Whenever I cover wind turbines many of you ask about what’s available for home applications. At the moment, I’ve got both good news and bad news. The bad news is that the current market for residential wind is…less than great. The good news? We have a lot of new innovations that look to improve it. The team behind the U.S.-based startup Harmony Turbines is hoping to popularize wind energy for the masses and allow them to have their iPhone moment. Plus, if you remember our video on Aeromine’s rooftop models from last year, we have an update on how its “motionless” design is progressing out in the real world. But of course, these are far and away from the only companies working on bringing wind power generation to our backyards.
Residential wind has to have its moment someday, but when? Or should I say, “but wind?”
I have solar on my home, but it’s obviously only producing significant amounts of electricity on sunnier days. Being able to augment that with wind power is incredibly appealing. That’s one of the reasons why companies like Aeromine and Harmony Turbines have been catching my eye, but I’ll get to them in a minute. Chances are that if you’re interested in renewable energy, you already know that residential wind is nowhere near the commonality and accessibility of residential solar…for now. Why? Well, I’ve previously discussed the practicality (or maybe more accurately, the lack of it) of home wind generation in depth. But for those who aren’t up to speed, here’s a recap.
What’s the challenge?
First of all, just like with any kind of home renewable energy generation, wind requires installation space. However, what makes it different from solar is the amount of space needed. While solar allows for somebody to make use of the roof they already have, wind is generally much more demanding. This isn’t only a function of the height needed to make the best use of winds found far off the ground, but the distance needed to keep turbines away from obstacles that cause turbulence. Otherwise, you risk not only undercutting energy production, but reducing the lifespan of the turbine.1
So, with those factors in mind, the U.S. Office of Energy Efficiency & Renewable Energy recommends you should have at least 1 acre of land for the proper placement of a wind turbine.2 For an idea of just how much that is, keep in mind that the average square footage of a US single family home is 2,273 square feet or 211 square meters on less than a tenth of an acre of land (or 43,560 square feet or 4,046 square meters).3 However, it’s worth noting that about 19% of the U.S. population lives in rural areas, and this typically goes hand-in-hand with having enough room to support home wind systems.2 Sorry, city slickers.
That’s not to say that urban areas are completely out of luck forever, though. There are other companies, like O-Wind and Alpha 311, that are focusing on integrating wind turbines directly into existing city infrastructure. I can dive into these companies in future videos if you’re interested.
That brings us right to the next barrier to wind energy. It might seem obvious at first, but to take advantage of wind power on your home turf, you need…wind. If your local weather doesn’t promote strong and consistent gusts that keep those blades turning, then wind simply isn’t worth your time. And not all wind is the kind that you want. So what separates “good” wind from bad? What are acceptable wind speed ranges, and where can you find them? It depends heavily on where you live.
In a 2022 study on distributed wind setups conducted by the U.S. government’s National Renewable Energy Laboratory, its authors identify California, Minnesota, and the Northeast region as areas of interest. These places tick all three of the boxes that allow for profitability: enough wind supply, high retail electricity prices, and favorable political policies. On a state-by-state basis, New York, Minnesota, Kentucky, Texas, Oklahoma, and South Dakota stand out for holding the “largest economic potential” for residential zones. The researchers also spotlight my own personal stomping grounds, the region of New England, as a solid contender because of its particularly pricey electricity.4 It’s very expensive here.
When it comes to capturing wind energy in residential, suburban or urban settings, you’re talking about wind speeds at roughly 10 meters (~30 feet) above surface level in most cases. And if you look at this map from NREL5 on those average wind speeds, you’ll notice one major trend: most places have a speed of 3 to 5 meters per second (or roughly 6 to 12 mph). That’s not nearly fast enough for wind energy to be cost effective … yet. However, a bunch of companies are trying to address that shortcoming by creating cheaper, more effective turbine designs that can make the most of what little wind resources are available.
That slower, more chaotic wind is usually a big problem … for traditional horizontal wind turbines at least. But not so for Savonius turbines — a type of vertical axis wind turbine that historically hasn’t fared too well as a mass market option. However, this is where creative engineering can truly shine. I spoke to Chris and Cheryl Moore from Harmony Turbines, a small startup developing a really interesting Savonius turbine, about that exact point.
“Generally, wind in the rural and even urban areas is not very good, so it’s dirty wind. It’s disrupted wind, and Savonius turbines are the king of low wind speed power production. Now, it’s not magic. This isn’t like zero point energy or, you know, getting more out of a system than you’re putting in. It’s not magic. It does need wind to make power. But if the majority of the United States, and the world at large, doesn’t have good wind, shouldn’t we try and make a wind turbine that can at least capitalize on that poor wind condition.” — Chris Moore, CEO Harmony Turbines
Clever Approaches to VAWTs for residential
That brings me straight into possible solutions for the more residential market. There are multiple companies, like Harmony Turbines, trying to tap into that niche with a cheaper, smarter approach.
As I mentioned before, Harmony Turbines’ design is a type of Savonius wind turbine, which was invented by Sigurd Johannes Savonius in 1922. They typically consist of two or more half-cylindrical blades that are mounted on a vertical shaft in an ‘S’ shape.6 If you’ve seen an anemometer, which measures wind speeds, it works in the same basic way. They’re designed to spin, even at low wind speed and regardless of wind direction. The turbine captures wind energy through a simple mechanism known as “differential drag.” As wind interacts with the concave and convex sides of the blades, the difference in drag force causes the rotor to spin.7 That differential drag allows it to operate effectively in turbulent wind.8
While it’s known for its simplicity and ease of construction, the Savonius turbine typically has a lower efficiency, which is often reported to be around 15% compared to traditional propeller designs at around 50-60%. But that’s disputed by Chris Moore, the CEO of Harmony Turbines.9
“If you really dig into it and look, you’re gonna see the Savonius Turbine is like the lowest crappiest out of all of them, out of like 10 or 12 pictures, and then you’ll see one that suddenly it’s like up in the 30, and you’re like, well wait, what’s that one? It’s the same graph, just the arrows are reversed. Yeah, so, the bad data, because the internet is just a copy and paste society, it was just making it a thousand times worse, and just putting all this bad data out there. Um, in working with the universities, Penn State especially, like, the professor slapped her hands down on the table, she goes, ‘Yes, yes, yes, I’ve been trying to teach this for the past five years in my classes, that the data’s wrong.’ So they were excited to work with us on this project because they wanted to help debunk this bad data.” — Chris Moore, CEO Harmony Turbines
What sets their approach apart from a typical Savonius design is that the scoops can articulate to control the spin.
“So the way we approach that problem is we have our furling mechanism, where our scoops (or fins or whatever you want to call them) at a certain RPM or when the turbine reaches its max RPM, they’ll close in towards each other a little bit. And the purpose of this is twofold: one, it’ll control the spin, so we’re not spinning out of control. But the second thing that it does is it allows us to continue generating power. Even though we have strong winds, even though we’re partially closed, we’re still generating power. The other ones, they stop.” — Cheryl Moore, COO
When wind speeds exceed a turbine’s rated spin speed, they have to shut off to protect themselves … or they’ll literally tear themselves apart. Harmony’s approach allows it to close itself off a little bit to slow the rotation, but not stop. The idea is to allow the device to keep going even under the kind of wild conditions that would typically grind production to a halt. The ability to reduce the exposure area and slow the rotational speed gives them some advantages over their larger HAWT cousins.
Then there’s Aeromine, which I covered in a previous video. I’ll link to it in the description if you want a deeper dive, but in a nutshell, they’re using airfoils to concentrate and amplify the wind.
The purpose of an airfoil is to make physics work for you and to take advantage of the Bernoulli Effect. This refers to how gasses and liquids flow around an object at different speeds. Just like an airplane wing, air moves faster over the top section of the wing than the bottom, creating lift.
Looking at their turbine from the exterior, there’s no exposed moving parts. Instead, two vertically mounted, hollow foils stand opposite each other with a space between them. This creates a low-pressure zone and as wind flows through the space a short pipe then leads the captured wind to a fully enclosed turbine located at ground level.
The fact that Aeromine’s approach is to place their devices along the front edge of a building’s flat roof isn’t by accident. Have you ever walked between tall buildings and felt like you’re walking into a wind tunnel? I used to work in the center of Boston, and it sometimes felt like I was one of those meteorologists trying to stand upright in hurricane force winds while talking about the ongoing storm. That wind tunnel effect is caused by the wind slamming into the surface of the building and getting compressed and funneled around it. It amplifies the speed of the wind, and Aeromine is capitalizing on that effect.
“One of the things that’s novel about Aeromine is we’re leveraging two fluid streams. What happens is the free wind hits the face of a building. It creates an amplification that goes into our generator, and at the same time, as the free wind hits the airfoils that creates a pressure, which pulls the wind up. So instead of kind of fighting the environment that it’s on, it’s actually helping it’s using the building structure itself to help. We’re leveraging the inherent aerodynamics of a building and those flow streams to effectively amplify the wind resources.” — David Asarnow, CEO
Basically, Aeromine is taking what would normally be a negative to a traditional horizontal wind turbine and making it an advantage. They’ve also been busy since I talked about them last time and have some interesting updates, which I’ll get to in just a minute.
The potential market for homes/urban/suburban wind
If one or more of these companies is successful at driving down the cost per watt of small wind turbines for more residential and suburban settings, there’s a huge market they can tap into.
“The traditional thinking in the wind industry, which is totally valid, is bigger is better because the bigger the swept area, the more power you can put out … which makes all the sense in the world. You know, that’s a lot of physics, but at the same time it does create a limited market to some level as far as applications … We think there’s a lot of behind the meter opportunity by leveraging these large rooftops to create power. You’re not as beholden to, you know, transmission requirements and you can get the power to where it’s needed.” — David Asarnow, CEO
“But it’s virtually an untapped market right now, so it’s not like … 90 percent of residential areas already have wind turbines, and so then you’re trying to convince them to get rid of that and get a new one. People are looking for them … People are waiting for the right solution to come out, and so we hope that we are the ones that fill that gap. People are looking for it, they’re not necessarily moving on the bad solutions, or the inferior solutions, I shouldn’t say that, the inferior solutions. You know, they’re just kind of waiting because they don’t know what to do.” — Cheryl Moore, COO
David said something very similar.
“If you think about onsite generation, what are folks really trying to achieve? They’re trying to maximize their on site generation. And so, I think that’s what really resonates with folks that we talk to every day all around the world, is that this technology allows Uh, an operator or owner of a building, um, were suitable to create this incremental generation, uh, which can really move the needle and be quite meaningful.” — David Asarnow, CEO
If a homeowner or building owner crunches the numbers and sees a path to maximizing their energy generation and savings by layering in wind turbines along with solar, small scale, distributed wind generation could finally see its…day in the sun.
When will they get here
This is where it gets interesting. Since I last covered Aeromine, there’s been some updates on what they’re doing. The company has had a pilot project running on top of a BASF building for about a year and a half with great results, and it’s planning to expand in 2024.
“We have a series of approximately 10 pilot projects that are actually in production right now and are starting to roll out in the next two quarters. So you’ll see a lot more Aeromines on the rooftops, both the US and Europe, in the next six months. And then we are in the final stages of what we call “design for manufacturing” of our mass market product, which should be introduced late in 2024.” — David Asarnow, CEO
Meanwhile, Harmony Turbines is collaborating with two universities in the company’s home state of Pennsylvania: It just finished a study that involved receiving feedback from Bucknell University, and it also has additional work being done with Penn State University. Harmony is also making a splash across the pond at Northumbria University in the UK.
Bucknell’s study helped the Harmony team do full scale testing of its current design, and Penn State has been doing water tank testing for clustering effects. That’s basically determining how to group turbines together to maximize production. In horizontal axis wind turbines, that usually means having to space them far apart, as the wake created by the turbines upwind can dramatically impact those behind it. What’s interesting is that for vertical axis wind turbines, that’s not the case. In fact, studies are showing that grouping them closer together can actually amplify their production.10 Again, this is about turning the disadvantage of dirty, chaotic wind into a positive.
Chris and Cheryl spoke to me at length about how they’re continuing iteration on their scoop design and will be starting to gather a lot of data next year. Like I said, they’ve got a really interesting approach that I’m keen to see play out, but they’re very early days. One thing I LOVE about Harmony Turbines as a company is how they’re sharing their journey of development out in the open. Most companies don’t do this. They have a website and a YouTube channel with videos they’re publishing on a regular basis. So, if you’d like to see what it’s like to develop this technology, and why it takes more time than you think it should, be sure to follow them. It’s awesome stuff. And let me know if you’d like me to do a deeper dive on their approach (or any other companies in this area).
While smaller scale wind technology still isn’t here for homes just yet, there’s a lot of interesting developments in the works. It doesn’t seem like we’ll have to wait much longer to find out which way the wind is blowing.
- Small Wind Guidebook: How Do I Choose the Best Site for My Wind Turbine? ↩︎
- Small Wind Guidebook: Intro ↩︎
- Average size of floor area in new single-family houses built for sale in the United States from 1975 to 2022 ↩︎
- NREL 2022: Distributed Wind Energy Futures Study ↩︎
- NREL: Annual Average Wind Speed at 10 Meters Above Surface Level ↩︎
- Savonius Wind Turbine ↩︎
- Savonius Rotor ↩︎
- REUK.co.uk – Savonius Wind Turbines ↩︎
- FAQ: Everyone says that Savonius turbines have terrible efficiency compared to other designs. Why are you wasting time and money on this? ↩︎
- Numerical modelling and optimization of Vertical Axis Wind Turbine pairs: a scale up approach ↩︎