Efficiency of PV modules vs cloud cover

On Sunday, 8 October 2023, a record was set in the energy market. In the history of Poland, this day can recorded as a breakthrough day. On that day, the electricity produced by Renewable Energy Sources would have covered 107% of Poland’s power needs if it were not for restrictions on PV power generation caused by a lack of off-take.

This success was influenced by 3 aspects: high generation from wind turbines, significant production from solar panels at a planned level of nearly 9 GW, and reduced power demand resulting from the day of the week (non-commercial Sunday).

Despite such successes, there is still a perception in Poland that our country is not the best place to produce energy from the sun and that such installations make more sense in hot, sunny climates.  At this point, it is worth considering what the production of energy from a PV installation in our country involves, and what are the main advantages of such an investment.

 

RES covered 97% of Poland’s demand. Five hours of negative electricity prices – WysokieNapiecie.pl

How and what aspects should you pay attention to when deciding to implement a photovoltaic project?

What does the efficiency of a PV installation depend on? This is one of the questions that every investor should ask themselves before deciding on PV Installations.

PV module lifetime and location are two key factors affecting the performance of the overall system.
This, in turn, translates into energy production and thus profits.  When we speak about location, we mean placing the modules in relation to the sun, but also the surroundings, which affects overshadowing. We will try to address both aspects in this text.

It doesn’t matter whether we are talking about a micro-installation or a farm – the owner of each of them wants the photovoltaic system to work as long and efficiently as possible. Fortunately, solar PV panels work for decades and require virtually no maintenance.

This is supported by the fact that the oldest PV panel dates back to the 1950s and is still in operation. Researchers at Bell Laboratories in the United States have created a silicon panel with an efficiency of about 6%, paving the way for further research and applications.

Currently, the modules achieve efficiencies ranging from 19% to as high as 23.23%.
Earlier this year, the 23% of PV module efficiency limit was finally broken.

What is the efficiency of a photovoltaic module?

The mentioned efficiency is otherwise known as module performance. This parameter tells us how much of the sun’s rays falling on the cell will be converted into electricity, under standard STC conditions (assuming no wind, module temperature of 25°C, radiation of 1000 W/m2).

Several factors affect the efficiency of photovoltaic panels, but the most important are the type and properties of the material from which the PV cells are made.

Monocrystalline modules currently lead the market with an efficiency of 22.6%, followed by polycrystalline panels, where efficiency reaches 18%. The above values, regarding the efficiency of solar PV, are indicative data. Every year, manufacturers of photovoltaic components push the limits of their efficiency. Solar panel technology is constantly improving, and consequently, their productivity is also increasing.

Unfortunately, it is important to realise that every PV module is subject to degradation related to its operating time. Fortunately, our country’s weather conditions are kind to them and there are no extreme weather changes. A study on the efficiency loss of photovoltaic panels was conducted on more than 2,000 solar panels and found that on average such a panel loses 0.5% of its efficiency per year.

What is the actual lifetime of PV panels?

We will probably be able to answer this question in a few years, as solar PV are still a fairly new technology. One of the indicators we can take into account is the ever-increasing number of years of product warranty and yields declared by panel manufacturers.

At the moment in the market, the declared length of the product warranty is 12 -15 years, but it is estimated that it will realistically reach at least 30 years of service. The operating time of PV panels is one of their biggest advantages. We can assume that the electricity produced from the plant currently under construction will be used by our grandchildren.

That is why it is so important to select the best solutions and to analyse every possible location of such a project on the land or roofs of the properties available to the Investor.

How does the overshadowing of photovoltaic panels affect the efficiency of the installation?

One of the main aspects of optimal energy production from a photovoltaic installation that we need to pay attention to is overshadowing, which can significantly reduce the production of electricity from PV modules. When a shadow falls on the panels, the amount of sunlight reaching them is reduced, leading to a decrease in the efficiency of the entire system.

To minimise the impact of overshadowing, proper placement of PV panels is crucial. We need to pay special attention to the correct inclination angle, orientation towards the sun and the distance between the rows of modules. This allows maximum use of the available sunlight for most of the day.

In addition, some manufacturers have developed technology that further offsets the effects of overshadowing on the energy output of installed PV panels.

In most cases, photovoltaic modules are mounted horizontally. Here’s a look at the implications of linear overshadowing for standard panels compared to CAT® modules.

Standard module:

A standard PV module under even slight shading loses as much as 33% of its power.

When the shadow falls on the longer edge of the module, one of the three cell strips is disabled, similar to spot overshadowing.

CAT^® module:

When CAT® modules are overshadowed, the decrease in power is proportional to the shaded area. If only half of the cells in the first row are overshadowed, the other half continue to operate at 92% of rated power.

Linear overshadowing in vertical orientation

If the first row is completely overshadowed (the panels are arranged vertically), the efficiency of the CAT® module drops by only 17%, which is a much smaller efficiency loss compared to 33% when using traditional modules.

Standard module:

When the shadow falls on the lower (short) edge of the traditional module, the entire panel is disabled, as the shadow affects all 3 zones simultaneously.

CAT^® module:

With special parallel and serial connections, the CAT^® module maintains performance even when shaded, achieving only 33% power loss. This means that 67% of the power is still produced, which is much better than 0% for traditional panels.

In conclusion, the effect of overshadowing on the power generation potential of PV modules is significant. The examples above illustrate how the design and special solutions in CAT^® modules can significantly increase the reliability of an energy source over its lifetime.

 

Advice at every stage of the investment

If you plan to install photovoltaic panels, keep in mind that choosing the right technology can have a big impact on minimising the effects of overshadowing and, consequently, the profitability of your project.

Eneria as an experienced supplier of photovoltaic panels helps in the selection of the appropriate technology that will be most effective in the given location and conditions, as well as carries out a comprehensive installation and provides maintenance of the equipment during its use.

In addition, it is worth using our solutions in the field of renewable energy including solar PV, because our experts have all the competence and knowledge to help each of our customers minimise energy losses, ensuring maximum efficiency and profitability of the investment over time.

 

Written by: Agnieszka Płocica-Wiśniewska
Photovoltaic Expert