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Electric cooking in the wilderness – a rough analysis


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  • #1306522
    Rex Sanders
    BPL Member

    @rex

    I know what you are thinking – Are you crazy? Who would cook with electricity in the wilderness? Why?

    I'll run the numbers, so we'll see how crazy that might be.

    But first:

    – Most backpackers use a battery-powered flashlight or headlamp, instead of a candle or no light. Are they crazy?

    – Some backpackers use a battery-powered GPS instead of a compass, paper maps, and navigation skills. Are they crazy?

    – Some backpackers use a battery-powered cell phone, satellite phone, or satellite messenger, instead of developing more self-reliance, and more tolerant families. Are they crazy?

    Why would someone want to cook with electricity in the wilderness?

    – Fire bans, which are becoming more common because of the left-wing global warming conspiracy.

    – Some people are afraid of cooking over a flame. Don't laugh, I have friends who grew up with electric stoves and are afraid of cooking with flames.

    Important concepts

    Energy is potential work. The energy in a battery is like the gasoline in a car's tank. Electric energy can be measured in Watt-hours.

    Power is how fast you spend energy. Some batteries can push out energy faster than others. The power of a battery is like the engine in a car. Electric power can be measured in Watts.

    Some cars have large tanks (high energy) and small engines (low power); some have small tanks and large engines; most are in between. Batteries are similar.

    So how could we cook with electricity in the wilderness?

    Caveat: I am not an engineer. If you are, please be kind in your comments!

    Goal: Bring 2 cups of 1° C (34° F) water to a boil in about 10 minutes.

    That's a a little slow, but tolerable.

    To raise 2 cups of water by 99° C takes about 55 watt-hours of energy.

    Delivering 55 watt-hours in 10 minutes takes 330 watts of power.

    … assuming we have 100% conversion of electricity to heat (good assumption), and 0% heat loss from the stove and pot (bad assumption).

    Assuming our stove and pot are 67% efficient, we need about:

    83 watt-hours of energy
    500 watts of power

    How do we deliver 500 watts to a pot holding 2 cups of water?

    Four 120-watt immersion heaters would be close enough:
    immersion heater

    Crammed into a pot with a cozy:
    pot with cozy

    Someone could make a better setup, these are off-the-shelf.

    Where do we get 83 watt-hours and 480 watts of electricity?

    Option 1: Lithium AA batteries

    One Energizer Ultimate Lithium AA battery can supply 4.5 watt-hours at 4.5 watts (being generous).
    AA battery

    We need to supply 12 volts to the immersion heaters. We could use an 8-battery pack like this:
    battery pack

    We need 4 battery packs running in parallel, for each heater, to get enough watts.

    128 batteries total cooks almost 7 meals, weigh about 1856 grams (4 pounds), about 265 grams (9.3 ounces) of "fuel" weight per meal. At $2 per battery, that's about $37 per meal.

    Total weight about 2600 grams (5.7 pounds) for batteries, cases, wiring, and immersion heaters.

    This particular setup might have other problems. A custom design could be a little lighter and more efficient.

    But almost any backpacking stove on the market will be much lighter and much cheaper, even this one:
    Stansport stove

    Option 2: Alkaline D batteries

    Consumers cannot easily buy Lithium D batteries, so we'll try Alkaline D batteries.
    D battery

    Alkaline D batteries have more energy than Lithium AA batteries, but D's are much less powerful (bigger gas tank, smaller engine).

    We need about 640 Alkaline D-cells weighing over 200 pounds to deliver 480 watts. I won't do the rest of the math.

    Rechargeable batteries

    We can choose from many different rechargeable battery chemistries – Lead Acid, AGM, NiCad, NiMH, several varieties of Lithium, and more. Lithium batteries are clear leaders in power and energy per gram, though rechargeable Lithium batteries store much less power per gram than single-use Lithium batteries. For more than you really wanted to know about batteries, try Battery University at http://batteryuniversity.com/learn/.

    We want rechargeable Lithium batteries that yield 480 watts and 83 watt-hours for the lowest weight – assuming we can recharge completely every day.

    There are hundreds, if not thousands of different rechargeable lithium batteries available. After about one hour of searching, I settled on this lightweight motorcycle battery:
    Shorai battery

    Each battery yields 240 watts and 252 watt hours, and weighs 1,370 grams (about 3 pounds). We need two of these batteries to supply enough power, but we can cook about six meals before requiring a recharge.

    That's 6 pounds of batteries, and we don't have a way to charge them yet.

    With more research, we might find batteries that yield 480 watts and 83 watt-hours.

    But the total battery weight is likely to be at least 2 pounds, and we still need a charging system.

    I'll stop here.

    Super Capacitors

    Super capacitors sound sexy, but their energy density is 20x-40x lower than lithium batteries, their voltage drops linearly with discharge, and they have other engineering challenges. Not analyzed.

    Conclusion

    Surprise! Electric cooking in the wilderness is not very practical. But if you really need to, you can.

    I'll stick to Esbit tablets in a Trail Designs stove.
    Trail Designs stove with Esbit

    — Rex

    #2015125
    Bob Gross
    BPL Member

    @b-g-2-2

    Locale: Silicon Valley

    I can envision that it might happen someday, but it would need a super efficient solar panel, and that might be too large to be practical for now.

    –B.G.–

    #2015126
    Rex Sanders
    BPL Member

    @rex

    Unless you brought rechargeable batteries (see above), you could use the super efficient solar panel only during the sunniest parts of the day.

    Might as well use a solar cooker, probably more efficient. And just as useless on a cloudy day or in a forest or deep canyon.

    — Rex

    #2015127
    Rex Sanders
    BPL Member

    @rex

    The lightest portable generator I could find with a few minutes of searching generates 450 watts continuous (about right), but weighs about 11 kilograms (24 pounds) with fuel and oil (not good):
    generator

    On the other hand, you could cook 20 meals with a full tank, using only 51 grams (1.8 ounces) of fuel per meal!

    — Rex

    #2015144
    Rick Reno
    BPL Member

    @scubahhh

    Locale: White Mountains, mostly.

    Just run a long line of windmills all along the Pacific Crest Trail(it's on the crest, right? it must get a lot of wind!), and then you can just plug in your little immersion heaters whenever you feel the urge for a nice warm cuppa!

    For the CDT you might need some of those huge solar mirror thingies instead.

    The AT, regrettably, is not all that sunny and in many places under the canopy of the forest for long distances. Little mini one-cup hydros at every stream crossing, or maybe a series of small nuclear power plants. You could disguise the cooling towers with cute little trees like on the cell phone towers, though, and nobody would ever notice.

    #2015150
    James Marco
    BPL Member

    @jamesdmarco

    Locale: Finger Lakes

    Hey, ha…plugging in to the local stump has always been a life long ambition.

    #2015155
    spelt with a t
    BPL Member

    @spelt

    Locale: Rangeley, ME

    – Some people are afraid of cooking over a flame. Don't laugh, I have friends who grew up with electric stoves and are afraid of cooking with flames.

    I discovered this a while ago and it still bemuses me. Not only is fire amazing and lovely, electric stoves are the pits!

    #2015167
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    Using your numbers, lithium AA has 4.5 Watt-Hrs and weighs 1/2 ounce = 9 Watt-Hr/oz

    Energy of combustion for butane = 49.5 MJ/kg = 390 Watt-Hr/oz (if I can calculate correctly : )

    Butane has 43 times more energy density than Lithium Battery

    That'll never work – you're crazy : )

    #2015220
    Michael Ray
    Spectator

    @thaddeussmith

    >>Fire bans, which are becoming more common because of the left-wing global warming conspiracy.

    Are you serious? And here i though it was those pesky forest fires raging through much of the south/west, destroying wildlife and property. no no, it's because of the liberal agenda. *roll*

    #2015291
    Michael K
    BPL Member

    @chinookhead

    Michael……you have it all wrong…..the bans are b/c of that pesky anti-Christ Obama and his satanic servants…..duhhhhh :)

    #2015303
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    When are we going to look back on this with amusement like the McArthey "anti-communist" era?

    #2015428
    R K
    Spectator

    @oiboyroi

    Locale: South West US

    How about using the new hydrogen battery technology seen at outdoor retailer?

    #2015431
    Bob Gross
    BPL Member

    @b-g-2-2

    Locale: Silicon Valley

    "How about using the new hydrogen battery technology seen at outdoor retailer?"

    They must be trying to use a hydrogen atom with the nucleus stripped off.

    Geez, I thought we went to the moon in 1969 using fuel cells.

    –B.G.–

    #2015487
    Rex Sanders
    BPL Member

    @rex

    >How about using the new hydrogen battery technology seen at outdoor retailer?

    Most portable fuel cells are designed to recharge small electronic devices over USB, supplying 5 to 10 watts.

    You need 48 of those fuel cells to boil 2 cups of water in 10 minutes.

    You can buy larger portable fuel cells, like this one:

    Hydropak fuel cell

    but you need 10 of them, and they weigh 3 kilograms (6.6 pounds) each with fuel cartridge.

    — Rex

    #2048761
    Rex Sanders
    BPL Member

    @rex

    I'm not the only one …

    http://www.wired.com/wiredscience/2013/11/how-many-batteries-would-it-take-to-cook-a-turkey/

    — Rex

    Spoiler alert:
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    263 D-cells

    #2048798
    Hiking Malto
    BPL Member

    @gg-man

    "Just run a long line of windmills all along the Pacific Crest Trail(it's on the crest, right? it must get a lot of wind!), and then you can just plug in your little immersion heaters whenever you feel the urge for a nice warm cuppa!"

    You may be on to something. There were plenty of windmills in SoCal that are becoming more plentiful by the day. There should be a congressional mandate to put a 4 plug 110 outlets at every windmill within half a mile of the PCT. cooking, electric blankets, device recharge, the possibilities are endless.

    #2048801
    humorless
    BPL Member

    @sleeping

    Locale: The Cascades

    "Hey, ha…plugging in to the local stump has always been a life long ambition."

    I've seen many a marriage get broken up because of that kind of thinking….

    #2048804
    scree ride
    Member

    @scree

    1and a microwave.

    #2048949
    Matt Dirksen
    BPL Member

    @namelessway

    Locale: Mid Atlantic

    I'm still waiting for the day that someone invents a scalable induction stove for the outdoors. That's probably the only technology that might allow for electric stoves to be feasible at a small scale.

    Matt

    #2048974
    Rex Sanders
    BPL Member

    @rex

    http://www.scientificamerican.com/article.cfm?id=sciam-50-see-through-tech

    One version even generates electricity—more than seven watts, enough to recharge phones.

    You need 72 packs wired together to generate 500 watts to boil two cups of water in 10 minutes.

    Under ideal conditions, you could provide 2 cups of boiling water to each of those 72 backpackers every 12 hours of hiking.

    Maybe we should wait for version 2.

    — Rex

    #2049004
    Peter Evans
    Member

    @nlslacker

    This is some excellent trolling/research…
    how about a wind up stove, similar to an emergency radio?
    How many winds to boil 2 cups?

    #2049027
    Rex Sanders
    BPL Member

    @rex

    A small Freeplay hand-cranked generator weighs 310 grams and generates about 8.5 watts if the FreeCharge is cranked energetically enough.

    Freeplay hand-cranked generator

    If you had 59 of these generators (and 59 people to crank them) you could bring 2 cups of water to boil in about 10 minutes.

    If you had a 100% efficient battery (exercise left to reader), one person could generate enough energy to boil two cups of water with about 1.4 hours of cranking.

    I suggest switching hands from time to time.

    — Rex

    More entertainment – Electronics on the floor: generators from wind-up torches.

    #2049062
    Rex Sanders
    BPL Member

    @rex

    Wikipedia says:

    A trained cyclist can produce about 400 watts of mechanical power for an hour or more.

    You could boil 2 cups of water in about 13 minutes generating 400 watts of electricity.

    #2049071
    Peter Evans
    Member

    @nlslacker

    Just for fun, how many BioLite stoves would it take to boil two cups of water?(electrically)

    #2049109
    Rex Sanders
    BPL Member

    @rex

    BioLite stoves are a triumph of engineering and marketing over real usefulness.

    BioLite stoves generate 2 watts. You can get 4 watts from a single AA battery!

    The extra weight of a BioLite stove over (e.g.) the Bushcooker LT-1, is equivalent to 60 Lithium AA batteries.

    But to take these calculations to a ridiculous extreme …

    You need 250 BioLite stoves to generate enough electric power to boil 2 cups of water in 10 minutes.

    In the process, you could have boiled over 2,000 cups of water over the wood fires.

    Enough calculations. I need to get back to writing BPL articles.

    — Rex

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