Development of Reactive Ceramics for Conversion of Concentrated Solar Heat Into Solar Hydrogen With Two-Step Water-Splitting Reaction

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
H. Kaneko ◽  
S. Taku ◽  
Y. Naganuma ◽  
T. Ishihara ◽  
N. Hasegawa ◽  
...  
Keyword(s):  
Solid Solution ◽  
Partial Pressure ◽  
Water Splitting ◽  
Thermal Energy ◽  
Rapid Heating ◽  
Nonequilibrium State ◽  
Solar Thermal Energy ◽  
O2 Partial Pressure ◽  
High O2 ◽  
Institute Of Technology

The reactive ceramics suitable for the rotary-type solar reactor (proposed by Tokyo Institute of Technology, Tokyo) with two-step water-splitting reaction were developed. It is confirmed that O2 gas is evolved in the two-step water-splitting reaction with the reactive ceramics vigorously by rapid heating (α-O2-releasing reaction). The α-O2-releasing reaction is due to the formation of interstitial defect and the conversion of lattice oxygen into O2 gas at a nonequilibrium state. Reactive ceramics (NiFe2O4 and yttria stabilized zirconia (YSZ)-NiFe2O4 solid solution) can absorb solar thermal energy and convert thermal energy into chemical energy under high O2 partial pressure atmosphere in the α-O2-releasing reaction. Repetitive evolutions of O2 gas were observed in the two-step water-splitting reaction with YSZ-Fe3O4 solid solution and cerium based metal oxides (CeO2–NiO, CeO2–ZrO2, and CeO2–Ta2O5) at high O2 partial pressure. The CeO2–Ta2O5(Ce:Ta=90:10) released a large amount of O2 gas (3.95 cm3/g) in the α-O2 releasing reaction in the flow of air.

H2 Generation by Two-Step Water Splitting With CeO2-MOx Using Concentrated Solar Thermal Energy

Solar Energy ◽  
2006 ◽  
Author(s):  
Hiroshi Kaneko ◽  
Hideyuki Ishihara ◽  
Takao Miura ◽  
Hiromitsu Nakajima ◽  
Noriko Hasegawa ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Thermal Energy ◽  
Infrared Imaging ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Simulator ◽  
Solar Hydrogen ◽  
H2 Generation ◽  
Solar Hydrogen Production

CeO2-MOx (M = Mn, Fe, Ni, Cu) reactive ceramics, having high melting points and high conductivities of O2−, were synthesized with the combustion method from their nitrates for solar hydrogen production. The prepared CeO2-MOx samples were solid solutions between CeO2 and MOx with the fluorite structure through XRD. Two-step water splitting reactions with CeO2-MOx reactive ceramics proceeded at 1573–1773K for the O2 releasing step and at 1273K for the H2 generation step by irradiation of infrared imaging furnace as a solar simulator. The amounts of O2 evolved in the O2 releasing reaction with CeO2-MOx and CeO2 systems increased with the increase of the reaction temperature. The amounts of H2 evolved in the H2 generation reaction with CeO2-MOx systems except for M = Cu were more than that of CeO2 system after the O2 releasing reaction at the temperatures of 1673 and 1773K. The largest amount of H2 was generated with CeO2-NiO after the O2 releasing reaction at 1573, 1673 and 1773K. The O2 releasing reaction at 1673K and H2 generation reaction at 1273K with CeO2-Fe2O3 were repeated four times with the evolving of O2 (1.3cm3/g-sample) and H2 (2.3cm3/g-sample) gases, respectively. The possibility of solar hydrogen production with CeO2-MOx (M = Mn, Fe, Ni) reactive ceramics system by using concentrated solar thermal energy was suggested.

Fabrication of Pt-IrOx and Au-V2O5 Thin Films

2007 ◽  
Vol 345-346 ◽  
pp. 735-740 ◽  
Author(s):  
Richard P. Vinci ◽  
T. Bannuru ◽  
Seung Min Hyun ◽  
Walter L. Brown
Keyword(s):  
Thin Films ◽  
Partial Pressure ◽  
Oxygen Affinity ◽  
Thermodynamic Characteristics ◽  
Oxide Dispersion Strengthened ◽  
Oxygen Solubility ◽  
Post Annealing ◽  
O2 Partial Pressure ◽  
High O2 ◽  
Equilibrium Oxygen

Pt-IrOx and Au-V2O5 thin films were created by magnetron co-sputtering from multiple targets in an Ar-O2 mixture. Successful Pt-IrOx production required high O2 partial pressure and slow deposition rate followed by post-annealing in pure O2. In contrast, deposition of Au-V2O5 films required relatively low O2 partial pressure, and did not need any post-anneal. These different strategies for forming oxide dispersion strengthened films in a multi-target reactive sputtering configuration are directly related to the thermodynamic characteristics of the two materials systems. The most important characteristics are the low equilibrium oxygen solubility in Pt and Au, and the different degrees of oxygen affinity by Ir and V.

O2 Releasing Reactivity of Ceramics for Rotary-Type Solar Reactor With Two-Step H2O Splitting

2009 ◽  
Author(s):  
Yutaka Tamaura ◽  
Hiroshi Kaneko
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Water Splitting ◽  
Thermal Energy ◽  
Reaction Rate ◽  
Chemical Energy ◽  
Solar Thermal Energy ◽  
Solar Reactor ◽  
Temperature Swing ◽  
Rotary Type

The relationship among the factors determining the thermal efficiency to convert concentrated solar thermal energy to chemical energy by the O2-releasing reaction of the reactive ceramics in the tow-step water splitting process has been studied for the development of rotary-type solar reactors. The α O2-releasing reaction which has been discovered in the present study for Ni-ferrite (NiFe2O4) has a high chemical reaction rate (k = 0.50 mol sec−1/m2). From calculation with the heat transfer equation in terms of heat transfer through the cavity wall with thckness, d (m), and heat absorption by the endothermic process of the O2-releasing reaction with rate constant, k (mol sec−1/m2), it is cralified that the heat flux of 2000 kW/m2 can be absorbed by the α O2-releasing reaction using the cavity wall with the thickness, d = 0.00036 m and thermal conductivity, λ = 70 WK−1m−1. The heat loss in the temperature swing (ΔT = 300K) for the two step water splitting of O2 releasing step (TH = 1773K) and H2 generation step (TL = 1473K) is only 8.3% for the α O2-releasing reaction. However, the O2 releasing reaction of NiFe2O4 in the β region where the reaction rate constant is around 0.0001 mol sec−1/m2, the heat flux of the concentrated solar energy to be used for conversion to chemical energy becomes very low around 300 kW/m2; the heat loss by the temperature swing in the two step water splitting is 87%. It is concluded that the α O2-releasing reaction can be used for the rotary-type solar reactor to convert the concentrated solar thermal energy to chemical energy with a high efficiency.

Hydrogen Production by Solar Thermochemical Water-Splitting/Methane-Reforming Process

Solar Energy ◽  
2003 ◽  
Author(s):  
Tatsuya Kodama ◽  
Yoshiyasu Kondoh ◽  
Atsushi Kiyama ◽  
Ken-Ich Shimizu
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Reduction Process ◽  
Thermal Reduction ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Thermochemical

Two different routes of solar thermochemical hydrogen production are reviewed. One is two-step water splitting cycle by using a metal-oxide redox pair. The first step is based on the thermal reduction of metal oxide, which is a highly endothermic process driven by concentrated solar thermal energy. The second step involves water decomposition with the thermally-reduced metal oxide. The first thermal reduction process requires very-high temperatures, which may be realized in sun-belt regions. Another hydrogen production route is solar reforming of natural gas (methane), which can convert methane to hydrogen via calorie-upgrading by using concentrated solar thermal energy. Solar reforming is currently the most advanced solar thermochemical process in sun belt. There is also possibility for the solar reforming to be applied for worldwide solar concentrating facilities where direct insolation is weaker than that in sun belt. Our experimental studies to improve the relevant catalytic technologies are shown and discussed.

Reactive ceramics of CeO2–MOx (M=Mn, Fe, Ni, Cu) for H2 generation by two-step water splitting using concentrated solar thermal energy

Energy ◽  
2007 ◽  
Vol 32 (5) ◽  
pp. 656-663 ◽  
Author(s):  
H KANEKO ◽  
T MIURA ◽  
H ISHIHARA ◽  
S TAKU ◽  
T YOKOYAMA ◽  
...  
Keyword(s):  
Water Splitting ◽  
Thermal Energy ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
H2 Generation

Pyrazolium Phase Change Materials for Solar-Thermal and Wind Energy Storage

2019 ◽  
Author(s):  
Karolina Matuszek ◽  
R. Vijayaraghavan ◽  
Craig Forsyth ◽  
Surianarayanan Mahadevan ◽  
Mega Kar ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
High Efficiency ◽  
Scale Up ◽  
Solar Thermal ◽  
Energy Storage Materials ◽  
Solar Thermal Energy ◽  
Storage Materials

Renewable energy has the ultimate capacity to resolve the environmental and scarcity challenges of the world’s energy supplies. However, both the utility of these sources and the economics of their implementation are strongly limited by their intermittent nature; inexpensive means of energy storage therefore needs to be part of the design. Distributed thermal energy storage is surprisingly underdeveloped in this context, in part due to the lack of advanced storage materials. Here, we describe a novel family of thermal energy storage materials based on pyrazolium cation, that operate in the 100-220°C temperature range, offering safe, inexpensive capacity, opening new pathways for high efficiency collection and storage of both solar-thermal energy, as well as excess wind power. We probe the molecular origins of the high thermal energy storage capacity of these ionic materials and demonstrate extended cycling that provides a basis for further scale up and development.

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