Full energy autonomy or how to survive with solar panels in the outback (part 2. practical)



    The real solar autonomy for the end user consists of the money spent, samples, installation of devices and training households to use electricity economically. Moreover, the last point is worth paying special attention to, since autonomy involves a very special approach to energy consumption and even the restructuring of familiar actions.





    Since solar panels are the most visible part of the system, and even convert the energy of the sun into electricity, it is worth starting with them. There are two ways to get a solar battery: do it yourself or buy a ready-made one. I must say right away that the final cost of the final product in the manufacture of several panels and without experience will cost about the same amount as a finished panel of the same capacity, but produced at the factory. But it’s interesting to do it yourself.
    Here we need to add a little theory again. There are three available for customers, for sane money, solar cell technology, consisting of different cells: monocrystalline, polycrystalline and amorphous silicon. They differ in structure and this is even visible by eye. I will try to tell you as simple as possible, but those who want to plunge into the difference in chemical compositions can see the information themselves - do not overload the article.
    Amorphous silicon is the most promising manufacturing technology. It allows you to produce bendable panels and generate current in diffused light, that is, in cloudy weather, but they degrade quite quickly, which translates into reduced efficiency.
    Single crystal - pure cells made of primary silicon. As a rule, black plates without inclusions, almost square in shape with rounded edges. Sometimes they are cut in half to increase the voltage of the line of elements.
    Polycrystal - cells made of secondary silicon or not very clean. Probably, single crystal scrap is used.

    Battery types are arranged in descending order of cost. And if the second and third options are still close, the first noticeably breaks out in cost, and even reduces energy production over time. To manufacture our own Solar Panel (hereinafter referred to as SP or SB - Solar Battery), a consignment of Grade B class solar cells was ordered in China (you can read about the classification of elements HERE) amount per pair of sat. It is necessary to check that the kit includes junction boxes, buses for connecting the cells to each other and at least a couple of meters of cable. MC4 connectors for connecting batteries were also ordered there. In Russia, the production of enlightened tempered glass with a thickness of 4 mm was ordered. This thickness is due to the need to protect themselves from all kinds of icicles (hail) and other weather conditions (a targeted stone blow is unlikely to survive), and enlightened glass is needed to increase the efficiency of the elements. For framing glass, protection against chips and ease of installation, an aluminum corner 30x30 and the necessary fasteners for it were purchased. To connect solar panels to the system, a multicore copper cable with a cross section of 6 mm square was selected. For charging, a PWM controller was ordered in the same China, and to power 220V devices - a simple car inverter with a capacity of 100 Chinese watts. Later I will explain the difference between conventional and Chinese watts.

    Energy system number 1. Budget

    Independent production of a solar panel

    So, assembly. The modules came in a box and some of them were broken, as in the first photo. For this, in stock, as a rule, there are about 10 pieces. I complained to the Chinese in a letter and he sent me another 10 cells for free. Each cell gave 0.5 V and 4 A according to the statement of Chinese sellers. That is, each module is 2 watts. To charge the battery, you must have a voltage above 14.4 Volts, that is, you need to combine the cells in series. Looking at the factory panels and using the practice of many home-made craftsmen, it was decided to combine on the same glass two chains of 36 elements each, receiving 18 Volts and 8A at the peak. That is, one panel could bring up to 144 watts of energy, which never happened. We will consider the reasons later, but for now manufacturing.
    The procedure is simple. Solder the tires:


    Prepare the glass with the frame:



    We lay, solder, remove the tires and solder the wires, and then fill it with a special compound to seal all the plates. The people poured sealant, various mastics, I liked the finished compound produced by the company in St. Petersburg. It's nice that the production is Russian, so giving money was not a pity, and the result was pleasantly pleased. It would be nice to fit a sealed box with a diode to the terminal pins, which will prevent a drop in system power during serial connection, if one of the batteries turns out to be darkened. The box came complete with cells.



    As a result, I got two solar panels with an estimated power of 288 watts.



    But there is a lot of conventions. When the solar panel is heated, its efficiency drops even from the calculated percentage by 20. In addition, the elements are not soldered and microcracks that inevitably occur during soldering. As a result of measurements in the summer sun, I got 40 watts from each panel, that is, the result is three times smaller than expected. The price of such a panel came out around 6000-6500 rubles, while factory panels with delivery cost 7000-7500 rubles. So I finished my initiative and in the future I bought only factory panels.

    Base voltage selection
    Perhaps this is one of the first decisions that must be made when designing solar panels. The fact is that solar-powered systems are created with a voltage that is a multiple of 12 - because most batteries have just such a voltage. Even capacious batteries assembled from 2V cells are often collected at 12, 24, 36 or 48 volts. Here we must recall the physics and the formula of electric power: P = U * I. It follows from it that at equal power, increasing the voltage, we will reduce the current. It is quite natural that a decrease in current will entail a decrease in the load on the element base and a decrease in the cross section of wires, but it is impossible to increase the voltage infinitely. Here the following problem exists: direct current, in contrast to alternating current, when the voltage rises above 36 volts, is much more dangerous for humans. If you don’t delve into theory, then you can most often tear your hand away from alternating current with a voltage of 220V, but you can almost never tear off a constant one. In addition to this, you can vote for low voltages, if only because 12V is a typical voltage of a car battery, which means there are a lot of different equipment designed for this voltage. In addition, increasing the battery capacity is possible by simply adding conventional batteries to the parallel, while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. but it’s almost never possible from constant. In addition to this, you can vote for low voltages, if only because 12V is a typical voltage of a car battery, which means there are a lot of different equipment designed for this voltage. In addition, increasing the battery capacity is possible by simply adding conventional batteries to the parallel, while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. but it’s almost never possible from constant. In addition to this, you can vote for low voltages, if only because 12V is a typical voltage of a car battery, which means there are a lot of different equipment designed for this voltage. In addition, increasing the battery capacity is possible by simply adding conventional batteries to the parallel, while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. that 12V is a typical voltage of a car battery, which means there are a lot of different equipment designed for this voltage. In addition, increasing the battery capacity is possible by simply adding conventional batteries to the parallel, while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. that 12V is a typical voltage of a car battery, which means there are a lot of different equipment designed for this voltage. In addition, increasing the battery capacity is possible by simply adding conventional batteries to the parallel, while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time. while with high voltage, you would have to buy batteries in pairs, triples or fours. There is another unpleasant moment in the series connection of the batteries: the unbalance of the cells, which leads to the failure of one cell first, then the whole battery and the entire chain, if the problem is not tracked in time.

    My choice: 12V

    Choice of solar charge controller
    There are two main types of controllers: PWM or PWM controller and MPPT or Maximum Power Point Tracking - Tracking the Maximum Power Point.
    The first type is as simple as possible and you don’t need to explain it to those familiar with PWM, but for the others it is as simple as possible: upon reaching the maximum battery level, the ripple controller gives current to the battery, not allowing it to recharge. Plus this scheme: simplicity, which means low cost. Less: you can connect batteries whose voltage rating matches the battery voltage rating.
    MPPT controllers are more complicated, more expensive, but have a huge advantage: solar panels can be connected in series, thereby increasing the voltage in the circuit to the controller and reducing current, which allows the use of thinner wires and reduce the loss of energy transfer to the controller. And the efficiency of such controllers is higher, because they scan currents at various voltages with a certain frequency and select the point of maximum power. Hence the name. If you want to plunge into the world of technology, you can go here , where it is reasonably detailed and detailed.

    To my own panels, I bought a Chinese PWM controller that gives a charge of up to 30A, that is, 360 W at a voltage of 12V or 720 W at a voltage of 24V. But since the system is selected at 12V, the limit is 30A or 3 solar panels connected in parallel.


    A voltmeter and an ammeter ordered from there were added to it to see what condition the battery is in and what charge is going into the batteries. The battery was chosen the cheapest lead-acid, with a capacity of 190 Ah, because I still believed that I was about to be connected to mains electricity.

    Choose an inverter
    We pass to the most entertaining point of our system. To begin with, in addition to power, inverters are easily divided into two types: with a pure sine wave at the output and a modified sine wave (also referred to as an approximated sinusoid or meander). The former produce a pure sinusoidal signal, while the latter have a step on the graph:

    image

    For most equipment there is no difference, and if you connect a simple voltmeter, its readings will be approximately the same. But if you compare the prices for both types of devices of the same power, it turns out that the price differs by an order of magnitude. Do I have to pay for a pure sine and why is it needed?As practice has shown, most devices easily get along with a modified sine wave, although some engines, for example, refrigeration compressors, start to heat up more and the risk of premature failure increases. In addition, if you connect audio equipment to the modified sine wave, noticeable noise will be heard, which is not at all happy when you want to enjoy good sound. From my own experience I can say that only the washing machine refused to work from the modified sine wave - all the other devices worked successfully. If there is a sum for a good inverter, then it is worth choosing a pure sine, if other devices are sensitive to signal purity.

    We select the inverter power
    In this matter, there are a lot of nuances that affect the choice of an inverter. The rule applies: the entire planned power load is added up and multiplied by two. For example: 4 lamps of 60 watts + a washing machine of 800 watts + a laptop of 80 watts + a refrigerator of 100 watts + a TV of 50 watts. It would seem that the maximum consumption is 240 + 800 + 80 + 100 + 50 = 1270 W and it is enough to take an inverter for 1300-1500 W, but! Different loads behave differently. For example, the starting current of the refrigerator can reach ten times the value during the start, which means it will require 1 kW of power instantly, and if the light and the washing machine are turned on at that time, the inverter will simply fail if it does not burn out. In addition, this type of Chinese invertersat 1500 watts were unable to start the refrigerator with a rated power of 100 watts of energy consumed. An experiment was conducted when the refrigerator started from the generator, and then quickly switched to the inverter using the phase switch. So it was possible to power the refrigerator from a Chinese inverter for 600 watts - barbarism is difficult, but it worked. The trouble is one: such an inverter is not able to start the refrigerator a second time. The deception was to set the refrigerator settings to maximum frost. And the refrigerator freezes until it is turned off. So you can freeze food during daylight hours, and turn it off at night.
    So, the power of the inverter must be such as to provide a double supply of consumption of your conventional devices or ten times to start the motors.

    My choice: two Chinese inverters with a capacity of 1000 and 600 watts.

    Duplication
    When choosing cheap and simple components, it is better to immediately lay on the duplication of systems. This will allow you to not be left without electricity in the event of failure of any element. Such reinsurance will not be expensive, but will provide peace of mind and stable nutrition.

    In general, the first set of autonomy looked like this:
    1. Two homemade solar panels with a total power of 80 W
    2. PWM- battery charge controller with a maximum current of 30A
    3. Automobile lead-acid battery with a capacity of 190 Ah
    4. Inverter for 600 W and 100 W with a modified sine wave

    The scheme of a working budget autonomy looks like this:



    Please note that the inverter connects directly to the battery, even if it consumes all the power of solar panels. In addition, it is necessary to avoid power failure of the controller when solar panels are connected, because this threatens with the failure of the controller.
    The first year my solar autonomy existed in this form and allowed me to charge gadgets, stay in the evenings with light and work on power tools on bright sunny days, like a drill or a jigsaw.

    The material turned out to be more than expected, so the second version of the solar autonomy, which cost a little more, but allowed you to use a powerful electric tool, use a pump station, and in general to refuse a gas generator for the summer, I will describe in the next article. What is the difference between good china and european china? Should I buy expensive equipment through Ebay? And also I will give an answer to the main question: was it worth it? Please ask specific questions, which I will answer in the next part.


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