State-of-the-Art Review of Vortex-Induced Motions of Floating Offshore Wind Turbine Structures

The motivation for this study is the fast development of floating offshore wind energy and the immature methodology and engineering practice related to predictions of vortex-induced motions (VIM). Benefiting from the oil and gas industry, in the past several decades, extensive knowledge and experience on vortex-induced vibrations (VIV) on slender marine structures has been gained. As the learnings from these efforts should be transferred and adapted to the renewable energy industry, a state-of-the-art review on influential VIM research has been carried out in this paper, focusing on: (1) engineering practice, (2) model tests, (3) numerical calculation, and (4) field measurement. Engineering gaps and potential research topics are identified as future work.publishedVersio

Inventory control of particulate processes

Abstract In this work we address the problem of designing model-based controllers for particulate processes described by population balance (PB) models. We focus on PB models that are solved by numerical discretization, for which many standard control methodologies are not suitable due to the high order of these models. We interpret discretized PB models as chemical reaction networks and suggest to combine inventory control with techniques of stability of chemical reaction networks to design the controller. Inventory control is based on the idea of manipulating process flows so that certain extensive variables defining the system, called inventories, follow their setpoints. The whole system is stabilized by controlling the dominant inventories. The discretized PB is exploited in all aspects of controller design, from determining the controlled inventories to the final implementation of the control law. The methodology is illustrated with an industrial leaching reactor, the Silgrain ® process. We show that the discretized PB model takes the form of a Feinberg-Horn-Jackson zero-deficiency network, allowing us to prove stabilization of the whole system. The performance of standard inventory control and robust inventory control are investigated by simulation, with satisfactory results even in the presence of modeling errors

Modeling, Identification and Control at Telemark University College

Master studies in process automation started in 1989 at what soon became Telemark University College, and the 20 year anniversary marks the start of our own PhD degree in Process, Energy and Automation Engineering. The paper gives an overview of research activities related to control engineering at Department of Electrical Engineering, Information Technology and Cybernetics

Optimal Operation of the Peat Drying Process in Steam Tube Dryers

Ukraine is an energy-dependent country and aims to reduce the import of natural gas, heat, and power in general. This implies extracting fuel from her own natural resources; one relevant and readily available energy carrier for such extraction is peat (bio mass). Currently, the operating regimes of the drying of peat are not energy efficient; these operating regime maps were developed in the 1970s and aimed only to get dry peat of required quality, without taking into account the cost of heat and electric energy in the drying process. The current quality of dried peat in the dryer does not always satisfy the necessary quality; e.g. parts of the peat may be insufficiently dried, or it may be over-dried. This affects the energy performance of peat briquette production. To improve the quality and energy efficiency of the peat drying process, an analysis of the drying process is carried out: an empirical mathematical model of the drying process is developed using the GMDH principle [1, 2, 3], mapping input parameters and disturbances to output qualities based on available experimental data. Next, with known (measured) disturbances, optimal input parameters for the drying process are found. Changing the operational parameters too fast leads to insufficient drying or over-drying of parts of the peat. Thus, to avoid changing the operational conditions too fast, the operational conditions are classified into a number of classes corresponding to a certain range of values for the operational parameters. Finally, an iterative procedure for changing the input parameters from the past values to new values is introduced. The resulting algorithm for finding the optimal operation of peat drying is based on mathematical models developed from experimental data, and aims to ensure improved quality and energy efficiency in the peat drying process

En vurdering av økologisk risiko ved bruk av introduserte bartreslag i Norge. Erfaringer ved bruk av kriteriesettet for Norsk svarteliste 2007

Artsdatabanken har etablert en arbeidsgruppe (Treslagsgruppen) som har vurdert økologisk risiko for et utvalg av introduserte bartreslag. Arbeidet tok utgangspunkt i kriteriesettet for risikovurdering som lå til grunn for Norsk svarteliste 2007. Gruppen har dernest vurdert egnetheten av dette kriteriesettet for trær, og har trukket følgende hovedkonklusjoner: • Vurderinger av 11 utvalgte bartreslag viste høy eller ukjent risiko for flere arter, men resultatet var mer knyttet til egenskaper ved kriteriene enn vitenskaplig dokumentasjon. Arbeidsgruppen utelukker likevel ikke at introduserte bartrær kan ha noen av de negative effektene som er beskrevet i Norsk svarteliste 2007. • Gruppen mener at gjeldende kriteriesett ikke følger naturvitenskapelige prinsipper og arbeidsmåter og derfor ikke er egnet for økologisk risikovurdering av bartrær. Flere av kriteriene fremstår som upresise, og viktige definisjoner mangler. • Når dokumentasjon mangler må dette fremgå eksplisitt, og systemene bør være transparente slik at det fremgår klart hvilke vurderinger som er dokumentert, og hvilke som baseres på faglig skjønn. • Det anbefales at fremtidige vurderinger graderer risiko i flere klasser for å gi et mer presist forvaltningsverktøy. • Et fremtidig kriteriesett for trær bør i sterkere grad vektlegge spredning og populasjonsendringer, og vurderes innen definerte arealrammer og i forhold til definerte, målbare effekter. • For å unngå for stor grad av subjektivitet anbefaler gruppen at risikovurderingene i fremtiden gjennomføres i paneler med minimum tre fagpersoner med solid kunnskap om de artene som skal vurderes. • Treslagsgruppen har sammenstilt økologisk informasjon om elleve introduserte bartrær (VITEN, Skog og landskap, 1/09). Informasjonen kan være et utgangspunkt for risikovurderinger etter et nytt kriteriesett. • Gruppen påpeker at det er betydelig kunnskapsmangel knyttet til spredning og effekter for flere introduserte treslag og at det er behov for en større FoU-innsats på fagfeltet

Modeling, Identification and Control at Telemark University College

Master studies in process automation started in 1989 at what soon became Telemark University College, and the 20 year anniversary marks the start of our own PhD degree in Process, Energy and Automation Engineering. The paper gives an overview of research activities related to control engineering at Department of Electrical Engineering, Information Technology and Cybernetics