To improve the performance of solar PV modules, our company conducted a number of studies, concluding that the following factors affect the efficiency of solar PV elements:
1. Technical performance of solar panels
World manufacturers of this type of product have established the production of batteries of various types, namely: a) organic polymer photocells that have an efficiency of 5-7%;
b) cadmium photocells have an efficiency of 11%;
c) photocells consisting of mixtures of gallium, copper, indium and selenium salts and have an efficiency of 15%;
d) polycrystalline solar cells have an efficiency of 13-17%;
d) in single-crystal, the efficiency index is 18-22%.
There are developments in which the efficiency level is more than 26%, photovoltaic cells are constantly being improved. Also one of the factors of imperfection of solar cells is that at high temperatures the photovoltaic modules lose their productivity and are designed to operate at a temperature of 25 degrees Celsius. With a temperature increase of 1 degree, they lose their productivity by 0.41%.
For example, a 100 W photovoltaic module in the summer at a temperature of 35 degrees Celsius will give a performance of 90 W and vice versa – in winter at a temperature of -20 degrees the 100 W module will have a capacity of 110 W. But the latest types of photovoltaic cells that are on the market are capable of operating at temperatures from -40 to + 80 degrees Celsius. Every day, photovoltaic modules become more advanced.
2. Luminous flux density and geographical location of the modules
Our planet receives energy from the Sun – this is 99.8% (everything else is the geothermal energy of the Earth). Thanks to the Sun, life exists on planet Earth. On a cloudless sunny day, at noon local time, the surface of the earth receives from 700 to 1300 W / sq. m (depending on location, or latitude and longitude). This value is called the intensity of solar radiation or the density of the light flux.
It should be noted that the intensity of solar radiation passing through the earth’s atmosphere decreases by 67 W / sq.m, because solar radiation is absorbed by water molecules (water vapor) H2O, carbon dioxide CO2, methane CH4 and various types of pollution, so the atmosphere of the earth heats up and additionally heats the earth’s crust. This extremely harmful phenomenon is called the greenhouse effect.
Consider a map of Ukraine, developed by European researchers and manufacturers of photovoltaic modules. The map shows global solar radiation and the potential of solar energy for optimally tilted photovoltaic modules. Where the longitude and latitude of the location of the photovoltaic elements, the degree of atmospheric pollution and the length of daylight are taken into account. Under the map is a graph of the annual total solar radiation intensity per year (kWh / Sq. M year).
As you can see on the graph, the total intensity of solar radiation (per year) for the conversion device installed directly on the ground (the right column of the scale) and with the location of the photovoltaic module with the optimal angle of inclination (left column of the scale). For example, in the city of Vinnitsa, the earth’s surface receives 1060 kW of energy per 1 sq. m. And if the generating device is located with an optimal angle of inclination, it will receive 1,420 kW of energy per 1 sq. m during the year. m
3. Optimum angles of inclination of the “receiving surface”
As can be seen from the above, there are two basic conditions that affect the efficiency of the PV modules, there is a third most important component, which most affects the efficiency of the photovoltaic cell. These are the angles of inclination of the working surface of the device to the sun. The greatest amount of solar energy will receive work surfaces located on two-coordinate solar trackers.
For example, 1 square meter of the working surface located on the forum for the city of Vinnitsa will receive 3120 kW of solar energy during the year, which is 2.19 times more than 1 square meter will receive. m surface stationary located at an optimal angle to the sun.
June 20, 2019, we conducted an experiment. In the city of Vinnitsa was located a solar concentrator of own production “SV-eko-4” with a peak power for the city of Vinnitsa 4.2 kW (photo 1).
Photo 1 Photo 2
On this day, the sun rises at 5-00, sets 0 21-14, the duration of a sunny day is 16 hours 14 minutes. The experiment started at 5:00. Thermal energy was received by a heat accumulator with a capacity of 350 liters (photo 2). The experiment lasted until 8 a.m. after which the sky was covered with clouds. At 8-30 it started to rain. Within 3 hours, the temperature in the heat accumulator was able to increase by 19 degrees Celsius or to obtain thermal energy of 6 kW 650 W (raising the temperature by 1 degree is 350 W). I would like to note that we not only designed a large parabola of the concentrator, a heat receiver and a small parabola.
An integral component of a solar concentrator is a tracker. Which in turn consists of a control board and a mechanical part. We designed the tracker in such a way that it can withstand loads with a margin of safety up to 10 times, all bearings, rotary and lifting mechanisms that are used in the manufacture of the tracker have a European certificate of conformity. Designing a solar concentrator, we created a solar tracker of high quality and reliability, which has a reasonable price even for the Ukrainian consumer. Our tracker can be used with great success at SES for private households and industrial facilities.
Solar panels work efficiently when their surface is perpendicular to the sun’s rays, so the angle of inclination to the horizon is one of the defining settings for a solar power plant. Another factor affecting the amount of electricity generation is azimuth – the angle between the direction to the sun and the direction to the south. Tracking these parameters is not yet a difficult engineering task, but its implementation requires additional equipment and high financial costs. Therefore, mainly solar panels are installed on the roofs of houses or on special farms.
Thanks to the experiment, we simulated the situation, see the figure below.
In one hour, the Earth rotates around the sun at an angle of 15 degrees. On June 20, a “sunny” day lasts 16 hours 14 minutes, equal to the azimuthal angle of 243 degrees. We assume that the working surface of the generating device is stationary with the optimal angle of inclination to the sun.
As can be seen in the figure, from five to seven hours and from the nineteenth to the twenty first hour of 14 minutes the stationary device will not work since solar radiation does not fall on the generating (working) surface. And only after seven hours will it begin to generate energy. As the experiment showed, a solar concentrator with a peak power of 4.2 kW from 5-00 to 8-00 generated 6 kW 650 W, while a stationary device would generate only 600 W during this time.
It is clear that the solar concentrator generates thermal energy, the photovoltaic element generates electrical energy, but the physics of the process is the same, the difference is that a light photon is working in the solar module, and a short-range thermal wave is in the solar concentrator. The factors affecting the operation of the solar module and the concentrator are the same, these are the angles of inclination of the working surface to the sun and the density of the solar flux.
At the end of the publication, we can confidently state that the SES installed at the two-coordinate forum will generate twice as much electricity during the year as a similar SES installed permanently with an optimal angle of inclination.