Science Buddies: "Ask an Expert"

Hello,

I started experimenting on a project in which I find out what effect salt has on the power output of a microbial fuel cell. The title of the project on your site is "Turn Mud into Energy with a Microbial Fuel Cell — and a Dash of Salt[/color]". I a followed every single instruction for the procedure. My light has been blinking meaning my cell is producing electricity but whenever I measure the power out put with my multimeter the screen reads 000 no mater what resistor I use except for the 47 which is the lowest and it reads five. I put the multimeter to 2000m I have the wires in the right place and everything is right I am on my third day of trial and I am getting nervous. Does anyone have any idea what it is I am doing wrong? or any advice as to what to do? I am on winter break so my teachar can not help me my project is due on the 27 of January and I am already behind on my timeline for experimentation.!!!!

Hi,

Sorry you are having a problem with the fuel cell. Let’s see if we can figure out what’s wrong. You said you followed all the instructions to the letter and your LED was flashing so you were generating power. How many seconds between flashes? The more frequent the flashes, the more power that is being generated.

So, you tried all the resistors and only the 47 ohm one gave you a reading. Was that 5 mV? I calculated the power output for 5 mV and I got 1 microwatt (uW) which is pretty small but not unreasonable for the lowest resistance. Note that in the instructions it says to convert W to uW you divide by 1,000,000. This is incorrect. There are 1 million uW per W, so to convert W to uW you MULTIPLY by 1,000,000.

I don’t know why you did not get any voltage output for the other resistors. It is possible that the meter is faulty. If you could borrow another meter that reads in millivolts I would try that. Or you could take your meter to Radio Shack and ask them if they could test the voltmeter part of it with a source of known millivolts over the range from 5 to 500 mV.

I would also try adding some salt to the mud and see if you can get some voltage readings with the higher resistors. Adding salt is supposed to boost the voltage so maybe this will help.

Hopefully some of the other experts can give their suggestions as to what the problem might be.

Good luck and keep us posted.

Sybee

Thx for helping Scib I am going to go to RadioShack tomorrow so that it can be tested. I already added salt to it yesterday wich was when I got those results but to my multimeter just read 0. Thank you for letting me know about the mistake found in the post.

Yeasterday it was flashing once evry five seconds on average which was the first 24 hours.
Today it flashed twice every second after I had added salt the previous day.

Wow! It sounds like your MFC is crankin' out the volts. There has to be something wrong with the meter. Let us know when your problem is solved and you are back to getting good readings.

Good luck!

Sybee