Can we depend on solar power throughout the year?
In today’s world, more people have started focusing on sustainable development. Generation of electricity through solar power plants has become an area of growing interest. However, there are many misconceptions surrounding this topic. In this article, we’ll be addressing one such belief using data, facts, and examples.
One of the most common misconceptions is that solar energy systems are better at generating electricity during the summer.
But, is that really true?
To answer that, let me take you through some factors that affect the solar energy system’s ability to generate electricity.
Did you know that the optimal solar cell temperature lies in the range of 43–47°C for most modules? At this temperature, the modules work at their rated efficiency. When the temperature increases beyond this value, the output of the module decreases, and vice versa. This implies that the output of the module is defined by a negative temperature coefficient.
If solar modules are mounted directly on the roof, with no air gaps, the cell temperature increases. This is because the exchange of heat between the cell and its surroundings takes place primarily from the front side of the module.
Wind speed is one of the most underrated factors, despite it playing a fundamental role in determining the module’s temperature. We know that there is a constant exchange of heat taking place between the photovoltaic module and its surroundings. Normally, the difference between the cell and ambient temperature lies between 20–25°C. However, on a windy day, we can observe the difference tending towards zero.
This means that windy days improve the efficiency of solar power generation.
Solar irradiance is the amount of solar energy that we receive. Ideally, the value of irradiance is 1050 watts per square meter. In real-world conditions, however, we receive around 800 watts per square meter. Several factors are responsible for this loss of energy; such as the presence of clouds, pollutants in the air, and anything that hinders transmission of light. Upon analysis, I found that solar irradiance has a strong linear relationship with the PV module’s output.
Higher solar irradiance = better solar power generation.
The cells in a module are usually connected in series. When there is shadow falling on a region of the module, the cells in that region generate less energy. This, in turn, affects the energy generated by all the modules in the system until the shadow disappears. Therefore, while designing and installing the system, possible shading from objects nearby should be taken into consideration.
Now, let’s say we have optimised all the factors and installed the system, but we fail to maintain the modules. What happens then? Dust settles (soiling) on top. This hinders the generation of energy due to the absorption and reflection of heat by the dust particles. Therefore, periodic cleaning of the modules will prevent losses from soiling.
Let’s do a simulation, then.
All these factors are dependent on the altitude and the season. Here, I have considered 3 seasons of the year — summer, monsoon and winter, across 3 places — Jaisalmer, Bangalore and Srinagar; located in India. Upon simulation using the various factors, the following results were obtained for a roof-mounted 2-kilowatt solar power system.
From the data, it is clear that solar power systems are able to generate electricity throughout the year in India. This contradicts the assumption that it does not do so during winters or monsoons. It is true, however, that the same amount of energy is not generated every day; as that is dependent on a number of factors we have discussed here.
Location: Bangalore, India.
We can see that Bangalore has a healthy year-around efficiency of solar power generation. This is mainly due to the city’s advantageous geographic location. In summer, Jaisalmer has an advantage in terms of energy generation, whereas Srinagar has an advantage during monsoon, while Bangalore during winter.
Solar power systems, unlike beach-wear, is a sensible choice throughout the year.
Written by Sriraksha Murali, Engineering-Operations at Solarify
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