Cell to module conversion loss
Dear All

can anybody tell me what is the standard cell to module conversion loss?i mean to say if one solar cell is giving 4 watt and i will make module of 60 cell then insted of giving 240 watt its giving 232 watt?
my question are
1)y it is happening?
2)what are the possible ways i can reduce it?
3)any new technologies that can be helful


waiting for your reply...

Individual solar cells are tested naked and at a standard temperature.
When they are put in a module there is a layer of glass over them.
The glass reflects a little light on the front surface and some on the back surface.
The front surface reflection can be lowered by using a coating.
The back surface reflection can be minimized by gluing the cell to the back surface.
Both the glass and the glue also absorb some light.
There are special glasses that absorb less light.
The old glues would start to turn milky after 10 to 20 years.
Also cells in modules run hotter at the same ambient temperature as the individual cells.
This also lowers efficiency.
This can be partially alleviated by circulating water behind the module.
The warm water can then be used to preheat water for hot water use.
In actual use, the light usually comes in at an angle, so there appears to be less of it and even more is reflected.

Dear Mark
thanks for your reply
can u pls tell what is the standard cell to module conversion loss?
What all are the steps i can take two reduce this loss at cell as well as module level

Cell to module losses are optical and electrical. Glass limits the transmission of light in the solar spectrum of 0.35 to 1.1. microns. Electrical loss - bus bar soldering, interconnect, resistance, bus bar to junction box connect etc. if the solar cell is producing 4W @ 0.5V, the current generation is 8Amps. If you have two bus bars they share equally, then you have I2R loss, if you have 3 bus bars, it will reduce the current carrying capacity. Not only I2R loss, but also FF loss.

There are lot of areas where one can improve the solar module efficiency

Besides above, there is solar cell mismatch issue as well, each cell would be different generate current out of it, but comprehensive current normally will lower than the max one. Someone did study the lay-up strings influence this.
Tell you a tip, after laminated, go baking for some time, you might find out power goes up little bit upto 2-3%, not by Isc, but FF recovering, that's from elec path annealing affect.
Not sure your role in developing team, but most jobs should be done in engineering steps.
Using patterned bin of cells could control your module at certain level.

There are 5 elements to cell to module (CTM) performance differences, they are 1. Optical changes (current goes up if the cell level ARC is correctly designed), 2. reflection from the air glass interface of the module glass (current goes down), 3. higher resistive losses in the module then in the ideal conditions of the cell tester( FF goes down), 4. cell to cell mismatch, not all cells are identical in the series string (FF goes down), and finally the biggest of all....5. The calibration of the two testers (cell and module). This final one generally swamps the others. In my experience, the CTM (module power/ cell count*ave cell power) is between 0.97 and 1.01, assuming no AR coated glass.

From my understanding, when a module states a power generation of 240W, it should generate that, and not less. Does somebody confirm this fact?
Regarding the ≈ 0% CTM losses of Day4 Tech, it should be mentioned that even Roth & Rau has recently implemented this technology in order to maximize cell efficiency to 19,3%.

it comes with +/- variation for sure, IEC is making a stnadrad requirement for this now. The fact is that not much manuf matching its said.

cell vs. module measurment tech is big topic, including specturm from light sources, setup and connection resisitances...my personal prefer, for cell I like to use effiency, but for module, like to use power rating.

Virginia, As the buying public has gotten more and more sophisticated module power rating have moved to -0 / +5% at the time of manufacturing. The customer must account for the initial LID (light induced degradation) that occurs with most CZ based modules and to a lesser degree with multicrystalline modules. That effect could be as much as -3%. Each manufacturer treats that differently, some by pretreating to minimize the effect, some by shipping over rated power, some by being silent. Jim