Suppose there were a zombie apocalypse (or similar event, such as a war or deadly epidemic). What could I do?
I live in a Buenos Aires apartment with two other people, about 29 meters from the street. If we could, it would be better not to leave the apartment if possible, preferring to conduct day-to-day life behind closed doors as long as possible.
Let’s suppose for the time being that we don’t need to provide our own air the way nuclear submarines and space stations do. What about the other necessities — food, water, medicine, warmth, coolth?
We have about 9m² of roof terrace and about 50m² of indoor space with 4m ceilings, a total of 200m³ of indoor space.
A food reserve probably needs 2500 kcal per person per day for each of the two adults, plus 1500 kcal for the seven-year-old, a total of 6500 kcal/day. If we want it to last a year, that’s 2.4 million kcal; if 40% of the calories are carbohydrate, 30% fat, and 30% protein — the desirable balance used in e.g. Clif bars — then that’s 950 thousand kcal of carbohydrate and 700 thousand kcal each of fat and protein. At 5 kcal/g, that’s 190 kg of carbohydrate and 142 kg of protein; at 9 kcal/g, that’s 79 kg of fat. The total is 411 kg of dry mass, or probably 500 kg of dry food, probably occupying about 500 ℓ, or about 250 two-liter plastic coke bottles, if it’s stored in that form.
We currently cook the food using the municipal natural gas supply; off-grid alternatives in case of catastrophe would include burners driven by LP gas cylinders, like the one that recently exploded the house of a friend of mine; alcohol burners; and solar cookers.
Lentils, as a representative cheap food, cost AR$5.20/kg in 10-kg bags. So 500kg of food would cost about AR$2600, which is currently about US$173. Of course, you wouldn’t buy 500 kg of lentils; you would buy a mix of different cheap foods. But this would be super cheap.
Right now I have a portable air conditioner set up in the bathroom drying my roommate’s sheets and towels. Dry laundry is essential to maintaining body temperature when it gets cold and damp. This machine uses 6 amps of 220-volt single-phase AC and can evaporate and recondense between 1ℓ and 10ℓ per hour (I haven’t measured carefully). (It also provides heat and cool when needed, although right now we’re heating the apartment rather expensively with a gas heater run off the municipal natural gas supply.)
Devices like this one cost about AR$5000 = US$333. It would be good to have a spare.
However, running it requires electricity. Maintaining electricity in the event of a zombie apocalypse would require being able to generate it locally.
We could drive the air conditioner off some car batteries and solar panels with an inverter, ideally on a pallet in a plastic tray under an awning on the roof terrace, so that if shit goes wrong it doesn’t blow up the house. But how much would we need?
220V × 6A = 1320W; 1320W ÷ 12V = 110 A. So we’d need batteries capable of 110 amps, which is easy enough as far as it goes, but we probably also need to be able to run it for a couple of hours at a time, which works out to 9.5 MJ or 2600 watt-hours. That suggests we need something like three deep-cycle batteries like the Trojan 27TMX, which holds 3.2 MJ by my calculations and can supply 530 amps. This gives the electrical system a “burst” capacity of 19 kilowatts.
These batteries cost AR$5100 each, so this is AR$15300 of batteries. Probably you’d actually want four so that you can put them in series strings of two batteries to get 24V, for a total of AR$20400.
There are 2000W inverters on MercadoLibre for AR$7500; they require 24V input.
Such an electrical system could also be used to run a microwave for cooking, lights, even electric stove burners.
Somehow you’d also need to charge the batteries. A 250-watt (peak) solar panel is 1.62 m² and costs AR$7000. Since this is 5.3 times less power than the air conditioner, a single one of these would require 5.3 hours of midday sunlight to recharge from a single hour of air conditioner use; it would be better to have two of them, for 500 watts peak and AR$14000. The roof has space for about six of them at most.
You also need a charge controller, which I think is about AR$1000.
So the total is AR$20400 + AR$7500 + AR14000 + AR$1000 = AR$42900 = US$2860.
Buenos Aires gets 1200 mm of rain per year, which is distributed fairly evenly through the year. That means our ≈9m² of roof terrace gets about 10.8 m³ of rain per year, or 10,800 liters; on average, that’s almost 30 ℓ per day, or 10 ℓ per person per day. Even at Burning Man, you only need about 6 ℓ per day per person, and you lose less water when you’re not in the hot sun in the desert.
So even a cistern system would work adequately, given adequate filtration and other measures against contamination. Transparent awnings covering 60% of the small terrace area would be adequate. Probably a month’s worth of water is adequate; that would be 6 ℓ × 3 × 30 = 540 ℓ. 500-liter drinking water tanks are readily available and cost a bit under AR$1000 = US$67.
Additionally, though, the air conditioner I mentioned earlier condenses water from the air, somewhere between 1ℓ and 10ℓ per hour. (If we figure that all of the 3000 kcal/h of cooling provided by a machine like this are provided by the condensation of water, whose heat of vaporization is 2257 kJ/kg, it would be 5.6 ℓ/h.) That means we can get water even without the cistern. It seems to be a bit jelled, though, and tastes funny; I suspect it may have some kind of microbial slime in it.
This calls for a 400× microscope with slides (AR$1000 = US$67) and a water tank.
Of course none of this is useful if the zombies can get in and bite us. The walls are concrete and therefore fairly zombie-proof, but it would be good to replace the apartment’s front door with a metal door, and add another metal door at the bottom of the stairwell, since an inhabitant of any of the other dozen or so apartments in our passage could get bitten and become a zombie. The stairwell is shared between only three apartments and provides us access to our roof terrace.
“Armored” doors from vendors like Pentagono cost on the order of AR$10000, and we would need three of them. This costs AR$30000 = US$2000.
(We have wood floors, but I think there may be a concrete subfloor.)
We need fire extinguishers, probably three of them. These cost about AR$700 each, for a total of AR$2100 = US$140.
Carbon monoxide detectors and flammable-gas sniffer alarms would be a good idea.
A catapult launching guided gliders from the roof would make it possible to get a look at what’s going on in the area and transmit radio signals to the rest of the city; the glider could return to the terrace to land, using a parachute to effect a vertical landing. If there are other survivors of the zombie apocalypse, we could send them small items.
What, are you kidding? You can’t kill zombies. Weapons are pointless. Just hide.
US$ 200 food
US$ 666 two portable air conditioners (I already have one)
US$2860 solar electric system
US$ 67 water tank
US$ 67 microscope
US$2000 armored doors
US$ 140 fire extinguishers
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US$6000 total