Thermodynamic analysis and comparison of downdraft gasifiers integrated with gas turbine, spark and compression ignition engines for distributed power generation

The objective of the present article is to assess and compare the performance of electricity generation systems integrated with downdraft biomass gasifiers for distributed power generation. A model for estimating the electric power generation of internal combustion engines and gas turbines powered by syngas was developed. First, the model determines the syngas composition and the lower heating value; and second, these data are used to evaluate power generation in Otto, Diesel, and Brayton cycles. Four synthesis gas compositions were tested for gasification with: air; pure oxygen; 60% oxygen with 40% steam; and 60% air with 40% steam. The results show a maximum power ratio of 0.567 kWh/Nm(3) for the gas turbine system, 0.647 kWh/Nm(3) for the compression ignition engine, and 0.775 kWh/Nm(3) for the spark-ignition engine while running on synthesis gas which was produced using pure oxygen as gasification agent. When these three systems run on synthesis gas produced using atmospheric air as gasification agent, the maximum power ratios were 0.274 kWh/Nm(3) for the gas turbine system, 0.302 kWh/Nm(3) for CIE, and 0.282 kWh/Nm(3) for SIE. The relationship between power output and synthesis gas flow variations is presented as is the dependence of efficiency on compression ratios. Since the maximum attainable power ratio of CIE is higher than that of SIE for gasification with air, more research should be performed on utilization of synthesis gas in CIE. (C) 2014 Elsevier Ltd. All rights reserved.

The root systems of permian arborescent sphenopsids: evidence from the northern and southern hemispheres

Anatomically preserved calamitalean trunks are described from the Permian fossil forests of Chemnitz, Germany, and Tocantins, central-north Brazil. Several trunk bases were found in situ, still rooting in their former substrate or in parautochthonous sediments and revealing multiple organic connections between stems and roots. The new evidence of several free-stemmed Permian calamitaleans from different fossil lagerstatten and different taphonomic modes from the Northern and Southern hemispheres has implications for understanding calamite growth and challenges the universal validity of the reconstruction of rhizome-bearing woody trees. Whereas the stems belong to different species of the widely distributed genus Arthropitys GOEPPERT 1864, among them the generitype A. bistriata (COTTA) emend. RoSSLER, FENG & NOLL 2012 the attached roots represent the largest calamite roots ever found and incorporate a broad spectrum of preservational forms and ontogenetic stages. The latter are represented by the root genera Astromyelon WILLIAMSON 1878, Myriophylloides HICK & CASH 1881 and Asthenomyelon LEISTIKOW 1962 that were evidenced for the first time from Chemnitz, the type locality of Arthropitys and Calamitea (COTTA) emend. ROSSLER & NOLL 2007. Branched, stem-borne, adventitious root systems exhibit similar architectures, arise from different nodes of the lowermost trunks and anchor the trees in' different substrates. Developmental features were analysed in first- to third-order roots, which possess clearly-defined concentric tissue zones: epidermis/periderm, cortex, endodermis and central vascular tissue with or without pith. First-order roots, in particular, show considerable secondary growth. Numerous zones of concentric density variation in the secondary xylem indicate some kind of seasonality in the early Permian environments.

Entropic information for travelling solitons in Lorentz and CPT breaking systems

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Active power reserve for frequency control provided by distributed generators in distribution networks

In a smart grid environment, attention should be paid not only to the power supplied to satisfy loads and system losses but also to the services necessary to provide security and stability to the system: the so-called ancillary services. As they are well known the benefits that distributed generation can bring to electrical systems and to the environment, in this work the possibility that active power reserve for frequency control could be provided by distributed generators (DGs) in an efficient and economical way is explored. The proposed methodology was tested using the IEEE 34-bus distribution test system. The results show improvements in the capacity of the system for this ancillary service and decrease in system losses and payments of the distribution system operator to the DGs.

Leveraging wireless devices for networked control systems in industrial applications

Networked control systems (NCSs) are distributed control system in which sensors, actuators and controllers are physically separated and connected through communication networks. NCS represent the evolution of networked control architectures providing greater modularity and control decentralization, ease maintenance and diagnosis and lower cost of implementation. A recent trend in this research topic is the development of NCS using wireless networks(WNCS)which enable interoperability between existing wiredand wireless systems. This paper presents the feasibility analysis of using serial to wireless converter as a wireless sensor link in NCS. In order to support this investigation, relevant performance metrics for wireless control applications such as jitter, time delay and messages lost are highlighted and calculated to evaluate the wireless converter capabilities. In addition the control performance of an implemented motor control system using the converter is analyzed. Experimental results led to the conclusion that serial ZigBee device isrecommended against the Bluetooth as it provided better metrics for control applications. However, bothdevices can be used to implement WNCS providing transmission rates and closed control loop times which are acceptable for NCS applications.Moreoverthe use of thewireless device delay in the PID controller discretization can improve the control performance of the system.