Scientists Powering Batteries with Soda, Tree Sap

BobB writes "St. Louis University researchers have concocted batteries fueled by almost any kind of sugar, from tree sap to flat soda, and that could be used to power everything from computers to cell phones. Their thinking: If sugar can jack up the human body, why not electronics?"

Re:Stupid.

[OSU ChemE]

Since TFA was a bit light on the technical side (and I couldn't find anything on the ACS site yet) I'm just going to SWAG a few reasons:

• The enzymes available (or that they developed) only work on sugar molecules; not to say they couldn't develop enzymes that work on fat
• Sugar is water soluable and water can be made relatively conductive; fat, not so much on either count
• Fat is has more energy/gram but fewer grams/volume, though 9:4 energy and 0.8/1.2 specific gravity means it's probably not an issue
• More plants produce sugar than produce fat, and sugar is generally easier to extract from said plants than fat (even setting aside corn syrup)

Re:2.59/battery, anyone?

[DeePCedure]

Judging from TFA, I don't think charge times will be a huge issue. Just empty the battery's resevoir, refill it with fresh sugary goodnes and enzymes, then drive away. The spent fuel is biodegradeable so you can dump it in the sewer. Refueling would probably end up being infrastructurally similar to current oil-based fuel distribution in order to ensure reliable deliverey and the proper sugar/enzyme mix.

Even if the enzyme reaction takes a little time to get going and build up a proper charge, having multiple batteries running in an asynchronous parallel setup instead of serially should keep people moving. When battery A dies, the car switches to battery B and the "low fuel" light comes on. If you refuel battery A before battery B dies, you never have to worry about waiting for the chemical reaction to ramp up. And that doesn't even account for the possibility of "jump-start" catalysts that could accelerate the chemical reaction through the ramp-up phase before returning to it's normal electron producing rate.

However, nothing significant was mentioned in TFA about energy density, so that's still a concern.

Isn't this a fuel cell, not a battery?

[Radon360]

It seems to me that technology functions by putting a chemical (sugar) into the cell, and it produces electricity by breaking down the sugar. It isn't a directly reciprocating process like a lead-acid battery (i.e. you put electrical power back into it and it produces sugar). Its operation would seem to be more akin to that of a fuel cell than a battery, would it not?

Re:What's the energy density of sugar?

[Radon360]

Sucrose (not glucose or fructose), as a pure carbohydrate, has an energy content of 4 kilocalories per gram (or 17 kilojoules per gram)[Wikipedia]. 1 gram of hydrogen has about 140kJ of energy.

Whether, in fact, this is a fair comparison depends largely on the efficiencies of the devices extracting this energy, as well as the amount of energy put into producing each of the chemical products for consumption. While hydrogen is more energy dense, can we produce it more efficiently than refining sugar from plant sources?

Using electrolysis to produce hydrogen would require more energy than 140kJ/g, making it energy negative. Refining the sugar from plant sources would likely be somewhat energy positive. However, most hydrogen gas produced today is steam reformed from natural gas. I'm not certain where that would fall out if the natural gas were derived from biomass, instead of underground petroleum-related sources.

Re:What's the energy density of sugar?

[ThosLives]

Refining the sugar from plant sources would likely be somewhat energy positive.

Only if you don't apply correct accounting. Total energy yield from photosynthetic organic material is always going to be less than (absorbed solar energy + energy to refine).

Or, if you use the flawed methodology, using pure solar + wind + geothermal to electrolyze water means hydrogen is 100% positive gain.

I think the flawed thinking comes from the fact that with things like oil, (energy to refine) is far less than (energy available), but that doesn't take into account whatever energy went into creating the oil in the first place.

Re:Obvious:

[MrCopilot]

So can we build a battery out of fat and give it caffeine to stimulate energy output? That would make for one disgusting battery. But we'd have a virtually unlimited natural resource!

We have already have this for transportation, it is called a Bicycle.