This 'Hourglass' Liquid Battery Runs on Gravity

Scientists at MIT have designed an ingenious new concept for a battery that operates on the same fundamental principal as an hourglass—it relies on gravity to generate energy. They described the device in a recent paper for Energy and Environmental Science. The fundamental concept of a battery is quite simple. There is a positive and negative terminal; electrons are produced by chemical reactions inside the battery, and collect on the negative terminal because they are negatively charged.
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