Interesting, can you provide the exact formula, and what are the absolute dielectric constant and the breakdown voltage strength (max V/m) for barium titanate?
Indeed atmospheric ingress can be an important factor, since the material seems to be a porous ceramic. The size of the pores, and the nature of the gas filling the pores could well be what determines the max V/m! Michel ----- Original Message ----- From: "Robin van Spaandonk" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Saturday, January 27, 2007 11:35 PM Subject: Re: [Vo]: More on the Bettery > In reply to Michel Jullian's message of Sat, 27 Jan 2007 14:11:55 +0100: > Hi, > [snip] >>Unless the coatings diminish the material's permeability to some atmospheric >>gases lowering it's breakdown voltage? >> >>Michel > > I would think that insulation from the atmosphere would be more cheaply and > easily obtained with a plastic sealant. > BTW there is no real reason to operate at such high voltages. By making the > dielectric material in the capacitor thinner, the capacitance per unit area is > increased, and also the total number of plates in a given volume can be > increased. Both of these together compensate for the drop in voltage, so in > fact > any desired operating voltage can be accommodated. It turns out that the > maximum > *energy density* of the device (J/m^3) is purely a function of the material > used > as dielectric in the capacitor, and is proportional to the product of the > absolute dielectric constant of the material and the square of breakdown > voltage > strength of the material (V/m)^2. > >> >>----- Original Message ----- >>From: "Robin van Spaandonk" <[EMAIL PROTECTED]> >>To: <vortex-l@eskimo.com> >>Sent: Tuesday, January 23, 2007 10:50 PM >>Subject: Re: [Vo]: More on the Bettery >> >> > [snip] >>> The EEStor patent is US7033406 which I believe contains a design flaw. >>> They state that the base material (Barium Titanate) is coated with Aluminum >>> Oxide and Calcium Magnesium Aluminosilicate, which coatings are intended to >>> increase the breakdown voltage of the composite. They then go on to >>> calculate >>> the energy density based upon this increased breakdown voltage. >>> >>> However IMO, what happens in reality is that a high voltage drop will occur >>> across the high breakdown voltage component, and a lesser voltage drop >>> across >>> the Barium Titanate. IOW with such a composite construction, one can't >>> simply >>> apply the full voltage to the entire material for the purposes of >>> calculating >>> the energy density of the whole. The real energy density of any given >>> material >>> is actually a constant, and no "trick" of design is going to get around >>> that. >>> Since they specify that the breakdown voltage of Barium Titanate itself is >>> only >>> 60% of that of the other materials, and since voltage appears squared in the >>> formula, the real energy density of the finished product is IMO going to be >>> nearer 60%^2 = 36% of their claimed energy density, which would be about 3 >>> times >>> the energy density of lead-acid batteries. >>> >>> Regards, >>> >>> Robin van Spaandonk > Regards, > > Robin van Spaandonk > > http://users.bigpond.net.au/rvanspaa/ > > Competition provides the motivation, > Cooperation provides the means. >
