PV module power generation is influenced by orientation and tilt angle, which affect the amount of solar radiation received, and by solar radiation intensity itself

Wonderful discussion with SHri SKB Vali & Shri S. Simhachalam Sir during training.

PV module power generation is influenced by orientation and tilt angle, which affect the amount of solar radiation received, and by solar radiation intensity itself. Temperature significantly impacts voltage, while factors like wind speed, humidity, shading from objects or dust, and even panel cleanliness can reduce output by obstructing sunlight or increasing panel temperature. 

Environmental & Operational Factors

Solar Radiation (Irradiance): The primary factor; more direct sunlight means more power generation.

Temperature: High temperatures increase voltage but significantly reduce panel efficiency, impacting overall power output.

Shading: Any object that blocks sunlight, such as trees or buildings, will reduce power generation.

Dust & Cleanliness: Dust and other debris on the panel surface obstruct sunlight, reducing the energy absorbed by the PV cells.

Wind Speed: Wind can help to cool the PV panels, which can improve their efficiency and reduce temperature-related losses.

Humidity: While humidity doesn't directly block light, it can affect the efficiency and performance of the solar cells over time and can contribute to panel soiling. 

Panel Placement Factors

Orientation: The direction the panels face is crucial; in the Northern Hemisphere, panels facing south are generally most effective for maximum daily energy production.

Tilt Angle: The angle at which the panels are tilted relative to the horizontal impacts how directly the sun's rays strike the panel surface. The ideal tilt angle varies by latitude and season to maximize solar exposure. 

Details 

Solar radiation

The intensity and angle of solar radiation are the most critical factors for power generation. 

Intensity: A positive correlation exists between solar radiation intensity and PV power output. Higher intensity results in more power generated.

Angle of incidence: Maximum power is produced when sunlight strikes the panel perpendicularly (at a 90° angle). Any deviation from this angle reduces the amount of energy absorbed. 

Temperature

PV module efficiency decreases as its operating temperature increases. 

Mechanism: Higher temperatures increase the recombination rate of electrons and holes within the semiconductor material and decrease the open-circuit voltage.

Temperature coefficient: This negative relationship is quantified by a panel's power temperature coefficient, which indicates the percentage decrease in power for every 1°C increase above 25°C. For crystalline silicon, this is typically between -0.4% and -0.5% per °C.

Mitigation: Cooling systems or proper air circulation behind panels can help mitigate this effect. 

Orientation and tilt angle

Properly orienting and tilting a PV module is essential for maximizing its power output by capturing the most sunlight throughout the day and year. 

Orientation (Azimuth): In the Northern Hemisphere, panels should face true south (0° azimuth). In the Southern Hemisphere, they should face true north. Orientations toward the east or west can still be effective but will shift peak energy production to the morning or afternoon, respectively.

Tilt angle: The optimal tilt angle for year-round production is generally equal to the installation site's latitude.

Seasonal adjustments: Adjusting the tilt angle seasonally can maximize output. For instance, in the Northern Hemisphere, a steeper angle is better in winter when the sun is lower, while a shallower angle is best in summer.

Tracking systems: Solar trackers can increase energy production by continually adjusting the panel's orientation and tilt to follow the sun's path. A dual-axis tracker can produce up to 30% more energy than a fixed system. 

Shading

The blocking of sunlight from reaching a PV panel, even partially, can cause a disproportionate drop in power output. 

Effect: Since cells are wired in a series, a shaded cell can significantly restrict the flow of current for the entire panel or string, acting like a resistor and creating "hot spots".

Causes: Common sources include trees, buildings, dust, and debris.

Mitigation: Bypass diodes and microinverters can be used to isolate shaded panels or cells, allowing the rest of the array to produce power. 

Humidity

High humidity can affect panel performance in several ways:

Air moisture: Water vapor in the air can reflect, refract, and scatter sunlight, reducing the amount of radiation reaching the panels.

Combined effect: In dusty regions, high humidity can cause dust particles to stick to the panel surface, forming a dense layer of mud that further blocks sunlight.

Degradation: Over the long term, humidity can penetrate the panel's casing and cause corrosion and moisture-induced degradation. 

Wind speed

Wind has a mixed but generally beneficial effect on PV module performance. 

Cooling effect: Wind blowing over the panels provides a free cooling mechanism through convection. This lowers the module temperature, which can increase efficiency and power output, especially on sunny, hot days.

Dust and soiling: Wind can also remove loose dust and debris from the panel surface. However, light breezes can sometimes deposit dust instead of removing it, and wind can carry airborne particles that scatter sunlight. 

Other factors

Dust and soiling: The accumulation of dust and other particulates on the panel surface is a major factor, with power losses potentially reaching 60% in desert regions.

Deterioration: Modules experience a gradual decrease in power output over their lifetime, known as degradation.

Material and equipment: The type of PV material used, the efficiency of the inverter, and the quality of wiring can also impact overall power generation.