Standardized Rectilinear Units of Power (SRUPs)

Ten years ago, my daughter (now a physics PhD candidate) and I were discussing on a road trip the idea of Standardized Rectilinear Units of Power (SRUPs) as mobile and stationary power sources. The idea was that large power sources should be like "C" and "D" dry-cell batteries and be of a standard size and power output. We had discussed the idea that these could be like traditional rechargeable batteries, but that other standard inputs and outputs could also be supported. The key thing was the standard size and the standard I/O. Other possible inputs could be hydrogen or LNG or even gasoline. I had challenged her to do some calculations of the energy density that would be required to make these economical. For example, if a truck was moving a load of such SRUPs and was also using them as its energy source, what would be the energy transportation bandwidth of different currently possible SRUP implementations. The proposition that I had made at the time was that by defining such industry standards, we would see the same benefits as had occurred with standard dry-cell batteries and with the early PC clones too - competition and volume. As I've recently re-discovered Hackernews, I thought I'd share this idea and see what discussions came of it.