We have seen the future, and the future is stored energy — Part 2

How Tesla’s Batteries Will Power Your Home

FINDING SOURCES OF energy isn’t actually difficult. It comes from wind, from water, from the sun, from the geothermal forces in the heart of the planet itself. The trick is holding onto that energy and moving it around, storing it and then delivering it where people need it. That’s why carbon-based sources like oil are so great. They’re transportable and shelf-stable.

So how will people store and transport energy from renewable sources? Batteries.

Last night, Elon Musk outlined his plan to bring a Tesla battery to homes and offices, generally as an adjunct to solar panels—green energy, on demand. The billionaire CEO unveiled the Powerwall, a battery in 7 or 10 kilowatt-hour sizes. For bigger operations, there’s also a 100 kWh unit called the Powerpack. And the Powerwall doesn’t just let you bank late afternoon solar for late night bingeing; you can also pull power from the grid during off-peak hours. All this for $3,500.

Battery technology is already pretty robust, but it’s never been able to hit such a reasonable price point. “The challenge is to develop a storage system that is economical, with a reasonable payback period for the customer,” says Ping Liu, program director at ARPA-E, the government agency charged with developing new sources of energy. The payback period is your savings over time, by weaning your home off Big Grid.

Batteries don’t store electricity; they store energy. They do this by keeping two different materials—a positively charged cathode and a negatively charged anode—separated by some sort of non-conducting material, categorically called electrolytes. The electrolyte keeps the cathode and anode from touching, but lets molecules pass through. When the terminals (the ends labeled with + and – signs) are connected to an electrical circuit, a chemical reaction inside the battery forces molecules from the cathode to pass through the electrocyte and into the anode. The anode responds by firing off electrons through the negative terminal, and anything wired into the circuit gets power.

The battery stops making power when there are no more volatile molecules to pass between the two materials. This is why the AA’s in your old Sony Discman would go dead. The materials in rechargeable batteries however, can pass volatile molecules back from the anode to the cathode with a little external charge. This restores the imbalance for another round.

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