Here you will learn:
- What is a household solar battery?
- Solar battery device
- Types of photocells
- Connection options
- How to connect solar panels to make the most of the capabilities of all elements
- Stages of connecting panels to solar power plant equipment
- Economic feasibility
Solar panel connection diagrams When installing solar power plants, the question inevitably arises: how to connect solar panels and in what order to connect them to the home’s power supply system. Now let's look at everything in detail.
What is a household solar battery?
Solar energy is a real find for obtaining cheap electricity. However, even one solar battery is quite expensive, and in order to organize an effective system you need a considerable number of them. Therefore, many people decide to assemble a solar battery with their own hands. To do this, you need to know how to solder a little, since all the elements of the system are assembled into tracks and then attached to the base.
To understand whether a solar power station is suitable for your needs, you need to understand what a household solar battery is. The device itself consists of:
- solar panels
- controller
- battery
- inverter
If the device is intended for heating a home, the kit will also include:
- tank
- pump
- automation kit
Solar panels are rectangles 1x2 m or 1.8x1.9 m. To provide electricity to a private house with 4 residents, 8 panels (1x2 m) or 5 panels (1.8x1.9 m) are needed. Install the modules on the roof on the sunny side. The roof angle is 45° with the horizontal. There are rotating solar modules. The principle of operation of a solar battery with a rotating mechanism is similar to a stationary one, but the panels rotate following the sun thanks to photosensitive sensors. Their cost is higher, but the efficiency reaches 40%.
The design of standard solar panels is as follows. The photoelectric converter consists of 2 layers n and p type. The n-layer is made on the basis of silicon and phosphorus, which leads to an excess of electrons. The p-layer is made of silicon and boron, resulting in the formation of an excess of positive charges (“holes”). The layers are placed between the electrodes in this order:
- anti-glare coating
- cathode (electrode with a negative charge)
- n-layer
- a thin separating layer that prevents the free transition of charged particles between layers
- p-layer
- anode (electrode with a positive charge)
Photovoltaic modules are produced with polycrystalline and monocrystalline structures. The former are characterized by high efficiency and high cost. The second ones are cheaper, but less effective. The power of polycrystalline ones is enough for lighting/heating a house. Monocrystalline ones are used to generate small portions of electricity (as a backup energy source). There are flexible solar cells based on amorphous silicon. The technology is in the process of modernization, because The efficiency of an amorphous battery does not exceed 5%.
Battery charging controller
The battery charging controller is designed to redistribute the generated electricity. The priority is to keep the battery charged and, when fully charged, to direct the energy to the inverter.
There are two ways to organize charging control:
- PWM (PWM) controller is a device that generates its own measuring pulses with a frequency (about 1 Hz) to monitor the condition of the battery in a wide range of characteristics (pulse wide). Circuit with simple relay logic, i.e. above the voltage on the battery (acid batteries - 16.2 V) - turned off the charging, below - turned it on again.
- An MPPT controller with a processor constantly monitors the position of the maximum power point (MPP) of the solar battery in terms of current and voltage. The other arm of the controller monitors the condition of the battery. The processor compares the data and determines the current and voltage values sent to the battery depending on the charge level.
Both types of controllers provide comfortable battery operation and do not have decisive advantages over each other. The advantage of MPRT is the visibility of its work process and the ability to accumulate information.
Solar battery device
When planning to connect solar panels yourself, you need to have an idea of what elements the system consists of.
Solar panels consist of a set of batteries with photovoltaic cells, the main purpose of which is to convert solar energy into electrical energy. The current strength of the system depends on the intensity of the light: the brighter the radiation, the greater the current generated.
In addition to the solar module, the design of such a power plant includes photoelectric converters - a controller and an inverter, as well as batteries connected to them.
The main structural elements of the system are:
- Solar battery – converts sunlight into electrical energy.
- A battery is a chemical current source that stores generated electricity.
- Charge controller – monitors battery voltage.
- An inverter that converts the direct electrical voltage of the battery into alternating 220V, which is necessary for the functioning of the lighting system and the operation of household appliances.
- Fuses installed between all elements of the system and protecting the system from short circuits.
- Set of MC4 standard connectors.
In addition to the main purpose of the controller - to monitor the battery voltage, the device turns off certain elements as necessary. If the indicator at the battery terminals during the daytime reaches 14 Volts, which indicates they are being overcharged, the controller interrupts charging.
At night, when the battery voltage reaches an extremely low level of 11 Volts, the controller stops the operation of the power plant.
How to avoid common mistakes?
The main errors encountered when connecting solar panels are incorrect connections and reversed polarity . There is only one way to avoid them - do not rush, carefully monitor the progress of work, and if in doubt, do not be lazy to check and clarify the purpose of the contacts or their polarity.
If solar panels are connected to the network, the circuit becomes more complicated, and there is a danger of short circuits or failure of the devices. In such situations, it is recommended to contact specialists who can correctly connect devices and connect solar modules. It will be useful for the user to draw up a wiring diagram for himself and mark the polarity on it. This will help you repeat the assembly later and eliminate errors.
Types of photocells
The main and rather difficult task is to find and buy photoelectric converters. They are silicon wafers that convert solar energy into electricity. Photocells are divided into two types: monocrystalline and polycrystalline. The former are more efficient and have a high efficiency of 20-25%, while the latter are only up to 20%. Polycrystalline solar cells are bright blue and less expensive. And mono can be distinguished by its shape - it is not square, but octagonal, and their price is higher.
If soldering is not very good, then to connect a solar battery with your own hands, it is recommended to purchase ready-made solar cells with conductors. If you are sure that you can solder the elements yourself without damaging the converter, you can purchase a kit in which the conductors are included separately.
Growing crystals for solar cells yourself is a rather specific task, and it is almost impossible to do it at home. Therefore, it is better to buy ready-made photocells.
Selecting a transparent element
The main criteria for choosing a transparent element to create a generator:
- ability to absorb infrared radiation;
- level of refraction of sunlight.
The lower the refractive index, the higher the efficiency the silicon wafers will demonstrate. Plexiglas and plexiglass have the lowest coefficient of light reflection. Polycarbonate also has far from the best performance.
To create frame structures for home solar systems, it is recommended, if possible, to use anti-reflective transparent glass or a special type of polycarbonate with an anti-condensation coating that provides the necessary level of thermal protection.
The best characteristics in terms of absorption of IR radiation have durable thermal-absorbing plexiglass and glass with an IR absorption option. For ordinary glass these figures are significantly lower. The efficiency of IR absorption determines whether the silicon wafers will heat up during operation or not.
If the heating is minimal, the photocells will last a long time and provide stable output. Overheating of the plates will lead to interruptions in operation and rapid failure of individual parts of the system or the entire complex.
Connection options
There are no questions when connecting one panel: minus and plus are connected to the corresponding connectors of the controller. If there are many panels, they can be connected:
- in parallel, i.e. connect the terminals of the same name to each other and obtain a voltage of 12V at the output;
- sequentially, i.e. connect the plus of the first to the minus of the second, and the remaining minus of the first and plus of the second to the controller. The output will be 24 V.
- series-parallel, i.e. use a mixed connection. This means that several groups of batteries are connected to each other. Inside each of them, the panels are connected in parallel, and the groups are connected in series. This output circuit gives the most optimal characteristics.
This video will help you understand in more detail how to connect alternative sources in your home:
Such power plants, using rechargeable batteries, accumulate solar charge for the home and store it, reserving it in battery banks. In America, Japan, and European countries, hybrid power supply is often used.
That is, two circuits operate, one of which serves low-voltage equipment powered by 12 V, the other circuit is responsible for the uninterrupted supply of energy to high-voltage equipment powered by 230 V.
Manufacturing process
In any photo of a homemade solar battery, you can see that the elements are attached to a common housing, which is necessary and reliable protection for the entire structure.
First, a frame of the required size is made from wood or aluminum, and then transparent glass is glued to it using silicone, on which the plates are laid out, keeping a distance of about 5 mm between each. This is done in order to avoid damage due to thermal expansion of the material.
When soldering contacts, it is necessary to take into account that parallel connection of individual elements increases the output current of the battery, and serial connection increases its voltage.
This way you can achieve the required output parameters. It is necessary to evenly include 4 diodes in the electrical circuit to prevent overheating of the elements and their failure.
A simple solar cell circuit should provide an output voltage of up to 19 volts because the battery (12 volts) is charged when connected to a source with a higher voltage than it itself has. At a minimum, you must have a battery of 36 plates.
How to connect solar panels to make the most of the capabilities of all elements
Mixed backup connection scheme. They will depend on the dimensions of the panels themselves and their quantity.
Now there's just a little bit left to do.
With the same characteristics, the next type of panels - thin film - will require a larger area for installation in the house. Of course, at your own risk, you can connect the panel directly and the battery will charge, but such a system must be supervised.
If the house is located in the shade of other buildings, then installing solar panels is only advisable only polycrystalline ones, and then the efficiency will be reduced. In all cases there should be no shadows. Natural airflow of the battery will help solve this problem. All these factors must be taken into account when choosing an installation location and installing panels according to the most convenient option.
Of course, at your own risk, you can connect the panel directly and the battery will charge, but such a system must be supervised. This is interesting: Many of the standard radio components can also generate electricity when exposed to bright light.
At this stage, it is important not to confuse the back of the panel with the front. This is the most important point, since whether the panels are in the shade of other buildings or trees will determine their productivity, and therefore the amount of electricity generated.
When connecting several panels in series, the voltage of all panels will add up. The frame is assembled using bolts with a diameter of 6 and 8 mm. There will be no change in voltage in this case.
A mixed connection scheme is often used. It turns out that properly installed solar panels will work with the same performance in both winter and summer, but under one condition - in clear weather, when the sun gives off the maximum amount of heat. To avoid damage, it is recommended to fasten photocells on the long side, choosing the method individually: bolts are fastened through the holes of the frame, clamps, etc. It can be secured with a thin layer of silicone sealant, but it is better not to use epoxy resin for these purposes, since you can remove the glass if necessary It will be extremely difficult to carry out repair work without damaging the panels.
Solar panels. How to make a cheap and efficient solar power plant.
Stages of connecting panels to solar power plant equipment
Connecting solar panels is a step-by-step process that can be done in different orders. Usually, the modules are connected to each other, then a set of equipment and batteries are assembled, after which the panels are connected to the devices. This is a convenient and safe option that allows you to check the correct connection of all elements before applying voltage. Let's take a closer look at these steps:
To battery
Let's figure out how to connect a solar panel to a battery.
Attention! First of all, it is necessary to clarify that direct connection of the panels to the battery is not used. Uncontrolled energy production is dangerous for batteries and can cause both excessive consumption and overcharging. Both situations are disastrous, as they can permanently damage the battery.
Therefore, a controller must be installed between the photovoltaic cells and batteries to ensure normal charging and energy release. In addition, an inverter is usually installed at the controller output in order to be able to convert the accumulated energy into a standard voltage of 220 V 50 Hz. This is the most successful and efficient scheme, which allows the batteries to give or receive a charge in the optimal mode and not exceed their capabilities.
Before connecting the solar panel to the battery, you need to check the parameters of all system components and make sure they comply. Otherwise, the result may be the loss of one or more devices.
Sometimes a simplified diagram for connecting modules without a controller is used. This option is used in conditions where the current from the panels will certainly not be able to recharge the batteries. Typically this method is used:
- in regions with short daylight hours
- low position of the sun above the horizon
- low-power solar panels that are not capable of providing excess battery charge
When using this method, it is necessary to secure the complex by installing a protective diode. It is placed as close as possible to the batteries and protects them from short circuits. It is not dangerous for the panels, but for the battery it is very dangerous. In addition, if the wires melt, a fire can start, which creates a danger for the entire house and people. Therefore, ensuring reliable protection is the owner’s primary task, which must be completed before putting the kit into operation.
To controller
The second method is often used by owners of private or country houses to create a low-voltage lighting network. They purchase an inexpensive controller and connect solar panels to it. The device is compact, comparable in size to a medium-sized book. It is equipped with three pairs of contacts on the front panel. Solar modules are connected to the first pair of contacts, batteries are connected to the other, and lighting or other low-voltage consumer devices are connected to the third.
First, the first pair of terminals is supplied with 12 or 24 V voltage from the batteries. This is a testing stage; it is needed to determine the functionality of the controller. If the device has correctly determined the amount of battery charge, proceed with the connection.
Important! Solar modules are connected to the second (central) pair of contacts. It is important not to reverse the polarity, otherwise the system will not work.
Low-voltage lamps or other consumer devices powered by 12 (24) V DC are connected to the third pair of contacts. This set cannot be combined with anything else. If you need to provide power to household appliances, you need to assemble a fully functional set of equipment - a private solar power plant.
To the inverter
Let's look at how to connect a solar panel to an inverter.
It is used only to supply standard consumers requiring 220 VAC. The specificity of using the device is such that it has to be connected last - between the battery unit and the end consumers of energy.
The process itself is not difficult at all. The inverter comes with two wires, usually black and red (“-” and “+”). At one end of each wire there is a special plug, at the other there is an alligator clip for connection to the battery terminals. The wires, according to the color indication, are connected to the inverter, then connected to the battery.
About batteries for autonomous systems
Batteries are probably the most expensive and important part of the system, they are very capricious and quickly deteriorate, there are many types of them and they need to be treated with care, otherwise they quickly lose capacity and deteriorate.
That’s why you need to buy a smart controller so that it can be configured for different types, or it should already have pre-installed settings for working with different types of batteries. For example, car starter batteries lose capacity very quickly in autonomous systems, just 1-2 years and they already lose 90% of capacity. This is due to deep discharges, since cheap controllers turn off consumers at 10 volts, and car batteries are not designed for this, so if you use them, do not discharge them more than 110.8-12.0 volts.
Traction batteries are more durable and can be discharged by 80%, but they are more expensive and it is also not advisable to discharge them to 10 volts. There are also, for example, gel batteries that are critical to overcharging. There are many subtleties and it is better to study everything so as not to lose your money. You can read more about lead batteries here - Automotive and traction batteries
Alkaline batteries are very durable, but also very expensive. And if lead batteries have an efficiency of 85-90%, then alkaline batteries are a little inferior here, and if they are operated by charging and discharging with high currents, then their efficiency noticeably deteriorates. Such batteries are not profitable, especially in winter, since there is already little energy coming in, and even the batteries give out 30% less energy than they receive from solar panels. Although now it seems that alkaline batteries with improved efficiency have appeared, the overall picture is the same.
Lithium iron phosphate batteries are the most promising for autonomous systems; they have a high efficiency of 95-98%, and at the same time are not at all afraid of undercharging, deep discharges, and high discharge-charge currents. But they are also expensive and require an additional BMS cell condition monitoring system. If such a battery is charged or discharged below the required level, it irreversibly loses capacity or the cell stops working altogether. But the condition of the battery is monitored by the BMS and it also balances the battery charge, so if something goes wrong, it will protect the battery and turn everything off, and it will not deteriorate.
You can’t describe everything in one article, but I tried to mention and describe the main things so that it would be clear to those who are not at all familiar with this. You can read more in other articles from the section. But in general, at the moment, judging by my experience, it is more profitable to build a small power plant without an inverter and power all electronics from 12 volts, and if everything is transferred to 220 volts, then build a system at 48 volts. Especially in winter, even a little extra energy is very necessary. Also, this winter I have lithium iron phosphate (lifepo4) batteries, and obviously the energy in general is noticeably greater than when using car batteries, plus lifepo4 have not deteriorated at all and there is no loss of capacity, although they have not been charged for a whole month before end and were constantly discharged until shutdown.
Economic feasibility
The payback period for solar panels is easy to calculate. Multiply the daily amount of energy produced per day by the number of days in a year and by the service life of the panels without reducing power - 30 years. The electrical installation discussed above is capable of generating on average from 52 to 100 kWh per day, depending on the length of daylight hours. The average value is about 64 kWh. Thus, in 30 years, the power plant should, in theory, generate 700 thousand kWh. With a single-rate tariff of 3.87 rubles. and the cost of one panel is about 15,000 rubles, the costs will pay off in 4–5 years. But the reality is more prosaic.
The fact is that December values of solar radiation are approximately an order of magnitude lower than the annual average. Therefore, for fully autonomous operation of a power plant in winter, 7–8 times more panels are required than in summer. This significantly increases the investment, but reduces the payback period. The prospect of introducing a “green tariff” looks quite encouraging, but even today it is possible to conclude an agreement for the supply of electricity to the network at a wholesale price that is three times lower than the retail tariff. And even this is enough to profitably sell 7–8 times the surplus of generated electricity in the summer.
Combination of solar energy and stationary network
When planning to use electricity from the sun in parallel with an equipped centralized stationary network, the connection diagram is made slightly different. And the main reason for this decision is that the private consumer does not have the opportunity to “dump” the remaining energy.
And this can provoke voltage surges lasting up to one second.
When combining solar electricity with a stationary centralized network, they are guided by the same rule: the more sources are connected, the more complex the scheme becomes
According to the above diagram, the voltage from the heliofield is first directed towards the battery, and from there it is transmitted to the load.
When designing this installation option, it is worth taking two types of load into account:
- non-redundant – lights in the house, household appliances, etc.;
- redundant – emergency lighting, refrigerator, electric boiler.
Keep in mind: the larger the battery capacity, the longer the backup electrical appliances will work in autonomous mode.
When choosing this method of generating energy into the network, be prepared for the fact that you will have to apply for permission from local power grids.
Despite the fact that inverters for solar panels produce voltage, the quality of which is sometimes higher than that in the centralized network, local power grids do not give the go-ahead for the electric meter to rotate in the opposite direction.
For this reason, according to the scheme, solar inverters stop working when the voltage in the network is lost. And the redundant load begins to be “powered” from the battery.
