Subhub Completes Commissioning

QED Naval have completed the commissioning of all onboard ballast and instrumentation systems ready for testing and launch early in 2018. This community version is a big step to proving the claims about competing with offshore wind for CFDs at utility scale.

QED Naval is working with Schottel Hydro on this 190kW version which is competitive, in terms of LCOE, with diesel generation for island communities’ or offshore power generation for aquaculture offering excellent niche market opportunities recently forecast by Aquatera.

However, Subhub was always designed for utility scale projects, removing the requirement for large specialist vessels at expensive day rates and multiple marine operations offshore. Where Subhub requires only a single offshore operation using smaller vessels and/or barge at low day rates.

Fundamentally, the concept of Subhub using buoyancy and good submerged stability to install the turbines scales very well. Also, the ballast ratios, for the required on-bottom weight to secure the turbines on the seabed, scales in their favor. The utility version is more slender and uses simpler construction methods reducing fabrication costs still further enabling the acceleration effects of the semi-duct to be applied to every turbine. QED’s latest CFD models when combined with a tidal harmonic models for the site and power curve of the tidal turbine show increases in yield of up to 50% year on year when compared with typical monopile structures. Subhub effectively increases the capacity factors of the site.

An independent report by a Master Mariner has stated that installation and recovery costs of a utility scale Subhub can be reduced by 50 to 90% compared with current methods. The seaworthy design, stability when submerged and the control of the ballasting process make the Subhub less sensitive to wave loading during installation. This allows it to be installed and recovered over broad weather windows and hence the availability for maintenance is higher. This attributes a large reduction in maintenance costs.

QED Naval pride themselves on the understanding of the combined effects of wave and tidal loading learning huge amounts from their tank testing at Flowave, open water testing at The Underwater Centre in Loch Linnhe. Their collaborations with EMEC/FORESEA, and QUB as part of the Tidal Turbine Turbulence (TTT3) project have provided unrestricted access to real measured tidal data using ADCP systems for accurate tidal modelling and turbulence measurements. QED’s work on turbulence modelling in collaboration with the National Oceanographic Centre (NOC) is thought to be class leading and provides more assertive results for energy yield calculations.

All this learning has been combined into Monte Carlo simulations for various projects QED have assessed which provides a sound basis to presenting the LCOE figures and making project finance decisions.

All these claims will be assessed in the next stage of testing to be commenced early 2018.

 

Aft view of Subhub showing tripod leg structure and semi-duct for accelerating the tidal flow into the turbine.