A 25.1% Efficient Stand‐Alone Solar Chloralkali Generator Employing a Microtracking Solar Concentrator

Abstract

or where extending the power connection lines would not be economically justifiable. Besides its direct use for lighting, appliances, etc., stand-alone photovoltaic electricity can be utilized to generate a valuable chemical feedstock via electrochemical processes. They are the natural entry point for PV integration, as these processes specifically require direct electricity to operate. Their scalability, coupled with the possibility to modulate the load and possibly operate on-demand, facilitates the implementation of timevarying renewable energy sources. [2] Most of the research efforts have been recently devoted to the investigation of solar hydrogen devices, following two distinguished paths: photoelectrochemical (PEC) or photo voltaic-electrolysis (PV-E) devices. The latter approach appears to be more technologically mature for shortterm implementation and have been demonstrated using multijunction solar cells [3] and inexpensive silicon cells.[4] While most efforts in the past decades have focus on the development of cost-effective hydrogen-generators, little attention has been dedicated to the development of stand-alone solar-reactors for the electrochemical generation of different commodities, e.g., halides that can already count on an established industrial practice. [5] Chlorine is used as a feedstock for the manufacture of numerous products in more than 50% of all the industrial processes. [6] The main route to produce chlorine is the chloralkali process, one of the largest electrochemical operations in industry; it accounts for a yearly energy consumption of 150 TWh, 1% of the global overall and 2% of the US electrical production. [7] Molecular hydrogen and hydroxide ions (which can later be extracted as sodium hydroxide) are generated in the cathodic reaction. The predominant chloralkali electrochemical reactors implement membranes [8] that separate a De Nora DSA anode and a nickel-based cathode. [9] The anodic coating is a metallic oxide blend, constituted of a mixture of ruthenium and titanium oxides mainly. Beside the importance of chlorine and sodium hydroxide as chemical feedstocks, hydrogen could be fully recovered, power to a significant extent the process itself or serve as an energy vector and further impact different sectors (e.g., mobility). It is therefore evident that the chloralkali process (and oxidation of halides in general) holds an intrinsic economic advantage when compared to the traditional

A comparative performance analysis of stand-alone, off-grid solar-powered sodium hypochlorite generators

“…where j is the measured current density, in mA cm À2 ; E 0 cell the cell working potential (2.188 V), given the negligible effect of the mixing contribution; 26 h Faraday the cell faradaic efficiency; P solar the solar power input (GHI for 4SHJ and 5SHJ; DNI for MJ cells coupled with concentration), in mW cm À2 , retrieved from the LESO-SB weather station online platform. It was estimated that the condence interval for the experimental SCEs was AE7.1%.…”

“…The latter ndings are consistent with other studies previously reported employing GaAs solar cells and solar concentration. 26 It is worth stressing that for a PV technology to ensure stability of operation, it has to full the condition: V MPP > E 0 cell + h, where h corresponds to the reaction overpotentials. In order to maximize the SCE throughput, the electrochemical cell must then be tailored to target the currentload match and to ensure a V OP lower than V MPP .…”

“…The combination of multi-junction solar cells and solar concentrators has proven to be the means to achieve the highest reported SCE for a solar-driven electrochlorinator. 26 In this study, we report a comparative analysis of solarpowered sodium hypochlorite generators employing two different PV technologies: (i) silicon hetero-junction or (ii) multi-junction GaAs solar cells under solar concentration (Fig. 1).…”

Towards industrialization of planar microtracking photovoltaic panels

“…The angular acceptance was validated over AOIs of +/-40° (limited by mechanical constraints that have been lifted since then) with optical efficiencies > 80% of the cosine law (Fig 2b-c). As an application example, the device was used to power an off-grid chloralkali electro-chemical reactor, taking advantage of the MJ cell's large V oc > 3V [9]. Recently, Ito et al published a detailed analysis of a very similar design, demonstrating efficient focusing up to 55° AOI, nearly 30% module efficiency vs direct irradiance, and a 32% increase of power generation with respect to conventional Si cells on a sunny day [10].…”

Miniaturization of InGaP/InGaAs/Ge solar cells for micro‐concentrator photovoltaics

“…While MTC of commercial standard CPV modules is typically between 65% and 75%, miniaturized modules have shown MTC in the range 71%–87% 10 . Consequently, micro‐CPV modules have already demonstrated high efficiency (>35%) with a record of 41.7% 11–18 . A summary of existing high‐performance micro‐CPV modules is reported in Table 1.…”