Solar is at the forefront of renewable energy, but did you know that rooftop solar panels can only produce up to 25% of their maximum electrical potential, on average? The percentage of solar energy produced compared to a system's maximum potential output is known as its capacity factor. Until we put solar panels in space, where solar radiation is available 24/7, solar energy developers and consumers must work within the capacity factor limitations of photovoltaics.
So, why don’t solar panels have an 100% capacity factor?? The main reason, of course, is that sunlight just isn’t available all day long. Even when sunlight is available, cloud coverage and panel placement affect how much UV actually reaches the panels. Technical factors also contribute to inefficiency. Electrical energy comes from a process of converting direct current (DC) electricity from solar panels into alternating current (AC) electricity. AC/DC conversions then create energy for use by electrical grids and household appliances. However, the conversion processes involves the use of an inverter and results in an inevitable loss of heat, and therefore energy. The amount of energy lost depends on the efficiency of the inverter and can range from 3-10% of the total energy produced. Finally, build up of dust or particulate matter on glass contribute to reduced capacity factors. Poor panel maintenance results in layers of grime that reduce UV penetration to panels.
This is all to say that understanding capacity factor is important because it plays a crucial role in determining the size of a photovoltaic system. For instance, if a consumer desires 5 kW of solar energy to power their building and resides in a sunny state where solar panels have an average capacity factor of 20%, a minimum 25 kW system would be required to meet their needs. Due to their relatively low capacity factors, particularly influenced by location, solar panels are better suited to supplement electricity on utility scales rather than serve as the sole source of power throughout the day.
Capacity factor limitations necessitates the exploration of optimization strategies to make the most of the power generated by solar panels. One heavily researched solution involves the implementation of battery systems which store solar energy generated during the day for use during night or other periods of low solar generation.
While battery technology continues to develop, solar forecasting also plays a vital role in maximizing solar power use. Solar forecasting utilizes weather and solar penetration data to evaluate when solar power generation is at its highest. Solar energy availability peaks during the day and disappears at night, resulting in a characteristic "duck curve."
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Incorporating day-ahead forecasting into the grid enables more accurate switching between solar and electrical energy sources. Research indicates that solar power forecasting reduces electricity generation costs, enhances solar penetration in the grid, and decreases reliance on fossil-fueled generators.
As the solar energy industry continues to evolve, understanding and navigating the capacity factor limits of photovoltaics are essential for effective system design and optimal power generation. While solar panels may have inherent limitations, technological advancements in areas such as battery storage and solar forecasting help overcome these challenges and improve the efficiency and reliability of solar energy.
Our goal at Vert is to help support decarbonization efforts. While capacity factors are a limitation to rooftop PV and simple solar panels, they also emphasize the importance of flexibility and creativity in the pursuit of a carbon free future. The path to clean energy reliance may be complicated, but an understanding of the challenges we face and their potential solutions are essential to a fossil-fuel free world. Vert is there to help companies understand what energy upgrades they can get with help from banks, and how those upgrades will benefit your business and our environment.