Do photovoltaic installations work in winter and on cloudy days?

The absolute foundation for the operation of PV installations is access to sunlight. But how significant is its intensity? Do photovoltaic cells work in winter when the sun appears on the horizon for a shorter time than in spring and summer? Do they completely stop working at night? How do clouds affect photovoltaic panels? We answer these and many additional questions in this article.

Do photovoltaic panels work at night?

Before we answer the above question and explain the problems that photovoltaics in winter can cause, let's start with a brief and as simple as possible discussion of how PV installations work.

A photovoltaic installation consists of many panels, the structure of which includes so-called photovoltaic cells. The entire concept behind this solution boils down to capturing photons (i.e., units of light) falling on the surface of these cells and converting them from solar energy into electrical energy. Considering this information, the answer to the question of whether photovoltaic panels work at night, when light does not reach them, seems obvious – they do not work. These devices can only harness energy when sunlight reaches their working area.

Efficiency of photovoltaic installations in winter and during warm seasons

Having answered the question of whether photovoltaic panels work at night, it is worth considering the next relevant issue for this entry – do photovoltaic cells work in winter? Absolutely, provided certain conditions are met.

We already know that the essential factor for the operation of PV installations is access to solar radiation. During the winter period, this access is indeed reduced, but that does not mean that we do not experience light at all during the day. When the sun is in the sky, the cells can conventionally harness energy, as long as nothing else obstructs their access to the source of photons.

A more significant question is not whether photovoltaic installations work in winter and on cloudy days, but rather how effectively they can operate under such circumstances.

Photovoltaics in winter, of course, operate much less efficiently than during the summer and spring months. It is estimated that an average single panel with a power of 1 kWp can generate up to 180 kWh in a single month during summer, while in winter, this value can drop by as much as 85%, oscillating around just 20-30 kWh in December and January.

In practice, much depends on additional factors such as the location of the system, the geographical latitude at which it is located, the angle of inclination of the panels, and their quality. However, regardless of these variables, the answer to the question of whether photovoltaic cells work in winter remains unequivocally affirmative.

Efficiency of photovoltaic installations in winter vs. profitability of their use

Concerns about how photovoltaics function in winter often lead investors to abandon the idea of their installation, fearing the unprofitability of this solution. This is unfortunately a significant mistake, often resulting from insufficient analysis of the issue.

Indeed, the efficiency of photovoltaic installations decreases in winter; however, only layers of snow accumulating on them can completely cut the system off from its energy source. With regular snow removal, the panels can operate quite efficiently, and under specific circumstances, even more efficiently than during warm seasons. It should be noted that the efficiency of PV cells increases up to a certain threshold as the ambient temperature decreases. In practice, it turns out that winter days with strong sunlight and cold temperatures provide optimal working conditions for them.

At this point, it is worth dispelling another doubt regarding the operation of photovoltaic panels in frost. Modern PV systems can withstand temperatures as low as -40°C, a great example being the installation used daily at the Henryk Arctowski Antarctic Station located at the South Pole.

How do clouds affect photovoltaic panels?

As a rule, clouds negatively impact the efficiency of PV panels. The more they cover the sky, the less sunlight reaches the cells, and consequently, the less energy they will be able to produce. According to common estimates, intense cloud cover (when the sun is not visible at all) can reduce their efficiency by as much as 90%. However, such situations occur relatively rarely and do not significantly affect the overall monthly performance.

Additionally, in response to the question of how clouds affect photovoltaic panels, it is worth looking at the other side of the coin. During specific positions of the sun in the sky, a so-called cloud edge effect can occur, where the number of photons hitting the cell increases due to their passing through the edge of the cloud, which can intensify the operation of the installation.

When considering whether photovoltaic installations work in winter and on cloudy days, it is important to realize that even in cases of low efficiency under certain conditions, the owner of the installation can still draw from the grid the surplus electricity produced in spring and summer. The bill received from the energy network operator will reflect a summary for the entire year, not just a single month. Therefore, this issue should be viewed from a broad, year-round perspective, and it turns out that after a few years of panel installation, the investor will always come out ahead in terms of this venture.

See: How to safely choose a photovoltaic company?