A paper by scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) and colleagues examining the net energy of a hydrogen-generating technology, which is still in development in the lab, is one of last week's "Hot Articles" in the refereed journal Energy and Environmental Science. Net energy is the amount of hydrogen produced minus the energy required to manufacture the technology.

The paper, by scientists in the Environmental Energy Technologies (EETD), and the Joint Center for Artificial Photosynthesis, evaluates whether solar-driven photoelectrochemical (PEC) generation of hydrogen would produce more energy over its lifetime than is required to manufacture the technology-a fundamental requirement for the technology.

Depending on the assumptions about efficiency and lifetime, a PEC cell can indeed produce more energy than is consumed during manufacture. PEC technology is still under development in the laboratory.

"Knowledge about the net energy balance of a PEC device can help guide the technology to success by identifying components and materials that use lower energies to manufacture, and continue to produce hydrogen for a long time, so that the net energy generation over its lifetime is as large as possible," says Greenblatt.

The authors of the study are Pei Zhai (formerly of EETD), Sophia Haussener, Joint Center for Artificial Photosynthesis and Laboratory of Renewable Energy Science and Engineering, Ecole Polytechnique Federale de Lausanne, Switzerland, Joel Ager (Joint Center for Artificial Photosynthesis), Roger Sathre, (EETD), Karl Walczak (Joint Center for Artificial Photosynthesis), Jeffery Greenblatt (EETD) and Thomas McKone (EETD).

"Net primary energy balance of a solar-driven photoelectrochemical water-splitting device," Energy and Environmental Science. DOI: 10.1039/c3ee40880a

This research was sponsored by Laboratory Directed Research and Development funding at the Lawrence Berkeley National Laboratory, and by the Joint Center for Artificial Photosynthesis.