Photovoltaics in Buildings

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Solar photovoltaic systems (PV) convert solar energy into electricity to power home appliances


The PV systems quietly generate electricity from light without producing noise, waste heat, air pollution or hazardous waste. There are different types of solar PV systems, but the principle on which they operate and the components they consist of are similar. Key components of any roof-top solar photovoltaic systems are the array of solar cells (modules) and the inverter.

Other important components of a roof-top solar PV system include a PV generation meter, mains fuse box, electricity export meter, and connecting cables and sockets.


All PV cells operate at a low voltage; therefore they are often connected together in series to form PV modules that may be up to several meters long and a few meters wide with different sizes and power output for household needs. The PV modules convert sunlight into electricity. The amount of electricity produced depends on the amount of light that falls on the PV modules. PV does not require direct sun rays, but only diffused light to generate electricity, however, the output from a PV module depends on the intensity of the light.

The PV modules are connected to the inverter that converts the direct current (DC) electricity generated by the panels into alternating current (AC) electricity that matches the building’s mains electrical grid supply. If the building is not grid connected the inverter is usually replaced with a battery bank to store the electricity generated.
The PV technology is proven and established. Unlike wind turbines, a solar PV system is silent and can be integrated into or mounted on an existing roof, however, roofs that have any shaded areas for any part of the day would not be suitable for Solar PV systems. The panels have no moving parts, which means that maintenance costs are kept to a minimum.

Solar PV modules are rated at peak output power. Watts peak (Wp) is the peak power in Watts (W) produced in standard test conditions. These conditions are rarely achieved consistently in practice as the output fluctuates with solar radiation levels, which vary considerably during the day and also during the year. According to the Joint Research Centre of the European Commission, the yearly sum of global irradiance incident on optimally-inclined south-oriented photovoltaic modules for Bulgaria ranges between 1300-1700 kWh/m2. It is estimated that for a Bulgarian home the yearly sum of solar electricity generated by 1 kWp PV system will be around 1100 kWh/kWp.

A solar PV system is an excellent solution to provide electricity for residential buildings in remote areas of Bulgaria where connection to the electric grid is expensive or impossible. At the same time, the favourable feed-in-tariffs which should be soon introduced in Bulgaria for the grid connected solar PV systems will make them a viable investment opportunity for the Bulgarian households interested in generating electricity at their homes and selling it to the grid.

If householders are interested in producing and selling solar PV generated electricity to the grid, they are advised to contact the local power distribution company. Some power distribution companies are collaborating with the local banks participating in the REECL Programme and may be able to assist in providing advice and arranging financing for optimal solutions.