Losses in Solar PV Power Generation

Contents

• Solar Energy System Losses
• Loss from PV Module
  1. LID Loss
  2. PID Loss
  3. Module Quality Loss
  4. Module degradation Loss
  5. Mismatch Losses
  6. Thermal Loss
• Solar Meteorological Loss
  1. Irradiation Loss
  2. Reflection Loss
  3. Spectral Loss
  4. Spectral Loss
• Loss due to Site condition
  1. Shading loss
  2. Dust and dirt Loss
  3. Solar panel orientation Loss
• Inverter Loss
  1. Solar Inverter Losses
  2. Inverter Clipping Loss
• Other component Loss
  1. DC Cable Losses
  2. AC Cable Losses
• Loss due to Installation
  1. Connection Loss
  2. IAM loss
• Grid Loss
  1. System availability Loss
• Failures in Solar Asset Management
• Conclusion

LID Loss

Light Induced Degradation(LID) Loss and Light and Elevated Temperature Induced Degradation (LETID) Loss occurs when the PV modules are exposed for the very first time to the sun. The modules are made of silicon, which is doped with n-type or p-type boron. When the modules are exposed to the sunlight, oxygen impurities in silicon react with doped p-type boron or gallium.It mainly affects the performance of the module.

This can cause losses of 0.5-1.5% but only affects certain module types, making the choice of module an important factor in limiting losses.

According to the 2024 PV Module Reliability Scorecard, the median power loss for Light-Induced Degradation (LID) and Light and Elevated Temperature Induced Degradation (LETID) combined was 0.4%.

PID Loss

Moisture gets inside the modules which leads to leakage in the conductivity of the cells. Charges that should go to the inverter gets deposited on the aluminium frame. Gradually solar cells become inactive which leads to losses. Research shows that PID could reduce solar panel efficiency by as much as 30%! 

Research solar panel certifications like IEC and MNRE before buying panels. 

Module Quality Loss

Module Quality loss is also known as module rating loss or module nameplate rating loss. It accounts for the difference in the stated power of the module. Note that in the module datasheet the (+)tolerance and (-)tolerance is always mentioned.

Module degradation Loss

The PV module degradation leads to reduction in solar panel output over time. A good quality solar panel will have low degradation rates that won't affect the performance of your system too greatly.

Solar Panel Mismatch Losses, Array mismatch Loss

When two or more solar panels in an array produce differing amounts of energy, there is a mismatch between the solar modules.

Mismatch loss refers to losses caused by slight differences in the electrical characteristics of the installed modules. It occurs either due to different operating conditions or different internal characteristics of the cell. This results in a net decrease in power in the strings.

Thermal Loss

A solar cell loses 0.5% of its output for every 1 degree C above the STC-rated temperature of 25 degrees C, making this one of the largest losses in energy. This loss is due to an intrinsic feature of the solar cell construction.

Low radiation loss / Irradiation Loss

This shows the reduction in efficiency when the irradiance is decreased from the STC rating (Standard test Conditions) of 1000W/m2 to a low irradiance of 200W/m2. It is averaged out for practical reasons at 1.5 percent.

Reflection Loss

Spectral Loss

This system loss is about the output of different types of wavelengths that solar cells receive. Solar energy cells do not use all sun’s wavelengths. There are different frequencies, but the most common ones are 4% UV, 54% infrared, and 43% visible light. To enhance electrical output, manufacturers work to design panels so that they offer a generic, broad response.

Shading loss

Shading impacts directly solar energy panels’ performance. The shade will decrease the efficiency of the PV system because this interrupts sunlight from directly hitting the panels.

Dust loss, Soiling Loss/ Dust and dirt Loss

As the name suggests, soiling loss occurs due to accumulation of dust and dirt particles on the surface of the PV modules. The dust effect factor mainly depends upon the geographical location of your home.  It depends on cleaning frequency & the rainfall. Dust accounts for a total of 2% loss in solar power generation. This percentage may easily reach 6% or 7% for areas near industrial activity and lengthy, dusty seasons; this energy loss is not insignificant.

Tilt Angle Loss/ Solar panel orientation

The tilt angle is determined during the design stage and can be adjusted to reduce dust and dirt accumulation while taking into account other factors, such as the optimal angle for sunlight absorption and shading from adjacent rows.  

Solar Inverter Losses

Inverter loss is the DC to AC conversion, this loss occurs when the inverter converts DC power to AC power. This loss depends on Inverter efficiency which can be described as how well a solar inverter converts DC energy into AC energy.

Efficiency for the most popular type of inverter, the string inverter, is at 97%, which means that for every 100kWh produced, 3kWh are lost.

Temperature and load are two of the key variables impacting solar inverter efficiency. If the unit is positioned outdoors or inside, make sure it is well-ventilated and sheltered from the sun’s glare. The efficiency curve of inverters is similar to that of most devices with maximum efficiency occurring around the maximum working load. This is typically not a problem until the inverter load goes below 25 to 30 percent, but below this point, it drops sharply.

Inverter Clipping Loss

This loss occurs when the output from the direct solar panels (DC) at their maximum power output(or maximum power point) is greater than the amount of DC power the inverter can convert. The amount of energy production lost(or clipped) compared to what the system would have produced if it had not been limited by the inverter rating is called inverter clipping.

DC Cable Losses / Ohmic Wiring Loss

Ohmic losses represent the voltage drop across the circuit. According to Ohm's law, the voltage drop across a circuit is directly proportional to the current flowing in the circuit. The losses faced by the circuit due to this resistance are known as ohmic losses. It is directly proportional to the length of the wire and inversely proportional to the area of cross-section. Therefore size of the cable should be directly proportional to the current passing through it.

Losses in DC connections cannot be eliminated because whenever a current flows, energy is lost. The loss can only be reduced as much as feasible, and that is all we can do. Although, 2 percent is acceptable. Designers strive to keep DC cable losses to less than 1% of the peak power output of the entire solar panel system. 

Moreover, when current flows through the cables, their electrical resistance causes a voltage drop as well as power loss in the form of heating. The heating effect is a factor across connections and gets worse the higher the current.

AC Cable Losses

AC losses at the output of inverters all need to be kept to a minimum. Minimizing the voltage drop in cables is one approach to keep these losses under control. It is OK to have a drop voltage of less than 1%, and it should never go over 3%.

Connection Loss

Connection loss captures resistive losses across wiring connectors and diodes. This loss can be avoided as most solar panels contain bypass diodes. The bypass diodes are connected in parallel with solar panels. It creates a path for the current to flow around them in case the panels become faulty.

IAM loss 

Incident angle modifier loss occurs due to the tilt and orientation of the panels. The amount of solar radiation incident on a tilted module surface depends not only on the power contained in the sunlight, but also on the angle between the module and the sun.The power density will always be at its maximum when the PV module is perpendicular to the sun. Therefore it is always recommended to install the PV modules at an optimum tilt angle and in the northern region, the solar panels should always face south. 

System availability Loss

This loss generally takes place in ON-Grid and Hybrid solar systems. As the name suggests this loss occurs when there are grid outages, inverter shutdown or failure. Due to unavailability of the grid, the power doesn't get exported leading to loss of power.