Comment by justaaron | Hacker News Reader

Comment by justaaron | Hacker News Reader

i live off grid inside of a 500w/h peak footprint. i paid around $1000 for proper German (Schutten) panels, a charge controller suitable for them, 2 110ah "solar batteries" (lead acid usual cheapo old school stuff), and a Xantrex inverter. After nearly 1 year running a fridge, lights, computer, router, & studio monitors, I'm ready to add more battery capacity before the winter (cloudy days) and a small wind turbine.

grid-tie systems are another story and a bigger investment. (need a proper electrician to wire it etc...)

feeding ignorant "city ways" in terms of people's silly habits fed by years of cluelessness (no a hairdryer will never ever be possible, as that's 2kw right there...) that's where the biggest expenses come in... if you don't try to keep up with the usual clueless electrical consumption, a well organized person can begin cutting their footprint down...

for example my alleged 85w macbook pro power supply consumes less than 20w typically... my inverter says so...

If you're up for it I still have my 2500 W windmill here and can't use it so you can have it, the base is damaged (slip rings, tower shaft and tower mount) and you'll need to put up a pretty solid tower. It's a 2.5 meter diameter machine.

See:

http://jacquesmattheij.com/how-to-build-a-windmill

It weighs about 100 Kg and it's currently in storage near the town of Beverwijk in NL. It cost a small fortune to make it and I'd rather see it being used than slowly rust away in storage.

What a fantastic project - thanks for documenting and sharing!

Do you always use your MBP connected to a power outlet? If so, try running it until its battery is drained about 50%, then plug it into your inverter and see how much power it draws. My guess is it will draw about 50-60 W.

I've been using a pedal-powered generator to power my computer, phone, tablet, and LED lights for the last 5 years and have tested several laptops and other devices using it. I've found that most laptops draw from 12 W (11" Chromebook) to 25 W (older 15" Dell) when their battery is charged, but 40-60 W when charging. The power supplies of most devices seem to have about a 50% safety factor, so a device that has a normal max power consumption of 50 W will use a 75 W power supply.

How much electricity can you generate? Just thinking off the top of my head, I'm a sucky cyclist so can only manage about 150W power output sustained, probably. I'm not sure I could handle more than an hour of stationary biking before I collapse in a puddle of sweat ;-) So that's about 150 WH...

Is that about right (ballpark), or have I missed something? It would probably power my laptop for the day, anyway... It's something to think about (since I love cycling, even stationary ;-) )

Most people seem to be able to comfortably produce 30 W over a sustained period of time.

If you're used to bicycling, dress appropriately, and work in a cool environment with a fan, you can produce 50-60 W.

Above that, it becomes difficult to maintain your concentration on your work while trying to pedal hard at the same time.

On most days, I maintain about 35-50 W, depending on the load.

So far this morning, I've ridden for 2 hrs, 5 minutes and produced 74 W-hr. The computer I'm using this morning is a Raspberry Pi2 with a 19" monitor. I'm also powering our DSL modem/router and a 12 V fan while recharging two tablets, four AA batteries, and my phone at the same time.

I wonder how much inefficiency there is due to the inverter and the computer's wall transformer. Would it be better to run DC from the generator to power a dc-dc converter (which might have its own losses)?

Yes, it's definitely better to power everything using DC if possible. The best, reasonably-priced inverter I've found still draws 2 W whether it's powering anything or not. But it's difficult to get the right voltage and connector for every electronic device you might want to power.

That 85W rating on your Macbook Pro power supply is it's peak power output. Typically it will be much less.

"no a hairdryer will never ever be possible, as that's 2kw right there"

You don't mention the model of Xantrex inverter but the 813-3000-UL is a 3 KW model.

I'm old enough that when I was young inverters and switching DC-DC and power supplies in general cost about a buck a watt, now its ten cents and dropping. That would have been $4000+ decades ago, now its about $300 delivered.

That's not the only cost, of course, 3 KW at 12 V is a non-trivial DC current, and two hundred aH isn't going to run that hair dryer for hours, but how much hair do you have to dry anyway?

Can you expand on your views on ignorant city ways? Just because you don't need to run a hairdryer does not make everyone else ignorant and clueless.

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