Shucks! My wind turbine just froze over...(5 min read)
Great title! ;-) Unfortunately, I don't have a wind turbine...?
I’ll provide some background. I recently had a chat with a fellow engineer with a huge amount of experience, and the “frailty” (my emphasis) of wind turbines was mentioned, especially in cold weather conditions. So, I thought, this can’t be right as they’ve been around for ages and have undergone a huge deal of improvement. Here’s my 2 pennies on these “marvels of engineering” (my emphasis, again) … It’s in 3 parts, for easier consumption.?
Interesting fact number 1 – Google search trends (worldwide) shows that searches for the term “wind turbine” peaks around winter / spring for the last 5 years. This makes sense as you read further.?
Part I: Wind, Some history and trends…
Human beings have used wind energy for several millennia. It’s known to have been used to power boats since 5000 bc, wind powered pumps are known to have been used from around 200 bc. The first known electricity generating wind turbine (using cloth sails) was built in 1887 by James Blyth in Marykirk, Scotland. I don’t have pictures of #wind powered boats from 5000 bc but here’s one of James Blyth’s.???
Blyth's "windmill" at his cottage in Marykirk in 1891
Interesting to know – James Blyth offered to power the main street of Marykirk using surplus electricity from the #windturbine, however, this offer was rejected by the towns people as they thought electricity was “the work of the devil!”. Fast forward 134 years later, attitudes are somewhat more relaxed about electricity and wind turbines. As at September 2021, the #UK had a total wind turbine installed capacity (onshore + offshore) of 24,764 MW with Scotland having 38% (9,403 MW) of that!
Hmmm… moving on…
Wind Facts
Interesting fact number 2 – Wind is complicated!
Factors that determine wind include temperatures, pressures, climatic conditions and earth surface obstacles.
The sun heats the air around the equator more than at the poles, this hotter air expands and rises several kilometres (leaving behind a low-pressure area around ground level), into the troposphere spreading northwards and southwards. Around latitude 30o?the air sinks (due to the Coriolis force, it’s worth a geek out on), creating a high-pressure area. These actions create the prevailing (geostrophic) winds which are dominant around 1km above ground level. This boundary is not constant and can be affected by terrain, temperature profile, time of day and seasons.
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Interesting fact number 3 – The higher above ground you go, you get more wind!
These geostrophic (global) winds largely determine the prevailing winds in a given area whilst local / surface winds (impacted by local climatic conditions / obstacles) will dominate when the effects of geostrophic conditions are smaller. Surface winds (especially onshore) are greatly influenced by ground obstacles up to about 100m above ground level, this effect is super important when siting onshore windfarms.
In temperate areas, summer winds are typically weaker in comparison to winter winds. The graph below displays the distribution of average wind speed in the UK with summer months generally having lower wind speeds on average compared to winter months.
The amount of energy transferred to wind turbines is dependent on the following factors:?
This relationship is condensed into the following equation:
Wind Power, P = 0.5 * density (kg/m3) * rotor blade area (m2) * wind speed (m/s)
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Therefore, the wind turbine output will likely be higher in windy, wintery conditions in temperate regions (which is a good thing as there’s also higher energy demand especially for heating). Given the increased potential power generation capacity and the higher #energy demand during winter months it makes sense to ensure equipment downtime is minimised during this period.?
Wind Trends
The last few months of 2021 have seen lower on average, wind speeds in the UK in comparison with previous years, as can be seen in the graph below (up to August 2021).?
Wind is complicated and is not constant, therefore, more innovative generation, transmission and #storage facilities are required to cope with changing generation capacity. One of those innovations is used in Gaildorf, Germany (discussed later).??
UK monthly average wind speed over 10 years
Wind speed / direction is constantly changing (you probably know that already), if you watched a wind turbine on a normal day, you'd see it change velocity (and possibly, direction) quite a bit during that time, to optimise power production. The graphs below display examples of short-term wind variation and diurnal (day / night) wind speed variability.
(Reference:?www.windpower.net )
Wind Turbine Giants
#Power generating wind turbines have come a long way since James Blyth’s time. The tallest operational wind turbine is in Gaildorf, near Stuttgart (as at time of this article but with taller ones planned). It has a total height of 246.5m with a hub height of 178m, with the windfarm at an altitude of 200m above sea level. This one is quite interesting as it actually uses a GE 3.4-137 (3.4MW / 137m blade diameter) wind turbine, but has its foundations raised an extra 40m to contain a water reservoir (acting as pumped water storage). This is used as short-term storage (water battery) for a downstream #hydroelectric power station. The Bains for each wind turbine has a water capacity of 40,000m3 (for a total capacity from 4 wind turbines of 160,000m3). There are existing wind turbines with much longer rotor blades and larger generation capacity but lower base to tip heights.?
Gaildorf wind-water project (https://www.windfarmbop.com/wind-turbine-foundation-as-a-water-battery-the-gaildorf-wind-water-project/)
The advantage of increasing a wind turbine hub height is that, each additional meter of #hub height added to a wind turbine approximately increases the annual energy yield by 0.5 to 1 percent.
Part 2 available soon...
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References:
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3 年Very informative and brings home that they are complicated systems.