# No need to be afraid of solar panels

I searched in Google for “100 W solar panel” and in the top ten a link to Habrahabr, an article from 2011, is issued. The comments are the right thing, but the relevance today is nonsense. Today, a 100 W solar panel (in Ukraine) costs up to \$ 100, controllers, batteries - all this is not very stressful. But the biggest catch of green progress is that people simply don’t understand what solar energy is, how to correctly and intelligently implement everything, why it is necessary and in general ...

Not for promotional purposes. I trade solar panels on the market and 90 people out of 100 repel this innovation, as cell phones repelled 15 years ago - expensive, not necessary, not profitable, and so good. Many people want to dial panels at \$ 100 per 10 kilowatts and not pay for electricity. Count yourself - 100 W x10 = 1 kW * 10 = 10 kW = 10 000 dollars. It is only on the panel, without batteries and controllers. Batteries for an hour of operation of a load of 10 kW need another 12-13 pieces of 100 Ah / (another 200 dollars each), etc. As a result, they look at the seller as an idiot, throw everything out of their heads that you tell them and one thing remains in that very head: "I am not interested." In fact, things are a little different.

Why are solar panels created? What is the meaning of human life? Why do we breathe dirty air? Save the planet, free Willy!

There can be many answers to these questions, I will try to state more or less clearly how I see it.
A solar panel is a device that converts solar radiation into electric current. More solar panels have no functions. They were not created for saving, for beauty, for boasting. Since the sun does not always shine the same, but does not shine at night at all, it is logical to use energy storage devices - batteries. Plus clouds, seasons, temperature, etc. - These are all factors that prevent the panels from giving stable energy all the time. So, I propose to consider the option of autonomous lighting for a private house, and there, substitute your data in the formulas and calculate the system for yourself.

Take the worst season of the year - winter. In winter, in Ukraine, a sunny day lasts from the power of 8 hours, plus there are clouds ... NO! STOP!In my experience, you don’t need to start calculating from the amount of money or from a price tag of \$ 100 on a 100 W panel. Initially, you need to select the load. To illuminate the cottages in two rooms and a plot in front of the house, we need 5 meters of LED strip. We will place three meters in the house, and let two be used to illuminate the arbor and the plot in front of the house. According to experience - this is more than enough for a standard summer cottage plot of 5 acres with a small house. The tape can be wound on a glass bottle, making such a light bulb for yourself, on the street in the gazebo just stick it under the roof, and we will illuminate the area in the casing from under a standard searchlight, throwing out the cartridge under the halogen. In general, everyone does as he wants, it is his right. We are here about formulas and calculations.

So. 5 meters of super-bright LED strip 5050 will consume a maximum of 5 A per hour at 12 V. We want to have lighting in the house for an hour. After all, no one is sitting in the house longer, right? (this is 2 A - 2 meters of tape, 1A each meter, recorded). In the gazebo for 4 hours (1 meter of tape 1A, plus 4A plus) and on the territory of 8 hours (2 meters of tape 2A, another 16A). Total consumption of 22 Amperes per night (~ 270 W at 12V) is recorded.

To ensure autonomous lighting in the country, we need a battery 2 + 4 + 16 = 22 A / h. There are 25-26 Ah batteries on sale, its cost in Ukraine is about 450-550 UAH (55-65 dollars, meaning a multi-gel battery). To fully charge this battery, we need to charge it with a current of 2.5 A for 10 hours. In the summer, when the sun and everything is fine, this will give us a solar panel of 50 watts. But suddenly, rain, winter, just overcast, the bird pumped onto one cell and it turned into a parasite cell - I suggest taking a panel of 100 W, it gives a current of up to 6A, in any case 2.2-2.5A we will have (panel price of 100 W per Ukraine 800 UAH, 100 dollars).

I already wrote that panels do not give stable current and voltage all the time. For this we use a charge controller for solar panels. The controller not only protects the battery from overcharge and overdischarge, but also regulates the charge voltage depending on the ambient temperature (controller price for 10A in Ukraine is \$ 18-20, recorded).

In general, we came to the finish line. From calculations, it turned out that for lighting a country house, a plot and a gazebo, we need:
5 meters of an ultra-bright LED strip -20 dollars
Solar panel 100 W - 100 dollars
Charge controller 10A - 20 dollars
Battery 26 A / h - 65 dollars
Cable - to how much is needed, let ShVVP bay 2x2.5 100m, 60 dollars

Total: \$ 265 and we have everything, everything is free (you must admit, this is not hundreds of thousands of dollars with a stupid approach on the wrong side). The biggest disappointment comes at the moment of final counting - this system will never pay for itself. After 5 years, you will have to change the battery, after 20 years the panel, after a week you will want to connect another TV / radio / laptop / tablet and you will have to add batteries and panels.

But ask: “Why do I need all this?”

1. Solar panels are used where there is no electricity at all or it is very expensive (For example, in Ukraine, enterprises pay 5 times more than ordinary consumers and they have a limit over which the tariff grows 20 times)
2. This is autonomy and independence. You do not depend on natural disasters, on the vagaries of the energy supplying company
3. It is fashionable, it is beautiful and stylish. You can reassure yourself that by charging your mobile phone, you did not burn a ton of oil :)

PS To reduce the cost of the system. You can use any stolen old unnecessary battery. It is not necessary to take 5 meters of ultra-bright tape, you can also use the usual 120 diodes or 60 diodes and you do not always need 5 meters. Do not turn on the lights all night, save!
PSS The panel does not need to be placed on the roof, it can be done in the garden or on the wall - almost vertically. It will be even better, because in winter the sun “goes” low and it’s better to make the system in winter, in summer it will crush.
PSSS Do not strive to assemble the system on huge panels of 200-300 watts. There is no difference between the price of a Watt of 100 and 200, but the sail on your wall will be quite large and heavy, no matter what comes off. IMHO better two or three "hundred" than one large panel.