Thursday, 6 March 2008

Perpetual motion machine, anyone?

As Kermit said, it’s not easy being green.

I recently stumbled upon a bunch of excitingly clean green things, like claims you can run a car on water (a teensy bit of electricity separates out the water into hydrogen and oxygen and you burn the hydrogen) and magnetic power generators that apparently make electricity out of nothing.

Now, I have actually majored in physics, and while some people may regard violating the law of conservation of energy as a victimless crime, I have to say that if any of this stuff was remotely close to possible, everyone would be doing it.

Let’s take running a car on water. So maybe the oil companies would suppress such an invention. But the sites claiming it can be done also claim it’s really simple. So what’s to stop an insignificant poor country without oil developing this technology for their own use? Even if it’s too hard a job for a backyard tinkerer to convert their car engine, why isn’t everyone running their lawnmowers on water? Why are there no modern-day Albert Schweitzers in darkest Africa, running their clinics off water powered internal combustion engines?

Anyway this stuff has been thoroughly debunked many times so why bother? One of these things has turned up in my own back yard. There is a bunch calling themselves Lutec in Queensland, Australia who claim they can amplify electricity.

An amplifier, in the usual sense, has two inputs: the signal you want to amplify, and a power source that provides the amplification (which sets an upper bound on the output signal). Theirs is really special. The input signal amplifies itself. No kidding.

Their device involves a few steps including:

  1. run mains AC through a transformer to step down the voltage
  2. rectify to DC
  3. run the DC through a pulsed motor which drives an AC generator

This is not quite all but their big claim is that if they stick a DC voltmeter and ammeter on the DC side, and AC equivalents on the AC output, the volt x amp product (watts) is significantly higher on the AC side. They are amplifying electricity.

Or so they claim.

A moment’s thought should reveal how absurd this is. If they fed the output back to the input, you would get a positive feedback loop. The output would increase indefinitely until something blew – even if you disconnected the mains input.

There are two reasonable possibilities. These people don’t understand what they are doing and are not measuring what they think they are measuring, or they are frauds.

How could they be getting the results they claim? If they are frauds, it’s easy: they could have another power source hidden somewhere – or they rigged the meters. If not, how could they be getting such a big instrument error? The trick is to understand how AC voltage and current are measured. Since AC is constantly fluctuating between a positive and equally low negative value, you need to take an average to get a voltage number that equates to DC voltage (or amperage). The standard formula for this is the root mean square (well explained on WikiPedia so I won’t repeat the explanation here).

The problem with taking the root mean square is that if you are designing a voltmeter, it would be hard to calculate the RMS voltage correctly, so my understanding is that most voltmeters fake it by assuming the AC is in the form of a sine wave, and calculate the RMS voltage as peak voltage / square root of 2. If the wave is different shape, the voltmeter will give an incorrect result. If your AC voltage is nominally 240 as in Australia, the actual peak voltage would be about 339, as illustrated in the first picture.

The second picture shows a different wave form in which the peak is still 339V, but the RMS is now 200V.
So if you had a machine that was producing this sort of output, your voltmeter would be registering 20% more than it should.

You can play around with wave forms to adjust the inaccuracy even further. I chose this particular one because it wasn’t terribly hard to construct out of sines and cosines.

I’m not an expert on AC and measurement techniques but this is a plausible indication of where the problem may lie – that’s if they aren’t straight-out charlatans, with a compact battery secreted somewhere to boost the output, hidden wires back to mains, or deliberately inaccurate meters.

As I said at the start – it would be great if these things were for real. If you want to be green, you can’t be gullible, that’s for sure. Poor old Kermit.

For those who want to check my working, here it is. I graphed the equations using the free Grapher program that ships with Mac OS X. Yet another reason to buy a Mac. PS: I checked the details with several engineers who are more familiar with AC measurement than I, and they agreed that this is a plausible explanation. You need to shape the wave so that it’s far enough off a sine shape to fool the voltmeter, but still register the peaks.

Here's another view on Pure Energy Systems Wiki.
The Australian Skeptics' journal has published a debunking of the Lutec device in two parts (part 1; part 2).

Lutec were claiming they had a machine ready to sell at least as far back as 2002. So where is it?

And if you are keen on powering your car with water, read this contribution at the good old Mythbusters site. Let me know which parts are wrong. Science please, not conspiracy theories.

1 comment:

Jimmi said...

Good job.... hopefully you save some fool some money on this and similar scams