Commercial solar installation

If you are interested in solar energy and your idea is to install a commercial solar system, below you will find a lot of information to learn about the topic of commercial solar installation that can make a good choice.

Commercial solar installation : Photovoltaic Solar Installation for Housing

Index of contents

1. Introduction

1.1- Generalities

1.2- Photoelectric principle

1.3- System architecture

2- System components

2.1- Photovoltaic modules

2.2- Charge regulator

2.3- Batteries and solar accumulator systems

2.4- Inverter or DC/AC Converter

2.5- Wiring

2.6- Protections

3- Starting data

3.1- Location

3.2- Layout of the modules

3.3- Estimation of consumption

4- Calculation of the installation

4.1- Number and connection of solar modules

4.2- Calculation of batteries

4.3- Regulator calculation

4.4- Calculation of the inverter

4.5- Wiring and protections

Introduction

1.1- Generalities

In this tutorial, the study and design of isolated photovoltaic solar installations that allow the generation of electricity for direct consumption in a single-family home that is isolated from any public electricity supply network will be carried out.

The main objective of an isolated solar installation is to produce electrical energy for self-consumption, without the need to depend on an electrical distribution and supply network, so that it becomes self-sufficient in this regard.

Therefore, it will be a question of describing the elements that make up an autonomous photovoltaic installation, including catalogs and technical specification sheets of the different equipment and presenting a practical calculation case, which can serve as a guide and model for other installations.

1.2- Photoelectric principle

The basis on which current commercial photovoltaic systems are based is the so-called photoelectric principle, through which the radiation of sunlight can be transformed into electrical energy. This effect takes place in the so-called photoelectric cells, the basic unit that makes up the photovoltaic modules or panels.

Figure 1. Photoelectric cell

All sunlight radiation is composed of elementary particles, called photons. These particles are associated with an energy value ( E ), which depends on the wavelength ( λ ) of the radiation, and whose quantitative value is expressed as follows:

 h · c E  = λ

where ( h ) is Planck’s constant and ( c ) is the speed of light. The reader is referred to consult the value of these physical constants in the following link:

>> Units of Measurement Systems

When a photovoltaic module receives solar radiation, the photons that make up said radiation affect the photovoltaic cells of the panel. These can be reflected, absorbed or pass through the panel, and only the photons that are absorbed by the photovoltaic cell are the ones that will ultimately generate electricity.

Indeed, when the photon is absorbed by the cell, the energy carried by the photon is transferred to the atoms that make up the material of the photovoltaic cell. With this new energy transferred, the electrons that are located in the most distant layers are able to jump and detach themselves from their normal position associated with the atom and become part of an electrical circuit that is generated.

Therefore, a crucial factor for the photovoltaic effect to be generated is that the cells of the solar panels are composed of a certain type of material, such that their atoms are capable of releasing electrons to create an electric current when receiving energy.

The atoms of the materials called semiconductors offer this property, that is, materials that act as insulators at low temperatures and as conductors, by detaching themselves from their electrons, when the energy that affects them is increased.

In addition, to improve their performance, these semiconductor materials are treated in such a way that two different doped layers are created (type  P  and type  N ), with the aim of forming an electric field, positive in one part and negative in another, so that when sunlight hits the cell to release electrons, they can be trapped by the electric field, and thus form an electric current.

Currently, most solar cells are built using silicon as a semiconductor material, in its mono or polycrystalline forms.

Monocrystalline silicon solar cells are manufactured from sections cut or extracted from a perfectly crystallized silicon bar in one piece, and which allow yields of 24% to be achieved in laboratory tests and 16% for marketed panel cells.

On the other hand, to obtain pure silicon solar cells of the polycrystalline type, the silicon crystallization process is different. In this case, we start from cut sections of a silicon bar that has been disorderly structured in the form of small crystals. They are cheaper to manufacture and are visually recognizable by their surface having a grainy appearance. The yields obtained are lower, reaching around 20% in laboratory tests and 14% in commercial modules.

Consequently, photovoltaic solar modules made with monocrystalline silicon cells offer a higher nominal power than those made with polycrystalline silicon cells, mainly due to the better properties offered by monocrystalline silicon, a very uniform material, compared to the lack of uniformity presented by the grain boundaries of polycrystalline silicon. In addition, another important aspect is the final surface texture presented by monocrystalline cells, of higher quality and with better anti-reflective properties, which allow the module’s performance to be improved.

Figure 4. Types of photovoltaic panels

1.3- System architecture

A photovoltaic installation for housing is intended to meet the needs of own electricity consumption, and consists of an installation diagram whose main components are shown in the attached figure.

Figure 5. Components of a photovoltaic installation

Solar panels or modules  are responsible for capturing solar radiation and transforming it into electricity, generating direct current ( DC ), also called direct current ( DC ). The number of panels will be determined by the power that needs to be supplied, and their arrangement and connection method (in series or in parallel), will depend on the nominal supply voltage and the current intensity that is desired to be generated.

Regulator or charge controller , responsible for controlling the charging of the batteries from the generator modules or panels, as well as their discharge to the internal power supply circuit of the home, also preventing excessive charging or discharging of the battery set.

Accumulators or batteries , allow the storage of energy that is produced during the day with solar radiation to be used at night or during prolonged periods of bad weather or with little solar radiation. In addition, the use of batteries allows to inject a higher current intensity than the solar panels themselves can deliver, if the interior installation of the house requires it.

Inverter or DC/AC converter , device that allows the conversion of the direct current ( DC ) generated in the photovoltaic panels into alternating current ( AC ) so that it can be used by the receivers and electrical appliances used in the home.

Figure 6. Scheme of photovoltaic installation for self-consumption

2- System components

2.1- Photovoltaic modules

The photovoltaic modules or panels are formed by the interconnection of solar cells arranged in series and/or in parallel so that the voltage and current that the panel finally provides adjusts to the required value.

Figure 7. Photovoltaic solar panel

The connection between cells can be in series and/or in parallel, to adapt the panel to the required voltage and current levels. Each cell that makes up a photovoltaic panel is capable of offering a voltage of the order of 0.5 volts and an electrical power of around 3 watts, although this value will depend on the surface that the cell measures. In this way, the power that a module can offer will depend on the number of cells it has, being designed for direct current (direct current,  DC ), at a certain voltage (normally 12 or 24 V).

The voltage and current intensity that a photovoltaic panel is capable of offering will depend on the number of cells it has and the type of connection between cells. As a general rule, solar panels are manufactured by first arranging the necessary cells in series until the desired voltage is reached at the panel output, and then these cell branches are associated in parallel until the desired current level is reached.

On the other hand, the complete system formed by the set of photovoltaic modules or panels arranged or connected in series and/or in parallel is usually called a photovoltaic generator. In order to be able to offer the desired electrical power, as well as the voltage and current intensity at the generator output, the different modules or panels will be distributed in series and/or in parallel, as appropriate.

To form a photovoltaic panel or module, the cells connected to each other will be encapsulated and mounted on a support structure or frame, forming the so-called photovoltaic module.

The elements that make up a photovoltaic module are the following:

– A transparent outer cover made of tempered glass about 3 or 4 mm thick, with its outer face textured so as to improve performance when solar radiation occurs at a low angle of incidence, as well as to better absorb diffuse solar radiation from the environment.

– An interior filling material, which works as an encapsulant, made from ethylene vinyl acetate (EVA), which serves to cover the photovoltaic cells inside the module, protecting them from the entry of air or moisture, and thus preventing the occurrence of the oxidation of the silicon that makes up the cells, given that if it occurs they will stop working.

– A back cover normally made from polyvinyl fluoride (PVF), which in addition to its properties as a dielectric insulator, offers great resistance to ultraviolet radiation, helping to serve as a barrier to the entry of moisture and offering great adhesion to the material from which the inner encapsulant is made.

– The photoelectric cells themselves, already studied in previous sections.

– Electrical connection elements between cells, to establish the electrical circuit.

– A watertight connection box, equipped with standardized connection terminals and with IP65 protection degree, from where the external wiring of the module starts for its connection with other modules that make up the complete photovoltaic generation system. Said box includes the protection diodes whose mission is to reduce the possibility of energy loss due to a malfunction due to partial shading of the panels and to avoid breaking the electrical circuit due to this effect. This is so because when a partial shade is produced on a panel, it stops generating current and becomes an energy absorber, which would cause excessive overheating of the panel that could damage it.

– The structural frame generally made of anodized aluminum that offers mechanical strength and support to the whole. Its mechanical resistance to wind and snow loads must be checked in the module manufacturer’s specifications, so that the assembly is adapted to the environmental conditions of the place where it is installed.

The features of the modules that appear in the technical information provided by any manufacturer are obtained by subjecting the modules to  Standard Measurement Conditions  ( CEM ) of irradiance and temperature, which are always the same and are used universally to characterize cells, modules and solar generators. These conditions are as follows:

– Spectral distribution: AM 1.5 G;

– Cell temperature: 25 °C.

However, the actual operating conditions of the modules will be different from the previous standards, so the corresponding correction coefficients will have to be applied to the calculation procedures that are carried out.

As indicated in the following graphs in figure 9, where the operation of a photovoltaic module is defined, the current value generated by the module grows with the intensity of solar radiation, while the voltage it offers falls as the temperature reached increases. in the module cells.

Figure 9. Operating curves of photovoltaic modules

When talking about the temperature reached in the cells of the module, it is understood that it is the temperature of the surface of the photovoltaic panel, which obviously does not have to be equal to the ambient temperature, since the surface of the module is heated by the solar radiation it receives.

A photovoltaic module usually works within a certain range of intensity and voltage values, depending on the intensity of solar radiation received, the temperature reached on its surface or the value of the electrical load it feeds.

The following figure schematically represents the current-voltage curve ( IV ) of any photovoltaic module in a continuous line, while the power delivered by the module is represented in a broken line for two different work situations ( A  and  B ).

Figure 10. IV and Potency Curves

From the previous figure it can be seen that the photovoltaic module must be made to work in the maximum power voltage range, in order to obtain its best performance.

In summary, depending on solar radiation, the temperature of the module cells (which will depend in turn on the ambient temperature, humidity, wind speed, module manufacturing material, etc.) and the electrical load it feeds , the photovoltaic module will generate a certain intensity of current ( I ) at a certain voltage ( V ), and whose product will mark the electrical power ( P ) generated by the module.

Then, in the following link, you can access the technical specifications sheet of the photovoltaic module model that has been selected for the realization of the solar installation of the house, object of this tutorial.

>> ISF-255 MONOCRYSTALLINE MODULE, ISOFOTON brand

To better understand the parameters included in the module’s technical characteristics sheet, some definitions are included for better understanding:

–  Nominal or maximum power ( P MAX ) : it is also known as peak power of the panel. It is the maximum value of power that can be obtained from the panel, and is obtained from the product between the voltage and the output current of the panel. For the selected module ISF-255, the value of  P MAX  = 255 W  (CEM).

–  Open circuit voltage ( V OC ) : it is the maximum voltage value that would be measured in the panel or module if there were no current passing between its terminals (0 amp intensity). For the selected ISF-255 module, the value of  V OC  = 37.9 V  (CEM).

–  Short-circuit intensity ( I SC ) : it is the maximum intensity that can be obtained from the photovoltaic panel (output voltage 0 V). For the selected ISF-255 module, the value of  I SC  = 8.86 A  (CEM).

–  Voltage at the point of maximum power ( V M  or  V MAX ) : it is the value of the voltage at the point of maximum power or peak power, which is usually 80% of the no-load voltage. It is also usually represented as  V MP . For the selected ISF-255 module, the value of  V MP  = 30.9 V  (CEM).

–  Maximum current intensity ( I M  or  I MAX ) : it is the value of the current at the point of maximum power or peak power. It is also usually represented as  I MP . For the selected ISF-255 module, the value of  I MP  = 8.27 A  (CEM).

Let us remember that  CEM  refers to the values ​​indicated above having been obtained under Standard Measurement Conditions.

2.2- Charge regulator

A charge regulator, whose location is indicated by the letter B in the attached figure, is a piece of equipment in charge of controlling and regulating the passage of electric current from the photovoltaic modules to the batteries.

Therefore, these devices work as a battery charger, also preventing overloads from occurring and at the same time limiting the battery voltage to values ​​suitable for their operation.

In this way, a charge regulator is responsible for controlling the way of charging the batteries when the solar panels are receiving solar radiation, preventing excessive charges from occurring.

And vice versa, that is, during the process of discharging the batteries for electricity consumption in the home, the regulator also prevents excessive discharges from occurring that could damage the life of the batteries.

In a simple way, a regulator can be understood as a switch placed in series between panels and batteries, which is closed and connected for the battery charging process, and open when the batteries are fully charged.

Likewise, currently most charge regulators have a function that allows maximizing the energy captured by the photovoltaic generator through the use of a specific technology for monitoring and searching for the generator’s maximum operating power point (MPP, Maximum Power Point), also called MPP-tracking or MPPT (from English, track: follow, track).

The charge regulator will be selected so that it is capable of withstanding nominal voltage and maximum intensity values ​​without damage according to the configuration of the installed photovoltaic generator system. In this way, it must be sized to withstand the maximum intensity of current generated in the system, both in the input line to the regulator from the photovoltaic generators, and in the output line to the loads it supplies.

In this sense, the maximum current expected by the input line to the regulator from the photovoltaic generators is that corresponding to the short-circuit current ( I SC ) of the photovoltaic generator plus a safety margin (generally 25%), to take into account possible irradiance peaks or temperature changes.

On the other hand, the maximum current expected by the output line is given by the consumption of the system loads (electrical appliances, household appliances, etc.) also increased by 25% ( I output ). The choice of regulator will be the one that supports the greater of the two previous electrical currents, as will be seen later in this tutorial.

As has already been seen, the regulator will act by interrupting the supply of electricity from the accumulation batteries to the interior installation of the home when the voltage of the batteries falls below the operating threshold, in order to avoid their total discharge that could cause battery damage.

Likewise, during periods of insolation when the solar panels are generating electricity and the battery voltage reaches a maximum limit value, the regulator will interrupt the connection between the photovoltaic modules and the batteries, or it will act gradually reducing the average current delivered by panels.

Therefore, when selecting the most suitable regulator, it must be taken into account that the load disconnection voltage of the regulator must be chosen so that the interruption of the electricity supply to the loads occurs when the battery has reached the maximum depth of discharge allowed, as indicated by the specifications of the battery manufacturer.

Any current regulator installed must be suitably protected against short circuits that occur in the home’s consumption line, as well as against the possibility of an accidental disconnection of the battery while the panels are generating power.

The internal voltage drops of the regulator between its generator and accumulator terminals will be less than 4% of the nominal voltage (0.5 V for 12 V nominal voltage), for systems of less than 1 kW, and 2% of the rated voltage for systems greater than 1 kW, including terminals. Likewise, the internal voltage drops of the regulator between its battery and consumption terminals will be less than 4% of the nominal voltage (0.5 V for 12 V of nominal voltage), for systems of less than 1 kW, and 2 % of the nominal voltage for systems greater than 1 kW, also including the terminals.

In any case, the daily energy losses caused by the self-consumption of the regulator in normal operating conditions must be less than 3% of the daily energy consumption.

Finally, indicate that every regulator used in the installation must be labeled with at least the following information:

– Rated voltage ( V )

– Maximum current ( A )

– Manufacturer (name or logo) and serial number

– Polarity of terminals and connections

2.3- Batteries and solar accumulator systems

Batteries, also called solar or photovoltaic accumulators, are used to store the electrical energy generated by the photovoltaic generator system, in order to have it at night or during those hours of the day when the sun does not shine.

However, they can also perform other functions, such as elements that serve to stabilize the supply voltage and current, or to inject current peaks at certain times, such as when starting motors.

Batteries basically consist of two electrodes that are immersed in an electrolytic medium. The most recommended types of batteries for use in photovoltaic installations are the stationary type of lead acid and tubular plate, made up of a set of interconnected electrochemical vessels of 2V each, which will be arranged in series and/or parallel to complete the 12 , 24 or 48 V supply voltage and the DC current capacity that is appropriate in each case.

Generally, the electrical association of a set of batteries is usually called an accumulator system or simply an accumulator.

The following table indicates the voltage level of the photovoltaic module depending on the power consumption needs that are demanded.

 Table 1. Working voltage of the photovoltaic system Power demanded (in W) Working voltage of the photovoltaic system (in V) < 1500W 12V Between 1500W and 5000W 24V ó 48V > 5000 W 120V ó 300V

The capacity of a battery is measured in ampere-hours ( Ah ), a unit of electrical charge that indicates the amount of electrical charge that passes through the terminals of a battery. Indicates the amount of electricity that the battery can store during charging, and then return it during discharge.

However, the time spent discharging the battery has a decisive influence on its storage capacity. In this way, the faster the battery is discharged, its supply capacity decreases, due to the fact that more energy is lost due to internal resistance, and conversely, as the discharge time increases and is carried out more slowly, then the battery capacity increases.

For this reason, since the capacity of a battery depends on the time invested in its discharge, this value is usually supplied in reference to a standard discharge time (10 or 20 hours), and for a determined final voltage.

Next, the definitions and comments on the most important parameters that define solar batteries or accumulators will be indicated.

– Battery performance factor: parameter that is defined as the quotient between the value of the ampere-hours that can actually be discharged from the battery divided by the value of the ampere-hours used in charging it.

– Self-discharge: is the loss of battery charge when it remains in an open circuit. It is usually expressed as a percentage of the nominal capacity, measured over one month, and at a temperature of 20 °C. In general, the self-discharge values ​​of the batteries used will not exceed 6% of their nominal capacity per month.

– Nominal capacity, C 20  ( Ah ): is the amount of electrical charge that can be extracted from a battery in 20 hours, measured at a temperature of 20 °C, until the voltage between its terminals reaches 1.8V/glass .

– Charge (or discharge) regime: it is a parameter that relates the nominal capacity of the battery and the value of the current at which the charge (or discharge) is carried out. It is normally expressed in hours, and is represented as a subscript in the symbol of the capacity and of the current at which the charge (or discharge) is carried out. For example, if a 100 Ah battery   discharges in 20 hours at a current of  5 A , the discharge rate is said to be  20 hours  ( C20  = 100 Ah ) and the current is expressed as  I20  = 5 A.

– Depth of discharge ( PD  or  DOD ): it is defined as the quotient between the charge extracted from a battery and its nominal capacity, normally expressed in %.

– Maximum depth of discharge ( PD max ): in this case it is defined as the maximum level of discharge that the battery is allowed before the regulator disconnects, in order to protect its durability. The maximum discharge depths that are usually considered for a daily cycle (maximum daily discharge depth) are around 15-25%. In the case of a seasonal cycle, which is the maximum number of days that a battery can be discharging without the modules receiving sufficient solar radiation, it is around 4-10 days and a depth of discharge of approximately 75%. In any case, aggressive discharges are not recommended for photovoltaic installations, but rather progressive ones, so the batteries to be used are usually with discharge of 100 hours  ( C 100 ), because the more intense and rapid the discharge of a battery, the less energy it is capable of supplying us.

– Useful capacity: it is the available or usable capacity of the battery and is defined as the product of the nominal capacity by the maximum depth of discharge allowed.

– State of charge: it is defined as the quotient between the residual capacity of a battery, generally partially discharged, and its nominal capacity.

In most cases, energy storage systems will be made up of associations of batteries, which will be connected in series or in parallel, to meet the needs, either of voltage or capacity that are demanded.

Through the associations in series of batteries, the final voltage is increased with respect to the service voltage that each battery alone can offer. In the series connection of several batteries, the negative terminal of each battery must be connected to the positive of the next one, and so on. The tension or voltage provided by the set is equal to the sum of the voltages of each of the individual batteries.

On the contrary, by means of the parallel associations of batteries, it is possible to increase the supply capacity of the set, that is, its autonomy, adding the nominal capacities of each battery and maintaining the same voltage of each individual battery.

Figure 14. Battery Associations

In another order of things, the nominal capacity of the accumulator systems used (measured in  Ah ) will not exceed 25 times the short-circuit current (in  A ) in  CEM  of the selected photovoltaic generator.

The life of an accumulator or battery, defined as the corresponding until the residual capacity falls below 80% of its nominal capacity, shall be greater than  1000 cycles , when the accumulator is discharged to a depth of 50% at 20 °C .

Although the manufacturers’ recommendations will always be followed, during the installation of a solar storage system it must be ensured that:

– the accumulator or batteries are placed in ventilated places with restricted access;

– The necessary protection measures will be adopted to avoid accidental short-circuiting of the accumulator terminals, for example, by means of insulating covers.

All batteries used in solar accumulator systems must be labeled, at least, with the following information:

– Rated voltage ( V );

– Terminal polarity;

– Nominal capacity ( Ah );

– Manufacturer (name or logo) and serial number.

2.4- Inverter or DC/AC Converter

The DC/AC current converter, also called inverter or inverter, is a power electronic device responsible for converting direct current (DC) from photovoltaic generators into alternating current (AC) for consumption in the home. It also synchronizes the frequency of the injected current with that of the network, adapting it to the conditions required according to the type of load, thus guaranteeing the quality of the energy poured into the electrical installation of the home.

Inverters are mainly characterized by the input voltage from the batteries, the maximum power it can provide and its efficiency or power output. The latter is defined as the ratio between the electrical power that the inverter delivers for use (output power) and the electrical power that it extracts from the battery system or photovoltaic generators (input power).

In general, inverters in photovoltaic installations must meet the following requirements:

– They must offer the highest possible efficiency to minimize losses. The power efficiency of the inverters (quotient between the active output power and the active input power) ranges between 90% and 97%. The performance value depends a lot on the input power, which should be as close as possible, or even try to be equal to the inverter’s operating nominal, since if it varies a lot then the inverter’s performance decreases significantly.

– Be adequately protected against short circuits and overloads, as will be seen later.

– Have elements that incorporate the reset and automatic disconnection of the inverter.

– Being able to admit instantaneous power demands greater than 150% of its maximum or nominal power, in order to deal with the starting peaks caused by many electrical appliances, such as refrigerators, washing machines, etc., which will require more power than the nominal at the time of its start-up or starting of its engines.

– Offer low harmonic distortion and low self-consumption.

– Have galvanic isolation.

– Have a measurement and monitoring system.

– Incorporate manual controls that allow the general switching on and off of the inverter, and its connection and disconnection to the AC interface of the installation.

Returning to the protections that current inverters must incorporate into their functions, these must be the following:

– Protection against overloads and short circuits, which will allow detecting possible faults produced in the input or output terminals of the inverter.

– Protection against excessive heating, which will allow the inverter to be disconnected if the temperature of the inverter exceeds a certain threshold value, and remain disconnected until the equipment reaches a lower pre-established temperature.

– Island mode operation protection, which will disconnect the inverter in the event that the grid voltage and frequency values ​​fall outside the threshold values ​​that allow correct operation.

– Insulation protection, which detects possible insulation faults in the inverter.

– Protection against polarity inversion, which allows the inverter to be protected against possible changes in polarity from the photovoltaic panels.

Lastly, the enclosure or casing that protects the inverter device will offer a basic class 1 insulation degree and a minimum protection degree of IP20 for those inverters installed inside buildings and in inaccessible places, IP30 for inverters located in the inside buildings and accessible places, and with a minimum protection degree of IP 65 for inverters installed outdoors.

2.5- Wiring

Photovoltaic systems, like any installation that remains permanently outdoors, must be designed to withstand harsh weather conditions (extreme ambient temperatures, ultraviolet solar radiation, humidity, impact resistance…) that condition the quality of the materials used. .

Until relatively recently, and due to the lack of standardization in this regard, RV-type electrical cables were used for wiring and connection between the panels, from these to the charge regulator box and from here to the electric motor of the pump. -K, very common in any other electrical installation, but for use in photovoltaic installations they offer limited characteristics. In fact, the cross-linked polyethylene of the RV-K type cable sheath is a suitable material for insulation of conventional electrical cables, but for more demanding applications, such as the case of photovoltaic installations, there are currently other cross-linked materials but with characteristics highly improved, suitable for these applications.

Thus, for specific use in photovoltaic installations, it is recommended to use  PV ZZ-F type cables , which are specially designed for photovoltaic applications.

ZZ-F PV cables   are single-core cables with double insulation, which have the capacity to transport direct current up to  1,800 V  efficiently and with great durability over time.

ZZ-F type PV cables offer great thermal resistance, in addition to great climatic resistance (UV rays, cold, humidity…), which is verified by weather resistance tests. They also have excellent behavior and resistance to fire, which is verified by specific fire tests.

To this end, the materials used for the insulation and sheathing of this type of cable are of high quality, cross-linked, with high mechanical resistance, also resistant to abrasion, flexible and halogen-free.

Likewise, the inner conductor of the PV ZZ-F cables must be tinned, thus conferring greater resistance to possible corrosion by oxidation.

The following table indicates the type of cable to be used in the continuous sections:

 Table 2. Flexible cables type PV ZZ-F Conductor:   Tinned electrolytic copper, class 5 (flexible) according to EN 60228 Insulation:   Halogen-free rubber type EI6. Cover:   Flame-retardant rubber type EM8, halogen-free and with low emission of smoke and corrosive gases in case of fire. Packaging:   Available in rolls with shrink film (lengths of 50 and 100 m) and coils. National/European standards :   UNE-EN 60332-1 / UNE-EN 50267-1 / UNE-EN 50267-2 / UNE-EN 61034 / NFC 32-070 (C2) International Standard:   IEC 60332-1 / IEC 60754-1 / IEC 60754-2 / ​​IEC 61034 Characteristics:

The sections of cables in direct current will be sections composed of two active conductors (positive and negative) plus the protection conductor.

For the calculation of the section ( S ) of conductors in direct current, as is the case of photovoltaic installations, the following formulation will be used:

 S = 2 · L · I ΔU · K

where,

S    is the section of the cable conductor in DC, in  mm 2

L    is the length of the section of conductor being considered, in  m

I    is the intensity of the current flowing through the conductor, in amperes ( A )

ΔU    is the maximum allowable voltage drop in the section, in volts ( V )

K    is the conductivity of the cable conductor ( 56 Cu; 35 Al )

The following table shows the maximum and recommended voltage drop percentages for each section in a photovoltaic installation for direct irrigation:

 Table 3. Percentages of voltage drop (%) Section maximum recommended Panels – Regulator 3% 1% Regulator – Submersible Pump 5% 3%

The attached table shows the cable sections most used in photovoltaic installations of a commercial house, with an indication of the maximum intensity of the cable and its voltage drop in DC:

Table 4. Cable sections and current intensity for direct current cables in photovoltaic installations

The following table is a comparison between the AWG (American Wire Gauge) gauges used in America and the  mm 2  of the Metric System:

 Table 5. AWG – mm 2 conversion table AWG 18 17 16 14 12 10 8 6 4 two 1 1/0 2/0 3/0 mm2 0.75 1.0 1.5 2.5 4.0 6.0 10 16 25 35 fifty 55 70 95

On the other hand, it is recommended that the wiring used complies with the low voltage electrotechnical regulation that is applicable in each country ( REBT 2002 , in the case of Spain) in all the sections of the installation, both in the sections DC (direct) ranging from the photovoltaic generator to its connection to the inverter, as in the alternating current sections from the inverter output to the interior electrical installation of the home.

As already indicated, the direct current sections will be sections made up of two active conductors (positive and negative) plus the protection conductor, while the alternating current sections, which will be of the single-phase type that feeds the interior installation of the house , will be composed of two conductors, phase and neutral, plus another protection conductor.

Thus, for the AC sections downstream of the inverter, copper conductor cables with a double layer of PVC insulation and nominal insulation voltage of  0.6/1 kV will be used . Likewise, these conductors will be housed inside conduits or corrugated PVC tubes on surface mounting on walls and ceilings.

The following table is attached, which indicates the maximum allowable currents for cables according to their section and the nature of their insulation.

Table 6. Admissible currents (A) in air at 40° C. Number of conductors with load and nature of the insulation

On the other hand, the conductor cables will be housed inside rigid PVC tubes or ducts for their protection. These tubes will be installed in surface mounting on the walls and ceiling of the house.

The tubes must have a diameter such that they allow easy accommodation and extraction of the housed cables. For the correct choice of the diameter of the protective tube, the following table will be used. It indicates the minimum outer diameters of the tubes based on the number and section of the conductors that are housed inside.

Table 7. Minimum outer diameters of protective tubes.

The correct choice of the section of the conductor cable is of the utmost importance, since a bad calculation could mean that the intensity that circulates through the cable is greater than the admissible according to its section, which would result in excessive heating of the cable that could damage its insulation and therefore affect the durability of the cable, and in extreme cases, incur a real fire hazard.

The regulatory determination of the section of a cable consists of calculating the minimum normalized section that simultaneously satisfies the following two conditions:

–  Thermal criterion : this condition establishes that the intensity that circulates through the cable is less than the maximum admissible intensity, according to its section. The permissible intensity of each conductor cable can be consulted in tables (see previous table), depending on the section, type of insulation and temperature of the cable.

–  By maximum allowable voltage drop in the conductors : this criterion limits the losses due to voltage drop in the cable. In this sense, as indicated in the IDEA Technical Specifications, for the conductors of the installation where direct current (direct) circulates, the maximum allowed voltage drop will be 1.5%.

The expressions and formulas that provide the way to calculate the minimum sections that the cables must have in each section of the installation are indicated in  section 4.5  of this tutorial.

2.6- Protections

This tutorial will only deal with the necessary protections to install in the continuous part, located before the inverter, in order to be able to detect and eliminate any incident in the installation, thus guaranteeing the protection of connected equipment and people.

In addition to the protections integrated in the inverter, it will be necessary to include the necessary protection devices that carry out the following electrical protection tasks:

Short circuit protection

Overvoltage protection

An overload occurs when there is an excessive current value caused by an insulation fault, a fault or an excessive load demand.

An overload in the cables generates excessive heating of them, which causes their premature damage, reducing their useful life. In addition, an overload that lasts over time and is not resolved can end up causing a short circuit in the installation.

The overload protection devices may be either an omnipolar cut-off automatic switch with a thermal cut-off curve, or a fuse. In the calculation of the installation, object of this tutorial, a fuse has been chosen as a protection element.

But in general, the devices used to protect the installation against overloads must meet the following two conditions:

being,

I n , the rated current of the switch, that is, the rated rating.

I adm , is the maximum allowable intensity of the conductor cable.

And the other condition:

I cd  ≤ 1,45 · I adm

being,

I cd , the current setting (disconnection) of the switch and that ensures the effective operation of the protection device. In fuses it is the melting intensity ( I f ) in  5  seconds.

As in this case fuses are going to be used as protection elements against current overloads, it is also true that  I cd  = I f    and in this case, for the chosen fuses, also that   I f  = 1.60 I n

Therefore, the previous relationship, in the case of fuses as a protection element, would be as follows:

A fuse basically consists of a metal wire or strip inserted in the current circuit that, when a certain intensity is exceeded, melts, causing the disconnection and thus protecting the circuit. Therefore, every fuse will have to be replaced after each short circuit that occurs.

The current rating of a fuse is the value of the continuous current intensity that it can withstand indefinitely. As a general criterion, a fuse is capable of clearing a lack of intensity 5 times the nominal in a time of 0.1s.

When selecting the fuse, the following factors should be taken into account:

Nominal voltage  V n  of the fuse, which must be greater than or equal to the operating voltage of the line where it is installed.

The rated current  I n  of the fuse must be greater than or equal to the maximum current expected on the line where it is installed.

The intensity of tripping or breaking of the fuse will act in less than 0.1 s.

That the maximum short-circuit current that the fuse can withstand is greater than the maximum short-circuit current expected at the point on the line where the fuse is installed.

–  Short circuit protection :

The origin for a short circuit to occur is usually in an incorrect connection or in an insulation fault.

All protective equipment used to limit the incidence of a short circuit must meet the following two conditions:

I 2  t ≤ I cu

being,

I , the firing intensity.

t , is the clearing time (the product    I 2  · t    is usually called step energy).

I cu     is the maximum short-circuit current withstood by the cable, where  I cu  = k 2  · S 2 , where  k  is a correction value for the material of the cable ( 115  for PVC-insulated copper conductor;  143  for insulated copper conductor with XLPE or EPR and  94  for aluminum conductors), and  S  is the section of the conductor in  mm 2 .

PdC ≥ I sc, max

being,

PdC , the breaking capacity of the protection device.

I sc,max     is the maximum expected short-circuit current at the installation point.

In any case, for the protection against short-circuits to be effective, it must be fulfilled that the cut-off time of any short-circuit current that occurs at any point in the installation must not be greater than the time it takes for the conductors to reach their admissible limit temperature.

–  Protection against surges :

Generally, an overvoltage in a photovoltaic installation for self-consumption has its origin in atmospheric discharges (lightning) that occur on the upper parts of the metal structure that supports the panels.

Protection against these phenomena is carried out with devices called autovalves or lightning rods. They are actually current dischargers that offer a reverse type resistance, made of zinc oxide (ZnO) or silicon carbide (SiC), whose value decreases as the voltage applied to it increases.

These devices must be placed as close as possible to the equipment to be protected, so that the excess voltage caused by a lightning discharge can be diverted to earth, in such a way that it absorbs the overvoltages that may occur in the installation and thus avoiding the perforation of the isolates.

3- Starting data

3.1- Location

The house where the photovoltaic solar installation for electricity self-consumption is to be carried out, is located in an isolated rural area, located in the municipality of  Arahal  (province of Seville, Spain), as defined by the following coordinates:

Geographic Coordinates (DMS): 37º 14′ 1” North 5º 32′ 33” West;

UTM coordinates: Zone 30 (274461, 4123814) North;

Decimal Coordinates: 37.2336 Latitude -5.5425 Longitude;

As a utility, the following link is attached where you can find the geographical coordinates of any place in the world.

3.2- Layout of the modules

The layout of the photovoltaic modules, defined by their orientation and inclination, has a decisive impact on their performance. The ideal is to use modules with a tracker that allow the photovoltaic panels to be oriented towards the sun at all times, which guarantees the maximum use of solar radiation. The increase in power delivered by those modules that use a monitoring system with respect to fixed installed panels is estimated at 40%. However, in this tutorial we will use fixed solar modules, much cheaper and simpler to install, for which we will have to define their orientation and inclination so that they are as efficient as possible.

The house has a walkable roof or flat roof, which allows the modules to be given the most convenient orientation and inclination, simply by using auxiliary structures with the appropriate design to support the photovoltaic panels.

The orientation of the solar panels will be such that they are always “looking” towards the terrestrial equator. This assumes south orientation for facilities located in the northern hemisphere of the earth, and north orientation for facilities located in the southern hemisphere. However, deviations of up to  ±20º  from the observer’s equator are permissible without significant performance losses.

Specifically, for installations located in the northern hemisphere, as is the case study in this tutorial, the orientation is defined by the angle called  azimuth  ( α ), which is the angle formed by the projection on the horizontal plane of the normal to the surface of the module and the meridian (orientation south) of the place. It takes the value   for modules facing south,  -90º  for modules facing east,  +90º  for modules facing west.

Figure 16. Definition of the orientation and inclination of the photovoltaic module

On the other hand, the angle of inclination ( β ) is the one formed by the surface of the module with the horizontal plane, as seen in the previous figure. Its value is   for horizontal modules and  90º  if they are vertical.

The value of the inclination of the solar panels with respect to the horizontal, when it is intended that the installation be used all year round with acceptable performance, approximately coincides with the latitude of the place where it is installed. If the installation is mainly used in winter, then the optimal inclination of the modules would be the one obtained by adding  10º to the latitude . And on the contrary, if the installation is going to be used basically in summer, the inclination that would have to be given to the modules would be the result of subtracting  20º from the latitude of the place . Finally, if an optimal design is intended that works for the whole year, the inclination that will have to be provided to the solar panel will be equal to the latitude of the place, as has been said.

On this occasion, it is intended that the installation provide sufficient energy in the months of lower radiation, which in the chosen place ( Arahal, Spain ) is during the winter. Therefore, as indicated above, the final inclination can be between the latitude of the place ( 37º ) and the latitude plus  10º  ( 47º ). Finally, and for constructive ease of the structure that will carry the modules, an inclination of  45º will be chosen .

In summary, the final layout of the modules will be as indicated in the following table:

 Table 8. Tilt orientation of the solar modules South Orientation ( Azimuth, α ) Tilt ( β ) 0º 45º

In other cases, the arrangement of the solar panels (orientation and inclination) may be more restricted or even predetermined (for example, when the panels are placed adopting the slope of the roofs of those houses with sloping roofs, adopting the orientation and inclination that have these).

In these cases, it will be necessary to calculate the losses incurred because the orientation and inclination of the panel is different from the optimum. For this, it is recommended to consult the Technical Specifications of the IDAE ( Institute for Energy Diversification and Saving ), whose document, in its Annex II, includes how to calculate said losses.

3.3- Estimation of consumption

If information is available about the number and operating regime of the electrical appliances that the home will usually have, a very approximate estimate of energy consumption could be obtained, by means of the product of the nominal powers of each appliance by the hours of operation. forecasts of each of them, and subsequently making their sum. It is important to increase the result by at least an additional 30% as a safety factor, in order to also take into account the power peaks that occur when some electrical appliances start up.

If more precise information is not available, tables can be used that present normal consumption ratios for homes, based on regular users, such as the one shown below.

 Table 9. Data on average electricity consumption per year in the home . people per dwelling Average annual electricity consumption KW h 1 1800 two 2700 3 3500 4 4150 5 4900 Standard annual consumption 3500 KW · h

For the purposes of this tutorial, the installation will be designed for an estimated  annual consumption  of   3500 kW·h .

The previous value does not take into account the localized losses in the components and equipment located between the solar generators and the interior electrical installation of the house, that is, the regulating device, the batteries and the inverter or current converter.

The yields considered for each of the above devices will be indicated below. These values ​​considered here must be verified once the real models of devices to be installed have been selected.

Regulatory efficiency,  η REG  = 0.95 ;

Battery performance,  η BAT  = 0.94 ;

Investment return,  η INV  = 0.96 ;

Taking into account the above yields, the estimated annual consumption ( C ea ) will be:

C ea  = 3500 / (0.95 · 0.94 · 0.96) = 4082.68 kW · h.

Considering  365  days a year, the estimated daily consumption ( C ed ) would be:

Ced = 11,185 kW·h.

Another way to provide consumption is to express it in Ampere-hours per day ( Q Ah ). In this case, the expression that provides the consumption would be the following:

 Ced Q Ah  = V BAT

Being,  V BAT , the working voltage of the storage battery, in this case, and according to table 1 of section 2.3, value  24 Volts .

Substituting, we have the following consumption:

 11185 W·h Q Ah  = ————— = 466 Ah/day 24V

Knowing the solar radiation that occurs in the place where the installation is going to be carried out is decisive, both to know the available energy and to analyze the behavior of the system components.

The terms irradiance and irradiance are commonly used to define the available solar radiation. Irradiance ( W h/m 2 ) is defined as the incident energy per unit area during a certain period of time, while irradiance ( W/m 2 ) refers to the instantaneous power received per unit area, or in other words, the incident energy per unit area and unit of time.

For the design of photovoltaic installations, and in order to be able to evaluate the energy that the installation can produce in each month of the year, the concept of number of  hours of peak sun  ( HSP ) of the place in question is defined, and which represents the hours of sunshine available at a hypothetical constant solar irradiance of  1000 W/m 2 .

In this sense, there is a multitude of databases from which information on the solar radiation available anywhere on the planet can be obtained. Attached are some links that provide values ​​of solar radiation:

>>   PVGIS, Photovoltaic Geographical Information System – Europa

For the specific case of this tutorial, the PVGIS database  , Photovoltaic Geographical Information System , will be used to obtain the daily irradiation values ​​for the location of the chosen place ( Arahal-Spain: 37º 14′ 1” North, 5º 32′ 33” West ), inclination of the surface of the panels ( ß=45º ) and south orientation ( Azimuth, α=0º ), for the month of December, which is the most unfavorable for the place in question, obtaining the following result:

 Table 10. Daily average of global irradiation received per square meter of module Month HSP (kWh/m2) December 4.56

To obtain the complete report, obtained from the PVGIS database, it can be accessed at the following link:

>>   PVGIS estimates of solar electricity generation

4- Calculation of the installation

4.1- Number and connection of solar modules

To calculate the number of solar panels needed to meet the expected electricity demand in the home, the following expression will be used depending on the location and type of solar panel to be installed:

 Ced N mode  = PMP · HSPcrít · PR

being,

C ed , the estimated daily consumption, seen in section 3.3, with a value of  11,185 kW·h .

P MP , is the peak power of the  ISF-255 module  selected in standard measurement conditions (CEM), seen in section 2.1, value  255 W ;

HSP crit , is the value of the peak sun hours of the critical month (in this case December), seen in section 3.4 above, with a value of  4.56 HSP ;

PR , is the ” Performance Ratio ” of the installation or energy performance of the installation, defined as the efficiency of the installation in real working conditions, where the following originated losses are taken into account:

Losses due to power dispersion of the modules

Losses due to temperature increase of photovoltaic cells

Losses due to the accumulation of dirt in the modules

Electrical losses

Reflectance losses

Next, the different previous losses will be assessed in order to be able to estimate the ” Performance Ratio ” ( PR ) of the installation.

–  Losses due to power dispersion of the modules :

The power that the modules can develop is not exactly the same, and therefore neither their intensity nor their maximum power voltage are. In this way, when a generator system made up of several panels or modules connected in series is constituted, this fact induces a loss of power due to the value of the through current intensity being equal to the one with the lowest value. of the panels placed in series.

To minimize this effect, the modules are classified by their intensity, which is usually indicated with a letter engraved by means of an adhesive attached to the frame of a panel, so that similar panels can be chosen when assembling the series during installation. .

On this occasion, and according to what can be consulted in the technical properties catalog supplied by the manufacturer of the selected photovoltaic modules (see section 2.1 of this tutorial), the power tolerance ( %P max ) of the selected module is  0/+ 3% , so the possible losses due to power dispersion can be estimated at  3% .

–  Losses due to temperature increase of the photovoltaic cells :

The performance of photovoltaic modules decreases with the increase in temperature of the panel surface. Being an element exposed to solar radiation continuously, it is necessary that there is good ventilation both on the surface exposed to the sun and on the back of the modules. However, even with good ventilation, there is an increase in the temperature of the surface of the modules with respect to the outside ambient temperature.

For the calculation of the factor that considers the losses due to the increase in panel temperature ( P T ), the following expression is usually used:

PT = KT · (Tc – 25ºC)

being,

K T , the temperature coefficient, measured in  ºC -1 . Generally, this value is given by the manufacturer of the solar panel, although if this data is not provided by the manufacturer, the value of  0.0035 ºC -1 can be taken by default . In this case, it can be extracted from the manufacturer’s catalog that contains the technical information of the plate (see link in section 2.1), where  K T  = 0.0044 ºC -1 .

T c , is the average monthly temperature at which the photovoltaic panels work. To calculate this temperature,  T c , the following expression is usually used:

 (T onc  – 20 ºC) · E T c   = T with  + 800

being,

T amb , the monthly average ambient temperature of the place where the photovoltaic modules will be installed. This is data that can be extracted from the information held by the official meteorology agencies in each country. In this case, for the town of  Arahal  ( Sevilla-Spain ), the place chosen to carry out the installation, the average temperature for the month of December is  11.1ºC .

T onc , is the nominal operating temperature of the cell, defined as the temperature reached by the solar cells when the module is subjected to an irradiance of  800 W/m 2  with spectral distribution  AM 1.5 G , the ambient temperature is  20 °C  and a wind speed of  1 m/s . This data is also supplied by the manufacturer of the solar module, the value in this case being  T onc  = 45ºC .

E , is the average radiation on a sunny day of the month in question, which in this case is  590 W/m 2  for the month of December in the town of Arahal (Seville).

Substituting the values ​​in the previous expression, it turns out that the average monthly temperature ( T c ) at which the photovoltaic panels work, turns out to be:

Tc = 11,1 + 18,4 = 29,5 ºC

Therefore, the factor that considers the losses due to the increase in panel temperature ( P T ) turns out to be:

PT = KT · (Tc – 25 ºC)= 0,0044 · (29,5 – 25)= 0,019

Resulting in losses due to temperature increase of the photovoltaic modules of  1.9% .

–  Losses due to the accumulation of dirt in the modules :

Under normal site conditions and performing corresponding maintenance and cleaning tasks on a regular basis, the photovoltaic panels should not exceed losses of  3% for this concept .

Losses due to partial shading of photovoltaic generators that penalize their electricity production can be estimated at around  4% .

–  Losses due to module degradation :

These losses are due to a natural process of degradation of all silicon cells due to their exposure to solar radiation, which is usually admitted to be around  1% .

–  Electrical losses :

The electrical installation and the connection between modules, and of these with the other components of the photovoltaic installation, must be carried out according to the recommendations contained in the IDEA Technical Specifications  , where it is indicated that the voltage drop may not exceed  3 %  ( 1.5%  for the direct or direct current part and  2%  for the conductors of the alternating current part). Therefore, taking these considerations into account, it is estimated that the electrical losses will be  3% .

–  Reflectance losses :

This type of loss, which refers to the angular effects of reflection on the modules, was estimated by the University of Geneva and should be considered at  2.9% .

Finally, accounting for all the previous losses, the ” Performance Ratio ” ( PR ) or energy performance of the installation is obtained, defined as the efficiency achieved in the installation, and value in this case of:

PR = 100% – 3% – 1.9% – 3% – 4% – 1% – 3% – 2.9% = 81.2%

Therefore, the previous expression at the beginning of this section, which was used to calculate the number of solar panels needed, will turn out to be worth the following:

 Ced N mode  = PMP · HSPcrít · PR

for,

C ed  (estimated daily consumption)=  11185 W h

P MP  (peak power of the selected module)=  255 W

HSP crit  (hours of peak sun)=  4.56 HSP

PR  (performance ratio)=  0,812 .

Therefore, to calculate the number of total modules ( N mod ) it is substituted in the previous expression:

 11185 N mode  = 255 4.56 0.812

resulting,  N mod  = 11.85 → 12

Finally  , 12  photovoltaic  modules will be installed, of the ISF-255 MONOCRYSTALLINE MODULE type, ISOFOTON brand  .

To establish the connection between modules, whether in series or in parallel, taking into account that the selected module, type Monocrystalline ISF-255, from the manufacturer Isofoton, has a voltage at the point of maximum power ( V MP ) of  30.9V , It turns out that the number of necessary panels that will have to be placed in series to reach the working voltage of the system, which is  24 V , as indicated in table 1 of section 2.3, will be given by the following expression:

N series  = 24V / V MP  = 24V / 30.9V = 0.78 → 1

While the number of panels to place in parallel will be calculated using the following expression:

Nparalelo = Nmód,Total / Nserie = 12/1 = 12

Therefore, finally the photovoltaic generator system will consist of  12 branches connected in parallel, with an ISF-255 panel per branch .

At this point, it is worth making a point about an additional function of charge regulators. These devices try to optimize the performance of all photovoltaic installations, seeking the operating point of the installation that coincides with the maximum power reflected in the characteristics curve of the photovoltaic generator.

However, in the event that a regulator is not installed that incorporates the maximum power point monitoring mode in the operation of photovoltaic generators, another criterion must be used, that of Ampere-hours ( Ah ), to calculate the connection. of solar panels.

–  Case b) : Calculation of the number of panels when the installed regulator does not include the monitoring and search of the maximum power point ( regulator without MPP ). Criteria for Ampere-hours :

In this case, it will be the installed battery that sets the working voltage of the system (12, 24, 48 Volts), and the operating point where the solar modules deliver maximum power will rarely be reached.

As seen in section 3.3, the energy consumption expressed in Ampere-hours and per day ( Q Ah ), is expressed as follows:

 Ced Q Ah  = V BAT

being,

C ed   the estimated daily consumption;

V BAT   the working voltage of the storage battery.

As seen in section 3.3, these parameters take the following values:

Ced = 11,185 kW·h

V BAT  = 24V

So substituting in the previous expression:

 11185 W·h Q Ah  = 24V

Resulting in the average daily consumption of:

Q Ah  = 466 Ah/day

In this way, the value of the electric current ( I MPT ) that must be generated by the total number of photovoltaic modules in the solar radiation conditions of the critical month (in this case, December) will be given by the following expression:

 Q Ah IMPT = HSP crite

That substituting the corresponding values ​​in the previous expression:

 466 IMPT = 4.56

Resulting finally, the value of the electric current ( I MPT ) of:.

IMPT = 102,19 A

Being as it has been said, ( I MPT ) the value of the electric current that must be generated by the total of the installed panels.

By this method, the number of panels to place in parallel ( N parallel ) is calculated by dividing the total current ( I MPT ) that the system must generate by the unit current of each panel ( I MP ), obtaining the following:

N parallel  = I MPT  / I MP  = 102.19/8.27 = 12.36

Being ( I ​​MP ) the value of the current at the point of maximum power or peak power of the selected  ISF-255 module , with value  I MP  = 8.27 A  (see section 2.1).

This other method results in the installation of 13 branches in parallel, with one module per branch, in the event that a charge regulator is used that does  NOT  include a maximum power point search and detection function.

However, for this case study, a regulator device will be used that DOES include a monitoring and detection function of the  MPP  (maximum power point), so that the photovoltaic generator system will finally consist of  12  branches connected in parallel, with one panel per branch, as calculated above.

4.2- Calculation of batteries

For the calculation of solar batteries or accumulators, the two important parameters necessary for their dimensioning are the maximum depth of discharge (seasonal and daily) and the number of days of autonomy. In this case, the following values ​​will be taken, depending on the selected battery model:

Maximum Seasonal Discharge Depth,  PD MAX,e  = 75% (0.75)

Maximum Daily Discharge Depth,  PD MAX,d  = 25% (0.25)

Number of days of autonomy,  n = 4 days

For the calculation of the nominal capacity ( C NBAT ) necessary that the batteries must offer, this will be the one that results from the highest value calculated when using the expected daily and seasonal discharges.

On the one hand, considering the maximum daily discharge ( PD MAX,d ), the calculation of the nominal capacity of the battery ( C NBAT ), will be carried out using the following expression:

 Q Ah NBAT C  = PD MAX,d

Which substituting values ​​results in:

 466 NBAT C  = 0.25

Resulting in a nominal battery capacity ( C NBAT ) of:

C NBAT  = 1864 Ah

Mediante la expresión anterior se ha obtenido la capacidad que deben ofrecer como mínimo las baterías de 1864 Ah, para generar la energía por día (QAh = 466 Ah/día) y permitiendo un 25% de descarga máxima diaria (PDMÁX,d = 0,25).

Por otro lado, para calcular el valor de la capacidad nominal de las baterías (CNBAT) en función de la descarga máxima estacional (PDMÁX,e), se utilizará la expresión siguiente:

 QAh · n CNBAT = PDMÁX,e

Que sustituyendo valores resulta:

 466 · 4 CNBAT = 0,75

Resultando una capacidad nominal de la batería (CNBAT) de:

CNBAT = 2485 Ah

En este caso, mediante la expresión anterior ha resultado una capacidad nominal necesaria para las baterías de 2485 Ah para generar la energía diaria (QAh = 466 Ah/día) y disponiendo de una autonomía mínima de 4 días sin sol, y permitiendo en todo caso una descarga máxima del 75%.

Como conclusión, para la selección de las baterías se tomará como valor mínimo de la capacidad el mayor valor obtenido de los anteriores, resultando en este caso CNBAT = 2485 Ah

La batería seleccionada, por tanto, estará compuesta de 12 vasos en serie (necesarios para obtener los 24V finales de tensión de servicio), de la gama de celdas de 2V EcoSafe TS, de la marca EnerSys.

En concreto, se seleccionará la batería Enersys Ecosafemodelo TZS13 (13OPzS), de 2V el vaso y una capacidad de 2640Ah C120, según información técnica del distribuidor comercial de la batería seleccionada.

Para la selección del regulador de carga es necesario calcular cuál será la máxima corriente que deberá soportar, tanto en la entrada como en su salida.

To calculate the maximum input current to the regulator ( I Re ), which comes from the photovoltaic modules, the following expression will be used:

I Re  = 1.25 · I SC  · N parallel

where,

I SC   is the short-circuit current of the selected photovoltaic module ISF-255, with value  I SC  = 8.86 A  (CEM).

N parallel   is the number of solar panel branches arranged in parallel of the photovoltaic generator to be installed, in this case,  12 .

1.25   is a safety factor to prevent occasional damage to the regulator.

Substituting the previous values ​​in the expression for calculating the input current to the regulator ( I Re ), the following result is obtained:

I Re  = 1.25 I SC  N parallel  = 1.25 8.86 12 = 132.9 A

On the other hand, to calculate the maximum expected current at the regulator output ( I Rs ), that is, on the consumption side of the installation inside the home, the following expression will be used:

 1,25 · ( PDC + PAC / ηinv ) IRs = V BAT

being,

P DC   is the power of the loads in direct current (or direct current) that must be supplied.

P AC   is the power of the alternating loads.

η inv   is the return on the inverter, around  96% .

V BAT   the working voltage of the storage battery ( 24V ).

On this occasion, the electrical consumption of the house is carried out only in alternating current, with the expected maximum power consumption ( P AC )  being 2200 W , so the output current of the regulator to be calculated:

 1.25 ( 2200 / 0.96 ) IRs = 24

Resulting,

IRs = 119,4 A

Por lo tanto, el regulador que se seleccione deberá soportar una corriente, como mínimo de 133 Amperios en su entrada y de 120 Amperios en su salida.

El regulador de carga seleccionado es de la marca ATERSAmodelo MPPT-80C, que incluye tecnología de seguimiento del punto de máxima potencia (MPPT), según se puede comprobar en el siguiente enlace al catálogo de especificaciones técnicas del equipo:

>>   Regulador de carga, modelo MPPT-80C, marca ATERSA

Como se puede comprobar de las especificaciones técnicas del regulador seleccionado incluida en el anterior enlace, éste sólo permite una intensidad máxima de entrada (IMÁX,e) de 70 A, mientras que la corriente máxima de entrada (IRe) proveniente de los módulos generadores fotovoltaicos es de 132,9 A, según se ha calculado, por lo que será necesario el empleo de más de un regulador.

El número de reguladores necesarios para instalar vendrá dado por la siguiente expresión:

Nreguladores = IRe / IMÁX,e = 132,9 / 70 = 1,9 → 2

Por lo que serán necesarios la instalación de 2 reguladores del modelo anterior.

En el caso concreto de este tutorial, el generador fotovoltaico diseñado dispone de 12 ramales en paralelo, con 1 módulo cada ramal, por lo que la instalación podrá ser dividida en 2 grupos de 6 ramales cada uno, alimentando cada grupo a un regulador distinto, y conectando después todas las salidas al mismo acumulador solar o baterías, según el siguiente esquema de configuración prevista:

Por último habría que comprobar que los parámetros de diseño del modelo de regulador seleccionado se ajustan a las condiciones de operación previstas:

Según la configuración prevista, cada regulador va a ser alimentado por 6 ramales en paralelo con un módulo fotovoltaico por ramal, por lo que la tensión de operación será igual a la del módulo, que según se puede comprobar en sus especificaciones técnicas del apartado 2.1 es de valor VMP = 30,9 V (CEM), que queda dentro del rango de diseño del regulador.

Tensión máxima en circuito abierto admitida por el regulador MPPT-80C: 140 Vcc máxima

De la misma manera, la tensión a circuito abierto del módulo, según se puede comprobar en sus especificaciones técnicas del apartado 2.1, es de valor VOC = 37,9 V (CEM), que es inferior al máximo de diseño del regulador.

De nuevo, según la configuración prevista, como cada regulador va a ser alimentado por 6 ramales en paralelo con un módulo por ramal, la potencia máxima producida por cada grupo será de: 6 · 255 W = 1530 W, siendo 255W la potencia nominal o máxima del módulo fotovoltaico seleccionado, según se puede comprobar en sus especificaciones técnicas del apartado 2.1.

Por lo tanto, finalmente el regulador-seguidor MPPT-80C seleccionado de la marca ATERSA, resulta válido para la instalación y la configuración prevista, según se muestra en la figura 19 anterior.

4.4- Cálculo del inversor

A la hora de dimensionar el inversor adecuado, además de conocer la tensión de servicio de la batería, como tensión de entrada en continua y de la potencia demandada por las cargas, se hace necesario calcular también la tensión y corriente generada en el punto de máxima potencia de funcionamiento de los paneles solares.

Para el cálculo de la tensión de máxima potencia que ofrece el generador fotovoltaico (VMPtotal), ésta se obtiene multiplicando el valor de la tensión de máxima potencia (VMP) de cada panel por el número de paneles conexionados en serie (Nserie) en cada ramal del generador:

VMPtotal = VMP · Nserie

In this case,  V MP  = 30.9 V  (see characteristics of the selected module in section 2.1) and  N series  = 1  panel per branch, for the configuration obtained (see section 4.1), resulting in:

V MPtotal  = 30.9 1 = 30.9 V

On the other hand, to calculate the current supplied by the photovoltaic generator when it provides maximum power ( I MPtotal ), this will be given by multiplying the maximum current intensity ( I MP ) at the point of maximum power or peak power of the module installed by the number of panels placed in parallel ( N parallel ) or branches, that is,

I MPtotal  = I MP  N parallel

Being in this case,  I MP  = 8.27 A  (see characteristics of the module selected in section 2.1) and  N parallel  = 12  panels or branches, for the configuration obtained (see section 4.1), so the previous expression is:

IMPtotal = 8,27 · 12 = 99,24 A

Regarding the nominal power that the inverter must have, it must be taken into account that it must satisfy the maximum expected power of instantaneous consumption ( P AC ) of  2200 W , which constitutes the consumption of the home, increased by at least  35 %  to take into account the “start-up peaks” generated by some household appliances, such as refrigerators or washing machines, which increase their nominal power during start-up. In this case, the nominal power of the inverter ( P inv ) must be calculated by the following expression:

P inv  = 1.35 P AC

For the case at hand, the maximum expected alternating power of the instant consumption loads of the home is  2200 W , so the nominal power of the inverter must be:

P inv  = 1.35 2200 = 2970 W (2970 VA)

The selected inverter that meets the above conditions belongs to the  Tauro range , of the  ATERSA brand , specifically the  3024/V model , as can be verified in the following link that includes the technical specifications catalog of the equipment:

>> DC/AC Inverter-Converter, ATERSA brand, model 3024/V

Finally, it should be noted that different types of inverters can be found on the market, both pure sine wave ( PWM ) and modified sine wave ( MSW ). The latter, although they can power most current appliances, can also have problems with electrical appliances with inductive loads, such as electric motors. Pure sine wave ( PWM ) inverters, however, better describe the waveform provided by the utility grid and are therefore the best choice for powering today’s electrical and electronic equipment. The selected model belonging to the ATERSA Taurus range corresponds to a pure sinusoidal waveform.

4.5- Wiring and protections

For the calculation of the sections of the conductor cables and the protections, a distinction will be made between the part of the installation that works in direct current (direct) and the part of the installation that works in alternating current.

Each of the sections that make up the installation will have a different section of conductors because the current intensity that circulates through each of them will be different depending on the equipment that they interconnect.

A)  Installation in direct or direct current (CC / DC) :

All the direct current sections will be made up of two active conductors (positive and negative) in copper cable with  0.6/1 kV insulation and PVC  sheath  .

For the calculation of the cable section ( S ) in the different sections where the direct current circulates, and which includes from the terminal output in the connection box of the photovoltaic modules to the input in the inverter, it will be used the following equation:

 2 · L · I S = ΔV · C

where,

S   is the section of the conductor cable, in  mm 2 .

L   is the length of the conductor cable in that section, in  m .

I   is the maximum current flowing through the conductor,  in A.

ΔV is the maximum voltage drop allowed in the conductors, which, as indicated in the IDAE   Technical Specifications  , must be a maximum of 1.5% in DC conductors  .

C   is the conductivity of the material that forms the conductor, in this case copper, whose conductivity at  20ºC  is  56 m/Ω·mm 2 . For other temperatures, the following table is attached:

 Table 11. Conductivity values ​​of copper-Cu ( m/Ω mm 2 ) with temperature T ( ºC ) 20 C 30 C 40 C 50 C 60 C 70 C 80 C 90 C 56 54 52 fifty 48 47 Four. Five 44

For those other cases where aluminum (Al) conductors are used, the following table of aluminum conductivities with temperature is also attached:

 Table 12. Aluminum-Al conductivity values ​​( m/Ω·mm 2 ) with temperature T ( ºC ) 20 C 30 C 40 C 50 C 60 C 70 C 80 C 90 C 35 3. 4 32 31 30 29 28 27

As has been said previously, in the different continuous sections, each section will be made up of two conductors, one positive and the other negative, which will have the same section as the one resulting from the calculation of applying the previous expression.

Next, the cable sections of each of the different sections that make up the continuous photovoltaic installation are calculated.

–  Section Connection to the Regulator :

This section of wiring includes the connection from the output of the group box of 6 photovoltaic modules connected in parallel, to the input of the charge regulator.

The values ​​of the different parameters that will be used to calculate the minimum section of the conductor cable will be the following:

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L = 5 m , is the length of the cable from the output of the photovoltaic generator to the charge regulator;

I = 6· I SC  = 6·8.86= 53.16 A , corresponds to the maximum current that can flow through the section, and which coincides with the short-circuit current ( I SC ) of the selected ISF-255 module  , with value  I SC  = 8.86 A , and multiplied by the number of modules (being in parallel, the currents are added) that make up the group that feeds each regulator ( 6 ).

ΔV = 0.46V , which corresponds to the maximum voltage drop allowed in the conductors, which, as indicated in the IDAE Technical Specifications  , must be a maximum of  1.5%  in DC conductors. Indeed, as the working voltage in each group of photovoltaic generators that feeds each regulator is equal to the voltage at the point of maximum power or peak power of each module (since the modules are connected in parallel in the group, the supply voltage output of the group is equal to that of each module). As the module to be installed is the  ISF-255 , with a service voltage value of  V MP  = 30.9 V , the maximum voltage drop of 1.5% will be equal to ΔV = 0,015·30,9 = 0,46 V.

C = 47 m/Ω·mm 2 , which is the conductivity of copper, for a cable service temperature of  70 ºC .

These values ​​substituted in the previous expression result in a minimum cable section of:

S = 24,59 mm2.

The normalized section greater than the calculated one is  25 mm 2 , as indicated in the table ” Admissible currents (A) in air at 40° C. Number of conductors with load and nature of the insulation “, in section 2.5.

According to the table above, the maximum admissible current for 25 mm 2 copper cable of   the 0.6/1 kV type and PVC insulation, installed inside surface-mounted tubes, is  84 A.

A reduction coefficient of  0.91  per temperature must be applied to the previous value, since the previous value is for a cable temperature of 40 ºC, and yet the cable will reach a higher temperature when it is in service. Therefore, finally, the maximum allowable intensity of the cable will be  I adm  = 84·0.91 = 76.44 A.

On the other hand, along the section that connects the group of 6 modules with the regulator, a maximum current will flow equal to the sum of the short-circuit currents ( I SC ) of the modules that make up said group. Therefore, the maximum current that can flow through this section will be  I = 6 I SC  = 6 8.86 = 53.16 A , where  I SC  = 8.86 A is  the value of the short-circuit current of the  ISF -module. 255  selected (see section 2.1)

Therefore, as the current flowing through the section ( I = 53.16 A ) is less than the maximum allowable that the cable can withstand ( I adm  = 76.44 A ), the section chosen for the conductor in this section of  25 mm 2  is valid.

In the same way as the previous one, the cable sections for the remaining continuous sections that constitute the photovoltaic installation would be calculated. In order not to lengthen the presentation of this tutorial, the following table is attached with the results obtained:

 Table 13. Current intensities and cable sections in DC sections Section Section length ( m ) Current intensity of the section ( A ) Minimum calculated cable section ( mm 2 ) Selected cable section ( mm 2 ) Connection with Regulator 5.0 53.16 24.59 25 Connection with Batteries 6.0 106.32 59.01 70 Inverter Connection 12.0 13.58 15.07 25

For a better understanding by the reader of the previous table, it is explained below how the calculation of the maximum current intensities that can circulate has been carried out, both through the section that connects the regulator with the batteries, and the other section that connect with inverter:

–  Battery connection section : the maximum current intensity of the connection section to the batteries will be equal to the sum of the short-circuit currents ( I SC ) of the 12 modules in parallel that make up the photovoltaic generator.

Therefore,  I = 12· I SC  = 12·8.86 = 106.32 A will result , as has been included in the previous table.

–  Connection section to the inverter : on the contrary, for the calculation of the maximum current flowing through the input to the inverter, this will depend on the maximum alternating power ( P ) that the inverter can deliver to the loads it supplies and of its performance ( η inv  = 0.96 ).

 P Ica = V · cosφ

donde,

Ica  es la intensidad de corriente alterna de salida del inversor.

P  es la potencia en alterna máxima que puede entregar el inversor seleccionado a su salida, que vale P=3000 W.

V  es la tensión de línea de la red interior de la vivienda, que coincidirá con la tensión nominal de salida del inversor, en este caso V=230 V.

cosφ  es el factor de potencia que, según el Pliego de Condiciones Tecnicas del IDAE, dicho factor de potencia proporcionado por las instalaciones solares fotovoltaicas deberá ser igual a la unidad (1).

Substituting in the previous expression will result in an alternating current output of the inverter of value  I ca  = 13.04 A .

Therefore, the intensity in direct current ( I cc ) that feeds the input of the inverter will be given by the following expression:

 i ca I cc  = ηinv

being ( η inv  = 0.96 ) the performance of the inverter.

Therefore, the intensity in direct current that circulates through the section that feeds the inverter will be calculated as:

 13.04 I cc  = 0.96

Resulting,

Icc = 13,58 A

As it has been included in the table above.

Finally, it could also be verified that through the cable sections of each section ( 70 mm 2 for the section that connects with the batteries, and 25 mm 2  cable   for the section that connects with the inverter) a current intensity circulates that is less than its maximum allowable current intensity.

In fact, according to table 2 ” Admissible currents (A) in air at 40° C. Number of conductors with load and nature of the insulation “, in section 2.5, the maximum allowable current for the 70 mm 2 copper cable   is  160 A , and for the  25 mm 2 cable  of  84 A .

A reduction coefficient of  0.91 will have to be applied to the previous value  due to the temperature of the cable, so that finally the maximum permissible intensity of the cable will be  I adm  = 160 0.91 = 145.6 A , for the cable of 70 mm 2 copper   and  I adm  = 84 0.91 = 76.44 A , for the  25 mm 2 copper cable , being in all cases higher than the maximum possible intensity that can circulate through each section, according to indicated in the following table:

 Table 14. Current intensities and cable sections in DC sections Section Cable section ( mm 2 ) Maximum admissible current ( A ) Current intensity of the section ( A ) Connection with Regulator 25 76.44 53.16 Connection with Batteries 70 145.6 106.32 Inverter Connection 25 76.44 13.58

–  Protection wiring :

For the protection and safety of the installation itself, an additional cable must be installed, in addition to the active cables (positive and negative), which will be the protection cable and will serve to connect all the metallic masses of the installation with the ground, with the aim of preventing dangerous potential differences from appearing, and at the same time allowing fault currents or those due to discharges of atmospheric origin to be discharged to ground.

The protection cable will be made of the same material as the active conductors used in the installation, in this case copper, and will be housed in the same conduit as the active conductors. The section that the protection conductor must have in each section is given by the following table:

 Table 15. Relationship between protection and active conductors Section of the active conductors of the installation,     S  ( mm 2 ) Minimum section of protective conductors,     S p  ( mm 2 ) S ≤ 16 Sp = S 16 < S ≤ 35 S p  = 16 S > 35 Sp = S/2

For the case in this tutorial, and using the table 11 above, the section that will have the protection cable in each section of the installation is indicated in the following table:

 Table 16. Sections of active conductors and protection by sections Stretch Active cable section ( mm 2 ) Protection cable section, ( mm 2 ) Regulator Connection 25 16 Battery Connection 70 35 Connection with inverter 25 16

–  Protective pipes or ducts :

For the selection of the diameters of the protective tubes the table 3 of section 2.5 will be used, which provides the minimum outer diameters of the tubes according to the number and the section of the cables housed.

For the case in this tutorial, and using the table 3 above, the diameter of the tube in each section of the installation is indicated in the following table:

 Table 17. Protective tube diameters in sections of direct current (DC) Stretch Tube Diameter ( mm ) Regulator Connection 32 Battery Connection fifty Connection with inverter 32

Finally, the following summary table of the sections of the installation operating in direct current is attached, with the results obtained:

 Table 18. Cable sections and diameters of the protective tubes in DC sections Stretch Active cable section, ( mm 2 ) Protection cable section, ( mm 2 ) Protective tube diameter, ( mm ) Regulator Connection 25 16 32 Battery Connection 70 35 fifty Connection with inverter 25 16 32

B)  Installation in alternating current (AC) :

From the output of the inverter, all sections of alternating current that feeds the interior installation of the house, which will be single-phase, will be composed of two conductors (phase and neutral), in addition to the protective conductor, in cable Copper with nominal voltage  0.6 / 1 kV  and PVC insulator.

For the calculation of the section ( S ) of the active conductors in the single-phase alternating current sections, the following equation will be used:

 2 · P · L S = ΔV · C · V

where,

S    is the section of the conductor cable, in  mm 2 .

P    is the maximum power that will carry the cable in  W .

L   es la longitud del cable conductor en ese tramo, en m.

ΔV   es la caída de tensión máxima permitida en los conductores, que según se indica en el Pliego de Condiciones Técnicas del IDAE, deberá ser en los conductores de alterna como máximo del 2%.

C   es la conductividad del material que forma el conductor, en este caso cobre, cuya conductividad a 20ºC es de 56 m/Ω·mm2. Para otras temperaturas se puede consultar la tabla 7 anterior.

V   es la tensión de línea de la red interior de la vivienda, en Voltios (V).

Para el caso de este tutorial, sólo se va a calcular el tramo de instalación en alterna desde la salida del inversor hasta su conexión con el cuadro general de protección y mando (CGPM), donde están instalados los distintos magnetotérmicos, diferencial e interruptores de corte de la instalación interior de la vivienda.

Los valores que definen el tramo de línea desde la salida del inversor hasta el cuadro general de protección y mando (CGPM) de la vivienda, son los siguientes:

P   es la potencia máxima que vaya a transportar el cable y que va a consumir la vivienda. Coincide con la potencia alterna máxima que puede entregar el inversor que se ha seleccionado a su salida, y que vale P=3000 W.

L   es la longitud del cable que va desde el inversor hasta el CGPM, y que en esta ocasión vale L=10 m.

V   es la tensión de línea de la red interior de la vivienda, que coincidirá con la tensión nominal de salida del inversor, en este caso V=230 V.

ΔV   es la caída de tensión máxima permitida en los conductores, que según se indica en el Pliego de Condiciones Técnicas del IDAE, deberá ser en los conductores de alterna como máximo del 2%, por tanto ΔV=0,02·230= 4,6 V.

C=47 m/Ω·mm2   que es la conductividad del cobre, para una temperatura del cable en servicio de 70 ºC (según tabla 7).

Estos valores sustituidos en la expresión anterior resulta una sección mínima de cable de:

S = 1,21 mm2.

No obstante, antes de seleccionar cualquier sección, es necesario comprobar que la intensidad admisible (Iadm) del cable que se coloque va a ser superior a la intensidad de corriente (I) que pase por dicho tramo.

La intensidad de corriente (I) que circulará desde el inversor hasta la entrada al cuadro general de la vivienda, vendrá dado por la siguiente expresión, válida para corriente alterna monofásica:

 P I = V · cosφ

donde,

P   es la potencia máxima a transportar por el cable y consumida por la vivienda. Coincide, como se ha visto, con la potencia en alterna máxima que puede entregar el inversor seleccionado a su salida, que vale P=3000 W.

V   es la tensión de línea de la red interior de la vivienda, que coincidirá con la tensión nominal de salida del inversor, en este caso V=230 V.

cosφ   es el factor de potencia, que según el Pliego de Condiciones Tecnicas del IDAE, para las instalaciones solares fotovoltaicas deberá ser igual a la unidad (1).

Por lo tanto, la máxima intensidad (I) que circulará por el tramo será de:

I = 13,04 A

Finalmente, para soportar este valor de corriente y según la tabla 2 anterior del apartado 2.5, se elegirá una sección de cable de 6 mm2, cuya intensidad máxima admisible es de 36 A.

A reduction coefficient of  0.91 must be applied to the previous value  due to the temperature of the cable, so that finally the maximum allowable intensity of the cable will be  I adm  = 36 0.91 = 32.76 A , still higher than the maximum intensity that can circulate through the section.

On the other hand, the section of the protection cable for this study section, and according to table 11 above, should also be  6 mm 2 .

Finally, and according to Table 3, which indicates the minimum diameters of the protective tubes based on the number and section of the cables housed, this must be  32 mm .

The following summary table is attached for the section in alternating current from the output of the inverter to the entrance to the interior installation of the house:

 Table 19. Cable sections and diameters of the protective tubes in AC sections Section Length of the section, ( m. ) Active cable section, ( mm 2 ) Protection cable, ( mm 2 ) Protective tube diameter, ( mm ) Investor – GFCM 10.0 6 6 32

–  Choice of protection elements: Fuses

For protection against overcurrents caused by overloads or short circuits, fuses will be used. In this case, gPV 1000V DC type blade fuse cartridges will be chosen   for specific use in photovoltaic installations, of the  DF Electric brand , which provide adequate protection against overloads and short circuits in accordance with the IEC 60269-6 standard, and with a minimum fusion current of  1.35 I n , capable of interrupting the flow of all currents ranging from its nominal intensity value ( I n ) to its assigned breaking capacity.

Let us remember from section 2.6 above, that for the selected fuse to be effective, it must be fulfilled that:

being,

Ib   la intensidad de corriente que recorre la línea.

 Tramo Ib In (asignado) 0,9·Iadm Conexión con Regulador 53,16 A 63 A 75,6 A Conexión con Baterías 106,32 A 125 A 144 A Conexión con Inversor 13,58 A 63 A 75,6 A

Finally, the following table shows the characteristics of the gPV 1000V DC blade fuse cartridges   that have been selected for each of the continuous sections of the photovoltaic system:

 Stretch Nominal intensity,  I n Rated voltage,  V n Cutting power Regulator Connection 63 A 1000 V 30 kA Battery Connection 125 A 1000 V 30 kA Connection with inverter 63 A 1000 V 30 kA