# Just confused about solar panel

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
Hi everyone!
I just wanna design PV system, but when i look on market the solar panel is too expensive. I found a seller who sell solar panel with 200 watt peak and rated 60 watt but the size is too small and too cheap to produce 200 watt peak. Here is the item on aliexpress, please help me observe this solar panel...

https://a.aliexpress.com/_d7BA7vg

#### Papabravo

Joined Feb 24, 2006
14,205
Why will it help you for us to observe this solar panel? I'm confused.

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
Why will it help you for us to observe this solar panel? I'm confused.
I just don't trust the item because the size too small to produce 200 watt peak and how can it is so cheap compare to another solar panel

#### Papabravo

Joined Feb 24, 2006
14,205
My first reaction is that you may not appreciate the changes in efficiency that result from continued research and experimentation. Observation may be helpful, but putting one on the bench at low to modest cost will yield better results more quickly. If you want to hit a home run in your first "at bat" by all means keep looking. If you actually want to learn something then get one and go for it!

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
My first reaction is that you may not appreciate the changes in efficiency that result from continued research and experimentation. Observation may be helpful, but putting one on the bench at low to modest cost will yield better results more quickly. If you want to hit a home run in your first "at bat" by all means keep looking. If you actually want to learn something then get one and go for it!
Thank's bro, i just need to try and learn more

#### Papabravo

Joined Feb 24, 2006
14,205
If it meets expectations -- let us know about it.
If it doesn't -- let us know about that too.

#### cmartinez

Joined Jan 17, 2007
7,060
That looks like a nice panel... and almost too good to be true, as you're probably suspecting. Papabravo is right, the only way to verify if it meets your expectations is to acquire one and test it to your heart's desire...

One thing I didn't find in its specs is its durability. All solar panels have a limited lifetime. Most high quality panels will work for about 10 years. But cheap-o ones will only deliver the goods for 2 years or less.

#### cmartinez

Joined Jan 17, 2007
7,060
Here's a thought. From the panel's specs:
• 21% efficiency
• Size of Panel: 620x540x2.5mm
• It's area is 0.620 x 0.540 = 0.3348 m²

The maximum solar power available on earth per square meter is 1,368 W

That means that, at 21% efficiency, receiving all of the solar illumination possible, its output should be:
• 0.21 x 0.3348 x 1368 = 96.18W

The specs do say that full continuous output power is 100W. I'll overlook the missing 4W here... but I fail to understand the 200W peak claim...

EDIT: The link I posted as reference to available solar power states that:
At the Earth's surface, the energy density is reduced to approximately 1,000 W/m2 for a surface perpendicular to the Sun's rays at sea level on a clear day
So the calculated number should be 70W, not 96W as I previously stated... something's fishy here...

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
Here's a thought. From the panel's specs:
• 21% efficiency
• Size of Panel: 620x540x2.5mm
• It's area is 0.620 x 0.540 = 0.3348 m²

The maximum solar power available on earth per square meter is 1,368 W

That means that, at 21% efficiency, receiving all of the solar illumination possible, its output should be:
• 0.21 x 0.3348 x 1368 = 96.18W

The specs do say that full continuous output power is 100W. I'll overlook the missing 4W here... but I fail to understand the 200W peak claim...
Yeah it is what i mean, this specs so confusing

#### cmartinez

Joined Jan 17, 2007
7,060
Yeah it is what i mean, this specs so confusing
I've just edited my post... check my addendum

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
I've just edited my post... check my addendum
Yeah, something's fishy here. Thank's for calculate it bro.

#### Papabravo

Joined Feb 24, 2006
14,205
Do things change if your are at a higher altitude?
Do they change if the panel is mounted in a way to maximize the available energy capture?

#### Audioguru again

Joined Oct 21, 2019
1,733
AliExpress and the seller do not say or do not know who makes the cheapo solar panel and they can say anything about it because they want your money and you are too far away to sue them.

I would buy a Name-Brand solar panel with spec's I can trust from a truthful chain of sports and car accessory stores near me.

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
AliExpress and the seller do not say or do not know who makes the cheapo solar panel and they can say anything about it because they want your money and you are too far away to sue them.

I would buy a Name-Brand solar panel with spec's I can trust from a truthful chain of sports and car accessory stores near me.
Right, this like a trap

#### Audioguru again

Joined Oct 21, 2019
1,733
I have never bought anything from Amazon because I like buying products I can see and touch.
But if I ever buy anything online then I would trust local Amazon more than those Chinese places.

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
I have never bought anything from Amazon because I like buying products I can see and touch.
But if I ever buy anything online then I would trust local Amazon more than those Chinese places.
I have bad experiences with chinese seller, they had tricked me many times... both item and service.

#### debe

Joined Sep 21, 2010
1,177
Average price for Solar panels here in Australia from reputable dealers is $1 per Watt. I have picked up good second hand 200W solar panels for free to$50 each. They have come from house solar systems. People here up grade to larger systems & the smaller system is either sold cheap or scraped. They are 44V DC panels but i re wire them to 22V DC for 12V battery charging with Regulator.

Thread Starter

#### Gembrotai

Joined Jul 2, 2019
28
Average price for Solar panels here in Australia from reputable dealers is $1 per Watt. I have picked up good second hand 200W solar panels for free to$50 each. They have come from house solar systems. People here up grade to larger systems & the smaller system is either sold cheap or scraped. They are 44V DC panels but i re wire them to 22V DC for 12V battery charging with Regulator.
What??? I wish i can go to Australia...

#### MisterBill2

Joined Jan 23, 2018
6,685
I just found this thread, and what I can offer is that PEAK anything is the absolute maximum possible, and may not ever be available under more normal conditions. And designing a system is a lot different than just assembling one. In addition, as others have mentioned, there is a huge spread in many of te quality aspects of a solar cell. Durability and weather resistance are the two most obvious considerations. So I advise caution and investigation before purchasing anything.

#### WBahn

Joined Mar 31, 2012
26,047
Hi everyone!
I just wanna design PV system, but when i look on market the solar panel is too expensive. I found a seller who sell solar panel with 200 watt peak and rated 60 watt but the size is too small and too cheap to produce 200 watt peak. Here is the item on aliexpress, please help me observe this solar panel...

https://a.aliexpress.com/_d7BA7vg
I think you are right to be suspicious of anything from AliExpress, especially when it is ships from China and Russia (don't know about Spain).

The test conditions that are used industry-wide call for an irradiance of 1000 W/m². Using the stated dimensions you have an area of, at most, 0.335 m², so incident power of just 335 W. To claim 200 W out of it would require 60% efficiency and even the 100 W would require 30% efficiency.

Assuming that the panel really is a monocrystalline panel at 21% efficiency, it is more likely that it should be rated at about 70 W. The current cost of such panels seems to be in the $0.60/W to$0.90/W, putting the price of that panel between $42 and$63, which seems like an amazingly close match to their offered price.

This is without any consideration for how long they will last.

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