Suchergebnisse

The synthesis of energy systems is a two-stage optimization problem where design decisions have to be implemented here-and-now (first stage), while for the operation of installed components, we can wait-and-see (second stage). To identify a sustainable design, we need to account for both economical and environmental criteria leading to multi-objective optimization problems. However, multi-objective optimization does not lead to one optimal design but to multiple Pareto-efficient design options in general. Thus, the decision maker usually has to decide manually which design should finally be implemented. In this paper, we propose the flexible here-and-now decision (flex-hand) approach for automatic identification of one single design for multi-objective optimization. The approach minimizes the distance of the Pareto front based on one fixed design to the Pareto front allowing multiple designs. Uncertainty regarding parameters of future operations can be easily included through a robust extension of the flex-hand approach. Results of a real-world case study show that the obtained design is highly flexible to adapt operation to the considered objective functions. Thus, the design provides an energy system with the ability to adapt to a changing focus in decision criteria, e.g., due to changing political aims. ; ISSN:1389-4420 ; ISSN:1573-2924

The synthesis of energy systems is a two-stage optimization problem where design decisions have to be implemented here-and-now (first stage), while for the operation of installed components, we can wait-and-see (second stage). To identify a sustainable design, we need to account for both economical and environmental criteria leading to multi-objective optimization problems. However, multi-objective optimization does not lead to one optimal design but to multiple Pareto-efficient design options in general. Thus, the decision maker usually has to decide manually which design should finally be implemented. In this paper, we propose the flexible here-and-now decision (flex-hand) approach for automatic identification of one single design for multi-objective optimization. The approach minimizes the distance of the Pareto front based on one fixed design to the Pareto front allowing multiple designs. Uncertainty regarding parameters of future operations can be easily included through a robust extension of the flex-hand approach. Results of a real-world case study show that the obtained design is highly flexible to adapt operation to the considered objective functions. Thus, the design provides an energy system with the ability to adapt to a changing focus in decision criteria, e.g., due to changing political aims.

The synthesis of energy systems is a two-stage optimization problem where design decisions have to be implemented here-and-now (first stage), while for the operation of installed components, we can wait-and-see (second stage). To identify a sustainable design, we need to account for both economical and environmental criteria leading to multi-objective optimization problems. However, multi-objective optimization leads not to one optimal design but to multiple Pareto-efficient design options in general. Thus, the decision maker usually has to decide manually which design should finally be implemented. In this paper, we propose the flexible here-and-now decision (flex-hand) approach for automatic identification of one single design for multi-objective optimization. The approach minimizes the distance of the Pareto front based on one fixed design to the Pareto front allowing multiple designs. Uncertainty regarding parameters of future operations can be easily included through a robust extension of the flex-hand approach. Results of a real-world case study show that the obtained design is highly flexible to adapt operation to the considered objective functions. Thus, the design provides an energy system with the ability to adapt to a changing focus in decision criteria, e. g., due to changing political aims.

The combustion of fossil fuels within the transportation sector is a key driver of global warming (GW) and leads to harmful emissions of nitrogen oxides (NOx) and particulates (soot). To reduce these negative impacts of the transportation sector, synthetic fuels are currently being developed, which are produced from renewable energy stored via catalytic conversion of hydrogen (H2) and carbon dioxide (CO2). A promising class of synthetic fuels are oxymethylene ethers (OMEs). This study conducts a prospective environmental assessment of an OME-based fuel using Life Cycle Assessment (LCA). We investigate an OME1-diesel-blend (OME1-blend), where OME1 replaces 24 mass% of diesel fuel. Such an OME1-blend could be a first step towards an OME transition. For the production of OME1 from CO2-based methanol, we consider both the established route via condensation with formaldehyde and a novel direct pathway based on catalytic combination with CO2 and hydrogen. To close the carbon loop, CO2 supply via biogas and direct air capture is considered. In a best-case scenario, hydrogen is produced by water electrolysis using electricity from wind power in the European Union as an input. The direct pathway reduces the required process steps from three to two and is shown to allow for an improved utilization of the energy provided by hydrogen: the exergy efficiency is increased from 74% to 86%. For combustion, we conducted experiments in a single cylinder engine to determine the full spectrum of engine-related emissions. The engine data provide the input for simulations of the cumulative raw emissions over the Worldwide Harmonized Light Vehicles Test Procedures (WLTP) cycle for a mid-size passenger vehicle. Our well-to-wheel LCA shows that OME1 has the potential to serve as an almost carbon-neutral blending component: replacing 24 mass% of diesel by OME1 could reduce the GW impact by 22% and the emissions of NOx and soot even by 43% and 75%, respectively. The key to achieving these benefits is the integration of renewable energy in hydrogen production. The cumulative energy demand (CED) over the life cycle is doubled compared to fossil diesel. With sufficient renewable electricity available, OME1-blends may serve as a promising first step towards a more sustainable transportation sector. ; ISSN:1754-5692 ; ISSN:1754-5706

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade. ; ISSN:1754-5692 ; ISSN:1754-5706

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we capitalise on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the largescale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.