It can work, although the lifetime of the SOFC is an open question.
On the other hand a battery pack will have about the same energy density.
Marco nailed it.
(I use capital L for liter so it doesn't look like a number 1)
hobbyking ANR26650 A123 2500mAh
3.3V / 2.5Ah / 8.25 Wh
weight 70g
dimensions 66.5mm x 26mm
Specific Energy = 8.25 Wh / 70g = 0.118 Wh/g = 0.118 Wh/g * 3600 J/Wh =
424 J/gEnergy DensityJoules = 8.25 Wh * 3600 J/Wh = 29700 J
volume = ¼*
pi*
d2*
length= (0.25) * 3.1415 * (26mm)
2 * 66.5 mm = 35306 mm
3 = 0.035306 Liters
= 29700 J / 0.035306 Liters = 841217 J/L =
0.84 MJ/LKraftwerk56Wh
weight 200g
dimensions 3.95 x 2.95 x 1.18 INCHES!! (WTF? mixing metric and imperial)
Specific Energy = 56 Wh / 200g = 0.28 Wh/g = 0.28 Wh/g * 3600 J/Wh =
1008 J/g Energy DensityJoules = 56Wh * 3600 J/Wh = 210600 J
volume = 3.95 x 2.95 x 1.18 = 13.75 Cubic Inches = 13.75 in
3 * 0.016387064 L / in
3 = 0.225 Liters
= 210600 J / 0.225 L = 936000 J/L =
0.936 MJ/L SummaryThe Specific Energy (energy per unit mass) of the KraftWerk is more than twice that of a typical LiFePo battery, but the Energy Density (energy per unit volume) is only slightly better than the battery.
So it's about the same physical size of a battery pack that can deliver the same energy, but it can do that at only half the weight of the battery pack.
You would need 6-7 batteries to get the same volume of the Kraftwerk, and they are $12.80 from HobbyKing, so it's about $90. The lowest price on the Kickstarter page is $99. So price is good, and half the weight, same energy density.
It would seem that the only real benefit here is the weight. It's not bad if you need or want the lower weight.
I didn't calculate the recharge costs. Maybe someone else wants to tackle that
However, a 3 second recharge time beats the battery too.
And there's also other considerations, such as lifetime as Marco already pointed out.
Batteries fade too. Is it better or worse than a battery?
One huge advantage of the Kraftwerk is the portable power aspect. You can carry the Kraftwerk and a butane cylinder and get several recharges out of it no matter where you are. That alone is what's going to make it worthwhile for anyone who finds themselves away from the power grid often enough.