A2SEA
A Danish offshore wind installation and marine services company that was integrated into DEME Offshore.
Last updated August 22, 2026
AI crawler reads
No AI crawler has read this profile since Oct 28, 2026.
Overview
A2SEA was a Danish offshore wind installation and marine services company headquartered in Fredericia. Established in 2000, it developed around the practical requirements of building offshore wind farms: transporting large turbine components from port to sea, lifting and installing turbines in demanding marine conditions, and supporting construction and servicing activities after installation. Rather than selling turbines or generating electricity, A2SEA operated as a specialist engineering and marine-construction contractor for wind-farm developers, utilities, turbine manufacturers and other project participants. The company’s early development was closely associated with the expansion of European offshore wind. In 2001, two vessels, M/S Ocean Ady and M/S Ocean Hanne, were converted for turbine-installation work; they later operated under the names Sea Energy and Sea Power. A2SEA carried out its first installation work at the Horns Rev 1 offshore wind farm in the North Sea in 2002. It subsequently worked on projects including Frederikshavn, Nysted, Arklow Bank, Scroby Sands, Kentish Flats and Thanet, and secured installation contracts connected with the London Array and Ormonde wind farms. These projects helped establish the company as a specialist in the transport, lifting, installation and marine coordination required for offshore turbines. A2SEA’s operating model depended on a dedicated fleet and associated offshore equipment. Its vessels included the semijack-up vessels Sea Energy and Sea Power and the jack-up vessels Sea Jack and Sea Worker. In 2010, the company ordered Sea Installer, described in the reference material as its first purpose-designed wind-turbine installation vessel. The fleet enabled A2SEA to work in the construction phase of offshore wind projects and to provide related support services, including marine operations associated with servicing and maintenance. Ownership changed as the offshore wind market matured. Danish energy company DONG Energy acquired A2SEA in 2009. In 2010, Siemens Wind Power was announced as a prospective 49% shareholder in a transaction valued at DKK 860 million; regulatory approval was granted on 13 October 2010. The reference material reports turnover of DKK 586 million and profit of DKK 86 million for 2010. In 2017, A2SEA was sold to GeoSea, the Belgian offshore installation company belonging to DEME Group. DEME later reorganized its offshore activities: in 2019, GeoSea, Tideway and A2SEA were integrated into DEME Offshore. As a result, A2SEA no longer operates as an independent company or standalone corporate brand. Its historical significance lies in its role as an early specialist contractor in Europe’s offshore wind installation sector and in the development of dedicated vessels for that market.
History
A2SEA was established in Denmark in 2000 as the offshore wind industry was beginning to develop into a specialized European infrastructure market. Its business addressed a bottleneck in wind-farm construction: turbines had to be moved from port to offshore sites and installed using vessels capable of operating in shallow, exposed and technically demanding marine environments. A2SEA therefore positioned itself as a marine engineering and installation contractor rather than as a turbine manufacturer or electricity producer. In 2001, the company converted M/S Ocean Ady and M/S Ocean Hanne for turbine-installation work. The vessels later became known as Sea Energy and Sea Power. A2SEA’s first installation work was performed at Horns Rev 1 in the North Sea in 2002. The project was an important early offshore wind deployment and gave the company practical experience in coordinating vessel operations, turbine components and offshore construction activities. During the following years, A2SEA installed turbines or performed installation work on a number of European projects. The reference material identifies Frederikshavn, Nysted, Arklow Bank, Scroby Sands, Kentish Flats and Thanet among the company’s projects, while also noting contracts for the London Array and Ormonde offshore wind farms. This project portfolio reflected the geographic spread of early offshore wind development across Denmark, the United Kingdom and Ireland. The company’s capabilities covered transport, lifting, installation and related servicing of offshore wind farms. A2SEA’s fleet was central to its identity. It operated two semijack-up vessels, Sea Energy and Sea Power, and two jack-up vessels, Sea Jack and Sea Worker, all specially converted or configured for offshore wind turbine installation. In 2010, the company ordered Sea Installer, described in the source material as the first purpose-designed wind-generator installation vessel in its fleet. The move illustrated the industry’s transition from adapting existing marine assets toward purpose-built offshore wind infrastructure. The ownership structure evolved alongside the industry. DONG Energy acquired A2SEA in 2009. In 2010, Siemens Wind Power announced an agreement to acquire a 49% stake for DKK 860 million, subject to regulatory review; approval was granted on 13 October 2010. The source material reports 2010 turnover of DKK 586 million and profit of DKK 86 million. These figures are historical and are included only for that stated year. In 2017, A2SEA was sold to GeoSea, a Belgian offshore installation company that was part of DEME Group. The acquisition placed A2SEA within a broader offshore engineering organization. In 2019, DEME consolidated GeoSea, Tideway and A2SEA into DEME Offshore. Following that integration, A2SEA ceased to function as an independent company and standalone brand. Its legacy is associated with the early professionalization of offshore wind installation, the use of specialist vessels and the expansion of marine engineering services supporting European offshore wind farms.
- 2019
Integrated into DEME Offshore
[1]DEME integrated A2SEA, GeoSea and Tideway into DEME Offshore.
- 2017
Sold to GeoSea
[1]A2SEA was sold to GeoSea, a DEME Group offshore installation company.
- 2016
Sea Worker accident
[1]Sea Worker was grounded off Nymindegab after its tow cable broke during bad weather and capsized roughly one week later.
- 2010
Siemens Wind Power stake announced
[1]Siemens Wind Power announced the planned acquisition of a 49% stake in A2SEA for DKK 860 million; regulatory approval followed on 13 October.
- 2010
Sea Installer ordered
[1]A2SEA ordered Sea Installer, identified in the reference material as its first purpose-designed wind-turbine installation vessel.
- 2009
Acquired by DONG Energy
[1]DONG Energy acquired A2SEA.
- 2002
First installation work at Horns Rev 1
[1]A2SEA performed its first offshore wind installation work at the Horns Rev 1 wind farm in the North Sea.
- 2001
First turbine-installation vessel conversions
[1]M/S Ocean Ady and M/S Ocean Hanne were converted for turbine-installation work and later operated as Sea Energy and Sea Power.
- 2000
A2SEA established
[1]A2SEA was established in Denmark as an offshore wind installation and marine services company.
Products and positioning
Specialist offshore wind installation, marine transport and offshore engineering services provider
Offshore wind installation vessels · 2001
Sea Energy and Sea Power
Formerly M/S Ocean Ady and M/S Ocean Hanne, these vessels were converted in 2001 for offshore wind turbine installation. They formed part of A2SEA’s early installation capability and were used to support the transport and offshore erection of turbine components.
Jack-up marine vessels
Sea Jack and Sea Worker
Jack-up vessels in A2SEA’s installation fleet, configured for offshore wind construction and turbine-related marine operations. Sea Worker was later involved in a grounding and capsizing incident off the Danish coast in 2016.
Purpose-designed installation vessel · 2010
Sea Installer
Ordered in 2010, Sea Installer was described as the first purpose-designed wind-generator installation vessel in A2SEA’s fleet. Its role was to support the lifting and installation of offshore wind turbines and major components.
Engineering services
Offshore wind installation services
A2SEA provided marine transport, lifting, turbine installation and offshore construction execution for wind-farm developers and project partners. The service depended on specialist vessels, offshore crews and coordination of large turbine components in marine environments.
Operations and maintenance support
Offshore wind servicing support
The company also supported offshore wind-farm servicing and related marine operations, complementing its principal construction and turbine-installation activities.
Brand decisions
2019
Integration into DEME OffshoreStrategyBackground
DEME sought to consolidate its offshore activities and combine the capabilities of several related companies.
Action taken
DEME integrated GeoSea, Tideway and A2SEA into DEME Offshore.
Aftermath
A2SEA ceased operating as an independent corporate identity, with its activities absorbed into DEME’s offshore organization.
2017
Sale to GeoSeaM&ABackground
A2SEA’s offshore installation capabilities were relevant to GeoSea’s broader marine engineering and offshore construction activities.
Action taken
A2SEA was sold to GeoSea, a Belgian offshore installation company within DEME Group.
Aftermath
A2SEA became part of the DEME Group’s offshore engineering portfolio before its later organizational integration into DEME Offshore.
2010
Planned Siemens Wind Power minority investmentM&ABackground
A2SEA was operating in a rapidly expanding offshore wind market and had become strategically relevant to turbine manufacturers and project developers seeking installation capacity.
Action taken
Siemens Wind Power announced the acquisition of a 49% stake for DKK 860 million. Regulatory approval was granted on 13 October 2010.
Aftermath
The transaction changed A2SEA’s ownership structure and linked the installation specialist more closely with a major wind-turbine manufacturer.
Transaction value. DKK 860 million (2010 announced transaction)
Recent events
- 2019
DEME integrates A2SEA into DEME Offshore[1]
M&A
DEME integrated its offshore companies, including GeoSea, Tideway and A2SEA, into DEME Offshore, ending A2SEA’s independent organizational identity.
- 2017
A2SEA sold to GeoSea[1]
M&A
A2SEA was sold to GeoSea, the Belgian offshore installation company within the DEME Group.
- 2016
Sea Worker grounded and later capsized[1]
Other
The Sea Worker barge was grounded off Nymindegab, Denmark, after its tow cable broke in bad weather. About a week later, the vessel capsized.
- 2010
Siemens Wind Power announced 49% A2SEA stake[1]
M&A
Siemens Wind Power was announced as the buyer of a 49% interest in A2SEA for DKK 860 million. Regulatory approval was granted on 13 October 2010.
- 2009
A2SEA acquired by DONG Energy[1]
M&A
Danish energy company DONG Energy acquired A2SEA, bringing the offshore wind installation specialist under utility ownership.
Sources1 sources
Cite this profile: Cite the canonical profile. /brand-wiki/a2sea · Editorial policy · How profiles are compiled