Efficiency of Solar Cells

Introduction

Solar energy is becoming more reliable and is quickly becoming one of the main sources of renewable energy widely used in residential and industrial setups.The efficiency of a solar cell ensures the maximum utilization of the installed hardware. Efficiency of a solar cell is the ratio of solar cell output to input energy from the sun rays. Efficiency is an indicator when we compare the performance of one solar cell to another. There are many factors that affect the efficiency of solar cells , from the spectrum and intensity of the incident sunlight and the ambient temperature around solar cells.

Definition

The efficiency of solar cells is the percentage of incident power which the solar cell can convert to electricity (1): 

P_max=V_OCI_SCFF    n= (V_OCI_SCFF)/ P_in 

Where: V_oc is defined as open-circuit voltage; I_sc is defined as short-circuit current; FF is defined as the fill factor and n is defined as the efficiency.

Solar panel efficiency reflects the amount of the incoming solar energy that the solar cell can convert into electrical power. The usual efficiency range of solar cells 11-15%.

Factors affecting efficiency of solar cells

1. Solar Panel Type
   The material used in manufacturing the solar panel can is one of the main factors affecting the efficiency as explained below:
   • The high purity level of silicone in monocrystalline solar cells makes them the most efficient solar panel type
   • Solar cells made from polycrystalline silicon are the closest efficiency after monocrystalline solar cells
   • Thin-film solar panels have lower efficiency, but also cost less. Also, thin-film solar panels take up a lot more space than mono- or polycrystalline solar panels
     
     
2. Shade
   Shade and percentage of shaded cells directly affect solar cell efficiency
   
   
3. Orientation
   Solar cell position and orientation directly affects the solar cell efficiency to maximize the input of sunlight. Solar trackers and charge controllers to ensure maximum power output with highest efficiency for the module.
   
   
4. Temperature
   As the temperatures increase, the efficiency of solar cells usually decreases, so proper natural ventilation ensures higher ventilation is provided
   
   
5. Degradation over the lifetime
   The efficiency of solar panels degrades over its lifetime. Generally, the power output drops by 0.5% yearly. Manufacturers provide a warranty that guarantees minimum 80% power output after 25 years.
   
   
6. Space
   Solar panels with higher efficiency requires less space than lower efficiency solar panels. So even if higher in price, higher efficiency solar panels are more space efficient and provide higher conversion rates.

Solar cell efficiency is critical in determining the type of solar panels to purchase and also in the design and installation of solar systems and ensures highest output is achieved by the solar module. Clearly, proper maintenance and extra devices like charge controller can ensure proper tracking and higher conversion rates.