I am not sure this design would work. Look at the flux from primary, the other secondary sees flux from primary and opposing flux from other secondary, they dont add up. Here is a 2d picture of what I mean.

I see now. These are the closests matching cores then:

2x Oval: M-284  >60000µ @ 50Hz 100 EUR

Toroid: M-028 ~30000µ @ 10kHz 100 EUR (25mm thick)
Toroid: M-115 ~30000µ @ 10kHz 120 EUR (30mm thick)
Toroid: M-615 >45000µ @ 10kHz 100 EUR (30mm thick)

So depending on which toroid you chose the price will be around 300 EUR (without shipping costs). It's not that much but you have to ask yourself what the COP will be and how much power you can take from these.

Perhaps this version would be cheaper and more efficient?

On the first page of this thread wojwrobel had a similar setup, but there's no experimental data of his setup.

It would cost around 404€ apperently if you include 19% taxes, shipping seems costless in europe. If more people can pitch in I'm willing to donate 100€ for the project.

Hello everyone, I post my old version ("Reacto-Converter" for Reactive Energy Converter) that I have thinked one year ago but never released, it consist of three identicals toroids (Nanoperm) with one input and two output, detail and operation in pics below:

I think your flux distribution is correct if you don't saturate the two bottom toroid, but remember I heavily saturate the two bottom and by this fact reducing the permeability substantially, is here the Heins effect enter in action, when you put load equally distributed in the two secondaries, the flux will feed each other without consumming real power in the coil 1, if you load more and more the Back flux will start again to draw power in coil 1, so you have a sweet point...
In short by magnetic saturation I droop permeability and force the two secondaries work TOGETHER instead FIGHTING the primary...
Here I'm in vacation but in September I will test my version and yours of course !!!
Sorry I have not made this precision in my previous post...
And try this experiment, it's not FE but worth to try: Take a magnetic core (or any normal trafo) and wind two bobbin, but saturate moderately to draw some amp, try with 1/1 ratio, load the secondary and put a light bulb in series with the primary, when you load the secondary you should observe amps decreasing, but if you load more the amps restart to increase !!!

ok, now I see your point. But wont it take power to saturate the bottom cores in the first place ? Or is this the power that gets returned back ? Well, I don't understand this energy returning back at all, where does it return to ? Does the companys meter measure difference it sees between L and N/ground lines ?

No, when you saturate an inductor it draw reactive power, due to the phase difference of 90° between voltage and current, the current wave form is like in pics in previous post...

The company only measure active power (watts) the real energy, but not reactive (VARS).

In my simplified BTT version I do not saturate the primary core, unless the high number of turns does it somehow. The audio effect I observe is that without load there is some noise and faint light in primary side. When adding load the noise goes down, primary light is dimmed and light in secondary side lights up much brighter that light on primary side. If core is saturated, shouldn't there be lots of noise then ?

In my opinion your primary is slightly saturated: A saturated core make more noise than normal, and the small current in the light in primary prove that some reactive current flow in it !!!
When you load the secondary, the input current goes down and light go off and the trafo become unsaturated then make less noise !!!

So in short: 1° A saturated core make more noise.
                 2° A saturated core draw more (reactive) current.
                 3° When you load a saturated core the input current goes down.
                 4° When you load a saturated core the noise decrease !!!
                 5° When you load a saturated core at certain point it become unsaturated and run   
                     like a normal trafo except providing real power in secondaries !!!   
                 

Look at this:

http://www.youtube.com/watch?v=qPo5Ch14jlc&feature=channel_video_title

Ugly sine wave input current (in yellow) inside...

If my memory is correct, in this Topic even Thane (Cranky Pant's) speak about some saturation to produce the effect...

In the video he affirm he must increase voltage then increase current then ugly sine wave (saturation) then third harmonic then more reactive power then two secondary forced to work together instead fighting primary...

But I can have wrong of course !!!

OK, saturation is not the only criteria but I think is necessary to increase power on load with no Back Flux...

In this video again at 2:30 an ugly sine wave again:
http://www.youtube.com/watch?v=Eiu-dCe8bnA&feature=channel_video_title

In a BH curve when you saturate a core it's permeability droop, so if have primary leg with low u and the outer leg not or less saturated why you think the Heins effect should be not here !?