الفهرس | Only 14 pages are availabe for public view |
Abstract Nowadays, replacing fossil fuels with a sustainable and environmentally safe alternative energy source represents great challenges for scientists and researchers in related areas. Hydrogen can be considered as the best candidate for replacing the fossil fuel for its cleanliness, readily available and highly efficient. Photo-electrochemical (PEC) water splitting system for hydrogen production is one of the promising technology that utilizes renewable energy (sunlight and water). However, the low efficiency of this technique is the utmost challenge for hydrogen production. The goal of this thesis is to study different designs of PEC reactors to elevate the temperature of the electrolyte and consequently lower the water splitting potential. Therefore, three different designs of PEC reactors are developed. The first design is contained multi-junction electrodes as photoanode and cathode. The solar irradiance enters the reactor from the right side wall and the others walls are insulated to reduce the heat losses. In the second one, the photoanode and cathode are separated and the solar irradiance enters the reactor from the right side wall. For both the first and second design, a good absorptivity glass is placed at the back of the reactor adjacent to the insulated wall to act a storage for long wavelength. In the last design, the solar irradiance entered into the reactor from right side and left side. In this thesis, numerical study of governing equations in photo-electrochemical (PEC) reactor is performed. The present models comprise of the Navier-Stokes and the respective energy equations for electrolyte, and the radiative transfer equation Abstract iii (RTE). Commercial software, ANSYS FLUENT 14.0 is used to solve the governing equations using the SIMPLEC algorithm. Based on the numerical results, the soar-to-hydrogen efficiency (𝜂���� and hydrogen volume production rate (𝛷, are assessed. The results have shown that the solar-to-hydrogen efficiency (𝜂���� and the hydrogen volume production rate (𝛷 are increased as the solar flux is increased for all three proposed designs. In addition, the second design is the best one which achieved the maximum solar-to-hydrogen efficiency (𝜂���� and the hydrogen volume production rate (𝛷 due to the minimum heat loss compared with the other designs. Comparison between currently predicted results and the previous data indicates an enhancement of solar-to-hydrogen efficiency and hydrogen production that can be achieved with the current suggested designs. |