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Knowledge Base

Photovoltaics is a science concerned with the transformation (conversion) of solar energy into electrical power. Devices in which such a conversion takes place can be called photovoltaic generators – they are direct current generators. The basic element of the photovoltaic generator of any size is a photovoltaic cell – a semiconductor device (usually silicon) – in the shape of a thin plate with electrodes.

It is the photovoltaic cells that convert sunlight directly into electricity. By connecting single cells together we can obtain the desirable electrical parameters (current and voltage) – which can be practically used. Such a set of cells which are hermetically sealed and embedded inside of a steel frame becomes an independent electricity generator called a photovoltaic module. The combination of numerous modules is called a photovoltaic panel and usually panels are the basis of the applied photovoltaic system. The most popular photovoltaic cells are silicon-based (on a silicon base). Silicon is a semiconductor – it means that only in certain conditions it may conduct the electric current. In the technological process silicon base is externally treated and doped in order to obtain special electrical and optical properties – enabling the photovoltaic effect.

The light which falls on a cell is absorbed and generates electric charges (positive and negative). These charges are distributed on both sides of a cell – just like in a capacitor, the difference of potentials will occur between the surfaces of a cell. Placing metal electrodes on both sides of a cell initiates electrical current flow which may power a particular receiver (a calculator, a diode, etc.). If a cell is exposed to solar radiation in a continuous manner, the current flow (current intensity) stabilizes at a level commensurate with the intensity of that radiation. 

Photovoltaic system functioning

Photovoltaics is a direct conversion of solar radiation into electrical power.

Photovoltaic cells (PV)

Photovoltaic cells, also known as solar cells, are made of the same types of semiconductor materials (e.g. silicon) as those used in microelectronics. It is a semiconductor material in which the conversion of solar radiation into electricity takes place. For the first time the photovoltaic effect was observed by A.C. Becquerel in 1839.

The principle of operating– the photovoltaic effect

When solar radiation hits a solar cell, loose electrons are knocked out from atoms in the semiconductor material. If the wires are attached to positive and negative sides, which form an electrical circuit, electrons can be captured in the form of an electric current.

The number of solar cells connected together and fitted in a support structure or in a frame is called a photovoltaic module. Modules (called solar modules or photovoltaic panels) are used to provide all kinds of electrical equipment, including small constructions and even large solar power plants, so called photovoltaic farms with electricity

Photovoltaic module

A photovoltaic set is located between layers of PET and EVA leaf and a toughened glass pane. The whole thing is hermetically laminated put into a light rigid frame, usually aluminum, which provides the mechanical strength of the modules and facilitates their installation. The construction of modules has to provide good weather resistance throughout the whole service life which is usually minimum 25 years. These types of photovoltaic modules have been successfully used all over the world, both on a small and on a large scale (e.g. in solar power plants).

The cross-section of a photovoltaic module

Photovoltaic cells generate electricity and solar collectors generate thermal power.

The advantages of using photovoltaics and photovoltaic systems:

Solar systems are highly secure and reliable. They do not generate any noise or pollution and moreover, they are recyclable. The service life of panels comes to over 30 years. After 25 years they retain minimum 80% of the initial power and capacity. Thanks to the PV systems they will generate electricity for a long period of time in a highly efficient, clean and environment friendly way. It is possible by using the appropriate hardware configuration and device parameters.

It is worth knowing that the solar system considerably increases the value of the property. It also makes it possible to save money despite of the continuous increases of electricity prices. It is a quick return on investing in the technologies of the future. The solar systems excellently protect against price fluctuations and increases. They also give the possibility to sell electricity and to be totally or partially independent from the public grid (depending on the designed and selected installation). It is also a way to generate electrical power in an unlimited way in places which are hard to reach.

Investing in photovoltaics

Power plants or solar farms (photovoltaic) are not only the source of clean energy but also the source of the income for the Investor. There are two possibilities of generating the income:

Selling electricity produced by a photovoltaic power plant to a grid

It is the most popular way to earn money in the solar industry all over the world. In different countries there are legally guaranteed rates, so-called tariffs, at which electricity boards are obliged to buy electricity from solar power plants. These rates are guaranteed for a period of several years so that after a 5-8 year period of the return on investment the Investor has the possibility to generate a profit. From a technical point of view, the total energy produced in power plants or solar farms is sold to the grid through a separate measurement system or a bidirectional counter. 

Currently in Poland applying such a system is still quite complicated. First of all, there are no guaranteed rates- there is only the system of green certificates, however, the price is not sufficient to cover the cost of the investment. Besides, there are no regulations concerning the terms of connection which means that the connection and the measurement system must be financed by the Investor. Additionally, the licence is obligatory. 

Consuming energy for own needs and saving on the electricity bill.

This is the second and at the moment the most easily available in Poland way of using electricity produced in solar power plants. The assumption is that the photovoltaic system will not produce more energy than a particular building needs on a regular basis. That is why there will be no surplus of electricity and no need to sell it to the grid and therefore the Investor will not be required to obtain a licence and sign a contract with an electricity board. 
In the example presented here maximum 80% of energy used in a building during the day comes from the photovoltaic system, while the remaining 20% is obtained from a parallel power supply from the grid. 

Taking into consideration the current price for energy which is 0.65 PLN / kWh and taking into account the growth rate of energy prices at the level of 7.64% (the average for the period between 2007 and 2012 according to the Central Statistical Office), the period of return on investing in such a solar plant is approximately 9 years and is comparable to the period of return on investment in solar collectors. The difference is that the solar collectors have to be additionally serviced and every few years circulation fluid has to be replaced, whereas PV modules do not require any maintenance or any additional maintenance funding. The standard warranty for PV modules is 25 years.

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About us

Solar Group operates in the photovoltaic branch and comprises of:
Solar Service Tomasz with its headquarter in Görlitz – the company executes the projects at the territory of Germany and Eastern Europe.
Solaris Group Ewa Grochowska with its headquarter in Legnica – the company executes the projects at the territory of Poland.
“Solar Group” Sp. z o.o. with its headquarter in Gdańsk – this company was established to merge the advantages of Solar Service and Solaris Group.
Thanks to vast experience obtained from numerous executions we counsel and design – we plan, sale and build – we cope with the erection and maintenance of Solar Power Plants.
We offer complex customer services. The services begin with designs, selection of components, through delivery and execution of photovoltaic installments, with maintenance services at the end. We operate on contractual agreements with key component producers who are necessary during the establishment of Solar Power Plant. We can satisfy the highest expectations of any customer group. We have the indispensible expertise and qualification for the major Solar Power Plant projects, not neglecting the smaller installments.
We execute the investments at land, roofs, the BIPV (Building Integrated Photovoltaic) projects, at elevations, facades, awnings, walls, including photovoltaic glazing.
Our aim is a complete and perfect execution of commissioned works. This begins with the design, the quotation and the verification of a project according to the Investor’s needs, than the delivery of electric components (PV modules, BIPV, cables, inverters) and mechanical components (foundations for construction, superstructures for PV modules, BIPV, converters), with the execution of the commissioned order at the end. The works executed by us are subject to strict quality control – it is the basis for our guarantee and provides more efficient maintenance service for installments.
A team of above 250 people is ready to work in any conditions – our qualified personnel holds the relevant certification and expertise, the relevant permissions for work at heights (respected in whole Europe), holds the certification for the construction equipment. They are professionals at each single step during the establishment of Photovoltaic Power Plant.