Why no wind turbines powered by driving?

[okmunky]

Hi Y'all,

I will admit to being totally ignorant about wind turbine technology, but isn't there a way to generate electricity from the air that rushes by while we drive? I envision a small, very strong generator that sits atop the rv not any taller than the A/C unit that recharges batteries. Can it be done?

[Midniteoyl]

A regular wind turbine would self destruct at 60mph.. even 40. What your looking for is something called a Ram Air Turbine.. These are used as emergency generators on aircraft.. real expensive though..






Ram air turbine - Wikipedia, the free encyclopedia

[wa8yxm]

You could but it would be very inefficient to do it that way, the Alternator is as efficient as the wind turbine, In fact the standard wind turbine turns an alternator, but the power is transferred direct from the engine so there is nothing lost in the transfer to speak of (There is always some loss) where as to spin a turbine you send the power down the drive train and there is loss at every gear.

[okmunky]

It just seems that there must be additional green ways to charge house" batteries. I suppose if the idea was easy, someone would have cashed in on it by now -- or are we too small a group to warrant the R&D expense?

[Ray,IN]

Perhaps this is why solar panels for power is such a popular option.

[LVJ58]

I considered getting one of these to supplement my solar panels during dark hours, of course you need the wind.

Amazon.com: Sunforce 44444 12-Volt 400-Watt Wind Generator: Automotive

[pkmesser]

Okmunky;
There's an old saying that was quoted by one of the early SF writers, Isiacc Asimov, as I remember. "There ain't no free lunch". In this context, any wind generator, mounted on top of an RV, will cause drag. The engine will need to burn more gas to overcome the drag. As pointed out by others, the alternator is probably more efficient, the bottom line is that a wind turbine on top of your vehicle will burn more fuel than it will save.

That being said, I live where commercial wind generation was born in the early 80's. It peaked out at about 700 Megawatts capacity, only because there was no more transmission line capacity to take it to market. Last year, SoCalEdison, started putting in large transmission lines, and substations, so that the wind energy capacity could be expanded. They are putting in 4400 megawatts of transmission capacity, probably 1/3 of that has alreading been installed in terms of large wind turbines. (this is in about 8 months) The thought is that eventually the installed capacity will reach 10,000 megawatts here. For comparasion: One of the last generation of nuclear reactors installed in the US were 1100 magewatt Westinghouse. BTW, the wind turbines are installed, owned, and operated by private companys. The bigger turbines are on 100 meter towers, (328 ft) and have rotar diameters of 100 meters also, they are rated at 2500 or 3000 KW each. (The largest 747 has a wingspan of about 256 ft in comparison) We live in town, yesterday afternoon was slightly breezeir (sp?) than normal. At my house, the wind was constant between 35-38 mph, with gusts to 46 mph. Where the wind turbines are located, it would have been 50% higher than that. The wind is like that here, from sometime in March, until August, day and night, 7 days/week. The rest of the year will occassionaly have quiet days. During winter storms, it can get real windy!

I have agreed with a lot Midniteoyl writes in these forums, but he is wrong on stating that a wind turbine would self-destruct at 40 MPH wind speed. At that speed, the blades will have changed pitch so as to not extract as much energy from the wind, just like changeing the pitch on a airplane prop, they will be producing energy at the top capacity of the generator itself (depending on the wind regime the turbine was designed for, they will reach rated capacity at between about 27 and 32 MPH wind speed). In the 65-70 MPH range, at a predetermined cutout speed, each blade will go a totally neutral position, the rotar will then just turn very lazy like.
In the early days, some turbines that were of generation 1 & 2 (early designs) did self destruct, however those were at wind speeds in excess of 100 MPH. (the ridges here will see 125 mph+ every winter).

[Midniteoyl]

Quote:

I have agreed with a lot Midniteoyl writes in these forums, but he is wrong on stating that a wind turbine would self-destruct at 40 MPH wind speed.

I know.. but just impressing it would be harder, and more expensive, than the $400 mini's sold on Amazon or Harbor Freight. Besides, who drives at 40? The 'over speed' protection of these little guys usually kick in at about 35-40 mph, above that and they will just stall, producing no energy.. If the wind is right and fast enough, you can then put the blades into 'flutter' and destroy them..

An excerpt from a random pick of small wind turbine manual:

Quote:

The AIR-X also uses stall control of the blades, but the stall mode is activated by the controller before the flutter RPM is reached. The result is a dramatic reduction in RPM in wind speeds above 35 mph. The stall mode of the AIR-X reduces wear on the blades and bearings in high winds, and most importantly, it protects the turbine from damage from high winds. It does this quietly, without producing the flutter noise of the AIR 403. Stall mode is activated at about 35 mph (15.6 m/s), and will stay in effect until the wind speed drops below 32 mph (14.3 m/s). If the AIR-X senses wind speeds above 50 mph, it will shut down completely for 5 minutes. The AIR-X controller will blink the LED two times each second (slow blink) to indicate that it is in stall mode.

[HR-TX]

As a former Renewable Energy sales rep, I can say that this whole arena is incredibly interesting. In very general terms, the issue in all forms of wind and solar is price for performance received. Its good for the planet but tough to have a true long term payback that meets expectations.

The wind has great promise, expecially in light of new friction reducers that can extend maintenance intervals. The draw back has alway been that they are mechanical and require fairly expensive maintenance.

PV (Solar) is moving ahead by leaps and bounds. There are new technologies in PV that range from "silicone chipping" to transparent films to PV shingles. There is a test underway here in FL where they have clear PV producing energy which is installed on windows so there is no architectural impact. But again the issue keeping these technologoes from being mainstream is the cost vs return.

From a payback perspective, solar thermal (hot water) is by far the best of any renewable energy technology.

But to get back on topic, the biggest impact we are likely to see in the RV world will come from new battery / fuel cell technology. I flew in from Germany sitting next to an engineer from GM. In conversation I learned he was on the fuel cell team. When I asked how long before we could buy a fuel cell powered vehicle, he said we were more likely to buy a fuel cell powered notebook computer first. He said his team already has a notebook fuel cell (read the size of a notebook computer battery) that can run the computer for a year without refueling.

[wa8yxm]

Thanks PKMesser, You added nicely to my explnation.

For HR-TX.. I agree, but when parked, as PK (And I) said, the additional drag would be, well, a Drag, when driving.

One technology that I find interesting is the Thermocouple systems.. There is an RV furnace that uses it's waste heat to generate electricity via Thermocouple technology..Kind of expensive at the moment but a good use of waste. I'm thinking there may well be other ways to do much the same thing.. Use waste,, Example, exhaust heat (in fact I think there is a system like that too)

And I read of a system that uses "Regenerative Braking" This does not chrge the batteries as you drive (in fact it can discharge them if you like, adding the power of the batteries to the drive shaft) but it charges them when you gently apply the brakes (using the forward motion of the vehicle to generate electricity)

Some of this stuff is very exciting.

[okmunky]

Wow guys!!! The future of green energy looks exciting and I look forward to seeing new products for RVs. I drive a Toyota Prius. It uses regenerative technology to charge the batteries, right? I assume the weight and cost of the batteries makes a hybrid RV impractical, but I sure would like to reduce my potential carbon footprint.

I am 2 weeks away from becoming a full-timer. Not being the campground type, I am looking forward to boondocking without running the generator in my new motorhome. I enjoy tinkering and always have a "project" of some sort. Giving up the garage, back yard and larger tools will severely limit the scope of my future projects, tho.

I purchased a 272 watt, 12 volt flexible mat solar PV battery charging system from Green Solutions (thru Amazon.com) and plan to install it and extra batteries with my brother's help (and tools) as soon as I get a few obligations
out of the way.

I'm new to RVing and need to figuire out how things will work for me and
Sena, my 14 year old capuchin monkey. Living and traveling with a monkey adds a higher degree of difficulty to life so it may take a while. After things calm down a bit, I want to find innovative ways to replace gas generator use with green energy production to meet our power needs.

Wind energy interests me and I'm thinking it will reduce my battery needs if I could use wind during dark or cloudy times to keep fewer batteries charged.

[JMonroe]

My 1941 Taylorcraft (airplane) had a wind generator on it. The airplane's cruise speed was 90 to 100MPH. I took it off. Too much drag.

[ralper]

I have been thinking along this line. My thoughts were to funnel air into a warm air furnace type of squirrel cage fan to turn an alternator. I have just thought about it so far and that is probably where it will stay but if any of yo'all want to try let me know if it works decently.

[vermilye]

As others have mentioned, any energy you get from a wind turbine mounted on your vehicle while driving down the road will come from your engine, resulting in a net loss.

One interesting concept, particularly as roads get worse due to state financial problems is this Shock Absorber designed by a couple of MIT students. They claim each shock is capable of producing 1KW while driving on normal roads. The article is over 2 years old, & I haven't seen anything new on the concept, but 4 or more of these on a RV could generate some serious battery recharging!