will be a different technology to the ammonia that will power future international shipping. Despite these apparent differences there is a common thread of scientific phenomena and practical performance metrics that runs through all of these that are the foundation of what we do in Storenergy and we should all strive to develop an understanding of how they compare and contrast.
 
 In particular it is our job to communicate these commonalities and contrasts to the broader communities, so that good, well based choices can be made. For example, kWh and MWh are widely understood quantities of energy that can be used to compare energy stored.  The thermal energy storage people have gotten used to expressing performance in these terms, adding the subscript “th” for thermal to remind everyone that it is not actually electrical energy that is stored. Equally power – stored or released – is an important common property that express the rate of the fundament process and kW or MW is the obvious common unit to use.  At the moment the battery/capacitor field will use C rates, the chemical fuels field will use a product rate (mol/s) and the thermal energy field is the only one that uses kW as a primary unit – ironic since that is most familiar as an electrical unit yet there is no electrical energy involved. The point is that in understanding, comparing and communicating it is important that we in StorEnergy be ready to flip between these unit system for the benefit of the less technically trained.