I've always worked on a rule of thumb of $1 per Watt for solar panels.
Places like Low Energy Developments might be a few more cents per watt but on the whole..........
But THIS LINK sounds just a bit too cheap at $139 or even less if you buy 2 or more for a 300W panel.
What might be the catch?
These is the only specs on offer.
Wattage:300W
Max Power Voltage:18V
Max Power Current:16.6A
Efficiency:More than 17%
Dimension:1225*680*30mm
????Efficiency: More than 17%??????
In the swords of the younger generation....WTF???
Guaranteed to be at least 18% efficient? So does that mean that 300W is at 100% efficiency but at 17% it will only be 50W so, you'll get somewhere in between these two numbers?
My neighbour found these. If they're any good I might grab a couple myself.
Jim
Too cheap?
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Grandad
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Too cheap?
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jon_d
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Re: Too cheap?
No, Jim.
300W.
Average panels are between 15-19 ish %. High grade quality ones are up to 23-24%. Hence why they are cheap.
300W.
Average panels are between 15-19 ish %. High grade quality ones are up to 23-24%. Hence why they are cheap.
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Grandad
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Re: Too cheap?
So, can you explain this efficiency thing for me please?
Was I on the right track with you can only expect 18% of the 300W advertised if it's rated at 18% efficient?
Jim
Was I on the right track with you can only expect 18% of the 300W advertised if it's rated at 18% efficient?
Jim
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jon_d
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Re: Too cheap?
It's the conversion factor. Size vs output.
eg A panel with
25% efficiency is smaller than a 17% panel for the same output and light input
https://news.energysage.com/what-are-th ... he-market/ it's discussed here towards the bottom
eg A panel with
25% efficiency is smaller than a 17% panel for the same output and light input
https://news.energysage.com/what-are-th ... he-market/ it's discussed here towards the bottom
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T1 Terry
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Re: Too cheap?
The average solar radiation that hits the earth's surface at sea level is 1,000w per square meter. If you have a panel that is 17% efficient, they are claiming it can harvest 170w per sq mtr. Module efficiency is not panel efficiency, panel efficiency is always less because of all the junctions and progressively increasing voltage as the module output from each is added to the next and so on, then diodes and ....... Yeah, it's an exacting science that is rarely if ever close to being exact. All panels are rated at an STC bench mark, this involves a 5 sec flash on a light box at 25*C ambient and panel temperature, no actual sun involved, so nothing to do with how they will actually perform out in the sun in Australia in the middle of summer.
Another common trick used by those who tend to deceive using B/S figures, they multiply the open circuit voltage (Voc) by the short circuit current (Isc). Each of these figures on their own can be used to test if the panel is functioning as specified, but the genuine output current (amps) (Imp) at the very highest voltage before the amps start to drop off (Vmp) will always be lower and is the genuine B/S figure used to compare one panel with another. Why I say this is the genuine B/S figure, a solar panel in full sun will not be still at 25*C yet this is the temp used for STC testing where they come up with these numbers.
Solar bought in bulk lots can be down as far as 50c/watt, $1 per watt for quality new panels is still the bench mark if buying 12v panels under 150w.
We are buying second hand Tindo 250w panels for $100 each at the moment, cleaned and polished they are still putting out their rated 250w in full sun, yet just about all the second hand panels fitted by the " as seen on TV " specialists that appear on evil bay and that tree site seem to put out about half of what is claimed if anything at all, so ....... You can pick up cheap panels but be prepared to test them before you actually determine if they are good value for money and area they will cover.
T1 Terry
Another common trick used by those who tend to deceive using B/S figures, they multiply the open circuit voltage (Voc) by the short circuit current (Isc). Each of these figures on their own can be used to test if the panel is functioning as specified, but the genuine output current (amps) (Imp) at the very highest voltage before the amps start to drop off (Vmp) will always be lower and is the genuine B/S figure used to compare one panel with another. Why I say this is the genuine B/S figure, a solar panel in full sun will not be still at 25*C yet this is the temp used for STC testing where they come up with these numbers.
Solar bought in bulk lots can be down as far as 50c/watt, $1 per watt for quality new panels is still the bench mark if buying 12v panels under 150w.
We are buying second hand Tindo 250w panels for $100 each at the moment, cleaned and polished they are still putting out their rated 250w in full sun, yet just about all the second hand panels fitted by the " as seen on TV " specialists that appear on evil bay and that tree site seem to put out about half of what is claimed if anything at all, so ....... You can pick up cheap panels but be prepared to test them before you actually determine if they are good value for money and area they will cover.
T1 Terry
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Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
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Mrcoolabah1au
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Grandad
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Re: Too cheap?
Thank you guys. I'm a little bit better informed now.
Regarding efficiency, I was obviously confusing what Terry refers to as module vs panel efficiency. I've only previously ever heard of one, not the other.
Jim
Regarding efficiency, I was obviously confusing what Terry refers to as module vs panel efficiency. I've only previously ever heard of one, not the other.
Jim
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native pepper
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Re: Too cheap?
Jim, you can get 24v panels for the same price on eBay which in my opinion is better because they produce up to 36v and with an MPPT controller, you get more energy for the price into a 12v system. Just have to be careful because some claim they are selling 24v panels, but they are 12v as they only have a 18v input. When you read the details they are saying they are 24v because they can be connected to 12 or 24v batteries, which is deceiving but we are dealing with chinese suppliers, so always have to realise they tend be deceptive in their claims.
You can get good stuff off ebay, just have to make sure you go through the specifications and take a shot of the advert you are working with, then if something goes wrong or they change the advert after your purchase, you have the original to use if you are making a claim. I never buy anything that doesn't provide the specs for the product in the advert, or you can get ripped off.
I recently bought a nexus 5 ph for my neighbour so she could switch to Ubports and get away from the intrusive apple and android. The seller claimed it had been fully refurbished, yet when I opened the back, it had a 6 year old battery, sent it back for a refund and found a new one for $20 more, they are a great ph even though they are more than 10 years old and come with up to 4-8 gig ram and 32-64gig storage.
You can get good stuff off ebay, just have to make sure you go through the specifications and take a shot of the advert you are working with, then if something goes wrong or they change the advert after your purchase, you have the original to use if you are making a claim. I never buy anything that doesn't provide the specs for the product in the advert, or you can get ripped off.
I recently bought a nexus 5 ph for my neighbour so she could switch to Ubports and get away from the intrusive apple and android. The seller claimed it had been fully refurbished, yet when I opened the back, it had a 6 year old battery, sent it back for a refund and found a new one for $20 more, they are a great ph even though they are more than 10 years old and come with up to 4-8 gig ram and 32-64gig storage.