Full energy autonomy or how to survive with solar panels in the outback (part 1. theoretical)

    It all started with the fact that I acquired a plot of land in the village, past which electric wires did not pass. No big deal, I thought. “Indeed, according to the law, they must connect me to the power grid within 6 months from the moment of conclusion of the contract.” If I then knew that I would have to master an autonomous power supply and plunge into the world of solar energy ...


    In the first part I will try to highlight the theoretical justification of my choice and calculations that will facilitate understanding of the volume of investments for building my own energy system.
    In the second part I will describe the practical implementation of my ideas with economic calculations, applied equipment and circuitry of a working power system. I will also describe the advantages, disadvantages and my own mistakes in the completed project.
    In the third, if it comes to it, I’ll talk about plans to integrate an autonomous energy system and a conventional grid in a private house.

    The realization that there was no electricity yet, and that the house was already assembled, came in the spring, when the construction and finishing season began. And if the house was assembled using a rattling gasoline generator, then it is impossible to live with such a rattle in the village, and it is unprofitable to drive a 2.5 kW gas generator for the sake of a drill or a pair of bulbs. It is very easy to deduce the first rule here: a gas generator is needed in the village , if there is a need for power supply at any time. Networks are unstable and no one will repair them in the first minutes after a failure. The second rule: the generator must run on the same type of fuellike the car. If the fuel runs out suddenly, you can drain from the car, and if the tank in the car is dry, then you can carry out the reverse procedure.

    If you look at the left corner, you can see how the generator works for the sake of one drill and a radio receiver. After this picture, thoughts began to creep in that electricity was needed not so much, but often. For example, in the evening you need to light a house, which requires about 100 watts of energy. Thoughts about buying a second, low-power gas generator, but were noted for a number of reasons: rumble, maintenance, mechanics, and therefore wear and tear, sooner or later, failure. We needed something autonomous, simple, reliable.

    Having studied the forum of car dealers, having reread hundreds of branches and learning to distinguish a single crystal from a polycrystal, it was decided to use solar energy for the benefit of a particular house. Indeed, there are a lot of reports on Habr how another cellular company in a remote region spent a lot of rubles and was able to save even more, but here everything is clear, with your own hands and by example.

    Let's move on to the theory. The main thing that a house will have to struggle with an autonomous energy system (hereinafter autonomous) is the desire of all households to include kettles, irons, microwaves, and other household appliances that use crazy kilowatts of energy. For hair dryers and irons, you can start the electric generator.


    So, the first thing you need to exclude most of the electrical appliances that we use in everyday life: electric kettles, electric stoves and more. Any gas stove and gas cylinder that can be refueled at almost any gas station will be replaced. So, we cook and heat with gas - this is the third rule of autonomy.

    LED lighting. You can take LED assemblies, individual LEDs or LED strips. In the latter case, you can buy wholesale in a Chinese online store immediately for the whole house and decently save. The main task is to choose the voltage of the LEDs equal to the voltage of the energy stores in the house. After all, any conversion will eat extra watts. Hence the fourth rule: LED lighting wherever possible.

    Motion sensors are a great help in saving electricity - this has also been identified empirically. On the way to the toilet, on the stairs to the second floor or in the hallway, it is best to put a motion sensor and LED strip. This will avoid going to the switch in the dark and save you from unnecessary energy losses when someone forgot to click a button.

    Such a sensor will cost about 300-350 rubles, but it will save a lot of nerves and energy. Own consumption is scanty in comparison with the included and forgotten lighting. One funny case from practice: pets quickly calculated the range of the sensor and at night had fun entering and leaving the visibility zone, including the light.

    And now about the technique that will be needed to create an autonomy on solar energy:

    1. Solar batteries:


    2. The controller of a charge of accumulators from solar batteries:


    3. Batteries. When discussing the type of batteries, so many copies were broken that I don’t even want to remember. One of the most difficult tasks and the most expensive part of the system:


    4. Inverter from direct current to alternating voltage of 220V:

    These are the four main elements of an autonomous energy system based on solar panels. I’ll talk about expanding the functionality in the second, practical part, but for now I’ll write out the minimum autonomy for the country house, where I want to watch TV in the evening, go out from the laptop to the network and sit at the table in the light of the lamp. Everything is considered based on the middle zone of Russia from April to September. At other times of the year, the sun is noticeably less, and the summer season is practically closed or not yet open.

    We take the initial consumption:
    1. An average laptop with a consumption of 80 Wh * will work 5 hours a day
    2. An average television with a consumption of 40 Wh * h (LCD) will work 3 hours a day
    3. Lighting with 3 LED strips (24 W / pc ), which is enough for a room of about 40 sq.m. will work 4 hours

    Total we need energy: 808 Wh
    If an ordinary car battery with a voltage of 12 V is selected as the energy store, then 67 Ah will be spent over the evening. In order not to drop the battery and extend its service life, it is recommended to discharge the battery by no more than 30%, which means that the required capacity is 200 Ah or more. In addition, during daylight hours it will be necessary to replenish the spent ampere hours, and you also need to take into account the efficiency and inconstancy of the sun in order to select the required number of solar panels. Suppose that the sun shines for 8 hours, from them it will be cloudy for 3 hours and the efficiency of energy production will drop. Therefore, we must compensate for 67 Ah in 5 hours. It would seem that there is nothing easier: 14 And we pour in 5 hours and that's it, but the solar energy has a lot of nuances.

    Turning to the calculation of the necessary equipment that will need to be purchased for the electrification of a country house, we get:
    1. Solar battery 2 pcs x 100 W - 15000 r
    2. The most simple charge controller - 800 r
    3. Battery 190 Ah - 8500 r
    4. 3 LED strips - 1200 p.
    5. Inverter 12V-220V - 2000r.
    Total: 27,500 rubles. The

    equipment was considered the most inexpensive, taking into account the minimum comfort described above. If you liked the material and want to see the implementation of a more powerful and current system, please let me know so that I can start writing the second part.

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