While some countries like Germany have take giant steps in the development of cost-efficient solar and other renewable energy sources, that virtually scrap the need for the so-called "conventional" sources like oil, gas or nukes, a problem remains: how to store energy in a reliable and efficient way to be released in a controlled way when the renewable sources are temporarily not available (night for solar, windless days for eolic, etc.)
Research is in progress but I will mention here a few examples on how this is advancing.
A year ago, a team of the USC Dornsife College of Letters, Arts and Sciences, led by Sri Narayan, developed an advanced battery based on iron rusting. This method has the advantage of being relatively well known (has been around from the 1970s) but previously faced the challenge of about half its capacity being robbed by hydrolysis. This research managed to reduce such loss to just 4%, what is a great advance, thanks to the use of a small amount of bismuth sulfide.
More recently research has been focused on membraneless batteries. In April team of U.S. Department of Energy's SLAC National Accelerator Laboratory and Stanford University researchers announced a lithium polysulfide battery, that overcomes material limitations of previous similar designs (lithium and sulfur are relatively inexpensive) and is easily scalable for large scale energy management needs.
This week MIT researchers offered another new membraneless alternative that beats lithium capacities by "an order of magnitude". The model, based on bromine and hydrogen reactions overcomes the limitations of these materials, whose composite hydrobromic acid tends to eat the battery membranes, by totally suppressing them. The development is being presented as "a quantum leap" in energy storage systems, although other researchers are more cautious.