Storage batteries in photovoltaic–electrochemical device for solar hydrogen production

Batteries to Keep Solar‐Driven Water Splitting Running at Night: Performance of a Directly Coupled System

“…As it has been predicted in our earlier work, [19] the battery can facilitate improvement of STH efficiency in addition to the stabilization function. This gain in STH efficiency is confirmed experimentally with high-efficiency components, appropriate voltage matching, and appropriate power matching of the components.…”

“…It has been shown theoretically and experimentally that a battery connected in parallel to the EC cell can smoothen out the PV power fluctuations, facilitate power coupling, and even improve STH efficiency. The latter point shown theoretically [19] is of particular interest but is yet to be shown experimentally. Analysis of the PEB system operation shows that the distribution DOI: 10.1002/solr.202100916 Direct solar-powered hydrogen generation (so-called "green" hydrogen) is promising as a renewable fuel that can be generated anywhere there is sunshine and water.…”

“…Running the electrolyzer on the battery-stored energy in the night, all charge collected during illumination (Q B ) can be utilized to split water if the battery has no charge losses, and the discharge current, I Bd ,is sufficiently high to release all the charge before the next cycle. [19] The first condition is achieved by very high Faradaic (Coulombic) efficiencies in modern batteries exceeding 99% per cycle. [21,22] This is especially so for low state of charge utilization and relatively low C-rates (battery charge/discharge rates relative to 1 h for full charge) for charge and discharge below 1 C. The second condition is fulfilled when the product I Bd  t d equals or exceeds Q B after accounting for storage and transmission losses.…”

“…Equation ( 5) also can be simplified for the case of the rectangular irradiance profile to a simple sum of currents to the electrolyzer and battery during the illumination phase. [19] η Ã STH PEB ð%Þ ¼…”

“…[17] One straightforward measure to stabilize operating conditions of the electrolyzer is to include battery storage into the PVÀEC combination, turning it into the PVÀECÀBattery (PEB) system, as demonstrated at the residential system level. [18] In our previous work, [19] we have explored how storage can be included in a directly connected PVÀEC system. We have shown the feasibility of unaided operation of a cell-to-cell, directly connected PEB system.…”