The race to find new ways to store electricity has some new and surprising entrants. Two new arrivals have the advantage of using extremely common elements, making them potentially very cheap to build. Neither is likely to power your phone or laptop, and they probably won't be suited to electric cars, but they might store solar or wind energy for still nights and cloudy days.

Oregon State University has announced the first hydronium battery, made from H 3 O+ or water with a proton added. Neither is in short supply.

To build the battery, Dr Xiulei Ji created electrodes from the crystalline solid perylenetetracarboxylic dianhydridem (PTCDA), which despite its intimidating name is formed from just carbon, hydrogen, and oxygen. The electrolyte is sulfuric acid, with a concentration well below that used for existing car batteries.

In Angewandte Chemie International Edition, Wang reports that hydronium ions can be stored in PTCDA in a reversible fashion, offering the chance to charge them up when power is plentiful, to be released when it is required.

"Organic solids are not typically contemplated as crystalline electrode materials, but many are very crystalline, arranged in a very ordered structure," Ji said in a statement. "This PTCDA material has a lot of internal space between its molecule constituents so it provides an opportunity for storing big ions and good capacity."

Silicon makes up 28 percent of the Earth's crust, so it's also abundantly available. The company 1414 Degrees has spent years trying to turn work initially done by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) into an economically feasible method for storing energy in the form of molten silicon, and recently announced the first tests of a prototype.

Energy is used to melt silicon, which, as the company's name suggests, occurs at 1,414ºC (2,577ºF). When the silicon is allowed to cool the energy drives a turbine to turn it back into electricity. Although this process can theoretically be used for a wide variety of materials, silicon has the advantage of holding heat far longer than most alternatives, and providing more stable power as it cools.

Extracting the energy efficiently is the challenge; much is inevitably lost as waste heat. Although 1414 puts this to use for space and water heating, the commercial value is far lower than for electricity.

On its first run the prototype managed to recover 80 percent of the stored energy as a whole, but just 31 percent as electricity. Nevertheless, 1414 Degrees say they are ready to build 10 and 100 Mega Watt hour units to fill the gap between small to medium systems like the Tesla Powerwall and large dams with pumping systems. They hope that their system's much lower cost will allow it to compete with more electrically efficient lithium-ion batteries.