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Hydrogen or batteries for grid-scale storage?

A recent GCEP analysis finds that hydrogen is just as energy-efficient as batteries when storing wind power, but significantly less efficient than batteries when storing solar photovoltaic power. For this study, GCEP researchers evaluated the total life-cycle energy efficiency of hydrogen and batteries, including the energy costs of manufacturing the storage system as well as the round-trip efficiency of energy storage.

Photo: Michael Milligan/NREL
GCEP researchers examine whether hydrogen or batteries were more efficient when storing wind power.
Matt Pellow Sally Benson and Charlie Barnhart
GCEP Scientists Matthew Pellow (left), Sally Benson and Charlie Barnhart

Electrical energy can be stored by using it to split water into hydrogen and oxygen, and then capturing and storing the hydrogen. Later, the hydrogen can be provided to fuel cell to generate electricity. Although the round-trip efficiency of this process that is less than half that of batteries, the GCEP analysis finds that less energy is required to manufacture a hydrogen system than a battery. The hydrogen system's lower manufacturing energy requirement offsets its larger efficiency losses as compared to batteries.

As a result, hydrogen is as effective as the most efficient batteries when storing wind power -- and considerably better than lower cost lead-acid batteries -- when considering both manufacturing and round-trip efficiency. The overall energy return on investment (EROI) of a storage-equipped wind farm using hydrogen storage would be significantly higher than one that uses lead-acid batteries (widely deployed for grid storage), and similar to lithium-ion batteries.

However, hydrogen is less effective than even the least efficient batteries for storing solar power.  Its low round-trip efficiency significantly degrades the overall energy performance of the facility. In this application, battery technologies with higher round-trip efficiencies, such as lithium-ion batteries, are much more attractive. 

GCEP's analysis of energy storage in hydrogen was published in Energy & Environmental Science, and was led by Matthew Pellow, a postdoctoral researcher in energy systems analysis at GCEP; and by Sally Benson, the director of GCEP. Charlie Barnhart (Western Washington University) and Christopher Emmott (Imperial College London) also contributed to this work.

December 11, 2015

GCEP Net Energy Analysis



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