Modelling of multi-megawatt wind turbines for EMI and EMS investigations by a topological approach
Todays installed multi-megawatt wind turbines (WT) form highly diverse system due to very complex control devices. Thus, special attention has to be paid to the electromagnetic compatibility (EMC) of the wind turbine. This contribution deals with different electromagnetic interference (EMI) and susceptibility (EMS) effects within the wind turbine. A well-known susceptibility problem of constructions and buildings with large vertical dimensions is the threat situation due to lightning phenomena. On the one hand, the high amplitude of the lightning current effects destructions of infrastructure directly. On the other hand, the transient electromagnetic fields caused by this lightning current could lead to disturbances as well as destructions of electronic devices inside the wind turbine. Furthermore, common-mode currents ¡cm on the power lines between the generator and the frequency converter will cause EMI effects during the normal operation mode. These I cms lead to radiated emissions to the WT's environment as well as to transient disturbing fields inside the WT, which might interfere with the control unit (CU) and the condition monitoring system (CMS). These issues will be investigated in this contribution. Therefore, the electromagnetic topology (EMT) will be applied to the wind turbine. The EMT delivers useful information in order to increase the WT's susceptibility and ensure a high degree of availability.
Determination of radiated emissions from wind energy conversion systems
This paper presents a measuring concept for determining the radiated electromagnetic emissions from wind turbines. The need for a more precise measurement specification for wind turbines will be explained with reference to a procedure, which is according to the normative situation. Then, an approach to simplify the determination of radiated electromagnetic fields by using a measurement of common-mode (CM) current is presented. It is shown that a measurement of the CM current indicates the frequencies, where an increased emission can be expected, in particular on the magnetic field. Thus, the technical effort and the measurement uncertainty are significantly reduced when determining the magnetic field of a wind turbine.
Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization
Abstract The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36 days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186 ± 0.3 mg L − 1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76 ± 0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.