Improving the torque generation in self-sensing BLDC drives by shaping the current waveform

Brushless DC drives are widely used in different fields of application because of their high efficiency and power density. Torque ripple can be considered one of the drawbacks of these drives. This paper proposes a method to reduce the torque ripple in BLDC drives. For this reason, the current amplitude is adapted to the rotor position rather than to be kept constant as done in a conventional commutation method. This is done by computing an optimum reference current based on the phase back-EMF waveform. The proposed approach is implemented in a self-sensing drive so its applicability to self-sensing BLDC motor drives is verified. Simulation and experimental results are given and discussed to show that the proposed method actually is able to improve torque production

Co-production of hydrogen and electricity from autothermal reforming of natural gas by means of Pd-Ag membranes

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Application of Sorption Enhanced Water Gas Shift for Carbon Capture in Integrated Steelworks

Abstract In integrated steelworks a large fraction of total CO2 is emitted from the power plant, where carbon- rich blast furnace gas (BFG) is burned to produce electricity by means of a steam cycle or a gas-steam combined cycle. The aim of the present paper is to assess the potential of Sorption Enhanced Water Gas Shift (SEWGS) process for CO2 capture from blast furnace gas. Firstly, a reference combined cycle applied to blast furnace steel plant is defined. Mass flow rate and composition of the steel plant off-gas used as fuel in the combined cycle have been derived from a large integrated steel plant. Then, the application of the SEWGS process is investigated and compared to a reference monoethanolamine (MEA)-based post-combustion absorption option. Two different SEWGS plant layouts are proposed together with two different sorbents. SEWGS achieves 85% of CO2 avoided with electric efficiency of 39% with the advanced sorbent

CAESAR: SEWGS integration into an IGCC plant

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Comparison of Thermocline Molten Salt Storage Performances to Commercial Two-tank Configuration☆

Abstract This work deals with the assessment of thermocline heat storage performances when applied to solar thermal plants. The considered thermocline is based on molten salt heat transfer fluid (Solar Salts between 300 °C and 550 °C) and filled with quartzite. A 2-D finite element heat transfer model is developed to determine the temperatures inside the vessel with mass flows input/output. The model includes heat conductivity of molten salt and quartzite rocks, heat transfer between the molten salts and the quartzite, as well as heat loss to the environment. Results of the model are compared to available experimental data as well as analytic results showing good agreement. Then, the thermocline storage with the performances predicted by the 2-D code was integrated in a CSP plant previously modelled with the two-tank TES system. Plant management is kept equal to the two-tank configuration. A performance index is introduced to make a consistent comparison between the thermocline and the two-tank system: storage efficiency is defined as the heat withdrawn from the storage above 545 °C divided by the overall input in the storage. The defined index is equal to 100% for the two tank system as thermal losses have a negligible impact. On the contrary, in thermocline storage, part of heat stored in the molten salt is in the thermocline region and this molten salt is not accounted as useful. The thickness of the thermocline is about 4 to 6 meter height out of 14 meters making the storage performances in the range of 65%, hence significantly lower than in two-tank configuration. A sensitivity analysis on tank size and tank shape factor is performed to assess the optimal configuration for the thermocline

Comparison of linear and point focus collectors in solar power plants

AbstractSolar tower based plants are seen as a promising technology to reduce the cost of electricity from solar radiation. This paper assesses the design and overall yearly performances of two different solar tower concepts featuring two commercial plants running in Spain. The first plant investigated is based on Direct Steam Generation and a cavity receiver (PS-10 type). The second plant considers an external cylindrical receiver with molten salts as heat transfer fluid and storage system (Gemasolar type). About the optical assessment performed with DELSOL3, a calibration of heliostat aim points was performed to match available flux maps on the receiver. Moving to results, the PS-10 type has higher optical performances both nominal design and yearly average. This is due both to the field size and orientation which guarantee a higher efficiency and to the receiver concept itself. About power production, the molten salts allow higher temperature and consequently conversion efficiency than PS-10. The solar-to-electricity efficiency is equal to 18.7% vs. 16.4% of DSG cavity plant. The obtained results are strictly related to the set of assumptions made on each plant component: when available real plant data where used. The two solar tower plants results were also compared to corresponding commercial linear focus plants featuring the same power block concept. Gemasolar type shows a higher solar-to-electricity efficiency compared to a parabolic trough plant with storage (18.7% vs. 15.4%) because of the higher maximum temperatures and, consequently, power block efficiency. PS-10 is better than a linear Fresnel DSG (16.4% vs. 10.4%) because of the higher optical performances

CO2 Capture from Industrial Sources by High-temperature Sorbents

Among the emerging CO2 capture technologies, systems based on high temperature (HT) regenerable sorbents had a significant development in recent years. In addition to power plants, HT sorbents technologies can be particularly promising for CO2 capture in carbon intensive industrial processes such as cement plants, steel mills and hydrogen plants. Calcium looping (CaL) is a combined post-combustion and oxyfuel combustion technology which uses calcium oxide (CaO) as CO2 sorbent. In this process, CO2 in combustion flue gases is absorbed in a carbonator reactor by forming calcium carbonate (CaCO3) through the exothermic carbonation reaction. Carbonated sorbent is then regenerated to CaO through the reverse calcination reaction in a calciner, where reaction heat is provided by oxyfuel combustion. A CO2 concentrated stream is therefore released from the calciner, which can be purified and compressed as in conventional oxyfuel product gas. Calcium looping is particularly promising for application in cement plants, because the raw materials used for the production of clinker (the energy intensive process in cement manufacturing) are rich of CaCO3, which is also the starting material of the CaL CaO sorbent. Therefore, no additional material needs to be imported or is released as waste when CaL is integrated in a cement plant. Two main configurations can be assumed to integrate the CaL process into a cement burning line: (i) the tail-end configuration, where the CaL process is used as a post-combustion, end-of-pipe capture process and (ii) a highly integrated configuration, where the CaL reactors are integrated into the raw meal preheating tower of the clinker production process and the CaL oxyfuel calciner coincides with the raw meal pre-calciner. Another class of processes where CaO is used as CO2 sorbent is sorption enhanced reforming (SER) technologies, where CO2 is absorbed within a steam methane reforming (SMR) reactor. The advantage of this class of processes is that the heat released by sorbent carbonation reaction matches very well with the steam methane reforming reaction. Moreover, the removal of the CO2 reaction product allows a greater advancement of the reforming and water gas shift (WGS) reactions. As a result, with a SER reactor, a H2 production and CO2 separation are performed in a single adiabatic reactor operating at moderate temperature (~650°C) instead of a sequence of reactors for steam reforming (~900°C), WGS (200-400°C) and CO2 separation (~30°C) operating in a wide temperature range as in conventional H2 production processes. In addition to material development, the main challenge in SER technologies is in the endothermic sorbent regeneration step. Several process schemes have been proposed for sorbent calcination, such as: (i) oxyfuel combustion, (ii) high temperature heat exchangers, (iii) direct contact heating with hot solids from a chemical looping combustion loop. Both fluidized bed and packed bed reactors are proposed for SER processes operating at different temperature and pressure range. If a CO2 sorbent is active at intermediate temperatures (~400°C), such as in the case of hydrotalcite-based sorbents, it can be adopted in sorption enhanced WGS (SEWGS) processes. As in the SER principle, the in-situ removal of CO2 form the gas phase allows a higher advancement of the WGS reaction. Therefore, H2-rich gas production and CO2 separation can be performed in a single pressurized reactor. While this concept can be adopted in hydrogen production plants, a promising application is in steel mills, where most of the CO2 emissions are associated to the combustion of the blast furnace gas (BFG) in the steel mill power plant. BFG is a byproduct of the pig iron production process and is a low calorific value fuel rich of CO, CO2 and N2. By processing BFG in a SEWGS reactor, a H2-N2 stream is produced, which can be burned at high efficiency in a low emission combined cycle. CaL, SER and SEWGS processes illustrated above for CO2 capture in industry, are being developed in the three ongoing EU FP7 and H2020 projects Cemcap (G.A. 641185), Ascent (G.A 608512) and Stepwise (G.A. 640769). In this work, the potential of these processes in terms of CO2 capture efficiency and energy efficiency will be discussed and compared with benchmark technologies, based on process integration and simulation studies

Energetic and economic analysis of a solar assisted heat pump for pasteurization process

In the present paper, the energetic and economic analysis of a solar-assisted heat pump for an industrial pasteurization process is investigated. The considered system consists of thermal energy storage, a water-to-water heat pump and a solar field made up of both photovoltaic-thermal collectors and evacuated tube collectors. A mathematical model of each component of the system is built and validated, while the overall model of the system is built with a bottom-up approach. The energetic and economic analysis is performed on a yearly basis varying the storage size and the solar field size and considering a boiler-only scenario as the reference system. The results show that, from the energetic point of view, the best system could provide up to 90% of the energy required by the process and, consequently, significantly reduce auxiliary boiler consumption. On the other side, from an economic point of view, the best solution provides a minimum payback time approximately equal to 8 years with 14.4% internal rate of return

Novel Methodology to Assess Advanced Biofuel Production at Regional Level: Case Study for Cereal Straw Supply Chains

Nowadays, there is an urgent necessity for breakthrough technologies able to reduce process complexity and to lower costs to make the biomass-based biodiesel supply chain competitive. This paper presents an innovative methodology for the identification of secondary biomass potentials for biofuel production. The methodology, divided into four steps, defines the criteria that allow identification of promising scenarios of biomass supply chains for commercial application of innovative technologies. The model set up a scoring procedure based on carbon emission avoidance, efficient resource exploitation and sustainability indexes. Applying the four levels of analysis (biomass availability, suitability analysis, regionalization and multi-criteria analysis), the cereal straw supply chains in four European districts (Scandinavian, Hanseatic, Central European and Mediterranean) have been identified and grouped in 18 biomass supply regional clusters (BSRCs). The clusters represent the most promising hotspots where biomass availability, logistics and feedstock requirements for a novel conversion technology meet. Central European and Mediterranean districts are those with the highest cereal straw bioeconomic potentials which allow mono-feedstock supply chains and relatively high capacity of a conversion technology at 200 MWth and beyond. Central Europe has an overall bioeconomic potential of 16.249 kt (232.359 TJ) distributed over 36 regions and organized in 12 BSRCs. The Mediterranean district has an overall bioeconomic potential of 3541 kt (50.630 TJ) distributed over nine regions and organized in four BSRCs

Preliminary Assessment of sCO2Power Cycles for Application to CSP Solar Tower Plants

This work presents a preliminary thermodynamic assessment of three different supercritical CO2(sCO2) power cycles integrated in a high temperature solar tower system, working up to 800°C. An indirect cycle configuration is considered with KCl-MgCl2molten salt as heat transfer fluid (HTF) in the solar receiver and a two tanks thermal energy storage (TES) system. The most promising cycle configuration is selected, optimizing the cycle turbine inlet temperature to achieve the best compromise between cycle and receiver efficiency. An estimate of the yearly energy yield of the proposed power plant is finally performed, indicating the possibility of reaching solar-to-electric efficiency of about 17.5%