DATE: July 21, 2018

SNIP: Energy storage (batteries and other ways of storing electricity, like pumped water, compressed air, or molten salt) has generally been hailed as a “green” technology, key to enabling more renewable energy and reducing greenhouse gas emissions.

But energy storage has a dirty secret. The way it’s typically used in the US today, it enables more fossil-fueled energy and higher carbon emissions. Emissions are higher today than they would have been if no storage had ever been deployed in the US.

This is not intrinsic to the technology, by any means. If deployed strategically, energy storage can do all the things boosters say, making the grid more flexible, unlocking renewable energy, and reducing emissions.

But only if it is deployed strategically, which it generally hasn’t been.

There are two reasons why energy storage deployed for the purpose of arbitrage increases emissions:

1) Storage increases the value of the energy sources it draws from (a source that can store some of its energy can generate more) and decreases the value of the energy sources it competes against when discharging. If the energy sources it draws from are more carbon-intensive than the energy sources it competes against, then it will have the effect of increasing the carbon intensity of the overall power mix.

2) Every bit of energy stored also represents a bit of energy lost. The “round-trip efficiency” of energy storage — the amount of energy it releases relative to the amount put in — ranges, depending on the technology, from around 40 to 90 percent.

Add those two effects together and you get a tough situation: To avoid increasing emissions, it’s not enough that the energy stored is less carbon-intensive than the energy displaced. It has to be a lot less carbon-intensive.

[Solutions discussed in the article; go read the whole thing!]