Wind Turbines for Home: Is it Worth It?

Rooftop solar energy is one of the great success stories of the energy transition. My

home

country, Australia, is leading the way in this regard: one in four

home

s now has solar panels on the roof. When all of Australia's rooftop solar is added up, it is a larger contributor to the grid than any generator or power station. This has happened in part thanks to initial government support and in part because of successful efforts to reduce permitting time and installation costs. And of course it helps that Australia is just a very sunny place. Take a look at the last year of the power grid across Eastern Australia's power grid.

There is plenty of solar energy every week, even in the middle of winter. So in Australia we have it pretty easy, but what about in northern Europe, like Germany or Denmark, where I used to live? Having lived there for five years, I can tell you that there were many more opportunities for

wind

surfing there than there were for sunbathing. . It is generally a dark and

wind

y place compared to Australia. But if you travel through northern Germany and Denmark, although the roads are lined with large-scale wind farms, if you look at the houses, you will see that they have solar panels, not wind

turbines

.

So why has urban wind energy taken off like urban solar energy has? In this video, we're going to talk about some of the reasons why rooftop wind

turbines

or urban wind in general are a much tougher challenge than rooftop solar, even in dark and windy locations. like Denmark. And yes, I will also talk about circumstances in which small-scale wind does make sense. And include some urban wind technologies you can use if you decide small-scale wind is for you. And I know from the comments that there are many of you. First, I want to start with the quality of renewable energy resources available on rooftops.

The quality of a solar resource, or how much sun there is, is measured in solar irradiance, which on this map is the annual average in kilowatt hours per square meter. To get a good resource, you just need to find a sunny place and then tilt the solar panel so that it points directly at the sun. If you want to place a solar panel on your roof, you will need to avoid shade from nearby trees, buildings or hills and choose a face of your roof that is close to the optimal tilt angle. And if you can pull it off, you'll end up with a solar resource pretty close to what a nearby solar farm would achieve.

And if you're in a place with a poor solar resource, say Kolding, Denmark, where I used to live, which has about 930 kilowatt hours per square meter, that's a little less than half the energy available in a good place. , let's say Canberra, where I live now, which has 2100 kilowatt hours per square meter. Therefore, you will get a little less than half the energy from a solar panel in Kolding than you would from the same solar panel in Canberra. Now let's look at the wind. The quality of a wind resource is usually evaluated by looking at the average annual wind speed.

Near Kolding, Denmark, the average annual wind speed is about nine and a half meters per second at 150 meters above the ground, and 4.3 meters per second at 10 meters above the ground. So in this last sentence, there were two clues as to why we don't see much urban wind. The first clue was when I said the wind speed "near Kolding" and not the wind speed "in Kolding". And that's because winds in urban areas are slower than in surrounding areas. Tall buildings block the wind, slowing it down and making it more turbulent. Therefore, wind speeds in urban areas are usually 30 to 40% lower than in nearby rural areas.

The second clue was the fact that the wind speed was significantly higher at 150 meters above the ground compared to 10 meters above the ground. And this is due to wind shear. As I mentioned before, wind near the ground is slowed down by buildings and also by trees and hills and stuff. As you move forward and away from these obstacles. There is nothing to stop the wind from making it faster. That's one of the main reasons why turbines and wind farms are increasingly getting taller towers. A wind farm wind turbine can have a tower height of 150 meters and reach those 9.5 meters per second winds, while an urban wind turbine, say on top of a roof or in a backyard, would be closer to 10 meters. high, which is equivalent to 5.2 meters per second. second in open terrain, and probably something like 4.3 meters per second in a built-up area.

Therefore, the short urban wind turbine will get wind speeds that are only about 46% of those of the tall wind farm wind turbine, even when they are very close to each other. And it gets worse because the energy of 4.3 meters per second of wind is not even 46% of the energy of 9.5 meters per second of wind. In fact, it is less than 10%. This is because the power available in the wind is related to the cube of the wind speed. There are 525 watts in a swept area of ​​one meter with a wind of 9.5 meters per second compared to 50 watts in an area of ​​one meter per square with a wind of 4.3 meters per second.

So even with a wind turbine of the exact same size, you will get 10 times less energy from the urban wind turbine compared to the commercial scale one. Let's complete our comparison by returning to Canberra, where the wind speed data gives us 5.6 meters per second at 150 meters and 3.5 meters per second at 10 meters. If we placed a wind turbine sweeping an area of ​​one square meter on top of a Canberra roof, it would say that the average wind speed is 3.5 meters per second and it generates 25.6 watts of power at that wind speed, the Kolding site has an average wind speed of 4.3 meters per second, and the same turbine on a Kolding rooftop will generate 50 watts of power at that wind speed.

And if those towers could be placed slightly outside the city on 150 meter towers, a one square meter turbine would reach 5.6 meters per second in Canberra and 9.5 meters per second in Kolding and would generate 110 watts in Canberra and 525 watts in Kolding. So those two factors, the reduction in wind speed near the ground and in urban areas, those two factors combined with the fact that wind power varies with a cube of wind speed make up most of the reason which is why urban winds do not produce as much. sense as urban land. But there are a few other reasons that I'll quickly address.

Now let's focus on the wind and solar resource maps and take a closer look at the Canberra region, solar irradiance varies from approximately 1800 kilowatt hours per square meter to 2100 kilowatt hours per square meter. It's basically the same whether I'm on my roof or at the largest solar park near the city, the Royalla Solar Park, while the average wind speed varies from about 2 meters per second to 10 meters per second. That's around two meters per second in the quietest area and around 3.5 meters per second in the parts where most Canberrans live, to more than nine meters per second at 150 meters in the busiest areas. wind speed, which is basically right where I am now.

Surprise, surprise, they installed a wind farm there. And I will say that when I left town, I would have said it was basically a windless day, but it's pretty windy here. Because wind speed varies a lot and power depends on the cube of wind speed, there is a lot more to be gained by choosing really good places to put wind turbines compared to solar panels that can go basically anywhere there is. We have space for them as long as they are not in the shade. The next reason I want to discuss is the nature of a wind turbine versus a solar panel.

Wind turbines rotate, which causes the moving parts to produce a certain amount of noise and vibrations, and the wind forces that rotate the blades necessarily cause a large force that the base of the tower has to withstand. Industrial wind turbines have service technicians who perform maintenance and repairs at least once a year. And they have large concrete foundations to resist the thrust loads that try to topple the turbine. If you want to place a turbine on top of your roof, you will need to ensure that the roof structure can support it and that all noise and vibrations travel to the supporting structure, which can sometimes be a big nuisance.

Solar panels, on the other hand, are fairly lightweight, quiet, do not vibrate, and require virtually no maintenance over their lifetime, other than occasionally needing to be cleaned of dust or snow. Well, there are many reasons why urban wind doesn't make sense. But I promised at the beginning that I would include examples of where it makes sense. So the first and most obviously beneficial situation where you will definitely want to install a small wind turbine are off-grid homes or microgrids that need to generate all of their power themselves. This adds value or diversity of resources to help distribute generation between day and night, summer and winter.

You can get by with much less energy storage or backup diesel generation if you include wind power, even in a place whose wind resource is not so great. The next place you'll probably want to use smaller urban wind is if you're located somewhere that really has high wind speeds. Rural properties, such as those on the Jutland coast, are an example of this. There are small wind turbines everywhere, on small farms and rural properties. And I talked to a couple of farmers who have them and were delighted with the performance and the money it saved them compared to buying them online.

Another place where urban wind might make sense is architectural buildings with wind turbines whose purpose is to inspire or look attractive or any reason other than to generate significant amounts of electricity at a reasonable price. I mean, these buildings are just cool. And I have no doubt that they could have gotten the same amount of renewable energy much cheaper by building a regular large wind turbine somewhere else. But they could also house the same number of hotel rooms or offices at a lower price simply by building many concrete rectangles. There is a place in the world for things that are great and for things that inspire people.

Lastly, if you enjoy DIY or garden engineering as a hobby and want to learn about wind energy, then an urban wind turbine is a great project for you. Personally, I have learned a lot from small wind energy projects that definitely didn't make any economic sense for the amount of energy generated. And I highly recommend these projects to anyone interested in wind energy or engineering in general. So if you fall into one of these categories, I would like to refer you to this book by Hugh Piggott. And if you are buying a small wind turbine, I would recommend purchasing it from the list of certified wind turbines whose performance has been validated.

A big thank you to the Rosie Patreon engineering team who supported this video like everyone else. If you would like to join us, there is a link in the description. You can join us on Patreon and the Discord server to chat about all things renewable energy, we'd love to welcome you. I work a lot with wind energy and less with solar energy. So for this video, I turned to Brilliant, who is the sponsor of this video. And I took their solar course to review the relevant topics. Brilliant is a website and app with over 60 interactive courses in math, science, and related subjects like engineering.

I like Brilliant because it allows you to learn interactively. It's not about memorizing, it's about doing. And that's what STEM is all about in the real world and especially engineering. Some of the topics and the solar course are things I know well from my work as a clean energy expert. Some things were reminders of things I studied in school and others were new. Brilliant has something for all levels of knowledge. If you've never studied STEM, or if it's been a long time, then you can go back to the basics. And even if you're an expert in closely related fields, there's still something to learn.

You can start for free and for Engineering with Rosie viewers, Brilliant's is offering 20% ​​off an annual subscription for the first 200 viewers who sign up. You just need to go to shiny.org/EngineeringwithRosie, I'll put a link in the description. Thank you Brilliant for joining as a new sponsor of the channel and thank you for watching. See you in the next video.