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Solar Power Storage Solution: Liquid Batteries

One of the biggest hurdles to more widespread use of solar power is that there is no simple way to store the excess energy produced, and peak energy demand doesn't always dovetail with sunny days. The latest attempt to solve this problem comes from MIT, where a team has invented an all-liquid battery that is powerful enough to store solar-generated electricity.

The problem of storing large quantities of electricity generated by eco power stations is that conventional battery tech isn't quite up to the job. Batteries have solid components that degrade, they take a significant time to charge up, they can be expensive and have a limited lifespan.

Hence the research into liquid batteries by Donald Sadoway's team of chemists at MIT. In the experimental new design, the battery is composed of three liquids mixed together—since they have different densities they form distinct layers inside the battery housing. Two of the materials act as liquid electrodes—molten magnesium and antimony—while the third liquid is an electrolyte like sodium sulfide.

When charging the battery, electrons are picked up by magnesium ions in the liquid, forming liquid metal magnesium and rising to the top of the battery. Meanwhile antimony ions lose electrons, and sink to the bottom as a layer of metal. This continues until all the metal ions are "used up" so that the battery is fully charged and there's only a narrow strip of electrolyte. When it's being discharged, the chemical process inverts and pushes electrons out until the liquids are back in their initial ionic state.

Since the battery effectively contains its own electrodes, there are no "solid" electrodes to decay like those in conventional batteries (think of the lead in a lead-acid car battery), and the large area of the electrodes and rapid movements of ions in the liquid means that the battery can take a very large charging current—ten times larger than any previous battery. And according to the team it's also cheaper than other battery tech due the simplicity of its materials and the physical design of the power cells.

Of course the battery tech isn't exclusively designed for solar power plants, and could easily find use for storing energy produced by wind and river turbines or wave farms for when it's needed versus when its produced. The MIT team is busy perfecting the design by improving the materials they use as electrodes, and envisage a practical product being on the market within five years. 

[via Technology Review]