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Technology demonstration of large-scale photo-electrochemical system for solar hydrogen production

Periodic Reporting for period 2 - PECSYS (Technology demonstration of large-scale photo-electrochemical system for solar hydrogen production)

Reporting period: 2018-07-01 to 2019-12-31

Solar driven hydrogen generation via water electrolysis is an archetypal use of renewable energy that ensures a sustainable energy supply while minimising green-house emissions. The challenges for adaptation by society are the high cost of the technology and maintaining the reliability of supply compared to conventional energy supply from fossil fuels. Thus the specific objectives of the project are:
• To study and develop devices for integrated photo-electrochemical concepts and scale viable concepts to prototype size > 100 cm².
• To use socio-techno-economic analysis to predict and select concepts with levelised cost of hydrogen production below € 5/kg.
• To scale the prototypes of the less mature but promising technologies to a demonstrator with active area > 10 m².
• To achieve a hydrogen production of 16 gH2/h from the demonstrator resulting from a solar to hydrogen conversion efficiency (ηSTH) of at least 6 %.
• To ensure that the initial solar to hydrogen conversion efficiency of the demonstrator does not reduce by more than 10 % relative after six months of continuous operation.
In the reporting period, five major project achievements have been achieved. Firstly, a 100 sq. cm CuInGaSe-alkaline electrolysis system was built and tested in Uppsala (Sweden) under 1000 W/sq. m illumination achieving a maximum solar to hydrogen (STH) efficiency of 8.5 % and a hydrogen generation rate of 2.87 g/h/sq.m. Secondly a 294 sq. cm silicon heterojunction photovoltaic (PV) module integrated on an alkaline electrolyser was built and tested in Berlin (Germany). The average solar to hydrogen conversion efficiency achieved under 1000 W/m² irradiance was 3.8% for a temperature range of 40-50°C. Both alkaline electrolysis systems used earth abundant transition metal catalysts. Thirdly, outdoor tests in Catania (Italy) of a direct coupling of a 730 sq.cm SHJ bifacial PV module to a single proton exchange membrane (PEM) cell demonstrated STH efficiency of 14% and an average production rate of 2.5 g/h/sq.m for irradiance levels between 800-1200 W/sq.m. Fourthly, in Juelich (Germany), a commercial 2 sq.m SHJ bifacial PV module was coupled to a PEM electrolyser stack and achieved an STH efficiency of 12% with a similar H2 production rate. Lastly, a techno-economic analysis of actually implemented prototypes has revealed that the capital costs of the electrolyser dominates the levelized cost of hydrogen (LOCH) production for all the concepts. However, if the device energy conversion efficiency can be improved significant reductions in the LCOH can be achieved.
The 294 sq. cm silicon heterojunction PV integrated electrolyser was tested under natural sunlight for over 70 hours providing behavioural data under a wide range of weather conditions which is seldom reported in the literature for such devices.Both the silicon heterojunction and CuInGaSe PV integrated electrolysers achieved high efficiency values for their size class in comparison with the state of the art. Also, though direct coupling of PEM electrolysers to commercial size PV modules is not new,uniquely in PECSYS, the operating temperature of the PEM electrolysers is not actively controlled and water is supplied only from the cathode side potentially reducing investment and operating costs. The final project demonstrator test field shall feature a small 80 sq. cm CIGS PV integrated electrolyser, a square metre- sized silicon heterojunction (SHJ) PV integrated electrolyser, several discrete commercial sized SHJ and CIGS PV panels connected to PEM electrolysis stacks with standard and low catalyst loading. Having a mix of technological approaches in the final demonstrator will give us a unique opportunity to study the effect of PV and electrolysis active materials on the device performance and stability behaviour under realistic conditions thus providing a diverse data set for future reference. If the project can successfully upscale the demonstrated laboratory devices using earth abundant materials to a 10 m² demonstrator with high efficiency and long-term durability, then this would contribute progress towards commercialisation of green hydrogen storage for renewable energies. Moreover, the reduction or complete elimination of critical raw materials in the device would also promote faster deployment of the technology on a large scale by reducing the cost of hydrogen.
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