December's calendar photograph is a battery of five solar cells that also stores electricity in series. The cells were invented and developed at the Weizmann Institute in the late 1970s. These not only converted sunlight into electricity, but also could store some of that energy using a battery-type setup with electrodes in a chemical solution, so that they could provide electricity day and night.
The idea of efficiently storing solar energy has taken more than one twist and turn since then - various forms of artificial photosynthesis, for example. Interestingly enough, one of the latest versions to be developed at the Institute also involves a form of electrolysis, though this one is quite hot. The proposal is to use an electric current (produced by solar cells or wind) running through 900°C molten salt to recycle CO2 fed into it (say, from a smokestack), splitting it into CO and O2. The CO could then be easily shipped, burned as is, or converted to liquid fuel such as methanol. Because the electrodes are composed of off-the-shelf titanium, rather than platinum or other rare metals, the new method just might have the advantage of being economically feasible, as well.