The design of a solar power system determines what equipment is needed. The designer must therefore have sufficient knowledge of the necessary equipment to be able to draw up a good plan.
The inverter is one of the most important links in solar designs, and designs are consequently limited by the type, quality and availability of inverters.

The purpose of an inverter is to convert the direct current generated by the solar panels into 50 Hz alternating current provided by the power network, and if you use batteries, to also charge the batteries.
The choice of an inverter is determined by the type of application required and the size of the installation. Inverters are divided into two groups: those that work with high-frequency electronics, and those that work with a transformer (low-frequency).
The transformer type is usually more reliable and is not so easily damaged when things happen outside its parameters, such as short circuits. However, it has a lower energy efficiency than the high frequency types.
Solar power is also used for small applications, such as electric shock wires for controlled grazing by livestock, gates, borehole pumps and fences.

Connected to the national network with solar panels and batteries (full hybrid inverter).

It is a more expensive option that provides for emergency power, as well as an auxiliary generator that is connected to the inverter. The inverter can also return power to the network.
These inverters have several options according to which they can be programmed to deliver power, for example sunlight preference, with replenishment through the network or batteries.
These types of inverters apply size restrictions, but are evolving rapidly and are becoming increasingly available. Inverters of 5-30 kW are available so that up to ten units can be connected in parallel for a joint unit with a delivery capacity of 200 kW.

Connected to the national grid with solar panels and batteries, but the inverter cannot return power to the grid (off grid, semi hybrid). 

This system should also have batteries that can replenish the power as soon as the solar panels can not supply enough.
The system will shut down as soon as the battery voltage drops too low and only turn on again once the batteries have charged enough. An inverter that works independently of the power network with solar panels and batteries and can also be connected to a generator.

The most common solar panel uses silicone crystals that have the ability to flow electricity as a one-way conductor as soon as it absorbs solar energy (photons) (piezoelectric effect).
Silicone material is used in a highly technological process to build an electrical cell that is attached to conductors to form a circuit.
The cells group together to build up the electrical potential of a panel, and this gives rise to the typical pattern of lines (bus bars) that one sees on a solar panel.
It is important to build and seal all these fine veins properly so that they can last for 100,000 hours; about 25-30 years. When the conductors are not properly welded, a small point of higher resistance arises which operates at a higher temperature (hot spot) and can give way.
This causes a dead spot which reduces the delivery potential of the panel. It is difficult for the layman to distinguish a weak panel from a good one.
Various grade panels are available. What makes things even more difficult is that the Chinese are the largest manufacturers and consumers of solar panels in the world.
They will therefore not try to obtain a SABS brand for such a small market as South Africa. Furthermore, the development of solar panels is happening so fast that what was still a good panel last year is already lacking again this year in terms of efficient energy delivery.

This leads to the realization that the ten-year warranty and 25-30 year use expectation set as the norm will only mean something if the manufacturer still exists. The well-known brands therefore take great advantage in the market, but you have to pay a lot for it.
Solar panels are manufactured by companies on a large scale but there are many other, lesser known factories that also make good panels at competitive prices.
Furthermore, solar panels are compared to each other at a standard of 1 000 W per square meter in terms of their output, but this is not an indication of the quality. Many consumers' panels give in after a few years.
The normal attenuation of panels is about 0.68% per year, so that after 20 years the panel can still deliver about 80% of its power, depending on environmental and installation factors.
A panel that vibrates in the wind, for example, will weaken faster due to microcracks that occur in the thin crystal films.

The final choice of the size of a solar panel will first be determined by the type of inverter you are going to use. The panels are connected in series to further increase the electrical potential to form a string, and each type of inverter has its own, required potential against which to operate.
You can therefore not buy a lot of solar panels from someone in good faith and expect it to work with any inverter. The choice of a solar panel supplier is less important than that of the inverter because the standards are much more uniform and there is more competition in the market for the same product.
However, one has to walk lightly to pay a lot for panels that are not necessarily better than other, lesser known brands. Local panel prices are largely affected by changes in the exchange rate and the volumes handled by the importer.
The manufacturer carries the warranty for many years. So make sure it is a level 1 company, which means it is the first link in the supply chain (OEM).
Another issue is the choice between mono- and polycrystalline panels. Due to the rapid development of panel technology, yesterday's mono panel may not be as good as today's poly panel.
The differences become so small that other factors, such as the angle at which the panels are installed, begin to play a larger role.

The most economical battery is the lithium iron phosphate battery, or LiFePO4, with a general usage expectation of about 3,500 cycles. A cycle refers to a complete charging and discharging cycle of one hour each, with a hold time of half an hour before the process is repeated.
As soon as the capacity starts to decrease to 80% of the original capacity of the first charge, the test stops, and it determines its accepted number of cycles over the life of the battery.
The service life of the battery is shortened when it is charged faster than 1 C, in other words the capacity of the battery in one hour.
This is also the case if the battery is discharged faster than its capacity. This can happen if the battery bank is too small for the load to be provided or if the battery is discharged below 10% of its total capacity, which can happen if the inverter's settings are not correct.
The battery life of the battery bank can be greatly extended if the charging and discharging rate is slower. A good rule of thumb is to give the battery bank a four-hour charging or discharging time. It will also stabilize and keep the temperature of the cells low.

Composite cells are usually sold, which then have a built-in control system that protects the cells from too low or too high a voltage. You can also successfully buy the cells separately for larger battery banks, which can save a lot of costs.
Battery systems are available at reasonable prices. As in the case of solar panels, there are many battery dealers in China, but only a few large, original manufacturers.
There is also a large market for second-life cells because the market for electric vehicles is very large, and those battery cells are used again to build, for example, 12 V batteries. One can quickly notice this by looking at the weight and capacity of the battery.
An original battery's capacity is from about 150 Wh / kg and higher, so you can notice when a battery is made up of repackaged cells.
Cost-effective heavy-duty switchgear, such as good-quality switches, fuses, and electronic control, are currently scarce and usually quite expensive. The cheaper products are a risk for long-term use.

A good generator is often the first equipment one acquires for auxiliary power, followed by a solar power system. It is important to calculate what the correct capacity should be for the generator, because diesel emergency power can be very expensive if a heavy load, such as a water pump, has to be pulled for a long time.
The cost of the service must therefore be weighed against the loss if it cannot take place. The size of the generator must be determined according to the necessary load. A diesel generator runs more economically if the load is more than two thirds of the size of the engine.
Otherwise the engine will run too light for its load and will tend to be heavy on fuel, especially if the engine is too small for the load. Most inverters can be automatically connected to generators, provided the generator's control device lends itself to it.
Otherwise, a special control system for the generator must be installed that will understand the inverter instructions. The larger the load, the more diesel the engine has to inject, but the ordinary mechanical diesel pump alone cannot handle this.
A computer-controlled diesel pump is more controllable, provided it communicates correctly with the inverter.

The installation and layout of a solar power system can easily amount to 25% of the total cost, and the electrical layout can quickly become more expensive when the distances become large. Therefore, this part of the project's cost should not be underestimated and carefully planned.
A good plan saves you money, and a bad plan costs money.