1,721,007 research outputs found
Thermo-economic optimization of the impact of renewable generators on poly-generation smart-grids including hot thermal storage
No full textCarbon Exergy Tax (CET): Impact on Conventional Energy Systems Design and Its Contribution to Advanced Systems Utilisation
No full textCarbon Tax vs CO2 Sequestration Effects on Environomic Analysis of Existing Power Plants
No full textAn Analytical Procedure for the Carbon Tax Evaluation
No full textIn this paper, an analytical procedure for carbon tax evaluation is presented. The aim is the assignment to energy plants of a charge linked to their CO 2 emissions. The problem is faced through the use of an environomic approach, including evaluation of the cost of the exergy destroyed inside the system and the cost of exergy rejected to the biosphere with the plant wastes ( EÅciency penalty ) coupled with evaluation of the Index of CO 2 emission herein deÆned. In this way, the procedure allows a cost of the emitted CO 2 to be obtained based not on political considerations but only on eÅciency and exergy analysis. The aim is to reward the eÅcient use of energy resources and to penalize the ineÅcient plants. The procedure is applied for the analysis of three typical Italian energy plants burning fossil fuels: a 320 MW coal steam plant; a 700 MW natural gas combined plant; and a 30 MW gas turbine cogeneration plant. The plants are analysed using an environomic optimization and taking into account all their pollutant emissions (CO, NO x ,SO x and CO 2 ). The values of the CO 2 emissions charges obtained with the proposed procedure are presented and discussed in depth and a comparison with the possible costs of CO 2 sequestration activities is presented to
Advanced Control System for Grid-Connected SOFC Hybrid Plants: Experimental Verification in Cyber-Physical Mode
No full textThis paper presents a model predictive controller (MPC) operating a solid oxide fuel cell (SOFC) gas turbine hybrid plant at end-of-life performance condition. Its performance was assessed with experimental tests showing a comparison with a proportional integral derivative (PID) control system. The hybrid system (HS) operates in grid-connected mode, i.e., at variable speed condition of the turbine. The control system faces a multivariable constrained problem, as it must operate the plant into safety conditions while pursuing its objectives. The goal is to test whether a linearized controller design for normal operating condition is able to govern a system which is affected by strong performance degradation. The control performance was demonstrated in a cyber-physical emulator test rig designed for experimental analyses on such HSs. This laboratory facility is based on the coupling of a 100 kW recuperated microturbine with a fuel cell emulation system based on vessels for both anodic and cathodic sides. The components not physically present in the rig were studied with a real-time model running in parallel with the plant. Model output values were used as set-point data for obtaining in the rig (in realtime mode) the effect of the fuel cell system. The result comparison of the MPC tool against a PID control system was carried out considering several plant properties and the related constraints. Both systems succeeded in managing the plant, still the MPC performed better in terms of smoothing temperature gradient and peaks
A new generalised Carbon Exergy Tax for CO2 emission internalisation: an effective rule to control global warming
No full textPerformance curves of prime movers for smart polygeneration grids
No full textThe purpose of this paper is to present and discuss the performance of experimental curves related to the following prime movers for smart polygeneration grids: a microturbine (100 kW electrical power), an internal combustion engine (20 kW electrical power), a SOFC-based hybrid system (450 kW virtual electrical power) and an absorption chiller (100 kW cooling power). The experimental results reported here were obtained using a new facility developed by the Thermochemical Power Group: essential operations for distributed generation grids equipped with different types of technologies are possible, as well as test with different control and optimisation algorithms. Apart from the data on the hybrid system (obtained with an emulator rig based on the coupling of a microturbine, a modular vessel and a real-time simulation model for components not present in the rig), the performance curves of the other devices were obtained from measurements on real machines. Given the influence of ambient temperature on microturbine performance, correlations related to this parameter were developed from experiments for easy application in optimization tools
Thermo-economic comparison of hydrogen and hydro-methane produced from hydroelectric energy for land transportation
No full textThis paper aims to investigate a system for large size hydrogen production, storage and distribution to refueling stations for its employment in land transportation. Hydrogen is produced by pressurized alkaline electrolysers, employing time-dependent renewable electricity produced by a large size hydroelectric plant (100 MW); the hydrogen is stored into pressurized tanks and delivered by trucks to the refueling stations. Since the technologies related to hydrogen vehicles still present high costs, an alternative solution is investigated: the hydrogen produced by water electrolysis is converted into Hydro-methane (a blend of methane and hydrogen, where H2 maximum volume content is 30%), which is easier to be stored and transported to the refueling stations, considering its higher energy content in volume terms. Since electricity available from the hydroelectric plant varies widely throughout the year, a time-dependent hierarchical thermo-economic analysis is performed in order to investigate both the optimal size of the whole plant and the management of the alkaline electrolysers. The analysis is carried out for the H2 and Hydro-methane plant lay-outs, comparing the results from energetic, strategic and economic point of view in a typical European economic scenario (Italy). For the different plant lay-outs, two energy scenarios are considered: (i) to feed the electrolysers only with renewable hydroelectricity during the year, keeping them off when it is not available; (ii) to purchase electricity from the national grid in shortage periods, in order to increase the utilization factor of the electrolysers and the production of H2 and Hydro-methane for the refueling stations
Techno-Economic Analysis of Power-to-Heat Systems
No full textThe heating and cooling sector, responsible for a large fraction of greenhouse emissions, may have a large scale impact on the energy system evolution contributing to smart industrial and domestic electrification; at the same time the recent increase of renewable energy sources installation, posing a threat in terms of grid stability, makes available a considerable amount of clean and cheap electrical energy during peak hours production. Power to heat technologies constitute a promising solution to face both these issues reducing the electric demand variability and decarbonizing the heat production. Large vapor compression heat pumps are a reliable technology able to compete, under the economic point of view, with the heat-only-boilers in order to serve district heating networks. Performance and economic profitability of a compression cycle is strongly dependent on available thermal source and the temperature of water delivered to the network. The present work explores and compares performance and economic indicators under different installation conditions, considering compression heat pumps employing four different fluids: a traditional HCF (R134a) and three natural fluids, ammonia (R717), butane (R600), and propane (R290), often preferred nowadays to HCFs due to the lower global warming potential
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