How Should a Solar Photovoltaic System Be Designed and Installed?

Photoelectric solar systems are gaining popularity in the world at an enviable speed. The sun’s energy is environmentally friendly is environmentally friendly, renewable, and accessible to every person. It is possible to use solar energy converted into electricity directly: store it on reserved batteries, combine it with a main power supply, and even sell surplus electricity in the grid.

Solar stations are suitable for industrial and residential use. But before installing the station, it is important to deal with the design of a solar photovoltaic system. In the following material, you can find out how the planning of the installation of electrical equipment is and what you need to pay attention to when choosing and connecting the components.

Planning for an Independent Photovoltaic System

The PV system design should start with choosing of a place where it is more profitable to mount the structure. The amount of energy generated differs depending on the climatic characteristics of the region, the duration of daylight hours, and the intensity of solar energy.

The following guidelines will help you not to make a mistake with solar system design:

• roof mounting – universal version requires knowledge of the type of roof, the angle of its inclination, and whether it is possible to achieve an angle of radiation to photoelectric panels of 90°;
• the required area – you need to determine the permissible area for the solar system installation, calculate the right number of panels to cover the necessary energy consumption, and prepare the location of other components;
• remoteness from the house – the longer the wires, the lower the voltage in them. PV design should include routes from the battery and inverter, minimizing the loss of system efficiency;
• shadow accounting – with the design of a photovoltaic system, there should not be green spaces or buildings that will create a shadow and reduce equipment performance.

While creating a solar panel layout, it is necessary to assess the insolation. You can get information about the irradiation of a particular area with solar radiation at the nearest meteorological station.

Considerations for a PV System That Is Independent

Designing a solar power system includes recommendations on the installation method based on the peculiarities of the location of future equipment. Photoelectric modules should be located on stable, strong mounting structures that withstand the necessary weight of all panels and not succumb to corrosion and atmospheric effects for several decades.

If the structures are on the ground, the design of the solar system should take into account special elements that turn the solar panels into automatic mode. The addition of tracking systems in the PV designs increases the cost of solar installation, but the efficiency of the equipment increases significantly.

If the design of the solar station is in the process of developing and integrating into the roof or facade of the structure, existing support and building structures are in use. This reduces the costs of the PV solar system design project itself, installation work, and materials.

The Calculation of the Required Amount of Energy

It is not wise to start designing a solar system without knowing how much energy is needed. When making solar panels layout design, it is important to calculate all electrical appliances, air conditioning, and heating systems, plus add some more power, taking into account the future increase in consumption.

You can calculate the need for energy supply with complete or partial disconnection from the central energy networks by multiplying the rated power of a load of PV solar power system by the duration of its operation (in hours). The result is recorded in the W-h. It is necessary to determine the daily need for electricity by summing up the individual energy consumption of each household appliance.

Source:  www.electricaltechnology.org
Further, the resulting indicator is multiplied by 1.3. This is necessary to consider the energy loss in the system. The resulting number is the essential watt-hours that panels should generate every day.

Solar PV system design should include the worst scenarios when energy demand is at its peak and generation is at its lowest. This is a possible downside of the approach in a tangible increase in the cost of the solar system.

Ratings for the Inverter and the Converter (Charge Controller)

In photovoltaic designs, the “heart” is the inverter. Its selection requires careful attention. Input, output voltage indicators, and rated current are important. The permissible power of the inverter is calculated from the total load connected to the network. The output voltage should withstand the current from the battery and from the load of the system.

The operation of all other devices of the solar station depends on the choice of inverter for photovoltaic system design. Its connection increases the efficiency of the equipment by up to 30%.

The charge controller converts excess voltage from the panels into charge current, which adds 20 to 30% more efficiency to photovoltaic arrays. In solar PV design, the rated voltage of the controller must be calculated within 125% of the short circuit current of the solar panel.

Calculating the Size of the Converter and Charge Controller

Charge controller rating depends on power and voltage. Choosing a device when planning solar system designs, you need to know that the controller must match the voltage of the battery itself and the batteries. Next, you should make sure that the controller has enough power to control the current coming from the solar panels.

The size of the series charger for solar panels system design is determined as follows:

• the Isc (short circuit current) of the solar panel is taken;
• multiplied by 1.3;
• the result is the rating of the controller.

The size of the device also depends on the relative position of the photovoltaic batteries: they can be parallel, series, and mixed. If an MPPT controller is in use in the solar system design, then the calculations will be different, and the formula for determining the size of such a device does not apply.

Inverter Sizing

Inverters in solar power designs are installed to convert DC to AC. The main requirements for the size of the device are as follows:

• the inverter must have a nominal voltage similar to that of the battery;
• the input power cannot exceed the total power of the electrical appliances used;
• in autonomous solar power plants, the size of the inverter must exceed the total load by 25-30%, associated with losses and efficiency problems in the device itself;
• when using compressors or motors, the inverter power must exceed the total power of these devices by three times.

If solar systems design is being developed for solar stations with a grid or those that connect to the grid, the input power rating of the inverter must match the power of the photovoltaic panel. This is a guarantee of productive and safe operation of the system.

The Energy Supplied to the Inverter on a Daily Basis

Each inverter has a certain efficiency. Based on its characteristic, the amount of energy supplied to the inverter must exceed the amount of energy used by the load. This will compensate for the losses in the device.

System Voltage

The voltage supplied to the inverter is called system or common. It consists of the following:

• linear current;
• individual panel voltages;
• power losses in cables;
• indicators of the maximum limit voltage drop.

Home solar system design has a voltage of 12 V and by reducing the current, you can reduce the power and possible current losses in the cables. By increasing the voltage in the solar system you can get a similar result. These methods allow to add additional batteries.

Battery Size and Capacity

The photovoltaic array design uses deep-cycle batteries. Their feature is the ability to discharge to a critically low level without loss of system performance. Batteries do not lose performance when quickly recharged or discharged daily for many years.

It is necessary to take the larger size of batteries for solar designing so that the amount of energy is enough to power all electrical appliances in the dark and in cloudy weather.

Source:  www.electricaltechnology.org

You can calculate the battery size for a solar layout like this:

• calculate the total number of watt-hours consumed by all appliances in 1 day;
• divide the resulting number by 0.85 (these are battery losses);
• once again, divide the result by 0.6 (drop depth);
• divide the answer again by the nominal battery voltage;
• multiply the result obtained by the number of days of autonomous operation of the system.

The number that you get as a result of the calculations is the required battery capacity, measured in ampere-hours.

Size of the Photovoltaic Array

The development of solar array design should take into account that photovoltaic modules, depending on the size, generate different output power. To determine the size of a solar module array, you need to know the total peak power of the equipment. This indicator depends on the geographic location of the solar panel designs and the volume of the module. Solar panel layout drawing must include the energy efficiency of the panels.

You, most probably, won’t have difficulty with the calculation of the optimal size of the models. The calculation is carried out in two steps.

1. Calculate the total peak load needed for solar arrays. To do this, divide the total number of watt-hours that the modules must produce per day by 3.43. The result is the total peak power needed to operate the panels.
2. The required number of panels included in the solar panel array design is calculated. This is done by dividing the total peak load by the number of output load ratings of the available modules. If you get a fractional number, you should round it up to the full. The figure resulting from the calculations will indicate the required number of panels for the solar station.

But these calculations give the minimum number of photovoltaic arrays necessary for the quality functioning of the systems. If solar energy designs consist of more panels than the calculations showed, both the productivity of the station and the operational life of the batteries will increase.

When using fewer panels, there is a risk of reducing the life of the solar system and completely stopping the station in cloudy weather. If you are planning a residential solar system design without grid power, it is important to consider the worst-case scenario when calculating.

Size of the Cables

An important component of photovoltaic panels is electrical wiring. Cables must be carefully selected to withstand the voltage and power produced.

Also, take into account the dimensions of the wires in advance at the stage of PV systems design. Cables must:

• be resistant to ultraviolet rays;
• have waterproof insulation;
• have minimal resistive losses;
• be characterized by a minimum voltage drop.

The disadvantage of wire gauges is that they will result in power loss or short circuits in the system. Exceeding the cross-section is also not recommended. It will not have a positive effect on the operation of the solar installation.

You can correctly determine the required cross-sectional area of the wires by the formula: А = (ρI M L / V D) × 2.

Behind each symbol lies a certain value: ρ – indicates the resistance of the cable material, L – the length of the wire; V D – the number of limit voltage drops; I M is the peak value of the current passing through the wiring.

All these nuances must be taken into account in photovoltaic design in order to exclude possible damage to expensive equipment of solar systems.

Kateryna Ryzha

Kateryna is an experienced writer with a focus in solar energy. She is a specialist in several topics related to energy efficiency, technical applications, renewable energy, and more as a consequence of her extensive reading.