Standing up at Commonwealth Bay in Antarctica requires a certain effort of will. The average wind speed there is around 50 miles per hour (mph), but it can regularly reach up to 150 mph. As the force of gravity downwards, which keeps things tethered to the earth, is roughly equivalent to the sideways force of a 120 mph wind, the danger lies in taking off. Some winds have huge energy and an average speed of 60 mph will certainly knock most people over. The highest ever recorded wind speed – 253 mph – was on Barrow Island, Australia in 1996 at an unmanned weather station, yet there may be much higher wind speeds inside numerous tornadoes, hurricanes and typhoons.

What is happening to wind as a result of climate change is a matter of some controversy. Since at a global level wind is the result of the temperature differentials between the poles and the equator, the logic is that wind speeds should decline. This is because we now know that the poles are heating up much faster than the tropics, so that the temperature differential has been declining. A long-term study of this “stilling” from 1978 to 2010 suggested that wind speeds had been declining by 2.3% per decade.

Happily, or unhappily, after 2010, a study by Princeton University suggested that average wind speeds have been increasing from around 7 to 7.4 mph and that they are in fact increasing about three times faster than they were slowing before and that this may accelerate in the later 2020s. Nonetheless, the Intergovernmental Panel on Climate Change (IPCC) believes that the wind speeds will still decline by about 10% before 2100. Both Chinese and South Korean researchers have identified the impact of tall buildings on slowing down the wind. This may be significant, but it often does not feel like it when you walk between skyscrapers.

Either way, the wind can be a bit of a bastard for power grid operators. Back in September 2021, while the British were merrily putting more turbines in the North Sea, the output of their increasing number of wind farms collapsed by 30% compared with the previous year, due to a lack of wind. The result was a major upsurge in gas prices as the grid made up the difference. What matters for generating electricity from wind is consistency. Indeed, high speeds in wind are a positive hazard to the whole idea.

This is not as simple as it sounds. Most wind turbines start to turn in winds running at 6-8 mph. If it goes much above 55 mph, they start to be threatened by the force and have to be feathered. And contrary to perception, they do not simply increase their power output as the wind gets faster and faster. They reach their rated output commonly at 30-35 mph and stay with it, even as the wind gets faster. Yet if it goes slower than this, the output declines. This explains why you don’t see them whizzing round in higher winds, but seem to keep to a slow and stately pace.

Standing near a wind turbine, one might be fooled into thinking these are simple machines. After all, mankind has been grinding corn with windmills for over a thousand years. In fact, they are a triumph of mechanical and electrical engineering. For a start, the yaw drive has to keep them facing into the wind, while the nacelle on top, balancing the back of the turbine, contains a variety of pieces of machinery, including electric motors and brakes and is effectively a gearbox.

The vast majority of wind turbines have three blades, which significantly reduces the angular momentum on the pivot, since one blade is normally upward. Two or four blades would shake the structure much more. There are also some basic trade-offs in terms of height and size of the rotors. By and large, the taller the structure and the longer the blades, the greater the power generated. This is because the wind tends to be steadier higher up, while the longer the blades, the more wind they catch; double the length of the blade and you quadruple the wind capacity.

The downsides of this are the weight of the whole structure and the amount of space it needs. In regard to the space needed, the rule of thumb appears to be that there should be distance between turbines of at least three times the diameter of blades at the sides and ten times it in front or behind. Some US wind farms can take up to 20-30 square miles of area for around 100 MW of capacity. This is fine for the US, but a bit tricky for onshore Europe. The Danish company LM Wind currently holds the record for the length of blade at 107 metres long, but being pragmatic about it, this is not for the onshore business and is pretty tricky to manoeuvre into place. A turbine using these has a diameter almost double the London Eye.

Weight clearly matters too. A pretty standard Siemens Gamesa G87 onshore model, rated at 2 MW, has a rotor weighing 37 tonnes but its nacelle adds 170 tonnes, while the tower itself comes in at around 242, making 449 tonnes in all. Intriguingly Gamesa gives some figures for its operation: it starts to function with wind at 8.9 mph, gets to its rated speed at 29 mph and shuts down at 55 mph; bravely they give a “survival” wind speed of 131 mph, which is presumably the point where it takes off, or falls over. Either way, wind turbines have to have pretty firm foundations, sometimes as much as 30 metres below ground level.

This is obviously a factor in offshore wind capacity, where decades of experience from that sworn enemy of all things environmental, the oil industry, may just come in handy. Mind you, one advantage the offshore wind business has over offshore oil is that their platforms do not sink as a result of the extraction of energy underneath them. Not a lot of people know this about those massive offshore platforms in the North Sea, but as the oil and gas is extracted, they very slowly decline into the briny. Wind has a different problem in that the pressure is sideways not downward.

Up until now, the deepest fixed wind farms are off Angus in Scotland, with 114 turbines being built in 59 metres of water, which will eventually have 1,075 MW of capacity. This, needless to say, is in much shallower water than many oil platforms, the deepest of these being Chevron’s Petronius platform in the Gulf of Mexico in some 535 metres of water. Thus, by and large, the achievable depth for wind turbines is a function of economics, not engineering and the consensus appears to be that wind capacity needs to float, in water depths higher than 60 metres.

At present the cost of floating capacity appears to be roughly three times that of fixed capacity, but this has not stopped them being built. In 2009, Statoil’s Hywind built a 2.3 MW wind turbine 10 km of Karmoy for around $63 million, which has survived 17 metre waves and has operated at 41% of capacity ever since. More are being built, notably off Scotland. Here Hywind’s costs are put at around $10 million per MW, while operating costs are expected to be higher than for fixed platforms. Nonetheless, the floating option is an important factor in the future of wind energy, because it is likely to more than double global capacity. France, Japan and the west coast of the USA have deep inshore waters.

Furthermore, aside from the shortage of available land for wind farms in countries that use the most power, the wind at sea tends to be more consistent and more powerful than on land. In addition, while wind turbines are now a great deal quieter than they were twenty years ago at around 35dB at 350 metres distance, there is still some concern over the health impacts of low frequency noise. Height is also a major consideration, with local councils in Scotland objecting to turbines higher than 200 metres in Galloway.

Another factor relating to both on and offshore wind farms is their potential effects on birds and NatureScot, the Scottish government’s nature agency, has done some considerable research. The mathematics are, to say the least, complicated. However, making the assumption that the bird hasn’t a clue that the turbine is actually there, the chances of one being hit as it went straight through it are put at around 26%. This makes the assumption that the birds are not forewarned by the movement of air around it and are essentially completely clueless.

This, in the opinion of many bird lovers, is something of an insult to their intelligence. Indeed, a very detailed study of the habits of Skuas and Red-throated Divers around wind farms across Scotland, Norway, Sweden, Finland, Germany and North America found only one corpse in northern Germany. Being of a conservative frame of mind, NatureScot put the potential threat at maybe one to three birds a year. More significantly, the study found a great deal of evidence that birds changed their breeding locations, presumably fed up with the constant deep thumping sound. Certainly, earlier visions of hundreds of migrating birds being chopped from the sky seems simply wrong. Whether this would be the case with the arrival of thousands upon thousands of large wind farms globally is another matter.

Speaking of which, between 2000 and 2007, NASA’s Jet Propulsion Laboratory used its satellite “Quick Scatterometer” or QuickSCAT for short, to bounce microwave pulses back and forth right across the planet to measure wind speeds everywhere. Perhaps to nobody’s great surprise, wind speeds are highest across the mid-latitudes of the northern hemisphere during December, January and March and strongest in the southern hemisphere in June, July and August, which when you come to think about it is mighty kind of Mother Nature; winter being when we all need more heating in those areas. Or on the other hand, you may think that the wind chill is one of the reasons why it gets so cold in the first place and would prefer to do without it.

Some places have odder winds than others, notably with the trade winds and monsoons, while the Gulf Stream creates extra wind variations due to the differences in water temperature. What is important here is that mankind now has the capacity to measure wind speeds globally in very great detail, without any longer having to read the numerous ship’s logs of people like Magellan, Drake or Captain Cook. The NASA study concluded that wind could provide as much as 10-15% of all global energy; not simply electricity, but primary energy in total.

Given the resource, this seems a little low, being roughly half to one-third of the primary energy that currently comes from coal. But it is growing at a pretty good lick. According to the IEA, wind farm capacity grew by 113 GW in 2021 or almost double the amount added in 2019. Generation grew by 17% to 273 TWh and this seems likely to continue. However, the IEA’s target is to produce 8,000 TWh by 2030. This means adding a further 250 GW of capacity every year until then. This means doubling the number that were built in one record year and keeping that high.

One danger here is the percentage trap. When starting from a very low base, you can get truly spectacular percentage increases and everybody crows about them. This mathematical morale booster particularly affects renewable energy at present suggesting that more progress is being made than is really happening. To get to even the IEA’s rather low target needs just a little less than 30 times its current production. At an average of 25% capacity factor – due to the variation in the wind – a 2 MW turbine running for 24 hours a day for 365 days a year will produce 4,380 MWh. Consequently, to get to the IEA’s target requires just under two million of these machines.

Admittedly this is a rather simplistic calculation. Clearly some machines will have a much higher wind capacity figure, depending on where they are. In addition, the machines are getting bigger all the time, particularly offshore. That said, however, few turbines can be expected to run for 24 hours every day of the year.

For these are more complex machines than they look and there are several issues that can stop them. Blade failure is the most common and can occur when they are struck by lightning. Equally the complex innards of the nacelle contains not merely electrical mechanisms but lubricating oil as well. Consequently, fire is a constant danger, with occasionally tragic results. Back in 2013 two service personnel were trapped high up by a fire on a turbine in the Netherlands and could not be rescued. Elsewhere, in California a turbine fire set 367 acres of the surrounding land ablaze in 2012. For obvious reasons such fires are difficult to spot, while fire services may have problems with access. The rule of thumb figure is put at around 25 machines catching fire every year, although most are not reported.

That said, the industry is very aware of the problems and most of these fires seem to have happened to machines built more than a decade ago. One problem is also the lack of maintenance personnel. One survey in the US suggested that with over 60,000 turbines in operation, there were only 7,000 qualified personnel. This is not perhaps surprising. A job that requires scrambling up 100 metres of a vertical ladder before you get to your place of work is not for the unfit or faint-hearted.

Nonetheless wind power remains both the fastest growing and the biggest source of renewable electricity apart from hydro. With China in the lead, followed by the USA in terms of total capacity and Denmark and Sweden getting more power per person, wind has a huge role to play in decarbonising the globe. Furthermore, wind can be built up incrementally in places where demand is yet relatively low and the wind blows free. A thousand islands come to mind.