A wind turbine is a large machine that looks like a cross between a windmill and a giant airplane propeller. Power companies use it to transform the kinetic energy of the wind into electricity. Many turbines together make up a wind farm.
We will answer the following questions in this article: Where can offshore wind farms be found? How are they operated? Finally, we will also consider how weather forecast services can help.
Because successful offshore wind farm operations rely on efficiently managing the weather window, energy companies depend on sophisticated weather forecasts.
DTN Offshore Forecast Services empower wind farms to plan better and efficiently handle weather risks.
Where can offshore wind farms be found?
Offshore wind farms are comparatively new to the United States. Rhode Island is the first offshore wind farm in the United States, located off the coast of Block Island, and started in December 2016. According to The U.S. Department of Energy’s Wind Vision Report, by 2050, wind could be a feasible source of renewable electricity in all 50 states.
Ideally, offshore wind turbines are found at a site shallow enough for the turbines’ foundations to be fixed to the sea bed easily. The field of operation should also be spacious enough to accommodate hundreds of turbines, some of which can be almost 200 meters, or over 600 feet, tall. This offshore location should also have consistently powerful enough winds to rotate the blades of these massive turbines.
Assessing the wind resource of an area involves determining the potential energy contained in the wind. The wind speed, temperature, pressure, and humidity must all be measured. There must be a sufficient amount of data collected, at least a year’s worth, to indicate average wind speed properly.
Offshore turbines weigh up to 400 tons which is similar in weight to that of a jumbo jet. Their foundations are positioned underwater, well below the waves. The standard wind turbine has a horizontal axis.
Materials used to build the turbines must be strong and stable. The usual construction materials are steel and fiberglass. Fiberglass has the perfect combination of qualities needed; it is light enough to spin in the wind and strong enough to stand up to powerful winds without breaking.
Methods used to stabilize the foundation will depend on the turbines’ location — offshore or onshore. Fixed foundations offshore are only feasible when the water depth is less than 50 meters. Beyond this depth, fixing the foundations to the seabed becomes impractical.
New developments allow for the possibility of having floating offshore wind turbines, those without a foundation, in deeper waters. For example, the Hywind project in Scotland is presently trying out floating foundations in water up to 120 meters in depth.
Similar to fixed foundations, there are several different floating platform designs. There are three types:
- A semi-submersible platform
- A spar-buoy system
- Tension-leg platforms
In each classification, foundations are fixed to the seabed with tethers or anchors.
How are they operated?
Each wind turbine has a “wind vane” mounted on top. The wind vane is connected to a computer and turns the turbine to face the wind. As the wind blows, causing the turbine’s blades to turn, the main shaft that holds the blades rotates.
The blades rotate at a constant speed of between 15-20 revolutions per minute on some turbines. On others, the speed may increase and decrease according to the wind speed.
Turbines catch the wind with blades that look like airplane propellers. In most cases, two or three blades are mounted on a shaft forming a rotor. Turbines with two blades are cheaper, lighter, and easier to install.
The wind causes a combination of lift and drag on the turbine’s rotor-like blades, making the rotor spin like a propeller. Located at the top of the turbine behind the blades is the nacelle, which houses the gearbox and generator.
The gearbox transfers the rotational speed of the main shaft to a high-speed shaft that drives the generator. Electricity is then produced by electromagnetism, the effect of a magnet spinning past coils of conductive wire.
The resulting electricity is transmitted by cables buried in the seabed to an offshore substation. Once the electricity reaches this offshore substation, it is then stepped up to a higher voltage and transferred to an onshore substation through high voltage cables.
From there, it enters the National Grid, providing millions of people with clean electricity. The generated energy from a single wind turbine can power up to 600 homes.
Weather impact on offshore wind farm operations
Have you ever noticed a wind turbine not moving even on a windy day? There are different possible reasons for this. It could be that the turbine is down for routine maintenance or that the winds are too strong to operate safely.
The weather has a significant impact on the day-to-day operations of a wind farm. Let’s go through a few examples.
Of course, the first step to operating your offshore wind farm is reaching it. Sending a crew out on a small vessel relies upon understanding the current weather conditions, as well as accurately forecasting the weather upon your crew’s return.
There are many moving pieces that are in place to ensure that a wind farm is operating effectively and efficiently. Those pieces of equipment need routine and preventative maintenance to ensure that things are running smoothly.
That maintenance needs to take place in such a way that keeps your personnel safe. Therefore, savvy operational professionals will be looking at weather conditions before sending their staff into a potentially dangerous situation. Knowing about lightning risks, for example, is a key piece of information your technician would need before climbing atop a steel tower!
Additionally, wind speeds will vary. It is simply wasteful to schedule routine maintenance at a time when wind speeds are high and a high level of output is expected from the turbines. Missing a weather window in which there are low wind speeds is a costly mistake.
Wind farms’ geographical placement is designed to capitalize on wind speed and strength. That placement and changing weather, though, means that wind speed variability is inevitable. This variability could even result in the sudden shut down of a whole wind farm during severe weather.
However, being able to plan for those weather inconsistencies would allow for maintenance to be conducted during low wind times. It could also mean shutting down operations carefully before severe weather strikes.
No doubt, you can make the connection between the efficient operation of an offshore wind farm and the wind farm’s access to reliable and detailed weather forecast data with expert analysis.
It may only give a small advantage day by day, but pretty soon, that adds up to enormous financial gains, especially when measured over the offshore wind farm’s life cycle.
DTN Offshore Forecast Services empower wind farms to handle weather risk, plan better and execute operations by managing the available weather window.