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Life-cycle net energy assessment of large-scale hydrogen production via photoelectrochemical water splitting

Scientific Achievement
This article reports the first prospective life-cycle net energy assessment of a utility-scale photoelectrochemical (PEC) hydrogen production facility including balance-of-system components.

Significance and Impact
Results show that large-scale H2 production using PEC technology can be energy-positive; however, PEC devices must meet certain efficiency and durability criteria. This suggests that a strong program of research into improved materials and methods to process the materials will have a high impact on the feasibility of this technology.

Summary
A research group at the Joint Center for Artificial Photosynthesis (JCAP), led by Roger Sathre and Jeffrey Greenblatt, conducted a prospective life-cycle net energy assessment of a hypothetical large- scale PEC hydrogen production facility with energy output equivalent to 1 GW continuous annual average (1 GW HHV = 610 metric tons of H2 per day). The work determined essential mass and energy flows based on fundamental principles, and used heuristic methods to conduct a preliminary engineering design of the facility. Then, a parametric model was developed and applied to describe system-wide energy flows associated with the production, utilization, and decommissioning of the facility. Based on these flows, life-cycle net energy metrics for the facility could be calculated. Sathre and colleagues found that under base-case conditions the energy payback time was 8.1 years, the energy return on energy invested (EROEI) was 1.7, and the life-cycle primary energy balance over the 40-year projected service life of the facility was +500 PJ. The most important model parameters affecting the net energy metrics were the solar-to-hydrogen (STH) conversion efficiency and the life span of the PEC cells. Parameters associated with the balance of systems, including construction and operation of the liquid and gas handling infrastructure, play a much smaller role.

R. Sathre, C. Scown, W. Morrow, J. Stevens, I. Sharp, J. Ager, K. Walczak, F. Houle, and J. Greenblatt, Life-cycle net energy assessment of large-scale hydrogen production via photoelectrochemical water splitting, Energy Environ. Sci. Advance Article (2014).