Martin Roeb's research while affiliated with German Aerospace Center (DLR) and other places

Publications (492)

Article
Solar thermochemical water splitting via a two-stage redox cycle has been subjected to numerous theoretical and experimental studies since a couple of decades. It has been considered as a promising technology to generate green hydrogen as it is feasible to directly convert concentrated solar radiation into storable chemical energy. The present arti...
Article
The influence of ionic radii and valence of dopants in Ce0.9LaxYbyZr0.1−x−yO2−δ (x = 0, 0.05, 0.1, y = 0, 0.05, 0.1) on the oxidation kinetics were investigated by thermogravimetric analysis in synthetic air and were compared to undoped ceria. Samples co-doped with Zr–La and Zr–Yb exhibited moderate oxidation kinetics that were slower than undoped...
Article
Technologies to capture carbon dioxide (CO2) from industrial processes are needed to reach the climate change goals. In case of the cement industry, calcium looping cycle (CaL cycle) for CO2 capturing has gained more attention not only because it can be integrated in an existent cement plant, but also because the calcination step of the CaL cycle c...
Article
The present work is part of an approach targeted on demonstrating a concentrated solar energy-driven thermochemical cycle employing solid elemental sulphur as a chemical energy vector and a seasonal solar energy storage medium. In exploring the concept of coupling this cycle to a centrifugal particle solar receiver, bauxite-based particles, commerc...
Article
The ability to store energy in the form of high-temperature heat is one of the key advantages of concentrated solar energy over other renewable sources. Higher energy densities compared to the state of the art can be achieved through a wider range of operating temperatures and by adding chemical energy storage. Thermochemical storage (TCS) systems...
Article
The inherent capability of concentrated solar power (CSP) plants for sensible thermal energy storage ensures their continuous operation and is considered their most crucial competitive edge versus other renewable energy sources. The storage density of air‐operated CSP plants can be significantly increased by hybridizing sensible with thermochemical...
Article
Full-text available
Solar thermochemical water-splitting cycle models for hydrogen production with single and multiple receivers working between 1773 K and 1173 K are developed. The receiver pressures and aperture sizes are optimized for maximum cycle efficiency. The efficiency of the cycle increases with the number of receivers because of the decrease in vacuum pump...
Article
Full-text available
This paper reports on the numerical analysis of a volumetric solar receiver-reactor for hydrogen production, using the 2-step reduction–oxidation cycle. A detailed parametric sweep covering hundreds of various parameter combinations is performed for a large solar reactor, using a transient physical model. We generate performance maps which are curr...
Article
In solar thermochemical redox cycles for H2O/CO2-splitting, a large portion of the overall energy demand of the system is associated with heating the redox material from the oxidation temperature to the reduction temperature. Hence, an important measure to improve the efficiency is recuperation of sensible heat stored in the redox material. A solid...
Article
Full-text available
Global trade of green hydrogen will probably become a vital factor in reaching climate neutrality. The sunbelt of the Earth has a great potential for large-scale hydrogen production. One promising pathway to solar hydrogen is to use economically priced electricity from photovoltaics (PV) for electrochemical water splitting. However, storing electri...
Article
Electrolysis and thermochemical water splitting are approaches to produce green hydrogen that use either an electrical potential (electrolysis) or a chemical potential (thermochemical water splitting) to split water. Electrolysis is technologically mature when applied at low temperatures, but it requires large quantities of electrical energy. In co...
Article
Large progress has been made in the last decades to reduce the carbon footprint of ammonia, which is an essential commodity of the food, chemical and energy industry. Apart from alternative routes for green feedstock production, such as hydrogen via electrolysis and nitrogen via solar thermochemical methods, alternatives are explored to replace the...
Chapter
The high-temperature heat produced through concentrated solar irradiation facilities can be exploited to cover partially or totally the enthalpy needs of endothermal reactions of significant industrial importance and scale like methane reforming. This so-called solar thermal methane reforming can serve as a “bridge technology” based initially on fo...
Article
Solar thermochemical redox cycles could be a path to efficient, large-scale renewable hydrogen production. A new receiver-reactor concept is presented that combines characteristics of the most successful receiver-reactor systems to date, with features of concepts showing the highest efficiency potential. The key features of the system are movable r...
Conference Paper
Ammonia is one of the most-produced chemicals in the world. It is applied in the fertilizer industry, and nitrogen fertilizers are a necessity to feed the world's growing population. Due to the high energy demand of the Haber- Bosch ammonia synthesis process, and due to the energy-intensive production of its precursors hydrogen and nitrogen, this p...
Conference Paper
The recently demonstrated potential of centrifugal particle receivers to provide hot particle streams of temperatures above 950°C as heat transfer fluid and solar energy storage material in the form of sensible heat opens new possibilities in performing endothermic chemical reactions that take place below this temperature in solar tower plants. Of...
Article
Ammonia is one of the most-produced chemicals in the world. It is applied in the fertilizer industry, and nitrogen fertilizers are a necessity to feed the world's growing population. Due to the high energy demand of the Haber- Bosch ammonia synthesis process, and due to the energy-intensive production of its precursors hydrogen and nitrogen, this p...
Conference Paper
Rotary kilns are very robust and versatile reactors and can be used on solar towers to perform high-temperature endothermic thermal decomposition reactions of solid materials with the aid of concentrated solar irradiation. Their easy functioning system allows flexibility with respect to a wide range of operating conditions, such as particle size, r...
Article
The recently demonstrated potential of centrifugal particle receivers to provide hot particle streams of temperatures above 950°C as heat transfer fluid and solar energy storage material in the form of sensible heat opens new possibilities in performing endothermic chemical reactions that take place below this temperature in solar tower plants. Of...
Conference Paper
The contractual objective to limit the global temperature rise well below 2°C represents a milestone in international climate policy and requires the timely development of strategies that provide solutions to how effective energy-saving pathways can be realized. The defossilisation of the energy system plays a key role here. But the transport secto...
Presentation
Full-text available
Research on the combination of a PSA with a thermochemical cycle for pure nitrogen production.
Conference Paper
A proof of concept sulphuric acid splitting/decomposition prototype driven by hot bauxite particles is designed and developed. The lab-scale test reactor is a novel counter-current flow shell-and-tube heat exchanger with particles on the shell side and sulphuric acid on the tube side with mass flow rates of 10 kg/h and 2 kg/h, respectively. A one-d...
Article
Full-text available
Wasserstoff hat das Potenzial, der zentrale Baustein für eine Energiewirtschaft mit massiv reduzierten Treibhausgasemissionen zu sein. Er bietet Antworten auf bisher ungelöste Fragen der Energiewende, insbesondere in den Bereichen Transport und Langzeitspeicherung. Wasserstoff ermöglicht es außerdem industrielle Prozesse emissionsfrei zu gestalten,...
Conference Paper
Overview on State of the Art of solar thermal water and CO2 splitting and on looping processes for CO2 capture
Article
Hydrogen production by solar-driven 2-step reduction–oxidation cycles has been successfully demonstrated in recent years. While the demonstrated efficiencies were quite low (up to 5.25% solar-to-fuel efficiency), there is a large potential for much higher efficiencies. This paper presents a detailed parametric investigation of a large scale (>100 k...
Conference Paper
In solar thermochemical redox cycles for H2O/CO2-splitting, a large portion of the overall energy demand of the system is associated with heating the redox material from the oxidation temperature to the reduction temperature. Hence, an important measure to improve the efficiency is recuperation of sensible heat stored in the redox material. A solid...
Conference Paper
Overview on DLR's and IMDEA Energia's solar water and CO2 splitting projects
Article
Sustainable energy supply is a crucial issue in times of climate change and receding fossil energy reserves. The emerging field of solar-driven thermochemical H2O and CO2 splitting cycles is a very promising approach to address this challenge. Providing low oxygen partial pressures is crucial in these processes. This issue is tackled by either high...
Conference Paper
Overview on DLR activities on solar fuel and chemical production
Article
Solar redox reforming is a process that uses solar radiation to drive the production of syngas from natural gas. This approach caught attention in recent years, because of substantially lower reduction temperatures compared to other redox cycles. However, a detailed and profound comparison to conventional solar reforming has yet to be performed. We...
Article
Concentrated solar thermal technology is considered a very promising renewable energy technology due to its capability of producing heat and electricity and of its straightforward coupling to thermal storage devices. Conventionally, this approach is mostly used for power generation. When coupled with the right conversion process, it can be also use...
Article
Full-text available
The perovskite oxide SrFeO3 has favourable redox properties for oxygen exchange applications, including oxygen separation and oxygen production chemical looping cycles. For such applications, lower temperature operation can improve the energy demand and feasibility of the process, but can also lead to kinetic limitations. Here we investigate the ox...
Article
Solar CO2/H2O splitting via two-step thermochemical cycles of metal oxides is a promising path for solar energy conversion to carbon-neutral, liquid hydrocarbons from virtually inexhaustible resources, water and (waste) carbon dioxide, with high theoretical efficiency potential. Cerium-based oxides have seen enormous interest and research efforts s...
Conference Paper
Production of ammonia from solar radiation air and water by thermochemical cycles.
Article
Apart from being a major feedstock for chemical production, hydrogen is also a very promising energy carrier for the future energy. Currently hydrogen is predominantly produced via fossil routes, but as green energy sources are gaining a larger role in the energy mix, novel and green production routes are emerging. The most abundant renewable hydro...
Conference Paper
Solar production of Calcium Oxide (CaO) is a promising way to reduce the CO2 emissions from the cement industry. To carry out this thermochemical process, closed solar reactors with continuous processing are needed. Indirect heated solar reactors to carry out this process have been designed and tested at lab-scale. However, the main drawback of the...
Article
Full-text available
Conventional productions of large volume of hydrogen from fossil based resources continue to play a key role in the hydrogen economy. This paper recalls the contribution of these conventional technologies with new technological development and researches. Providing gradual integration of renewable solutions into large-scale production, some emergin...
Conference Paper
Full-text available
The present research focuses on modeling of solar thermal driven fuel production plant with CO2 and H2O as raw materials to produce synthetic gas (syngas) which is converted into hydrocarbons through Fischer-Tropsch process either with Fe and Co catalyst to produce diesel, gasoline and kerosene. The solar reactor uses cerium oxide (CeO2) as a metal...
Article
Solar CO2/H2O splitting via two-step thermochemical cycles of metal oxides is a promising path for solar energy conversion to carbon-neutral, liquid hydrocarbons from virtually inexhaustible resources, water and (waste) carbon dioxide, with high theoretical efficiency potential. Cerium-based oxides have seen enormous interest and research efforts s...
Conference Paper
Converting solar energy efficiently into hydrogen is a key element to develop a sustainable and affordable hydrogen economy. The presentation will give an insight in how concentrated solar radiation can be coupled into hydrogen production processes. It will discuss the benefits and challenges of using the sunlight directly instead of converting it...
Article
Within the general framework of investigating novel routes for solar hydrogen production, the idea of combining a solar centrifugal particle receiver with sulphur thermochemical cycles, involving SO3 dissociation to SO2 and O2 as key step, is pursued. In this perspective, the present work concerns the synthesis, development, evaluation and characte...
Article
Full-text available
Solar thermochemical cycles are promising processes for the efficient production ofrenewable hydrogen at large scale. One area for process optimization is the high temper-ature reduction step. The oxygen released during this step has to be removed from thereactor in order to increase the reduction extent of the redox material. If low partialpressur...
Article
Perovskites are excellent candidate materials as oxygen carriers in thermochemical processes. Due to their versatile composition, it is possible to fine-tune the perovskite’s properties. We present a method for the rational design of AMO3-δ perovskite solid solutions with two different species on the Msite in order to tune their redox behavior. To...
Article
Full-text available
Although the utilization of concentrated solar power (CSP) for electricity production is already at commercial stage, the application to energy intensive industrial processes is still at an early stage. Among these, the cement industry is one of the biggest CO 2-emitters and requires temperature levels achievable with concentrated solar radiation....
Article
The achievement of low oxygen partial pressures is beneficial in a number of applications, including the production of nitrogen for the Habor-Bosch process, one of the largest industrial chemical processes. It has been suggested in the literature that a redox cycle can be utilized for selective oxygen adsorption, with the potential for application...