Solar panels with high efficiency. The efficiency of solar panels of different types and ways to increase it. depends on many factors

Now you will learn what sellers will never tell you solar panels.

Exactly a year ago, in October 2015, as an experiment, I decided to enroll in the ranks of the “greens” who are saving our planet from premature death, and purchased solar panels with a maximum power of 200 watts and a grid inverter designed for a maximum of 300 (500) watts of generated power . In the photo you can see the structure of a polycrystalline 200-watt panel, but a couple of days after purchase it became clear that in a single configuration it has too low voltage, not enough for proper operation my grid inverter.

Therefore, I had to change it to two 100-watt monocrystalline panels. In theory they should be a little more efficient, but in reality they are just more expensive. These are high quality panels from the Russian brand Sunways. I paid 14,800 rubles for two panels.

The second cost item is a Chinese-made grid inverter. The manufacturer did not identify itself in any way, but the device was made with high quality, and an opening showed that the internal components are designed for a power of up to 500 watts (instead of 300 written on the case). Such a grid costs only 5,000 rubles. The grid is an ingenious device. On the one hand, + and - from solar panels are connected to it, and on the other hand, it is connected to absolutely any electrical outlet in your home using a regular electrical plug. During operation, the grid adapts to the network frequency and begins to “pump out” AC(converted from DC) to your 220 volt home network.

The grid operates only when there is voltage in the network and cannot be considered as a backup power source. This is its only drawback. And a huge advantage of a grid inverter is that you basically don’t need batteries. After all, batteries are the weakest link in alternative energy. If the same solar panel is guaranteed to work for more than 25 years (that is, after 25 years it will lose approximately 20% of its performance), then the service life of an ordinary lead-acid battery under similar conditions will be 3-4 years. Gel and AGM batteries will last longer, up to 10 years, but they also cost 5 times more than conventional batteries.

Since I have mains electricity, I don't need any batteries. If you make the system autonomous, then you need to add another 15-20 thousand rubles to the budget for the battery and the controller for it.

Now, as for electricity generation. All energy generated by solar panels enters the network in real time. If there are consumers of this energy in the house, then all of it will be used up, and the meter at the entrance to the house will not “spin”. If the instantaneous generation of electricity exceeds that currently consumed, then all the energy will be transferred back to the network. That is, the counter will “spin” in the opposite direction. But there are nuances here.

Firstly, many modern electronic meters count the current passing through them without taking into account its direction (that is, you will pay for the electricity sent back to the network). And secondly, Russian legislation does not allow private individuals to sell electricity. This is allowed in Europe and that is why every second house there is covered with solar panels, which, combined with high network tariffs, allows you to really save money.

What to do in Russia? Do not install solar panels that can produce more energy than the current daily energy consumption in the house. It is for this reason that I have only two panels with a total power of 200 watts, which, taking into account inverter losses, can supply approximately 160-170 watts to the network. And my house consistently consumes about 130-150 watts per hour around the clock. That is, all the energy generated by solar panels will be guaranteed to be consumed inside the house.

To control the energy produced and consumed, I use Smappee. I already wrote about him last year. It has two current transformers, which allow you to keep track of both the network electricity and the electricity generated by solar panels.

Let's start with theory and move on to practice.

There are many solar power calculators on the Internet. From my initial data, according to the calculator, it follows that the average annual electricity generation of my solar panels will be 0.66 kWh/day, and the total production for the year will be 239.9 kWh.

This data is for ideal weather conditions and does not take into account conversion losses DC into alternating voltage (you are not going to convert your household's power supply to constant voltage?). In reality, the resulting figure can be safely divided by two.

Let’s compare with actual production data for the year:

2015 - 5.84 kWh
October - 2.96 kWh (from October 10)
November - 1.5 kWh
December - 1.38 kWh
2016 - 111.7 kWh
January - 0.75 kWh
February - 5.28 kWh
March - 8.61 kWh
April - 14 kWh
May - 19.74 kWh
June - 19.4 kWh
July - 17.1 kWh
August - 17.53 kWh
September - 7.52 kWh
October - 1.81 kWh (until October 10)

Total: 117.5 kWh

Here is a graph of electricity generation and consumption in a country house over the last 6 months (April-October 2016). It was during April-August that the lion's share (more than 70%) of electrical energy was generated by solar panels. During the remaining months of the year, production was impossible largely due to cloudiness and snow. Well, don’t forget that the efficiency of the grid for converting direct current into alternating current is approximately 60-65%.

Solar panels are installed in almost ideal conditions. The direction is strictly south, there are no tall buildings nearby that cast a shadow, the installation angle relative to the horizon is exactly 45 degrees. This angle will give the maximum average annual electricity production. Of course, it was possible to buy a rotary mechanism with an electric drive and a sun tracking function, but this would increase the budget of the entire installation by almost 2 times, thereby pushing its payback period to infinity.

I have no questions about generating solar energy on sunny days. It fully corresponds to the calculated ones. And even a decrease in production in winter, when the sun does not rise high above the horizon, would not be so critical if not for... cloudiness. Cloudiness is the main enemy of photovoltaics. Here is the hourly output for two days: October 5 and 6, 2016. On October 5 the sun was shining, and on October 6 the sky was covered with lead clouds. Sun, oh! Where are you hiding?

In winter there is another small problem - snow. There is only one way to solve this: install the panels almost vertically. Or manually clear them of snow every day. But snow is nonsense, the main thing is that the sun is shining. Even if it’s low above the horizon.

So, let's calculate the costs:

Grid inverter (300-500 watts) - 5,000 rubles
Monocrystalline solar panel (Grade A - top quality) 2 pieces of 100 watts - 14,800 rubles
Wires for connecting solar panels (cross section 6 mm2) - 700 rubles
Total: 20,500 rubles.
Over the past reporting period, 117.5 kWh were generated; at the current daily tariff (5.53 rubles/kWh), this will amount to 650 rubles.
If we assume that the cost of network tariffs does not change (in fact, they change upward 2 times a year), then I will be able to return my investments in alternative energy only in 32 years!

And if you add batteries, then this whole system will never pay for itself. Therefore, solar energy in the presence of grid electricity can be beneficial only in one case - when our electricity costs the same as in Europe. If 1 kWh of network electricity costs more than 25 rubles, then solar panels will be very profitable.
In the meantime, it is profitable to use solar panels only where there is no network electricity, and its implementation is too expensive. Let's assume you have it country house, located 3-5 km from the nearest electric line. Moreover, it is high-voltage (that is, you will need to install a transformer), and you have no neighbors (no one to share the costs with). That is, you will have to pay approximately 500,000 rubles to connect to the network, and after that you will also have to pay network tariffs. In this case, it will be more profitable for you to buy solar panels, a controller and batteries for this amount - after all, after putting the system into operation, you will no longer need to pay any more.
In the meantime, it is worth considering photovoltaics exclusively as a hobby.

Science and technology do not stand still in the use of alternative energy, and the use of solar energy in everyday life and industry will continue to develop and improve, trying to displace traditional energy sources. Unfortunately, global dominance of solar energy is still far away and the reason for this is low efficiency solar panels.

Factors affecting the efficiency of solar panels

The efficiency of solar panels is influenced by objective and subjective factors, such as:

materials used in production,
technologies,
place of use (latitude),
angle of incidence of sunlight,
dustiness and damage.

Moreover, all these factors are connected and dependent on each other in their impact on the efficiency of solar panels. But the initial factor that determines the efficiency is the cost of manufacturing a solar battery element.

Leaders in Solar Energy Efficiency

Let's look at the leaders in the manufacture of the most efficient solar panel components and sort them by their efficiency:

44.7% efficiency from the first non-university research institute in Germany. The result was obtained for triple junction concentrators of layers of complex semiconductor composition (Ga 0.35 V 0.65 P / Ga 0.83 V 0.17 As / Ge). Such solar cells are complex and are not used for residential or commercial purposes because they are very expensive. They are used in space technology manufacturers such as NASA, where space is limited.
37.9% efficiency is obtained from single layer semiconductor junction module (InGaP/GaAs/InGaAs). In this case, the result was obtained exclusively for 90° normal to the Sun. These solar cells are also complex and time-consuming to manufacture, but their industrial production seems more promising.
32.6% was achieved by Spanish researchers from the institute (IES) and university (UPM). They used multi-modules of dual-junction semiconductor hubs. Again, these elements are still far from being widely used for commercial or residential applications.

Balancing the efficiency of solar panels

There are about a dozen largest manufacturers, producing solar panels with relatively good efficiency and moderate cost. Leading companies producing solar panels at the most modern technologies can industrially produce solar cells with an efficiency close to 25%. At the same time, mass production of modules with solar cell efficiency, which, as a rule, does not exceed 14-17%, is well established. The main reason for this difference in efficiency is that the research methods used in laboratories are not suitable for commercial production of photovoltaic products and, therefore, more accessible technologies have relatively low production costs, which leads to a decrease in efficiency in use.

To do this, we will show on a graph the dependence of the cost of the finished module to the cost of produced electricity for technological series of solar batteries with their characteristic efficiency indicators.

The comparative graph clearly shows the economic efficiency of solar cells with initial laboratory efficiency indicators, manufactured according to different technologies, in relation to the optimal cost of electricity produced at 6 cents per kWh (3.4 rubles/kWh).

Thus, the most accessible and inexpensive solar cells made of amorphous silicon in the form of a thin bendable film pay for themselves at relatively small sizes, but are not economically effective for large electricity needs. They are widely used for portable charging of phones, lamps, etc.

Polycrystalline silicon batteries are already becoming effective in residential buildings and small greenhouses.

The elements of experimental solar power plants are made on the basis of highly purified silicon monocrystals (99.999). They have optimal performance indicators and have an economically justified payback period.

The latest scientific developments of photocells, which have the highest efficiency, are used exclusively in those branches of science and industry where cost is not the main selection criterion.

The use of solar panels is increasingly becoming part of various areas our lives, but unfortunately, due to the imperfection of production technology (and as a consequence of the rather low efficiency) at a significant cost, it is not widely used.

Constantly exploring new frontiers, solar energy is moving forward, raising the efficiency of solar panels to new levels. It's no secret that the performance that solar panels provide cannot compete with established energy sources. Blame it all low performance existing panels.

Impact of various factors on performance

Increasing the efficiency of solar modules is a headache for all researchers working in this direction. Today, the efficiency of such devices ranges from 15 to 25%. The percentage is very low. Solar batteries are an extremely demanding device, the stable operation of which depends on many reasons.

The main factors that can affect performance in two ways include:

Solar cell base material. The weakest in this regard are polycrystalline solar cells, which have an efficiency of up to 15%. Modules based on indium-gallium or cadmium-tellurium, having up to 20% productivity, can be considered promising.
Orientation of the solar flux receiver. Ideally, solar panels with their working surface should be facing the sun at right angles. They should remain in this position for as long as possible. To increase the duration of correct positioning of modules in the sun, more expensive analogues have in their arsenal a sun tracking device that rotates the batteries following the movement of the luminary.
Overheating of installations. Elevated temperatures have a negative impact on power generation, so during installation it is necessary to ensure adequate ventilation and cooling of the panels. This is achieved by installing a ventilated gap between the panel and the installation surface.
The shadow cast by any object can significantly spoil efficiency indicators the entire system.

By fulfilling all the requirements and, if possible, installing the panels in the desired position, you can obtain solar panels with high efficiency. Precisely high, not maximum. The fact is that the calculated, or theoretical efficiency, is a value derived in laboratory conditions, with average parameters for the duration of daylight hours and the number of cloudy days.

In practice, of course, the percentage of beneficial effects will be lower.

When choosing solar panels for your home, it is better to focus on the lower limit of performance rather than the upper limit. Having thus chosen solar modules and all the components required for operation, you can be sure that the installed installation has sufficient power. By choosing the lower performance limit when calculating, you can save on the purchase of additional panels, which are purchased for reinsurance in case of a lack of power.

Encouraging development prospects

Today, the absolute record for efficiency in solar energy belongs to American developers and is 42.8%. This value is 2% higher than the previous record in 2010. A record amount of energy was achieved by improving a solar cell made of crystalline silicon. The uniqueness of such a study is the fact that all measurements were carried out exclusively under working conditions, that is, not in laboratory and greenhouse premises, but in real locations of the proposed installation.

Behind the scenes of the same technical laboratories, work continues to increase the latest record. The next goal of the developers is to limit the efficiency of solar modules to 50%. Every day, humanity is getting closer and closer to the moment when solar energy will completely replace the harmful and expensive energy sources currently used, and will become on a par with such giants as hydroelectric power plants.

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 of 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 junction, 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 had a size of 5 by 5 mm, 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.

A record has recently 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 production costs, 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.