Portable Laptop Computer Charger Plan

[John J.]

I use my laptop off a 12v adapter/converter at camp sometimes but it stays at camp. Still draws about 2.5 - 3 amps. Just a note on that - while universal adapters may work I feel it's better to match the oem power requirements. Typically found/stamped on a oem 120v charger. If your mobile maybe some kind of smartphone. Take a look at a charger for one of those and see what the output is.

[inetdog]

Understood that but some loonies on green sites don't

I like the part about hitchhiking!

Hitchhiking is very green. Saves on carbon footprint.

[russ]

Russ -do you understand that I was joking??
By the way - when hitch hiking
1. I can charge the laptop from the car 12v
2. I am not the one that pay for the fuel

Understood that but some loonies on green sites don't

I like the part about hitchhiking!

[SolarWatt]

Russ -do you understand that I was joking??
By the way - when hitch hiking
1. I can charge the laptop from the car 12v
2. I am not the one that pay for the fuel

[inetdog]

Some fools actually suggest mounting a turbine on the car to generate power - never realizing they are spending more power to turn the turbine than it will generate.

Not nearly as weird as someone who wants to design a piezoelectric layer inside a car tire to make use of the power that would otherwise be "wasted" in the flexing of the tire.
Or the person who proposed using an electric resistance heater and then adding some Seebeck effect thermovoltaics to use the concentrated heat of the element to generate electrical power that can then be fed back into the resistance element to supplement the outside power. Since the heat is being transferred to the room air anyway, the extra electric power must be free right?

Actually, it takes a little bit of thinking to understand why that last one does not really work. (Not just the general laws of thermodynamics, but the specific energy balance for this situation.)

[russ]

No, but when I'm hitch hiking - I will put the turbine outside of the car window.....

Some fools actually suggest mounting a turbine on the car to generate power - never realizing they are spending more power to turn the turbine than it will generate.

[SolarWatt]

Do you plan to put that on your head and run really fast?
.

No, but when I'm hitch hiking - I will put the turbine outside of the car window.....

[inetdog]

By the way - does anyone knows a good wind turbine of ~50W ??
S.W

Do you plan to put that on your head and run really fast?


Actually, since any turbine regardless of size benefits from mounting high off the ground, a 50 watt (nominal in 25+ mph wind) is probably considered too small to be worthwhile for reputable manufacturers. There are probably uses for that size in far off-grid unattended low power situations, but I am just not aware of any sold to the home market.

[SolarWatt]

So what are we saying - there is no device that a man can carry which have enough capacity to power laptop ??

I think that the answer is - No there is no such device.

Unless you don't mind walking with 50W panel on the top of your head.

By the way - does anyone knows a good wind turbine of ~50W ??

S.W

[russ]

Actually, the description shows the voltage (probably Voc, of course) increasing linearly with RPM. That is not BS. But there will not be a linear relationship between windspeed and either no-load or max power RPM. The Vmp for a given RPM will also probably not increase linearly as Voc does.

That table may be accurate but still either useless or misleading.

Sorry Dave but the spec is BS as best I can tell -

[SolarWatt]

Okay Okay......
I just read about Betz law in wikipedia - very interesting.....

[russ]

From Betzs law - The key concept that this formula shows is that when the wind speed doubles, the power available increases by a factor of 8.

[russ]

in a 10 mph wind, a 10 square foot rotor would likely put out 17.5 watts. A perfect turbine would put out 29.5 watts. If the turbine you are looking at does better than that, there's something wrong with their data.

Power Curve (Watts)
Wind Speed mph -[m/s]	Betz Limit per m^2	Good Turbine per m^2	Betz Limit per ft^2	Good Turbine per ft^2
1 - [0.45]	0.031	0.019	0.00295	0.00175
2 - [0.89]	0.254	0.151	0.0236	0.0140
3 - [1.34]	0.857	0.508	0.0796	0.0472
4 - [1.79]	2.031	1.205	0.1887	0.1119
5 - [2.24]	3.966	2.353	0.3685	0.2186
6 - [2.68]	6.854	4.066	0.6367	0.3777
7 - [3.13]	10.88	6.457	1.01	0.5998
8 - [3.58]	16.25	9.638	1.51	0.8954
9 - [4.02]	23.13	13.72	2.15	1.28
10 - [4.47]	31.73	18.82	2.95	1.75
11 - [4.92]	42.23	25.05	3.92	2.33
12 - [5.36]	54.83	32.53	5.09	3.02
13 - [5.81]	69.71	41.36	6.48	3.84
14 - [6.26]	87.07	51.65	8.09	4.80
15 - [6.71]	107.1	63.53	9.95	5.90
16 - [7.15]	130.0	77.10	12.07	7.16
17 - [7.60]	155.9	92.48	14.48	8.59
18 - [8.05]	185.1	109.8	17.19	10.2
19 - [8.49]	217.6	129.1	20.22	12.0
20 - [8.94]	253.9	150.6	23.58	14.0
21 - [9.39]	293.9	174.3	27.30	16.2
22 - [9.83]	337.9	200.4	31.39	18.6
23 - [10.28]	386.1	229.0	35.87	21.3
24 - [10.73]	438.7	260.2	40.75	24.2
25 - [11.18]	495.8	294.1	46.06	27.3
26 - [11.62]	557.7	3330.8	51.81	30.7

[inetdog]

A useless piece of junk. The specifications are made up BS. The voltage increases linear with the wind speed which does not happen. There is no overspeed protection.

Actually, the description shows the voltage (probably Voc, of course) increasing linearly with RPM. That is not BS. But there will not be a linear relationship between windspeed and either no-load or max power RPM. The Vmp for a given RPM will also probably not increase linearly as Voc does.

That table may be accurate but still either useless or misleading.

[russ]

Check this link:

http://www.ebay.com/itm/NEW-WIND-TURBINE-GENERATOR-AIRE-50-WATT-BATTERY-CHARGER-4-BLADE-/271090224237?_trksid=p2045573.m2102&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D146%26meid%3D3373254261879073856%26pid%3D100034%26prg%3D1079%26rk%3D3%26sd%3D200739054519%26

Can it help ??

A useless piece of junk. The specifications are made up BS. The voltage increases linear with the wind speed which does not happen. There is no overspeed protection.