- École Polytechnique Fédérale de Lausanne (EPFL) researchers in Switzerland have successfully scaled a thermally integrated photoelectrochemical device—utilizing concentrated solar irradiation—to a kW-scale pilot plant capable of co-generation of hydrogen and heat.
- A solar-to-hydrogen device-level efficiency of greater than 20% at an H2 production rate of >2.0 kW (>0.8 g min−1) is achieved.
Their study reveals a validated model-based optimization that highlights the dominant energetic losses and predicts straightforward strategies to improve the system-level efficiency of >5.5% towards the device-level efficiency. The identify solutions to the key technological challenges, control and operation strategies and discuss the future outlook of this emerging technology.
a, Technical illustration of the overall site showing key components such as the solar parabolic concentrator dish, reactor and ancillary hardware and cabinets. b, Close-up of the integrated reactor showing the assembly of the shield, homogenizer, PV and enclosure. c, A simplified process and instrumentation diagram of the system showing material and energy flows. The key input/output/intermediate energy streams are composed of the PV-generated electrical work available for electrolysis, heat output from the heat exchanger and the external work required for water pumping. W and Q stands for work and heat respectively and sensors are denoted by a circle (T = temperature sensor, P = pressure sensor, H2 = hydrogen concentration sensor). Image credit: Holmes-Gentle, I., Tembhurne, S., Suter, C. et al. Kilowatt-scale solar hydrogen production system using a concentrated integrated photoelectrochemical device. Nat Energy (2023). https://doi.org/10.1038/s41560-023-01247-2
Some of the conclusions
The design and construction of the pilot plant is outlined, highlighting how key non-trivial operational challenges have been overcome, such as the complex process control and judicious management of water flow rates to realize the synergistic effect of thermal integration. The on-sun results demonstrate advantageously fast system dynamics (startup/shutdown takes ~5 minutes) and the successful operation without degradation over various meteorological conditions and ambient temperatures (that is, operation in summer and winter). Controlling strategies were shown to be effective in dampening the solar radiation variation-induced hydrogen and heat-production dynamics. The balance of plant and auxiliary energy losses are comprehensively assessed, which highlight that this device design mitigates the typical requirement for an auxiliary heater for kW-scale electrolysers.
Link to the full paper HERE
Author: Bryan Gronenedaal