Guide to Choosing Solar Panels: Maximizing Power Output

· About Solar Panels

Introduction:

Solar technology has emerged as a monumental innovation in the renewable energy sector, offering significant solutions to reduce carbon emissions and enhance energy sustainability. Within solar systems, solar panels (also known as solar modules) play a pivotal role, directly determining the amount of energy produced. Therefore, selecting the right solar panel is a crucial step to ensure optimal system performance.

This article delves into each factor influencing the energy output of solar panels. By fully understanding these key elements, you will be better equipped to plan and design your solar system, catering to your energy needs while amplifying the efficiency of sustainable energy production.

Key Factors Influencing Module Power Generation:

  1. Solar module’s Operating Current and Temperature
  2. Solar Module’s Temperature Coefficient
  3. Solar Module’s Spectral Response
  4. Solar Module’s Low-Light Performance
  5. Solar Module’s Degradation
  6. Installation and Accessories
  7. External Environmental Factors

1. How does solar module’s operating current and operating temperature affect electricity generation?

When the operating current of a solar module is higher, it typically leads to an increase in the module's operating temperature. This is because the current's magnitude is related to the generation of heat within the module due to internal resistance, and higher currents result in more heat losses.

Heat losses cause an increase in the temperature of the solar module. At higher temperatures, the flow of electrons slows down, reducing voltage, and consequently, the efficiency of the solar module decreases.

To study the relationship between the electricity generation performance of different modules and their operating temperatures, JinkoSolar, in cooperation with TUV Nord, conducted an outdoor empirical project at the Yinchuan National Photovoltaic Experimental Base in February 2021. The operating temperatures of the ultra-high current modules (18A) were, on average, approximately 1.8°C higher than those of the 182 modules (13.5A), with maximum temperature differences of around 5°C. This is primarily because the excessive operating current of the modules leads to a significant increase in heat losses on the surface of the solar cells and soldering ribbons, contributing to the rise in the module's operating temperature. As widely known, the output power of PV modules decreases with an increase in temperature. For instance, in the case of PERC modules, when the module temperature exceeds the rated operating temperature, the power output decreases by approximately 0.35% for every degree Celsius increase in temperature. Considering a combination of factors, the empirical results show that the 182 modules achieve a single-watt electricity generation rate approximately 1.8% higher than that of the ultra-high current modules. Maysun's Twisun black frame modules offer the advantage of low current (9A) and high power, performing better in high-temperature conditions because the low current helps reduce operating temperatures, decrease heat losses, and improve module efficiency.

The following images illustrate the comparison of operating temperatures between the ultra-high current modules (18A) and the 182 modules (13.5A)

the working temperature of the modules on 4 th May
The workign temperature of the modules on 21st March
The 182 modules achieve a single-watt electricity generation rate approximately 1.8% higher than the ultra-high current modules.

The preliminary data from the empirical station shows that, on March 21st and May 4th, the operating temperatures of the ultra-high current modules (18A) and the 182 modules (13.5A) were measured. The operating temperatures of the ultra-high current modules were noticeably higher than those of the 182 modules. An increase in temperature leads to a reduction in electricity generation. The 182 modules achieve a single-watt electricity generation rate approximately 1.8% higher than the ultra-high current modules.

Suggestion:

Large current modules can lead to increased thermal losses, causing them to heat up more and, in turn, resulting in a more substantial drop in their output power. It's imperative to enhance the thermal loss control of solar panels. Implementing cooling measures, such as mounting heat dissipation plates beneath the modules or elevating the height of the solar panels from the ground for improved ventilation, can be beneficial.

Furthermore, when choosing inverters and solar panels, ensuring that the panel's Maximum Power Point Current (often abbreviated as MPP current) does not exceed the inverter's Maximum Power Point Tracking (or MPPT) maximum input current is crucial. This is because the inverter's MPPT circuit needs to effectively track the solar panel's MPP to maximize energy conversion efficiency. For instance, if an inverter's MPPT is rated at 12.5A and a panel's MPP current is at 13.5A, then the module would not be compatible with that inverter.

2. Why the Temperature Coefficient of Solar Modules Matters?

The temperature coefficient of solar modules is a vital performance parameter, indicating the performance variation of solar panels under different temperatures. The rated power of solar modules is determined under Standard Test Conditions (STC). If, during operation, the actual running temperature exceeds the rated working temperature, the output power will decrease. This is because the photovoltaic conversion efficiency of the module decreases as the temperature rises. For instance, if the power temperature coefficient is -0.34%/°C, for every 1°C rise above the rated working temperature, the module's output power will reduce by 0.34%.

Moreover, temperature fluctuations also impact the long-term stability and lifespan of solar modules. Elevated temperatures can lead to material fatigue within the modules, reducing their longevity. Typically, modules with a lower temperature coefficient are more likely to have a longer lifespan. In extreme cases, overheating of solar modules could pose safety risks, even leading to fires.