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Feasibility and payback of solar panels. The most efficient solar panels: efficiency, power and voltage ratings

The record holder for efficiency among solar batteries available on the market today are solar batteries based on multilayer photocells, developed by the Fraunhofer Institute for Solar Energy Systems in Germany. Since 2005, their commercial implementation has been carried out by Soitec.

The size of the photocells themselves does not exceed 4 millimeters, and focusing sunlight on them is achieved by using auxiliary concentrating lenses, thanks to which saturated sunlight is converted into electricity with an efficiency reaching 47%.

The battery contains four p-n junctions so that four different parts of the photocell can effectively receive and convert radiation of a specific wavelength, from sunlight, concentrated 297.3 times, in the wavelength range from infrared to ultraviolet.

Researchers led by Frank Dimiroth initially set themselves the task of growing a multilayer crystal, and a solution was found - they spliced ​​growth substrates, and the result was a crystal with different semiconductor layers, with four photovoltaic subcells.

Multilayer photocells have long been used on spacecraft, but now solar stations based on them have been launched in 18 countries. This is becoming possible thanks to improved and cheaper technology. As a result, the number of countries equipped with new solar stations will increase, and there is a tendency for competition in the market for industrial solar panels.

In second place are solar batteries based on Sharp three-layer photocells, the efficiency of which reached 44.4%. Indium gallium phosphide is the first layer of the solar cell, gallium arsenide is the second, and indium gallium arsenide is the third layer. The three layers are separated by a dielectric, which serves to achieve a tunnel effect.

The concentration of light on the photocell is achieved thanks to a Fresnel lens, like the German developers - the light of the sun is concentrated 302 times and converted by a three-layer semiconductor photocell.

Scientific research into the development of this technology has been continuously conducted by Sharp since 2003 with the support of NEDO, a Japanese public administration organization promoting scientific research and development, as well as the dissemination of industrial, energy and environmental technologies. By 2013, Sharp had achieved a record of 44.4%.

Two years before Sharp, in 2011, the American company Solar Junction had already released similar batteries, but with an efficiency of 43.5%, the elements of which were 5 by 5 mm in size, and focusing was also carried out by lenses, concentrating the light of the sun 400 times. The solar cells were three-junction germanium-based cells, and the team even planned to create five- and six-junction solar cells to better capture the spectrum. Research is still ongoing by the company.

Thus, solar panels made in combination with concentrators, which, as we see, are produced in Europe, Asia, and America, have the highest record efficiency. But these batteries are mainly manufactured for the construction of large-scale ground-based solar power plants and for efficient power supply to spacecraft.

Recently, a record has been set in the field of conventional consumer solar panels, which are affordable for most people who want to install them, for example, on the roof of a house.

In mid-autumn 2015, Elon Musk's company SolarCity introduced the most efficient consumer solar panels, the efficiency of which exceeds 22%.

This indicator was confirmed by measurements carried out by the Renewable Energy Test Center laboratory. The Buffalo plant already sets a daily production target of 9 to 10 thousand solar panels, the exact characteristics of which have not yet been reported. The company already plans to supply at least 200,000 homes annually with its batteries.

The fact is that the optimized technological process allowed the company to significantly reduce the cost of production, while increasing the efficiency by 2 times compared to widespread consumer silicon solar panels. Musk is confident that his solar panels will be the most popular among homeowners in the near future.

Billions of kilowatts of solar energy reach our planet every day. People have long begun to use this energy for their needs. With the progress of progress, solar panels began to be used to convert the energy of sunlight. But are these devices effective? How much is the efficiency of solar panels, and what does it depend on? What is their payback period and how can you calculate the profitability of using solar panels? These questions concern everyone who is planning or has already decided to purchase solar panels, so this article is devoted to this pressing topic.

Let's briefly look at what the principle of operation of solar panels is based on. It is based on the physical property of semiconductors. Due to the knocking out of electrons from the outer orbit of atoms by light photons, a sufficiently large number of free electrons are formed. After the circuit is closed, an electric current occurs. But, as a rule, one or two solar cells are not enough to generate sufficient power, therefore, solar modules most often include several solar batteries. The more solar cells are connected together, that is, the larger the area of ​​the solar panels, the greater the power they produce. In addition to the area of ​​the panels, the intensity of sunlight and the angle of incidence of the rays have a noticeable impact on the power produced.

Let's understand the concept of efficiency

The efficiency value of a panel is obtained by dividing the power of electrical energy by the power of sunlight falling on the panel. Today, the average value of this indicator in practice is 12-25%, but in theory this figure is close to 80-85%. What is the reason for such a big difference? First of all, it depends on the materials used to make solar panels. As is already known, the main element included in the panels is silicon. One of the main disadvantages of this substance is its ability to absorb only infrared radiation, that is, the energy of ultraviolet rays is wasted. Therefore, one of the main directions in which scientists are working, trying to increase the efficiency of solar panels, is the development of multilayer modules.

Multilayer batteries are a structure consisting of layers of different materials. They are selected based on quanta of different energies. That is, one layer absorbs green energy, the second - blue, the third - red. In theory, various combinations of these layers can give an efficiency value of 87%. But this, unfortunately, is just a theory. As practice shows, the manufacture of such structures on a production scale is a very labor-intensive task, and the cost of such modules is very high.

The efficiency of solar modules is also affected by the type of silicon used. Panels made from monocrystalline silicon have a higher efficiency than panels made from polycrystalline silicon. But the price of monocrystalline batteries is higher.

The basic rule: with a higher efficiency, to generate electricity of a given power, a module of a smaller area will be required, that is, a smaller number of photocells will be included in the solar panel.

How quickly will solar panels pay for themselves?

The cost of solar panels today is quite high. And taking into account the low efficiency of panels, the issue of their payback is very relevant. The service life of batteries powered by solar energy is about 25 years or more. We’ll talk about what causes such a long service life a little later, but for now let’s clarify the question raised above.

The payback period is affected by:

  • Type of equipment selected. Single-layer solar cells have lower efficiency compared to multilayer ones, but also have a much lower price.
  • Geographical location, that is, the more sunlight in your area, the faster the installed module will pay for itself.
  • Cost of equipment. The more money you spent on purchasing and installing the elements that make up the solar energy saving system, the longer the payback period.
  • The cost of energy resources in your region.

The average payback period for the countries of Southern Europe is 1.5-2 years, for the countries of Central Europe - 2.5-3.5 years, and in Russia the payback period is approximately 2-5 years. In the near future, the efficiency of solar panels will increase significantly, this is due to the development of more advanced technologies that will increase efficiency and reduce the cost of panels. And as a result, the period during which the solar energy saving system will pay for itself will also decrease.

How long will solar panels last?

Solar panels do not contain mechanical moving parts, so they are quite reliable and durable. As mentioned above, their service life is more than 25 years. With proper use, they can last 50 years. The big advantage is that such a long service life does not require major breakdowns; you just need to systematically clean the photocell mirrors from dust and other contaminants. This is necessary for better energy absorption, and, consequently, for a higher efficiency rate.

A long service life is one of the main criteria when deciding whether to purchase solar panels or not. After the batteries pay for themselves, the electrical energy you receive will be absolutely free. Even if the payback period is maximum (about 6 years), you will not pay for energy resources for at least 20-25 years.

Latest developments that increase efficiency

Almost every day, scientists around the world announce the development of a new method to increase the efficiency of solar modules. Let's get acquainted with the most interesting of them. Last year, Sharp introduced to the public a solar cell with an efficiency of 43.5%. They were able to achieve this figure by installing a lens to focus energy directly into the element.

German physicists are not far behind the Sharp company. In June 2013, they presented their photocell with an area of ​​only 5.2 square meters. mm, consisting of 4 layers of semiconductor elements. This technology made it possible to achieve an efficiency of 44.7%. Maximum efficiency in this case is also achieved by placing a concave mirror at focus.

In October 2013, the results of the work of scientists from Stanford were published. They have developed a new heat-resistant composite that can increase the performance of solar cells. The theoretical efficiency value is about 80%. As we wrote above, semiconductors that contain silicon are capable of absorbing only IR radiation. So, the action of the new composite material is aimed at converting high-frequency radiation into infrared.

The next were English scientists. They have developed technology that can increase the efficiency of cells by 22%. They proposed placing aluminum nanospikes on the smooth surface of thin-film panels. This metal was chosen because sunlight is not absorbed by it, but, on the contrary, is scattered. Consequently, the amount of solar energy absorbed increases. Hence the increase in solar battery performance.

Here are only the main developments, but the matter is not limited to them. Scientists are fighting for every tenth of a percent, and so far they have succeeded. Let's hope that in the near future the efficiency of solar panels will be at the proper level. After all, then the benefits from using the panels will be maximum.

The article was prepared by Abdullina Regina

Moscow is already using new technologies for lighting streets and parks, I think the economic efficiency has been calculated there:

Let's consider the question of how feasible it is to install solar panels to power a country house or even an apartment. Prices are current for the spring of 2017, calculations of battery production for the North-Western and Central regions of Russia.

People usually want to use solar panels in three cases:

1. There is no electricity in the house at all, that is, city power is not connected

2. Electricity often goes out for several hours or even days.

3. There is electricity, but they want to save money

Let's consider all three cases. Let's see what is needed to calculate the payback of batteries, and how feasible they are in these three cases.

1. There is no electricity at all

That is, there is no city power line and is not expected. Or its installation costs a lot of money, then you need to evaluate whether it is worth investing in a solar power plant or whether it is better to pay for the supply line.

Here is a general diagram of a solar power plant. The batteries provide electricity (from 5 to 30 volts depending on the lighting), the controller makes them 12 or 24 or 48 volts, which charge the batteries (one battery - 12 volts, two - 24 volts, 4 -48 volts or depending on the type their connections).

The inverter makes 220 volts of alternating current from the battery voltage and powers the loads in the house. If there is a city power line, then the inverter can charge the batteries from it; when the power is turned off, it will instantly switch to generating a 220 volt sine wave.

You need to decide on two numbers: the maximum peak consumption of the house and the amount of electricity needed per day. Peak demand determines the maximum power an inverter can provide. And the amount of electricity (measured in kilowatt-hours per day) is the main characteristic that we need. This figure determines how much electricity should be obtained from the batteries. This figure is calculated by the electric meter.

Let’s take an average small “temporary” type house. For example, a refrigerator consumes 100 watts per hour on average, running 24 hours a day = 2400 watt-hours per day.

Light bulbs consume 100 watts per hour, 6 hours per day = 600 watt-hours per day.

A TV consumes 100 watts per hour, 6 hours per day = 600 watt-hours per day.

In total we get 3600 watt-hours per day.

Taking into account the inverter’s own consumption and the fact that we still need to charge the phone and turn on the laptop for a couple of hours, we get 4 kilowatt-hours per day.

In the calculator, enter 4 in the “average load” field, select the region and look at the generation and consumption curves. Let's take larger batteries (monocrystalline, 230 watts, 6 pieces). We see that from February to September our need for electricity is almost covered.

Here we come to the main problem of our region - in winter, electricity generation is much lower than in summer. In May-June we have 8.5 kilowatt-hours of electricity per day, from November to February - 2-3. That is, we need to either greatly increase the number of batteries so that the output is sufficient in winter (the batteries will pull a more powerful controller with them, the whole system will become more expensive), or use a generator in winter (especially if we plan to turn on electric heaters).

We count equipment for our system “from February to September.” Prices spring-summer 2017, retail.

6 batteries of 240 watts = 12,000 * 6 = 72,000 rubles.

Controller (makes the battery output voltage 12 or 24 volts). Let there be a 48-volt system, then the required controller power = 240 * 6 /48 = 30 amps. A good 30 amp 48 volt controller costs 35 thousand.

The inverter turns 48 volt batteries into 220 volts to power the home. Let's say that our maximum power consumption at home will not exceed 3 kilowatts (so that we can turn on the kettle). Inverter MAP "Energy" SIN Pro 48/220V 3.0 kW costs 47 thousand.

Batteries are needed to store energy and release it when there is no sun or at night. We have a 48 volt system, which means we need at least 4 12 volt batteries.

Battery Delta GX12-100 * 4 pieces = 60 thousand rubles.

Plus a metal rack for all equipment, a fuse, an SPD, a special large-section cable (all this is needed to protect the system) = approximately 16 thousand.

Total 230 thousand rubles. With professional installation, consumables and delivery - all 260 thousand rubles.

This is how solar power plants are considered. If no more appliances will be used in our temporary hut, and we don’t go there in winter (or don’t use a refrigerator and electric heater), then such a system will be completely justified.

2. Electricity often goes out

Example: there is basic electricity, the maximum consumption at home is 5 kilowatts. Consumption during a power outage (if we manually turn off the most powerful loads, we will leave what is necessary) - 3 kilowatts. Power outages are possible for up to 3 hours.

We take the inverter MAP “Energy” SIN Pro 24/220V 6.0 kW = 72 thousand.

Important thing! One inverter works per phase! That is, if we have all the important loads hanging on one phase, then fine, we install an inverter, but if they are distributed over all three phases, then we need three inverters, there is no escape from this. Three 5 kilowatt inverters (as is usually the case in houses) = 216,000 rubles.

We hold 3 kilowatts for three hours = 9 kilowatt-hours should be stored in the batteries. We don’t count solar panels at all yet; they will provide little energy in 3 hours, especially not in the summer or in the evening. There is no hope for them; we believe that the batteries are charged from electricity.

9000 watt-hours / 12 volts (each battery is 12-volt) = 750 amp-hours. Batteries are discharged not to zero, but to 20% of capacity. The inverter efficiency is 93 percent (considered quite high). In total, we need to store 1008 ampere-hours of energy in the batteries.

We take batteries of 250 ampere-hours 12 volts. 4 pieces. By the way, they weigh 80 kg each. The price of a good gel battery with a service life of 10-12 years is 34,000 rubles.

Total inverter and batteries = 208,000 rubles. Plus connecting cable, rack, fuse = approximately 224 thousand rubles. Here is the complete solution to the problem.

If electricity will be lost frequently and for a long time, then you can add solar panels to this system, and in sunny months they will add battery life to the system. Or double the number of batteries.

You can also add a generator to the system that can be triggered by an external signal. The inverter, seeing that the batteries are almost empty, will start the generator and stop it after charging is complete. This will lead to the fact that the generator will not work all day, but a couple of hours a day.

3. There is electricity, but they want to save money

There are such hybrid inverters, they are more expensive than conventional ones, but they can mix electricity from solar panels and from the city network, reducing the meter readings.

Let's say we installed the system as in point 1, but with a hybrid inverter. Let's say 320 thousand with installation.

In the calculator below we see the total production for the year, it will be 1958 kilowatt-hours. Taking into account the efficiency of the inverter - 1821 kilowatt-hours. The cost of a kilowatt-hour of electricity in the Leningrad region from January 1, 2017 (daily tariff) is 3.89 rubles.

In total, we save 7,084 rubles a year. No such savings.

Payback period is 45 years. But the service life of solar panels is approximately 25 years. Batteries are 10-12 years old. The inverter is also 10-12 years old.

In total, we will get 2 advantages from such a system:

  • In the event of a short-term power outage, the house will continue to operate for some time (depending on the capacity of the batteries and the consumption of the house). That is, there is no need to install any uninterruptible power supplies on the equipment. And if we install a generator, there will be no loss of power during its startup (usually from 30 seconds to 2 minutes). The inverter switches power to backup batteries almost instantly.
  • Solar panels will be installed on the house. Neighbors will see that the owner of the house is a supporter of “green” technologies.

In total, if we lived in Europe, where there is more sun, electricity is several times more expensive, and equipment is cheaper (although I’m not sure about this), then, probably, we would be able to say that by the end of its service life the equipment will just pay for itself or will come close to this. But we are saving nature from the negative influence of power plants! This is important in Europe. We don't have it at all. So the option of saving is eliminated.

In Europe, it is even possible for a person to receive money from the electricity supplier that he has supplied to the general network from his batteries. We sell meters that can turn in the opposite direction, but there is no such option by law.

    • - not a new invention. For more than half a century, humanity has been using solar radiation to supply electricity to a wide variety of devices and devices. However, batteries of this type have not yet become widespread and have not displaced other energy sources from the market. One of the reasons for this is that solar panels are not always sufficiently efficient.

    A solar panel or battery is a device that can convert the energy contained in solar radiation into electricity.

    depends on many factors:

    • materials;
    • weather;
    • Battery Type.

    Standard efficiency of solar panels widely used for personal use , the value is considered approximately equal to 20%. For some types of devices this figure will be higher, for others it will be lower. But that's the average. This value shows what percentage of the light hitting the battery was converted into electricity.

    Of course, this is a very approximate definition, but generally correct. Batteries with efficiency of 50 and even 100% have already been created in laboratories. But for now these are only prototypes.

    Silicon panels

    The ideal operating efficiency of solar panels that use pure silicon as a semiconductor is 34% of the total light received. It must be borne in mind that in low light conditions, with diffused light, the batteries will capture less light, and the quantitative indicator of this 34% will decrease.

    • Silicon panels perform well in bright light, but are ineffective in diffuse light.
    • Polycrystalline have lower efficiency, but perform well in low light conditions.
    • (thin film) the panels are also quite effective in diffuse light.

    Hybrid panels

    The efficiency of silicon devices is relatively low, since they can only receive energy in the red part of the spectrum. The energy of the blue, the most energetically saturated photon, remains unused. Scientists around the world are actively working to solve this problem.

    One of the proposed options is the use of the aromatic carbon pentacene and the chemical compound PbS. This combination allows you to obtain more electrons and, as a result, generate more energy.

    The most efficient solar panels are multilayer cells, in which each layer performs its own task. The efficiency of these batteries can reach 87%. But these technologies are not yet used in mass production. As the number of layers increases, the cost of the battery also increases. To achieve 87% efficiency, you will have to make a very expensive solar battery.

    Devices based on the perovskite mineral are very promising. Now they are less efficient than silicon, but this is largely due to the novelty of the technology. Available test results suggest that in the future they are capable of taking first place in the alternative energy market.

    The efficiency of solar panels directly depends on their location. They should be facing south with the working surface and inclined at an angle equal to the latitude of the point at which they are located. The panels cannot be placed so that a shadow from a neighboring building falls on them, for example.

    A problem that you may encounter in winter is snow covering the work surface. In general, there are few solution options here: either clean it manually or change the angle of inclination. A useful device that can increase the efficiency of batteries is a tracker that rotates the panel to follow the sun.

    It is important to ensure that the system does not heat up too much, since overheating weakens the photoelectric effect. This can be avoided by installing a vented battery. Dust on the work surface also reduces the amount of energy generated. The system must be wiped down at least every two years.

    About the solar-powered base station. The caveat was that the payback period for a solar panel power system is 2-3 years. By profession, I am engaged in the installation and commissioning of systems of alternative energy sources and, as I see it, The authors of articles on this topic underestimate the time during which the system fully pays for itself, several times more.

    I don’t pretend to be absolutely accurate, but the numbers are not taken out of thin air, but from a specific facility where the team did the installation – the Simferopol production and warehouse complex “Myasko”. The calculations include the main most costly items.

    At the time of our work, this plant already had a farm with 300+ panels assembled using a modular system. We added six more circuits of twenty panels. (Circuit - combining a certain number of panels into one energy source, thus dialing the circuit of the voltage required for the inverter).

    Dry calculations

    Now a little about the numbers, all calculations are carried out with the cost of delivery to Crimea from Germany.


    Total:
    A truss of 120 panels costs $59,000. These calculations do not yet include wages for the designer, engineer and installers. In total, everything will result in a budget tending to $65,000.

    Actual power output

    Theoretically, under ideal conditions, one panel should produce approximately 220-230 W per hour (in terms of the usual 220 volts). Below are the graphs maintained by the control unit in the inverter; they can be monitored remotely.

    sunny day:

    Partly cloudy:

    Monthly chart:

    In the last graph, it should be taken into account that for two days the system was turned off for a while, and the first three days of the month and the last two are missing.

    In a consistently sunny summer month, with long daylight hours, such a farm will produce a maximum of 4500-4700 kWh. Knowing these numbers, you can calculate the profitability of the system, taking into account electricity tariffs.

    It should be taken into account that the farm was assembled without batteries; their presence would increase the total cost of the system and, accordingly, the payback time.

    Thus, I can’t achieve a payback period of 2-3 years. 10 years is a more or less realistic period.