Aspects that affect how much energy a solar panel produces
First of all the performance of solar panels depends on the material and technology of manufacture. Of those on the market, you can find batteries with a capacity of 5 to 22%. All solar panels are divided into silicon and film.
The performance of modules based on silicon:
There are also mixed types of panels, which, by using the advantages of one type to offset the disadvantages of another, thereby increasing the module’s efficiency.
Also on how much energy a solar panel gives affects the number of clear days per year. It is known that if the sun in your area appears for a whole day less than 200 days a year, the installation and use of solar panels is hardly profitable.
In addition, the efficiency of panels is also affected by the temperature of the battery heating. So when heated by 1̊ C, the efficiency drops by 0.5%, respectively, when heated by 10̊ C we have half the efficiency. To prevent such trouble, cooling systems are installed, which also require the consumption of energy.
To maintain high performance during the day install sun tracking systems that help maintain the right angle of incidence of the rays on the solar panels. But these systems are quite expensive, not to mention the batteries themselves, so not everyone can afford to install them to power their homes.
How much energy a solar panel produces, also depends on the total area of the installed modules, because each photovoltaic cell can take a limited amount of solar energy.
The cost of solar panels and batteries
of panels and batteries have a wide range, due to the many variants of design, power and other parameters. However, the costs should be calculated only on the basis of the estimated composition of the solar power plant, which includes quite certain types of equipment.
Note! It is not advisable to purchase the equipment separately, because the result can be heterogeneous equipment that is not able to work in tandem. It is better to buy ready complexes, consisting of fully compatible equipment.
The initial cost of the plant is 5 thousand rubles. and increases in proportion to the capacity, battery capacity and other features of the complex. There is practically no upper limit, since the number of solar panels can be infinite.
How to optimally calculate the parameters of a solar plant for your needs?
Very often, when applying for the selection of equipment or when choosing a solar power plant customers ask: How to calculate the capacity and number of solar panels and batteries and how much power to choose a solar power plant. In this article we will try to deal with this issue, and I will try to explain in simple language, without going into details how to do it.
The first thing you need to know how much electricity you consume per day, this can be done by taking the average monthly electricity meter reading and divided by 30 days. That’s how we get the average consumption per day. For example, the social norm in the RO for two people is 234kW, which is about 8kW.hours of electricity per day. Accordingly, we need the solar panels to produce the same amount of energy per day.
Latitude and longitude depth of the problem
Imagine you are a scientist. you find an interesting article, but the results/experiments cannot be reproduced in the lab. It makes sense to write to the authors of the original article and ask for advice and clarifying questions. According to the survey, less than 20% have ever done this in their scientific career!
over, an absolute minority of scientists have attempted to publish a refutation of non-reproducible results, facing opposition from editors and reviewers who demanded that the comparison with the original study be downplayed. Is it any wonder that the chance of reporting non-reproducibility of scientific results is in the order of 50%?
Question one: Have you tried to replicate the results of the experiment?
Second question: Have you tried to publish your attempt to reproduce the results??
Maybe we should at least conduct a reproducibility check inside the lab then? The saddest part is that a third of the respondents had NEVER even considered creating methods to test the data for reproducibility. Only 40% indicated that they regularly use such methods.
Question: Have you ever developed special techniques/techniques.processes to improve reproducibility?
Another example, a biochemist from the United Kingdom, who did not want to reveal her name, said that attempts to repeat, reproduce the work for her laboratory project just double the time and material costs, without giving or bringing 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?
What set of photovoltaic installation to buy for a private home
The development of engineering has led to the creation of three main categories of photovoltaic systems. Each of them has design and technological features and differs in some nuances of functioning.
Solar panels of the I category. autonomous
The main difference between the systems of this group is the lack of connection to the centralized power supply network. The equipment connected to the installation receives direct power. Stand-alone systems are equipped with batteries, allowing an uninterrupted power supply during periods of lack of sunlight.
Solar panels of category II. open
This equipment is connected to the centralized power supply system through an inverter. Battery not included. When the power consumption becomes higher than the generated power, the photovoltaic system shuts down, switching appliances to be powered from the main grid. In the opposite situation the central power grid is blocked. This is the most economical and reliable option. However, in the absence of a complete centralized power supply, the system cannot be operated.
Solar panels of III category. combined
Special feature of the installation is the flow of surplus electricity into the main grid. Solar panels with this configuration are the most expensive.
Tip! In the event of a simultaneous failure of the main power supply channel and a shortage of sunlight, a small-scale power generator should be purchased. This step protects against unexpected power outages at home.
Deciding to switch to economical mode of electricity supply at home, it is important to consider the price not only for the set, but also for its installation and maintenance. A specific cost of solar panels is quite difficult to name, since its formation is influenced by more than one factor.
It is not difficult to calculate the cost of acquisition of a set, which generates 100-200 W of power (enough for a small house). 6000-12000 It is worth noting that this calculation covers the attention of photovoltaic equipment of the lowest quality.
For a set of category I, characterized by the nominal capacity of 2 kW will have to pay at least 120,000
When choosing a set of solar panels for a private home, it is also important to consider the guarantee of uninterrupted power supply. This is especially important to maintain the stable operation of heating systems installed in the house, outdoor and indoor surveillance, fire alarms and computer software.
To understand how appropriate in a particular case the purchase of a set of solar panels for the house, you need to do the following: compare the cost per unit of power produced by a centralized power grid with the price of the same amount of power transformed from sunlight. Carrying out comparison of the now in force, shows that such parity makes 8-9 times in favor of the photovoltaic equipment.
Output voltage of solar panels.12 V, 24 V and more. The characteristics of the elements of the kit allow them to be used separately, without connecting the whole kit. Recall, in order to get 1 Watt it is necessary to spend about 60 for photovoltaic equipment.
To get 1 watt from solar energy you need to spend about 60
Let’s move on to the specifics of local use. For example, if you need a 25 W light bulb for lighting a small area with a voltage of 12 V, you can buy a solar panel with suitable parameters for this purpose, which will cost about 2000. To the non-volumetric photovoltaic system, you can connect a small well pump with the parameters. 200 watts and 24 V. The irrigation system based on it will serve more than 10 years and will cost about 12,000
Solar panel kit for the cottage
When planning the use of a photovoltaic system in the dacha, it is important to consider several nuances:
- stability of centralized electricity supply in the area;
- The risk of theft during the period of absence from the dacha;
- The necessary power of electrification.
Most often a set of solar panels of category I, i.e. autonomous type, is installed on the dacha. Autonomous power supply for a building with low energy consumption is financially beneficial. In some cases a mobile kit is used.
Interesting! According to the data obtained by analysis, it is found that the use of photovoltaic systems for a country house with an area of up to 300 square meters is advantageous.
Solar off-grid heating system for your home
Not only photovoltaic systems, but also collectors for heating and water heating are based on solar energy. When using quality installation can save more than 30% of the money spent on these needs.
Solar collector is a panel 10 cm thick with an area of 1 × 2 m. Varieties within the specified dimensions differ from each other by the coefficient of heat loss, which reflects the amount of thermal energy transferred to the liquid coolant. For a modern solar collector panel this value is 1.2-5 W/m² × °K.
It is important to understand that when it comes to the price of solar thermal plant for home, usually means the purchase of a complete set. It includes a pump, tank, accumulator and other components. For such a set on average you need to pay from 100 to 170 thousand rubles. rubles. It is worth noting that when you buy a system of domestic manufacturers can save about 50-60 thousand. rubles.
If we consider the domestic counterpart will cost on average 15% cheaper, the Chinese. 40% cheaper.
Important! The cost of hot water can be reduced by more than half if you combine a system of collectors and batteries, working on the radiation of daylight.
Example of calculation of solar panels for the house
Whether we admit it or not does not change the essence. Very often we, proceeding to the implementation of serious, moreover, less serious their plans, neglect projects or calculations. This usually does not lead to the expected results, or the resulting time or material costs are not expected at all. Of course everything must be calculated. Hardly anyone would disagree with this.
With regard to solar panels, the calculation of their capacity is a must, since the slightest deviation in any direction leads to a change in material costs by an order of magnitude.
There is another indisputable benefit of the calculation procedure forms a conscious clear understanding of the order of operation of the future solar power plant. Only a person who operates in his house autonomous power system, to fully understand what it means.
And understanding this boils down to one thing: how to conserve every watt hour of energy produced. In a house that is powered by an autonomous system, you won’t see glowing light bulbs unnecessarily, as is often the case with a traditional power supply.
In the process of using a solar power plant, you may have devices in your home such as motion sensors, timers for automatic control of lighting, photo relays to control outdoor lighting, etc.д. It’s going to be the norm.
You shouldn’t be surprised that I spend so much time on this. You really need to know and understand this. Some would categorize the need to control every watt hour as a disadvantage, I would not agree.
Firstly, let’s remember those who simply do not have other options for power supply. Second, when did this sensible savings become, suddenly, a disadvantage! Agree that it would be wasteful “investing” Knowingly pour more money into the electrical system only to squander energy uncontrollably.
The first step in calculating a solar plant is to calculate the total load of the consumption of your home. There are many examples of these calculations in various interpretations, both with narrative and online. Nothing new to invent in this case. First you set a goal, then look for ways to achieve it. It’s the same here: first the needs are clarified, and then the technical and material capabilities to meet them are calculated.
Calculation of the total consumption load
This is the first stage of the calculation. It starts with the fact that you take a blank sheet of paper and on it make a list of all appliances and devices that you expect to use in the house. You start by making this list without going into the quantitative and qualitative composition of it. At the first stage of the calculation, if you have not had a chance to do it, it is difficult to conclude whether or not to keep a particular device in the list. We will add, delete or replace after the order of material costs will be clear.
The next step is to find out the power consumption of each of the devices. You can find this out from the data sheets of appliances or look at the tags on the appliances themselves, which show their characteristics, including the power consumption. In extreme cases, if there are no passports and labels, you can find out the necessary information from sales managers in stores. And finally, if you have the Internet at your fingertips, you can search for this data with the help of search engines.
I give some approximate numbers just to show the order of the steps:
|Energy saving lamp||8|
If you pay attention to the first two positions, then, as you can see, I have separated lamps with different power consumption. There is no need to put lamps in small and seldom visited rooms the same as in living rooms. And since the next step is to enter the total time of operation of these devices during the day, it makes no sense to combine these lamps in one position.
Enter the number and total working time per day:
|Name||Power, W||Qty, pcs.||Time, hour|
You should explain the results in the last column. For example, if you use the vacuum cleaner not every day, but once a week for 2 hours, then in a month the total time is 2 X 4 = 8 hours, t.е. per day 8 hours : 30 = 0.3 hours. Same with the pump. If you have to pump water, let’s say twice a week and it takes 2 hours, then 2 X 2 = 4 hours, 4 X 4 = 16 hours, 16 : 30 = 0.6 hours. Rounded up, of course.
Now we can calculate how much electricity each of the devices consumes per day:
|Name||Power, W||Qty, pcs.||Time, hour||Watt-hour|
|Energy saving lamp||8||3||0,2||4,8|
The final stage of calculating the daily consumption add up all the results of the last column. The result is: 7919,8 Wh per day.
Well, let’s start calculating the solar cells. We have a daily consumption of 7919.8 Wh, from which we will “refer to”.
Selecting the value of DC voltage of the system
Selecting the value of the system voltage is necessary, firstly, for the selection of the system devices in terms of their voltage consistency, inverter, battery charge controller, and secondly, the value of this voltage will depend on the connection schemes of solar modules and batteries, well, and thirdly, for further calculations of the solar cells.
Usually for autonomous power supply systems of a private residential house choose either 12 V or 24 V. Unless, of course, the power supply system is not too powerful and this, its power, does not force to resort to a voltage of 36 V or, say, 48 V in order to reduce currents in circuits, and thus be able to use a wire with a smaller cross section, t. е. cheaper.
In our case I suggest to stick to the following logic: if you are not planning to increase the power supply system, and you expect to be limited to 1000 watts or 2000 watts, it is enough to stop at 12 V.
In case you plan to increase it, in addition, to operate in the winter, it is more reasonable to build a 24-volt system. It is reasonable because at a certain stage of operation of power supply system you are likely to come to the inevitability of augmenting it with a wind generator. This is quite logical and gives the system an undeniable advantage in operation all year round. We will talk about it when we touch the topic of wind turbines.
So you do not have to change once installed devices, it is better to choose the option at once for 24 V, then a wind turbine generator with 24 V output without much difficulty fit into your existing system.
And so. Let’s assume that we stop at the variant of power supply system of 24 V. I make this choice in our example to show a more obvious example of calculation. You do what you think is necessary based on your data, of course with this in mind.
Determining the required amount of energy per day
In order to determine the necessary amount of energy per day, we must divide our calculated value of daily consumption of 7919.8 W by the selected system voltage of 24 V. The result of this division will be 330 Ah.
But we must not forget that the inverter itself consumes some energy for its own requirements. So we have to have a reserve of energy for it as well. Proceeding from that we will multiply obtained result of 330 Ah by coefficient of 1,2 and get 396 Ah.
So we have calculated the daily amount of energy necessary to supply our customers with electricity. And it’s 396 Ah.
What we must not forget when choosing the solar modules
Undoubtedly the electrical characteristics of photovoltaic modules are of paramount importance. Power, voltage, current. But you should also pay attention to such parameters as dimensions, design, weight, etc. д.
Let’s list the characteristics and parameters of these devices in order, and at the same time note how a particular value of these indicators may affect the further operation.
Let’s start with voltage, of course. From the choice of voltage magnitude will determine the choice of battery charge controller, the choice of battery voltage and, accordingly, their connection scheme.
In this choice there is no dogma, you can choose any voltage. But! The most important thing is that it should be standardized. Otherwise, you will find it difficult to select equipment such as a charge controller, inverter, batteries. Even based on the standardized line of voltages, it makes sense to see what voltages are available for all the necessary devices. This is usually 12 volts, 24 volts, 48 volts.
A small remark should be made here. Did you pay attention to the fact that the value of voltage, and there are usually two of them for a photovoltaic module (maximum and no-load voltages), differs from the standard one upwards. It is necessary to ensure that the batteries are fully charged. This margin is intended to compensate losses in the system and takes into account the work of the module in real conditions, when the solar insolation is not equal to 1000 W / sq. km. m, the temperature does not correspond to 25 degrees Celsius.
We have settled on 12, 24, 48 volts. It does not make sense to choose other values for the reason that it will be more difficult to find a device with a different voltage, if necessary. Why knowingly create difficulties for yourself?
It should be taken into account that some modules are designed for non-standard voltages and intended for operation with network inverters. For this reason we are not interested in them.
In general, the main principle of constructing any system should be if possible, to avoid using unique devices. Nodes and devices must be standard and as accessible as possible. Only in this case you can guarantee the long lifetime of your system.
Of course you get the total power from those modules, the voltage of which corresponds to the one you have chosen for your system. I don’t need to remind you that they should have the same characteristics.
By connecting them either in parallel, if the voltage of each of them is equal to the selected one, or in series, if the voltage of each of them is less than the selected one. Well, in series-parallel to provide the total power at the selected voltage of the system. Who missed the article “Diagram of solar panels connection”, I recommend that you read.
Once you have decided on the number of modules and the scheme of their connection, you can on the basis of the resulting current make the choice of the charge controller, because the voltage of the system you have already selected.
Remembering this truth, that every additional electrical connection in the system increases the probability of failure, we understand that a single module corresponding to the required power and voltage, would be ideal for us. No extra connections, no extra wires.
But we know that’s impossible. And by and large you don’t need it. Not necessary, if only because in this case we would deprive our system of flexibility, and maintainability would also suffer. Not to mention weight, which will play an important role in installation.
It would be much harder to ramp up the system, to change the system voltage, if that were needed. To repair the module, after all. High sailor’s weight, again. This also should not be discounted, because you are going to mount the modules on a surface exposed to all winds.
However, without forgetting about the mentioned truth, we must pay attention to the size of the modules in terms of installation (not every size will allow installation without lifting mechanisms), laying on the roof (no shading throughout the daylight hours).
On the other hand too small in size will cost more.
Design also plays an important role, both from a performance and financial point of view. Frameless modules, for example, will cost less, but they can and should be used only if you have the opportunity to perform the installation in such a way as to ensure their normal operation without frames.
Or you have the opportunity to build a frame yourself and it will cost you less. Only the issue of sealing the module should be taken into account, because if air and moisture get in, the contacts oxidize. This significantly reduces their service life.
Things like glass. They come in different sizes and the price also depends on that. Conventional glass leads to losses of up to 15% due to reflection. Glasses that can withstand impact may be superfluous, but glass with an increased degree of transparency makes sense to consider.
Solar Panels Behind Glass
People often ask us how much the yield of solar panels would decrease if they were installed behind glass. inside a balcony, porch, etc.п. Many dachshunds fear that an externally installed solar panel will be stolen. Some people try to make the installation of solar panels inconspicuous.
Solar panels use special glass with increased transparency, which is achieved by reducing the amount of iron in the glass, but even this reduces the capacity of the solar panel by several percent. As you can see from the table above, single pane window glass reduces solar panel output by 9%, while double pane glass reduces solar panel output by 16%. That’s assuming those panes are perfectly clear and the sun’s rays fall on them perpendicularly. In reality the glass pane can be dusty or even dirty which further reduces its transparency. When sunlight falls at an angle other than 90 degrees, the front and back surfaces of each pane produce re-reflections that also deflect sunlight away from the solar cell. That is why we do not recommend installing solar panels behind window panes.
Solar panels behind glass on the balcony
Solar panel power calculation
The power of solar panels for stand-alone systems is selected based on the required power output, time of year and geographical location.
The required output power is determined by the power required by the electrical consumers that are planned to be used. In the calculation it is worth considering losses on conversion of direct voltage into alternating voltage, charge-discharge of batteries and losses in conductors.
Solar radiation is not constant and depends on many factors. time of year, time of day, weather conditions, and geographic location. These factors must also be taken into account when calculating the amount of solar panel power required. If you plan to use the system year-round, the calculation should take into account the most unfavorable months in terms of solar radiation.
When calculating for each specific region, it is necessary to analyze statistical data on solar activity for several years. On the basis of these data, determine the averaged actual solar flux power per square meter of the Earth’s surface. These statistics can be obtained from local or international weather services. Statistical data will allow you to predict with minimum error the amount of solar energy for your system, which will be converted into electricity by the solar panels.
As an example, let’s look at the average daily insolation by month from one of the servers of the weather service for g. of Moscow. The data are given with consideration of atmospheric phenomena and are averaged for several years.
Insolation measurement unit in the table is kWh/m2/day.
Tilt angle of the plane, degrees to the ground (0 °. insolation to the horizontal plane, 90. insolation to the vertical plane, etc.). п.), with the plane oriented to the South.
|Jan.||Febr.||March||Apr.||May||June||July||Aug.||St.||Oct.||November.||Dec.||Average annual insolation kWh/m2/day|
As can be seen, the most unfavorable month for this region is December, the daily average insolation on the horizontal surface of the ground is 0.5 kWh/m2 / day, on the vertical. 1.22 kWh/m2 / day. At an angle of inclination of the plane relative to the earth 70 degrees insolation will be 1.26 kWh/m2 / day, the optimum angle for December is 74 degrees. The most favorable month is June and insolation on the horizontal surface will be 5,27 kWh/m2/day, the optimal angle of inclination for June is 11 degrees.
The angle of inclination of the solar panel, when used year-round in a system that consumes on average the same power regardless of the season, should coincide with the optimal angle of inclination of the most unfavorable month in terms of the amount of solar radiation. Optimal angle of slope for December in. Moscow is 74 degrees, and thus should install a solar panel, as in other months insolation is noticeably greater, and as a consequence, the production of electricity will be more than enough. over, in winter, at angles of inclination of 70-90 degrees, the solar panel will not accumulate precipitation in the form of snow. If the task is to obtain maximum power from solar panels throughout the year, it is required to constantly orient the solar panel as perpendicular to the sun.
Formula for calculating the power of solar panels
Eins. average monthly insolation (from the table) kWh/m2/day;
Rins. power of insolation on the ground surface on one square meter (1000 W/m2);
k. coefficient of losses on charging. discharging of accumulators, conversion of direct voltage into alternating voltage, usually taken equal to 1.2-1.4.
Formula for calculating the energy produced by solar panels
Eu. generated energy by solar panels, Wtch per day;
Eins. monthly average insolation (from the table) kWh/m2/day;
Rins. power of insolation on the ground surface on one square meter (1000W/m2);
k is the coefficient of losses on charging. discharging of batteries, conversion of direct voltage into alternating voltage, usually taken equal to 1.2.
Characteristics of solar panels
Solar cells, also called solar panels or solar modules, are constructed of individual photovoltaic converters (so-called solar cells) which are connected to one another in series and parallel circuits that together act as a single current source.
One panel can be considered as a power source. Several solar panels form an autonomous solar power plant, which can be small (if it is a private house for example) or large (if it is an industrial solar power plant) capacity. The size of a solar plant depends on its purpose and the needs of its consumer.
One solar panel usually contains a multiple of 12 cells, viz: 12, 24, 36, 48, 60 or 72 solar cells. Nominal power of one such panel is usually in the range of 30 to 350 watts. Accordingly, the size and weight of the panel is the greater, the greater its nominal capacity.
To date, the real efficiency of solar panels available to the general consumer is in the range from 17 to 23%. There are some specimens that declare efficiencies of up to 24%, but these are exceptions and exaggerations. Laboratories around the world are striving to develop solar cells with efficiencies of at least 30%. that would be a very good result for a power source of this type, if you look at things realistically.
Silicon-based solar cells as an alternative source of electrical power are time-tested, reliable and safe, compact and relatively affordable. Their normal service life is up to 30 years or even more. Although, to be fair, it is worth noting that the silicon photovoltaic cells degrade over time, it is reflected in a decrease in the received power in full lighting by about 10% of the original rating for every 10 years of active operation.
That is, if in 2020 a new solar panel was purchased for 300 watts, by 2040 it will be able to generate a maximum of 240 watts. For this reason, the installed capacity of the system should be calculated with a certain current reserve. As for the thin-film cells they are not time tested but specialists say that their degradation rate in the first years is several times higher than that of monocrystalline and polycrystalline silicon cells.
During normal operation, neither cell replacement nor any other special maintenance is required for monocrystalline and polycrystalline solar panels. They are easy to install, contain no moving parts and their sun-facing surface is always mechanically stable.
The volt-ampere characteristic of solar cells is taken in the laboratory during production and is given in the data sheet. The standard test is carried out at solar radiation of 1000 W/sqm.m at an ambient air temperature of 25°C, as at latitude 45.
Here we can see the extremes of the CVC at which the power delivered by the battery is converted to zero. No-load voltage Voc. is the maximum available voltage at the battery output when the load circuit is open. The current at short-circuited load circuit Isc is, respectively, the current at zero output voltage.
In practice, the battery is always operating in some optimal mode somewhere in between these two points. At the optimal point of the MPP. maximum load power. The nominal voltage for the maximum power point is denoted by Vp and the nominal current for that point by Ip. At this point the efficiency of the solar panel is also determined.
In principle, the solar panel is capable of working at any point of the CVC, but to get maximum efficiency, it is useful to use the point of highest power, so solar panels never feed the load directly. For best efficiency, a charge controller with MPPT technology should be connected between the solar panel and the batteries (inverter), which will always operate at the maximum power available at any current solar intensity.