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Working principles and productivity


Simple diagram of a solar panel element
n-type, e.g. phosphorus-enriched silicon
connecting joint
p-type, e.g. boron-enriched silicon/and productivity

HISTORY: The photoelectric effect was discovered by French physicist Alexandre Edmond Becquerel in 1839. After 50 years, an inventor named Charles Fritt created the first application for this phenomenon in the form of a solar battery. The first solar battery was based on selenium and gold, and had an entire per cent of efficiency. In the following 50 years, nothing of importance was achieved in the development of solar batteries, only after the war in 1946 did Russell Ohl patent the first modern solar battery. By 1954, it was found that certain silicon-based semiconductors are very sensitive to solar radiation and testing began on modern solar batteries with nearly 6% efficiency. Soon it became clear that solar batteries are most useful for space travel, where the sun is always shining, and the first solar panel for a satellite was completed by 1958. In 1970, Soviet scientists led by Zhores Alfyorov made the first GaAs type solar battery and the modern solar battery was born.



Every solar battery actually consists of several smaller elements or cells, which are connected serially or in parallel, depending on the desired current strength or voltage. Each individual cell consists of a layer of p- and n-type semiconducting material. Both layers consist of purified silicon in the case of a silicon-type solar battery, which is turned into a p- or n-type semiconductor with the help of additives.

n–type semiconductor is usually silicon alloyed with boron.
p–type semiconductor is usually silicon alloyed with phosphorus.

In addition, a solar battery is covered with an anti-reflecting layer to increase its effectiveness. Light makes the charge carriers in the upper semiconductor move, as the solar radiation energy is strong enough to break single charge carriers away from the core which holds them. As the only possible direction of movement of current has been determined with the p-n transmission, charges start to move in that direction. In addition, both semiconductors are connected with external cables, thus creating a closed circuit which enables us to benefit from this current.



Productivity mostly depends on the intensity of the sun and effectiveness of the panels. The most adequate data on solar intensity in our region is available in this database:

Photovoltaic Geographical Information System
Select the site where you want to install panels from the map.

Important terms and explanations:


PV technology – select the mono- or polycrystal panel as applicable.
Installed peak PV power – provide the capacity of your solar panel system in kW. (e.g. 250W x 10 = 250W = 2.88 kW)
Estimated system losses - provide “2%”. As we offer high-efficiency inverters with individual controllers for each panel, the system loss is very low.
Mounting position – select “Free standing” if the installation is on a frame or ground.
Slope – slope of the roof. In Estonia, the optimal angle is 35°….40°; flat roof 0°; wall mounting 90°.
Azimuth – direction of panels. The optimal direction is south, i.e. 0°
Show graphs – shows annual productivity by months on a graph. Show horizon shows the trajectory of the sun on a graph.
The table contains cells: “Ed” average daily productivity (kWh) in the given month. “Em” indicates monthly productivity (kWh). At the end of the “Em” slot is the productivity of the PV system per year (Total for year kWh), which is also the most important indicator.

References: Horisont 6/2007.