driving home I saw a new wind turbine

jwxr7 · 02-18-09, 07:10 AM

Took a different route home last week and noticed turbine blades spinning in the distance

. It appears to be a Skystream 3.7. Skystream 3.7 Compact Wind Turbine and Wind Energy System

They are usually grid connected using a 2.4kw peak generator and a 12 foot down wind rotor.

I tried getting a couple shots of it yesterday on my way by. The first pic, you have to look close in the center to see it.

Daox · 02-18-09, 07:45 AM

Are you planning on talking with the owner?

jwxr7 · 02-18-09, 08:17 AM

I would like to.
It would be interesting to see his tower up close and how it is footed and guyed. I'd also like to see how his experience with our utility went.

Bob McGovern · 02-18-09, 10:49 AM

Usually they are on 'light-pole' type unguyed towers. SWWP has done an excellent job with distributorships and supporting homeowners in their zoning and utility negotiations. So these things are popping up in unexpected neighborhoods. Price is right where it needs to be, too.

Initial performance reports have been disappointing, tho. SWWP has always put more effort into marketing and sales than into engineering. Output numbers I have seen are about half what you would expect from a grid-tied turbine that diameter. Why the scimitar-shaped blades? No reason I can see. Big commercial turbines have straight blades. You want your leading edge perpendicular to the lift vector; last thing you want is air movement parallel to blade length, detaching laminar flow. I fear it's to make the machine look 'dynamic' and 'new.' Yup -- just found this from their PR: "A visually aesthetic shape played a key role in the design to show that a wind generator is not only a clean source of energy but pleasing to the eye." Bah. Good engineering is pleasing to MY eye. Keep your curved bloody blades.

What kind of Net Metering regs are in your district? That and incentives will make all the difference in feasibility.

ETA: URF! Just pulled up a wind resource map for Michigan. Not so good. Along the lakes it's fabulous, esp. down the western shore. But that seems to end about one mile inland, for some odd reason. Thumb's okay.

knowbodies · 02-18-09, 07:45 PM

Quote:

Originally Posted by Bob McGovern

Initial performance reports have been disappointing, tho. SWWP has always put more effort into marketing and sales than into engineering. Output numbers I have seen are about half what you would expect from a grid-tied turbine that diameter. Why the scimitar-shaped blades? No reason I can see. Big commercial turbines have straight blades. You want your leading edge perpendicular to the lift vector; last thing you want is air movement parallel to blade length, detaching laminar flow. I fear it's to make the machine look 'dynamic' and 'new.' Yup -- just found this from their PR: "A visually aesthetic shape played a key role in the design to show that a wind generator is not only a clean source of energy but pleasing to the eye." Bah. Good engineering is pleasing to MY eye. Keep your curved bloody blades.

I don't think 'a visually aesthetic shape' is the only concern here. A windmill blade performs very much like an airplane's wing - some of the wind hitting the blade will travel laterally down the leading edge to the tip of the blade. As it leaves the tip of the blade it (travelling much faster than the surrounding air) it mixes with the surrounding air creating turbulence and noise. An aerodynamic scimitar shape should slow the air on the leading edge and help reduce noise and turbulence. I couldn't tell you how their design affects the efficiency of the windmill though.

And it looks cool so I'm sure their marketing department loves it.

Bob McGovern · 02-18-09, 09:48 PM

It's an interesting notion. Airplanes sweep their wings back to slide the air stream away from the drag and turbulence of the fuselage. Tip spillage -- which is a major source of turbulence and noise -- is increased with swept-back airfoils since lots of air migrates along the blade length. I would expect the Skystream's blades to loose nearly all lift where the curve begins; it should act like an 8ish-foot turbine because of those raked blades, and that's exactly what its (real-world) output numbers resemble. Really, at 300 RPM noise shouldn't be much of a problem whatever the blade shape.

I saw a prospectus for another residential-sized turbine with curved blades. They claimed it would be very quiet because (to paraphrase) "the curvature relieves pressures that build up on both sides of the blade." Yeah, that dreaded pressure differential. It's called lift. It's what makes the alternator go round.

Quiet blades are great -- but sometimes a turbine is quiet because it just isn't working very hard. That's the case with most VAWTs.

The trouble with SWWP is they too often begin with a marketing plan and a price point, then design backward until something resembling a wind turbine plops out. Then they hype the heck out of it, driving expectations up. It's made for a successful enterprise -- and a lot of unhappy customers. If we could marry their marketing and cost management divisions to ARE's engineering department, life would be grand.

As for placing an expensive, utility-power-grade inverter on top of a tall metal pole.... Don't even get me started on that idea. I got a handful of Bergey rectifiers that have eaten it from lightning strikes and blowing snow. NOT a good place to stick delicate electronics. Put the fancy stuff down on the ground with a couple lightning arrestors and a grounding spike ahead of it.

Bob McGovern · 02-18-09, 10:09 PM

Okay, here's some info on Michigan's net metering and incentives. It's not the worst I've seen, but the deck is firmly stacked in the utilities' favor. First, it's voluntary -- not every utility has to play. Second, since they had to go back and amend the interconnection permissions, you can guess the utilities were setting up major roadblocks. Third, they limit system size to your approximate household consumption, to prevent meaningful cogeneration. Fourth, they work on rolling credits rather than cash payments; any excess credits at year's end get zeroed out.

At least they credit you at retail prices, which is better than many states. In Wyoming, grid-tied RE owners pay retail cost for the electricity they draw off the utility (~$0.080/kWh) but get credited wholesale cost (~$0.025) for the power they add to the grid. It's called "avoided cost": what it would cost the utility to generate that electricity from coal. Takes a long time to pay off an RE system at 2.5 cents per kWh.

Michigan offers no money or tax breaks for residential RE systems. Looks like some individual utilities might. Here's THE clearinghouse for state and federal incentives: DSIRE.

jwxr7 · 02-19-09, 07:10 AM

I just rechecked my utility's web site and they've updated it with stuff from the new alternative energy bill that passed in the fall of 2008.

Consumers Energy Web Site

I can't link the section on generators under 30kw, but it's in the first link if you navigate around a bit.

It looks better than it used to.

jwxr7 · 02-19-09, 07:17 AM

Bob,
BTW, this skystream is using a guyed tower. I'm not interested in buying a skystream, just want to look at the tower and talk to the owner about dealing with Consumer's energy.

I'm glad to see AE growing in my area.

Higgy · 02-19-09, 10:44 AM

You guys know like WAY too much about all this.

After reading all this I feel like I just got geek slapped with a combo punch of aeronotics and physics.

Remind me to have you guys flown out to my place when I'm going to get one of these set up.

02-18-09, 07:10 AM	#1
jwxr7 Apprentice EcoRenovator Join Date: Dec 2008 Location: mid michigan Posts: 191 Thanks: 0 Thanked 0 Times in 0 Posts	driving home I saw a new wind turbine Took a different route home last week and noticed turbine blades spinning in the distance . It appears to be a Skystream 3.7. Skystream 3.7 Compact Wind Turbine and Wind Energy System They are usually grid connected using a 2.4kw peak generator and a 12 foot down wind rotor. I tried getting a couple shots of it yesterday on my way by. The first pic, you have to look close in the center to see it. Attached Thumbnails

02-18-09, 10:49 AM	#4
Bob McGovern Lurking Renovator Join Date: Feb 2009 Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts	Usually they are on 'light-pole' type unguyed towers. SWWP has done an excellent job with distributorships and supporting homeowners in their zoning and utility negotiations. So these things are popping up in unexpected neighborhoods. Price is right where it needs to be, too. Initial performance reports have been disappointing, tho. SWWP has always put more effort into marketing and sales than into engineering. Output numbers I have seen are about half what you would expect from a grid-tied turbine that diameter. Why the scimitar-shaped blades? No reason I can see. Big commercial turbines have straight blades. You want your leading edge perpendicular to the lift vector; last thing you want is air movement parallel to blade length, detaching laminar flow. I fear it's to make the machine look 'dynamic' and 'new.' Yup -- just found this from their PR: "A visually aesthetic shape played a key role in the design to show that a wind generator is not only a clean source of energy but pleasing to the eye." Bah. Good engineering is pleasing to MY eye. Keep your curved bloody blades. What kind of Net Metering regs are in your district? That and incentives will make all the difference in feasibility. ETA: URF! Just pulled up a wind resource map for Michigan. Not so good. Along the lakes it's fabulous, esp. down the western shore. But that seems to end about one mile inland, for some odd reason. Thumb's okay. Last edited by Bob McGovern; 02-18-09 at 04:46 PM..

02-19-09, 07:10 AM	#8
jwxr7 Apprentice EcoRenovator Join Date: Dec 2008 Location: mid michigan Posts: 191 Thanks: 0 Thanked 0 Times in 0 Posts	I just rechecked my utility's web site and they've updated it with stuff from the new alternative energy bill that passed in the fall of 2008. Consumers Energy Web Site I can't link the section on generators under 30kw, but it's in the first link if you navigate around a bit. It looks better than it used to. Last edited by jwxr7; 02-19-09 at 07:25 AM..

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02-18-09, 07:45 AM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Are you planning on talking with the owner?

02-18-09, 08:17 AM	#3
jwxr7 Apprentice EcoRenovator Join Date: Dec 2008 Location: mid michigan Posts: 191 Thanks: 0 Thanked 0 Times in 0 Posts	I would like to. It would be interesting to see his tower up close and how it is footed and guyed. I'd also like to see how his experience with our utility went.

02-18-09, 09:48 PM	#6
Bob McGovern Lurking Renovator Join Date: Feb 2009 Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts	It's an interesting notion. Airplanes sweep their wings back to slide the air stream away from the drag and turbulence of the fuselage. Tip spillage -- which is a major source of turbulence and noise -- is increased with swept-back airfoils since lots of air migrates along the blade length. I would expect the Skystream's blades to loose nearly all lift where the curve begins; it should act like an 8ish-foot turbine because of those raked blades, and that's exactly what its (real-world) output numbers resemble. Really, at 300 RPM noise shouldn't be much of a problem whatever the blade shape. I saw a prospectus for another residential-sized turbine with curved blades. They claimed it would be very quiet because (to paraphrase) "the curvature relieves pressures that build up on both sides of the blade." Yeah, that dreaded pressure differential. It's called lift. It's what makes the alternator go round. Quiet blades are great -- but sometimes a turbine is quiet because it just isn't working very hard. That's the case with most VAWTs. The trouble with SWWP is they too often begin with a marketing plan and a price point, then design backward until something resembling a wind turbine plops out. Then they hype the heck out of it, driving expectations up. It's made for a successful enterprise -- and a lot of unhappy customers. If we could marry their marketing and cost management divisions to ARE's engineering department, life would be grand. As for placing an expensive, utility-power-grade inverter on top of a tall metal pole.... Don't even get me started on that idea. I got a handful of Bergey rectifiers that have eaten it from lightning strikes and blowing snow. NOT a good place to stick delicate electronics. Put the fancy stuff down on the ground with a couple lightning arrestors and a grounding spike ahead of it.

02-18-09, 10:09 PM	#7
Bob McGovern Lurking Renovator Join Date: Feb 2009 Posts: 24 Thanks: 0 Thanked 0 Times in 0 Posts	Okay, here's some info on Michigan's net metering and incentives. It's not the worst I've seen, but the deck is firmly stacked in the utilities' favor. First, it's voluntary -- not every utility has to play. Second, since they had to go back and amend the interconnection permissions, you can guess the utilities were setting up major roadblocks. Third, they limit system size to your approximate household consumption, to prevent meaningful cogeneration. Fourth, they work on rolling credits rather than cash payments; any excess credits at year's end get zeroed out. At least they credit you at retail prices, which is better than many states. In Wyoming, grid-tied RE owners pay retail cost for the electricity they draw off the utility (~$0.080/kWh) but get credited wholesale cost (~$0.025) for the power they add to the grid. It's called "avoided cost": what it would cost the utility to generate that electricity from coal. Takes a long time to pay off an RE system at 2.5 cents per kWh. Michigan offers no money or tax breaks for residential RE systems. Looks like some individual utilities might. Here's THE clearinghouse for state and federal incentives: DSIRE.

02-19-09, 07:17 AM	#9
jwxr7 Apprentice EcoRenovator Join Date: Dec 2008 Location: mid michigan Posts: 191 Thanks: 0 Thanked 0 Times in 0 Posts	Bob, BTW, this skystream is using a guyed tower. I'm not interested in buying a skystream, just want to look at the tower and talk to the owner about dealing with Consumer's energy. I'm glad to see AE growing in my area.

02-19-09, 10:44 AM	#10
Higgy The Gardener Join Date: Oct 2008 Location: Manitoba - Canada Posts: 492 Thanks: 17 Thanked 8 Times in 7 Posts	You guys know like WAY too much about all this. After reading all this I feel like I just got geek slapped with a combo punch of aeronotics and physics. Remind me to have you guys flown out to my place when I'm going to get one of these set up.