EXAMPLE OF PHOTOVOLTAIC SYSTEM CONFIGURATION 23 kWp

The post gives an example of the configuration of a 23 kWp photovoltaic system.

General information of the photovoltaic system configuration 

- Latitude, longitude: 44⁰ 6 '1 ", 18⁰ 9' 3"

- Elevation: 422 m.

- Installed power of the production facility: 23 kWp

- Connected power of the production facility: 23 kW

- Annual production of electricity: 26130 kWh

- Generator type: solar photovoltaic panels with inverters

- Total number of photovoltaic (PV) panels: 84 (pcs) unit power 275 Wp

- Total area of ​​photovoltaic panels: 84x1,7x1,1 = 157 m²

- Total number of inverters: 1

- Manner of connection: to the corresponding electricity distribution network     according to the conditions of the competent electricity distribution company    defined by the electricity consent

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Description of the photovoltaic system configuration (about design)

 

The system consists of one solar field mounted on the south side of the single-roof roof of the ground floor auxiliary building, built of slag-concrete elements, a wooden roof structure with a cover of corrugated saloon panels and a usable roof area of ​​approximately 180 m². The SP solar field will consist of 84 modules, with 4 strings of 21 series-connected solar panels each, allowing a total power of 23 kWp. The solar field is connected directly to the input string boxes of the inverter. The inverter is mounted in the existing room on the ground floor of the building, on the inner wall. The AC side of the inverter is connected with cables of appropriate cross-section, laid in cable ducts, to the LV block.

The panels are placed in a portrait position facing the south side of the world, to which the side of the roof is facing, at a slope parallel to the roof slope of approximately 300, on a purpose-built structure. Adequate aluminum construction is used for the installation of the panels, with the help of which the necessary conditions for the installation of solar panels are achieved, in order to obtain the maximum utilization of the sun's radiation.

For electrical connection of solar panels, a halogen-free solar conductor in black and red with a cross-section of 4mm² / 6mm² is used. The electrical connection between the panels was achieved using MC4 connectors and T splitters. Metal parts of the structure and panels are galvanically connected to the derived earthing systems. The inverter is equipped on the DC and AC side with overcurrent protection devices, surge arresters and earthing busbars.

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An example of selecting photovoltaic panels when configuring a photovoltaic system (everything you need to know about solar energy)

 

The basic element of any photovoltaic system are photovoltaic modules. The modules consist of a large number of photovoltaic cells that are connected in combination (in series and in parallel) to obtain the appropriate voltage or power. Their basic characteristics are longevity, high efficiency, and high mechanical and atmospheric resistance. The most important factor that affects the electricity production of any photovoltaic module is its power. The power of photovoltaic modules depends on the age of the module and the weather conditions. It decreases with increasing temperature, and increases with decreasing temperature. When comparing different types of photovoltaic modules, it is important to compare their minimum powers.

An important indicator of the general quality of the manufacturer of photovoltaic modules is certainly the amount of deviation from the rated power depending on the aforementioned factors, temperature and age.

For the realization of the photovoltaic system, photovoltaic modules IBC PolySol 275 CS5, power 275 W, manufactured by IBC SOLAR, based on polycrystalline cells, were selected. The characteristics of the built-in modules are given in the following table:

MODULE IBC SOLAR	PolySol 275 CS5
Maximum power Pmax (Wp)	275
Voltage at maximum power Ump (V)	31,8
Current at maximum power Imp (A)	8,67
Idle voltage Uoc (V)	39,0
Short circuit current Isc (A)	9,23
Maximum voltage of the Umax system (V)	1000
Module dimensions (mm)	1650x992x40
Module weight (kg)	19,5
Usefulness (%)	16,8
Number of module cells	60
Connecting cable	2x1 m, 4 mm2, MC 4 connector
Module protection	IP 65, 3 diodes
Number of modules	84

 

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Example of inverter selection in photovoltaic system configuration (about control of power inverters)

 

Solar inverters convert the DC voltage of solar modules into AC voltage of regulated amount and frequency, synchronized with the mains voltage.

For the photovoltaic system in question, it is necessary to install one three-phase inverter for parallel operation with a network of rated voltage 400/230 V, 50 Hz. The power of the DC inputs of the inverter must be at least equal to the power of the corresponding solar field. All separate DC inputs of the inverter must have the MPPT function.

Inverters must have integrated:

 

 DC protection against polarity reversal

 Surge protection

 AC short circuit protection

 String error detection

 Earth connection monitoring

Inverters should be able to communicate with external devices through which all important parameters of the system can be recorded and stored.

An inverter type FRONIUS ECO 25.0-3-S, manufactured by FRONIUS, was selected for this photovoltaic system.

The characteristics of this type of inverter are given in the following table:

INVERTER	FRONIUS ECO 25.0-3-S
Input sizes
Maximum DC power (kWp)	37,8 (kWp)
Maximum DC voltage	1000 (V)
Maximum DC current	44,2 (A)
DC input	6
MPPT	1
MPP voltage interval	580-850 V
Surge protection	Da
Output sizes
AC rated power	25 (kW)
Nominal AC voltage	400 (V)
Maximum output current	37,9/ 36,2 (A)
Harmonic distortion of THD	< 2 %
Rated frequency 50.60 / - 6… + 5 Hz	50/60 ( Hz)
Power factor Cosφ	1
Efficiency
Maximum efficiency	98,2 %
European efficiency	98,0 %
Night consumption	<1 (W)
Protection
Protection	IP 66
Permissible ambient temperature	-25 do +65°C
Mechanical characteristics
Dimensions	725/510/225mm, 35,7 kg

 

The input DC voltage enters the Maximum Power Point Tracking (MPPT) system, which ensures that PV modules in any operating conditions, regardless of the intensity of solar radiation or its operating temperature, always operate at the same maximum voltage.

This inverter is also equipped with an advanced power limitation system function, this function can be activated and configured depending on the needs of the system.

The DC voltage obtained by connecting the PV module for the selected inverter should be between 580-850 V, and the maximum input current should not exceed 44.2 A, the maximum output current is 37.9 A, and is limited according to the allowable connection power of 23 kW.

A computer can be connected to the inverters via a serial channel (RS485), which serves as a feedback to the manufacturer, in which all important electrical quantities are stored and the produced electricity is registered.