(222bj) A Comprehensive Energy Analysis of Photovoltaic Thermal Water Electrolyzer for Hydrogen Production

Solar energy is often harnessed by using a photovoltaic/thermal (PVT) collector, where a photovoltaic (PV) module and a thermal collector convert solar energy into electricity and heat, respectively [1]. The heat energy has been conventionally used for domestic hot water and/or room heating; it is, however, highly desirable to convert the released energy into alternative storable forms. Hydrogen is environmentally friendly and a sustainable energy carrier that can be stored. Currently the PV-assisted water electrolyzers available on the market have PV conversion efficiencies of only 15%.  The energy that is not transformed into electricity is just dissipated. To this end, we have developed a new integrated system – so-called “photovoltaic thermal water electrolyzer” – which consists of PV cells positioned on top of a planar micro water electrolyzer. Using this system, we utilize the released heat to raise the temperature of the electrolyte solution, thereby increasing the efficiency of hydrogen production. Herein, we provide a comprehensive analysis of the overall energy output efficiency of a PVT water electrolyzer.

The hourly radiation and ambient temperature data of Phoenix are used in our model. The temperature of PV module and the electrolyte are computed using COMSOL Multiphysics software. The 3D design of the PV system and water electrolyzer, which includes a 400 um thick electrolyzer chamber, is presented. The electrical output of the PV was calculated based on the work of presented in reference [2]. The efficiency of the water electrolyzer is calculated from the data reported in the literature at constant current flux as 10mA/cm² [3]. The analysis for the day June 21^st 2010 indicates that the highest efficiency difference between the PV modules with and without water electrolyzer is 2%. At the same time the improvement in the efficiency of the water electrolyzer is around 6%, which means an overall increase of 4% in the efficiency of the integrated system. This new integrated approach is advantageous over PV module and water electrolyzer systems as it utilizes heat into efficient hydrogen production, less space occupation with architectural uniformity, and reduces installation costs.