Energy storage is indeed a significant challenge for solar farms since solar power generation is intermittent. One common solution is using large-scale battery storage systems, which store excess energy produced during peak sunlight hours. These batteries can then discharge and supply electricity to the grid during periods of low sunlight or during nighttime. Additionally, some solar farms are integrated with other energy sources or the broader electricity grid, allowing for consistent power supply even when solar generation is low. Advances in battery technology, like lithium-ion and flow batteries, are enhancing the efficiency and capacity of these storage systems.

Yes, photovoltaic cells can function on cloudy days or during rainfall, albeit at reduced efficiency. While direct sunlight is most efficient for power generation, solar panels can still capture and convert diffused sunlight that penetrates through the clouds. However, the energy output on a cloudy day might be reduced by 10-25% (or more) compared to a sunny day, depending on the cloud cover's thickness and density. Rain, in itself, doesn't prevent PV cell operation. In fact, rain can help clean the surface of solar panels, potentially improving their efficiency by removing accumulated dust and debris.

Typically, solar panels have a lifespan of 25-30 years. However, this doesn't mean they stop working after this period; instead, their efficiency at converting sunlight to electricity decreases. Degradation rates vary, but most high-quality solar panels degrade at a rate of about 0.5% per year. By the end of their 25th year, they might still be operating at around 87-90% of their original capacity. Factors contributing to this degradation include UV exposure, temperature fluctuations, and physical wear and tear. Modern panels are designed with durability in mind, and ongoing research aims to reduce degradation rates even further.

The angle of incidence of sunlight on a solar panel can significantly impact its efficiency. When sunlight strikes the panel directly at a 90-degree angle, the energy transfer is most efficient. However, as the angle deviates from this optimum, the efficiency diminishes because the same amount of light gets spread over a larger area. Solar trackers address this issue by allowing panels to pivot and follow the Sun's path across the sky. This ensures that panels receive the maximum possible sunlight at an optimal angle throughout the day, thereby maximising energy capture and conversion.

The efficiency of photovoltaic cells can be limited by several factors. Firstly, some photons might not carry the appropriate energy to free electrons from their atomic bonds. These photons will either be reflected or pass through the cell without interaction. Secondly, thermalisation can decrease efficiency. When high-energy photons are absorbed, the excess energy not used in liberating an electron becomes heat. Lastly, inefficiencies can arise due to electrical losses like resistances in the material. Advancements are constantly being made to tackle these issues, such as using multi-junction cells, which use multiple layers to capture a broader spectrum of sunlight, or incorporating materials like perovskites which offer better efficiency potential.