While creating the Nuclear Rebalance mod (to be released soon(tm)) it became apparent that the same barriers to nuclear power adoption (well, some of them) that exist in real life also exist in factorio. Namely, Nuclear Energy is excellent for base load power, but is not ideal for peak power draw. To deal with this, accumulators exist in the base game. However, it is well known that steam-storage is hugely more energy dense than accumulators. In Factorio, steam storage incurs use of the fluid system, which is a hard UPS hit.
All late-game mega bases use Solar Power because it has a single UPS impact for both production and storage. However, to generate the 60 or so GW of energy needed to run a 10k SPM megabase requires a solar panel array that is normally as large, if not larger, than the base itself. Much of that space is taken up by the accumulators needed to store power overnight.
The purpose of this mod is to create higher tiers of energy storage. In factorio, accumulators are based on Lead-Acid battery technology and have the energy density to match. Well done factorio devs! However, better energy stores exist. NiMH batteries would have roughly 3x the energy density of Lead-acid, and lithium-ion batteries would have just shy of 2x the density of NiMH. Flywheel storage is the pinnacle of energy storage, allowing for twice the energy density of li-ion. In all cases, I am quoting density as Megajoules per unit volume as my metric.
Only technologies which exist in production (non-lab settings) today (2019) and which have an energy density greater than that of lead-acid batteries were considered. That is why pumped storage was not considered, it's energy density is quite low.
Once newer and better battery technology is unlocked, there is no reason to continue to use the older technology. Thus, new satellite blueprints become available which use the newer battery technologies. At first, the new satellite blueprints simply swap the old accumulators for the new battery tech, but eventually the satellites become upgraded to have more sensors and more energy generation, enabling deep-space probes to be launched. This, in turn, allows a single satellite to bring pack more science packs when launched. Thus, upgrading battery technology not only
simplifies the production chain, but also confers a benefit to space-science research.
Check out my other UPS saving / Megabase mods: