Sweet work, fellas: Boffins build high-density battery powered by sugar Scientists at Virginia Tech have come up with a new battery that uses one of nature's most common forms of energy storage – sugar. sugar battery American innovation in action "Sugar is a perfect energy storage compound in nature. So it's only logical that we try to harness this natural power in an environmentally friendly …
0.8mW per cm², a maximum current density of 6mA per cm² and an energy-storage density of 596Ah per kg.
To put this into perspective… I have some 12V (so 6 cell) sealed lead-acid batteries about the size of house bricks weighing in at around 1.5kg. 9Ah capacity, which equates to 6Ah/kg.
We don't know what the mass per cm² is for these new cells, but 596Ah/kg looks quite good.
Actually no, that calculates as 130mV per cell, if the cell is 1cm² in area. We don't know how big they're making their cells and what the mass of the cells are.
I'd agree with you on the J/kg measurement, but I'm just working with what's mentioned here as I don't have access to the full document or the remaining information. There are factors we don't know, so it's not an apples-to-apples comparison.
"The only waste products are hydrogen and water, ...."
The hydrogen could be fed into a hydrogen fuel cell I suppose. What happens to all the carbon in the maltodextrin? The linked reference mentions the 'complete oxidation of maltodextrin', hence some carbon dioxide would be formed.
How much energy would be expended in the extraction, isolation and delivery of the maltodextrin feedstock and the preparation of the catalysts? What would be the financial and energy costs of maintaining the battery? etc ....
The carbon originally came out of CO2 in the atmosphere, when the sugar beet plants were growing. You are only putting back something that was already there before. This is not at all the same as burning carbon that, as part of coal or oil, has been kept out of the cycle for millennia.
Assuming the sugar is of biological origin, it was made in a plant by photosynthesis using atmospheric CO2. So it's a closed loop (assuming the plant is regrown ... a fair assumption for agriculture).
There is a carbon cost, in that agriculture uses fossil fuels for powering machinery and for making Nitrogenous fertilizer.
You're thinking of fats, which do burn well in air (hence "spontaneous" human combustion and that UK local news favourite, the chip pan fire). Sugars tend to melt and carbonise (turn to caramel) and go out. But chemically, sugars are easier to degrade in solution using enzymes.
I want to know if it's more efficient than feeding the maltodextrin to rats and making them run treadmills.
Sugars are quite flammable. In 2008, a sugar plant in Georgia (state) suffered a catastrophic dust explosion that was caused by ignition of the sugar dust in the air. 14 people were killed and 40 injured; the fire burned at around 4,000F (compared to the usual 1,000F to 1,800F a typical building fire sits at).
Maltodextrin is different than surcose (refined sugar), but they both carry the same dust explosion issue. In a battery, where is is unlikely to be in a dust-like state, it won't be explosive and flammability might be limited, especially if in an aqueous solution. Nevertheless, sugars can burn, and burn hot.
Sugars are quite flammable. In 2008, a sugar plant in Georgia (state) suffered a catastrophic dust explosion that was caused by ignition of the sugar dust in the air.
That's stretching the definition of "flammable" in this context past the breaking point. Since, as you note, the batteries are not large spaces with sugar dust drifting about in air, the sugar-plant explosion is in no way comparable. Neither will these batteries regularly be used in, say, an atmosphere of pure oxygen. Flammability is not an absolute attribute; it indicates relative risk of combustion in normal use and plausible failure modes.
Grain elevator explosions are hardly uncommon, but we don't go around complaining that corn is flammable. Steel wool burns nicely in our atmosphere (at normal conditions), but that doesn't lead us to blithely label steel as "flammable".
Since the maltodextrin will be in solution then you will first need to dry it before you wish to ignite it.
As a biologist the man problem I can see will be keeping the unit sterile. The environment is full of bacteria, fungi and assorted protists who will happily chow down on maltodextrin. Since the cells would have to be refillable since they are not electrically rechargeable (yet) then that provides an ideal route for infection.
Being unable to use your battery because something ate the charge is going to be a problem. I also wonder what the range of operating temperatures that enzyme has.
Energy density is measured in Wh/kg.
Proclaiming an energy-storage density of 596 Ah kg−1 is meaningless, because the voltage is missing.
I could claim that our drive battery has an energy density of 10000 Ah/kg simply by lowering the output voltage sufficiently (using a DC/DC converter).
Also, seeing that this is a fuel-cell, not a battery: What does the mass data relate to?
Mass of fuel cell alone? -Then they should compare to other fuel cells, not to Li-Ion.
Mass of fuel cell and fuel? -Then it is easy to fake good results by combining an oversize large fuel tank with a minuscule fuel cell. .. Which, when taken to the extreme, equates to the energy density of the fuel alone.
-Which is also quite misleading. We fly some 500 km on 5 kg of hydrogen. Sounds nice?
Wait until we have added the weight of the fuel cells, the peripheral systems and the pressure vessels.
El Reg is not at fault here though. Whoever wrote that press release either was being willfully misleading or ignorant of the matter at hand.
Thank you..
I looked at the article, but did not see the table.
596 Ah kg−1 at 0.5V yields 298 Wh/kg, which fits to 15% maltodextrin (24 e) found in "Supplementary Table S3 Comparison of energy densities of batteries and EFCs". If I read the table correctly, then this means that the 298 Wh/kg relates to the fuel mixture, not to the complete system.
For comparison
Li. Ion: 180 Wh/kg is a reasonable value for a cell with good power and lifetime values. I know of alternative chemistries that have achieved 300 Wh/kg in lab conditions.
Although I would be happy to see a good and lightweight fuel cell that can use this fuel, I fear that the 298 Wh/kg will be slashed substantially for any application that is not "low power over extreme intervals". Even for such an application, 298 Wh/kg is not "one order of magnitude higher than that of lithium-ion batteries". However, it is also not one order of magnitude less, which means that this is a technology to keep an eye on.
"El Reg is not at fault here though. Whoever wrote that press release either was being willfully misleading or ignorant of the matter at hand."
Well, I'm afraid they are. What you raise are excellent points that occured to me too, and it doesn't take a great deal of knowledge to note that Ah is not a unit of energy storage. Regurgitating tracts of press release without asking obvious questions is surely closer to churnalism, than journalism.
No they haven't. They have demonstrated that a hypothetical energy source can be made to produce electricity.
The day that that process can be found in a battery is decades away if all the previous impressive declarations of these past years are anything to go on.
Not knocking the work in any way - I find what they did quite interesting - just putting things in perspective.
Let's face it, it's the beginning and on a very limited basis. They've not explored all the potential of this cell. I would hope that down the line they find a way to make it scalable and economically feasible. Just the thinking alone could lead to something even better.
The team deserves a beer for exploring some uncharted territory in research that could benefit us all.
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