Training course. Part 3 – Solar stations of home and commercial type.

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Solar stations of home and commercial type.

This material is allowed to be used for educational purposes.

A solar power plant is an object for generating electricity through the use of solar energy.

The work of power plants can be carried out in 3 modes:

  • an autonomous mode takes place when the solar power station does not have access to other sources of energy, except for solar radiation;
  • The standby mode of a solar power station is a feature of operation in which the central network is a fundamental source of energy and the solar power station is an auxiliary.
  • The hybrid mode of operation involves a combination of the use of energy from a common network in addition to the energy generated by a solar power plant. This mode of operation is most appropriate when the central network undergoes an overvoltage or malfunctions are observed in it.

The production of electricity using solar power plants is currently quite a popular area in renewable energy. This production allows us to provide consumers with electric energy without reference to a common network, receiving energy from solar radiation and transforming it into alternating current.

The components of a solar power plant include:

  • photovoltaic modules;
  • charge controller;
  • inverter installation;
  • energy storage unit (battery).

The uninterrupted operation of a solar power station is ensured by the operation of all these components as a single system.

Structural Components of solar power plant

Let us consider in more detail the component parts of any solar power plant.

Solar module

The integrated single array of photovoltaic modules is the center of the solar power plant. The array of solar panels fully determines the amount of electricity generated by the solar station.

The solar panel or FEM transforms the energy flux of sunlight into electric current. The efficiency of a conventional photovoltaic module is in the range of 10-35 percent. Advanced models can show efficiency results of 45% and higher.

The principle of operation of the solar power plant, which is based on solar panels, is quite simple and understandable. Photovoltaic modules are combined into a single array, the control of which is carried out by the social block of the solar power plant. A solar battery with a sufficient amount of radiation generates a constant electric current. Thanks to the inverter installation, it is transformed into a variable and supplied to the consumer. The amount of energy produced above the norm accumulates in the battery. Photovoltaic modules are divided into several types. This separation is based on the consideration of silicon compounds in the composition of the panels.

There are three main types:

  •  single-crystal panels;
  •  modules consisting of polycrystals;
  •  amorphous panels.

It should be noted that it is the presence of silicon compounds in the composition of the photovoltaic module that makes it possible to create a “pn” junction. It is this transition that allows you to transform the sun’s rays into electrical energy. 

An important parameter of the efficiency of the solar panel is the material of which it consists. Monocrystalline modules have the longest life and are characterized by a high level of stability. The power of such a solar panel for 5 years is reduced by 5-10 percent. Among the minuses of this type of modules can be distinguished increased fragility and reduced indicators of the mechanical strength of the device. At the same time, the cost of such a photovoltaic module is the highest of all the presented types.

Polycrystalline modules have a lower cost, but at the same time they have a reduced stability of the output power. The efficiency of such modules does not exceed 30 percent.

The latest scientific methods make it possible to produce modules from silicon compounds of amorphous structure. Such modules are called thin-film. The life of such solar panels is about 10 years. The coefficient of performance in this case is 10%. The advantages of amorphous panels are the low price and low weight of the modules.

Charge controller

Charge controller is one of the most important links in the composition of solar power plants, which performs a number of special functions. Firstly, the controller adjusts the voltage, which is an array of photovoltaic panels. Secondly, this device controls the correctness and productivity of the energy storage charge. This allows you to avoid raising or lowering the charge level, save it within the permissible norm.

This device connects the photovoltaic module with an energy storage device.

Functions of the charge controller:

  • the implementation of the connection of the photovoltaic module to charge the battery in automatic mode;
  • the product of the charge of the energy storage unit, including many stages;
  • disabling the photovoltaic module after a full battery charge in automatic mode;
  • in case of exceeding the established norm of the discharge of the battery, the product of shutdown in automatic mode;
  • the product of reconnecting the load in order to charge the battery.

All the above functional features play an important role in the process of preserving the energy storage efficiency and preventing its premature failure, which significantly reduces the cost of servicing a solar power plant. If the battery is recharged on a regular basis, this will lead to boiling of the electrolyte. Accordingly, there will be expansion of the sealed structure of the device. 

The opposite process – an excessively high level of battery discharge, is also dangerous. This process can lead to sulfation of the drive plates and its complete failure. Lead-acid batteries are most susceptible to breakdowns in the event of an uncontrolled charge-discharge. They are most often installed in traditional solar systems.

Varieties of popular charge controllers:

  • a device with pulse-width modulation;
  • device with the search for the maximum power point.

The types of controllers that were used earlier had the ability to disconnect the battery from the photovoltaic module causing a short circuit. For photovoltaic modules that do not tolerate shorting, the use of this type of controller was unacceptable. This significantly limited their scope. 

A device with PWM (pulse width modulation) is characterized by a process sequence that allows you to charge the battery by 100%. 

There are four main stages of the charging process using a similar controller:

  1. The implementation of the main charge. At this stage, the battery is transferred the entire volume of electric current from the module.
  2. The implementation of an absorbing charge. This stage involves maintaining a certain battery level. Thus, the controller eliminates the possibility of increasing the temperature of the drive above the norm and the formation of gases inside the structure. The amount of incoming electric current decreases depending on how charged the drive is.
  3. The implementation of a support charge. At this stage, the controller allows you to save charge after the battery is 100% charged. Also, the incoming current is reduced to avoid overheating.
  4. The implementation of a balancing charge. This stage is only possible for open batteries. When charging, equalization occurs, accompanied by large gas evolution. This process involves the formation of hydrogen and oxygen. To prevent the battery from exploding, provide an adequate level of ventilation and secure the device by placing it away from the source of fire.

Most charge control devices are programmed to use the factory default settings. It is they who regulate the switching of charge-discharge modes. It is best to give preference to controllers that are customizable. In them, you can select a specific battery capacity, charge voltage indicators, which are recommended by the manufacturer of the energy storage device.

Selection of the charge controller is carried out in an individual mode specifically for each solar power plant. In this case, the power parameters of the photovoltaic panels and the load as a whole are taken into account. Before putting the solar panels into operation, you should carefully read the manual and technical description for the most successful selection of the controller.

Battery, solar power is also a very important link. Its function is to accumulate and conserve electricity, which was generated by solar power plant. An autonomous system of solar power plants involves the use of special batteries, the service life of which is the longest. 

Battery

An energy storage device (battery) acts as a buffer that accumulates electricity using the reversibility of chemical reactions. The cyclic mode of operation of the drive is due to the chemical processes occurring in it that provide charge and discharge. The charge process involves passing an electric current in the opposite direction to the discharge process. 

If drives are combined into blocks, then they are characterized as batteries.

The characteristic of energy storage is capacity as the main parameter. This parameter represents the largest allowable charge level that a certain type of drive can withstand. In order to measure the capacity of the drive, it should be discharged for a specified time to the specified voltage indicator. 

Energy storage devices, which are used in various types of power systems, have a number of specific differences with respect to:

  • rated voltage indicators;
  • sizes;
  • capacitive characteristics;
  • types of electrolyte;
  • availability of resource indicators;
  • the speed of the full charge
  • pricing policy;
  • indicators of operating temperatures, etc.

There are certain requirements for energy storage in solar systems:

  1. The battery must have a high cyclicity, that is, withstand as many charge-discharge cycles as possible.
  2. Preference is given to devices having a small self-discharge.
  3. The charge current should be high.
  4. The battery for the photovoltaic system should have a fairly wide range of temperature conditions, within which its effective operation is carried out.
  5. An important aspect is the lack of special requirements for the maintenance of the device.

Taking into account all of the above requirements, deep-discharge energy storage devices have been created that are suitable for different types of electrical supply systems.

For installation on photovoltaic stations, there is a special modification of such batteries called solar. These devices have the highest resource indicators during the work on cycles.

The starter drive in this mode of operation is not effective. Starter batteries do not tolerate deep discharge or low current charge. In addition, they are characterized by an increased level of self-discharge. 

The life of such devices is relatively small. As a standard mode of operation, these devices use a short-term discharge using high current with subsequent restoration of the charge level. Then they are put into standby mode for starting the starter. The battery charge at this time is maximum.

For clarity, you can compare these types of batteries with runners. In this case, the starter drive is a sprinter. A specialized battery is comparable to a marathon athlete.

The most popular at the moment are energy storage devices based on lead-acid. Their popularity is justified by the reduced unit price of 1 kW / h compared to similar devices. Such drives have a higher efficiency and a wider range of operating temperatures. For example, if the performance indicators of a lead-acid storage device are about 80%, then an alkaline storage device has no more than 60 percent according to these parameters. 

Some characteristics of alkaline batteries allow them to exceed lead acid. Firstly, alkaline drives have a longer resource in the duration of operation. Secondly, there is a chance to restore the operation of such a battery due to a change in electrolyte. Thirdly, alkaline batteries can function effectively at low temperatures. At the same time, many parameters of this type of storage devices make them unsuitable for use by photovoltaic stations. Among them:

  • low coefficient of performance;
  • reduced susceptibility to charging with low current.

The final link of the constituent solar power plants is an inverter installation. Inverter is called special equipment for a solar power plant, which transforms direct current into alternating current. In this case, the parameters of the magnitude and frequency of the voltage change. 

The inverter perceives electricity coming from the drive through a special input. The inverter also receives energy that is supplied through the controller from the photovoltaic modules. The main function of the inverter is the conversion of direct current to alternating current. It is alternating current that is used in the future for the energy supply of a residential building or other energy consumption facility. The inverter installation is selected according to the power that is in demand by household appliances. The inverter power in watts is measured. The most popular for use in home solar power stations are inverters with a sinusoidal waveform. In order to meet the energy needs of a residential facility, the performance of the inverter installation should be within 2-4 kilowatts.

Most often, the inverter is presented in the form of a periodic voltage generator. The shape of the inverter installation is close to sinusoidal. Within the photovoltaic station, the inverter acts as one of the central links in the system.

Given the fact that the efficiency of the photovoltaic module is within 30%, the use of an inverter installation with a low efficiency will significantly reduce the efficiency of a solar power plant. This combination makes the work of solar power plant economically inexpedient and unprofitable.

An inverter installation as part of a solar power plant can operate as a single device or be included in the equipment of uninterruptible power supply systems.

Next, we will consider standard types of solar power plants, depending on how they function.

Autonomous solar power plant

A solar power plant characterized by an autonomous mode of operation that does not have a connection to a common electric network is called autonomous. This type of power plant is used in cases where the ability to connect to the power line is absent. Autonomous solar power plants are widely used in remote regions and have become an alternative way to meet the energy needs of residential facilities. Among the obvious advantages of autonomous solar power plants, a significant drawback is the total cost of equipment and installation, the difficulty in calculating the necessary loads.

It should be noted that in case of interruptions in the work of the autonomous solar power plant, it will be impossible to resume energy consumption through the use of a common network. The power of a solar power plant of this kind should be calculated based on the energy consumption of household appliances in a residential facility. This will fully satisfy the energy needs of the house.

An important fact is that an autonomous solar power plant must fully provide the energy needs of a residential building. That is, the entire amount of electricity that household appliances will consume must be generated by photovoltaic panels. At night and in cloudy weather conditions, energy consumption at home will be ensured by the operation of the battery.

The number of photovoltaic panels for an autonomous solar power station should be calculated on the condition that energy should be fully enough for the consumed power of a residential building and the full charge of the battery. In addition to providing energy to residential facilities, such solar power plants can be used to provide power to powerful equipment during repair and construction work in the field.

In order to increase the efficiency and the most productive use of the power plant, it is necessary to develop a clear work plan that allows to increase the performance of the system. For this, the following aspects should be worked out most carefully:

  • required power at a certain time of the day;
  • how much energy a solar power plant can provide at a given time;
  • what power indicators can be provided by the battery;
  • what will be the final price of electricity coming from all structural units of the solar power system.

The backup power supply solar plant

In many settlements remote from large cities, there is not always a satisfactory level of energy supply. Frequent network interruptions force us to look for alternative methods. One of these methods is the power supply system.

This mode of operation does not imply the use of photovoltaic modules on an ongoing basis. The energy storage device (battery) is 100% charged and arrives in standby mode. If in the general network a failure occurs or the voltage does not meet the required parameters, the backup power system is connected. At this moment, the inverter is converting the direct current from the energy storage device into alternating current. 

Uninterrupted power supply becomes possible precisely thanks to such a scheme of work. The capacity of the battery acts as a limitation in this mode of operation. It is this parameter that determines the time of power supply from the backup power system. 

The reserve solar power station operates only in emergency cases when the supply of electricity from the common network becomes impossible. The main aspect of the efficiency of the backup power system is the number of batteries. 

There is a variant of the backup type solar power plant, in which the process of charging the battery is carried out at a time when the photovoltaic module generates excess electricity. To prevent the battery from losing its charge while abstaining from recharging system devices, there is a charge controller. He is involved in the regulation of these processes. 

The function of the controller is to monitor the process of ensuring the set charge level of the energy storage device. This significantly increases the life and productivity of the battery.

Grid type solar power plants

Network solar power plant as a structural component includes a network inverter installation and photovoltaic modules. The inverter is used to carry out the process of direct transformation of direct current received from photovoltaic modules into alternating current. It should be noted that the frequency of the alternating current is 50 Hz, and the voltage is 220 volts. The inverter is connected in parallel to the common network. 

In this case, the generated energy is supplied to the power grid and is used primarily. If the solar panels do not produce enough electricity, then the energy supply of the house is provided by energy from the network. 

Network solar power plant uses the battery only in case of power outages. This advantage significantly reduces the financial investment of the consumer.

It should also be noted that the electricity produced by the photovoltaic modules is supplied to the consumer through an inverter immediately after generation.

The amount of energy produced is directly proportional to the intensity of solar radiation. When a grid solar power station works in tandem with a common grid, the priority is given to electricity produced by photovoltaic panels. This means that with a sufficient amount of insolation, energy from the common network is not used absolutely. If the level of insolation is insufficient to ensure the energy needs of a residential building, then exactly the amount of energy that is missing is supplied from the network.

Basics of building a power plant

The construction of a solar power plant involves the preliminary creation of a program. This approach allows you to create a clear algorithm that will detail each main process in construction.

The most important points of the program will be:

  • territorial coordination, that is, the approval of the area on which the solar power station will be located;
  • creating a safe environment for staff and the operation of the facility as a whole;
  • development of a construction fund;
  • the installation of photovoltaic panels;
  • installation work on the collection of structures;
  • construction work at substations;
  • electrical work on the specified site;
  • connecting the power plant to a common network;
  • testing and starting a solar power plant.

An important aspect in planning the construction of a solar power plant is the price control of the object. A solar power plant project will be considered viable if the costs of its construction are well thought out and reasonable.

It should also be noted that the owners of solar power plants most often resort to the services of a contractor company, which carries out engineering work for the further design and construction of the facility. Warranty obligations within the framework of the agreement between the contractor and the solar power plant owner are provided on photovoltaic panels, a guarantee of the volume of energy production, on the capacity of the solar power plant as a whole.

In addition, during installation, a prerequisite is the quality control of the work performed.

Next, we will consider which format of a solar power plant is most suitable for private home ownership. 

For the energy supply of a residential building and for the sale of energy balances at a green tariff, the most suitable type of solar power plant would be a network.

Often people who are interested in the process of installing solar power plants on the territory of a private house ask themselves what the cost of equipment for a residential building will be, for example, with an area of ​​100 square meters.

It should be noted that the price of equipment is directly dependent not only on living space. In this case, a different calculation method is used.

Before deciding to install a solar power station, the installation site should be inspected by a specialist. Only he will be able to give an opinion on whether the technical conditions of electric networks correspond to the installation of solar modules. The required power is estimated in kilowatts for a specific residential facility.

The maximum allowed power of a home solar power plant is 50 kW. This is the limit that is allowed for purchase in Oblenergo. If the owner of the house decided to install a solar power plant with a capacity of 50 kW, then he must bring a cable of the corresponding capacity to the residential object. In accordance with the specified conditions in the future, all technical parameters are calculated.

The next step in installing a solar power plant is the installation of equipment and the commissioning of a complete system. Only after this, documentary confirmation and drafting of an agreement regarding the supply and sale of electricity to Oblenergo is carried out. Then you need to open a bank account, which will be credited with the proceeds from the sale of surplus electricity.

The last step in this algorithm is to connect the green tariff and make a profit from your home solar power station.

The process of installing a solar power plant, together with the paperwork, can take about 30 days. Timing can be delayed if the nominal power of the energy network of a private house is about 5-10 kW. In this case, the owner of a private house should visit the distribution zone and draw up a statement, on the basis of which the relevant authorities will give permission to install a more powerful cable.

An important factor that interests future owners of solar power plants is the payback period of their investments. In Ukraine, given the level of insolation, these lines can vary from 5 to 7 years.

If a solar power plant with a capacity of 10 kW is installed in a private household, then the payback period will be approximately 6-6.5 years, if the power of the power plant is 30 kW, then the invested funds will be repulsed in 5-5.5 years. 

Regarding revenues from a solar power plant of a private nature, we can say that this amount is in the range of 10,000 hryvnias for 1 month.

It should also be noted that generating electricity just for the purpose of providing energy to your home is not very profitable. Today’s green tariff allows you to sell residual energy into the network at a price that is 6-7 times higher than the price consumed.

The amount of solar radiation most affects the amount of energy produced. For example, if you own a solar power station in Transcarpathia, then the insolation rate will be within 1100 watts. If you install a solar power station in a private house in the Odessa region, then these figures will increase to 1500 watts. The more sunny the region is, the faster the project will pay off.

The period of the highest solar activity, as a rule, begins in the month of May and ends in September. The average value of the volume of electricity generated by a solar power plant during the day is about 90 kilowatt hours.

How many photovoltaic modules are needed for a 30 kilowatt solar power plant?

If we take into account that one solar module has a power of 250 watts, then for such an solar power plant 120 modules are required.

Now the installation of solar modules in apartment buildings is gaining popularity. The only condition for the success of such an event is the presence of a powerful wiring. In addition, when designing a solar station of this type, the roof area of ​​the object is taken into account. Poor roof sizes can be a limiting factor. Photovoltaic modules have different capacities, so if the roof area is small, the installation of more powerful panels in a smaller quantity will be an excellent output.

At the moment, the state provides all kinds of support to owners of home solar power plants. State-owned banks, including Oschadbank, offer customers favorable credit conditions for the purchase of solar power plant equipment. 

Many factors in the architecture of a residential building can become a barrier to the installation of a solar power station. The reason for this may be the complex construction of the roof; orientation of slopes, unsuitable for installing panels; poor shading interference (this may be a chimney, ventilation outlet or window). Despite the above factors, the ability to install a 30-kilowatt solar power station is still present.

Installation becomes possible if there is a site on the territory of the household, the meter of which allows you to install photovoltaic modules on it.

The increased interest in terrestrial solar power plants arises due to the often encountered limited roof area. The average static private residential facility, even having a suitable roof, the total area of ​​which reaches 100 square meters, allows you to install up to 15 kW of rated power. 

If you install photovoltaic modules on the plot, the total capacity of which will be 30 kilowatts, the profit from the sale of electricity will be about 5,000 euros for 12 months. This is provided that the residential facility will consume about 5 hundred kilowatt hours per month. The time it takes for an investment in a home solar power plant to return to its owner is about six years.

Installation of a home solar power station is not a complicated task from a technical point of view. Minimization of time costs, elimination of incorrect calculations and work defects occurs due to the involvement of professional solar installers. 

The most important conditions to be observed when installing a solar power plant on a land plot are the southern orientation of the photovoltaic modules and the exclusion of shading objects. An important factor is the placement of photovoltaic modules. The inability to install the modules in one row can be leveled by careful attention to the plan and the placement of the rows of panels in such a way as to prevent mutual shading. Although this approach will require a larger area, it will provide greater productivity of the solar power plant.

A private solar power plant, with a capacity of 30 kW, averages about 500 square meters. The area also depends on the angle of the modules. 

The complexity of installing a ground or roof power plant is determined by the presence of standard designs. If at the preliminary stage of designing a power plant, which will later be located on a personal plot, the construction was carried out and the necessary calculations of certain loads were carried out, then installation on the ground will take a minimum time. In this case, the design will consist in determining the optimal location of the “tables”, that is, the supporting structures that will directly hold the solar modules. If the installation of solar panels is carried out on the roof of the building, then the location of the photovoltaic modules and the process of compiling a complete set of equipment takes the maximum amount of time. 

When the installation of a ground-based solar power station is carried out using equipment that is not typical, the construction time is delayed, and the process itself is much more complicated.

The installation time of a solar power station on a personal plot is determined by a number of factors: the

  • availability of a detailed plan of the territory;
  • land relief features;
  • the presence of communications that are underground;
  • geological conditions of the regions;
  • preliminary approval of the established location of the supporting structures for photovoltaic modules;
  • establishing the total capacity of a solar power plant.

If the installation of a typical table design is not possible, then some time will be required for the process of developing an individual configuration.

The typical design of a table for installing a solar panel is a special profile. The most suitable material for creating supporting structures is galvanized iron or aluminum. In addition to the weight of the photovoltaic module, a typical load-bearing structure must be designed for additional loads. In the design process, the probability of the influence of snow, rain and strong gusts of wind on the surface of the solar panel is taken into account.

The best option for creating a supporting profile for solar panels is a steel structure. To increase the wear resistance, it is better to process the structure using the hot galvanization method. A thick layer of zinc in this case will not allow the appearance of rust for many years. The galvanizing process will also reliably protect the design slots.

The installation of a private solar power station is as follows:

  • structures and parts are transported to a personal plot, where the installation of a solar power station will take place;
  • components are assembled by type of constructor according to the requirements of project certificates.

The cost of installation work on installing a solar power station

The price of installation work varies within 10% of the total estimate of a solar power station. It should be noted that the quality of the supporting installations directly affects the duration of the solar power plant and the security of financial investments in the future. Professional designers can greatly simplify the installation process and reduce the time of construction work without compromising the quality of the project. Thus, it will be much easier for the performer of installation work on the ground to work according to a previously developed plan than to improvise.

When installing a ground-based solar power station, the foundation is key. As the foundation can be used:

  • ballast structures, consisting of reinforced concrete blocks;
  • traditional foundation made of concrete;
  • a special base made by digging piles from metal into the ground.

From the point of view of speed and manufacturability, the foundation of metal piles is the most suitable. To create such a structure, it is necessary to use special equipment and machinery that will ensure the correct introduction of piles into the ground. The depth at which the pile should be located is about one and a half meters.

The creation of such a foundation with the necessary technological support can take several hours. Further, on this basis, installation of structures can be carried out.

If the option with a concrete foundation was chosen, then the installation work is better to postpone until the next day. Concrete requires a certain hardening time. 

Provided the foundation is ready, installation can take about several days. Such a period of work is possible with standard designs. Installation of supports and installation of photovoltaic modules is fast enough. A separate sector of work with increased responsibility is the installation of inverters and cable connections. It should be noted that these activities can be carried out simultaneously with the installation of solar panels.

Installation of a solar power plant with a capacity of 30 kW can be carried out with the professionalism of workers for 4 days. This process involves a full range of construction work and equipment setup.

If at the preliminary stage high-quality design was carried out, and the preparation for installation work was based on experience and a competent distribution of responsibilities, then the installation of a solar power station will occur as soon as possible and will eliminate the presence of defects.

It is important to note that the efficiency of a solar power plant in a private house can be increased up to 5% due to fixtures with a variable angle. This design feature allows you to change the tilt angle of the solar module seasonally. The owner of the power plant can perform this manipulation independently in the winter and summer.

It should also highlight the system of facade installation of photovoltaic panels. This option is most suitable for those who prefer the competent distribution of the living area of ​​the house. Facade fastening systems are divided into two types: 

  • those that are mounted directly on the building’s facade;
  • those that are attached by hanging structures.

Private solar power plants differ from commercial volumes of generated electricity. If a solar station installed in private households has the main goal – energy supply at home, then for a commercial solar power plant this goal is to profit from the sale of electricity. It should be noted that a private solar power plant also produces electricity in the general grid, only in small quantities.

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