364 research outputs found
Power quality requirements and responsibilities at the point of connection
In the present power delivery environment, electricity as a product has become more competitive than before. Modern electrical devices are complex in terms of their functionalities and are more sensitive to the quality of the supplied electricity. A disturbance in supply voltage can cause significant financial losses for an industrial customer. Moreover, there are increasing number of disputes in different countries of the world among the network operators, the customers and the device manufacturers regarding their individual responsibility concerning 'Power Quality' (PQ) problems and solutions. In addition, the existing standards on PQ give very limited information about responsibility sharing among the involved parties. PQ disturbances can be originated in the network as well as at the customer's premises and can propagate to other parts of the network. The PQ level in the network is also highly influenced by PQ emission behaviors of customer's devices and the network characteristics. During the last decades, PQ related complaints have increased largely. Inadequate PQ can lead to various technical and financial inconveniences to the customers and the network operators. This research aims to find out a socio-economically optimum solution to PQ problems. The main objectives of this thesis are defined as: "Analyze main PO problems and their consequences to various involved parties in the network. Next, define optimal PQ criteria at the customer's point of connection (POC) and finally specify responsibilities of the involved parties". The thesis is based on practical field measurements of PQ parameters in the network, on analyzing the developed network models by using computer simulations and laboratory experiments. The most important part of the work is the verification of simulation results with thepractical measurements. Further, the obtained results are compared with the values given in the available standards. Lastly optimal PQ parameters at a poc are defined for flicker, harmonics and voltage dips. A summary of the research work reported in this thesis is as follows: âą Obtained a deeper insight in PQ problems around the world âą Developed typical network models for computer simulations on different PQ phenomena (such as flicker, harmonics and voltage dips) and verified the results with field measured data âą Gathered practical information on various technical and financial consequences of inadequate PQ for different parties namely: the network operators, the customers and the equipment manufacturers âą Made an inventory on various existing (and developing) standards and technical documents on PQ around the world. Then, compared the limits given on various PQ parameters in those standards/documents and discussed their relevance and applicability in the future âą A proposal is given about optimal PQ limits (for flicker, harmonics) at the low voltage (LV) customer's POC Also, the average and maximum values of voltage dips in the networks are estimated âą Suitable planning level limit values for flicker, harmonics and voltage dips are proposed âą PQ related responsibilities of the customers, network operators and device manufacturer at the customer's POC are defined The main conclusions and thesis contributions are: âą It is found that a harmonization among the presently available PQ standards is required and a dedicated set of global standards is needed to get optimal PQ at the customer's POC Various limiting values on different PQ parameters (e.g. flicker emission and harmonic current emission limits for a customer) at a POC are proposed in this thesis. Also, the average and maximum numbers of voltage dips in the Dutch high voltage (HV) and medium voltage (MV) networks are estimated. âą A new set of planning level values for flicker severities at different voltage levels of a network is proposed. For harmonics, a proposal is given to change the planning level values for 'triple n' harmonic voltages and new values are suggested for the MV and LV networks. Moreover, it was proposed that the 3rd harmonic summation coefficient value of the standard can be modified to a higher value as sufficient diversity is found in the system. Regarding voltage dips, the numbers of planning and compatibility levels are proposed for a MV network in the Netherlands. In this thesis, PQ responsibility sharing procedures are defined for a network operator, customer and a device manufacturer. Network impedance is identified as an important parameter in deciding flicker and harmonics at a POC The network operator should provide information on the approximate number of occurrence of voltage dips in a year at a customer's POC To maintain sufficient PQ level in the network, all the involved parties should follow certain rules and duties. It was concluded that PQ regulation can be successfully implemented in the electricity business when all the involved parties are aware of their respective responsibilities in the network
Advances in Repurposing and Recycling of Post-Vehicle-Application Lithium-Ion Batteries
Increased electrification of vehicles has increased the use of lithium-ion batteries for energy storage, and raised the issue of what to do with post-vehicle-application batteries. Three possibilities have been identified: 1) remanufacturing for intended reuse in vehicles; 2) repurposing for non-vehicle, stationary storage applications; and 3) recycling, extracting the precious metals, chemicals and other byproducts. Advances in repurposing and recycling are presented, along with a mathematical model that forecasts the manufacturing capacity needed for remanufacturing, repurposing, and recycling. Results obtained by simulating the model show that up to a 25% reduction in the need for new batteries can be achieved through remanufacturing, that the sum of repurposing and remanufacturing capacity is approximately constant across various scenarios encouraging the sharing of resources, and that the need for recycling capacity will be significant by 2030. A repurposing demonstration shows the use of post-vehicle-application batteries to support a semi-portable recycling platform. Energy is collected from solar panels, and dispensed to electrical devices as required. Recycling may be complicated: lithium-ion batteries produced by different manufacturers contain different active materials, particularly for the cathodes. In all cases, however, the collecting foils used in the anodes are copper, and in the cathodes are aluminum. A common recycling process using relatively low acid concentrations, low temperatures, and short time periods was developed and demonstrated
End-of-Life Impact on the Cradle-to-Grave LCA of Light-Duty Commercial Vehicles in Europe
A cradle-to-grave life cycle assessment focused on end-of-life (EoL) was conducted in this study for three configurations of a light-duty commercial vehicle (LDCV): diesel, compressed natural gas (CNG), and battery electric vehicle (BEV). The aim is to investigate the impact of recycling under two EoL scenarios with different allocation methods. The first is based on the traditional avoided burden method, while the second is based on the circular footprint formula (CFF) developed by the European Commission. For each configuration, a detailed multilevel waste management scheme was developed in compliance with the 2000/53/CE directive and ISO22628 standard.
The results showed that the global warming potential (GWP) impact under the CFF method is significantly greater when compared to the avoided burden method because of the A-parameter, which allocates the burdens and benefits between the two connected product systems. Furthermore, in all configurations and scenarios, the benefits due to the avoided production of virgin materials compensate for the recycling burdens within GWP impact. The main drivers of GWP reduction are steel recycling for all of the considered LDCVs, platinum, palladium, and rhodium recycling for the diesel and CNG configurations, and Li-ion battery recycling for the BEV configuration. Finally, the EoL stage significantly reduces the environmental impact of those categories other than GWP
End-of-Life Impact on the Cradle-to-Grave LCA of Light-Duty Commercial Vehicles in Europe
A cradle-to-grave life cycle assessment focused on end-of-life (EoL) was conducted in this study for three configurations of a light-duty commercial vehicle (LDCV): diesel, compressed natural gas (CNG), and battery electric vehicle (BEV). The aim is to investigate the impact of recycling under two EoL scenarios with different allocation methods. The first is based on the traditional avoided burden method, while the second is based on the circular footprint formula (CFF) developed by the European Commission. For each configuration, a detailed multilevel waste management scheme was developed in compliance with the 2000/53/CE directive and ISO22628 standard. The results showed that the global warming potential (GWP) impact under the CFF method is significantly greater when compared to the avoided burden method because of the A-parameter, which allocates the burdens and benefits between the two connected product systems. Furthermore, in all configurations and scenarios, the benefits due to the avoided production of virgin materials compensate for the recycling burdens within GWP impact. The main drivers of GWP reduction are steel recycling for all of the considered LDCVs, platinum, palladium, and rhodium recycling for the diesel and CNG configurations, and Li-ion battery recycling for the BEV configuration. Finally, the EoL stage significantly reduces the environmental impact of those categories other than GWP
Energy analysis of a fruit drying plant in Adeiso, Ghana
The purpose of the project has been to work out recommendations that reduce the energy-related costs and environmental impact of HPW Fresh & Dry Ltd., a fruit
drying factory in Ghana. The factory produces electricity with diesel and biogas but also purchases electricity from the national electricity company. Heat for the drying
process is produced from biogas, kerosene and solar panels. In the project the energy system was analyzed by measuring production and consumption of heat and electricity.
The project results show that the factory can become self-sufficient on heat if the available energy is used more efficient. The production units for both electricity and heat have low efficiencies. Inadequate insulation and sealing contributes to the poor performance of the heat system. The electricity measurements show that several
electrical loads are unbalanced and that the three phase cooling machines are not fully utilized.
The factory is recommended to invest in a new kerosene boiler and a roaster boiler for combustion of coconut waste. Furthermore, the biogas should be combusted in a
boiler instead of in the now used combined heat and power engine (CHP), for improved utilization of the gas. Unused capacity of the three phase cooling machines could replace the less efficient single-phase cooling machines. Moreover, the electrical loads should be balanced and the usage of motors connected to the biogas plant minimized. By insulating pipings and seal leakages, heat losses and the need of cooling will decrease. Finally, the factory is recommended to install automatic regulation of the boilers to avoid over-heating of the storage tank.Syftet med projektet har varit att ta fram rekommendationer för hur HPW Fresh & Dry Ltd., en frukttorkningsfabrik i Ghana, kan minska sina energirelaterade kostnader
och sin miljöpÄverkan. Fabriken producerar el med diesel och biogas samt köper el frÄn nationella elbolaget. VÀrme till torkprocessen produceras med biogas, fotogen och solpaneler. I projektet analyserades energisystemet genom att mÀta produktion och konsumtion av vÀrme och el.
Resultaten frÄn projektet visar att fabriken kan bli sjÀlvförsörjande pÄ vÀrme om den tillgÀngliga energin anvÀnds mer effektivt. Produktionsenheterna för bÄde el och
vÀrme generellt har lÄga verkningsgrader. BristfÀllig isolering och tÀtning bidrar till den lÄga prestandan i vÀrmesystemet. ElmÀtningarna visar bland annat att flera
elektriska laster Àr obalanserade samt att det finns outnyttjad kylkapacitet i fabrikens trefasiga kylmaskiner.
Fabriken rekommenderas att investera i en ny fotogenvÀrmepanna samt en vÀrmepanna för förbrÀnning av kokosnötavfall. Vidare bör biogasen förbrÀnnas i en
vÀrmepanna istÀllet för i den nu anvÀnda kraftvÀrmemotorn, för att bÀttre utnyttja gasen. Outnyttjad kylkapacitet pÄ de trefasiga kylmaskinerna kan ersÀtta mindre effektiva enfasiga kylmaskinerna. Dessutom bör de elektriska lasterna balanseras och driften av elmotorer till biogasanlÀggningen minimeras. Genom att isolera rör och tÀta vÀrmelÀckage kan vÀrmeförluster och kylbehov minskas. Slutligen
rekommenderas fabriken att installera automatisk reglering av vÀrmepannorna för att undvika övervÀrmning av ackumulatortanken
Solid State Drive: New Challenge for Forensic Investigation
There has been a tremendous increase in the usage of electronic devices day by day. With the increase in usage of electronic devices, technology keeps on emerging. Due to the emergence of new technologies, there has always been a scope for the hackers to cash the loopholes that are available which resulted in a hefty increase in cyber crimes. Consequently, the number of investigations that require digital forensic expertise have been resulting in a huge evidence backlogs that are being encountered by the law enforcement agencies all over the world. It is anticipated that the number of cases that would require digital forensics is likely to be increased in future.
The primary storage technology used for digital information has remained constant over the last two decades in the form of the magnetic disc. For decades, Hard drives have been dominating the market due to their cost and capacity. However, things are being developed and manufactured to be faster and smaller but there are few changes that truly turned to be technological revolutionary. Solid states drive familiarly known as SSD have crept up on us as they arrive under cover of the previously known technology. This paper demonstrated that the assumptions about the behavior of a storage media are no longer valid, how modern storage devices will operate under their own volition without any computer instructions. These operations are highly destructive of traditionally recoverable data. This would contaminate evidence, can make validation of digital evidence reports difficult, it can complicate the process of live and dead analysis recovery and can also complicate and frustrate the post recovery forensic analysis. This paper compared the key evidence that were identified in an HDD and SSD and discussed the key features that make SSD self-Destructive and cause difficulties for Forensic Investigations
Enhanced decoupling current scheme with selective harmonic elimination pulse width modulation for cascaded multilevel inverter based static synchronous compensator
This dissertation is dedicated to a comprehensive study and performance analysis of the transformer-less Multilevel Cascaded H-bridge Inverter (MCHI) based STATic synchronous COMpensator (STATCOM). Among the shunt-connected Flexible AC Transmission System (FACTS) controllers, STATCOM has shown extensive feasibility and effectiveness in solving a wide range of power quality problems. By referring to the literature reviews, MCHI with separated DC capacitors is certainly the most versatile power inverter topology for STATCOM applications. However, due to the ill-defined transfer functions, complex control schemes and formulations were emerged to achieve a low-switching frequency high-bandwidth power control. As a result, adequate controller parameters were generally obtained by using trial and error method, which were practically ineffective and time-consuming. In this dissertation, the STATCOM is controlled to provide reactive power (VAR) compensation at the Point of Common Coupling (PCC) under different loading conditions. The goal of this work is to enhance the performance of the STATCOM with the associated proposed control scheme in achieving high dynamic response, improving transient performance, and producing high-quality output voltage waveform. To evaluate the superiority of the proposed control scheme, intensive simulation studies and numerous experiments are conducted accordingly, where a very good match between the simulation results and the experimental results is achieved in all cases and documented in this dissertation
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