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.
But, It is a ponderable notion. And you could reverse the rotor, add a tail and yaw bearing and make a regular wind turbine.
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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.
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.
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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.
I have some steppers laying-around, and your 'ible has got me thinkin'!!!
TANSTAAFL
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
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".
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!
'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.
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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.
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.
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.
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.
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.
broken printers
broken CNC mills(the big ones have bigger motors)
Broken plotters
Broken electronics that need accuracy
Cd-roms
floppy drives
others
i got mine from a broken scanner
electronics goldmine
alltronics
all electronic
surplus shed
fjpalacios1
You would find it would use less energy to run your pool pump from the mains than doing it this way, sorry to say.
(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.
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.
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.
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!)
The first one on the Alltronics site looks like a good one.
virtuPIC
--
Airspace V - international hangar flying!
http://www.airspace-v.com/ggadgets for tools & toys
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 :-):
http://tinyurl.com/58fopn
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.
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 :)
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?
Doesn't matter, just read mowdish's comment, which explains what i mean better as well :)
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 ;)
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.
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....
It would be far more efficient to simply turn down the AC a little.
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. :-)