A 25 cm² Solar Redox Flow Cell: Facing the Engineering Challenges of Upscaling

Abstract

The solar redox flow cell (SRFC) is an emerging technology that uses semiconductors to photocharge redox pairs, storing solar energy in electrochemical fuels and heat. Despite being in its infancy, significant efforts have been made in the development of high‐efficient materials and in understanding the fundamental processes. However, little attention has been given to device architecture and scalability, which may prove equally important in bringing this technology closer to commercialization. This work is the first attempt at upscaling SRFCs, proposing an innovative 25 cm2 photoactive‐area device: the SolarFlow25 cell. A computational fluid dynamics model is developed to implement design key features aiming at: maximizing light absorption by the semiconductor, ensuring effective diffusion and convection of redox species, and guaranteeing minimal electronic and ionic transport resistances. After being connected to a redox flow cell (RFC), the combined SRFC/RFC device is used to photocharge–discharge a ferrocyanide/anthraquinone (2,7‐AQDS) chemistry continuously. A nanostructured hematite (α‐Fe2O3) photoelectrode combined in series with a dye‐sensitized solar cell (DSSC) produces an unbiased photocurrent of ≈40 mA. The solar‐to‐output‐electricity‐efficiency remains stable at ≈0.44%, fourfold higher than any other reported hematite‐driven SRFC. The guidelines provided here are expected to help design and upscale future SRFC devices, making solar energy accessible in decentralized locations.

Photovoltage memory effect in a portable Faradaic junction solar rechargeable device

“…For this purpose, substrate ohmic loss, ionic transport resistance, parasitic adsorption of Faradaic materials should be decreased. Some possible methods, such as conductive silver frame as collector 11 , further reducing the distance between the two electrodes and introducing back-side illuminated photoelectrodes 45 , can be used. Moreover, it is also significant to develop large-scale deposition methods for Faradaic materials on the semiconductors and FTO substates 11 .…”

Advances and Challenges in Photoelectrochemical Redox Batteries for Solar Energy Conversion and Storage

“…[161] Regarding the development of the scaleup of PRBs, various systems reported in the literature were also proposed from lab-scale proofs-of-concept to mature and scalable PRB technology. [37a,162] A typical case was proposed by Mendes et al, [163] where they first attempted to upscale PRBs and proposed a photoelectrode with an active area of 25 cm 2 , as shown in Figure 14a. By using the nanostructured hematite (α-Fe 2 O 3 ) as the photocatalyst, ferrocyanide (Fe(CN) 6 4− / Fe(CN) 6 3− )-anthraquinone (AQDSNa 2 /AQDS) as the redox couples, the unbiased photocurrent density can reach about 40 mA (1.36 mA cm −2 ) with the help of a dye-sensitized solar cell that is in series with the photoelectrode.…”

“…In this direction, developing a stable polymer Reproduced with permission. [163] Copyright 2022, Wiley.…”

“…Figure 14. a) Scheme of the cell component and front-side view of the assembled device, b) cycling behavior and photocurrent,c) efficiencies for the 10 photocharge-discharge cycles. Reproduced with permission [163]. Copyright 2022, Wiley.…”

Ultralow Temperature Glass Frit Encapsulation for Stable Dye-Sensitized Solar Cells

“…Dye-sensitized solar cells (DSSCs) are a photovoltaic (PV) technology that merges simple and cheap fabrication processes with the use of earth-abundant materials in nice aesthetic devices that display moderate power conversion efficiency (PCE); , a PCE record of 13.0% under standard 1 sun illumination was recently certified . Due to their appealing aesthetic, the possibility of implementing them in flexible and semitransparent modules and the high PCE under dim and diffused light, DSSCs have been traditionally considered appealing as outdoor building- and agriculture-integrated PVs. , DSSCs are considered as a promising technology for integration with energy storage systems, solar-chargeable redox flow batteries, , and wearable electronics to name a few emerging applications. Recent advancements turned DSSCs into one of the most efficient, rapidly developing, and attractive indoor PVs , to address the need for cordless energy for low-power devices such as the Internet of Things (IoT), wireless sensor nodes, and controllers, , since DSSCs perform exceptionally well under artificial indoor light, displaying amazing PCE of ca.…”