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lgx198437

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Joined: 10/02/2009
Location: China
Posts: 11

Posted: 06:14am 02 Mar 2009

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Hi Everbody,

We want to install a samall power electric solar system.

the system can support the 2pcs 9W/12V DC lamp.the sunny time is 5 hours per day, continue cloudy time is 3 days.

The assemble as follows:

50watt solar panels

12V/5A charge controllor.

12V/50AH solar battery

2pcs 9W/12V DC lamp.

The design is fit for load? any suggestions?

Thanks in advance.

Gary

Gary liu
Msn:gui.xiang@hotmail.com
Skype:lgx198437
Email:lgx198437@126.com

davef
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Joined: 14/05/2006
Location: New Zealand
Posts: 499

Posted: 10:38am 02 Mar 2009

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How long do you want to run both DC lamps for each day?
Are you going to move the panels to track the sun or leave them in a fixed position?
Does sunny time mean 5 hours totally clear sky? Also, it depends what time of day those 5 hours are.
Where in China (your latitude) will the system be installed?
Is that one 50 Watt solar panel?

If one 50W panel is fixed in position, due south and at an angle which corresponds to your latitude and those 5 sunny hours are around 12noon I would expect the following:
9AM to 10AM 20Watts
10AM to 11AM 35Watts
11AM to 12PM 50Watts
12PM to 1PM 50Watts
1PM to 2PM 35Watts

for a new panel and around the times of year when the sun is directly perpendicular to the panel. This gives you a maximum of 190Watts.

I would only count on getting back about 75% (you should Goggle for a better estimate) of what you put in the battery, say about 140Watts.

So, if you have 3 cloudy days that 140Watts is divided by 3 to give about 50Watts available per cloudy day.

Your two lamps draw 18Watts, so that gives you about 2.5 hours of use each night.

You will get about 40% more power if you track the sun, but for a small system like this it probably is not worth the extra money, unless you do it manually.

The controller looks appropriate for your system. With a fully charged 50A/H battery and at a discharge rate of around 2.0Amps (your 2 lamps) you should get around 27 hours running time.

13.5Volts * 50A/H = 675Watts * .75 = 487Watts divided by 18Watts = 27 Hours running time

The battery appears to be about 4 times bigger then required for your stated application (3 days at 2.5 Hours = 7.5 Hours). However, they are probably the cheapest size of battery to buy. Batteries become more inefficient as they age and it having extra battery capacity allows you some flexibility.

Also, even on a cloudy day you get some charging. I often see 1Amp on a cloudy day when the maximum is about 7Amps in full sunlight.

Good luck!Edited by davef 2009-03-03

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 12:57pm 02 Mar 2009

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This looks very suspiciously like a homework question

Klaus

davef
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Joined: 14/05/2006
Location: New Zealand
Posts: 499

Posted: 07:20pm 02 Mar 2009

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Oops.

lgx198437

Newbie

Joined: 10/02/2009
Location: China
Posts: 11

Posted: 06:25am 03 Mar 2009

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HI Davef,

your answer is very professional

Gary liu
Msn:gui.xiang@hotmail.com
Skype:lgx198437
Email:lgx198437@126.com

davef
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Joined: 14/05/2006
Location: New Zealand
Posts: 499

Posted: 09:27am 03 Mar 2009

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Obviously, as you have no further questions!

Hope the installation works well. Perhaps you would like to give feedback on whether or not it did work as suggested or what mark you got for this assignment.

Edited by davef 2009-03-04

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