Rob Harrison  
Weather forecasting can make a vital contribution to the pre-construction process for wind farms, writes Rob Harrison, head of Renewables at the Met Office.
Rob Harrison

Weather patterns and forecasting intelligence are critical when planning ahead for wind farm site construction.

Access to accurate weather forecasts enables engineers to pinpoint an appropriate weather window for the various phases of construction, which help them to reduce the potential for extended downtime and ensure the safety and wellbeing of staff and contractors.

Both onshore and offshore, the variability of wind and climate can pose challenges for managing that risk. But offshore projects require even more forecasting input at their construction stage as they involve greater risk.

The role of the Met Office is to work with the construction company to help it effectively plan and manage construction and financial procedures through providing a site specific knowledge of the weather and climate. For the construction company, using a weather forecasting service helps mitigate the weather risks that can present various challenges for any given installation. The key challenges include:

  • safeguarding the health and safety of employees;
  • ensuring ease of access to construction sites;
  • getting the planning right;
  • tendering at the right level;
  • bringing the construction in on time and on budget.

Long-term forecasting, a year ahead of the start of construction, is important for the planning and budgeting of a complex project. As the project moves towards the construction phase, forecasting needs to be factored in for balancing probabilities and their associated risk, such as likely downtime periods, typical conditions and equipment required.

In the short term, accurate forecasts facilitate operational decisions by enabling developers to identify the potential for construction on any given day.

On the day the operations team may rely on real-time advice from onsite experts, who can provide information on changing conditions, such as lightning risks, to help construction site managers make informed decisions on whether operations need to be suspended and construction staff brought down to safety.

Challenging environments

One of the biggest challenges facing the whole industry is the natural variability of the weather.

Met Office's web-based solution afesee
Designed specifically for the marine and offshore industries, the Met Office’s web-based solution afesee™ provides forecast data values for weather and wave parameters for up to five days ahead, enabling clear weather windows to be identified swiftly.

The offshore wind power industry is one of the fastest growing areas in the renewable energy market. Yet it suffers from a limited availability of suitable long-term wind reference data for assessing offshore wind resources. The challenges to be overcome include:

  • calculating coastal effects for near-shore projects;
  • capturing spatial variability across large areas of ocean;
  • defining the optimal site for real met masts to ensure maximum effectiveness.

And as wind projects move further and further offshore into deeper and more exposed waters, many of these challenges are further compounded for wind farm construction companies.

Design and planning around these issues can be difficult, as quality assured wind and weather observations are sparse in certain offshore areas, while new observational campaigns are both expensive to set and cannot immediately provide a useful dataset. The key to success is ultimately in the careful planning and understanding of the environment in which operations have been planned.

The need to forecast the impact of varying weather and sea conditions, such as thunderstorms, fog, low cloud, wave height, energy and swell duration, differs during the period of execution for each stage of an operation. Each element of an installation will have a different weather limit, a change of just 0.1 metres can be critical to an operation that depends on wave height, and weather downtime can mean a specific stage of the operation is off limits.

The weather window is critical to the success of the operation and can be tense for all involved. Everyone understands the forecast details, but what project managers want is the bit between the lines. The trust and confidence offered by being physically offshore with the operations team cannot be underestimated – it is a significant factor in the overall success of the operation, especially as uncertainties change.

The financial cost of weather downtime is not the only important consideration for offshore operations. The health and safety of the employees involved is of paramount importance.

The appliance of science

At the Met Office we apply our investment in science and research to develop wind intelligence tools that help the industry accurately assess the wind, to support all stages of development in the business life cycle of the wind farm – from site search and selection, through development and construction to operations and maintenance.

It is fundamental that we drive scientific research into wind resource assessment so the renewable energy industry can be informed about past wind patterns, future trends and how they might manage wind variability risk.

Safesee's graph display
Safesee’s™ graph display has been configured to enable the option to overlay observational data for wind and wave, and probability forecasts out to 15 days ahead, over site-specific forecasts.

Investment in science is increasing industry insight and understanding of the climatology and risks associated with wind assessment. We are starting to see the potential in long-range forecast systems, which in the future will enable us to map trends and put some certainty around climate variability.

Current rates of advance in computational power have led to enormous improvements in the sophistication of atmospheric, ocean and wave models that deliver such data. For example, present capabilities enable decadal runs of mesoscale (order 10 km) atmospheric and wave models that can accurately represent local wind and wave fields in continental shelf-seas and how they impact on marine operations.

Most modern offshore projects have been developed using 2–3 MW machines. Future projects are expected to use 3–7 MW machines, to take advantage of higher wind speeds, resulting in an increase in energy production.

The ability to map wind variations over time, even decadally, means we can more easily identify which areas within Europe have the greatest wind speeds and long-term resource. This can benefit the industry when it comes to making more informed decisions about identifying and constructing sites for wind turbines.

Identifying the weather window

Forecasting capability is invaluable at the construction phase, not least for providing weather tolerance thresholds for completing foundations, or calculating wind speed at crane height, or the risk of lightning when installing and lifting a turbine onto a pile.

The Met Office was closely involved in providing on-site forecasters for the Beatrice Wind Farm Demonstrator Project, led by Talisman Energy (UK) and Scottish and Southern Energy, to assist with weather sensitive operations. We provided the weather forecast advice for identifying a suitable weather opportunity for installing the jacket and turbines.

Construction companies are familiar with working in harsh conditions, but the geography of offshore wind farms will set even tougher challenges as they move further and further offshore, where variability of weather and marine conditions will be even greater.

We are working on the science that will enable us to enhance the forecasting aspects with future modelling. Increases in supercomputing capability will allow more skilful forecasting and enable us to produce models with finer resolutions to see what drives large-scale climate processes and patterns.

www.metoffice.gov.uk/marine

www.metoffice.gov.uk/renewables/