A 24.4% solar to hydrogen energy conversion efficiency by combining concentrator photovoltaic modules and electrochemical cells

Nakamura, Akihiro; Ota, Yasuyuki; Koike, Kayo; Hidaka, Yoshihide; Nishioka, Kensuke; Sugiyama, Masakazu; Fujii, K.

doi:10.7567/apex.8.107101

Cited by 144 publications

(110 citation statements)

References 30 publications

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“…[32][33][34] Due to the lack of CIPEC device demonstration, we separately validate the PV and EC component. The experimental validation for PV and EC components is presented in Figs.…”

Section: Resultsmentioning

confidence: 99%

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Tembhurne

Haussener

2016

J. Electrochem. Soc.

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We investigate the direct conversion of solar energy and water into a storable fuel via integrated photo-electrochemical (IPEC) devices. Here we focus particularly on a device design which uses concentrated solar irradiation to reduce the use of rare and expensive components, such as light absorbers and catalysts. We present a 2-dimensional coupled multi-physics model using finite element and finite volume methods to predict the performance of the IPEC device. Our model accounts for charge generation and transport in the photoabsorber, charge transport in the membrane-separated catalysts, electrochemical reaction at the catalytic sites, fluid flow and species transport in the porous charge collectors and channels, and radiation absorption and heat transfer for all components. We then develop performance optimization strategies utilizing device design, component and material choice, and adaptation of operational conditions. Our model predicts that operation under high irradiation is possible and that dedicated thermal management can ensure high performant operation. The model shows to be a valuable tool for the design of IPEC devices under concentrated irradiation at elevated temperatures. To our knowledge, it is the most detailed yet computationally low-cost model of an IPEC device reported. The solar energy received on earth's surface can meet mankind's current and future energy demand.1,2 Direct conversion of solar energy and water into chemical energy via photo-electrochemical (PEC) processes is one viable route for renewable fuel processing and energy storage. Integrated photo-electrochemical (IPEC) devices, i.e. composed of an integrated buried photovoltaic (PV) component and an integrated electrochemical component (consisting of membraneseparated catalysts and porous charge collectors), allow circumvention of some of the challenges imposed by solid-liquid interfaces in traditional PEC devices, while also exhibiting potential to operate at higher efficiencies and lower cost than externally wired (non-integrated) PV plus electrolyzer (EC) devices. [3][4][5] We refer to the design as "integrated" to signify that the PV and electrolyzer components are area-matched and in direct contact, allowing heat transfer from one component to the other and for thermal management strategies to be applied. In order to increase the economic competitiveness of IPEC devices compared to conventional hydrogen generation pathways, we consider concentration of irradiation. [6][7][8] This leads to large driving current densities (approximately proportional to the concentration factor), and thus introduces larger overpotentials and potential mass transport limitations.9 Concentration also decreases the performance of the photoactive components due to increased temperature. On the other hand, the kinetics are enhanced with increased temperature. Ionic transport in the solid electrolyte is also enhanced with increased temperature, but this increase stops abruptly and sharply drops at temperatures above 120• C due to membrane dry out. ...

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“…[32][33][34] Due to the lack of CIPEC device demonstration, we separately validate the PV and EC component. The experimental validation for PV and EC components is presented in Figs.…”

Section: Resultsmentioning

confidence: 99%

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Tembhurne

Haussener

2016

J. Electrochem. Soc.

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“…Theoretical studies using a variety of assumptions have predicted that the maximum attainable efficiency using a tandem PEC water splitting device is 23–32% (refs 17, 18, 19, 20). PV-electrolysis systems have demonstrated exceptional potential to achieve even higher STH efficiencies811212223242526. The highest STH efficiency demonstrated to date, 24.4%, was delivered by a PV-electrolysis system using GaInP/GaAs/Ge multi-junction solar cells and polymer electrolyte electrochemical cells24.…”

mentioning

confidence: 99%

“…PV-electrolysis systems have demonstrated exceptional potential to achieve even higher STH efficiencies811212223242526. The highest STH efficiency demonstrated to date, 24.4%, was delivered by a PV-electrolysis system using GaInP/GaAs/Ge multi-junction solar cells and polymer electrolyte electrochemical cells24. For comparison, the best multi-junction PV created to date demonstrated a solar-to-electricity conversion efficiency of 46.0% under concentrated illumination27.…”

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confidence: 99%

Solar water splitting by photovoltaic-electrolysis with a solar-to-hydrogen efficiency over 30%

et al. 2016

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Hydrogen production via electrochemical water splitting is a promising approach for storing solar energy. For this technology to be economically competitive, it is critical to develop water splitting systems with high solar-to-hydrogen (STH) efficiencies. Here we report a photovoltaic-electrolysis system with the highest STH efficiency for any water splitting technology to date, to the best of our knowledge. Our system consists of two polymer electrolyte membrane electrolysers in series with one InGaP/GaAs/GaInNAsSb triple-junction solar cell, which produces a large-enough voltage to drive both electrolysers with no additional energy input. The solar concentration is adjusted such that the maximum power point of the photovoltaic is well matched to the operating capacity of the electrolysers to optimize the system efficiency. The system achieves a 48-h average STH efficiency of 30%. These results demonstrate the potential of photovoltaic-electrolysis systems for cost-effective solar energy storage.

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“…Two examples of experimental investigation of non-integrated PEC devices using concentrated irradiation demonstrate that very interesting efficiencies can be achieved. 8,9 However, irradiation concentration leads to driving current densities which are approximately proportional to the concentration factor, thus inducing larger overpotentials and possible mass transport limitations. 10 Optical concentration generally increases the device temperature and consequently enhances the kinetics and the ionic transport in the solid electrolyte (its conductivity drops, however, at temperatures above 120…”

mentioning

confidence: 99%

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Tembhurne

Haussener

2016

J. Electrochem. Soc.

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Concentrating solar irradiation for use in integrated photo-electrochemical devices potentially provides an economically competitive pathway for hydrogen generation, even with partial use of rare material components. Heat transfer and thermal management are crucial in devices operating under large irradiation concentrations. With dedicated thermal management, detailed 2-dimensional multiphysics modeling predicts high performance. Two competing operational parameter spaces are observed: i) thermal effects enhance performance in the zone of low operational current density, and ii) mass transport limits dominate in the zone of high operational current density (saturation current of the electrolyzer component). These competing effects lead to tradeoffs between device efficiency and hydrogen evolution rate, quantified using Pareto frontiers. Smart thermal management -only possible through integrated device design -helps in achieving efficient and low cost production of solar fuels, and can further alleviate degradation-related performance decreases over the lifetime of the device. For example, at an irradiation concentration of 707, a 12% degradation in STH efficiency of a Si-based device is compensated by a seven-fold increase in the water mass flow rate. Integrated photo-electrochemical device designs combined with smart thermal management prove to be a practical and economically feasible approach to solar fuel processing, and provide a pathway to circumvent limitations imposed by materials. The solar energy received on earth's surface, capable of meeting mankind's current and future energy demands, 1-4 can be directly converted into electricity using photovoltaic cells. However, electricity is difficult and costly to store, and considerable losses are accrued when attempting to distribute it over long distances. This problem can be circumvented by directly converting the photon energy into fuels. The simplest reaction considered is the electrolysis of water to produce hydrogen. Hydrogen can become a complementing energy carrier, and can be used as an energy-rich reagent for the exothermic formation of methane, methanol, or hydrocarbons using atmospheric CO 2 as a carbon feedstock. To realize this goal, practical means for sustainable hydrogen production are needed. Today more than 95% of global hydrogen production is based on steam reforming of fossil fuels.5 A promising sustainable approach to hydrogen production is solar driven, using integrated photo-electrochemical (IPEC) pathways. An IPEC device is defined as a device in which an area-matched photoabsorber and electrocatalyst are in direct contact. We propose an integrated photo-electrochemical device design, shown in Fig. 1. This device profits from the exclusion of direct semiconductor-electrolyte interfaces prone to interface degradation issues, and limits the transmission losses occurring in completely unintegrated, externally wired photovoltaic plus electroyzer systems. The design incorporates an electronic conductor for the transfer of charge carriers f...

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A 24.4% solar to hydrogen energy conversion efficiency by combining concentrator photovoltaic modules and electrochemical cells

Cited by 144 publications

References 30 publications

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Solar water splitting by photovoltaic-electrolysis with a solar-to-hydrogen efficiency over 30%

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

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