How to choose solar panels for private houses

The formula for calculating the electrical power of a solar battery

There is quite a lot of information on the Internet about solar panels, so I'd rather focus on specific numbers that allow you to calculate the average amount of energy generated by solar panels. Of course, an important factor to consider when installing such panels is the amount of solar radiation falling on them. For example, you have purchased solar panels, which indicate a power of 250 watts. This means that it will give you 250 W of solar energy at a radiation of 1000 W/m². Naturally, such ideal performance can only be achieved with clear skies and bright sunlight. To calculate the electrical power, you need to use the following formula:

battery area * conversion efficiency * solar radiation.

For instance,

1.6 m² * 15% * 1000 W/m² = 240 W.

Each sandpiper praises his swamp

Although 52% of respondents point to a crisis of reproducibility in science, less than 31% consider the published data to be fundamentally wrong and the majority indicated that they still trust the published work.

Question: Is there a reproducibility crisis?

Of course, it is not worth blaming and lynching the whole of science as such only on the basis of this survey: half of the respondents were still scientists connected in one way or another with biological disciplines. As the authors note, in physics and chemistry, the level of reproducibility and confidence in the results obtained is much higher (see the graph below), but still not 100%. But in medicine, things are very bad compared to the rest.

An anecdote comes to mind:

Marcus Munafo, a biological psychologist at the University of Bristol, England, has a longstanding interest in reproducibility of scientific data. Recalling the days of his student youth, he says:

Question: How many already published works in your industry are reproducible?

Initial data for calculations

Now consider how to calculate solar panels? The main figure required for calculations is the total energy consumption for a certain period. If the panels are installed in an electrified country house, then the electricity consumption can be determined by the meter. However, if the power supply is connected for the first time, it is necessary to make a list of all available consumers with an indication of the capacity of each of them.

For example, a refrigerator consumes 350 Wh. It will consume about 1 kWh per day, and about 30 kWh per month. In the same way, you need to calculate the energy consumption of lighting and other appliances.

The resulting figures are added up and the total daily energy consumption is determined first. The result is then multiplied by the number of days in the month to give the preliminary value. For example, the power consumption is 100 kWh. This figure will be relative, since another 40% should be added to it for losses in the battery and during the operation of the inverter.

Thus, the total electricity consumption per month will be 140 kWh. It turns out 140:30:7 = 0.67 kW / h per day. Therefore, panels with a minimum power of 0.7 kW are required. However, they will be sufficient only in good weather in the summer and partly in spring and autumn. It is also necessary to take into account cloudy days, which are often observed in the summer months. In this regard, it is required to increase the number of panels at least twice, otherwise the electricity will be intermittent.

The maximum effect from the solar system is obtained only under the condition of the coordinated work of all constituent parts and components. First of all, you need to correctly calculate the batteries based on the initial data, because the efficiency of the entire power plant will depend on these calculations.

What to do

Of the 1,500 interviewed, more than 1,000 spoke in favor of better statistics in data collection and processing, better oversight by bosses, and more rigorous design of experiments.

Question: What factors will help improve reproducibility?

Answers (from top to bottom): –Better understanding of statistics –More stringent oversight –Improved design of experiments –Education –Intralab validation –Improve practical skills –Incentive for formal data review –Interlaboratory validation –Dedicate more time to project management –Raise the standards of scientific journals – Allocate more time to work with laboratory records

Conclusion and some personal experience

Secondly, the article ignores (or rather does not consider) the role of scientific metrics and peer-reviewed scientific journals in the emergence and development of the problem of irreproducibility of research results. In pursuit of the speed and frequency of publications (read, increasing citation indexes), the quality drops sharply and there is no time left to additionally check the results.

As they say, all the characters are fictional, but based on real events. Somehow one student had a chance to review an article, because not every professor has the time and energy to read articles thoughtfully, so the opinion of 2-3-4 students and doctors is collected, from which a review is formed. A review was written, it pointed out the irreproducibility of the results according to the method described in the article. This was clearly demonstrated to the professor. But in order not to spoil relations with "colleagues" - after all, they succeed in everything - the review was "adjusted". And such articles were published 2 or 3 pieces.

It turns out a vicious circle. The scientist sends the article to the editor of the journal, where he indicates “desirable” and, most importantly, “unwanted” reviewers, that is, in fact, leaving only those who are positively disposed towards the team of authors. They review the work, but they can’t “shit in the comments” in a black way and try to choose the lesser of two evils - here is a list of questions that need to be answered, and then we will publish the article.

PS: The article was translated and written in a hurry, about all the errors and inaccuracies noticed, please write to the LAN.

Calculation of the number of solar panels

It is done very simply: the total need for electricity is divided by the power of the panel. The total need can be determined in two ways:

1. Compose list of all electrical devices
   , determine the approximate duration of work during the month, calculate how much electricity each of them consumes per month (power multiplied by the number of hours), and summarize all the figures obtained.
2. Raise electricity bills
   and find the largest amount of kWh consumed in one month. Just in case, the resulting figure can be multiplied by 1.5.

Suppose that in a month 3-4 the inhabitants of the house use 300 kWh. To fully provide yourself with your electrical energy, you need to have 300 * 12 / 284.16 = 12.66 SolarWorld 2015 panels. The final figure is rounded up, of course. Therefore, you need to buy 13 panels.

In 1991, in Germany, in the capital of Bavaria, Munich, the INTERSOLAR EUROPE exhibition was opened. At this exhibition, leading manufacturers of solar energy systems presented their latest developments.

As conceived by the organizers of this exhibition, Freiburg Wirtschaft Touristik und Messe GmbH & Co. KG - this international exhibition was entirely dedicated to the use of solar photovoltaic cells in various fields, as well as solar heating components

The exhibition immediately attracted the attention of experts from many countries around the world. It was a great success, so the organizers decided to make it traditional and hold it annually.

The exhibition, which takes place in May-June, brings together the heads of the largest manufacturing companies, as well as companies using various types of solar energy products, developers, engineers, and scientists working in this field.

Everyone wants to get acquainted with new ideas, the latest technologies in the field of solar energy application. Experts exchange experience, present their latest developments. In the exhibition halls you can see miniature chargers and the most powerful solar panels, a transparent solar-powered TV and a solar house, various appliances, devices, machines that operate solely on solar energy.

This exhibition is not intended for the general public, but exclusively for professionals. Seminars and conferences for specialists working in the fields of photovoltaics, energy storage systems, renewable heating technologies are held at its sites. Separate pavilions are allocated for the presentation of the most interesting developments.

At the last two exhibitions, Chinese and South Korean manufacturers of solar modules presented their latest products - panels with a power of more than 300 watts.

The second formula for calculating the power of a solar panel

There is another formula that allows you to calculate the amount of energy generated by solar panels. To do this, you need to know the size of your battery, as well as the amount of power it produces and the average amount of time it has been exposed to solar radiation. Let's say that you have a 2 m² solar panel with a power of 185 watts. In winter, it receives sunlight for a maximum of 1-1.5 hours, in summer - 3-3.5 hours. Now we can calculate the average electricity generated by such a battery.

Winter: 185 * 1.5 = 278 Wh. Summer: 185 * 3.5 = 648 Wh.

Pros and cons of solar panels

Yes, the use of solar panels may seem like a fairly rational solution when you need to provide yourself with electricity and heat:

1. There are many companies on the market now that are ready to provide you with quality batteries.
2. Despite the price, photovoltaic panels can pay for themselves within 2-3 years.
3. Power guarantee: 12 (over 90%) and 25 years (over 80%).
4. Minimum maintenance.

But do not forget about the cons, which also have a place to be:

1. Low efficiency on cloudy days.
2. The need for fairly large areas to accommodate the panels so that they can generate enough energy.
3. To store energy, special batteries are needed.

Conclusion

I myself have always wanted to switch to alternative energy sources and, with the advent of solar panels in Ukraine, I realized that it was time to put my plans into practice. The only problem that I now observe is a small amount of solar radiation in the winter. But that doesn't stop me! I think she can be dealt with in the end. I really believe that solar panels can provide the necessary amount of electricity to support a normal way of life, which means that in the near future they can be a great way to generate energy for the average person.

13.02.2017

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Calculation example

Initial data (optional):

• A TV with a power of Pa = 100 W works t = 5 hours a day and 7 days a week.
• Lighting devices with a total power of Pa = 1000 W, t = 6 hours a day and 7 days a week.
• Illumination of the solar panel: T - 5.5 hours per day (latitude of Moscow, summer).
• Inverter efficiency - 0.9.
• Characteristics of one battery: Ca - 225 A / h, Ua - 12 V.
• The battery discharge level is 0.7.

With a total power of devices of 1100 W, the average daily energy consumption will be Wn = 45.500 kWh per week or Wc = 6.500 kWh per day. For an accurate calculation, it is necessary to take into account the likelihood of simultaneous use of devices, peak and reactive loads, or load distribution during the day.

Based on the total consumer power of 1.1 kW, we select an inverter with a power of 2 kW (with the prospect of growth and compensation for unaccounted loads). Inverter input voltage Uinv - 24 V.

Full daily current load on the inverter in A * h, taking into account the efficiency of the inverter: Wc / efficiency * Uinv \u003d 6500 / 0.9 * 24 \u003d 297.91 A * h.

This value is important for determining the number of batteries, the charging current and, ultimately, the reliability of the system.

In our case:

• The current load is doubled to provide a two-day power supply.
• We take into account the permissible depth of discharge of the battery 0.7.
• We get the total current load - 297.91 * 2 * 0.7 \u003d 851.19 A * h.

Taking into account the characteristics of one battery Ca = 225 Ah, we obtain the number of battery blocks for a voltage of 24 V (inverter voltage) 851.19/225 = 3.78. Round up to 4. In order to get Ua (12 V) for one battery, we connect two batteries in series in one block. In total, 4 blocks connected in parallel, consisting of two batteries each, are obtained. There are 8 batteries in total.

In addition to the load of the consumer, it is necessary to add a load that takes into account the recharging of the batteries. It is 10% of the total power of the battery module (8*225*12) = 21600 Wh*10% = 216 Wh. The total average daily consumption will be - 6500 + 216 = 6716 Wh.

To provide the system with energy, the solar battery must generate the average daily electricity demand (6716 Wh) during the illumination time (T = 5.5 hours). Therefore, a block of solar modules (with an output voltage of 24 V and a power of 200 W each) should consist of 6 modules (6716 / 5.5 * 200 = 6.10).

Latitude and longitude depth of the problem

Imagine that you are a scientist. You come across an interesting paper, but the results/experiments cannot be replicated in a lab. It is logical to write about this to the authors of the original article, ask for advice and ask clarifying questions. According to the survey, less than 20% have ever done so in their scientific career!

The authors of the study note that perhaps such contacts and conversations are too difficult for the scientists themselves, because they reveal their incompetence and inconsistency in certain issues or reveal too many details of the current project.

Moreover, an absolute minority of scientists attempted to publish rebuttals of irreproducible results, while facing opposition from editors and reviewers who demanded that the comparison with the original study be downplayed. Is it any wonder that the chance to report non-reproducible scientific results is about 50%.

First question: Have you tried to reproduce the results of the experiment?

Second question: Have you tried to publish your attempt to reproduce the results?

Maybe it's worth then inside the laboratory at least to carry out a test for reproducibility? The saddest thing is that a third of the respondents have NEVER even thought about creating methods for checking data for reproducibility. Only 40% indicated that they regularly use such techniques.

Question: Have you ever developed special techniques/technological processes to improve the reproducibility of results?

In another example, a biochemist from the United Kingdom, who did not wish to be identified, says that trying to replicate work for her lab project simply doubles the time and money, without adding or adding anything new to the work. Additional checks are carried out only for innovative projects and unusual results.

And of course, the age-old Russian questions that began to torture foreign colleagues: who is to blame and what to do?

Determination of electricity losses in the home system

The value of these losses is taken into account by Kpot. These losses can be:

1. Wires. The value is 1%.
2. . They range from 3 to 7%.
3. Shunt diodes (0.5%).
4. The battery itself at very low solar radiation (1-3%).

Also power losses can occur due to the strong heating of the module
(make 4-8%) and due to the presence of dirt on the solar panels or their darkening (1-3%).

An autonomous electrical system for a home is considered optimal if the total losses do not exceed 15%. Then the payback period is reduced, and the batteries accumulate more current. Kpot
is 0.85. However, poor quality equipment or an illiterate choice of components can lead to 30 percent losses. Kpot
will already be 0.7.

Solar battery LG 315 N1C-G4 NeON2

Already from the very name of this solar module of the South Korean company LG it follows that the declared power of this module is 315 watts.

It is very important for LG to enter the market of alternative energy sources not just as one of the manufacturers, but as one of the leading manufacturers of photovoltaic systems.

Therefore, product quality assurance is one of the company's top priorities. Solar panels are designed and manufactured using the most advanced technological processes.

And the photoconverters that make up this solar battery are made with the highest quality and efficiency.

The cells are made on the basis of single-crystal silicon using a special bilateral technology. Due to their qualities, these cells are able to transmit sunlight, which, reflected from a special coating on the back of the cell, contribute to an increase in the generation of electric current. That is, each cell can generate electric current on both sides, thereby increasing the power of the module.

LG 315 N1C-G4 NeON2 module. Front side

Before assembling the module, each plate undergoes the most thorough control for strict compliance with the dimensions (accuracy to the micrometer) and detection of possible mechanical damage. After checking, the selected cells go through the next stage of preparation. To minimize the reflection of sunlight, the cells undergo an alkaline wet etching step. Cells on the front side are laminated with a three-layer coating of EVA (ethylene vinyl acetate) and a special reflective film on the back.

LG 315 N1C-G4 NeON2 module. Backside

The assembled module is then encapsulated to protect the cells from moisture penetration, and then covered with 3mm anti-reflective shockproof glass. The frame of the module is made of anodized aluminum profile. On the rear side, a multifunctional junction box with bypass diodes is installed.

Multifunctional junction box

Thanks to this manufacturing technology, LG NeON 2 modules have a characteristic black color, which makes them attractive from an aesthetic point of view.

Rated power 315 watts.
Efficiency 19.2%
N-type
Dimensions (LxWxT) 1640x1000x40 mm
Weight 17.0 ± 0.5 kg
Type of connectors MS-4
Protection class IP67
The cost of the module is 30,000 rubles

Calculation of solar panels

The required power of solar panels is calculated in accordance with the weather in the area and the intensity of radiation at different times of the year. Of great importance in the calculations are the angles of inclination horizontally and vertically. This indicator is especially important if the solar system will be operated all year round. The location of the equipment will also depend on this. If the angle of inclination does not require adjustment, then the panels can be placed directly on the roof of the building.

The most responsible event is the calculation of solar panels, the number of modules and their efficiency. The data is taken from the best and worst month in terms of energy efficiency. For calculations of standard insolation, an area of ​​​​1 m2 is selected, and to determine the rated power, a temperature of 25 ° C is required, with a standard luminous flux of 1 kW / m2.

Determining the performance of the solar battery during the month is carried out according to the following formula: Esb = Eins x Psb x η / Rins. Its variables correspond to the following indicators:

• Esb is the amount of energy generated by the battery.
• Eins is the result of monthly insolation of 1 m2.
• η - the value of the overall efficiency in the transfer of current through the conductors.
• Rsb - nominal power of the solar panel.
• Rins - the highest insolation power of 1 m2 of the Earth's surface.

When calculating, it is necessary to use units that are the same for all indicators. As a rule, this is joules or kilowatt-hours. By calculating the monthly insolation, you can easily determine the nominal power of the solar panel required to generate the monthly amount of electricity: Psb = Rins x Esb / (Eins x η).

It should be noted that the voltage at the output of the solar panel will be 15-40% higher than the battery voltage. When using cheap controllers, this difference invariably goes to waste. More expensive modern models can reduce this figure to 2-5%.

Solar radiation has different power indicators, depending on the season and the specific month. The rated power of the panel itself remains unchanged, so the correct choice of its installation location is of great importance. Using the formulas above, only an approximate number of modules can be determined. To get an accurate value with the necessary margin, double the number of panels is taken, adjusted for night time, cloudy days, snowfalls and other factors that reduce the efficiency of the system.

The power of solar panels for a private house and their performance largely depends on the correct choice of battery and inverter.

Varieties of solar panels. What to look for when calculating the operating parameters of a solar power plant user experience.

Solar panels are rarely considered as the only source of electricity, however, there is an expediency in their installation. So, in cloudless weather, a properly calculated autonomous system will be able to provide electricity to electrical appliances connected to it almost around the clock. However, well-packed solar panels, batteries and auxiliary devices, even on a cloudy winter day, will significantly reduce the cost of paying for electricity by the meter.

The correct organization of autonomous power supply systems based on solar panels is a whole science, but based on the experience of users of our portal, we can consider the general principles for their creation.

Features of the indicators used in the formula

The amount of solar energy falling on the roof and walls of a house in a certain region can be measured for different periods of time. Meteorologists (they are the ones who measure this indicator) calculate the annual, monthly and daily solar radiation per 1 sq. km. m.
If this indicator is annual, then its unit of measurement is kWh / (m² * year). Instead of the word "year" there can be the words "month" and "day". For example, an indicator of 5 kWh / (m² * day) means that in 1 day 5 kW of solar energy falls on 1 square meter.

Any indicator can be substituted into the above formula. It should be remembered that if annual solar energy is substituted, then the result of the calculation will be the amount of electricity that the panel produces in 1 year. Similarly with indicators of other periods of time. It is most expedient to calculate the monthly production of electrical energy. This is because the intensity of lighting is different every month, and to generate, for example, 10 kW of electricity, you must use, and also connect the appropriate number of batteries.

Although the expression includes 2 measures, it should be treated as one. This is because it shows panel performance
. It would be more correct to use the expression ,
where S is the area of ​​the photosensitive plates in square meters. m. It allows you to determine the efficiency of solar panels, or rather, what part of the world can turn 1 square. meter panel into electrical energy.

For example, there is a German SolarWorld 2015 monocrystalline panel. It has an area of ​​1,995 square meters. meter and power 320 watts. Its efficiency is 320 / (1,000 * 1.995) * 100 = 16.04%. Of course, to use in the formula, the expression does not need to be multiplied by 100. It should use the number 0.1604.

However, the second expression is not used because the result is power 1 sq. panel meters
. As you know, the battery rarely has such an area. This figure is much higher. For example, the above product has an area of ​​1.995 m². As a result, the final result calculated by the formula would need to be multiplied by the area. It would turn out that there would be S in the numerator and denominator of the expression. And if S is divided by S, 1 will come out.

Ko is taken from a special table, in which a certain coefficient corresponds to a different value of the angle of inclination and the angle of deviation from the south direction. Manufacturers can provide such a table. They can also always give useful advice, some of which may relate to the choice of batteries.