PV panel value winner?

[phil.g00]

Assuming unlimited roof space.

Panel A is R1600 at  320W 16.5% efficiency.

The latest Sunpower equivalent panel is ( I dunno, I cant find an SA price) at a reported 22.8% efficiency.

Meaning the Sunpower  is about 37%  more efficient, meaning 37% more power for the same number of panels.

So I should be willing to pay 37% more for a sunpower panel. ( But i think they are at more of a premium than that).

So for  panel A R1600 /320W = R5/watt  at 16.5 % efficiency

While fictitious panel B might be R2000/335W = R5.97 at 21% efficiency

My thinking is:

Panel B is 21%/16.5 % = 27% better that panel A @ a cost of premium of 5.97/5 =  19.4% per watt.

So panel B is the better buy.

Has anyone compared various available solar panels and considered price/watt and considered efficiency?

Is there a clear value winner available on the SA market?

 

 

Edited October 28, 2018 by phil.g00

[Coulomb]

8 hours ago, phil.g00 said:

Assuming unlimited roof space.

...

So for  panel A R1600 /320W = R5/watt  at 16.5 % efficiency ...

While fictitious panel B might be R2000/335W = R5.97 [ presuming per watt ] at 21% efficiency ...

So panel B is the better buy.

? With unlimited roof space, you don't care about efficiency. You just care about price per watt, unless the extra space costs significantly in terms of racking, cabling, etc. Panels are getting cheap enough that those other costs are not negligible any more.

But with panel A at R5/watt and panel B at nearly R6/watt, it seems to me that panel A is the winner, ignoring those other costs, quality, etc.

[___]

6 hours ago, Coulomb said:

With unlimited roof space, you don't care about efficiency. You just care about price per watt

What he said :-)

Farming principle as well. You don't care about how much money you get per head of cattle. You care about money per hectare. That's a concept that is hard to explain to most Brahman farmers :-P

[phil.g00]

That sounds very logical. Thanks.

However, is it a simple as price/watt or is it actually price/watt-hour.

Picture two panels of equal wattage, say 300W, but with an efficiency difference of 14% and 21%. So one is 50% more efficient that the other.

I understand that both panels will equally produce 300W during peak hours, but the more efficient panel will wake up earlier and produce 50 % more power getting to 300w output earlier.

So I am still getting a higher number of watt-hours from the more efficient panel, that should be worth some sort of premium surely? 

[Gabriel_2018]

The difference is the space. If both are 300 w, and have the same relation of Decrease Power/Temperature, the result will be the same.

[Gabriel_2018]

The winer value could be NOCT. 

[Coulomb]

38 minutes ago, phil.g00 said:

the more efficient panel will wake up earlier and produce 50 % more power

What do you base that assertion on? I'm not saying you are wrong, just that I've never heard that before.

[___]

41 minutes ago, phil.g00 said:

However, is it a simple as price/watt or is it actually price/watt-hour.

Same thing. The hour component, on any particular day, will be a constant in that equation. I don't think the more efficient panel will start earlier... well maybe it will make enough for the MPPT to start a tiny bit earlier, but I doubt it's going to make a big difference.

[Gabriel_2018]

 Temp. coefficient of Pmax [%/°C]   -0.133 This is a data of mono panel.

 Temp. coefficient of Pmax [%/°C]   –0.44  This is a data of poly panel.

If we have a tipycal temperature of 50ºC in solar cells in both panels, we lose 3.325% in the first panel and 11% in the second panel. That loses are caused by temperature.

 

Edited October 29, 2018 by Javi Martínez

[phil.g00]

The way I understand: (open to correction)

The magic number is 1000W/m2.

At that level of sunlight both similarly sized panels produce their Wp of 300W.

So to my mind the efficiency comes into play at values less that 1000W/m2, when 1 panel can make 50% more watts from say 500W/m2 of sunlight.

Which to me means it starts producing earlier.

Or I may be understanding panel efficiency all wrong.

Edited October 29, 2018 by phil.g00

[Gabriel_2018]

Magics numbers are 1000 w/m2 and 25ºC in solar cells. If you have a panel 50% more efficient, two panels make the same production, but the most efficient is smaller. 

Edited October 29, 2018 by Javi Martínez

[Gabriel_2018]

6 hours ago, Javi Martínez said:

 Temp. coefficient of Pmax [%/°C]   -0.133 This is a data of mono panel.

 Temp. coefficient of Pmax [%/°C]   –0.44  This is a data of poly panel.

If we have a tipycal temperature of 50ºC in solar cells in both panels, we lose 3.325% in the first panel and 11% in the second panel. That loses are caused by temperature.

 

I can´t edit and there was an error in mono panel. The coefficient of Pmax is 0.29%/ºC

[phil.g00]

OK, I am with you, if it is unlimited roof space only price/watt counts.

Efficiency only comes into play when trying to maximize power output with limited roof space.

The temperature coefficient would suggest a mono panel is worth a small premium over a poly panel but in the order of less than 5%.

[phil.g00]

In which case is their any other offering that compares to the locally manufactured 320W panel from Artsolar at R1600 (Vat excl.) ?

[Antony]

18 hours ago, phil.g00 said:

In which case is their any other offering that compares to the locally manufactured 320W panel from Artsolar at R1600 (Vat excl.) ?

That is a good price, R5.75/W (Incl VAT) 

[phil.g00]

Slightly cheaper if you order a pallet too.