Hello all .
Do you like to open a conversation about solar and wind energy ?
I found out it, for to have free power for a laptop 24/24 at day.
But i saw the cost is very high : 2 solar panels total 160 watts ,batterie one 200 mAh ,inverter 12 volt -220 volt ac 300 watts ,and one regulator charge ,total cost here to Greece 1100-1300 euro for to have 60-70 watts 24 hours a day .

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During my previous career, I designed, built, and installed low power solar telemetry installations.

In my experience, solar power at anything less than a commercial scale is still generally only affordable in combination with some other subsidy or incentive.

That could be tax incentives from the government. However, it can also be the remoteness of the site from mains power, therefore the avoided cost of construction.

In the latter case, there's a direct relationship between the amount of power required and the distance/construction costs to make solar cost-effective.

Here in the US, we're starting to see solar powered LED traffic signs where mains power is only a few feet away. For my telemetry sites, mains power might have been a block or 2 away. For a home, the magic distance might be a half mile or so.

Here are my rules of thumb for small systems in Central California. A purely solar system needs to be designed for worst case.

1) Solar panels need to supply enough power in 5 hours (peak sun on the winter solstice) to supply at least 24 hours of system power. Then the panel size needs to be increased further to allow for derating for X number of consecutive overcast days. I figured on 50% output for 5 straight days.

2) Battery life is increased by not deep-discharging them (below 50% of capacity). Therefore, the size of the battery bank needs to be at least doubled, based on the above assumptions.

3) Solar panels are less efficient in hot weather. Batteries are less efficient in cold weather. The former is less of a problem, because hight temps usually happen during longer periods of sunshine. The latter means the battery bank may need to be upsized even more depending on the climate/environment.

4) Don't rely on any nameplate data for inputs to the above calculations. Measure everything. And, if the design includes an inverter, remember that they are not 100% efficient.

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Let's start with the load, and average it to 65 watts. That's 65 x 24 hours = 1,560 watt-hours for a day. That's how much the panels needs to produce, and how storage you should start with. I'm used to designing 12 volt systems, and watts = volts x amps, so 1,560 watt-hours / 12 volts = 130 amp-hours. Assuming that you really meant 200 AH battery when you said 200 mAh, that's a good start. The panels will supply a few hours of power each day, so the batteries don't have to supply a full 24 hours of power. However, the battery bank would last longer if it was at least 250-300 AH at 12 volts.

1,560 watt-hours required in a day / 5 hours of real sun (California) = 312 watt solar panels required for the dead of winter here. 1,560 / your 160 watts of panels = a minimum daily effective sun of 9.75 hours. I checked Athens amount of daylight vs: San Luis Obispo for 21 Dec. We're both in the Northern Hemisphere, and you have about a half hour more than we do. So, I think your panels are a little undersized.

You can save some money and some efficiency if your laptop happens to run on 12 volts DC. Then you don't need the inverter. Unfortunately, most current laptops seem to run on odd voltages like 19 volts. In that case, it's more effective to just use an inverter, rather than try to build a 19 volts solar supply.

Having said all of that, the first thing to do is measure your laptop power consumption with a fully charged battery. I'll wager that you'll find it's substantially less than 65 watts. That AC power supply has to power both run the computer and charge a fully discharged battery.

I think that if you were to build your system with the specs and conditions you gave above, it would work fine for 8-10 months of the year, and be a little iffy the rest of the time. If the computer really draws substantially less power, then your design will probably be just fine.

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Thanks, that was really interesting to read. I have been giving some thought to solar or wind power in my home. (latitude 39 degrees S) . We get circa 2200 hrs of Sun, with a reasonable proportion in the winter months plus a fair amount of wind, though the run isn't constant, of course.

Another thanks to Sloweather for the calculation to solar panel .
Yes the batterie is 200 Ah ,and no 200 mAh from my mistake.
My laptop runing with 19 volt ,unfortunately for this reason i thinking the inverter .
One question ,how is the cost to USA for one panel 160 watts ,one baterrie 200 Ah ,one regulator charge,and one inverter 300 Watts ?
I thing here to Greece is more expensive .

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All From Backwoods Solar Electric Systems

2- 85 watt Kyocera panels
$485 x 2 = $970

2- 6 volt Trojan Golf Cart batteries, 225 AH
$152 x 2 = $304

SCI Mark 22 22 amp controller (need at least 14 amps)
$108

Xantrex Xpower 400 watts
$45

$1,427 without tax or shipping (970 euros according to Google.)

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Thank you Sloweather.
Finally i see the solar energy is expensive yet everywhere .
And i beleive it is not absolutely free ,the day is free ,but the night we need bateries and the bateries it have high cost to change it every 3-5 years (here to Greece one batery closed type 12 volt - 200 AH it cost 380 euro or 528 dollars). Do you understand to have 10-15 bateries this type parallel ,and you change it every 3-5 years how big is the cost .And all this if someone he want to have solar energy inside all house ,and do not need the electricity company ,but this is a very high cost ,and my personal opinion is the solar energy is only yet for helpful the main electricity power .
Yet the cost for solar panels ,bateries is high ,and the wind generator is more expensive ,and it want areas with strong wind over to 25 km/h for work .
I like the idea for solar-wind energy but yet it have high cost the all equipment.

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And not only the financial cost - also the environmental. I am certainly no physicist, but in the great school of life I have learned that there is no such thing as a free breakfast!

I have a 6 turbine wind farm 500 yards away. There are five or six monster farms within a few miles of here. They are an eye sore. And noisy. Over the years i have watched these being built. The huge amount of energy that must have gone in to their manufacture, transport and erection, plus the cost of the road and pylon infrastructure, must surely outweigh any benefits? Add to that maintenance costs. And by the time (if they ever do) they have paid for themselves they are falling apart and need replacing.

And, I understand, the farmers do very nicely out of annual way-leave payments.

Just my humble opinion.

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Thank you ,and i agree with you Grey-Owl ,if the cost at solar panels - turbines and bateries do not decrease ,i thing yet the solar-wind energy is prohibitive ,for this where it offer .

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My god sloweather you know your stuff, very impressive.