Komplementäre Dekarbonisierung der Erzeugung von Elektroenergie und Gewinnung synthetischer Kraftstoffe durch Erneuerbare Energien und fossile Energieträger

The concept of complementary decarbonisation of power generation from renewable energy sources and fossil fuels consists of their integration in one system. A technology network in the form of a CCU‐combined power plant is proposed for the energy generation from fossil fuels by a coal power plant with CO₂ recovery from the exhaust gases and a pyrolysis of natural gas to hydrogen and carbon as a basic technology. This technology network is completed by a reverse water‐gas shift reaction for the conversion of the CO₂ to CO, which will react with the hydrogen in a Fischer‐Tropsch synthesis for synthetic diesel. The recovered energy from the exothermic Fischer‐Tropsch synthesis meets the energy needs of CO₂ scrubbing. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered.     

Long-term scenarios for energy and environment: Energy from the desert with very large solar plants using liquid hydrogen and superconducting technologies

Among the long-term energy scenarios identified by major international organizations in order to drastically reduce fossil fuels consumption and to develop a sustainable energy system within the 21st century, the exploitation of desert areas for large-scale renewable energy production, must be seriously considered. Desert areas are characterized by large land availability, with high levels of solar radiation and wind. However, apart from generating costs (which should fall down in future), two main problems have to be faced. First, fluctuations of renewable power availability may lead to electric grid instability, reducing the quality of energy supply. Second, since deserts are typically far from energy-demanding areas, large power transport lines are needed. The system proposed in this paper resorts to the use of liquid hydrogen (LH₂) for energy storage, and to the combined transport of electric energy and LH₂ with a MgB₂ superconducting line. The system allows flexible delivering of energy in electric and chemical form, depending on end-users demands.     

Numerische Simulationen der katalytischen Methanisierung von CO2 in einem pseudo‐homogenen Strömungsrohr

Power to gas is an attractive option for storing excess energy from fluctuating renewable energy sources. In recent years, the concept has gained great interest. An essential part of the process chain of power to gas is the methanation of CO₂. Within this work the catalytic methanation of pure CO₂ and of biogas is modeled in a three‐dimensional polytropic pseudo‐homogeneous flow tube and numerically simulated at different loads. The results represent axial and radial quantitative information about the reaction behavior under the different boundary conditions.     

Influence of Power-to-Fuel Plant Flexibility Towards Power and Plant Utilization and Intermediate Hydrogen Buffer Size

Conversion of intermittent renewable energy into synthetic fuels and chemicals is required to secure long-distance transport and feedstock for chemical industry. Due to the fluctuating energy generation, process intensification and feed flexibility are essential. This contribution investigates the importance of feed flexibility on the buffer size with applying a 20:80 scenario of wind/solar energy generation. The degree of power and plant utilization are calculated. With the capability to accept a lower load bound of 17 % after only 10 min, a minimum tank capacity of only 1.3 h is calculated to avoid a fuel plant stop throughout a calendar year. Additional tank capacity for peak power compensation in the range of ∼10 h is beneficial for the utilization degree of power and under the prerequisite of a load-flexible fuel plant.     

Osmotic power — power production based on the osmotic pressure difference between waters with varying salt gradients

Statkraft engaged in the development of osmotic power technology in 1997, and is today the most prominent developer of the osmotic power technology in a global context. The commercialisation of osmotic power is dependent on large volumes of sufficiently efficient semi-permeable membranes with high flux and salt retention. In addition to developing the technological concept and critical parts of the system, such as the membrane technology, Statkraft has also identified the energy potential, the financial aspects and the environmental implications of the technology. Osmotic power stands out as a promising and yet unexploited, new renewable energy sources. Throughout the last years, Statkraft has been successful in its furtherance of the necessary membrane technology and has recently started the detailed planning and design of the first osmotic power prototype plant in which it will further verify and test the technology.     

CO2 Reduction to Substitute Natural Gas: Toward a Global Low Carbon Energy System

Methane has proven to be an outstanding energy carrier and is the main component of natural gas and substitute natural gas (SNG). SNG may be synthesized from the CO₂ and hydrogen available from various sources and may be introduced into the existing infrastructure used by the natural gas sector for transport and distribution to power plants, industry, and households. Renewable SNG may be generated when H₂ is produced from renewable energy sources, such as solar, wind, and hydro. In parallel, the use of CO₂-containing feed streams from fossil origin or preferably, from biomass, permits the avoidance of CO₂ emissions. In particular, the biomass-to-SNG conversion, combined with the use of renewable H₂ obtained by electrolysis, appears a promising way to reduce CO₂ emissions considerably, while avoiding energy intensive CO₂ separation from the bio feed streams. The existing technologies for the production of SNG are described in this short review, along with the need for renewed research and development efforts to improve the energy efficiency of the renewables-to-SNG conversion chain. Innovative technologies aiming at a more efficient management of the heat delivered in the exothermic methanation process are therefore highly desirable. The production of renewable SNG through the Sabatier process is a key process to the transition towards a global sustainable energy system, and is complementary to other renewable energy carriers such as methanol, dimethyl ether, formic acid, and Fischer-Tropsch fuels.     

Linking renewables and fossil fuels with carbon capture via energy storage for a sustainable energy future

Renewable energy sources and low-carbon power generation systems with carbon capture and storage (CCS) are expected to be key contributors towards the decarbonisation of the energy sector and to ensure sustainable energy supply in the future. However, the variable nature of wind and solar power generation systems may affect the operation of the electricity system grid. Deployment of energy storage is expected to increase grid stability and renewable energy utilisation. The power sector of the future, therefore, needs to seek a synergy between renewable energy sources and low-carbon fossil fuel power generation. This can be achieved via wide deployment of CCS linked with energy storage. Interestingly, recent progress in both the CCS and energy storage fields reveals that technologies such as calcium looping are technically viable and promising options in both cases. Novel integrated systems can be achieved by integrating these applications into CCS with inherent energy storage capacity, as well as linking other CCS technologies with renewable energy sources via energy storage technologies, which will maximise the profit from electricity production, mitigate efficiency and economic penalties related to CCS, and improve renewable energy utilisation.     

Ammoniaksynthese als Beispiel einer stofflichen Nutzung von intermittierend erzeugtem Wasserstoff

Producing hydrogen‐rich chemicals, such as methane, ammonia or methanol, from renewable energy may foster the integration of renewables into the current energy system. Here, a flexible ammonia synthesis concept is introduced, which is then compared to the widely discussed power‐to‐gas concepts on a technical and economic level. The current ammonia prices result in comparably high hydrogen‐specific revenues, which imply the ability to operate the system more profitable under fluctuating electricity prices and thereby increase the plant capacity factor.     

Carbon capture from stationary power generation sources: A review of the current status of the technologies

The world will need greatly increased energy supply in the future for sustained economic growth, but the related CO₂ emissions and the resulting climate changes are becoming major concerns. CO₂ is one of the most important greenhouse gases that is said to be responsible for approximately 60% of the global warming. Along with improvement of energy efficiency and increased use of renewable energy sources, carbon capture and sequestration (CCS) is expected to play a major role in curbing the greenhouse gas emissions on a global scale. This article reviews the various options and technologies for CO₂ capture, specifically for stationary power generation sources. Many options exist for carbon dioxide capture from such sources, which vary with power plant types, and include post-combustion capture, pre-combustion capture, oxy fuel combustion capture, and chemical looping combustion capture. Various carbon dioxide separation technologies can be utilized with these options, such as chemical absorption, physical absorption, adsorption, and membrane separation. Most of these capture technologies are still at early stages of development. Recent progress and remaining challenges for the various CO₂ capture options and technologies are reviewed in terms of capacity, selectivity, stability, energy requirements, etc. Hybrid and modified systems hold huge future potentials, but significant progress is required in materials synthesis and stability, and implementations of these systems on demonstration plants are needed. Improvements and progress made through applications of process systems engineering concepts and tools are highlighted and current gaps in the knowledge are also mentioned. Finally, some recommendations are made for future research directions.     

Möglichkeiten und Problemlösungen der Stromerzeugung mit Windkraftwerken

Scope and problem solutions of power generation by wind-driven plant. The importance of wind power has changed in the course of history with the advent of competing energy converters for power production from coal, oil, and nuclear energy. The known physical laws of aerodynamics and geographical location ascribe wind power a market share of no more than a few percent of power generation. Among the many designs of wind turbines, only 2- and 3-blade propeller turbines have been produced in large quantities with power ratings up to ca. 4 MW. Market developments have so far been determined by government funding. The power generation costs of 0.25 to 0.30 DM/kWh are still too high by a factor of 2 to 3. With regard to future developments it remains to be seen whether the use of more sophisticated generator systems will permit the expected large savings on the mechanical side and thus open the path to economic large production runs also in the case of medium and large-scale units.     

Combined Decarbonization of Electrical Energy Generation and Production of Synthetic Fuels by Renewable Energies and Fossil Fuels

Power generation from renewable energy sources and fossil fuels are integrated into one system. A combination of technologies in the form of a carbon capture utilization (CCU)-combined power station is proposed. The technology is based on energy generation from fossil fuels by a coal power plant with CO₂ recovery from exhaust gases, and pyrolysis of natural gas to hydrogen and carbon, completed by reverse water-gas shift for the conversion of CO₂ to CO, which will react with hydrogen in a Fischer-Tropsch synthesis for synthetic diesel. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered. This technology offers significant CO₂ savings compared to the current state of technology and makes an environmentally friendly use of fossil fuels for electricity and fuel sectors possible.     

Techno-economic assessment of pulverized coal boilers and IGCC power plants with CO<Subscript>2</Subscript> capture

The current studies on power plant technologies suggest that Integrated Gasification Combined Cycle (IGCC) systems are an effective and economic CO₂ capture technology pathway. In addition, the system in conventional configuration has the advantage of being more “CO₂ capture ready” than other technologies. Pulverized coal boilers (PC) have, however, proven high technical performance attributes and are economically often most practical technologies. To highlight the pros and cons of both technologies in connection with an integrated CO₂ capture, a comparative analysis of ultrasupercritical PC and IGCC is carried out in this paper. The technical design, the mass and energy balance and the system optimizations are implemented by using the ECLIPSE chemical plant simulation software package. Built upon these technologies, the CO₂ capture facilities are incorporated within the system. The most appropriate CO₂ capture systems for the PC system selected for this work are the oxy-fuel system and the postcombustion scheme using Monoethanolamine solvent scrubber column (MEA). The IGCC systems are designed in two configurations: Water gas shift reactor and Selexol-based separation. Both options generate CO₂-rich and hydrogen rich-gas streams. Following the comparative analysis of the technical performance attributes of the above cycles, the economic assessment is carried out using the economic toolbox of ECLIPSE is seamlessly connected to the results of the mass and energy balance as well as the utility usages. The total cost assessment is implemented according to the step-count exponential costing method using the dominant factors and/or a combination of parameters. Subsequently, based on a set of assumptions, the net present value estimation is implemented to calculate the breakeven electricity selling prices and the CO₂ avoidance cost.     

Plant for the production of activated carbon and electric power from the gases originated in gasification processes

The development of the countries involves a high energy demand; however, the energetic resources used by the moment are not renewable. Events like the energetic crisis of 1973, the continuous geopolitic clashes in energetic resource-rich areas, and the global environmental deterioration as a consequence of the industrial activity taking place in last century, make obvious the need of searching new sources of energy [1].One of these sources is the obtainment of energy from biomass exploitation. The use of this raw material involves advantages in the emission of low quantities of contaminants to the atmosphere and its renewable character. Until now, the main drawback of this source is its lack of viability when trying to obtain electric power from biomass, due to the use of systems composed of a boiler and a steam turbine (which offer low operative flexibility), which are not rentable in such a competitive market as it is, currently, the energetic one. Nowadays, the use of internal combustion engines, combined with biomass gasifiers, allows rapid connection–disconnection of the plant (aproximately of five minutes), which confers a big flexibility to the system and, as a consequence, a better exploitation of the plant in maximum energetic consumption hours. It also has the advantage of establishing a co-generation system since the gases are generated at a high temperature, 800 °C [2].With this view, the aim of this work has focused in the re-design of a gasification plant for the production of activated carbons, from biomassic residues, for the energetic exploitation of the combustible gases produced during the pyrolytic process (H₂, CO, CH₄, C₂H₂, C₂H₄, C₂H₆), since these gases are currently burnt in a torch in the plant. The idea of designing the activated carbon production plant arose from the need of managing the biomass residues (olive wastes) generated by the firm Euroliva-Azeites e Oleos Alimentares SA, located in Alto Alentejo, in the city of de Vale do Peso, Concelho de Crato. This firm collects the residues produced in the olive oil mill of Concelho do Crato and then, in the plant, makes the last obtainment of less-quality olive oil, which gives rise to a high production of olive waste. The production of this residue is 250 tons/day, which involves an annual production of 87,500 tons of residues that have to be removed [3]. The activated carbon production plant, already built, has a processing capacity of 250 kg h^− 1 of residual biomass, with a yield close to 16% in carbon production. According to the plant capacity and the generated gases potential, a thermal power of 1.05 MW and, considering a process global output of 25%, an electric power of 250 kW would be obtained.     

Transient Effects during Dynamic Operation of a Wall‐Cooled Fixed‐Bed Reactor for CO2 Methanation

The power‐to‐gas process is an option to transform fluctuating renewable electric energy into methane via water electrolysis and subsequent conversion of H₂ by methanation with CO₂. The dynamic behavior of the methanation reactor may then be a critical aspect. The kinetics of CO₂ methanation on a Ni‐catalyst were determined under isothermal and stationary conditions. Transient isothermal kinetic experiments showed a fast response of the rate on step changes of the concentrations of H₂, CO₂; in case of H₂O, the response was delayed. Non‐isothermal experiments were conducted in a wall‐cooled fixed‐bed reactor. Temperature profiles were measured and the effect of a changing volumetric flow was studied. The experimental data were compared with simulations by a transient reactor model.     

Redox Flow Batteries: Stationary Energy Storages with Potential

On the way to a secure, economic, and environmentally compatible future of energy supply, the share of renewable energies will rise strongly as part of the energy transition. To ensure a constant and resilient energy supply, despite the fluctuations of renewable energies, efficient energy storage systems are crucial. One of the most promising technologies are redox flow batteries. They are of particular importance in the field of stationary applications, due to their flexible and independent scalability of capacity and power output as well as their high cycle stability, calendric service life, and operational safety.     

Techno-economic study of CO2 capture and storage in coal fired oxygen fed entrained flow IGCC power plants

The attractiveness of fossil fuel as a feedstock for power generation depends on the development of energy conversion systems that are efficient, clean and economical. Coal fired power plants are generally considered to be “dirty” since they have high CO₂ emissions, with the exception of those coal fired power plants that employ CO₂ capture technology. Among the coal fired options, Integrated Gasification Combined Cycle (IGCC) systems have the best environmental performance and are potentially suitable candidates. The objective of this work is to provide an assessment and analysis of the potential for reduction of the output of greenhouse gas from the oxygen fed entrained flow gasifier systems, including the cost and cost-effectiveness of each likely conceptual scheme.     

Slurry Phase Hydrogenation of CO2 to Methanol Using Supported In2O3 Catalysts as Promising Approach for Chemical Energy Storage

A promising approach for chemical energy storage from fluctuating renewable electricity is methanol synthesis from CO₂ and hydrogen in a slurry reactor concept, due to efficient heat storage and easy reactor control. In combination with a promising In₂O₃/ZrO₂ catalyst and mineral oil as carrier liquid, efficient methanol production under a wide range of changing process conditions is shown for the first time. A maximum methanol productivity of 2.1 g_MeOHg_In⁻¹h⁻¹ and multiple recycling stability of the catalyst and the carrier liquid was achieved, showing no significant decrease in methanol yields.     

Flexible and economical operation of chlor-alkali process with subsequent polyvinyl chloride production

Demand response (DR) can compensate for imbalances in variable renewable energy supplies. This possibility is particularly interesting for electrochemical processes, due to their high energy intensity. To determine the technical feasibility and economic viability of DR, we chose the chlor-alkali process with subsequent polyvinyl chloride production, including intermediate storage for ethylene dichloride. We estimate the maximum possible cost savings of implementing load flexibility measures. A process model is set up to determine the system characteristic. Subsequent optimizations result in the facility's best possible dispatch depending on additional and minimum power load, storage volume, and cost of a load change. Real plant data are used to specify model parameters and validate the system characteristic and the plant dispatch. An economic evaluation reveals the economic advantages of efficiency and flexibility. The approach can be used to analyze the DR potential of other chlorine value chains or facilities with high electricity demand in general.     

Evaluation of strategies for the subsequent use of CO<Subscript>2</Subscript>

If substantial amounts of CO₂, which according to actual scenarios may in the future be captured from industrial processes and power generation, shall be utilized effectively, scalable energy efficient technologies will be required. Thus, a survey was performed to assess a large variety of applications utilizing CO₂ chemically (e.g., production of synthesis-gas, methanol synthesis), biologically (e.g., CO₂ as fertilizer in green houses, production of algae), or physically (enhancement of fossil fuel recovery, use as refrigerant). For each of the processes, material and energy balances were set up. Starting with pure CO₂ at standard conditions, expenditure for transport and further process specific treatment were included. Based on these calculations, the avoidance of greenhouse gas emissions by applying the discussed technologies was evaluated. Based on the currently available technologies, applications for enhanced fossil fuel recovery turn out to be most attractive regarding the potential of utilizing large quantities of CO₂ (total capacity > 1000 Gt CO₂) and producing significant amounts of marketable products on one hand and having good energy and material balances on the other hand \(\left( {{{t_{CO_2 - emitted} } \mathord{\left/ {\vphantom {{t_{CO_2 - emitted} } {t_{CO_2 - utilized} < 0.2 - 0.4}}} \right. \kern-\nulldelimiterspace} {t_{CO_2 - utilized} < 0.2 - 0.4}}} \right)\). Nevertheless, large scale chemical fixation of CO₂ providing valuable products like fuels is worth considering, if carbon-free energy sources are used to provide the process energy and H₂ being essential as a reactant in a lot of chemical processes (e.g., production of DME: \({{t_{CO_2 - emitted} } \mathord{\left/ {\vphantom {{t_{CO_2 - emitted} } {t_{CO_2 - utilized} > 0.34}}} \right. \kern-\nulldelimiterspace} {t_{CO_2 - utilized} > 0.34}}\)). Biological processes such as CO₂ fixation using micro-algae look attractive as long as energy and CO₂ balance are considered. However, the development of effective photo-bioreactors for growing algae with low requirements for footprint area is a challenge.     

Simulation of a Lignite‐Based Polygeneration System Coproducing Electricity and Tar with Carbon Capture

Lignite‐based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized‐bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO₂ is captured, the larger energy penalty it will cost. Therefore, a trade‐off should be made between low emissions and high efficiency.