1,720,963 research outputs found
ANALYSIS OF A COMBINED CYCLE EXPLOITING INLET CONDITIONING TECHNOLOGIES FOR POWER MODULATION
No full textThe high share of non-dispatchable renewable energy source generators in the electrical grid has increased the need for flexibility of Gas Turbine Combined Cycles (GTCC) already installed. To maximize not only the maximum power produced, via Power Augmentation Technologies (PATs), but also to reduce the Minimum Environmental Load (MEL), both OEMs and GTCC owners have adopted several technical solutions. This kind of flexibility has become, year-by-year, ever more crucial to guarantee GTCC economical sustainability. Amongst the solutions which can be adapted to guarantee GTCC flexibility, the Inlet Conditioning System is a particularly interesting technical solution, which can be installed without restrictions related to the different GT design.In this paper, an evaluation of the compressor inlet temperature effect over the Combined Cycle performance is presented, with a focus on the bottoming Cycle impact. Different Inlet Conditioning Strategies are then compared considering the energy, and the environmental impact on GTCC behavior. The performance of a layout including a Thermal Energy Storage (TES) and a Heat Pump (HP) is then evaluated and compared to other technical solutions
Techno-Economic Assessment of CO2-Based Power to Heat to Power Systems for Industrial Applications
No full textThe industrial sector is a major source of wealth, producing about one-quarter of the global gross product. However, industry is also a major emitter of CO2 and it represents a key challenge toward achieving the worldwide CO2 emission reduction targets. Nowadays, about 22% of the overall energy demand is heating for the industrial sector, generating about 40% of the global CO2 emissions. Additionally, 30% of the final energy demand of the industrial sector is electricity. Solutions to decarbonize the industrial sector are needed. This work presents the techno-economic assessment of four different molten salts-based power-to-heat-to-heat and power solutions aiming at decarbonizing the industrial sector, requiring medium temperature heat. The systems are studied under different electric markets. Dispatch strategies and system sizing are identified to ensure optimal techno-economic performance. The main performance indicators investigated are the levelized cost of heat and electricity (LCoH and LCoE), the operational expenditure, and the attainable savings with respect to alternative business as usual solutions. The results highlight that the proposed system can be cost-competitive, particularly in markets characterized by low electricity prices and high daily price fluctuations, such as Finland. In these locations, LCoE as low as 100 e/MWh and LCoH lower than 55 e/MWh can be attained by the base system configuration. The introduction of high temperature heat pumps can provide further LCoH reduction of about 50%. This study sets the ground for further power-to-heat-to-heat and power techno-economic investigations addressing different industrial sectors and identifies main system design strategies
TECHNO-ECONOMIC ASSESSMENT OF CO2 BASED POWER TO HEAT TO POWER SYSTEMS FOR INDUSTRIAL APPLICATIONS
No full textThe industrial sector is a major source of wealth, producing about one-quarter of the global gross product. However, industry is also a major emitter of CO2 and it represents a key challenge towards achieving the worldwide CO2 emission reduction targets. Nowadays, about 22 % of the overall energy demand is heating for the industrial sector, generating about 40 % of the global CO2 emissions. Additionally, 30 % of the final energy demand of the industrial sector is electricity. Solutions to decarbonize the industrial sector are needed. This work presents the techno-economic assessment of four different molten salts based power-to-heat-to-heat and power solutions aiming at decarbonizing the industrial sector, requiring medium temperature heat. The systems are studied under different electric markets. Dispatch strategies and system sizing are identified to ensure optimal techno-economic performance. The main performance indicators investigated are the levelized cost of heat and electricity (LCoH and LCoE), the operational expenditure, and the attainable savings with respect to alternative business as usual solutions. The results highlight that the proposed system can be cost-competitive, particularly in markets characterized by low electricity prices and high daily price fluctuations, such as Finland. In these locations LCoE as low as 100 €/MWh and LCoH lower than 55 €/MWh can be attained by the base system configuration. The introduction of high temperature heat pumps can provide further LCoH reduction of about 50 %. This study sets the ground for further power-to-heat-to-heat and power techno-economic investigations addressing different industrial sectors and identifies main system design strategies
Ancillary services potential for flexible combined cycles
No full textCombined Cycle Gas Turbines, CCGTs, are often considered as the bridging technology to a decarbonized energy system thanks to their high exploitation rate of the fuel energetic potential. At present time in most European countries, however, revenues from the electricity market on their own are insufficient to operate existing CCGTs profitably, also discouraging new investments and compromising the future of the technology. In addition to their high efficiency, CCGTs offer ancillary services in support of the operation of the grid such as spinning reserve and frequency control, thus any potential risk of plant decommissioning or reduced investments could translate into a risk for the well-functioning of the network. To ensure the reliability of the electricity system in a transition towards a higher share of renewables, the economic sustainability of CCGTs must be preserved, for which it becomes relevant to monetize properly the ancillary services provided. In this paper, an accurate statistical analysis was performed on the day-Ahead, intra-day, ancillary service, and balancing markets for the whole Italian power-oriented CCGT fleet. The profitability of 45 real production units, spread among 6 market zones, was assessed on an hourly basis considering local temperature, specific plant layouts, and off-design performance. The assessment revealed that net income from the ancillary service market doubled, on average, the one from the day-Ahead energy market. It was observed that to be competitive in the ancillary services market CCGTs are required to be more flexible in terms of ramp rates, minimum environmental loads, and partial load efficiencies. This paper explores how integrating a Heat Pump and a Thermal Energy Storage within a CCGT could allow improving its competitiveness in the ancillary services market, and thus its profitability, by means of implementing a model of optimal dispatch operating on the ancillary services market
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
COMBINED CYCLE, HEAT PUMP, AND THERMAL STORAGE INTEGRATION: TECHNO-ECONOMIC SENSITIVITY TO MARKET AND CLIMATIC CONDITIONS BASED ON A EUROPEAN AND UNITED STATES ASSESSMENT
No full textThe integration of a Heat Pump (HP) with a Combined Cycle Gas Turbine (CCGT) to control the inlet air temperature has been previously investigated turning out to be a promising technology to meet the requirements imposed by the current electricity generation systems in terms of efficiency and flexibility. If the HP is coupled with a Thermal Energy Storage (TES) in an Inlet Conditioning Unit (ICU), it can be exploited in different modes to enhance the off-design CCGT’s efficiency or to boost the power output at full load. Furthermore, fuel-saving would be reflected in avoided emissions. The optimal sizing of the ICU, as well as an accurate estimation of the benefits, is a complex problem influenced by several factors such as the local climate and electricity market prices. The paper aims to systematically investigate, by means of a Mixed Integer Linear Programming model for optimal dispatch, the feasibility of an ICU integration in different scenarios (EU and US), providing general rules for assessing the concept application in new sites all around the globe. Different electricity markets have been analyzed and classified according to the parameters describing the average and variability of prices, the interdependency with the gas market, the ambient temperature, or the local carbon pricing policy. The most favorable conditions are identified and the dependency of the optimal ICU sizing on the climate and the electricity market is highlighted. The concept appears to be highly profitable in the hot regions with high price variability with an NPV of around 60 M€. Additionally, even in less profitable conditions (i.e., stable low prices in a cold climate), the system is able to increase the operating hours and reduce the economic losses. The performances enhancement described does not imply any environmental cost in terms of CO2 emissions
SCO2 BASED PUMPED HEAT THERMAL ENERGY STORAGE SYSTEMS VALORIZING INDUSTRIAL WASTE HEAT RECOVERY: A TECHNO-ECONOMIC ANALYSIS OF THE ROLE OF HIGH TEMPERATURE TES
No full textIn the current renewable energy dominated power system, as power production is becoming more and more unpredictable, it would be important to act at two levels: integrating relevant power/energy capacity of energy storage and making demand more controllable. At this purpose, acting on industrial energy demand via integration of energy storage and electrification of local processes, could provide a significant contribution. At the same time, waste heat recovery (WHR) is quite a consolidated industrial practise. Nevertheless, WH valorisation is usually performed via bottoming cycles, such as steam, ORC or supercritical CO2 (sCO2) power cycles. The development of thermo-mechanical storages to be installed at industrial level, can contribute in this direction through the use of traditional technologies (rotating machinery) employed in power plants as well as in Waste-heat-to-power (WH2P) plants. This paper presents a thermo-economic analysis of Pumped Thermal Energy Storages (PTES) for sCO2 cycles, comparing market available thermal energy storage materials for different temperature range of operation. The proposed system is purposefully designed to exploit the waste heat sources for the temperature ranges of 150-400°C, difficult to exploit for WH2P solutions and rarely addressed in literature so far. The use of sCO2 enhances the techno-economic features of these systems, the independent charging and discharging system proposed in this study can also provide a keen sense of flexibility especially for the upscaling of a PTES plant to reach an equal grid flexibility power for charging and discharging. At the same time, the valorisation of low temperature waste heat enables industries to enhance their energy efficiency, limit their operational costs and environmental impact, whilst becoming an active part in the regulation of the grid. At this purpose optimal system configurations and dispatch strategies are identified based on typical load curves of specific EU markets. Starting from an identified reference case (a cement production plant with WH temperature to be valorized around 330°C), different PTES cycle layouts and TES technological solutions are compared on a techno-economic basis. The waste heat integration to the PTES system has been found to add satisfactory value in terms of RTE. On the other hand, it proves to be an optimal use case of waste heat valorisation than traditional waste heat to power cycles when compared in terms of exergy, capital cost and dispatchability in ever increasing RES penetration scenarios. The identification of the most optimal TES however is driven by economic factors too as presented in CAPEX and dispatchability analysis
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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