Optimal and Thermal Design in Transitional Condition of a Paraboidal Solar Furnace for the Hydrogen Production
Abstract
We present the results of the optical and thermal simulation in temporary state of the receiver of a parabolic solar concentrator used as a chemical reactor to produce hydrogen. In a previous experimental work, the reaction of reforming ethanol with the water vapor (ESR) based on a bimetallic catalyst Ni-Co-Hidrotalcita-WOx (HTB-3) with high selectivity for H2, was tested. The activation temperature of the catalyst was 450 oC in a flow of H2 for 30 min, and this temperature was maintained for 30 min more to make three chromatographic analyzes. Then a flow of N2 was introduced to remove all remaining H2 gas inside the reactor. This process was repeated at three temperatures (450 C, 500 C and 550 C). In order to supply the electric energy necessary for the reaction (500 W resistors were used), this work focuses on designing a solar concentrator to replace the resistances. Using the methodology of P.F. Díez, geometric parameters of the paraboloid were calculated, such as the area, angle of opening and the focus, determining the most convenient geometry to concentrate the solar power required to reach the necessary temperature in the solar furnace. A temporary balance of energy was made in the solar concentrator that has served as a chemical reactor, to solve by finite differences the differential equation that determines the temporal evolution of the temperature until reaching at least the 600 C and hold it as long as possible to have the highest production of hydrogen. The results show that the proposed parabolic solar concentrator operating in the city of Hermosillo Sonora, with an irradiance greater than 900 W/m2, reaches average temperatures (in the absorber) above 700 C in 15 minutes and it remains stable for a period close to 7 hours, showing the technical feasibility of the equipment.