Aerial view of the Buštěhrad photovoltaic power plant
Buštěhrad lies near Kladno in the plains of households in Central Bohemia. The Buštěhrad photovoltaic power plant is located on the border of a former industrial site. The names of the power plant’s main three parts were derived from its shape resembling a rifle (the Stock, the Trigger, the Barrel).
The whole aerial panorama is dominated by the former Poldi – Dříň steelworks northwards. Towards the northwest, you can see the cooling towers of the Kladno Power Plant and the whole city of Kladno can be seen in the west. The local castle, Mining Museum and Sládeček Museum of Local History are the main attractions for its visitors.
The easterly direction offers a view of the town of Buštěhrad, where tourists can visit a castle or the Ota Pavel Museum. In the southeast lies the village of Lidice with its National Memorial and a monument commemorating the victims of 1942. In the southerly direction, you can see the villages of Hřebeč and Netřeby.
With its natural conditions, this is one of the best locations for a solar power installation in the area. The annual total global radiation here averages out at up to 4,100 MJ/m2. Moreover, the area next to the industrial site would hardly find an alternative use.
Built in the spring and summer of 2010, the power plant with an installed capacity of 2,396 MW, generates enough electricity to cover the consumption of about 640 households Central Bohemia every year.
How photovoltaic power plants work:
The direct conversion of solar radiation into electricity uses the photovoltaic effect, during which electrons are released in a substance by light. This is based on the properties of semiconductor materials. A semiconductor can have either n-type conductivity caused by the presence of impurities providing free electrons (negative charge carriers) or p-type conductivity associated with the presence of impurities that capture electrons, leaving “empty spaces” that behave like positive charge carriers in the semiconductor. Thanks to the properties of the two semiconductors, a potential difference is formed across the interface between them, called a p-n junction, with the n-type semiconductor being positive and the p-type semiconductor being negative. If a light quantum hits the junction area, it passes its energy to the material: this makes an electron jump to a higher energy level, leaving an “empty space” that behaves like a positive charge. Due to the diffusion potential difference, the two charges of the created pair separate – the electron is attracted to the n-type area, the “empty space” in the opposite direction. If a cell is hit by a stream of photons, there are many such charges and an electric current flows when the circuit is closed.
Illustration of the photovoltaic effect
Eastern part of the panel array
The eastern part of the site (the Barrel) is a continuation of the central part. It lies solely on a slope below the former site of the Poldi – Dříň steelworks, stretching to its easternmost edge.
Central part of the power plant
The main part of the Buštěhrad power plant (the Trigger) lies on a slope adjacent to the former site of the Poldi – Dříň steelworks. The rows of photovoltaic panels face directly south. Pole mounts driven about 2 metres underground form a base for the support frames. These carry the actual polycrystalline silicon panels – the technology for direct conversion of sunlight into electricity. The cells consist of a large number of smaller polycrystals with an efficiency range from 12% to 15%. The main cabling runs underground; group converters ensure that the power plant’s production does not decrease when a portion of the site is accidentally shaded. All of the power plant’s equipment is easy to dismantle and recycle.
The panels can work with direct incident radiation as well as diffuse sunlight. The result is that the power plant operates, with a somewhat lower output, even if the sky is cloudy. The photovoltaic power plant, however, does not generate electricity at night.
In addition to about 400 meters of panel arrays on the slope, the central part of the Buštěhrad photovoltaic power plant includes 8 rows of arrays installed on level ground along the access road. Spaces between the rows are set up to prevent the modules from shading one another and to allow vehicles to drive in between the rows, e.g. when cleaning the panels. Natural grass grows between the rows of modules and under them. The ground under the panels on the slope is cleared of vegetation.
The photovoltaic panels and converters are connected in a manner that reduces line losses. DC current lines are made of wires intended for photovoltaic applications with appropriate certification and resistance to weather, including UV radiation.
Inverters
Power inverters are devices that change DC voltage generated by the solar panels to 230/400 V AC voltage The efficiency of AC/DC conversion in inverters highly exceeds 90%. Thanks to additional circuitry, they also provide data on the energy produced and other values. The production is carried from the inverters to the substation by standard AC cables.
Panel underside
In addition to the pole mounts and support structure, the non-production sides of the photovoltaic panels and especially the interconnecting cables are an unusual sight. The DC cables interconnect production sections and carry the generated DC voltage of several hundred volts to the appropriate inverter. All connecting material for the pole mounts and support structure is made entirely of stainless steel.
Substation
The heart of the whole power plant is the substation with a set of protective housings for the control electronics. All of the electricity generated in the power plant runs through the inverters to the substation. The output of the photovoltaic power plant then flows through an underground cable connected to the 22 kV high-voltage grid at the Kladno substation, Kladno node area.
Electrical enclosures
From the left, you can see the enclosure of the power plant’s main switch (+J1), then the housing of the current and voltage measuring array (+J2) and switches for the station service transformer (+J3).
Then there is the enclosure with a disconnecting switch (+J4), which allows shutting off the current under full load. With its digital display, the enclosure helps the operator monitor the basic performance variables. A thermometer allows monitoring the room temperature, which should not reach any extreme values throughout the year.
The last pair of enclosures (+J5, +J6) contains disconnecting switches for individual transformers. The wire screen behind the door covers the station service transformer.
Control room
The photovoltaic power plant operator’s office is also the control room of the environmentally friendly electricity source. The deployment of advanced technology and three working monitors enables the plant operator’s online.
- Power plant operation, monitoring any outages,
- observation of any movement inside and outside the site through CCTV
- and communication with the surroundings.
You can also see a board with keys to all on-site equipment, a noticeboard with an overview of the most important regulations and work safety rules and archives with all operational documentation for the power plant in the control room.
The power plant’s operation is also generally monitored from our renewable resources supervising centre in Hradec Králové.
Western part of the panel array
The western part of the site (the Stock) forms a narrow strip running from the former steelworks site in the north almost all the way down to the Buštěhrad-Kladno road in the south.
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