Advanced exergoeconomic analysis of a power plant with CO2 capture

Conventional exergy-based analyses reveal options for improving energy conversion systems, but they suffer from some limitations that are addressed by advanced exergy-based analyses. Advanced exergy-based methods are capable of (1) identifying interdependencies among plant components (endogenous / exogenous values), and (2) revealing the potential for improvement (avoidable / unavoidable values). Thus, data obtained from these methods pinpoint strengths and weaknesses of energy conversion systems and are of great importance when complex plants with a large number of interconnected components are considered. This paper presents one of the first applications of an advanced exergoeconomic analysis to a complex power plant. The plant includes a mixed conducting membrane for oxy-fuel combustion and CO2 capture. The results show that for the most influential components of the plant, the largest part of investment cost and of the costs of exergy destruction is unavoidable. Additionally, in most cases the interactions among the components are of lower importance and, for the majority of the components, the endogenous parts of the costs (related to the internal operation of each component) are significantly larger than the corresponding exogenous parts (related to component interactions). Nevertheless, relatively strong interactions have been found among the components that constitute the mixed conducting membrane reactor of the plant.EC/FP7/332028/EU/Green Energy for Islands/GENERGI

Advanced exergoeconomic analysis of a power plant with CO2 capture

Conventional exergy-based analyses reveal options for improving energy conversion systems, but they suffer from some limitations that are addressed by advanced exergy-based analyses. Advanced exergy-based methods are capable of (1) identifying interdependencies among plant components (endogenous / exogenous values), and (2) revealing the potential for improvement (avoidable / unavoidable values). Thus, data obtained from these methods pinpoint strengths and weaknesses of energy conversion systems and are of great importance when complex plants with a large number of interconnected components are considered. This paper presents one of the first applications of an advanced exergoeconomic analysis to a complex power plant. The plant includes a mixed conducting membrane for oxy-fuel combustion and CO2 capture. The results show that for the most influential components of the plant, the largest part of investment cost and of the costs of exergy destruction is unavoidable. Additionally, in most cases the interactions among the components are of lower importance and, for the majority of the components, the endogenous parts of the costs (related to the internal operation of each component) are significantly larger than the corresponding exogenous parts (related to component interactions). Nevertheless, relatively strong interactions have been found among the components that constitute the mixed conducting membrane reactor of the plant.EC/FP7/332028/EU/Green Energy for Islands/GENERGI

Vergleichende Bewertung von Kraftwerken mit CO2-Abscheidung: Thermodynamische, wirtschaftliche und ökologische Performance

CCS (CO2-Abscheidung und –Speicherung) wird im Energiesektor als Brückentechnologie zur Reduzierung des Ausstoßes von anthropogenem CO2 angesehen, welches einen ständig wachsenden Einfluss auf Klima und Umwelt hat. In dieser Dissertation werden acht Kraftwerkskonzepte mit Abscheidetechnologien im Hinblick auf ihre Effizienz, ihre Wirtschaftlichkeit sowie ihren ökologischen Fußabdruck untersucht. Es werden hier exergiebasierte Methoden benutzt, um die untersuchte Kraftwerkskonzepte mit einem Referenzkraftwerk ohne CO2-Abscheidung zu vergleichen. Während konventionelle Exergieanalysen bereits wichtige Hinweise auf effizienzverbessernde Maßnahmen liefern können, ist es hilfreich, zusätzliche Informationen über die einzelnen Kraftwerkkomponenten und ihre Wechselwirkungen zu erhalten. Diese Überlegung führte zu der Entwicklung von erweiterten exergiebasierten Methoden, in denen die Exergievernichtung und auch die damit verbundenen Kosten und Umweltauswirkungen aufgeteilt werden in vermeidbar/unvermeidbar und in endogen/exogen. Das eigentliche Verbesserungspotential der Anlage wird deutlich, wenn man den vermeidbaren Anteil der Exergievernichtung und der Kosten betrachtet. Die Aufteilung in einen endogenen und einen exogenen Anteil der Exergievernichtung liefert die Wechselwirkungsbeziehungen zwischen den einzelnen Komponenten der Anlage. Die effizientesten der untersuchten Kraftwerke mit CO2-Abscheidung sind die Oxyfuel-Kraftwerke. Eine exergoökonomische Untersuchung zeigt einen minimalen Anstieg der relativen Investitionskosten (in €/kW) von 80% für die konventionelle Abscheidemethode der chemischen Absorption und einen Anstieg von 86% für das Oxyfuel-Kraftwerk mit chemical looping combustion. Das Oxyfuel-Kraftwerk hat einen reduzierten Umwelteinfluss im Vergleich zu dem Kraftwerk ohne CO2-Abscheidung, während sich der Umwelteinfluss bei chemischer Absorption erhöht. Akzeptiert man alle hier zugrunde gelegten Annahmen und Daten zur Berechnung des Umwelteinflusses, so zeigt sich, dass eine Effizienzsteigerung in den Kraftwerken ein größeres Potential für die Verringerung des ökologischen Fußabdrucks der Kraftwerke besitzt als die CO2-Abscheidung. Mit fortschrittlichen exergiebasierten Methoden erkennt man die Wechselwirkungen der einzelnen Kraftwerkskomponenten in der Anlage, und das wirklich vorhandene Potential für kosten- und umweltbezogenen Verbesserungen wird deutlich. Generell wurden die größten thermodynamischen Ineffizienzen im Inneren der einzelnen Komponenten erzeugt. Außerdem wiesen Komponenten mit hohen Kosten und Umweltauswirkungen nur einen geringen Anteil an vermeidbarer Exergievernichtung auf. Dies bedeutet, dass es nur begrenzte Möglichkeiten zur Steigerung der Effizienz und zur Verringerung der Umweltbelastung gibt.CCS (Carbon Capture and Sequestration) in the energy sector is seen as a bridge technology for CO2 mitigation, due to the ever-growing environmental impact of anthropogenic-emitted greenhouse gases. In this work, eight power plant concepts using CO2 capture technologies are assessed based on their efficiency, economic feasibility and environmental footprint. Exergy-based analyses are used for evaluating the considered power plants through comparison with a reference plant without CO2 capture. While conventional exergy-based analyses provide important information that can lead to improvements in plant performance, additional insight about individual components and the interactions among equipment can aid further assessment. This led to the development of advanced exergy-based analyses, in which the exergy destruction, as well as the associated costs and environmental impacts are split into avoidable/unavoidable and endogenous/exogenous parts. Based on the avoidable parts, the potential for improvement is revealed, while based on the endogenous/exogenous parts, the component interactions are obtained. Among the examined plants with CO2 capture, the most efficient are those working with oxy-fuel technology. An exergoeconomic analysis shows a minimum increase in the relative investment cost (in €/kW) of 80% for the conventional approach (chemical absorption) and an increase of 86% for the oxy-fuel plant with chemical looping combustion. The latter shows a somewhat decreased environmental impact when compared to that of the reference plant. On the contrary, the plant with chemical absorption results in a higher environmental penalty due to its high efficiency penalty. Therefore, accepting that all assumptions and data related to the calculations of the environmental impacts are reliable, efficiency improvement seems to be a more significant factor in potentially decreasing a plant’s environmental impact. With advanced exergy-based analyses, interdependencies among components are identified, and the real potential for cost- and environmental-related improvement is revealed. A common trend for all plants examined is that most thermodynamic inefficiencies are caused by the internal operation of the components. Additionally, avoidable quantities are generally found to be low for components with high costs and environmental impacts, leaving a relatively narrow window of improvement potential

Studying the Reduction of Water Use in Integrated Solar Combined-Cycle Plants

With vast amounts of water consumed for electricity generation and water scarcity predicted to rise in the near future, the necessity to evaluate water consumption in power plants arises. Cooling systems are the main source of water consumption in thermoelectric power plants, since water is a cooling fluid with relatively low cost and high efficiency. This study evaluates the performance of two types of power plants: a natural gas combined-cycle and an integrated solar combined-cycle. Special focus is made on the cooling system used in the plants and its characteristics, such as water consumption, related costs, and fuel requirements. Wet, dry, and hybrid cooling systems are studied for each of the power plants. While water is used as the cooling fluid to condense the steam in wet cooling, dry cooling uses air circulated by a fan. Hybrid cooling presents an alternative that combines both methods. We find that hybrid cooling has the highest investment costs as it bears the sum of the costs of both wet and dry cooling systems. However, this system produces considerable fuel savings when compared to dry cooling, and a 50% reduction in water consumption when compared to wet cooling. As expected, the wet cooling system has the highest exergetic efficiency, of 1 and 5 percentage points above that of dry cooling in the conventional combined-cycle and integrated solar combined-cycle, respectively, thus representing the lowest investment cost and highest water consumption among the three alternatives. Hybrid and dry cooling systems may be considered viable alternatives under increasing water costs, requiring better enforcement of the measures for sustainable water consumption in the energy sector

A Closer Look at the Environmental Impact of Solar and Wind Energy

Moving towards a sustainable society implies constant improvement in the way energy is supplied and consumed, with wider implementation of solar and wind energy facilities in stand-alone or hybrid configurations. The goal of this work is to evaluate the lifecycle performance (construction and operation-related impact) of large-scale solar and wind energy systems and to compare it with conventional coal and natural gas fossil fuel plants under similar conditions. Environmental analyses of energy conversion systems today usually neglect the construction-related environmental impact of fossil fuel plants, because it is significantly smaller than the impact related to the operation of the plant. However, the construction of large-scale renewable plants implies the use of rare materials, transport-related emissions, and other environmentally impactful activities. The plants evaluated here are configured and compared for similar emissions and similar power output. It is found that the life-cycle environmental impact of the renewable plants could, in some specific cases, exceed that of the fossil fuel plants. Understanding the reasons behind this and the possible limitations of the different technologies can help plan for sustainable energy systems in the future. Finally, solutions to minimize the impact of renewable energy are proposed for more environmentally friendly implementation and future research

Evaluation of the Coupling of a Hybrid Power Plant with a Water Generation System

This paper presents the design and analysis of an energy/water system that combines a 20 MW hybrid concentrated solar/biomass power plant with an advanced wastewater treatment facility. Designed to be installed in one of the most demanding areas of the Iberian Peninsula, the Spanish region of Andalusia, this plant seeks to provide the area with potable water and electricity. The solar block works with a mixture of molten salts, while the biomass backup system of the power plant uses olive pomace. The implementation of a direct potable reuse facility further enhances the sustainability of the project. Urban sewage from the region is collected and passed through a series of purification procedures in order to generate potable water ready to be directly blended into the water distribution system. A sensitivity analysis is conducted to determine the feasibility of the co-generation of electricity and water in the area. With a capacity factor of 85% and an annual operation of 7,446 hours, the hybrid solar/biomass power plant generates 148.92 GWh. Exergetic analyses have been realized for two extreme cases: exclusive use of the solar block and exclusive use of the biomass system. An overall plant exergetic efficiency of 15% is found when the solar block is used and an efficiency of 34% is calculated when the biomass support system is used. Following an economic analysis, a total investment of 211,526,000 € is required for the full implementation of the system with a resulting levelized cost of energy of 0.25 €/kWh. We find that the selling price of the generated potable water which makes the plant operation economically viable is found to be 14.61 €/m3. At present, this price seems relatively high in view of current conditions; yet it is expected to become more realistic under future heightened water scarcity conditions, especially in arid regions

Simulation and evaluation of a hybrid concentrating-solar and wind power plant for energy autonomy on islands

Renewable energy sources can offer isolated communities the opportunity to regulate their energy use in a manner that best suits their needs. This paper presents the simulation and thermodynamic evaluation of a stand-alone hybrid power plant exclusively using renewable energy sources and storage technologies for the energy autonomy of a Mediterranean island. The study assumes stand-alone dynamic operation and investigates the sustainable and robust energy independence of the community under consideration, a remote area not connected to a centralized electrical grid. The analysis shows that the evaluated hybrid concentrating solar-wind power plant is a reliable alternative for satisfying the fluctuating electricity demand of the island. The plant achieves stable and controlled autonomous performance using the complementary character of solar and wind energy, combined with energy storage.Fontina Petrakopoulou would like to thank the Universidad Carlos III de Madrid, the European Union's Seventh Framework Programme for research, technological development and demonstration (grant agreements nº 600371 and 332028), the Ministerio de Economía y Competitividad (COFUND2014-51509) and Banco Santander.Peer reviewe