Power, power, power

[azazel1024]

I thought I'd share a bit on power. The books aren't particularly accurate and they certainly don't go in to a whole lot of detail on generating or using power. So here goes.

There are many ways to generate power. The most likely and easiest to access for most is the cigarette lighter or power plug on a car; after that it is a car battery; a portable or standby generator; solar panels; wind; and finally microhydroelectric.

Vehicles

Basically all vehicles have a cigarette lighter and some even have power plugs on them. The power that comes out is 12v DC power and can be used for a number of things, but it isn't easy to use. Most devices run on 120/240v AC single phase power, which 12v DC most certainly isn't. A few devices such as cell phone chargers (worthless with no cell network, unless a safe haven community has gotten a cell tower or three up and running), GPS charger (very valuable) or a handful of similar devices are designed to plug right in and pull juice from the outlet. Also much knocked, but very useful is as a cigarette lighter. A perfectly reusable, easy to use fire starter when matches might not be the easiest thing to come by.

Most cigarette lighters have 15a fuses, that means a maximum power output of 180w. A power inverter is just the thing to use this power. A small inverter can convert that 12v DC to single phase 120v AC. The average 4cyl burns about 1/3rd of a gallon per hour, V6 around 1/2 gallon per hour and V8 around 2/3rds of a gallon per hour idling. This gives you an idea of just how much gas your going to burn through supplying this current.

Car battery

Car batteries are plentiful and easy to recharge if you have a car handy, just plop in the new battery and start the car up. If the new one isn't charged enough use jumper cables on the old battery to get the car running on the new one to charge it up. Car batteries vary in capacity, but they generally hold around 300w/hr of power. This means that you can run a device that needs 300 watts for 1hr or 1 watt for 300hrs and so on. Just like a car your going to need/want an inverter to utilize the 12v DC power. Unlike the car you aren't limited to a 'measely' 180w of maximum power output, you can draw as much as you want, you'll just run the battery down really fast. Car batteries weigh around 40lbs on average, so not easy to tote a bunch around with you. They are great as a storage system for when you don't want to be running a generator or other charging system.

Generator

Generators are fairly plentiful. Many homes have a standby generator and if you can get to a big box store you can probably find one. Standby generators are not made to be portable, but they can be transported okay (about as big as an AC compressor). They come in a variety of outputs from around 1500w up to around 15,000w. Fuel consmption varies, but a good rule of thumb is about 4,500w/hr per gallon of gasoline. Generators can be used to run things directly off of them or for charging batteries. Generators are designed with either 120 or 120/240v single phase AC power, so a battery charger/DC inverter is going to be required to charge batteries.

Solar power

If you look around solar panels are everywhere. Street signs, construction signs, sometimes on houses or other buildings. Solar panels vary in output, but most that you'll find on a street sign tend to be around 20w panels with construction signs being around 60w and home/building panels varying from about 60w for small panels up to around 200w for the really big panels. Houses and buildings can have anything from a single panel or two up to dozens.

Solar panels work by converting sunlight in to power. This of course requires sunlight so they aren't going to work during the day time. Also due to their limited power output the best way for a power system to work is using solar panels to charge batteries (example car batteries) and then run your equipment off the batteries. Solar panels generally produce 12v power and are always DC. Some areas are sunnier then others, so for ultimate realism you might want to look up "Insolation days ______" Where _____ is the city/area your group is in. That'll tell you what the average number of hours per day of sunny conditions is (this averages in length of day, how over cast it is on average, etc, etc). Example some places in the southwest average around 8hrs per day on average of direct sunlight to a low of around 3 for areas such as the US Northwest. Solar panels are relatively portable, but don't have nearly the same power to weight ratio that a generator does.

Wind

A poor man's windmill generator can be made with most people with some electrical skills and a few tools/supplies. However, they aren't going to be nearly as good as a commercial wind generator. In either scenario because of the variability of wind your best off with charging batteries to power equipment with wind power. Small wind generators such as for use on a boat are around 100-400w in output with larger mast mounted residential generators ranging from 1-3kw of output. A homemade cobbled together afair is likely to generate around 200-300w for 'farm style' windmill on a 20-30ft mast. (the huge windmills you see on ridge tops, etc generate from 400-3,000kw and you could certainl base a small safe have community around one or more using its power for the community).

Microhydroelectric

Kind of like wind mills, but placed in the water. This vary from literal windmills placed in to a river to small turbines lowered in to the water. All of these work on the principal of a stream or river flow turning blades to generate power. You can make one or find a commercial one. They don't generate much power, but are pretty compact. Outputs vary from 100-600w and are generally stable enough you could run equipment directly off one, but due to the lowish power output your best off charging batteries to run equipment off them.

Now for power use. This is the part that the book was really far off on and I hope to give readers a general idea of what a lot of different types of electrical equipment needs.

Power consumption is listed either per day for things that you are likely to operate 'long term' or continuous conumption (example arc welder).

A compact refridgerator (4-5cu-ft) 1kw/hr
Full size refridgerator (18-22cu-ft) 1.8kw/hr
Hotwater heater 4,500w@240V to heat water, takes about 150w/hr per gallon of hot water (IE heating 1 gallon of water uses 4,500w of power and uses 150w/hr of energy, or about 2 minutes to heat 1 gallon of water or for something like a 50 gallon hot water heater 100 minutes to heat all 50 gallons)
Electric oven/range 3,000w per range element, 5,000w for the oven all @240v
Hotplate 500w
CRT TV 27" 80 watts
LCD TV 37" 200 watts
LCD TV 50" 350 watts
DVD player 20 watts
Desktop computer and monitor 250 watts
100w incandescent light bulb 100w
100w equivelent compact fluorescent light light bulb 23w
Table saw 1,800w
Power drill 600w
7 1/2" circular saw 1,440w
Air compressor 1,200-2,500w
Electric welder 3,000-7,000w
-Matt

[azazel1024]

Any hydroelectric or wind power could be harnessed for years after the fact. It would take a bit of work and someone with some good electrical skills, but very doable. All require at least a limited amount of maintenance. You'd probably see some of the turbines start siezing up after a few years or electrical failures at a hydro plant, but for a complete shutdown it probably would take a few decades with no maintenance before no power could be generated. Wind is a little trickier because your talking about a single wind mill, of course if you mean say a dozen or so along a ridge line then odds are more in your favor. Not sure what MTTF for a wind generator is, but assume something like 5 years with no maintenance so out of a dozen you might have one or two still working after 10 years or so.
-Matt

[Gamer]

Those maintenance people may start to make demands for thier skills.
Without those people to maintain the substations that plant is useless.
Without the substations the plant is useless.
Without the parts to maintain the substation the plant is useless.

The plant can be generating raw power for years, but there may be no way to utilize it without the substation working properly and they are not automated.

[jaymz]

nice work, definitely useful info...

[asajosh]

Interesting.... How about Hover damn??

According to he speculation on Life After People, the Hoover Dam wil continue pumping out watts to the South West for perhaps a decade with out human interferance.