Understanding solar radiation and its variation between summer and winter is essential for assessing its impact on the Earth's climate and the efficiency of energy systems, especially solar panels. Each year, the seasons bring with them different levels of light, solar intensity, and temperatures, which directly impact the amount of energy received and utilized, both in terms of climate and in terms of domestic and business energy consumption.
The impact of these variations goes beyond electricity production figures: they affect the thermal balance of the atmosphere, water cycles, agriculture, and human health. Furthermore, understanding how solar radiation behaves in each season allows us to optimize photovoltaic installations, adopt better sun protection habits, and anticipate energy and climate changes.
Why does solar radiation vary throughout the year?
Solar radiation reaching the Earth's surface does not remain constant over time, but fluctuates depending on the season and the planet's position. This variability is mainly due to the tilt of the earth's axis with respect to the Earth's orbit around the Sun. When the Northern Hemisphere is tilted toward the Sun (around June), it receives more direct sunlight for more hours, resulting in summer. During winter, however, the tilt is opposite, and the sun appears lower on the horizon, resulting in fewer hours of daylight and weaker solar radiation.
It's not that the planet is much closer or farther from the Sun in summer or winter., as is sometimes thought, but it is the orientation of the sun's rays that changes, thus affecting the intensity and duration of heatstrokeThis phenomenon explains the differences in temperature, light, and heat at different times of the year.
Characteristics of solar radiation in summer and winter
La solar radiation in summer It is usually more intense, with the sun's rays impacting perpendicularly and directly on the surface. This translates into more hours of daylight, higher temperatures and greater total radiation received per square meter. winter, the sun's rays fall at a more oblique angle, pass through more of the atmosphere and generate less heat and energy, coinciding with shorter days.
Furthermore, the sun path varies, being much lower on the winter horizon, which influences the duration of sunlight and in the amount of radiation absorbed by the Earth's surfaceThe result is a marked difference between summer and winter in terms of radiation and temperatures.
Factors affecting solar radiation and its use
- Daylight hours: In summer, days can last more than 15 hours, while in winter they can be as short as 8-10 hours, depending on the latitude.
- Inclination of the sun's rays: The perpendicularity of the rays in summer favors greater energy absorption, while the inclination in winter reduces intensity.
- Weather conditions: The presence of clouds, fog, rain or snow can significantly reduce direct radiation and promote light diffusion, affecting the energy received.
- Environmental temperature: Although it seems contradictory, Photovoltaic solar panels work more efficiently at low temperatures, since excess heat can reduce the performance of semiconductor materials.
- Geographic location: Latitudes closer to the equator receive greater annual radiation, but altitude and local climate also play a role.
Impact on the efficiency and energy performance of solar panels
It is a myth that solar panels only work well in summer.. In reality, its functioning depends on the solar radiation received and not from ambient heat. Photovoltaic modules can produce energy even in the coldest months, as long as sunlight is present, although total production decreases due to the shorter solar day.
En summer, the greater intensity and duration of radiation facilitates a higher energy production, although high temperatures can reduce efficiency somewhat: for every degree the panel exceeds 25°C, its performance can be reduced by up to 0,44%. However, the long days compensate for this loss.
On the contrary, in winterAlthough there are fewer hours of daylight and more chances of cloudiness, the low temperature favors the solar modules to work with a greater efficiency per unit of light captured. Even with less daily sunlight, the available energy is better utilized.
Actual energy production data: seasonal comparison
To illustrate these differences, real data from photovoltaic installations such as the one recorded in Almería can be analyzed, where a 5,20 kWp (kilowatt peak) system showed the following annual generation figures during the period from December 2022 to November 2023:
| MES | PRODUCTION (kWh) |
|---|---|
| December 2022 | 425,13 |
| January 2023 | 581,24 |
| February 2023 | 512,33 |
| March 2023 | 865,90 |
| April 2023 | 905,34 |
| May 2023 | 791,91 |
| June 2023 | 856,43 |
| July 2023 | 835,15 |
| August 2023 | 804,55 |
| September 2023 | 672,76 |
| October 2023 | 648,15 |
| November 2023 | 506,99 |
As can be seen, the Energy production increases significantly from March to August, coinciding with spring and summer, while the winter months show significantly lower figures.
| STATION | PRODUCTION (kWh) |
|---|---|
| Spring | 2.563,15 |
| Summer | 2.496,13 |
| Fall | 1.827,90 |
| Winter | 1.518,70 |
It is interesting to note that although summer and spring lead in energy generation, The efficiency of the panels can be higher in the cold months, since they do not suffer thermal losses and have more stable conditions for electronic materials.
Performance and efficiency of solar panels in winter
Contrary to what many may think, winter is not synonymous with low solar production or inefficiency.. Although there are fewer hours of sunshine and greater presence of clouds or fog, photovoltaic panels are designed to take advantage of both the direct and diffuse light, generating electricity even on cloudy days.
In fact, low temperatures can be an ally: The semiconductor materials in solar panels work best in cold weather., allowing for more efficient conversion of sunlight into electricity. Excessive heat, on the other hand, can degrade the modules' performance and reduce their lifespan.
In snowy conditions, if the panels are clean and clear, they can even receive reflected light, slightly increasing solar gain.
Efficiency comparison: summer versus winter
If we compare the energy production of a given facility, winter typically offers between 20% and 60% of the production of a day or season of maximum solar irradiance.The specific case depends on the geographic location, the inclination of the panels, and the weather conditions.
For example, in southern Spain, a facility can produce around 60% of the energy generated in spring or summer in winter, while in more northern or cloudy locations, the percentage can decrease.
Furthermore, the Efficiency per unit of light received can be even higher in winter due to the lower ambient temperature, which optimizes the behavior of semiconductors and minimizes thermal losses.
The role of orientation, tilt and maintenance
Correctly adjusting the orientation and inclination of the solar panels is key to maximizing the use of radiation in both seasons.During the winter, it is advisable to increase the tilt to better capture the sun's rays that reach lower on the horizon.
El regular maintenance Equally important: the accumulation of snow, dust, or dirt can reduce production by up to 6,5%. Therefore, cleaning after adverse weather events is essential to keep the panels performing at their best.
Technological solutions and strategies to optimize performance
- Bifacial panels: They take advantage of the light reflected by the snow or the environment, increasing capture in unfavorable conditions.
- Solar tracking systems: They allow the orientation of the panels to be adjusted throughout the day and year, maximizing radiation exposure.
- Energy storage systems: They accumulate the energy generated during hours of maximum sunlight for later use, especially useful in winter and on cloudy days.
- Automated inspection and cleaning: Facilitates the removal of snow or dirt without additional risks or efforts.
Climate, solar radiation and their impact on society and the environment
Solar radiation not only affects the production of electrical energy, but is a central factor for the global climate, agricultural cycles and human health.Greater radiation means more evaporation, cloud formation, and weather phenomena, while months with low sunlight can lead to harsher winters and a greater need for heating.
La prolonged exposure to intense solar radiation It can also be harmful to the skin, increasing the risk of sunburn, skin aging, and melanoma. For this reason, using sunscreen year-round is essential, as UV, UVA, infrared, and visible radiation affect the dermis even in winter.
Myths and realities about solar radiation in winter
The erroneous belief has spread that solar radiation disappears in winter or that solar panels stop working efficiently.Although the intensity decreases and the days are shorter, there is always energy available to capture and convert.
Another reality is that Snow and rain can help clean the panels, improving their efficiency, although they can also temporarily block light if they accumulate on top of the panels. Most modern installations are designed with a sufficient slope to facilitate snow slide and withstand adverse weather conditions.
Keys to maintaining high solar performance throughout the year
- Periodically check the condition and cleanliness of the panels.
- Adapt the incline according to the season and geographical location.
- Choose materials and technologies that are resistant to extreme temperatures and weather factors.
- Monitor production and quickly resolve any issues to avoid energy losses.
Climatic and energy effects of variable solar radiation
The inequality in the arrival of solar radiation to Earth is fundamental to understanding climate patterns.The alternation of seasons, winds, rains, and droughts is closely related to the solar cycle and the amount of energy received.
Furthermore, energy systems that harness this radiation, such as solar panels, play an increasingly critical role in the transition toward sustainable models, reducing emissions and dependence on fossil fuels.
Solar radiation, with its seasonal variations, not only determines the efficiency of photovoltaic installations, but also shapes our climate, our customs, and the well-being of ecosystems and society. Investing in knowledge, prevention and technology is the best way to maximize its benefits and prevent its risks. in every season of the year.