Optimization of operation temperatures and durations during solar thermal water splitting towards greater energy efficiencies

Download
2016
Yavuzyılmaz, Ezgi
Hydrogen production by solar thermal water splitting is an eco-friendly way of storing solar energy in chemical bonds. The most important obstacles for the viability and the commercialization of this technology are lower energy efficiencies and higher production costs compared to conventional hydrogen production ways such as steam reforming, coal gasification, and electrolysis of water. Two-step thermochemical hydrogen production by using solar energy is an alternative method to conventional hydrogen production. In this method, the thermochemical cycle consists of two sequential steps: a high temperature step where the decomposition of the redox material is driven by solar energy and a relatively moderate temperature step where oxidation of the redox material is achieved by steam fed to the reactor. However, the changes in operation temperatures and process durations lead to trade-offs between performance criteria of the reactor. Therefore, the problem of evaluating optimum values for the operation temperatures and durations have extreme significance in terms of achieving high energy efficiencies in the reactor. In this thesis, more than one solution approach is presented for the solution of the problem. Both parametric statistical analysis approach and mathematical optimization methods are adopted to find local optima for operation temperatures and durations. Several local optimum values are presented for the studied specific reactor conditions and alternative cases.  .

Suggestions

Hydrogen production by different strains of Rhodobacter sphaeroides
Gündüz, Ufuk; Yucel, M; Turker, L; Eroglu, L (2000-06-15)
Utilisation of solar energy by photosynthetic microorganisms for H-2 production attracts much interest due to unlimited supply of energy. It is important to identify the most effective strain in terms of hydrogen production for the feasibility of the process. Four different strains of Rhodobacter sp. were grown in a water-jacketed cylindrical glass-column photobioreactor under anaerobic conditions. Growth characteristics and hydrogen production rates were determined. Comparison between strains of Rhodobacte...
Phototrophic hydrogen production by agar-immobilized Rhodobacter capsulatus
Elkahlout, Kamal E. M.; Yücel, Ayşe Meral; Eroğlu, İnci; Department of Biotechnology (2011)
photosynthetic bacteria is attractive field as production is fueled by solar energy. Hydrogen production potential of two photosynthetic bacteria R.capsulatus (DSM1710 wild type and R.capsulatus YO3 Hup- uptake hydrogenase deleted mutant strain) were examined in agar immobilized systems. In the present work agar and glutamate concentrations were optimized for immobilization of bacteria while feeding bacteria with 40/2-4 mM acetate/ glutamate. Immobilized bacteria produced hydrogen for 420-1428 hours coverin...
Development of 100w portable fuel cell system working with sodium borohydride
Erkan, Serdar; Eroğlu, İnci; Department of Chemical Engineering (2011)
Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. A single proton exchange membrane (PEM) fuel cell can only generate electricity with a potential between 0.5V and 1V. The useful potential can be achieved by stacking cells in series to form a PEM fuel cell stack. There is a potential to utilize 100W class fuel cells. Fuelling is the major problem of the portable fuel cells. The aim of this th...
Investigation of various options for numerical modeling of fluidized bedsI for a solar thermal application
Bilyaz, Serhat; Tarı, İlker (null; 2015-05-29)
Circulating fluidized bed solid particle absorption solar thermal energy system is a promising approach to solar thermal with thermal energy storage. For accurately modeling such systems, the fluidized bed numerical model should be correctly representing the behavior of the actual bed. There are several suggested partial semi-empirical models in the literature considering distinct phenomena related to fluidization and void fraction distribution in a fluidized be...
Modeling and design of reactor for hydrogen production using non-stoichiometric oxides
Yılmaz, Arda; Kıncal, Serkan; Department of Chemical Engineering (2017)
Nowadays countries investigate to improve alternative energy technologies such as solar power, biomass, wind energy, hydrogen etc. Hydrogen gas is very useful energy carrier and fuel cells produce electricity through hydrogen gas. Hydrogen production technologies are also investigated by many researches due to its high cost production. Thermochemical production way is one of the hydrogen production methods. Solar energy is also clean, renewable and alternative energy source. It is used for heating reaction ...
Citation Formats
E. Yavuzyılmaz, “Optimization of operation temperatures and durations during solar thermal water splitting towards greater energy efficiencies,” M.S. - Master of Science, Middle East Technical University, 2016.