Solar Afloat #4 Panel configuration/styles

Highland_Fling

Looking at these two 100W panels

PANEL A http://www.solarblvd.com/Solar-Panels-&-Systems-Individual-Solar-Panels-100---170-Watt-%2812%29/c1_25_42/p854/Sunwize-SW100C-100W-12V-Solar-Module/product_info.html

Each module consists
of 48 solar cells connected in series providing maximum charging power.

Dual bypass diodes contained within the junction box insure reliable operation.

Does dual bypass diodes mean there are three parallel/series circuits (Vmp) = 23V which is a function of there being 48 cells?

PANEL B http://www.solarblvd.com/Solar-Panels-&-Systems-Individual-Solar-Panels-100---170-Watt-%2812%29/c1_25_42/p1394/Solar-Cynergy-100-Watt-12-Volt-Solar-Panel/product_info.html

which has 36 cells in a series (4 x 9)

which i assume means there are four parallel/series circuits the (Vmp) = 17.2V which is a function of the number of cells (36) ?


Now if i am correct with the number of individual circuits does this mean that panle A will suffer 'more' from shading issues than panel B?

BB.

Re: Solar Afloat #4 Panel configuration/styles

The short answer is "It depends"...

Shading is bad for solar panels and shading tends to be random depending on mounting and what is causing the shading.

If you have specific shading issues... Say the bottom edge of a panel is shaded by a pipe during the mornings/evenings--then if the panel is laid out so that the bottom 1/2 or 1/4 is one series string then the other 1/3 strings will not be affected so that the panel will output full voltage but on string less current.

If the shading is from a tree, wire, line, etc. across random parts of the panel face and/or cover all strings--then the whole panel will be equally affected no matter how many bypass diodes/strings are in the panel--it really won't matter and the panel output voltage will collapse.

Just a couple power lines across a large Grid Tied Array can easily cause a 50% fall of in production until the shade moves off the array.

With battery systems--the solar panel (or array) Vmp must be a couple volts above the battery voltage for charging current to flow.

If you have 3x Vmp=17v panels in parallel and drop one panel voltage by 2 volts or more, it will drop out of supplying any charging voltage pretty quickly.

If you have 3x Vmp=17v panels in series (behind a MPPT charge controller) charging a 12 volt batty bank... Then a minor loss of voltage on one panel does not take the whole panel down as the rest of the cells are still supplying voltage/current too and Vmp shaded of the Array is still >> Vbatt-charging.

The end result is that you may gather more energy from 3 panels in series behind a MPPT controller than 3 panels in parallel behind a PWM or MPPT controller if you have shading issues. However--any way you cut it--shading is bad news for a Solar PV array.

-Bill

niel

Re: Solar Afloat #4 Panel configuration/styles

i hope you are not misinterpreting the number of columns or rows to mean that each of them contains a bypass diode. they do not specify that the cynergy model contains any bypass diodes at all. now the cells are all in series and the bypass diodes just goes in parallel across half of the cells in the sw series pvs as they said there are 2 bypass diodes. if it would've said 1 bypass diode it would've gone across the output of the entire pv and 3 would be in 3rds as it would go across 1/3 of the cells and for 4 then 4ths as it's across 1/4th of the cells and so on.

Highland_Fling

Re: Solar Afloat #4 Panel configuration/styles

BB. wrote: »

The short answer is "It depends"...

Shading is bad for solar panels and shading tends to be random depending on mounting and what is causing the shading.

If you have specific shading issues... Say the bottom edge of a panel is shaded by a pipe during the mornings/evenings--then if the panel is laid out so that the bottom 1/2 or 1/4 is one series string then the other 1/3 strings will not be affected so that the panel will output full voltage but on string less current.

If the shading is from a tree, wire, line, etc. across random parts of the panel face and/or cover all strings--then the whole panel will be equally affected no matter how many bypass diodes/strings are in the panel--it really won't matter and the panel output voltage will collapse.

Just a couple power lines across a large Grid Tied Array can easily cause a 50% fall of in production until the shade moves off the array.

With battery systems--the solar panel (or array) Vmp must be a couple volts above the battery voltage for charging current to flow.

If you have 3x Vmp=17v panels in parallel and drop one panel voltage by 2 volts or more, it will drop out of supplying any charging voltage pretty quickly.

If you have 3x Vmp=17v panels in series (behind a MPPT charge controller) charging a 12 volt batty bank... Then a minor loss of voltage on one panel does not take the whole panel down as the rest of the cells are still supplying voltage/current too and Vmp shaded of the Array is still >> Vbatt-charging.

The end result is that you may gather more energy from 3 panels in series behind a MPPT controller than 3 panels in parallel behind a PWM or MPPT controller if you have shading issues. However--any way you cut it--shading is bad news for a Solar PV array.

-Bill

Well one thing i will be doing is putting the panels in series if only to make the wiring smaller and easier

niel wrote: »

i hope you are not misinterpreting the number of columns or rows to mean that each of them contains a bypass diode. they do not specify that the cynergy model contains any bypass diodes at all. now the cells are all in series and the bypass diodes just goes in parallel across half of the cells in the sw series pvs as they said there are 2 bypass diodes. if it would've said 1 bypass diode it would've gone across the output of the entire pv and 3 would be in 3rds as it would go across 1/3 of the cells and for 4 then 4ths as it's across 1/4th of the cells and so on.

He He i was - silly me assumed the visual cell layout was reflected in the number of circuits and bypass diodes - learning fast

thanks

David