Is Wind Energy Effective?

The conventional ways of generating electricity are out dated, unsustainable, and in fact damaging to many of the delicate ecosystems at work on our planet.

Society’s response to this is to put forward renewable energies like solar and wind energy to offset the problem. So just how effective a solution is wind energy? And how does it compare to its cousin, solar energy, or its older competitors, gas and coal?

Is wind energy effective? Wind energy is one of the most effective methods of harnessing renewable energy today, behind hydroelectric and tidal power plants, and just about equal with carbon emitting gas and coal-fired power plants.

Advances in technology have made wind energy more and more efficient over the years, bringing the cost down from 40 cents per kWh in the 1980s to 2.5 – 5 cents per kWh today.

Most wind turbines in use today harness 30-45% of the wind energy that passes by their blades. In other words, if 100 Kw of kinetic energy blew past the turbine as wind, the generator would on average be able to create 30-45 Kw of electricity.

How Does Wind Energy Compare to Other Forms of Energy?

Wind energy is far from alone in the energy market. It shares the stage with a host of other technologies. By looking closer at the efficiencies of each of the major players, we can paint a clearer picture of how good we humans are at harnessing energy.

Hydroelectric – Ranking at the top of almost any comparison, is Hydroelectric energy plants. Usually situated in a dam of some sort, these plants divert the still water into channels of flowing water, and use those channels to spin generators which gather between 90% – 95% of the water’s kinetic energy from the flowing water.

Solar Energy – At the moment, solar panels gather from 15- 20% of the sun’s energy, but recent advances in the technology have pushed that number up to around 40%, and further advances will make those types of solar cells more available in the near future. So look out wind, solar is on the rise, if you’ll pardon the pun.

Tidal – Tidal energy is one of the most efficient forms of renewable energy, raking in about 80% of the tide’s available kinetic energy. It harnesses the energy brought in by the tides twice a day.

Nuclear – When atoms are separated at a fundamental level it creates a lot of energy. When done violently that energy looks like an atomic bomb; when done with more accuracy and finesse, and with different materials, it looks a lot more like a nuclear power plant.

Nuclear power plants use the heat released by the isotopes to boil water, and the resulting steam is used to turn turbines to generate energy. They are able to capture between 30-37% of the radiant heat energy created by those nuclear reactions.

Gas/Coal – There’s no getting away from carbon emissions with this type of energy production: Coal- and gas-fired power plants harness 33-40% of the available energy from the coal and gas that they burn. Meaning that 60-67% of the coal or gas that is being burned, isn’t generating electricity.

Is Wind Energy Cost-Effective?

The cost of wind energy depends a lot on how much power you need or want. Systems outputting less than 100 kilowatts, (small scale turbines) cost roughly $3,000 – $8,000 per kilowatt capacity. So a 10 kW turbine would run you $50,000 – $80,000, after installation.

Naturally, the more power you want to gather, the more expensive it’s going to be. For instance, most commercial wind turbines have a capacity of 2 Megawatts (MW), that’s 2000 Kilowatts (kW), and cost $3 – $4 million dollars each.

Getting your money back can be a hurdle sometimes when purchasing a wind turbine. You must calculate not only the amount of energy the turbine is able to capture, (10 kW – 2 MW commercial, etc.) but also the available energy in your area.

You can do this either by measuring it for yourself for up to a year to get a proper average, or by trusting the collected data online or in an almanac which contains such numbers.

One also must know the given life expectancy of the turbine they’re purchasing, (usually a commercial wind turbine will last upwards of 20 years) the installation and annual maintenance costs, and the current price of energy, which varies from area to area, and which at the time of writing is averaged to 12 cents per Kilowatt hour in the United States.

With all that information, you can calculate how long it will take for your new wind turbine to pay for itself. As a rule of thumb, anything longer than ten years means it’s probably not worth the investment, but don’t let me tell you how to live your life.

Where is Wind Energy Most Effective?

Wind energy is more useful in some places than in others, for instance there would be little point erecting a wind turbine in the middle of a city, or in your basement. Anything that would block or disrupt the wind before it gets to the turbine itself, means a loss of energy.

So it’s important to place wind turbines where the wind will be largely undisturbed. This is why you often see wind farms laid out over the vast open landscapes in the Midwest, or situated in the water off the coast.

Offshore Wind Farms

One of the most ideal places to have wind turbines is offshore or in the open water, as there are no obstacles for the wind to maneuver around, making the wind much stronger.

Offshore wind farms tend to be more expensive to set up, but yield a higher return as the winds blow stronger and for longer periods compared with onshore wind farms.

They also aren’t limited in terms of size. Whereas onshore wind farms are limited by the roads available to deliver materials, offshore, you simply need to float your materials out to the building site.

Another reason to put wind farms out on the water is that wind turbines are more noisy than most people realize. Every time a big fan blade whips by it makes a loud whoosh.

That coupled with a whirring generator up at the top, and it’s no wonder that some neighborhoods would much prefer the turbines to be built somewhere else.

How Does Wind Energy Compare to Solar Energy?

These two giants of the renewable energy industry will likely be the resources that help humanity break its dependence on fossil fuels, but neither are perfect. For starters let’s look at what they share:

They both rely on resources that are not always available: the sun is hidden literally half the time, unless you’re a resident of northern Canada or the Arctic Circle; and the wind sometimes just doesn’t blow.

These obstacles are to be expected and are solved by placing them where they’ll be most effective. I.e. placing solar panels in places with minimal cloud cover, and placing wind turbines where the wind blows most often.

Danger to Wildlife

It’s an unfortunate fact that while these renewable sources of energy are meant to lessen our impact on the environment, and they certainly do, they’re not without their drawbacks.

Wind turbines for example kill an estimated 140,000 to 328,000 birds per year in North America, according to the Audubon Society. While solar kills much fewer birds, the number still isn’t zero.

Solar farms have been known to ignite birds mid-flight in its 900 degree beams. One solar farm in California is reported to have killed upwards of 6000 birds per year.

These are substantial problems, and people have already made improvements on these numbers. However, and this is not to diminish the value of the birds’ lives, these numbers are dwarfed by the amount of birds that die from collisions with buildings, which is estimated between 365 – 998 million birds annually.

Efficiency

Though, as I mentioned earlier, solar power is likely to see impressive technological advances in the near future, what with the recent advance to solar cells that can capture up to 40% of the sun’s energy.

At the moment wind energy massively outweighs its solar counterpart. One wind turbine can generate the same amount of power per kWh as 48,704 solar panels.

One consideration that solar has in its favor is space. Commercial wind turbines are massive, some standing taller than 400 ft, part of that being the blades which can reach a diameter of 280 ft. They need space, and that’s why they’re usually placed in rural areas, away from densely populated areas.

Solar on the other hand is more versatile. They can be inoffensively strapped to the roof of your home, out of the way, or set up in an array in an empty field of unused land.

Ultimately, neither of these technologies are perfect, and what we should strive for is a union between these two renewable sources of energy, not a division between them.

They’re both use resources which are practically limitless, they both release less harmful greenhouse gasses into the atmosphere, they each can fill the gaps the other one leaves behind.

Wind power can provide for rural areas and anywhere there’s room for their hulking blades. Solar can fill in the rest of the gaps with solar farms in open areas like the one in the Mojave desert, and it can be utilized in more densely populated areas, where wind turbines are an eyesore.

Vertical-Axis Wind Turbines (VAWT)

Vertical wind turbines are a fairly recent development and they solve some of the problems presented by the typical horizontally spinning wind turbine.

They can be used in densely populated areas, as they are silent and are not that bad to look at either. Their vertical spin looks a lot like a climbing double helix or a barber shop’s pole, so they might even be used as an attraction or an art installation.
They’re less dangerous to birds.
They are able to harness the wind omnidirectionally, meaning that no matter what way the wind is blowing, a VAWT can use it.
A single-axis means the generator and gearbox can sit at ground level, which makes maintenance faster and easier.
VAWTs have their downsides, of course, for instance, if wind can come from any direction, gusts of turbulent wind could stall the turbine. Having a single axis but multiple directions of force mean that undue strain is put on the axis.
But modern designs make improvements on pre-existing VAWTs, making them more durable and more viable.
Studies have shown that a carefully constructed wind farm consisting of Verticle-axis wind turbines, could produce ten times the energy of a conventional wind farm of the same size.

What’s the Limit of How Effective Wind Energy Can Be?

It’s impossible to harness 100% of the wind’s energy, and if you’ve ever watched an incense stick burn, or watched a camp fire throw smoke into the sky, you can understand the basics of how wind energy works, and what its limitations are.

Picture a burning incense stick, with the smoke particles rising up in the hot air. When it’s a nice smooth column of smoke, that’s known as laminar flow, and when it’s twisting and turning and going crazy, that’s known as turbulent flow.

If you put a very tiny wind turbine into this laminar flow, the rising air would turn the blades, and you’d be harnessing a certain percentage of the air’s energy. This makes the smoke on the other side of our mini turbine rise a little bit slower, since we’ve taken some of its energy.

Now imagine that we were hypothetically able to harness 100% of our incense’s energy. The smoke particles wouldn’t be able to rise past our turbine, they’d simply hover there until pushed out of the way by something else. This of course can’t happen in nature according to the laws of physics, but what’s the upper limit of how much energy can we harness from the wind?

A German physicist named Albert Betz in the early 1900s calculated the upper limit of a turbine’s ability to capture energy from the wind to be 16/27s, or 59.3%. This is known as Betz’s limit, or Betz’s Law.

Modern day wind turbines are able to capture 70-80% of the Betz limit. Though there are a few who claim to have surpassed Betz’s limit, these newcomers should be taken with a grain of salt, as none have yet proven their ability to gather more than 59.3% of the wind’s energy, and especially under adverse conditions.

How Did Wind Energy Get So Effective? A Brief History

wind turbines closeup with lushan mountain background, China

Wind energy is harnessed using a turbine, essentially a large fan, but instead of pushing the air like a normal desk fan would, wind turbines are pushed by the wind. As those giant fan blades spin they turn a generator, which generates electricity, which is funneled down into the grid and may be powering the device you’re reading this on right now.

One issue that engineers ran into while designing these wind turbines is the fact that the blades, being so large, turn so slowly, on average only 10-20 revolutions per minute. If the engineers settled for that amount of energy generated, wind energy, as an industry, would be just terribly inefficient.

So the engineers’ solution was to connect the fan blades, or rotor, up to a set of gears with the intention of increasing the generators spin speed. It works, with the gear box in place, the generator can spin on average 90x faster and thus generates 90x more electricity. Thanks engineers!

“But what if the wind spins it too fast?” I hear you cry, “How do they slow the blades down?” They have installed between the gear box and the generator, a braking system, much like the one in you car, which can slow down the blades. However this creates a lot of heat, and can lead to, very rarely…explosions.

So the engineers came up with an alternative solution. They designed a mechanism that can rotate the fan blades to an angle that doesn’t catch as much wind, just like a pilot might do to the flaps of the plane when they reach cruising altitude, or after they’ve landed.

With all the pieces in place, and a motorized mechanism which can turn the head of the turbine to face the wind, you have a machine that can turn wind into electricity.

Learn More

If you’re serious about learning more about wind energy, I recommend the Wind Energy Handbook on Amazon. This book is great for both students and professionals, and it holds invaluable information on the subject of wind power.