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The myth of the space solar power plant. Solar batteries, their use in spacecraft

Any spacecraft, especially one intended for a long mission, must be equipped with its own power source. Currently widely used solar panels, photovoltaic elements and thermoelectric generators. However, they may soon be replaced by nanosatellites equipped with electrodynamic tether systems.

Conquest of deep space

When going on a long journey by car, one of the important aspects There will be constant monitoring of the availability of gasoline. Of course, you need to carefully calculate the route, but the basic scheme is this: as soon as your supply comes to an end, you need to stop at the nearest gas station, stock up on fuel and move on. Until the next refueling.

Rockets and spacecraft are no different from cars in this regard - they also need fuel. But there is one “but” - no one has yet built gas stations in space. What to do if the device not only needs to be launched into Earth orbit, but also needs to make a really long journey, beyond the solar system?

How much does it cost to send a package into space?

If you ever set yourself such a goal, there are really few options for solving the problem. Firstly, you can sacrifice all sorts of equipment on board and send a really large supply of fuel into space. Rather, it will even more likely just be a giant flying tank of fuel - so much of it will be needed.

We doubt that you will like this method - every additional kilogram of weight when launching a rocket will cost you very, very dearly. To be more precise, about ten thousand euros. The Voyager 1 and Voyager 2 spacecraft, belonging to the so-called “deep space probes” - space stations exploring deep space - are plying solar system for forty years now. Even if you want to send enough fuel for such serious missions, you will never be able to do the basics. economic reasons. Yes and oh scientific benefit There is no need to talk about such a launch if equipment like cameras, receivers and transmitters of information have to be abandoned as much as possible.

"What do you mean you haven't been to Alpha Centauri?"

Refueling technologies in space do exist, and in general have been in use for quite a long time. Fuel is delivered to orbiting space stations and even to individual satellites, although this is much more difficult to do. Anyway, we're talking about specifically about objects that are in Earth's orbit. As soon as you are about to overcome the gravity of your home planet and go into deep space, refueling is out of the question. Space fueling stations are still a thing science fiction, in reality, this is both technologically and economically difficult and extremely unprofitable. And there will be few clients.

There remains the last, third option, in which “every man for himself”: you somehow generate energy on board your spacecraft yourself.

Einstein's legacy

On satellites located at low near-Earth orbits, having a height above the surface of the planet in the range from 160 km to 2000 km, or in geosynchronous orbits, when the satellite’s orbital period around the Earth is equal to a day, solar panels are used. Their work is based on the photovoltaic (also called photovoltaic) effect, due to which, when light hits certain substances, they produce electric current.

Photovoltaic arrays range in power from 100 watts to 300 kilowatts and are a relatively inexpensive energy source with minimal safety regulations for use.

Ubiquitous radiation

Photovoltaic energy was first used on March 17, 1958, when the Avangard-1 satellite was launched with six solar panels on board. They worked for more than six years, producing 1 watt of power. At the same time, the efficiency of these batteries, that is, the ratio of the generated energy to the amount that can actually be used to power devices, was only 10%.

Photovoltaic cells must be installed in such a way as to cover the maximum possible part surface of the satellite. It is necessary to constantly monitor their position relative to the Sun - it is advisable to always remain perpendicular to the incident radiation, since in this way the current generated will be the greatest.

It is also important to calculate that during its stay on the Sun, the satellite has time to accumulate enough energy: 40-45% of the entire orbital travel time, the device is in the shadow of the Earth and cannot generate current. In general, the efficiency of batteries is influenced by many factors, such as temperature dependence, distance to the sun, degradation of electronics under the influence of constant radiation - all of them must be taken into account when choosing a specific type of photovoltaic cells.

The warmth of our sun

Spacecraft use two types of devices that convert heat into electricity: static and dynamic. Static thermoelectric generators are usually based on a radioactive source. Dynamic thermoelectric generators, which are actively being implemented in GPS satellite systems, use alkaline electrochemical cells.

At the core this method The generation of energy is based on the Seebeck effect. It manifests itself when two different materials, which are also at different temperatures, are combined. Because of these differences, a flow of electrons occurs from the hotter end to the cooler end - we get an electric current. The device itself for generating energy is called a thermoelement or thermocouple.

The Seebeck effect also has the opposite phenomenon, the Peltier effect, in which when an electric current is passed through an alloy of two conductors or semiconductors, the junction heats up in one direction and cools in the other. The Peltier effect is used in space to cool electronic equipment: due to the lack of convection in a vacuum, this turns out to be a rather problematic task.

To use the Seebeck and Peltier effects, of course, a heat source is required. For this purpose, NASA specialists have developed a standardized radioisotope thermoelectric generator operating on plutonium-238 with a half-life of 87.7 years. On at the moment 41 similar generators are used on 23 spacecraft, with power ranging from 2 to 300 watts. The fundamental disadvantage of using radioactive isotopes is the possibility of contamination environment, if launch the mission will pass unsuccessful.

When GPS doesn't work, SAMTEC is to blame

Dynamic electric generators should become more efficient. Their main difference from static ones is the method of converting mechanical energy into electrical energy. If in thermoelectric elements heat is directly converted into electricity, then in electrochemical concentration elements the expansion energy of sodium vapor is used for these purposes.

IN GPS satellites a new generation of thermoelectric converters of the Solar AMTEC type (solar alkali metal thermal-to-electric conversion - converter of solar thermal energy into electrical energy based on alkali metals), or SAMTEC for short, were introduced.

In SAMTEC generators the receiver solar radiation heats a reservoir of liquid sodium, which evaporates. Sodium vapor is passed through a special membrane that separates the gas high pressure(temperature 800-1000 o C) from gas low pressure(temperature 200-300 o C). Due to the pressure difference, positively charged sodium ions accumulate on one side of the filter, and negatively charged electrons on the other. The potential difference created can generate an electric current in a connected external circuit.

The efficiency of SAMTEC cells is 15-40%, with a service life of 10-12 years without a decrease in performance under constant radiation conditions in space. The power generated can vary from a few watts to kilowatts.

Cosmic threads

Space tether - a thin metal rope attached to an orbital or suborbital spacecraft - a rocket, satellite or space station. The length of space cables varies from several meters to tens of kilometers (the world record is just over 32 kilometers). The cables are made of especially strong materials that can withstand enormous loads.

Space tether systems are divided into two categories - mechanical and electrodynamic. Cables of the first category are used, in particular, to exchange speeds and connect various spacecraft to each other to move as one.

Electrodynamic cable systems use special materials that are not only durable, but also conductive (usually aluminum or copper). When such cables move in the Earth's magnetic field, an electromotive force acts on free charges in metals, creating an electric current. Also, regions of ionized gas with different densities and properties present in space and the presence of the ionosphere near the Earth itself contribute to this process.

Numerical simulations, verified by experiment, showed that for a large satellite, an electrodynamic tether ten kilometers long could generate an average power of 1 kilowatt with an energy conversion efficiency of 70-80%. A cable of this length, made of aluminum, would weigh only 8 kilograms, which is negligible compared to the weight of an average orbiter.

Nanoship

Space generators have been developed and studied for many decades. They are well described from a theoretical point of view, and are exposed to the most extreme conditions on Earth - but at the same time, the development of “extraterrestrial” energy sources is much slower than their terrestrial counterparts. Surprisingly, space exploration, which is at the forefront of technology, turns out to be a very, very conservative area in which the introduction of new developments rarely occurs due to many risks and economic reasons.

However, we are at the dawn of a completely new field: nanosatellites, and even much smaller satellites. They can serve as a base for space tether systems, and by launching many such devices into space at once, we will be able to generate much more electricity. Perhaps they are the ones who will revolutionize the field of energy generation in space, expand the technological capabilities of spacecraft and increase their operating time.

These are photovoltaic converters - semiconductor devices that convert solar energy into direct electric current. Simply put, these are the basic elements of the device we call “solar panels.” With the help of such batteries space orbits artificial earth satellites operate. Such batteries are made here in Krasnodar - at the Saturn plant. The plant management invited the author of this blog to look at the production process and write about it in his diary.


1. The enterprise in Krasnodar is part of the Federal Space Agency, but Saturn is owned by the Ochakovo company, which literally saved this production in the 90s. The owners of Ochakovo bought a controlling stake, which almost went to the Americans. Ochakovo invested heavily here, purchased modern equipment, managed to retain specialists, and now Saturn is one of the two leaders in Russian market production of solar and rechargeable batteries for the needs of the space industry - civil and military. All profits that Saturn receives remain here in Krasnodar and go to the development of the production base.

2. So, it all starts here - at the so-called site. gas phase epitaxy. In this room there is a gas reactor, in which a crystalline layer is grown on a germanium substrate for three hours, which will serve as the basis for a future solar cell. The cost of such an installation is about three million euros.

3. After this, the substrate still has a long way to go: electrical contacts will be applied to both sides of the photocell (moreover, on the working side the contact will have a “comb pattern”, the dimensions of which are carefully calculated to ensure maximum passage sunlight), an antireflective coating will appear on the substrate, etc. - a total of more than two dozen technological operations at various installations before the photocell becomes the basis of the solar battery.

4. Here, for example, is a photolithography installation. Here, “patterns” of electrical contacts are formed on photocells. The machine performs all operations automatically, according to a given program. Here the light is appropriate, which does not harm the photosensitive layer of the photocell - as before, in the era of analogue photography, we used “red” lamps.

5. In the vacuum of the sputtering installation, electrical contacts and dielectrics are deposited using an electron beam, and antireflective coatings are also applied (they increase the current generated by the photocell by 30%).

6. Well, the photocell is ready and you can start assembling the solar battery. Busbars are soldered to the surface of the photocell in order to later connect them to each other, and a safety glass, without which in space, under radiation conditions, the photocell may not withstand the load. And, although the glass thickness is only 0.12 mm, a battery with such photocells will work for a long time in orbit (in high orbits for more than fifteen years).


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7. The electrical connection of photocells to each other is carried out with silver contacts (they are called bars) with a thickness of only 0.02 mm.

8. To obtain the required network voltage generated by the solar battery, photocells are connected in series. This is what a section of series-connected photocells (photoelectric converters - that's correct) looks like.

9. Finally, the solar battery is assembled. Only part of the battery is shown here - the panel in mockup format. There can be up to eight such panels on a satellite, depending on how much power is needed. On modern communications satellites it reaches 10 kW. Such panels will be mounted on a satellite, in space they will open like wings and with their help we will watch satellite television, use satellite Internet, navigation systems (GLONASS satellites use Krasnodar solar panels).

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10. When a spacecraft is illuminated by the Sun, the electricity generated by the solar battery powers the spacecraft's systems, and excess energy is stored in the battery. When the spacecraft is in the shadow of the Earth, the device uses electricity stored in the battery. The nickel-hydrogen battery, having a high energy capacity (60 W h/kg) and a practically inexhaustible resource, is widely used on spacecraft. The production of such batteries is another part of the work of the Saturn plant.

In this photo, the assembly of a nickel-hydrogen battery is carried out by Anatoly Dmitrievich Panin, holder of the medal of the Order of Merit for the Fatherland, II degree.

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11. Assembly area for nickel-hydrogen batteries. The battery contents are prepared for placement in the housing. The filling is positive and negative electrodes separated by separator paper - it is in them that the transformation and accumulation of energy occurs.

12. Installation for electron beam welding in a vacuum, with the help of which the battery case is made from thin metal.

13. Section of the workshop where battery cases and parts are tested for impact high blood pressure.
Due to the fact that the accumulation of energy in the battery is accompanied by the formation of hydrogen, and the pressure inside the battery increases, leak testing is an integral part of the battery manufacturing process.

14. The housing of a nickel-hydrogen battery is a very important part of the entire device operating in space. The housing is designed for a pressure of 60 kg s/cm 2; during testing, rupture occurred at a pressure of 148 kg s/cm 2.

15. Tested batteries are charged with electrolyte and hydrogen, after which they are ready for use.

16. The body of a nickel-hydrogen battery is made of a special metal alloy and must be mechanically strong, lightweight and have high thermal conductivity. The batteries are installed in cells and do not touch each other.

17. Rechargeable batteries and batteries assembled from them are subjected to electrical tests on installations of our own production. In space it will be impossible to fix or replace anything, so every product is carefully tested here.

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18. All space technology is tested for mechanical influences using vibration stands that simulate the loads when launching a spacecraft into orbit.

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19. In general, the Saturn plant made the most favorable impression. The production is well organized, the workshops are clean and bright, the people working are qualified, communicating with such specialists is a pleasure and very interesting for a person who is at least to some extent interested in our space. I left Saturn in a great mood - it’s always nice to see a place here where they don’t engage in idle chatter and shuffle papers, but do real, serious work, successfully compete with similar manufacturers in other countries. There would be more of this in Russia.


Photos: © drugoi

P.S. Blog of the Vice President of Marketing at Ochakovo

Recently, a conference “New Generation of Suborbital Explorers” was held in Colorado, at which, in particular, projects for the construction of space solar stations were discussed. And if no one took such ideas seriously before, now they are really close to implementation.

Thus, the US Congress is preparing a plan for America’s gradual transition from fossil fuels to space energy. A specially created space department will be responsible for the implementation of the project; NASA, the Department of Energy and other organizations will play an active role in its work.

By October of this year, the Department of Justice must submit to Congress all necessary changes and additions to the current federal legislation to begin construction of space solar power plants. As part of the program for initial stage it is planned to develop nuclear systems space engines, to use reusable ships for space logistics and the construction of solar power plants in orbit.

Technologies that will transform sunlight into electricity and teleport it to Earth.

In particular, experts from the California Institute of Technology propose illuminating the planet using orbital “flying carpets.” These are systems of 2,500 panels, 25 mm thick and 2/3 of a football field long. Elements of such a station will be delivered into orbit by rockets like the Space Launch System, an American super-heavy launch vehicle being developed by NASA. The space power plant is being created as part of the SSPI (Space Solar Power Initiative), a partnership between California Tech University and Northrup Grumman. The latter has invested $17.5 million to develop the core components of the system over the next three years. The initiative was also supported by researchers at NASA's Jet Propulsion Laboratory.

According to Caltech professor Harry Atwater, who led the Space Solar Power Initiative, "magic carpets" convert solar energy into radio waves and send them to earth. The energy will be transmitted using the phased array principle used in radar systems. This will create a flow moving in any direction.

Solar panels consist of tiles measuring 10x10 cm and weighing about 0.8 g, which will ensure a relatively low cost of launching the structure. Each tile will transmit the converted energy autonomously and if one of them fails, the rest will continue to work. The loss of a few elements due to solar flares or small meteorites will not harm the power plant. According to scientists, with mass production, the cost of electricity from such a source will be less than when using coal or natural gas.

The percentage of ground-mounted solar installations in the overall energy supply balance of many countries around the world is becoming increasingly higher. But the capabilities of such power plants are limited: at night and in heavy clouds, solar panels lose their ability to generate electricity. Therefore, the ideal option is to place solar power plants in orbit, where day does not give way to night, and clouds do not create barriers between the Sun and the panels. The main advantage of building a power plant in space is its potential efficiency. Solar panels located in space can generate ten times more energy than batteries located on the surface of the Earth.

The idea of ​​orbital power plants has been developed for a long time; scientists from NASA and the Pentagon are working on similar studies since the 60s. Previously, the implementation of such projects was slowed down high cost transportation, but with the development of technology, space power plants may become a reality in the foreseeable future.

There are already several interesting projects for the construction of solar installations in orbit. In addition to the Space Solar Power Initiative, the Americans are developing an orbital solar panel that will absorb solar radiation and transmit electron beams using radio waves to an earthly receiver. The authors of the development were specialists from the US Navy Research Laboratory. They built a compact solar module with a photovoltaic panel on one side. Inside the panel there is electronics that convert direct current into radio frequency for signal transmission, the other side supports an antenna for transmitting electron beams to Earth.

According to the lead author of the development, Paul Jaffe, the lower the frequency electron beam, carrying energy, the more reliable its transmission will be in bad weather. And at a frequency of 2.45 GHz, you can receive energy even during the rainy season. The solar receiver will provide energy for all military operations; diesel generators can be forgotten forever.

USA not the only country, which plans to receive electricity from space. The fierce struggle for traditional energy resources has forced many states to look for alternative energy sources.

The Japanese space exploration agency JAXA has developed a photovoltaic platform for installation in Earth orbit. The solar energy collected using the installation will be supplied to receiving stations on the Earth and converted into electricity. Solar energy will be collected at an altitude of 36 thousand km.

Such a system, consisting of a series of ground and orbital stations, should begin operating in 2030, its total capacity will be 1 GW, which is comparable to the standard nuclear power plant. To achieve this, Japan plans to build an artificial island 3 km long, on which a network of 5 billion antennas will be deployed to convert ultra-high frequency radio waves into electricity. JAXA researcher Susumi Sasaki, who led the development, is confident that placing solar batteries in space will lead to a revolution in energy, making it possible over time to completely abandon traditional energy sources.

China has similar plans, which will build a solar power plant in Earth orbit larger than the International Space Station. Total area The installation of solar panels will amount to 5-6 thousand square meters. km. According to expert calculations, such a station will collect solar rays 99% of the time, and space solar panels will be able to generate 10 times more electricity per unit area than their ground-based counterparts. It is assumed that the generated electricity will be converted into microwaves or laser beam. Construction is scheduled to begin in 2030, and the project will cost about $1 trillion.

Worldwide engineers are assessing the possibilities of building solar space power plants not only in orbit, but also in areas closer to the Sun, near Mercury. In this case, almost 100 times less solar panels will be required. In this case, receiving devices can be moved from the Earth's surface into the stratosphere, which will allow efficient energy transfer in the millimeter and submillimeter ranges.

Projects for lunar solar power plants are also being developed.

For example, the Japanese company Shimizu proposed creating a belt of solar panels stretching along the entire equator of the Moon for 11 thousand km and a width of 400 km.

It will be posted on back side satellite of the Earth so that the system is constantly under sun rays. The panels can be connected using regular power cables or optical systems. The generated electricity is planned to be transmitted using large antennas and received using special receivers on Earth.

In theory, the project looks great, all that remains is to figure out how to deliver hundreds of thousands of panels to the Earth’s satellite and install them there, as well as how to deliver energy from the Moon to our planet without losing a significant part of it along the way: after all, you will have to cover 364 thousand km. So the ideas of creating lunar power plants are too far from reality and if they are realized, it will not be very soon.

Tatyana Gromova


Where will we place the CSP? Most likely at GSO. In other orbits, you either need to install receivers all over the planet, or carry a bunch of batteries with you.

Let’s not fantasize for now, but let’s look at the available possibilities.

The Angara launch vehicle from the Plesetsk cosmodrome will deliver 3-4 tons to the geostationary orbit. What can you put in them? Very approximately 100 squares of solar panels. With a constant focus on the Sun and Efficiency percent 20 you can squeeze out 300 W per square. Let’s assume they degrade by 5% per year (I hope it won’t surprise anyone that solar panels in space they deteriorate from radiation, micrometeorites, etc.).
Let's count: (100*300*24*365*20)/2=2,628,000,000 Wh.
To understand the full scale of the problem, let these megawatts reach the Earth without loss. The power is impressive, but what if we are not flying anywhere. There are 300 tons of kerosene available. Kerosene is almost gasoline. He makes one more assumption and takes a regular gas generator (200KW for 50 liters per hour).
200000*300000/50=1,200,000,000 Wh
What happens: we drain gasoline from the rocket and already get half the power.
Another half of the rocket is occupied by liquid oxygen. I wanted to calculate the cooling and liquefaction through the heat capacity, but then I just came across a price on the Internet of 8,200 rubles per ton of liquid oxygen. Since the cost price is practically electricity alone (let a kilowatt be 2 rubles):
300*8200*1000/2= 1,230,000,000 Wh
Oops, second half. Already 0% efficiency. We haven’t counted the rocket yet.

But we will invent some kind of payload launcher into orbit

That is, we will somehow communicate the kinetic energy to the panels in the form of 10 km/s:
3000*10000 2 /2 = 150000000000 J = 41,700,000 Wh
It seems that there is an efficiency of 5000%, but there are some problems:
- it is unlikely that it will be possible to throw the object high enough, so part of the mass and energy must be spent on overcoming the atmosphere;
- everything that is thrown from the Earth according to the laws of ballistics will return to the Earth, that is, another part of the mass will go to the rise of perigee.
Let a ton go to thermal protection. Let's calculate the change in orbit:
ΔV=root((3.986ּ10 14 /42000000)(1+2*6000000/(6000000+42000000)))=3441 m/s
The best engines give an impulse of 4500. Let’s take Tsiolkovsky’s formula:
M final =2000/exp(4500/3500)=572 kg
Let's take electric rocket engines, the impulse is 10 times greater and we have panels. Yes, but with the existing power of the panels, the thrust will be millinewtons, and the transition will take years. And we only have a couple of hours before landing.
As a result: minus the engine, tanks, overloads - it’s good if we get the same amount.

Let's raise the panels on the elevator

Overall the idea is not bad. If you simply raise the load to a height, then we calculate the change in potential energy:
3000*9.81*36000000/3600 = 294,300,000 Wh
How to communicate them to the cargo? Electricity transmission options:
- By the elevator itself. It is not difficult to imagine the losses and mass of a conductor 36,000 km long. I wish I could build the elevator myself.
- By laser – minus a significant part of the mass for transformation.
- Deliver a certain number of panels traditional way and then lift the rest on a rope for free. For a megawatt of power you need 3 km 2 of panels. In this case, it will take two weeks to lift the load. Those. We will raise the same megawatt in a year.

Other difficulties

Freely using kilometers of panels and the efficiency of receiving solar energy in space, rare authors tell how they are going to orient the panels towards the Sun. GSO is stationary only relative to the Earth. Accordingly, we need mechanisms and fuel.
We also need converters, guardians, and receivers on Earth. Are there many consumers near the equator? High voltage lines through half of the ball. If all this is multiplied by the non-100% probability of completing the task, the question is, who can do it?

Conclusions:

- With existing technologies, building a space solar power station is unprofitable.
- Even if you lift everything on a space elevator, by the time construction is completed the question will arise of how to dispose of the failing panels.
- You can bring an asteroid to Earth and make panels from it. Something tells me that by the time we can do this, there will no longer be a need to transmit energy to Earth.

However, there is no smoke without fire. And under the seemingly peaceful intentions there may be completely different intentions.
For example, building a combat space station is orders of magnitude simpler and much more efficient:
- the orbit can and should be chosen lower;
- 100% hitting the receiver is not necessary;
- very short time from pressing the start button to hitting the target;
- no pollution of the area.

These are the conclusions. The calculations may contain errors. As usual, I invite readers to correct them.

Holding "Russian space systems"(RKS, part of Roscosmos) has completed the creation of a modernized electrical protection system for domestically produced solar panels. Its use will significantly extend the life of spacecraft power supplies and will make Russian solar panels one of the most energy efficient in the world. The development is reported in press release received by the editor.

The design of the new diodes used patented technical solutions, which significantly improved their performance characteristics and increased their reliability. Thus, the use of specially developed multilayer dielectric insulation of the crystal allows the diode to withstand reverse voltages of up to 1.1 kilovolts. Thanks to this, the new generation of protection diodes can be used with the most efficient photovoltaic converters (PVCs) available. Previously, when diodes were unstable to high reverse voltage, it was necessary to choose not the most efficient samples.

To increase the reliability and service life of diodes, RKS created new multilayer switching buses for diodes based on molybdenum, thanks to which the diodes can withstand more than 700 thermal shocks. Thermal shock is a typical situation for solar cells in space, when, during the transition from the illuminated part of the orbit to the shaded part of the Earth, the temperature changes by more than 300 degrees Celsius in a few minutes. Standard components of terrestrial solar batteries cannot withstand this, and the service life of space batteries is largely determined by the number of thermal shocks that they can survive.

The active lifespan of a spacecraft solar battery equipped with new diodes will increase to 15.5 years. The diode can be stored on Earth for another 5 years. So the general warranty period The service life of new generation diodes is 20.5 years. The high reliability of the device is confirmed by independent life tests, during which the diodes withstood more than seven thousand thermal cycles. The proven group production technology allows RKS to produce more than 15 thousand new generation diodes per year. Their deliveries are planned to begin in 2017.

The new solar cells will withstand up to 700 temperature changes of 300 degrees Celsius and will be able to work in space for more than 15 years

Solar batteries for space consist of photovoltaic converters (PVCs) measuring 25x50 millimeters. The area of ​​solar panels can reach 100 square meters(for orbital stations), so there can be a lot of solar cells in one system. FEPs are arranged in chains. Each individual chain is called a "string". In space, individual solar cells are periodically damaged by cosmic rays, and if they did not have any protection, the entire solar battery in which the affected converter is located could fail.

The basis of the solar battery protection system is made up of diodes - small devices installed complete with solar cells. When the solar battery partially or completely falls into the shade, the solar cells, instead of supplying current to the batteries, begin to consume it - reverse voltage flows through the solar cells. To prevent this from happening, a shunt diode is installed on each PV cell, and a blocking diode is installed on each “string”. The more efficient the solar cell, the more current it produces, the greater the reverse voltage will be when the solar panel enters the Earth's shadow.

If the shunt diode does not “pull” the reverse voltage above a certain value, the solar cells will have to be made less efficient so that both the forward charging current of the batteries and the reverse current of unwanted discharge are minimal. When, over time, under the influence of destabilizing factors outer space individual solar cells or a “string” immediately fail, such elements are simply cut off without affecting the working solar cells and other “strings”. This allows the remaining, still working, converters to continue working. Thus, the energy efficiency and active life of the solar battery depend on the quality of the diodes.

In the USSR, only blocking diodes were used on solar batteries; if one solar cell malfunctioned, they immediately turned off the whole chain of converters. Because of this, the degradation of solar panels on Soviet satellites was rapid and they did not work for very long. This forced us to more often make and launch devices to replace them, which was very expensive. Since the 1990s, when creating domestic spacecraft, foreign-made solar cells began to be used, which were purchased assembled with diodes. It was possible to turn the situation around only in the 21st century.