What module parameter indicates its low light efficiency?
I don’t think that there is anything on a module data sheet that specifies this as far as I know.
I think the only way to know is from the technology being used. It’s a good question @BrownBird, I hope someone else has more info.
Low light efficiency seems to be more of a marketing term. The amount of energy produced by a solar panel is directly proportional to the amount of solar irradiance measured in W/m2 (sunlight). I don’t know of any actual physics or properties of a solar cell which would make them more efficient under low light conditions.
Lower light W/m2 = lower power ouput. It’s very linear for all solar cells.
1 Like
Interesting graph, it seems 37-39 volts achieves optimum power output.
1 Like
Did a bit more research on academic sites. It comes down to the PV module components, “The low light behaviour of a solar panel is mainly dependent on the shunt resistance and series resistance of the cells”. All of which seems to relate to quality & cost of circuits, resistors, individual cell material used in a PV module and consistency/quality of material used by manufacturer. Apparently standardised testing is conducted in laboratories with software analysis of PV Module performance.
Thus it seems, cheap PV modules are unlikely to be low light power producers, mid range ones are anyones guess and expensive ones might produce 10% more power over their life. Based in techniques and materials used today to manufacture PV modules.
I thought some thin film modules used to perform better in low light (shaded) conditions, compared to mono silicon?
Yes @Marty, I think the now mostly obsolete thin-film modules performed quite well in low light conditions but since their overall efficiency was very low (approx 10 to 12%) then they still didn’t come close monocrystalline modules with efficiencies of 15 to 17% at the time.
From what I know the main reason they were popular back in 2010 and earlier was due to the low price compared to monocrystalline panels.
@BrownBird, Interesting insight but considering almost all the major manufactures now use the same mono PERC P-type cells in a half-cut configuration there is really minimal difference - I would say 1-2% at most. I have 8 different panels with module-level Tigo optimisers and monitoring and I can see virtually no difference between the same size panels under cloudy conditions.
The thickness of [solar]( cells is less than four strands of human hair. Since each cell is small, it can only typically create 1 or 2 watts of energy. They are linked together like chains to make large blocks called panels or modules so that the power output can be boosted.
The amount of sunlight the panel gets and the location are the power output determiners.
If there’s a shade such as clouds or anything that covers a portion of the whole module, it can lessen the generated power of the panels. Since there is a change in the sun’s position, there’s also less output during the summer and spring compared to fall and winter.
The low light performance of solar modules is of high importance for operating cost effective solar power systems, especially during winter season in Europe.
The short answer to the original question is no. Solar Panels are tested under STC = Standard Test Conditions, which are 1,000 W/m^2 (1 sun), 25° C, and AM1.5 (atmospheric model) sunlight. Using STC one obtains Vmpp (voltage at maximum power point), Impp (current at maximum power point). Multiple Vmpp X Impp and one obtain the rated output power. Input photons (solar irradiance) free electron and within limits, the output current is directly proportional to the input sunlight. (Look at the graph provided by Svarky and compare 800 W/m^2 to 400 W/m^2.). At input irradiance lower than about 100 W/m^2 the internal losses become more important where for example shunt resistance (Rsh) can greatly impact conversion efficiency.
Hi Svarky,
As a matter of interest, are all 8 panels Tilted &/or Fixed to the Same direction ?
@TheRaptor Yes, the panels are all fixed and facing the same direction. I haven’t actually checked the data for a while so it will be interesting to see if there is a more noticeable difference. Some panels may have slightly degraded more than others? I will have to post the results
Yes do share results, that are helpful.
Yes, @BrownBird Low light efficiency seems to be more of a marketing term. The amount of energy produced by a solar panel is directly proportional to the amount of solar irradiance measured in W/m2 (sunlight).
Lower light W/m2 = lower power ouput. It’s very linear for all solar cells
And Solar panel efficiency is measured as a percentage (ranging between 15% to 22%) that determines how much energy a solar panel is able to produce over the course of a year. This is also referred to as solar panel performance.
Certain factors affect solar panel efficiency.
- Higher for monocrystalline solar panels
- Lower for polycrystalline and thin film solar panels
- Measured in watts per meter
Solar panel efficiency ratings are currently between 15% to a maximum of 22%. The higher the efficiency rating, the more energy your panels are going to be able to produce.
Here are some of the factors that affect solar panel efficiency.
- The location of your solar panels
- The tilt angle of your solar panels
- The weather conditions in your area
- How well you maintain your solar panels
- The build quality of your solar panels
- The number of peak daylight hours in your area
It is vital to go for the most efficient panels possible when you decide to go solar…
Thanks,
Matt
1 Like
Direct recombination, in which light-generated electrons and holes encounter each other, recombine, and emit a photon, reverses the process from which electricity is generated in a solar cell. It is one of the fundamental factors that limits efficiency.
When it comes to low-light conditions, the efficiency of solar panels in generating electricity can decrease. In situations where sunlight is limited, such as on cloudy days 
or during early morning or late evening hours, solar panels may not produce as much electricity as they do under direct sunlight 
However, advancements in solar technology have led to the development of panels that are more efficient in low-light conditions, allowing solar power systems to still generate some electricity even when sunlight is not optimal.
The concept of “low light efficiency” often touted in marketing lacks a specific module parameter to quantify it. Solar panel performance fundamentally hinges on solar irradiance, measured in watts per square meter (W/m²) of sunlight received. No inherent physics or properties favor solar cells to be more efficient under low light conditions. Instead, diminished light intensity directly correlates with reduced power output, a linear trend across all solar cells. Despite marketing claims, there exists no distinct parameter indicating heightened efficiency in low light scenarios.
1 Like
Absolutely, you’re spot on. The notion of “low light efficiency” often promoted in solar panel marketing can be a bit misleading. At the core of solar panel performance lies solar irradiance, which is essentially the amount of sunlight they receive per square meter (W/m²). When light intensity decreases, so does the power output of the panels—it’s a pretty straightforward cause-and-effect relationship.
There’s no special physics or properties that give solar cells an edge in low light conditions. In fact, across the board, reduced light intensity leads to reduced power output, following a linear trend. Despite what some marketing materials might suggest, there isn’t a specific parameter that indicates solar panels perform notably better in low light scenarios.
It’s important for consumers to be aware of these nuances and not be swayed by misleading claims. By understanding the fundamentals of solar panel performance, we can make more informed decisions when it comes to harnessing solar energy for our homes and businesses.