This page contains a Flash digital edition of a book.
FEATURE SPONSOR


WEATHER DOWNTIME


CALCULATING WEATHER DOWNTIME Individual operational tasks, such as deploying a particular piece of equipment or mooring on site, may each require a suitable amount of time to complete. During this period there may also be certain metocean parameters (e.g. wave height or wind speed etc.) that must not be exceeded for operability or safety reasons.


Weather downtime information is commonly reported in a generic form (e.g. percentage time in a given month when conditions are likely to be less than a given threshold value for a given minimum duration). When using such generic information, a simple spreadsheet is commonly used to assess cumulative weather downtime for an operation with multiple sub-tasks.


However, such methods make inherent assumptions about the required time order of weather windows. The nature of these assumptions typically leads to an under- estimation of weather downtime for more complex or interrelated task schedules.


In practice an operation usually consists of a number of consecutive and inter- dependent tasks in a specific time order i.e. transiting from location A to B, THEN mooring on site, THEN deploying a particular piece of equipment. In this case, the statistical chance of the required thresholds being met in the correct order is likely to be reduced. Assessments that consider an operation as a set of consecutive tasks in the intended order provide a better estimate of the expected downtime than generic methods.


A robust weather downtime assessment should be informed by many years of hindcast metocean data. Longer data sets give greater confidence that the statistics have adequately captured variability in the metocean climate over time. The spatial/ temporal resolution and the accuracy of the data are, of course, important to ensure that the data and the results of the analysis are representative of the location of interest.


To take account of natural variability from year to year, a range of results is used to provide weather downtime statistics with varying non-exceedance probabilities, typically including P50, P75, P90, Pmean, Pmax (the ‘worst’ year), and Pmin (the ‘best’ year).


WEATHER DOWNTIME EXPRESS CALCULATOR


Developed in conjunction with the offshore wind industry, ABPmer’s Weather Downtime Express service enables 24/7 weather dependent decision making by providing on-demand access to the company’s weather downtime statistics calculator.


The email based system allows authorised users of the software to send a schedule of their operations to be analysed against the company’s exclusive past weather


‘SEASTATES’ archives using a ‘sequential task’ best practice approach. Each task list is processed by the system and the results are returned in a matter of minutes by email.


The calculator can consider any combination of home ports, take account of sequential operations with multiple limiting parameters and process any number of scenarios.


Multiple operations are simulated with start dates/times of every hour in an hourly time series, i.e. the operation is simulated over 300,000 times.


For each task provided, the calculator generates statistics of overall project programme and weather downtime, categorised by start date over the full range of probabilities as well as for each task in the operation.


By creating multiple versions of the task list corresponding to choices of construction/installation methodology, tooling or vessel, a user can rapidly test options for decision making.


Designed to help ABPmer’s clients make quicker operational and risk management decisions, the outputs offer the level of detail needed to optimise schedules or provide tailored and accurate prices when bidding for new work.


ABPmer


Click to view more info Website


Click to view more info Whitepaper


www.windenergynetwork.co.uk


37


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92