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The ZEB Laboratory is an experimental facility located in NTNU Gløshaugen campus in Trondheim. The building is designed as 4 storeys high and 1800 m2 area office space and should achieve the ZEB-COM ambition level over 60 years. The laboratory will contribute to build knowledge for zero-emission buildings, it will be an arena for experimental investigation of user-building interaction, and a laboratory to test new technologies on a large scale. Innovative ventilation and energy technologies are included. At the first floor two identical rooms are equipped as test cells with dedicated HVAC systems, a larger number of sensors and with a higher flexibility for control. This paper reports some characteristics of the ZEB Laboratory and some of the research possibilities.

A 5 MW Tension-Leg-Buoy (TLB) concept has been optimized and developed. The design is based on the MIT Double Taut Leg, initially proposed by Professor Sclavounos of MIT in 2005. Six variants have been tested, in two wave tank tests, to prove the concept and aid validation of 3DFloat, the coupled aero-hydro-servo-elastic tool utilized for the numerical computations. Optimized TLB designs are presented in this thesis for harsh weather sites in the North Sea basin, and a new TLB design (designated TLB B2) for the K13 Deep water site in the Dutch North Sea. The TLB concept relies on inclined taut synthetic fibre mooring lines and excess buoyancy for stability. Thus, its natural resonance (Eigen) periods must be shorter than wave periods in the high energy part of the wave spectrum, i.e. less than 3.5 seconds. Ensuring that none of the Eigen-periods interfere with the rotor rotational periods then becomes challenging and requires a sophisticated optimization approach. Due to low damping, the structure is prone to resonant behaviour and fatigue becomes important. Fatigue damage is particularly high when the rotor is in idle or parked mode and the aerodynamic damping contribution is low. However, even when accounting for fatigue, the resulting need for primary steel in the construction is low. The TLB B2 design has a draft of 40 m and buoyancy of 2166 tons. The total mass is 1068 tons, of which the floater accounts for only 355 tons. The remaining mass origin from the 350-ton nacelle assembly and the 363 tons of tower structure. Due to the strong influence of Eigen-periods, the design is sensitive to site conditions, especially water depth and environmental conditions. It is therefore challenging to develop a straightforward strategy to determine its potential at a given site. A specific design approach has therefore been developed and the validity of a two-stage optimization procedure (frequency-domain followed by time-domain optimization) is presented. The approach is verified by Ultimate-, Accidental, and Fatigue Limit state analyses. The design approach features a cost evaluation in a Levelised Cost of Energy perspective (LCOE) and the concept’s performance parameters are compared to those of various floating turbine concepts, bottom-fixed monopiles and jacket structures. In terms of capital expenditure (CAPEX), TLB B2 is the optimal concept for the K13 site, low material and production costs providing a significant advantage. The combined CAPEX of production and mooring is significantly lower than the production cost alone for both jacket and monopile foundations. In terms of LCOE, at about € 107 per MWh over a lifetime of 25 years, the TLB B2 is comparable to monopile foundations in an optimal depth (around 15 m) of water. The relative variation of the concepts’ LCOE is assumed to be 7% and 8 %, respectively. In comparison to previous TLB designs, the TLB B2 design substructure mass is 19 % lower, and the anchor loads are 47 % lower. The mooring loads are comparable to those of typical catenary mooring systems. The work presented in the thesis shows that TLB designs can potentially provide simple and economically advantageous options for supplying green energy in intermediate water depths of 50 to 100 m and should therefore be pursued further. Oslofjordalliansen, MARINET

This thesis is based on previous work from 2008 by MSc students David W. Moss and Anders Myhr. They have been working on a concept study for large scale assembly of floating offshore wind turbines. Further improvement of the concept is done in this thesis by identifying the worst case scenarios and operation conditions. The current investigation has been carried out with relevance to a semisubmersible platform operating on site in offshore locations. Analysis has been carried out with four turbine concepts to verify loads occurring during challenging environmental conditions. Extreme operating conditions are set to allow operation 90 % of the time within the North Sea region. There are currently few studies made on the subject of large scale assembly and erection of floating offshore turbines. The wind farms are located in hostile waters making traditional lifts and towing nearly impossible if a high rate of production is to be achieved on a rational basis. Pivot rotation by the means of ballast transfer is a common technology used in the offshore industry. Utilizing the concept on floating wind turbines is yet to be explored and seems to have large potential. Challenges related to the fact that most of the current floating wind turbines have geometrical differences would have to be overcome. At this early stage it is not known what kind of floating turbine concept will be proven to be economically viable. Making the pivot concept adaptable to several different wind turbine concepts is thus important. One other main goal is to incorporate all of the assembly features from connecting the individual tower parts to handling the anchor lines for the wind turbines. The cradle, named after the Roman god of wind Aquilo, is a simplistic design with focus mainly on direct axial stress elements. An effort was made to limit the number of elements and joints in the structure. The main challenge in the design lies in balancing the weight of the turbine in horizontal position and utilizing the same construction elements to cope with the wave loads that will interact with the turbine floater when in vertical position.Worst case loading conditions are dependent on dynamic response from the assembly platform. Current results show that the pivot concept performs as anticipated. The versatility for application of different assembly platforms is yet to be proven but should result in lesser dynamic response and loading on both the pivot concept and turbine towers. It is clear that turbines with a smaller draught will make assembly more versatile and less prone to weather. Adequate measures must be taken in order to ensure that the pivot concept can handle the final geometries of the turbine towers. Denne masteroppgaven er en videreutvikling av en konseptstudie for storskala montering av flytende offshore vindturbiner som ble utarbeidet av masterstudentene David W. Moss og Anders Myhr i 2008. Det blir i denne oppgaven fokusert på identifisering av ugunstige lastsituasjoner for på den måten å verifisere konseptets realiserbarhet. Undersøkelsene baserer seg på offshore sammenstilling og montering av flytende vindturbiner ved hjelp av en halvt nedsenkbar plattform. Fire ulike vindturbinkonsept er blitt kontrollert med tanke på montering i vanskelige værforhold. Det settes som mål om å oppnå operasjonsvilkår 90 % av tiden i Nordsjøen. Det er foreløpig få studier tilgjengelig innen storskala sammenstilling og montering av flytende offshore vindturbiner. Framtidige havvindparker vil være plassert i værharde områder noe som vanskeliggjør konvensjonelle løft og tauing på en rasjonell måte dersom en vesentlig monteringsfrekvens ønskes oppnådd. Bruk av ballastkontroll for oppretting av konstruksjoner er en velkjent teknologi i offshorebransjen. Utnyttelse av denne teknologien med tanke på montering av flytende offshore vindturbiner er ikke blitt utredet i større grad og vil kunne ha et stort potensial. På dette tidlige stadiet er det uvisst hva slags turbinkonsept som vil vise seg å være mest konkurransedyktig i framtiden. Derfor vil det være et mål for monteringskonseptet å kunne tilpasses ulike geometrier og massefordelinger. Et annet mål for oppgaven er å innlemme store deler av monteringssekvensen på monteringsplattformen. Det er et ønske om å utføre alt fra sammenstilling av tårn til ankerhåndtering på plattformen. Pivoteringskonstruksjonen, som er oppkalt etter den Romerske vindguden Aquilo, er utarbeidet slik at den i hovedsak overfører opptredende laster ved hjelp av direkte aksialspenninger. Videre er det forsøkt å begrense antall elementer og knutepunkt i konstruksjonen. Dette er krevende da balansegangen mellom fordeling av vekt i horisontalposisjon og evnen til å ta opp bølgebelastning fra turbinflyteren i vertikalposisjon stiller store krav til de ulike konstruksjonsdelene. Verste lastsituasjon oppstår som følge av ekstreme operasjonelle bølger i Nordsjøen og ugunstig dynamisk respons fra den halvt nedsenkbare monteringsplattformen. Foreløpige resultater viser at pivoteringskonstruksjonen oppfører seg som tiltenkt. Fleksibiliteten for montering med ulike plattformer er ikke undersøkt i detalj, men belastning og respons bør være mindre både på Aquilo og turbintårn. Det viser seg at et turbinkonsept med liten dypgang vil være mindre avhengige av værforhold og dermed mer rasjonell med tanke på montering. Når det gjelder vurdering av ulike turbiner har konseptet vist seg å være fleksibelt med tanke på ulikheter i flyter‐ og tårngeometri.