The document describes the BLACKBIRD, a proposed hybrid vertical axis wind turbine and wave energy converter attached to a tension leg buoy floating platform. It is at an early technology readiness level of 2. The BLACKBIRD aims to combine existing vertical axis wind turbine, wave energy converter, and tension leg platform technologies to harness both wind and wave energy offshore. It would be anchored to the seabed using a rock-anchored foundation template to provide stability. The design seeks to significantly reduce levelized costs of energy production for offshore wind compared to traditional offshore wind farms using fixed bottom or shallow draft floating turbines.

1. BLACKBIRD: Storage Base Single Anchored Uniaxial Hybrid Vertical Axis Wind Turbine [VAWT]
and Wave Energy Convertor [WEC] on Tension Leg Buoy – AWEA Offshore Rhode Island 2016
Summary
Early developments in Offshore Wind [OW] have been in shallow
water, primarily the southern North Sea, with turbines up to 8 MW
founded on steel monopiles or piled truss towers (“jackets”). There are
increasing indications that Floating Offshore Wind Turbine [FOWT]
array size projects could become commercially viable beyond 2020.
The feasibility of Vertical Axis FOWT and Wave Energy Convertor [WEC]
technology is at an early stage, but costs are expected to reduce. WEC
development has been patchy and irregular Prototypes are undergoing
long term testing to prove reliability, operability and durability [4].
Dr.C.R. Golightly, BSc, MSc, PhD, MICE, FGS .Geotechnical and Engineering Geology Consultant, Rue Marc Brison 10G, 1300 Limal, Belgium, Tel: +32 10 419525 Mobile: +32 478 086394 e-mail: chris.golightly@hotmail.com
skype:chrisgolightly Linked In: www.linkedin.com/pub/5/4b5/469 Twitter: @CRGolightly Academia.edu: https://independent.academia.edu/ChristopherGolightly
“You Pay for a Site Investigation - Whether You do One or Not”– Cole et al, 1991. “Ignore The Geology at Your Peril” – Prof. John Burland, Imperial College.
References
1. Beerens, J.: Offshore Hybrid Wind-Wave Energy Converter System: A Frequency Domain Approach,
M.Sc. Thesis, TU Delft, p. 145, February 2010.
2. Carbon Trust: Innovation in Offshore Wind: International Collaboration and Coordination”, All Energy
2015, Glasgow, UK, p. 32, 2015.
3. DNV-KEMA: The Crown Estate – UK Market Potential and Technology Assessment for Floating Offshore
Wind Power; An Assessment of the Commercialisation Potential of the Floating Offshore Wind Industry,
Rev. 01, 21st December 2012, Ref. 2012-1808, p.24, 2012.
4. Drew, B., Plummer, A.R. and Sahinkaya, M.N., A Review of Wave Energy Converter Technology, Review
Paper 782, Proc. IMechE Vol. 223 Part A: J. Power and Energy, DOI: 10.1243/09576509JPE782, 2009.
5. Feng, N., Yu, H., Hu, M., Liu, C., Lei, H. and Shi, Z.: A Study on a Linear Magnetic-Geared Interior
Permanent Magnet Generator for Direct-Drive Wave Energy Conversion, Energies 2016, 9, 487.
6. Garg, A., Lay, C. and Fullman, R.: The Feasibility of an Underwater Pumped Hydro Storage System. IRES
12th November 2012, p. 12, 2012.
7. Golightly, C.R.: Efficient Anchored Template Foundations for Offshore Wind Turbines [OWT], EWEA 2013
8. Mørk, G., Barstow, S, Kabuth, A. and Pontes, M.T.: Assessing the Global Wave Energy Potential, Proc.
OMAE2010 29th Int. Conf. Ocean, Offshore Mechanics and Arctic Engineering, June 6th -11th, 2010,
Shanghai, China. Paper No. OMAE2010 – 20473, 2010.
9. Muliawan, M.J., Karimirad, M., Moan, T., Gao, Z.: STC (Spar-Torus Combination): A Combined Spartype
Floating Wind Turbine and Large Point Absorber Floating Wave Energy Converter - Promising and
Challenging. In: Proc. Int. Conf. Ocean, Offshore & Arctic Engineering (OMAE), Rio de Janeiro, 2012.
10. Myhr, A. and Nygard, T.A.: Experimental Results for Tension-Leg-Buoy Offshore Wind Turbine Platforms,
Journal of Ocean and Wind Energy, ISOPE, 1, 4, November 2014, pp. 217–224, 2014.
11. Paulsen, U.S., Borg, M., Madsen, H. A., T.F. Pedersen, Hattel, J., Ritchie, E., Ferreira C.S., Svendsen H.,
Berthelsen P. A., Smadja, C.: Outcomes of the DeepWind Conceptual Design”, Energy Procedia 80, pp.
329 – 341, 2015.
12. SI Ocean: Wave and Tidal Energy Strategic Technology Agenda, February 2014, p. 44, 2014
13. Slocum, A. H., Fennell, G.E. and Dundar, G.: Ocean Renewable Energy Storage (ORES) System: Analysis of
an Undersea Energy Storage Concept, Proc. IEEE, 101(4): pp. 906–924, 2011.
14. White, C.N., Erb, P.R. and Botros, F.R.: The Single-Leg Tension-Leg Platform: A Cost-Effective Evolution of
the TLP Concept”, Proc. 20th Offshore Technology Conference, Houston, 1988, Vol. 1, p.8, 1988.
Seabed Anchored Foundation Template [SAFT]
SAFT [7] is a buoyant floated-out hybrid GRP/reinforced concrete
subsea foundation designed to support tripods, jackets or GBS or pre-
installed for taut (TLP) or catenary mooring lines/tethers templates.
Steel or concrete edge skirts, suction caissons [SC] , anchor piles or
helical screw are options available for a wide variety of different soil
overburden types and thicknesses and geological rock strata.
Tensile pressure grouted, fully proof loaded single or multi-strand
rock anchors are installed through support casing, using an ROV
marinised drilling unit. External GRP, concrete or steel mudmats and
integral plastic anti-scour frond mats/mattresses provide support
and scour protection. The SAFT unit has high lateral load resistance
and tension uplift capacity, especially anchored into bedrock.
Design is preceded by high quality seabed geophysical investigation
followed immediately by confirmatory geotechnical soil and rock
coring, with the same ROV drilling unit used for anchor installation.
1. Twin bladed Carbon Fibre Vertical Axis
Wind Turbine [VAWT]
2. VAWT Generator
3. Anti Yaw Swivel Bearing
4. WEC Power Take Off [PTO] Unit
Integrated into Floater.
5. Composite Heave Plate Wings
6. Linear Magnetic-Geared Interior
Permanent Magnet Generator
[LMGIPMG] [5]
7. Inner Stationary Stator Coils
8. High Buoyancy Uniaxial Submerged
Tension Leg Buoy [USTLB]
Combined wind-wave energy potential is enormous [3,8,12],
Recent work on hybrid concepts [1.4] is only theoretical but
promising. The TRL level 2 BLACKBIRD is a potential “gamechanger”
VAWT-WEC uniaxially tethered hybrid, a synergy of existing VAWT,
WEC combinations and PTOs [5,9,11], TLP/TLB mooring [10,14] and
local pumped energy storage [6,13] concepts. Fig. 2 shows the
energy potential existing off the NW coasts of Europe.
European Offshore Wind – Need to Reduce Rising Costs
The majority of European OW turbines installed or planned in the
German, UK and Danish sectors of the North Sea have been scaled up
conventional onshore triple bladed horizontal axis wind turbines
[HAWT], founded mainly on large diameter (4 to 8 m) steel monopiles
(WD <35m) or piled tripods/jackets (WD ~ 30 to 55m), with some
concrete GBS. Costs must be halved or more for industry survival
without subsidies. CAPEX rose between 2005 and 2010 (Fig. 1).
9. Tension Leg Buoy Bottom Connector
10. Single Vertical High Capacity
Damped Tether/Tendon.
11. Subsea FRP “Green” Concrete
Storage, Pump& Electrolysis Unit.
12. Subsea Ball & Taper “Plug-In”
Seabed Connector
13. Seabed Rock Anchored Foundation
Template [SAFT]
14. Export HVDC Power Line plus Gas
Pipeline.
15. Grouted Rock Anchors and Suction
Caissons
Figure 3 – BLACKBIRD - Summary
LCOE: from > 200 USD/MWhr
to ~ 50 USD/MWhr
Figure 1 – Reducing LCOE [USD per MWHr]
Sources: Carbon Trust [2]; Bloomberg New Energy Finance
Figure 2 – European Combined Wind & Wave Energy Potential
Source: ORECCA
Dr. C.R. Golightly, BSc, MSc, PhD, MICE, FGS.
Geotechnical and Engineering Geology Consultant, Belgium