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General information Print E-mail

The Sun – a source of energy
The Sun is a huge energy source providing limitless and free of charge solar energy all over the Earth. Photovoltaics is the technology enabling the use of this energy by directly converting solar energy into electric energy.
Photovoltaic systems are a high-technological product which is ever more present in our everyday life. More and more solar installations are erected on the roofs of residential, public and industrial buildings. Even in cloudy weather, electricity is supplied by photovoltaic systems.
Production of energy through photovoltaics is environmentally clean. It converts the solar energy into electricity without any chemical or mechanical intermediate steps. There is no noise or harmful emissions. That is the reason why photovoltaics is a reasonable answer to  the climate change consequences.  Photovoltaic systems are built from materials that are in sufficient quantities and can be recycled. Moreover, a photovoltaic installation requires no complex maintenance and servicing personnel and has a long service life (around 30 years).
The many advantages of solar electricity make it the energy of the future.

Components, principle of action and types of photovoltaic systems
The smallest unit of a photovoltaic system is the solar cell, which is a thin wafer of highly purified silicon. A certain number of photovoltaic cells are arranged in a solar module.  Several modules can be installed on a roof. Modules connected in an electric circuit form the so-called springs. Their totality represents the solar generator.
A solar module with an approximate power of 120 watts can be situated on an area of one square meter. Photovoltaic systems built on the roofs of detached  or semidetached houses are most frequently from 1000 watts (1 kilowatt) to 30 000 watts (30 kilowatts) and occupy an area from around 8 to 240 square meters.
Under the influence of solar light, electrical voltage occurs in the solar cells and direct current runs, which is transformed by the inverter into alternating current. The inverter not only performs electricity conversion but controls the overall operation of the photovoltaic system as well. Such converted electricity can be used for personal needs or supplied to the mains.
Depending on the place of installation, photovoltaic systems are being installed either on a roof or on free areas. In case of roof systems, either the roof slope is used or an additional structure is built (provided the roof is flat). The optimum slope for effective operation of a photovoltaic system is approximately 30°. In case of installing photovoltaic systems on free areas, it is possible to use sun tracking devices for enhancing the system efficiency.

Investments and return on investment
The costs of building a photovoltaic system vary depending on the system’s power, type of structure, location and the technical equipment selected. With the increase in power, the costs per unit (1 kWp) installed power capacity decrease. A solar system requires minimum service and maintenance costs.
The return on investment in a photovoltaic system is guaranteed by the laws and regulations in force in Bulgaria. Pursuant to the Renewable and Alternative Energy Sources Act,  the purchase of electrical energy generated by photovoltaic stations is guaranteed by the government for a period of 25 years. The preferential energy purchase prices are as follows:
-    for power plants working with photovoltaic modules up to 5 кWр – BGN 782.00/MWh;
-    for power plants working with photovoltaic modules over 5 кWр – BGN 718.00/MWh.

In compliance with the international commitments made, Bulgaria is obliged to increase the share of the energy generated by renewable energy sources with 20% by 2020.