Picture of Parasitic Wind Turbine
This was built as a lark, a whimsical attempt to recapture some of the hundreds of dollars I spend on air conditioning each year. It's a wind turbine powered by the compressor fan on my air conditioning unit.
But, It is a ponderable notion. And you could reverse the rotor, add a tail and yaw bearing and make a regular wind turbine.

Step 1: The alternator

Picture of The alternator
I started off by messing around with a stepper motor I had, it was rated 6 volts 0.4 Amps per phase and was a two phase motor, meaning max input would be 4.8 watts. So running it backwards could I get that much out?

I'm not really an electronics guy, so I stuck my meter in AC mode across the terminals, spun it with my fingers, and got a reading of 50 volts! On current it read .2 amps. Umm okay, never mind the meter, would it light LEDs?

So wanting to see if it would light LEDs I wired 5 red LEDs together, four as a full wave bridge rectifier and the fifth as the load. As you can see in the video and pics, it had no problem lighting those LEDs, nor the five super bright white LEDs arranged in the same manner.

nudim24 days ago

very innovative idea ... thanks for sharing

hargee5 years ago
I'm sure the extra load on the AC is negligible since, with the turbine on top, in open air, it is not a closed system. Unlike the turbo which has a restricting conduit that does not give the exhaust an alternative path to spooling the turbine.
rgerber1 hargee26 days ago

I agree, I believe the unit is already loaded by " Sucking" air through the coils.. the fan appears high enough to not restrict the air flow out of the collar of the unit ( for lack of a better word, much like the back side of a house fan, at least on my ac unit it has a cone in which the fan sits slightly in front of)

bob88982 months ago

Soooo.... I dont know that much about steppers... Whats single phase vs. dual phase? Also with a stepper that i know has 2 dc power inputs, would those 2 dc inputs (when the stepper is used as a generator) output dc? or AC? if ac... HOW DO I MAKE A FULL WAVE BRIDGE RECTIFIER?

you can check You tube or perhaps search here, a full wave Bridge will change AC into DC Current. I am sure Wikipedia has something on the subject also.

mgalyean2 years ago
It would be more efficient to just run the LEDs from a wall power supply because you are robbing Peter to pay Paul. You are making the A/C blower motor work a bit harder by putting that resistance over it. The A/C blower only runs when the A/C condenser coils reach a certain temperature. By putting resistance in the path of the cooling air, you are just delaying the blower motor from shutting off by some amount and make it run longer. You need to make the system do *less* work, not *more*, to get a savings. In dry climates, I've used a water mist on the intake air into the A/C outdoor condenser unit to make the heat exchange more efficient. This allowed the A/C to run more efficiently. At the cost of the water I was spraying anyway. There is no free lunch.

My thought exactly on adding resistance to the condenser motor. Spraying water on the condenser coils will certainly improve the system, but at the risk of leaving hard water deposits fouling the coils.

Hard water. Good point. Maybe I should have taken the condensate from the inside evaporator and sprayed that water instead as it should be much more scale free than tap water having lost the scale when it became humidity in the air.

javierkayaker8 months ago


I stuck an old 140mm PC fan over my Trane unit and at best generated 4v at 20ma. Cool idea, I'm gonna build by own with a 200mm fan.

paqrat4 years ago
I must admit to not knowing much of anything about this but wouldn't it be more efficient if the blades of the fan were parallel to the exaust fan of the ac?

I got the idea for using a fan when, a few years ago, I bought a small electric fan and walking to the car I noticed the breeze I was generating by walking slowly was spinning the blades of the fan.
nav_lexy4 years ago
What about adding two more at 1/3 of the angle? Like a PEACE sign
I was mislead by the amount of torque you were applying to light the LED's, -and I want to know how hard the wind was blowing for this picture.
I have some steppers laying-around, and your 'ible has got me thinkin'!!!

All I can say comes from the fertile-mind of Robert Heinlein:
whitten_jaw4 years ago
To answer your question about phases. Two voltages are only 'summing' if their phases are the same. 180 degrees out of phase would be subtractive, so you would get less power out. 90 Degrees out of phase would give you no effect. You may be better to generate two DC outputs and put those in series (provided that the source resistance is high enough). The other alternative is to look up inductors and capacitors and their corresponding phaser math to offset your motor phases enough to make them additive. I hope that gets you started--doing the vector math isn't hard when you have the circuit in front of you... if my memory serves me right, capacitors are:

Z = -[j]/ [(omega)*(Capacitance) or Z = 1/[(omega)*(Cap)] < -90 degrees
and an inductor is

Z = [j]*(omega)*(inductance) or Z = (omega)*(Ind) < +90 degrees
kenmneth4 years ago
if you want something to work on then try this take a mirrored satellite dish and put in the center of it a mirrored tube at the focal point must be a mirrored cone shape or small dish your choice sending the light down the mirrored tube into the basement straight into the mirrored box i am using a frig, solar panels are inside of frig i used rollers from a desk to slide solar panels back and forth for cleaning if they need it .small fan takes the hot air out cooling system will cause sweat sending the light into the mirrored box is a GOOD IDEA BUT NOT THE GREAT ONE I AM WORKING NOW.
SNUFFY37244 years ago
OK, I'm just a housewife, never studied thermodynamics or physics, so don't rake me over the coals. In NC, I use my heat pump AC from March (sparingly) to November (again sparingly), with the heaviest usages from last week of April to 3rd week of October. In the worst part of the year, the AC runs CONSTANTLY - not only heating, but pulling out humidity. My condenser unit is under my deck, on purpose, to eliminate freezing over when we get our wonderful ice storms. There is a six foot clearance vertically, and I can tell you when I walk across that part of the deck, especially in a skirt, there is still a strong wind current - certainly enough to power a turbine. I bought a unit a full 1/2 ton larger than my neighbors ( I have 3080 sq/ft heated space, so I got a 4 ton unit), which only cost me about $100 more, and my electric bill is always, year round, cheaper than my neighbors by 10% +/-; my EPP is $199/mo., and the 12th month they always owe me, most years I only pay 10 1/2 months of electricity. I haven't even thought about salvaging the heat loss, because it seems to me it would be complicated and expensive, but maybe that's just me being ignorant. But seriously, if you're wont to create a wind generator, in my climate, this would be an absolutely dependable source of 'wind' to power one, and you wouldn't have to worry about damage due to the HAWT or VAWT being too close to the unit - 6 feet will still 'get her done'! This instructable is the closest thing I've seen to date for someone thinking to salvage this unused energy. Get to work boys, I want to see something real - I'm closing in on retirement, and I still can't get rid of the kids and their electronics.
where can i buy the generator thingy? ive been lookign around and cant find it.
dallasmel5 years ago
All the comment relate to the 2nd law of thermodynamics.  The resultant of any process will always be less that the amount of energy you put into it!

You tap energy off a condensing unit, you'll get less energy out of your process, and increase the amount of energy the condenser uses.  There's just no way around it!  There's no such thing as 'free energy".

'honeybees can't fly per law of aerodynamics'
dm, the energy being tapped is the dump/waste heat energy. there is no strain on the condenserunit as it is designed to push air away from said unit to remove the excess temperature, aka cooling effect.
if anything. the small fan blade assists in moving the air by deflecting it.

I would have thought that the fan on top once it got going if it had no load or very little load, it would have helped to draw the air away from the AC unit's fan because it would be pulling air upwards to keep it spinning?
Honeybees can fly per the laws of thermodynamics.  For example, if you quit feeding a honebee, it eventually won't be able to fly (a process), and the second law of thermodynamics state the resultant of a process is alway less than the amount of energy put into it!  Starve yourself for a week and try doing the same amount of work you did before.  Same principle.

Not only does the condenser fan remove heat from the condenser via "forced convection", the system in which it operates is essentially fixed, and fan laws for a fixed system with turbulent flow applies.  The change in air-horsepower as a function of a change in the system resistance of such flow (eg: more restrictive as a result of placing your device in the airstream) changes as a linear funciton if assuming constant mass flowrate.

Strain is a change in length over a unit length, and as a result of compression or tension of a member.  Strain does not apply to a machine, in this case a heat pumping machine.  You restrict airflow in a heat pumping machine, you will encounter an increase in the delta-Temperature (ie: leaving-entering air temperature) at a constant heat transfer rate according to a Sensible heat transfer (ie: another process). 

The First, Second, and Third Laws of Thermodynamics apply to everything.  There's no way you ... or a honeybee can get around it.
this device is utilizing the exhaust not the intake and was discussed
in the comments with trebuchet in june 2008. please read.
Intake, Exhaust, it doesn't matter ... they are both part of the "system" in which the airflow is operating, and it is related to principles of continuity of mass, momentum, etc.

I typically don't like to use an "appeal to authority" argument ... but since you have .... 

I see this as being a little misunderstanding about the law of thermodynamics, the fan laws, laws involving the continuity of mass, etc.  ... in general, Laws of Nature/Physics ... not Man-made laws.  Even with a minor misunderstanding of the Laws of Nature/Physics, the probably of Rub-Goldberg devices being proposed into society increases expotentially. 

If you truly think you have engineered a devise that does not tap energy off of the condenser, then add several of your devices to the condenser outlet ... and do it again ... and again ... and again ... allowing you to save enough energy to bill back the utility companies.  You'd be creating energy!!!! (a violation of the First Law of Thermodynamics).

It won't and can't happen, and because of the Laws of Thermodynamics.

Mel Presswood, P.E. ... I've been involved with pumping heat, thermodynamics, HVAC, and environmental control systems for over 40-years .. my "Appeal to Authority" argument.
The point most people are missing (which you are dutifully trying to explain) is that putting a load on the back end of the system is still putting a load on the system.

Basically what adding a turbine to your AC exhaust does is literally make it harder for the AC unit to push the exhaust air out. This will result in one of two things as it relates to the AC unit (and these are the only options): if it's a relatively smart exhaust fan, it will increase it's speed to compensate for the lost air movement. If it's a dumb fan, it will keep cranking at the same speed/power, and the cooling capability of your unit will be decreased. Your AC unit will have to run longer to hit your target temperature, because it cannot cool quite as fast.

If you think it through a little bit, you just have to extrapolate from what you know to understand it won't save you anything. Start with the extreme of covering the AC unit. The heat exhaust is critical to cooling the house, so your AC unit does not cool anything without a way to exhaust the heat. Lifting the cover slightly to allow a small amount of air through will allow the unit to begin cooling, but it won't work well at all. Lift the cover further - say a foot or so - and you've got heavy restriction but it is really starting to cool things down. Lift the cover to 10 feet and it will run at almost peak efficiency, but you also have very little air flow.

Putting a turbine on the back of your AC unit is exactly the same as partially covering it. It adds restriction to the air flow, which means it cannot exhaust the heat as well, which means it loses efficiency.
gentlemen, what both of you are explaining is applicable to a 'closed' system, where the air is going thru ducting in a closed cycle similar to central heating systems. it has minimal impact on an 'open' system which is being tapped by this device.
It applies to both a closed and an open system. Adding anything to the back end of that exhaust fan increases the resistance on the air moving out. Since the point of the air moving out in the first place is to dissipate waste heat, anything that slows that air down is going to slow the heat dissipation as well, which means the exhaust system works less efficiently.

The exact same thing can be seen in reverse in high power carburated engines. Hot rod builders remove the air filter to increase the flow, but they also cut holes in the roof and install flared intake pipes to maximize the air flow.

With no holes, it's still an open system. Air flows freely through the radiator and from under the car, into the intake which provides oxygen to the engine to burn the fuel. Cutting holes in the hood of the car alone increases the air flow, which means the engine has more oxygen for burning fuel. To maximize the air flow, they then add specially engineered flared intake pipes, which provide the best possible air flow into the engine.

They do the exact same thing with the exhaust, putting wide, straight pipes out from the engine to maximize the flow.

Obviously the AC unit isn't that precisely engineered, however any obstruction reduces the ability of the air to dissipate heat, which reduces the efficiency of the AC unit. At the same time, the obstruction makes the air being pushed out more difficult to push, so the fan either pushes out slightly less air or uses more electricity to push the air out a little faster, depending on how smart the fan is.  The only difference between an obstruction inside a sealed tube attached to the exhaust and an obstruction sitting in the open air outside the exhaust is the amount of potential loss it can create.  They both create a loss in efficiency, which cannot be recovered because the turbine is not even remotely close to 100% efficient.  The laws of thermodynamics are pretty clear on this one, even if you don't see the relationship.

The only way I could see this being of any benefit is if you aren't the one paying for the electricity to run the AC. In that case, it's incredibly unethical, but it will result in a net gain for you (but not overall).  And then, if you're going to do it, you might as well seal it off, because you'll collect a whole lot more energy that way.
Look out everybody! It's the battle of the Physics egos. Kindly stop behaving like a gaggle of self-righteous quacks or we'll have to take your magnadoodles away, you bumblebee haters. Personally, I'd like to know if you could use the motor out of an old fan to make some electricity.
Absolutely, but you'll need high RPMs to get any electricity out of it because of the motor design - the metal of the electromagnet will want to stick to the permanent magnets and you need to overcome that. You could roll your own generator pretty easily that would generate electricity at much lower RPMs (which is what you are more likely to be dealing with). All you need are some properly wound induction coils (how they are wound will depend on your setup) sitting in a circle on a board or other flat plate, and some permanent magnets in a circle on another board. Put a drive shaft between the two circles and suspend the magnets above the induction coils as close as you can without touching, and then just spin the top plate. You'll get AC current flowing through the circuit on the induction coil side. You can hook that up to a wind turbine or any other rotating device and generate electricity. And cheap too.
Thanks Big Jeff. If you know of an instructable I could use as a reference, it would be greatly appreciated. I really like the concept of producing electricity with these things. I hope I can adapt it up here in big breeze country to my benefit.
So by tapping geothermal power, you're saying we're aging the planet by working it too hard? By using solar power, we're causing the sun to use more power as well so we're helping it to burn out sooner? Heh.
The laws of thermodynamics do not know if you are simply heating your yard's air with the 'waste' heat or your house. There is no violation of any laws of thermodynamics by using the waste heat. How silly.
@Dave - I agree totally. Dallas you are missing some key elements.. A condenser works BETTER when the heat can be dissipated faster. Think of your fridge, when the condensor gets dusty and dirty, and even the fact that it is crammed into a hole against the wall... these all fight the process. If you capture heat waste and re-use it, you actually IMPROVE the process, if anything. In fact this technology is taking the world by storm, do your homework. Volkswagen are in bed with a West German power company, with over 300,000 installations.
One of the simplest and best examples I've seen was an article about 10 years ago about homes built in Italy in mountain areas with no electricity. It mentioned a small generator used for pumping water into a storage tank, lights, and charging batteries. The generator manufacturer sold a heat exchanger unit that used the exhaust heat (where about 80% of the heat from the engine is usually wasted) to heat an insulated water tank for heat later, washing, etc.
It wouldn't take very sophisticated technology to do this anywhere with even the most primitive set up, although if it is an Italian design it probably looks good, too!
Very Cool! I think you will see a lot of people putting their heat pumps inside of solar collector rooms, or small "sun rooms" if you will... why not? That heat pump is working hard outside to try and do it's job, all winter long. It makes no sense to NOT have the sun help it out. I believe that a lot of people are quick to jump to an incorrect assumption: free energy, overunity - they are not the same thing as COP>1. A co-efficient of performance greater than one, has nothing to do with breaking the laws of physics (dallasmel: There's no such thing as 'free energy".) We are, in fact not even talking about free energy, at all period. If you spun your fan generator by hand, you'd get some juice. By capturing the waste "wind" you are putting that generator COP>1, you don't have to spin it. The air movement upwards, from the AC fan, is only very very slightly affected by this restriction, and that does cost a little bit, HOWEVER - that is offset by the fact that the secondary fan is helping to remove heat FASTER, which in theory will make the lower fan operate less often, in the first place.
You obviously do not have a working appreciation for the Laws of Thermodynamics to make such a statement. I highly recommend you talk to a High School/College Physis professor for clarification. Even waste heat dosen't get there by itself. It's the inefficient resultant of a "process", and as dictated by the 2nd Law of Thermodynamics. A reviewer had previeously made a suggestion to use your neighbor's condensing unit to power the device (acknowledged unethyical). But ... it wouldn't be you paying for the waste heat to power your device. It would be your neighbor. Wind turbines are in reality powered by the nuclear reaction occurring on our Sun. That reaction heats our planet and causes air to move ... subsequently powering our wind generators ... and generating electricity. All along the way in the process ... energy is being converted from one form to another ... and at each conversion process ... an inefficiency is generated. Try powering a motor with a generator that powers the motor. It dosn't work ... and can't work ... and because of the 2nd Law of Thermodynamics. A parasitic generator is powered by waste heat .... but something has to move that waste heat .... or the parasitic generator cannot work. If you place the parasitic generator in the air path of a condensing unit, the system in which the air-moving device (in the condenser) operates changes (becomes more resistive). Subsequently, the air-moving device will move less air, resulting a higher condensing temperature, less ability to remove heat from the home, and increase electrical usage, an example of the 2nd Law of Thermo.
I have taken several years of college physics and yes I do understand the basics. You brought up a bunch of scenarios that I did not support or even imply. I was not implying using the parasitic fan or stealing from my neighbor, both ideas that are a bit silly in my book but at least the person is trying to make it more efficient. All I said was that there are other things to do with waste heat than heat the air above the condenser. No laws would be broken building a properly designed heat exchange unit. I was talking about recovering waste heat which is a very common thing to do as any engineer that deals with industrial processes will tell you. Picture the waste heat going out of the condenser into a building for example. There is no net change in the energy consumption, you are simply putting the waste heat to use. If you look at industrial processes you will find that heat exchangers are extremely common in order to retrieve heat that would normally be wasted. They improve the overall efficiency of a large number of industrial processes without violating any laws of thermodynamics. I suggest you look into the engineering of heat exchangers in industrial processes if you would like to gain an understanding of the myriad practical uses of such a device. I have worked with them in industrial conditions and they are not put there by engineers that don't understand thermodynamics, they are used to recover energy that otherwise would go to waste and put it good use, almost always to save money despite their considerable costs. I am trying to bring practical information to this discussion so that all of us can see possibilities through proper use of technology, not win an argument.
So your taking waste heat and using it in a process, that of recovering a portion of the heat that was formerly being wasted. By definition, it is no longer waste heat if your putting it to work. In addition to having over 41 years of HVAC, Thermo, environmental control systems, etc. under my belt, I have done rocket science, and I am a certified commercial energy plans examiner and inspector. The point I have attempted to make is that you can't get something for nothing. You can't power the wind generator with the the discharge of a condensing unit without imposing additional energy requirement on the prime mover (the air-moving device in the condenser, and compressor since a decrease in the flowrate of air in a more restrictive system will decrease it's ability to pump heat due to higher condensing pressure ... which will also raise the staturated suction pressure and temperature in the evaporator ... also decreasing the ability of the evaporator to absorb heat. I'm quite familiar with energy conservation and recovery principles, and have engineered several such systems. Look up the term "specific speed". It's an engineering principle used to minimize the energy consuption of engineered systems utilizing rotary driven fans, pumps, etc. I believe you have some misunderstanding of the Laws of Thermodynamics, and probably because of the scope that the laws apply. The First Law says that energy can be converted from one form to another (eg: heat, potential, dynamic, etc.). The Second Law says that during any energy conversion process, the resultant of the process will always be less than the amount of energy put into it. Subsequently, waste energy (or heat if you like) is created. If you tap into that waste energy to use it, it's another process ... and if that process affects the prior process that created waste energy ... then you've also affected the prior process. If you use waste energy from the 1st process for a 2nd process, then by definition, it isn't waste heat anymore, and the second process will create it's own waste heat. The argument you've been giving regarding waste heat from a condensing unit, also supported by a photo of a air-powered generator mounted atop a condensing unit will affect the prior process because it affects the system in which the condenser air-moving device operates, which will affect compressor operation, which will affect evaporator operation.
A heat pump moves heat from one side of a device to the other. In the case of AC we want to use the cold side to cool a space and we need a heat sink, in this case the outside environment, to absorb the heat. If we wanted to heat a space, we would use the hot side to warm a space by pumping heat from somewhere, in this case the outside environment. A defined amount of work is done moving the heat. If I want a cool house and warm water, the water being the heat sink instead of my 100 degree yard, the same amount of work is done. It is simply a different heat sink, water instead of air. Why does using both sides, the cool side and the heat sink, violate laws of thermodynamics? How do the laws change due to my intent in designing the system differently by using water instead of air? Isn't a heat sink a heat sink? BTW - I enjoy an exchange of ideas as much as the next person but please notice that I have not supported the idea of the fan as described above. I have no idea why you feel I am defending it. You're analysis of the problem associated with it is basically correct.
When I talk of pumping heat, I'm referring to the energy level within the substance I'm pumping. It doesn't matter if it's hot, cold, etc. ... it contains heat as long as it's above absolute zero. My argument has to do with changing the system in which the pumping of heat occurs, and in order to utilize the total heat (evaporator heat + compressor heat) of rejection of the condensing unit. It's not so much as you'd be using the heat rejected to power an air-driven generator as you'd be influencing the mass airflow through the outdoor condensing unit. They heat pumping process is not a batch process (the heat has already been removed from the home?). It's a continuous process as long as the HVAC system is operating. You cannot power something with nothing. The system in which the air-moving device operate will be impared (made more restrictives). Subsequently, the ability of the device to pump heat will be compromised. My analysis is correct ... there's nothing "basically" about it. I enjoy this site as much as you ... and I hope my comments are taken as constructive critizism. I've nothing else to render regarding this subject, and will not be responding to any further comments. I've Clients that expect results ... GO FIGURE ... so it's back to work for me. Regards!
Again, I am not talking about using the unit as designed and constricting the air flow which obviously would change the dynamics of the system. I am talking about better design so that you use both sides of the heat pump. Even as designed, hanging a pot of water 6 feet above the unit to heat some water instead of air would neither affect the unit or violate any law of thermodynamics while at the same time it would use so-called 'waste heat' for a practical purpose. I saw a generator on a house in Italy that provided electricity from the generator along with hot water and house heat from the exhaust. It did not use a drop more diesel or provide less electricity than the same model generator without the heat exchanger, it simply cost more for the heat exchanger. Use the heat sink. Nothing can be made 100% efficient but nature does not differentiate between heat and 'waste' heat. It has to go somewhere so let's use it.
dave5706 years ago
i think u guys are assuming the a/c fan is drawing downward thru the fan thus restricting air flow to the ac fan/ how ever my ac unit draws air UP thru the sides tthru the condencer THEN out thru the top...in my case this is not causing any undo resistance to the ac motor, as all the air movemnet thru th ac unit is complete.
Sorry, inlet or outlet, it is still adding to the load on the fan. Block up the exhaust end of your vacuum cleaner and then see how well it sucks. The above arguments about using the waste heat from the condensor for another purpose than further heating summer-air are more realistic, e.g., heating the shower, dishwasher or maybe even the oven...
Grichey55 years ago
Wow! I am not sure if I want to leave a comment or not. I would not wan to insult any engineers. I currently work in Energy management for large industrial and commercial buildings and complexes. I do not believe that this will cause your AC compressor in negligible difference in power usage. Your idea is in fact already being considered on large air cooled chiller systems. I got a chuckle when I saw your little version here. No doubt the energy you recover will be less than the energy put into it. I have worked on many jobs that have us spending millions of dollars pursuing all of that wasted energy that Mel finds so ridiculous. We are doing it more and more and there are huge financial incentives to do it for large commercial buildings. Obviously if it was not worth the effort so much money would not be spent on it. I am sure the purpose of your project was not to bruise the ego of an engineer. I work with engineers all of the time and I find most are now consulting engineers. That is code for not my fault if it don't work. Experimentation is a good thing and SHOULD be encouraged. Is that not the purpose of a site like this?
shortw5 years ago
Well, I just figured it out.
It would take about 700 hrs to generate 1000 watts. 1000 watts is about 18 cents savings.
700 hrs. is about 2 month air conditioner operation in the summer. Remember air-conditioners are matched to be 1/2 time, meaning they will be on for 15 minutes and then off for 15 minutes.
You have about $ 20 in plastic ware in your project without the stepping motor.
You would have to produce 111,000 watts to break even. That is 222 month of operation.
Since we run air conditioners only summers, I use the 6 month rule.
222 month is about 37 years just to break even without any repairs.

There is only one problem, In order to get the wattage out the stepping motor, the condensing motor uses about 5-10 watts more per hr. than what you get out of the stepping motor.

You would save more money by using the heat of the condenser to heat water.
Just think,
1 ton in AC terms is 12000 BTU per hour.
My AC is a  1 1/2 ton unit or 18000 BTU. 18000 BTU is about 6000 watts per hour.
Remember air-conditioners are matched or designed to be 1/2 time, meaning they will be on for 15 minutes and then off for 15 minutes.
So the 6000 watts per hour going down to 3000 watts.
We all know that you can not regain 100 % of the heat, but lets say 50 % of the heat that would be 1500 watts per hour.
The heat can be stored in water tanks.
1 lb of water heated up 1 degree is 1 BTU.
If you have a water tank with 40 gallon ( 8.5 lb per gallon)  and you increase the temperature by 80 degrees you can store the energy.
40 X 8.5 X 80 = 27200 BTU = 9066 watts.

This would cost more than your design, but could pay for it self within a few month especially if you are able to make it yourself.

necromncr7 years ago
Wait. Isn't the fan pushing the air doing some work? And if you put a fan in the path of the air being pushed, don't you increase the load the pushing fan has to do? In that case, you actually make energy from increase of power consumption of the fan which means larger bill. I might be talking jiberish, my tea didn't kick in yet, please be nice.
Think of a turbo-charger on a car. Yes it pushes back on the engine, but it gives more than it takes because w/o the turbo-charger ALL of the energy in the exhaust is wasted.
shortw bwcbwc5 years ago
That statement is false.
The exhaust is turning the turbo charger.
The turbo charger pushing more air into the intake and cylinders of engines.
But also , because more air is put in the engine more gasoline is required to make the engines or gasoline / air-mixture to fire. The extra gasoline will give it more power, not the exhaust.
doryrhp bwcbwc6 years ago
Turbo-chargers do not improve the efficiency of an engine, in fact they generally lower the overall efficiency of an engine (more gallons of fuel per horsepower). Turbos only improve the volumetric efficiency of an engine, allowing the engine to burn more fuel-air mixture (since the mixture is pre-compressed) than a naturally aspirated engine. The turbo essentially allows a small displacement engine to produce power similar to a larger displacement engine (which is why they are so popular, large engine power, with a small engine weight and size). The set-up in this Instructable is most likely forcing the motor running the fan to draw more power than what the turban and alternator are producing. One method to improve the efficiency would be to make sure the fan is compressing only cool, fresh air, then forcing the air past the hot compressor motor and condenser before exhausting it through the turbine. With this method the AC unit and turbine would essentially be acting as a jet engine! Of course for the AC-jet engine to work you would most likely need some serious aerodynamic ducting and compressor/condenser streamlining to reduce frictional losses in the unit. You might also need to start out with a larger AC unit since running the compressor and condenser in a hot environment would likely reduce the amount of cooling power available to your house!
That's exactly right. See Treb's accurate explanation in the thread. I'll paraphrase it: You don't get anything free, because by putting something in the way of the airflow, the fan has to work harder to do the same cooling it was doing before you put the new fan on top and reduced the airflow.
i think the power loss is negligible as the air is already out of the unit. Now if there was ductwork forcing the air into the fan blades now you are talking less cooling effect on the condenser.
I've been exploring along the same lines with the exception of using one of those ventilating roof turbines. I suspect the efficiency is better as it took quite a bit of finger force to stop it! I'm wondering along the same lines as you though: Does it use more power by restricting air flow and/or reducing cooling efficiency of the air conditioner?
Perhaps a better way to make the whole process more efficient would be to use the heat coming off the condenser for heating your water instead of just heating your yard. That way you would put BOTH sides of the condensor to good use for the same energy expenditure since we use hot water as well as air and refrigerator cooling. It's not free energy, just better use of it. My guess is that if you use your air conditioning much it would eliminate your hot water bill during the hot time of the year.
spa31rky5 years ago
kevinkm775 years ago
and where would i get this said "stepper motor"?
broken scanners

broken printers

broken CNC mills(the big ones have bigger motors)

Broken plotters

Broken electronics that need accuracy
floppy drives

i got mine from a broken scanner
Tool Using Animal (author)  kevinkm775 years ago

electronics goldmine


all electronic

surplus shed

rpvanpatt5 years ago
 What about creating a normal wind turbine out of this design instead?  Would it be able to charge a decent size battery?  How much energy output is created with this plan?
buteman5 years ago
 This sounds very good but I am sorry to say it will not be saving anything. Your compressor will have to work harder, the turbine will  not be 100% efficient, and so you will be loosing power overall..

You would find it would use less energy to run your pool pump from the mains than doing it this way, sorry to say.
Transquesta7 years ago
IMO, this is an excellent Instructable, but the real beauty is in the IDEA of recovering otherwise wasted energy. I'd personally like to see a lot, LOT more of this kind of thing. To me, it's not enough just to think in terms of energy conservation, but also to think in terms of energy recovery as such might have a positive impact on the total "cost" of of energy.

I'll have some of my own ideas along this theme posted in the next day or so, but, in the interim, somebody's already ahead of us in a BIG way :-):

You're really not recovering anything - you're putting more load on the motor.... With the right equipment, you'd see the motor drawing more current to maintain a constant rpm (as per the motor design). This is why Tool explicitly called it "parasitic" ;) Overall, it'd be more efficient to either get the power from the wind (an actual wind turbine rather than parasitic) or power it directly from the wall (less energy conversions can yield much higher efficiency than parasitic loads) Waste heat (as per your link) is very different than this, just for the record ;)
See my comment below to Patrick. Otherwise, I don't see how what amounts to a windmill placed atop the outdoor/condensing unit would put an added load on the CFM (Condenser Fan Motor). ASSUMING you're right, though, that'd be easy enough to determine with any good ammeter. . . .NOW, how about a way to put that condenser heat to good use? ;-)

I would say that the heat rise would compensate for any resistance the generator fan is creating.  The little 1/2 horsepower fan motor on the AC unit is pulling cool air through the bottom coils which heat it up about 20 degrees above ambient air temps creating an updraft assist for the cooling fan.

It is simple, although not obvious/intuitive, physics... An action has an equal and opposite reaction (recalling newton's laws of linear motion). This isn't obvious nor intuitive as the forces are transmitted through the air (viscously) - effectively, viscously coupled.

Allow me to walk through a corollary scenario:

Imagine riding in a car with the windows down - then put your hand outside and feel for force pushed against it. It's very reasonable (and accurate) to say that the engine must push harder to overcome that extra force to maintain a constant velocity (perhaps difficult to measure - but we intuitively know we can't get something for nothing). Replace your hand with this turbine - it obviously takes some force to turn, you're generating power and thus work (force * distance) must be done. So we know the engine is working a little harder, and we're generating power... Now replace the engine with the motor, and we have the exact same scenario.

The issue is, thermodynamics tells us (by thermodynamic laws) that there's an efficiency loss every time energy is converted or transfered (remember, you can't create energy ;) ) - in this case, mechanical (air resistance) and electrical (internal resistance as a function of I2*R). Since all of that power was ultimately generated by the a/c motor, and the motor is designed to always spin at the same rpm (dependent on the number of poles inside), and voltage remains constant, the motor will pull more current as the load increases to maintain it's operating slip angle (the stator in a motor trails behind the frequency of mains power - 60Hz - more slip in this case means more current).

As far as putting the heat to good use - such devices actually exist - waste heat recovery units... They go on the refrigerant line just before the condenser and have a heat exchanger to go to a water heater tank... At least, a friend of mine has this - the power company used to give rebates for having one of these systems. Alas, with higher efficiency A/C units, the system isn't as effective... With a less efficient a/c system, the water heat might not turn on all day :) This isn't necessarily the case with newer a/c designs... At home, my family has a solar assist water heater - the heating element never turns on during the day :D

On the subject of waste heat recovery - large power generation turbines (likely like the ones at your nearest power plant) use recouperators to re-use some of the rejected heat (rejection is necessary for all power systems - back to those thermo laws :p). It's a very similar concept to what I described above for air conditioners ;) This is one method thermodynamisists use to increase the efficiency of large power generation operations :)
You're correct that there's always an efficiency loss, but the efficiency loss of the setup without the generator is 100%. Even if he only gets 1% efficiency from the generator on the airflow, that doesn't necessarily mean that he's increasing the load on the compressor to 100/99~1.010101... of the original load. How do you think a turbo charger on a car exhaust can increase both HP and gas mileage at the same time? The gains from harnessing the waste energy are greater than the added load on the pistons. A counter example is worth a thousand words...
back pressure on the engine creates turbo lag which takes away form the maximum efficiency of the engine. It takes a lot more force to get the turbine moving than once it's spinning already though. Also, you get the notion that you get high mpg but rather most cars that are turbo charged typically have smaller displacement in the cylinders therefore are more fuel efficient.
yetihair bwcbwc7 years ago
"How do you think a turbo charger on a car exhaust can increase both HP and gas mileage at the same time?"

It may increase HP but it certainly doesn't increase MPG, since the turbine spins up a compressor on the inlet side of the engine forcing more air into the engine. Since you now have more air in the cylinders per ignition cycle you now need more fuel to keep the fuel/air ratio correct. Meaning you use more fuel.

Here's a question tho, if the generator fan is far away from the condensor yet still generating something is it still placing a load on the condensor fan?
Here's a question tho, if the generator fan is far away from the condensor yet still generating something is it still placing a load on the condensor fan?

Doesn't matter, just read mowdish's comment, which explains what i mean better as well :)
How do you think a turbo charger on a car exhaust can increase both HP and gas mileage at the same time? The gains from harnessing the waste energy are greater than the added load on the pistons.

A turbine recovers HEAT - and there's a subsequent pressure differential. You can, in fact, calculate how much heat was used knowing a few fluid properties and the pressure differential between the high side inlet and the low side outlet (mind you, I said heat - not temperature). This is one of the most misunderstood concepts about turbines, in my opinion. I think that is because no one investigates the heat differences between the inlet and outlet for automotive turbines - because this isn't particularly useful for them.

Check out "Fundamentals of Thermodynamics" by Michael J Moran, Howard N Shapiro from your library - I, unfortunately, had to drop a couple hundred dollars to buy it, but I'll bet your library has it or something similar
Link to Buy so you can see the cover. While it won't directly explain automotive turbines, it does an excellent job and explaining recuperation and recovery systems etc., the efficiencies behind them, entropy etc. etc. etc. You too can join the club of people confused by the difference between entropy and enthalpy (I used to be the president of said club).

You're correct that there's always an efficiency loss, but the efficiency loss of the setup without the generator is 100%.
This is an intuitive approach to a problem that isn't intuitive. The efficiency loss is not 100% - that is just making useless heat. Work is being done - moving air (which is a rather intensive process). The energy balance will come from somewhere - if not from the fan motor, the loss of airflow due to obstruction will lower the heat rejection efficiency of the condenser - the compressor must stay on longer to cool your home, car, etc.

Perhaps I should do an instructable on an introductory to thermodynamics and how to solve some basic thermo problems :) That'd be fun for the math geek groups :)

There's no such thing as a free lunch ;)

A counter example is worth a thousand words...
Only if applicable ;)
On the general physics of the situation: A number of people have responded to this project by saying that you can't create energy. That is obviously true, but Tool isn't trying to create energy he's trying to convert energy. For the same reasons that we can reclaim/convert some energy from wasted heat, we can also reclaim/convert some energy from the wasted kinetic energy of the exhaust. Regarding back pressure: This is an open system in that the exhaust is being released into the open air. In an open system back pressure drops off with distance from the exhaust. What is more, the rate that back pressure drops off is higher than the rate that exhaust pressure drops. As a result, if you move the turbine far enough away, you can reclaim some of the energy. If I remember correctly the optimal distance is a function of the radius of the exhaust fan.
Tool Using Animal (author)  mowdish7 years ago
Thank you Mowdish, I've been giving this some thought. Here's how I analyze the system.

The compressor system: Elecin =KEOut

Turbine system KEin=Elecout,turbine+KElower,out

sum the two.

Here's my allegory, I go to the gun range, I shoot a machine gun down range at a target, someone puts a spinning target between me and the target, that doesn't make the gun shoot any harder, it makes the target spin and my bullets slow down.

I think the back pressure issue is the crux of the argument, there will be an increase in pressure in front of the turbine, but as you said, being an open system, how far does that bubble of high pressure extend? I would contend it doesn't extend as far as the compressor fan.

And yes there will be an expanding area of lower speed, higher pressure behind the turbine, but that is not relevant.
I think the back pressure issue is the crux of the argument, there will be an increase in pressure in front of the turbine, but as you said, being an open system, how far does that bubble of high pressure extend? I would contend it doesn't extend as far as the compressor fan.

If there's moving air, there's a pressure gradient. In order not to put additional load on the a/c fan, you must not interfere with that pressure gradient... Alas, without that pressure gradient - there's no airflow....
Put the fan perpendicular to the air flow of the compressor fan parallel to the wall of the house. Granted, the amount of wind captured would be significantly less than that of being mounted directly above the air flow. However, the house isn't going anywhere and any additional load on the compressor fan from the dreaded Back Pressure would microscopic. Changes in relative air pressure from passing clouds would have more of an affect. Conversely, the amount of energy reclaims would be radically reduced as well. Just a thought...
Tool Using Animal (author)  trebuchet037 years ago
There is a pressure gradient across the compressor fan, but once that column of air leaves the compressor, it should be at ambient pressure. My experiments have been inconclusive, I'll post the results tomorrow, after I try something.
Alright here's what I did experimentally, I call the results inconclusive because of the resolution of my meters. In the first experiment pictured below I modified a power strip to allow me to monitor current by cutting one of the bus bars between the first and second outlet, jumpering that with my meter allowed me to measure current. The fan was plugged in and allowed to reach steady state, the voltage was 122 volts the current draw was .58 amps, a paper plate was then placed in front of the fan to represent the load, the measurements remained unchanged. The second experiment an impeller, pictured below, was attached to a 380 size DC motor to represent the load, the fan above was replaced with a hair dryer, in steady state free air the dryer drew 2.27 amps, starting at an approx distance of 10 radii the impeller was introduced into the air stream and then slowly moved towards the dryer, between 10 and 1/4 radii there was no change in current draw, inside of 1/4 radius the draw dropped by .03 amps. The experiment was repeated with the impeller motor shorted to increase load, and with the impeller manually stalled, again the current draw profile was the same. Lastly experiment one was replicated with an open cage stand fan again with no change in current. Make of it what you will.
experiment 015.jpgexperiment 016.jpgexperiment 008a.jpg
Tool Using Animal (author)  trebuchet037 years ago
Hey T, been a while, if I have time, I'll do a little experiment with a small ducted desk fan I have. Measure current draw whilst obscuring various portions of the air flow from various distances. But your corollary scenario is imprecise since you have the hand and the engine mechanically coupled.
That would totally work - assuming the load is high enough for the kill-a-watt to pick up on :D The thin isn't the most accurate or precise, but it could work :) I imagine shaded pole motors would have the same results.... As far as coupling is concerned - force equations don't care how you're coupled ;) If the a/c fan blew out the side rather than the top - the fan would be mechanically coupled through the earth or platform the things are sitting on :)
Tool Using Animal (author)  trebuchet037 years ago
Yes I already ruled out the kill-a-watt, the fan only drew 30 watts, I'd have to cut the cord and use my multimeter.
However, there is no guarantee that the added load on the motor is as great as the energy recovered by the generator. If you connected the generator directly to the shaft of the compressor fan, then the added load would be greater than the "recovered" energy, but both values would be far greater than the energy transferred here. In this setup, the air acts as kind of a clutch between the compressor fan and the generator fan, so some of the torque is borne by the airflow itself rather than the compressor. This is similar to the action of the hydraulic fluid in a car when you let up slowly on the clutch pedal. The wheels use some additional power from the engine, but they also get some power that the engine normally wastes at idle.
It would be interesting to see the additional power drain caused by installing the turbine. If you were to hook it up to an alternator and the power generated there was greater than the power drain caused by the introduction of the turbine, you would have quite a valuable device on your hands. Finally something good would come from my girlfriend keeping the thermostat set at -4!
evank5 years ago
Two points: The reason there is a fan is to more quickly move heat in or out of the house. If you put the turbine anywhere, it doesn't matter if it's before or after the fan, it will slow the flow and create turbulence, and make this heat flow slower. Think of it like a line at an amusement park, with one entrance before the ride and one exit after the ride. Instead of air molecules, you have people, instead of a fan you have a ride. It doesn't matter if you restrict the flow of people coming into the entrance (before the fan) or moving out of the exit, either way you'll make the ride less efficient. If you don't allow people to leave the exit, they'll back up into the ride, and eventually the ride can't operate. It's called back pressure. In a fan, it's much more fluid, but the idea's the same. If you think the fan is moving too much air, and wasting electricity, you should check with an HVAC expert, but the easiest way to conserve energy in that case would be to replace the fan or its motor with a more efficient design, or set up some variable speed system. But I do think this is a brilliant way to test new turbine designs.
Carmelite evank5 years ago
 If you shoot a block of wood with a bullet and the bullet stops, does that affect the speed at which the bullet comes out of the gun?
(that was a rhetorical question)

The ride will always make move the same amount of people. It doesn't slow down if there's an increase in people after the ride is over.
evank Carmelite5 years ago
It's more like what would happen if you put a block of wood over the end of the barrel of the gun. It would slow the gasses from escaping (which always travel faster than the bullet), and lower the exit velocity of the bullet. If you put the block inside the barrel tight enough, then the gun doesn't work at all. We're talking about compressible gasses, not slugs of metal.

If the heat exchanger didn't need a big fan to work properly, they would have put a small fan on it. Swap out the fan if you think it will save you money, but a Rube Goldberg energy capture approach will always be less efficient.
fjpalacios15 years ago
instead of making a fan that catches the air from the AC fan, wouldn't it be more efficient if you some how connected the motor to the fan itself so the AC fan spun it directly?
No in that case energy spent would be air flow plus motor, energy recovered would be motor, it zeros out (it's actually WORSE than that when losses are taken into account)
Correct! The idea here is to recapture energy which would otherwise be wasted. If you came directly off the shaft of the condenser fan motor, you'd be using MORE energy over-all (to say nothing of overloading a perfectly good PSC motor).
Actually, the energy from the AC fan is not wasted - that fan is there to distribute the cold air throughout the room. By putting a wind turbine in the air flow, you're essentially reducing the effectiveness of the AC by a tiny amount (say, about enough to light a few LEDs).

It would be far more efficient to simply turn down the AC a little.
The fan which the author of the Instructable proposes to use is the *condenser* fan motor. Apart from removing heat from the condenser, the wind energy from the fan (as well as heat from the condenser) is wasted. Provided that the installation of what basically amounts to a windmill atop the outdoor unity doesn't put an additional load on the condenser fan motor (and I don't see how it could), then the attempt by the author to recover that wasted energy is valid.

Only thing is, I'd be figuring out a way to use the voltage he generates to charge a cell-phone battery or something a bit more useful than lighting a series of LED's. :-)

why not think of other applications like using the heat given off ac to heat water going to your water heater .that should warm the water and make the waterheater work less maybe saving some money in your utility bill. a round coil the size of the opening of the ac would not block airflow and as it passes out the coil the heat transfer to coil should warm the water a bit . in theory i guess let me know what you think
I agree. Looks to me like he is "claiming" the energy of the blown air. The only pressure he would be putting on the motor is if the pushed air back flows into the condenser fan. His fan is at an angle so back flow would be minimal at best.
bwcbwc ramedia7 years ago
Good point. The force vectors would direct the backflow away from the condensor blower. Flip side is that he doesn't recover as much energy from the airflow as he would if it was parallel and centered to the blower.
Tool Using Animal (author)  Patrik7 years ago
Patrik, that would be the blower fan, this is the condenser fan,it's purpose is to move air over the hot condenser coils and then blow it away, The only way my turbine could impact the performance would be to cause the air to stagnate around the condenser, however temp measurements around the condenser showed no deviation between with/without turbine.
I'd be interested to see the difference in amp draw readings from the CFM with the 'windmill' attached versus not. If you're curious enough to find out, you'll need a good clamp-on ammeter (Fluke--Home Despot--about a hundred bucks). You'll need to measure the current/amp draw from the motor's common (usually black) lead. Of course, any difference in load/amps at all and my recovery idea goes out the window. :-)
All you need to do really is work out the actual power in the circuit. Get two DVMs, and switch one to AC current, and wire it inline with the fuse and the AC. Turn it on and get a reading. The line voltage will be measured at the same time by the other DVM. (I suggest you check your DVM can take the fuse rated current before you start wiring it to anything!) Now for the bit that actually matters - wire the DVMs in the same way to the turbine, and determine the actual power from it. You see, the problem is that when the terminals are open, or are only shorted by a megaohm or 10 from a DVM set to read voltages, you get a thing where the voltage floats upwards. This is why it reads 50V in the article. Then you measure the amps, and that is a dead short, so you get more current but almost no voltage! It's the same effect, only backwards. To get an accurate result, you need to measure both the current and voltage outputs at the same time. You can then multiply them together to get a correct power rating. If it was, say, 1 watt (so putting out 0.1A at 10V) then you can simply plug the numbers in to the formula to find out roughly what is happening. The 50V measurement is outputting only 1/50 amps, which won't run much, and your dead short measuring 0.2A gives 1/0.2 amps, or about 5V. These figures give you a good idea of what you can run from your device.
Tool Using Animal (author)  Patrik7 years ago
PS that would be turn UP the ac a little ;-) but I have a wife, who like it cold, when she leaves for work I turn it up to 80.
austin Patrik7 years ago
the turbine in this is on the outside heat pump not the inside vents.
Tool Using Animal now thats what I call using you brain,and your right to use the escaping air to generate more energy than the AC unit draws. GREAT IDEA!!!!!
Yes, but the energy we recapture does not necessarily need to come from YOUR a/c unit! Maybe a gov building or an oil company office. The possibilities are endless! Hee Hee
ptacnik6 years ago
can this be made just by changing polarities of the motor in a Domestic/Industrial Fan ? HELP !! so i can use the blades and the housing for this project :)
Tool Using Animal (author)  ptacnik6 years ago
No, the form of motor used to power a fan from the mains AC is not conducive to use as a generator.
AJC8946 years ago
Good, A lot of people don't do this And great project.
Actually if oyur house is solar powered and your fans are solar pwoered you could use htis to charge other devices.
vtvtvt6 years ago
Unfortunately if we keep installing "free energy" devices like this, we will need a few more coal fired power plants to cover the energy wasted. The load on the A/C fan due to the "wind charger" is for sure more than you could ever capture due to losses of energy from air to mechanical, mechanical to electric and electric transmission.
rimar20006 years ago
Very good work. I agree with who said that this is more commensalism than parasitism. I do not think the big fan is affected by the addition of the small, except that this latter significantly obstruct the air flow. In the area where I live there is not enough wind, I will have to move ... These wind turbines always liked me. One small point: I think that efficiency would improve significantly if the propeller pointed straight to the source of wind and not give back as when the fan is supported on air conditioning.
lr10cent6 years ago
An even simpler way to do this, if you had an old muffin fan, would be to open it up and access the wires from the motor. Your bridge might be a bit more complicated, I think. Less current, of course. Hmm... I wonder if you could just hook up to the wires from the box fan and leave it in the box. Aren't those synchronous, and therefore brushless??
joeofloath6 years ago
I see one flaw in this plan... using the fan is making the compressor work harder, so drawing more electricity, and costing more. it's like putting a dynamo on the wheel of a bike, and using that power to drive a motor. the power from the motor is less than that used to turn the dynamo. 2nd law of thermodynamics I believe?
i think the fan is too far away to make any difference to the AC.
I think the point is to recover some, not all, of the electricity lost, so its a pretty clever idea for recycling the energy we waste in things like cooling our homes.
sircosmic7 years ago
this is an interesting idea...but picture this y'all!! instead of feeding off the power of the breeze generated by the fan,why not (assuming the AC unit is no longer under warranty) retrofit the motor INSIDE the AC unit with a belt drive to run a generator!!!since an AC unit is switched on pereiodically why not recoup some of the costs involved in running the unit (especially if the unit is old and probably getting increasingly more expensive to run)
you can never get more energy out of somthing than you put in so the motor from the fan put more energey into turning the gerenrator motor than the generator motor will produce into electricity
Wouldn't that just be putting more load on the fan motor, thus drawing more power than it otherwise would, or make the fan spin slower and cool (however small an amount) less efficiently?
Jouda Mann7 years ago
how about adding a shroud to the unit and put a turbine inside the shroud?
trebuchet037 years ago
Seems like a good electronic method to activate a solenoid to spray water on the condenser coils :D Unless it gets too windy and you get a false trigger..... Or maybe trigger a timer to see how long the condenser unit runs..... Or just how many times per day it turns on....
The water spray is a great idea. Since you are looking to use evaporative properties, it could be a mister if there is not a lot of wind. Since the heat of the day usually comes without much breeze this could be genius! I think I will try to do that for my next little side project. After all, if the condenser is more efficient it will have to run less duration and maybe less often. Maybe instead of mist it could have a drip system, these are already available for indoor plants and could be modified easily. Since the condenser doesnt move around that could still be an efficiency boost. Hmmm lots of ideas suddenly flowing..... I will have to think it all through for diminishing returns before buying parts or building of course. : )
Pretty clever idea. I noticed that the Condenser box is painted some mild colour similar to the wall of the house. Would it cool the condenser coils to paint the condenser box with very, very reflective paint? Would "she who must be obeyed" notice that silver box before the results are in?
You don't want to reflect heat away, you want to reject heat.... Black would be the best color to do this... Yes, black heats up faster (from radiation) - but it works both ways, it will also reject heat faster (through radiation). The trick is, the coils are aluminum, which is already a decent conductor - you'd need a surface coating that doesn't impede it's good thermal conductivity properties.... If you're worried about the box heating up from say, the sun.... Plant some greenery for shade - she who must be obeyed will probably like this much better :)
Tool Using Animal (author)  trebuchet037 years ago
Interestingly, a google shows the emissivity of Kyrlon Flat black and Flat white to be nearly identical. With the white slightly higher, but you can't believe everything you read on the net ;-) So, I'd say for the casing, any color is good as long as it's flat. Here's a crazy idea. Don't mess with the coils, paint the inside of the case black to absorb any radiant heat, paint the outside white to emit the ir and reject solar heating. Probably not worth the effort.
cheap experiment: get two black umbrellas paint one white on the outside paint one black on the outside (they each have black inside) blindfold someone and hand him an open umbrella will he detect a difference in the comfort level?
Probably on a very hot day the white umbrella assuming both paints were equally opaque would be cooler. Look up Kirschoff's law of thermodynamics: Heat absorption is equal to heat dissipation given the same material and same color. I might have misspelled Kirschoff but I think that's the proper spelling.
Tool Using Animal (author)  rcg407 years ago
Painting it white might help, silver is a bad idea because of low emissivity. Try this experiment, find a black car parked in the sun, touch the paint, hot right? Now touch some chrome on the car,carefully. And yes the wife would kill me.
Read my above comment: Just don't use an excess of water as it leads to alge and possibly mold/spore build-up.
I had a friend who fixed a water spray and got an alge build-up but he had it running full-time, or at least when the compressor was running; I don't remember the details.
Isn't it less Parasitism and more Commensalism?
I agree in full
richelton7 years ago
Regarding the concept of 'recovering lost work' perhaps this scenario might offer another way to consider who 'foots the bill':

What if one of your neighbors put a few of these little fans directly in the airflow paths of your AC compressor fan and that of your other neighbors--those being physically located on 'his property', say, in a 'zero-clearance' urban situation--and used that 'recovered' energy output to reduce or buffer his own energy costs, i.e. not that of the collective, just his own power bill.

Now, Would you say 'more power to him' (pun intended) or would you start to look more closely at how his actions affected your own energy costs? Apartment dwellers in a vertical configuaration effectively do this already, being insulated above and below as well as inheriting 'waste' heat from the unit below. That's implicit in the bargain when negotiating rent or mortgage for such an arrangement. However, the scenario described above would likely get ugly and involve lawyers examining covenants, property easements, 'airspace rights' and whatever else they could come up with as practical reasons why you are doing extra work to carry his parasitic energy 'recovery' scheme, and thus he is 'stealing' from you and should stop doing it.

The important take-home concept here IMHO is that what you might for convenience choose to think of as a closed energy system in fact is not and cannot be truly closed--and thus the resource inputs and entropic outputs of any such system are all interrelated. That insight is what got me interested in alternative energy sources a long, long time ago.

(Incidentally, this is one of the reasons I enjoy reading the Instructables site. I pick up on little comments back and forth that point out to me discrepancies between what I thought I knew and what I thought I didn't know. There are some really smart people here to whom one does not have such candid and ready access in normal workaday life. Thanks!)
Learndy7 years ago
Yes, stepper motors seem to be really popular poor-man's alternators. Has anybody tried some brushless model motor? The have a permanent magnet as rotor and several (usually 3) coils as stator. Kind of a 120° stepper motor...

Airspace V - international hangar flying!
http://www.airspace-v.com/ggadgets for tools & toys
sleeps7 years ago
The word, paracidic threw me off for a while, but good instructable!
chuckr447 years ago
I assume your stepper motor was a DC motor, right? Now what can I do with 2 AC motors from fans? Fan blades and motors and electronics are all fine, the cases are just smashed.
fishhead4557 years ago
FLATULATIONS HOMOHABILUS--I must now go make on e of these...thanks
What do turbines do? Like the Tesla Turbine thingy...
Tool Using Animal (author)  GorillazMiko7 years ago
They generate power GM, by conversion of the kinetic energy of wind into mechanical energy (the spinning blade) into electrical energy (the alternator).
So you could connect one to an LED or small motor, and it would power it?
Tool Using Animal (author)  GorillazMiko7 years ago
Or ten LEDs in this case. ;-)
That's so cool! I want to make one now. Way too hard though...
Tool Using Animal (author)  GorillazMiko7 years ago
Nothing is too hard if you are willing to risk failing.
Well, it looks like I failed.
Naw, you just discovered another way not to succeed - which is success in itself, frustating as it may be :P
Jackhole7 years ago
Very good, I thought this was a great Instructable, I've actually been looking around for information on building something like this. Where did you happen to get your motor?
Tool Using Animal (author)  Jackhole7 years ago
I bought it from a store called Skycraft, they have a website, but the motor is not listed. Similar motors can be found at other surplus electronics suppliers on the web. Also Ebay can have good deals, I juts bought a 6 phase 90 V 4.0 Amp motor for all of $20 inc. shipping off ebay.

The first one on the Alltronics site looks like a good one.
Yea, Skycraft is loaded with stepper moters and all sorts of electronics. I love that place! For those of you that don't live near one, their website is http://www.skycraftsurplus.com/
Another central Floridian :p
ryaninc7 years ago
I would also like to know where you got the motor. I think this is an awesome idea and I would love to try it...but I did a quick search and couldn't find a motor like that...especially not for only 4.95. :-)
Mikey D ryaninc7 years ago
I wonder if a stepper scavenged from a printer, like dbc1218 use in his http://www.instructables.com/id/Bike-Generator/ project, would work?
Tool Using Animal (author)  ryaninc7 years ago
This one looks good, and this one.
Mr. Rig It7 years ago
TUA, Very nicely done. At first I didn't get the "parasitic" idea, but then as I started reading I picked up on it. This is a great GREEN idea. Create a wind tunnel off the top of the AC unit and line it with a few of these. You cold be cranking out some serious voltage. Direct that back into battery storage etc etc... Good job with clear instructions.
Tool Using Animal (author)  Mr. Rig It7 years ago
Thank you sir, on two counts.
ry259207 years ago
Good Idea. Fav, 4.5 stars
Geordiepom7 years ago
We already harvest water from our air conditioner which we put on plants and give to the dogs for drinking water. This is another great way to to get something back from our power-hungry friend on the verandah. I'd like to store the power produced during the day and use it to light the footpath at night.