So in this article we will try to tell you what a solar power plant (SPP) is and what they consist of, what options there are and how much they approximately cost.
For example, let’s consider a solar power plant for a private home, as this is the most common use of it among residents of Canada.
What does a solar power plant consist of
The most typical solar power plant consists of 4 main components:
- Solar panel;
- Charge controller;
- Battery;
- The inverter.
Below is a schematic drawing of a solar power plant showing how all components of the system are connected to each other.
Connecting and protective equipment is not yet taken into account, we will tell them in a separate article.
Now let’s take a closer look at each of the components of the solar power plant.
Solar panels
Solar panels, also known as solar cells – this is probably the most key component of solar power plants. The main task of solar panels is to convert solar energy into electrical energy.
Power rating
The solar panel itself consists of crystalline silicon cells, also called solar cells. The number of such solar cells determines the rated power of the solar panel. Thus, solar panels come in power 100, 150, 200, 250, 300W. There are other ratings, but these are the most popular. So, a 300W solar panel, here 300W is the maximum power a solar panel can produce. Ideally, in one hour the output of such a solar panel would be 300W*h.
Below are a few options for solar panels, by clicking on each of them, you can look at the detailed characteristics and high-resolution photographs:
Electricity Generation
The electricity production of a solar panel is highly dependent on external factors. In fact, the stated power rating can only be achieved under ideal conditions when the sun’s rays strike the surface of the solar panel at right angles. Also, the production of electricity depends on the intensity of the solar radiation itself. In Canada, the intensity of solar radiation peaks in June-July. When weather conditions are unfavorable, such as cloudy, rainy or just cloudy weather, electricity production decreases. Less sun, less electricity generation.
For example, below is a graph of the electricity production of four polycrystalline solar panels with a capacity of 250 watts each. You can see that the peak production is in the period from May to July, in these months will be generated up to 5 kWh of energy per day. The minimum is between November and January. In the winter months, the generation in general can decrease by 10-15 times compared to the summer period.
The graph is based on the location of solar panels in Kazan with an angle of inclination ~ 50 ° with orientation to the south.
In addition to power, solar panels also differ in nominal operating voltage.
- up to 200 W – 12 volt
- from 200 W (inclusive) – 24 volt
- The nominal voltage of the solar panels is necessary to know for the correct selection of the other components of the system.
Monocrystal, polycrystal
As written above, solar panel cells are made of crystalline silicon, only silicon itself also comes in different types:
- Monocrystalline. The highest efficiency (efficiency), costs a little more.
- Polycrystalline. Efficiency is less (usually 1-2%) than monocrystalline, but they are cheaper.
- There is an opinion that polycrystalline solar panels are better suited to climates with private cloudy or cloudy weather, supposedly they better absorb diffuse light, but clearly this is not noticed. If there is such an effect, it is quite insignificant.
H3 – Connecting Solar Panels
To increase the capacity of solar panels connected in an array, for example, 4 solar panels rated at 250W can give a total power of 1 kW. Solar panels can be connected together in 3 different ways:
- Parallel connection. In this type of connection, the nominal voltage of 4 connected solar panels will remain 24 volts, the current increases by 4 times.
- In series connection. Here, on the contrary, the nominal voltage will quadruple to 96 volts, while the current value will remain at the level corresponding to a single panel.
- Parallel-Serial Connection. If you connect two pairs of solar panels in series in parallel, the nominal voltage will be 48 volts and the current will double.
Which type of connection should be used in this or that case depends mainly on the peripheral equipment, namely the charge controller, inverter and the planned number of batteries.
That’s all about the solar panels for now, then we move on to the charge controllers.
Charge Controller
The charge controller is an intermediate but very important link between the solar panels and the batteries, it essentially controls the flow of energy from the former to the latter, i.e. controls the process of charging the battery, protects it from overcharging and boiling.
To better understand why the charge controller is needed, let’s consider a very simple solar power plant consisting of one 150W monocrystalline solar panel, one charge controller and one battery.
The panel of 150W, as was written above, its nominal voltage is 12 volts, but it has another important parameter as operating voltage and it is Vmp~17.6V, as well as the no-load voltage Voc=21.7V, this voltage is given by the solar panel without a connected load, ie without any consumer. If you try to connect a voltmeter to the + and – terminals of the solar panel, you just get a voltage of ~21.7V. All of these parameters are indicated on a special sticker on the back of the solar panel.
Can you do without a controller
Now what happens if you connect the solar panel directly to the battery? In a very short time it will simply destroy the battery completely, because the allowable voltage at the battery terminals should not exceed ~14V, and the solar panel, as you already know, will give a few volts more. Т
If the battery has been discharged, it will of course charge, but then it will overcharge (not to be confused with recharging, here we are talking about overcharging), followed by boiling. The charge controller prevents all that, maintains the required voltage level on the battery terminals, turns off the charge if the battery is already charged, prevents the battery from discharging at night, because if there is no output, the solar panels themselves can become a consumer. This all adds up to a longer battery life.
Types of Controllers
There are two types of charge controller, MPPT and PWM:
- MPPT ( short for Maximum Power Point Tracking) (eMPATY) Maximum Power Point Tracking;
- PWM (Pulse Width Modulation).
The first are more efficient, but more expensive. PWM controllers are usually installed in low-power solar power plants, with a small number of solar panels.
Batteries
Batteries allow you to store electrical energy generated by solar panels and use it after the sun goes down.
Starter or Automotive
Often there are variations where solar power plant owners use conventional automotive starter lead-acid batteries in their systems. We advise against this because such batteries are not designed for use in standby or autonomous power systems. The main task of such batteries is to produce a high starting current to start the engine, then replenish the spent charge from the generator. The batteries are not designed to be fully discharged. After just a few such cycles they can completely fail and the only thing that can be done with them is to dispose of them.
Deep Discharge
The best batteries for solar applications are deep-discharge batteries. Almost every brand manufacturer offers a special series of deep-discharge batteries, most often produced with AGM and/or GEL technology.
What such batteries are capable of:
- Deep discharge/discharge cycling;
- Low self-discharge current;
- Wide operating temperature range;
- Fully sealed, no acid vapor emission;
- Service life up to 12 years in buffer mode.
Battery Capacity
In addition to manufacturing technology, batteries also differ in capacity, the greater the capacity, the more energy is stored in it. For example, if we consider a battery with a capacity of 100A*h, the stored useful power in it is ~800W, this means that if a load is connected to the system, for example, with a consumption of 150W*h, the battery can work for about 5 hours.
The most commonly used battery in solar power plants for homes is a 200A*h battery. Reserved power in it ~ 1.5kW. By the way, such a battery weighs about 60 kilograms.
Connecting the batteries
To create a system with a large autonomy reserve it is necessary to increase the number of batteries. The connection of batteries can be implemented on the same principle as the solar panels. Which type of connection is used depends on the rated voltage of the charge controller and inverter. For example, if the controller is 24V, the batteries (2 pcs) must be connected in series to also get 24V. If the controller is 12V and there are two batteries, they should be connected in parallel.
There are a lot of nuances with the connection and operation of batteries, we are often asked such questions as, can you increase the capacity of the system by simply adding another battery, can you connect batteries of different capacity, why do you need to use balancers for charging, etc. About all this we will tell in separate articles.
Inverter
Inverter is a device that converts the DC (Direct Current) voltage of batteries into our familiar AC (Alternating Current) voltage ~220V with a frequency of 50 Hz. Without the inverter you can use only constant voltage of 12V, the charge controller has special terminals for this, but if you want to connect household appliances, you can not do without the inverter.
Inverters used in solar energy can be divided into 3 types:
- Standalone inverters. This type of inverter is connected to the battery by terminals. On one side of the body there is a plug for connecting the load. This type of inverter can be used without solar panels, as they are equipped with input ~220V, i.e. they are able to do not only DC / AC conversion, but also work in the opposite direction, namely to charge the battery from 220V. This type of inverter must be paired with a charge controller;
- Hybrid inverters. It is essentially 2 devices in 1 case: a charge controller and an inverter. i.e. there is no need for a separate charge controller to the case of a standalone inverter. Solar panels are connected directly to the inverter, namely to the built-in controller. This type of solar inverter also has the ability to work with the incoming voltage of 220V;
- Mains inverters. Similar to the hybrid inverter, there is also a built-in charge controller, but this inverter works without batteries, all electricity generated by solar panels is converted to 220V and fed to the load, i.e. consumers. Unused electricity through a bi-directional electricity meter is fed into an external (mains) power grid at a green tariff (note, green tariff does not apply in Canada). This type of inverter is most popular in Europe and the United States;
- Below, just below are product cards stand-alone inverter Sib Volt, hybrid inverter SILA and grid inverter Sofar. Each is rated at 3000W. By clicking on the photo you can see detailed specifications, description and photos.
Now you have some idea about the solar power plant, what components it consists of, what characteristics it has and what you need to pay attention to.
