Weather Downtime service to optimize the planification of operations at sea
In order to prepare the commissionning and to assess the time during which the various equipments will be needed, RTE requested NOVELTIS to build a tool giving an easy access to weather standby statistics for each offshore wind farm.
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Weather Downtime service to optimize the planification of operations at sea
Project details
Categories:
In order to prepare the commissionning and to assess the time during which the various equipments will be needed, RTE requested NOVELTIS to build a tool giving an easy access to weather standby statistics for each offshore wind farm.
The weather Downtime calculation interface
Examples of graphs included in the Weather Downtime studies
NOVELTIS implemented a precise and reliable system enabling:
- The assessment of nearshore and offshore metocean conditions for each site and the construction of time series for wind, waves and currents over a 19 year period ;
- The determination of thresholds and operating conditions to assess the Weather Downtime, both onshore and offshore ;
- For each point, the assessment of the number of workable occurrencies, i.e. the periods during which all conditions are met. This work was carried out for each month, day and hour throughout the latest 19 years. This number of occurrences constitute the « Working Window », that is to say, the number of times when all nessary conditions were met.
Means used
The expression « Weather Downtime » or « Weather Standby » defines the percentage of time that is not workable during a defined period.
This period can be daily, monthly or yearly and it depends on the type of project that is contemplated. It is also necessary to precise the environmental thresholds beyond which it is considered impossible to work. Talking about offshore activities, the constraints on work time have mainly to do with thresholds on waves height, wind speed or currents.
In addition, the preferences or operational constraints given by the operator must also be integrated. They can be:
- The day/night light conditions ( taking into account the time of sunrise and sunset), if applicable ;
- The total duration of on site operations ;
- The period to be studied : a precise month or the whole year ;
- The unsplittable operations (that must get enough time for completion once initiated).
Hence, knowing the environmental thresholds and the prefered operating conditions, it is possible to determine precisely, based on a long time series of metocean parameters, the percentage of time during which work at sea won’t be possible, for each month. The best window of opportunity can also be determined, waiting on weather (WOW).
Results
The NOVELTIS system provides a precise and user-friendly calculation of the Weather Downtime.
Once the acceptable threshold metocean values (waves, wind, currents) are keyed-in, the Weather Downtimes comes out instantly i.e. the number of days that need to be added to the project duration to allow for immobilisation due to weather conditions. The result is expressed as a probability of occurrence : P0, P50, P75, P90, P100.
