Comments on: Parasitic power devices

By: Dave

Dave — Wed, 30 Jul 2008 00:26:52 +0000

I think it’s interesting you can take parts from an old box fan or oscillating fan to make a turbine.
I was wondering, won’t a reverse phase turn a normal electric motor into a generator?

By: Tool Using Animalt

Tool Using Animalt — Wed, 04 Jun 2008 18:54:45 +0000

Hi everyone, I’m the author of that instructable, I wanted to correct one important thing in the summery, the turbine uses a 2phase 6volt 0.4 amp stepper, the larger one is for an, as yet, unrealized project.

As to whether it increases the load on the compressor, that is still up for debate. My experiment have been inconclusive due to limitations of the test equipment available.

By: Alek

Alek — Wed, 04 Jun 2008 02:14:56 +0000

and wouldn’t putting this fan near the exhaust accomplish the same thing? if your concern is restricting airflow to your ac, then just put it where the air leaves. hell, put it in front of the vent; that will also help circulate the air, cooling the house faster

By: JaimE

JaimE — Tue, 03 Jun 2008 23:28:31 +0000

Parasitic sound bad.. Symbiote is better.

By: andy

andy — Tue, 03 Jun 2008 05:39:05 +0000

In think calling this device “parasitic” is fitting in a context where the “host” is somebody ELSE’s A/C unit. I would also say that this is probably the most interesting application… in which case it wouldn’t matter whether or not it makes the A/C Unit less efficient, as the user wouldn’t be paying the electricity bills.

By: joe

joe — Tue, 03 Jun 2008 04:16:54 +0000

to Justin Reed and others who asked why up to approximately 20% of the air's kinetic energy can be recovered.

A wind turbine is, in theory, 59.6% efficient, a 3 bladed wind turbine gets about half of that 59.6%. The alternator is 80% efficient, and a box fan is around 10% efficient or less, working backwards.

if you put a flat disk, the size of the fan, about 1 fan diameter, above the fan outlet, did the back pressure increase? no, not significantly.

The fan in question is recovering kinetic energy if it is far enough away from the fan, if it is too close, then the air is forced to go through the turbine, and it will recover a lot more.

a 1 meter diameter fan blowing air at 5 meter's second requires a [3.9 cubic meter/s x 1.19KG X (5m/s)^2] 233 watt motor.
If we increase the speed to 10m/s we need 8 times the power, but we only get twice the cooling rate.
that is why i suggested a larger condenser and a slower fan.

A good question to ask is: is the air pressure in front of a wind turbine higher than the air pressure a hundred feet up stream?
you will learn a lot if you try to answer that.

By: alfiesauce

alfiesauce — Tue, 03 Jun 2008 02:47:06 +0000

I was kinda mystified by the humidifying the area that requires a dehumidifier as well…
But what I really want to know is -
What the heck is a Twin Screw Expander?

By: Christopher

Christopher — Mon, 02 Jun 2008 22:02:35 +0000

Just spitballing here, but couldn’t the vent fan housing be enlarged some and have the fan increased in size/changed to accomodate the wind turbine? Place the turbine in-line with the current fan axle and have 100% of the fan’s rotation generating energy?

If the fan is creating windflow that is turning another fan, couldn’t a middle step be cut out?

And….if that step could be cut out, then we would have electricity turning the fan turning the turbine creating electricity, so we’d be better off redesigning the fan even more so it required less energy to operate in the first place? I’m thinking it would be more efficient to be more efficient in the first place, rather than trying to “win back” energy already expended.

By: Julie

Julie — Mon, 02 Jun 2008 20:39:10 +0000

This ElectraTherm device truly doesn't expend any energy. It doesn't use a turbine, it uses a patented twin screw expander. That is what makes it cool - fuel free, emmission free power.

Full release explains it better - http://www.electratherm.com/graphics/pdfs/FirstCommercialUnit.pdf

By: jstorm

jstorm — Mon, 02 Jun 2008 20:17:39 +0000

***(10)*** i use the heat from my dryer exhaust (only when i am drying clothes) in the winter to help keep the basement warm. only side effect is a little humidity. there is a dehumidifier running anyways in the basement.

Isn’t this defeating the purpose of regaining lost power by running the hunidifier to reduce the humidity? Does that not use more power?

By: vsnine

vsnine — Mon, 02 Jun 2008 16:49:11 +0000

Can anyone with a Kill-a-Watt or other device back up this discussion, please?

By: cde

cde — Mon, 02 Jun 2008 14:29:16 +0000

@Chronic: A parasite by definition is bad. You mean a symbiote (which all parasite are but not all symbiotes are parasite).

http://en.wikipedia.org/wiki/symbiont

By: jim

jim — Mon, 02 Jun 2008 13:04:57 +0000

seems more than a little futile to run a multi-kw ac and then try and claw back a watt or two by impeding its airflow. perhaps servicing it or just turning it down would be a better solution?

By: Andrew

Andrew — Mon, 02 Jun 2008 12:01:32 +0000

Has anyone posted anything on using power that comes into the home from telephone or cable lines?

By: Justin Reed

Justin Reed — Mon, 02 Jun 2008 08:02:44 +0000

Joe – how do you figure the first part of your comment? It sounds like you know what you’re talking about but I don’t follow. By placing a wind turbine in front of the fan, you’re decreasing the pressure difference across the fan, which decreases the fan’s airflow and thus reduces the heat transfered by the heat exchanger. Then the controller has to increase the fan speed to compensate, thus drawing more power and decreasing efficiency. Would you mind going into more detail of where the 20% number comes from? I’m curious. Thx.