I am a little confused. According to reasonable sources 1cm2 of fuel cell gives 0.5 watt at 0.6v. So trying to do a comparison with the needed power I did the old Watts Volts x Amps bit to try and get the right figure. But, according to that, the fuel cell cm2 is 0.3 amps and the power I need (15w at 30kv) is only 0.0005 amps. Now, I know fuel cells are efficient, but that does seem very far off reality. Does anyone know what the right figure would be for the fuel cell area?
First voltage: If the cell only gives 0.6 V, you will need 30,000/0.6 50,000 cells to make the 30,000 Volt battery. If each sq cm of cell gives 0.3 A, then you need 0.0005 * 0.3 cm in each cell. 50,000 (0.3 * 0.0005) 7.5 sq cm total, divided among the 50,000 cells in the battery. Reliability: Since failure (open circuit) of any one of the 50,000 cells could mean failure of the battery, you might prefer to use only a few cells, with electronics to get the voltage you want. If could mean losing some efficiency, but it might be easier to find and repair any failures, and the lower voltages would be safer to work with.
You have an unusual application needing only 15 watts. A tesla coil design likely needs a minimum of about 6 volts dc, so you need 10 fuel cells in series instead of 50,000. Likely you need about 60 watts, as the tesla coil is only about 25% efficient. Another type (more efficient and lighter weight) of 6 vdc to 30,000 vdc converter is likely available, but very expensive. Perhaps you can build your own, if you can add one or two turns to a transformer designed for dental Xray machines, or a flyback transformer for an obsolete CRT color TV.You will need a voltage doubler circuit as the fly back transformers were not designed for much more than 20,000 volts ac peak voltage. Two lithium ion rechargeable cells (7 volts), will be lighter than the fuel cells, if you only need the 30,000 volts for a few minutes, between recharge. Neil
This is the wrong way to approach it, you will never be able to build 50000 tiny fuel cells to add up to 30 kV Build a 30 watt fuel cell with 20 plates to give you 12 volts at 6 amps. Run that into an inverter with an output of 30 kV AC and rectify that to about 30 kV DC. .
