DIY - New Paradigm

[Stewart Corman]

here is an article that was referenced on the AWEA forum:
http://www.bbc.co.uk/blogs/newsnight/2006/11/are_domestic_wind_turbines_an_ecocon.html

It points to several features which constitute my DIY paradigm:
note: I am NOT talking about charging banks of batteries with low voltage

1) for most rural locations, a residential unit of 15 foot diameter and WS at/above 12.5mph avg (15mph rated) is the minimal condition to make sufficient energy at competitive costs.
2) Electricity is 100% efficient, so convert all power into electric heat and use the residence as the thermal heat sink
3) tower costs can expensive and exceed turbine cost
4) for residential use, very expensive features such as tying into the grid are added generator/control/inverter expense ...rule is KISS
5) Current commercially avail units are NOT designed for low/moderate WS and as in the article above CANNOT be cost effective (scam?)
6)mechanical means must be applied to protect the turbine from "runaway" conditions in the event of a storm gust ...recent thread worth reading:
http://tech.groups.yahoo.com/group/awea-wind-home/message/20540

I am NOT an inventor, but rather an implementer .
I am researching a multirotor design, whose parameters need to be properly evaluated to define the operating envelope

specs:
http://www.geocities.com/scorman/turbine1.html?1168883247561

I have posted here before and have added a few pics/charts to my collection recently:

http://s145.photobucket.com/albums/r203/scorman1/Wind/
http://s145.photobucket.com/albums/r203/scorman1/Turbine%20project/

Blades are currently under construction (pics to follow)


I will maintain this thread to discuss progress, data, comments/ technical arguments related to this project

Stew Corman from sunny Endicott

[Rob Beckers]

Hi Stewart,

First off, I'll be very interested in following along with your project! So please keep this thread alive and let us know how it goes. By the way, rather than posting links you can also directly include pictures in your text (through attaching files, in the 'additional options' when you are composing text). Makes it easier to follow along and more interesting.

I wanted to comment on your points. Converting electricity to heat is usually the worst use of electricity. Yes, it is 100% efficient, but there are better ways to heat a house. Passive solar would be excellent, but even a ground-source heat-pump would make better use of the electricity (400% efficient!!) than just turning it into heat. In general, electricity is better put to use for things like lighting, pumping, electronics etc.

Towers for small wind turbines are generally indeed at least as expensive as the wind turbine that goes on them. At least, when one honestly adds costs of labor, footings etc.

The larger ones of what would still be considered 'small' wind turbines (say 5 - 10 kW) can produce meaningful amounts of energy even at lower wind speeds, and I know at least one that was optimized for low wind speeds. How is 410 kWh/month at an average wind speed of just 9 mph (at hub height). That is about as much as the average household in my native Netherlands uses. Of course, they come at a price, and payback at low wind speeds would be an issue.

Talking about cost-effective, or to use a better term, return-on-investment period, this very much depends on the price of electricity. As you probably know I peddle wind turbines. I've always been very upfront with cost and ROI, in fact you'll find tables on my Web site that calculate it in detail, using realistic costs. This table is taken from my Web site, it's in fact at the front page, and it lists return-on-investment. Prices are in Canadian dollars:

23

This uses current electricity and installation prices. The moral of that table is that if one can use the turbine for business use and has a reasonable amount of wind it can be cost-effective. At current electricity prices, at least in this country, it is rarely cost-effective for home use.

Now things look entirely different if electricity prices would go to 25 ct/kWh. Of course I don't know when that will happen, though I have a feeling it is not that far off. ROI for home use of that same turbine is now less than 20 years even for sites that have a fairly modest wind speed of 5 m/s at 10 meters (a value found in many places). The details of the calculations can be found at my Web site (http://www.solacity.com/economics.htm). There's no fudging here, these are realistic numbers to the best I know.

You are right that small wind turbines, towers, and inverters are very expensive. I believe this doesn't have to be the case. It really is a matter of scale. A wind turbine is not a very complicated device. Compared to a car it's outright simplistic, yet it costs as much as a small car. A similar argument goes for towers and inverters. If these things were produced in (much) larger quantities prices would go down very, very substantially IMO. Just as they have for cars. So, I believe there's a future for commercial small wind turbines. It's a matter of electricity getting more expensive and turbine production volumes going up.

-Rob-

[Stewart Corman]

In the previous post, I described a multirotor HAWT based upon a patented Allison design.

The original Pop Science article from 1980 was posted along with some projected data charts provided to me by Allison, as well as a performance chart for one demonstration configuration of a 20 ft turbine that ran for 6+ months as stated in that article:
http://s145.photobucket.com/albums/r203/scorman1/Wind/?action=view&current=AllisonPg64.jpg

There are three parameters which can be set which will ultimately determine at which WS the efficiency peaks and then the subsequent increasing falloff of efficiency until at such a point, increased WS will NOT cause an increase in rpm.

Since to raise and lower the 10+ foot turbine and rotate the spars, etc would be quite a laborious task each time a change is desired, and to wait for natural wind to collect data for each parameter would be very time consuming (if not impossible), I have constructed a bench model and artificial wind source to collect comparison data. There will be no attempt to use the bench model to predict absolute overall eficiency, just a comparison of one configuration to another as far as rpm,TSR, peak power output vs WS, runaway and/or self feathering effects.

details:
http://www.geocities.com/scorman/experiment.html?1168892956793

The wind souce is a 220v/14 inch high volume fan with VFD to vary the WS up to 60mph. It is calibrated by a Velometer 6000 pitot tube capable of reading up to 113mph. The experimental unit is comprised a 12 inch turbine with single or multiple rotors of 2 to 6 blades each, to which a 19v DC servo motor has been calibrated. Rotation speed of 3000 rpm has been demonstrated for a three blade single rotor experiment.

a few old photos:
http://s145.photobucket.com/albums/r203/scorman1/Experiment/

It is desired to compare conventional 2 and 3 blade designs against Allison's various configurations, both at similar pitch and at optimum pitch.
After the 2 blade x 3 rotor configuration has been optimized for the three key parameters, then the 10+foot unit on the 25 ft tower will be similarly configured and field tested for comparison.

I am working on a means to mold sample blades to be able to better replicate multiple blades, since I need as many as ten at one time.

We can discuss various features of this project as far as implementation or philosophy, as well as construction techniques.

I am willing to consider additions to my experiment as time permits, just to prevent the NIH crowd from saying "BUT, you didn't consider ?"

Stew Corman from sunny Endicott

[Stewart Corman]

Hi Steward,

Rob starting out on the wrong foot already (second time) ...drop the "d' and replace with "t";)

By the way, rather than posting links you can also directly include pictures in your text (through attaching files, in the 'additional options' when you are composing text). Makes it easier to follow along and more interesting.

I need to be able to edit out old or edit in new pics at my convenience ..I'll use links

I wanted to comment on your points. Converting electricity to heat is usually the worst use of electricity. Yes, it is 100% efficient, but there are better ways to heat a house. Passive solar would be excellent, but even a ground-source heat-pump would make better use of the electricity (400% efficient!!) than just turning it into heat. In general, electricity is better put to use for things like lighting, pumping, electronics etc.

missed my point ...once you have a turbine up, resistance heating is the most efficient use of what it produces ..converting has losses ...my biggest problem in the middle of the winter would be having to open the windows because the house got too warm! Have a grid enabled system is the worst payback I can see.


I know at least one that was optimized for low wind speeds. How is 410 kWh/month at an average wind speed of just 9 mph (at hub height). That is about as much as the average household in my native Netherlands uses.


Give me a link to that model and/or specs ...
BTW , I use 1000KW /mo @$0.13/KWhr w/o heating (domestic hot water and stove is electric) ..consumption of 1000gal fuel oil OR 5 full cord wood to heat all winter


Talking about cost-effective, or to use a better term, return-on-investment period, this very much depends on the price of electricity. As you probably know I peddle wind turbines.

sorry, I hadn't realized that you were in the business
maybe if my experiment is successful, we could start a business up there
BTW, Allison's patents have long expired

If you look at Allison's design and my implementation of it, the cost to build a 15 ft unit could be quite reasonable ...I have a source for custom "pancake" 2KW direct drive generators, and the build of fiberglass blades on a spar can be contracted out. Claus Nybroe makes his own for the Windflower:
http://www.windmission.dk/workshop/bladeprod.html
BTW excellent site to read every page, especially blade design

I will keep this thread alive IF, if you start spelling my name correctly :)
Stew Corman from sunny Endicott

[Lion Kuntz]

Look at this:
http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=5,823,749
http://www.google.com/patents?q=5823749&btnG=Search+Patents


http://www.greenwindmill.com/
http://www.greenwindmill.com/plans_and_kits.htm

[Stewart Corman]

Lion,
Never saw that one before ..good find

First comment is that most complain that Allison's multirotor turns too slowly (1/2 speed) making it difficult to implement a generator that can produce high voltage.

Vertical units typically only have a TSR of <1, so the larger it gets (in diameter), the slower it runs ..that is not to say that an axial direct drive generator can't be designed properly

Now that you tweaked me ... I can see a Darrius straight rigid blade replaced by a main/jib constructed of nylon sails and fiberglass struts (tent poles?) and stays. BUT, could the TSR >1???? good question ....a sailboat goes faster than the wind that drives it when in a tack direction.

It would be extremely lightweight in construction and if allowed to partially pivot, the drag on the upwind side could be minimized. It could be quite large in cross-section and height, so losing 1/2 the available wind can be easily accomodated by making it twice as big. I can picture 10 foot high sail edge with 5 foot span on each side, so effect area is 50sqft equiv to an 8ft HAWT which has 500watt max power at 12.5mph and 2KW at 20mph WS

No idea what kind of efficiency these things could produce (multiply eff % times max values above) but if the rotor and tower were inexpensive enough ...could be an argument for it

OT - Rob: is there a way to attach an Excel file to the thread?
I have a spread sheet which calculates max power (above numbers) at any WS for any Diameter, and RPM vs TSR for any WS


Stew Corman from sunny Endicott

[Rob Beckers]

OT - Rob: is there a way to attach an Excel file to the thread?
I have a spread sheet which calculates max power (above numbers) at any WS for any Diameter, and RPM vs TSR for any WS

Certainly!
When you're composing a message there is a window below it with the title 'Additional options'. In there is a button named 'Manage attachments', hit that one. From the attachment manager, use the 'Browse' button to select the file you want to attach, hit 'Upload', and close the window. It's now attached to the message you're typing.

-Rob-

[Stewart Corman]

I am attempting to make available a simple spread sheet that calculates the max power available in the wind (KW) for a specific diameter HAWT (swept area) as a function of WS (mph).
where you see a "?", you can put in a customized value

Also included are a means to determine the rotational speed in rpm for any given TSR and WS. Tip speed is simply WS x TSR which is trivial and left off

Why should we bother?
Every time a new press release touts the latest and greatest ala Skystream 3.7 and they have an oddball swept area and oddball rated WS and then show a performance chart ...I always take out the calculator to see how fast those tips are whipping by and what efficiency they claim at diff WS.

working on other blade geometry related spread sheets for my experiment

Stew Corman from sunny Endicott

[Stewart Corman]

Thanks Rob ...nice feature

BTW, you owe me a link to that turbine that you mentioned:
The larger ones of what would still be considered 'small' wind turbines (say 5 - 10 kW) can produce meaningful amounts of energy even at lower wind speeds, and I know at least one that was optimized for low wind speeds. How is 410 kWh/month at an average wind speed of just 9 mph (at hub height).


hmm, that quote tab works too :rolleyes:

Stew Corman from sunny Endicott

[Rob Beckers]

Thanks Rob ...nice feature

BTW, you owe me a link to that turbine that you mentioned:



hmm, that quote tab works too :rolleyes:

Stew Corman from sunny Endicott

Hi Stew (from now on I'll stick to Stew, less chance to mess up with that! :D ),

Actually my 'signature' at the bottom of every message points to the site with the turbine I mentioned. I thought you'd have found it by now. It's Eoltec's Scirocco (http://www.solacity.com/Scirocco.htm). It is a fairly conventional HAWT (in view of some of the others mentioned on this forum). What makes it special is that it is variable pitch, with a governor controlling RPM. So no diversion load, no self-destruct in high winds even if unloaded, low RPM, low TSR, and very efficient in low winds for what's still considered a small turbine (as opposed to the big guys, 50 kW and up, which tend to have much better efficiency numbers than almost all the small guys).

-Rob-

[Stewart Corman]

Rob,
Yes, I had seen those spec sheets but hadn't realized it was what you were referring to in the thread.

Quick check of their ad chart has numbers showing 1KW at 5.6m/s (12.5mph) for a rotor diameter of 18.4 ft which has the max avail power of 2.6KW, so 38% efficiency ..that is probably as good as I have seen and compares favorably to even the huge turbines. But as you had mentioned earlier ...too expensive for residential ROI ..that is an expensive piece of hardware

Stew Corman from sunny Endicott

OT -- if you are compiling a set of reference links, here is a really good tutorial about blade design/calculations that was just passed to me:
http://www.dreesecode.com/
"Airfoil Primer 2007"

If you want to organize such a reference as a new section on your site ..contact me and I'll send you a long list catalogged by subject

[Rob Beckers]

Quick check of their ad chart has numbers showing 1KW at 5.6m/s (12.5mph) for a rotor diameter of 18.4 ft which has the max avail power of 2.6KW, so 38% efficiency ..that is probably as good as I have seen and compares favorably to even the huge turbines.

Actually I made a little table with efficiency numbers (http://www.solacity.com/MoreScirocco.htm) at various wind speeds. For that I've used a more realistic derating of 10% of 'published' power, just as for all the production numbers on my site. At 5.6 m/s the published power is around 950 Watt, so derated power is 855 Watt. That makes for a more realistic efficiency number of 32%. That's still very good for a small wind turbine, most won't get there, but not an unrealistically high 38% (there's no small turbine I know about with that kind of efficiency at any wind speed). To get an idea of efficiency numbers Paul Gipe's book has a table with various small and large turbines compared, at various wind speeds.

Anyway, I don't want to get this thread off-topic. Just wanted to keep the record straight, and not get any unrealistic claims out there...

-Rob-