A large proportion of European offshore wind projects have been subject to delays in both their planning and construction phases. Prime development locations are determined by high wind speeds making installation of components difficult during the notoriously limited construction windows. Analysis of a number of European projects that have been fully commissioned or are currently under construction was undertaken by 4C Offshore in order to highlight the main causes of delays to construction schedules and completion dates. These causes continue to be an important factor in the development of future projects as developers hope to minimise unforeseen problems through the lessons learnt at neighbouring projects.
The capacity of upcoming European projects, and the investment required in the stages leading to construction, means that developers carry a significant risk of return income being diluted by unexpected complexities. As a result, employment of more thorough contingency planning, wider installation windows and mitigation strategies are being used in order to reduce the likelihood of difficulties impacting already costly projects. When reviewing delays across Europe it can be seen that most issues arise regularly, however the ways in which they are dealt with vary significantly.
The main catalysts of delays were found to be:
Winter months are increasingly being omitted from construction schedules in order to minimise delays. The advancement of wind, current and wave modelling has allowed developers to utilise project specific equipment and vessels which are much less likely to incur non-operating days. The majority of installations aim to take place between March and October where conditions are more favourable, however if this slips into the winter months new vessels may need to be chartered (at a spot rate cost) or operations may have to halt completely in order to comply with environmental restrictions.
Vessel scheduling and the associated problems have proved to be one of the most common causes of delays. Contracts for specialist installation vessels are regularly in place two years prior to their requirement on site. Due to the need for these vessels to have a high utilisation rate, operators leave very little room for project overruns. In addition, a number of vessels are limited by their operational capability, meaning that installation may be pushed into the winter months, during which the scheduled vessel is unable to operate. Greater Gabbard saw several weeks of delays after installation vessel MPI Adventure was delivered from her Chinese shipyard three months later than planned. Vessels therefore have a substantial impact on project finances, as seen at London Array: delays in the delivery of the export cable amassed standby vessel costs of 12.1 million GBP.
OVERSIGHTS IN THE SURVEY AND INVESTIGATION STAGES
Pre construction surveys have a profound impact on the perceived technical challenges that will be encountered during the installation phase, as timetables are built around the conditions expected to be encountered. Unexpected soil types or environmental habitats can significantly delay progress whilst developers source new contractors, equipment or licensing approvals. This has been highlighted recently with the discovery of World War II munitions at a number of European projects including 108MW Riffgat and 576MW Gwynt Y Môr. In addition, the latter project has also been subject to array cables installation delays due to unexpected sediment types.
COMPONENT FAILURE OR DAMAGE
Manufacturing defects and damage during installation combined with lengthy component lead times can push project completion dates into the future by many months. UK project Greater Gabbard was subject to problems with the quality of foundations and damage to array cables which substantially inflated costs and construction schedules, with the offshore installation period spanning almost three years. In 2010, a design fault with the grouting mixture used to secure transition pieces to foundations had an impact on a large number of projects, with DONG Energy alone quoting 164 turbines as being affected in both Denmark and the United Kingdom. Such widespread problems can extend construction periods whilst inspection and insurance teams assess damage and claims for compensation from relevant contractors can be sought.
INSOLVENCY AND CONTRACTING
Large contract values, high operating costs and long lead times have led to a number of global contractors to collapse part way through design, supply and installation activities. The time and cost associated with retendering and finding new contractors or equipment can be substantial, especially at short notice when many key suppliers in the sector are working at full capacity. A number of projects have sourced new cable and turbine installers part way through an installation campaign, as recently seen with array cable installation at 288MW German project DanTysk.