Efficiency rating of solar panels - please confirm/deny

TrickyDicky101

Hi All

Am I correct in thinking if I have two modules (different manufacturers) and both are rated at 250W but Module 1 has 20% efficiency and module 2 has 10% efficiency (made up numbers to make the maths easier!) then:

1. Both modules will still only generate 250W at peak
2. There will be no practical difference between power generated for the same conditions, all other things being equal
3. The only likely difference between the two is that the 20% panel will be half the size of the 10% one

I am struggling to get my head round the module efficiency and have a pair of quotes where the difference is down to module efficiency but same (ish) peak output. I know the sizes of the panels are different.

Any advice/help very welcome.

Thanks

keith_r59

Solar panel efficiency explained:

http://us.sunpowercorp.com/blogs/blog/2010/07/09/solar-panel-efficiency-explained-an-interview-with-dr-richard-swanson-founder-president-and-chief-technical-officer-sunpower/

TrickyDicky101

That didn't answer the question I asked, unfortunately.

penrhyn

The panel is made up of a number of photoelectric cells, the more efficient the cells the less you need to produce a given output.
If the output power is a constant then as you state the more efficient panel will be smaller.

grahamc2003

TrickyDicky101 wrote: »

Hi All

Am I correct in thinking if I have two modules (different manufacturers) and both are rated at 250W but Module 1 has 20% efficiency and module 2 has 10% efficiency (made up numbers to make the maths easier!) then:

1. Both modules will still only generate 250W at peak
2. There will be no practical difference between power generated for the same conditions, all other things being equal
3. The only likely difference between the two is that the 20% panel will be half the size of the 10% one

I am struggling to get my head round the module efficiency and have a pair of quotes where the difference is down to module efficiency but same (ish) peak output. I know the sizes of the panels are different.

Any advice/help very welcome.

Thanks

I think your view is correct.

Say in bright summer conditions, the power of the sunlight when it hits your roof is 1kw over each square metre.

So if you have a 20% efficient panel 1mx1m, then you'd expect to generate 200w from it under the above assumptions.. A 10% efficient panel of the same size would generate 100w under those assumptions. For the 20% efficient panel to generate 100w would only require a size of 0.5sqm (e.g. 1mx0.5m), which answers your specific question.

TrickyDicky101

Thanks. Which means one probably shouldn't get too hung up on quoted panel efficiency when deciding between different quotations as it is the total array size (kWP) that is key.

Issues of shading/future expansion may be a consideration suggesting one over the other.

zeupater

Hi

As mentioned above, the efficiency is just the generation of power from the energy received on the panel surface at a given nominal level of irradiation. To compare panel performance in various conditions you would need to study the relative performance curves very carefully, however, the biggest difference between the performance of panels on the roof is the manufacturing tolerance of the actual pack you receive and this can vary considerably.

The quality of the glass is probably significant when comparing cheap & nasty panels with the decent makes as the angle of incidence makes a difference on the more reflective cheaper glass. There is a difference between the quality of the cells use in different panels, but this will be included in the efficiency and therefore the power rating of the panel for a given size.

I am particularly sceptical on many 'enhanced performance' claims on panel performance which are made by a number of manufactures which are pushed heavily by installers in order to enhance their own turnover, so always check the smallprint which justifies the claim .

HTH
Z