Defining the cost of water impact for thermoelectric power generation

Thermal power plants use large amounts of water, mainly for cooling purposes. Over a long operational period, power-plant cooling can have a large impact on the water source: elevated temperatures of return flows alter the local physical and chemical properties of the water (i.e., quality impact), while water consumption reduces the available water reserves for future and down-stream uses (i.e., Quantity impact). The vulnerability of the energy sector to water availability is an important problem and measures to confront or mitigate this challenge have not yet been adopted. Here, a novel, straightforward methodology to calculate the cost of water impact caused by coal and natural-gas (combined-cycle) plants with once-through and wet-recirculating cooling systems is developed. The goal is to internalize systemic costs related to water use impacts and thereby incentivize more sustainable energy generation practices. The impact is calculated here as a theoretical feedback on the plant's operational costs, since altered water properties will eventually lead to malfunction or part-load operation. The main parameter affecting the cost of water impact is found to be the temperature rise of the cooling water in the condenser. In plants with once-through cooling systems, the quantity and quality impacts of water use are of a comparable magnitude. The cost of water impacts in facilities with wet-recirculating cooling systems, on the other hand, is determined only by their quantity impact on water resources. Overall, recirculating systems result in a significantly lower water cost when compared to once-through systems. Furthermore, an approximately three times higher cost of water impact is calculated for coal plants in comparison to natural gas plants, which clearly demonstrates the importance of operational efficiency on the water use of power plants.Fontina Petrakopoulou would like to thank the Spanish Min- istry of Science, Innovation and Universities and the Universi- dad Carlos III de Madrid (Ramón y Cajal Programme, RYC-2016- 20971)

On the economics of stand-alone renewable hybrid power plants in remote regions

In recent years ever more examples of regions that have managed to achieve or orientate themselves toward renewable energy sufficiency are emerging. However, actions to create energy autonomy are mainly the result of isolated activities and they are less driven from fully organized movements. In addition, total energy independence without the support of a centralized electrical grid is yet to be achieved. The objectives of this work are to investigate the associated costs of stand-alone renewable hybrid power plants on a Greek island and compare them to the cost of the currently used fossil-fuel-based conventional plant. The plants examined here are designed to fully cover the electricity needs of the island. Islands may face numerous energy problems and rely heavily on foreign and environmentally-harmful fuels. It is shown that the relatively high cost of electricity of such a remote region can increase the competitiveness and promote the wider incorporation of technologies based on renewable energy sources that may, in other cases, seem economically inferior to business-as-usual energy solutions.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) the Ministerio de Educación, cultura y Deporte (CEI-15-17) and Banco Santande

The Social Perspective on the Renewable Energy Autonomy of Geographically Isolated Communities: Evidence from a Mediterranean Island

The use of renewable energy sources can provide a path toward sustainable developmentand regional energy independence. In particular, renewable-based energy autonomy constitutes aviable option in remote areas. This work presents a survey on the use of renewable energy as part of anenergy autonomy plan on a Mediterranean island. The study also included personal communicationswith residents and local community leaders. The results show an overall positive attitude towardrenewable energy applications. The majority of the respondents support the implementation ofrenewable-based, small-scale projects corresponding to local energy autonomy scenarios. They are,furthermore, convinced that a wider use of renewable technologies can reduce the environmentalimpact of conventional fuels. However, although people are aware of technologies widely used onthe island, they are much less so when it comes to less prominent technologies (wave energy, fuelcells, etc.). People tend to be more open to installations of solar, wind and geothermal energy, whilegenerally they dislike nuclear and coal power plants. Lastly, the majority of the respondents believethat local policies on energy issues should change, while they also perceive the lack of political willas one of the most important obstacles to the implementation of renewable technologies

Economic and Environmental Considerations for Zero-emission Transport and Thermal Energy Generation on an Energy Autonomous Island

The high cost and environmental impact of fossil-fuel energy generation in remote regions can make renewable energy applications more competitive than business-as-usual scenarios. Furthermore, energy and transport are two of the main sectors that significantly contribute to global greenhouse gas emissions. This paper focuses on the generation of thermal energy and the transport sector of a fossil fuel-based energy independent island in Greece. We evaluate (1) technologies for fully renewable thermal energy generation using building-specific solar thermal systems and (2) the replacement of the vehicle fleet of the island with electric and hydrogen-fueled vehicles. The analysis, based on economic and environmental criteria, shows that although solar thermal decreases greenhouse gases by 83%, when compared to the current diesel-based situation, it only becomes economically attractive with subsidy scenarios equal to or higher than 50%. However, in the transport sector, the sum of fuel and maintenance costs of fuel-cell and electric vehicles is found to be 45% lower than that of the current fleet, due to their approximately seven times lower fuel cost. Lastly, it will take approximately six years of use of the new vehicles to balance out the emissions of their manufacturing phase.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) the Ministerio de Educación, cultura y Deporte (CEI-15-17) and Banco Santander

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

Sustainable Water Generation on a Mediterranean Island in Greece

Population growth, increasing droughts, and high irrigation needs are all factors that create freshwater shortage problems on islands. The pressing needs of remote islands usually call for water transport from the mainland or other neighboring islands, at a high cost. This study evaluates the design and economic viability of an alternative, sustainable water supply network onthe Mediterranean island of Skyros in Greece. The proposed water supply system provides the island with potable water from desalination units, as well as water for agricultural use from a wastewater treatment plant. The total investment cost of the project is found to be Euros9.8 million, accounting forthe cost of transportation of the water between the different settlements (installation, operations, and maintenance), as well as for the required energy of the involved methods. It is found that 44% of the expenses are related to the transport of potable and residual water, and 52% of the cost corresponds to the production of the required desalinated water. As part of a sustainable water and energy network, all energy needs of water generation are assumed to be covered by a renewable power plant. The total cost of water generation on the island with the proposed system is estimated at 2.49 Euros/m3, constituting a competitive and more sustainable solution, when compared to current practices.Fontina Petrakopoulou is funded by the Ramón y Cajal Programme of the Spanish Ministry of Science, Innovation and Universities (Grant no. RYC-2016-20971)

Exergetic analysis and dynamic simulation of a solar-wind power plant with electricity storage and hydrogen generation

The ambitious vision of off-grid renewable energy autonomy of remote regions has yet to come to fruition. The development of comprehensive energy production systems would be needed to achieve such a goal. This study consists of the simulation and exergetic evaluation of a novel hybrid power plant for stand-alone operation aiming to provide electricity autonomy of a Mediterranean island. The considered power plant is simulated dynamically over an annual cycle and accounts for both energy input fluctuations and electricity surplus. The plant combines a photovoltaic array with wind turbines for energy input, coupled with electricity storage and a hydrogen generation facility to stabilize the power output of the plant. Unlike other similar studies, the energy system presented here relies on real-case weather and demand data of a relatively large remote community and is optimized to ensure continuous operation even under extreme conditions. It is seen that this stand-alone hybrid power plant constitutes a robust and secure alternative to the current conventional energy situation; the combined renewable technologies succeed in complementing each other and offer stable performance throughout the year without the requirement of additional support by fossil fuels. The mean annual exergetic efficiency of the plant is found to be 17.9%, producing approximately 25,000 MWh of electricity per year, along with a secondary product (hydrogen) produced in the electrolyzer of the plant. Although this additional product is associated with additional investment cost, it offers the possibility to stabilize the power plant's performance and can be used as an additional source of financial income for the community. (C) 2015 Elsevier Ltd. All rights reserved.The authors would like to acknowledge the Marie Curie Actions PEOPLE-2012 IEFGENERGIS- 332028 and COFUND CONEX funded by FP7

Der Einfluss der Immunsuppression auf den funktionellen und morphologischen Koronarstatus nach orthotoper Herztransplantation

Hintergrund Die Transplantatvaskulopathie stellt eine wesentliche Ursache der Spätmorbidität und Mortalität für Patienten nach Herztransplantation dar. Durch das diffuse Befallmuster wird die Erkrankung mit Hilfe der Koronarangiographie erst in einem fortgeschrittenen Stadium erkannt. Die pathophysiologische Bedeutung der immunsuppressiven Therapie für die Entwicklung der Transplantatvaskulopathie nach Herztransplantation wird kontrovers beurteilt. Das Ziel der vorliegenden Arbeit war es, den Einfluss von zwei unterschiedlichen immunsuppressiven Regimen auf den morphologischen und funktionellen Koronarstatus zu untersuchen. Im Rahmen einer randomisierten und prospektiven Studie untersuchten wir die Veränderung des Koronarstatus bei 44 Patienten (8 weiblich, 36 männlich) im ersten Jahr nach der Herztransplantation. Verglichen wurde eine Gruppe, mit der immunsuppresiven Kombination TAC und MMF, mit einer zweiten Gruppe unter CYA und MMF. In der frühen postoperativen Phase, bis zu 6 Monaten, wurden zusätzlich Kortikoide verabreicht. Methoden In beiden Immunsuppressions-Gruppen wurde die epikardiale und mikrovaskuläre Endothel- und glatte Muskelzellfunktion, sowie die koronare Intimaverdickung 1 Monat und 1 Jahr nach der Herztransplantation bestimmt. Es sollte ermittelt werden, ob das Ausmaß der funktionellen und strukturellen Gefäßveränderungen bzw. die Progression derselben zwischen CYA und TAC-Patientengruppe unterschiedlich ist. Die endothelunabhängigen Substanzen Adenosin und Nifedipin sowie die endothel-unabhängige Substanz Acetylcholin wurden in die linke Koronararterie appliziert. Darauffolgend wurde die epikardiale Weitenänderung des Ramus interventricularis anterior an proximalen und distalen Abschnitten mittels quantitativer Koronarangiographie bestimmt. Die Änderung der koronaren Flussgeschwindigkeit (als Ausdruck der mikrovaskulären Vasoreagibilität) wurde parallel mit Hilfe eines Dopplerdrahtes in der linken Koronararterie fortlaufend gemessen. Zur frühzeitigen Erkennung der koronaren Intimaproliferation bzw. des vaskulären Remodelings erfolgte abschließend eine Untersuchung mit Hilfe des intravaskulären Ultraschalls im Ramus interventricularis anterior bzw. im Ramus circumflexus. Intimafläche, Gefäßfläche und Gefäßokklusion wurden als Parameter für strukturelle Koronargefäßveränderungen ausgewertet. Systemische Endothelin-Konzentrationen wurden mittels Radioimmunoassay nach einem und zwölf Monate nach der Transplantation bestimmt. Ergebnisse Es ergab sich ein Anstieg der mittleren Intimafläche ohne kompensatorisches vaskuläres Remodeling in der Follow-Up-Untersuchung, assoziiert mit einer signifikanten Reduktion der endothelabhängigen koronaren Flussreserve und einer (kompensatorisch) verbesserten endothelunabhängigen epikardialen Gefäßreagibilität auf Nifedipin in der CYA-Gruppe. In der TAC-Gruppe zeigte sich eine tendenzielle Zunahme der mittleren Intimafläche in der Follow-Up-Untersuchung bei gleichzeitig signifikantem Anstieg der mittleren gesamten Gefäßquerschnittfläche als Ausdruck eines positiven koronaren Remodelings. Es ergaben sich keine Unterschiede in der endothelabhängigen epikardialen Vasomotorik und in der endothelunabhängigen mikrovaskulären Vasoreagibilität im Zeitverlauf zwischen den Patienten mit TAC und CYA. Assoziiert mit den unter TAC verbesserten funktionellen und morphologischen Koronarparametern zeigte sich in der TAC-Gruppe eine signifikante Verminderung der zirkulierenden Endothelin-1 Konzentrationen im Jahresverlauf. In der CYA-Patientengruppe wurden nach einem Jahr unverändert hohe Endothelin-1-Konzentrationen gemessen. Schlussfolgerung Die Immunsuppression mit TAC und MMF scheint der mit CYA und MMF bezüglich der koronaren Gefäßokklusion und der mikrovaskulären Endothelfunktion überlegen zu sein. Pathogenetisch erscheint eine in der TAC-Gruppe verminderte Endothelin-1-Konzentration von Bedeutung zu sein. Bezüglich der epikardialen endothelabhängigen Vasomotion scheint keines der beiden immunsuppressiven Regime einen Vorteil zu haben. Weitergehende Nachbeobachtungen sind notwendig um den langfristigen Nutzen einer Immunsuppression mit TAC und Mykophenolat Mofetil für zukünftige kardiovaskuläre Ereignisse zu bestimmen