How realistic is solar power from space?

(Image source: ESA)

Gigantic solar farms orbit the earth at a height of thousands of kilometers and send the energy they generate to earth by means of microwaves. Receiver units with a diameter of several kilometers convert the radiation back into usable electricity.

What sounds like a paragraph from a science fiction novel could be a reality and part of the solution to our energy problems in the not too distant future. At least when it comes to the European Space Agency ESA.

With the initiative Solaris A decision on a development program for space-based solar energy is to be made in 2025. If this is positive, a demonstration plant could be put into operation as early as 2030, and commercial operation would be possible a decade later, the head of the project, Sanjay Vijendran, told Golem.de.

In addition to Solaris, there are other projects that are seriously dealing with the topic. For example, a team from the renowned US university Caltech, which only recently managed to complete an experiment that claims to have proven the fundamental possibility of transmitting electricity from space to earth.

But how realistic is solar energy from space really? What are the advantages and disadvantages of the technology that first saw the light of day as an idea in the 1970s?

What is required for solar power from space?

In order to generate solar power in space, you need the appropriate satellites and solar modules. However, we are not talking about a few solar cells here, but about gigantic collector surfaces. Plants for the production of significant amounts of electricity in the gigawatt range would have to be square kilometers in size. The reason for this is the limited amount of energy that the sun provides per square meter – almost 1.4 kilowatts outside the earth’s atmosphere. This means 1.4 gigawatts per square kilometer.

In addition, ground stations that are several kilometers long must be set up, which receive the energy in the form of microwaves in a broad and not highly focused manner and convert it into electricity. The whole thing should look like this:

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Solar power from space – This is how the ESA wants to contribute to the energy transition

What are the main advantages of the technique?

In contrast to the earth, solar energy can be used as a base load in space. This means that it can be won there permanently without restrictions such as the time of day or the weather. The huge solar collectors also do not need to be cleaned because they do not gather dust in space. A problem that large projects have, for example, in desert areas like the Sahara. Space-based solar energy would thus solve the biggest problem of renewable energies such as wind and solar. There are simply no windless and sunless hours in space.

What are the main disadvantages of the technique?

Efficiency is the top priority here. A lot of energy is lost in transforming solar energy into electromagnetic waves (microwaves), transporting it to earth and converting it back into electricity. According to an ESA FAQ on the subject, the state of the art is even between 85 and 90 percent. That means, only 10 to 15 percent would ultimately be fed into the power grid.

That is probably just enough to operate such a system economically, but it is one of the biggest construction sites. According to Vijendran, the overall yield should be ten times higher than systems on the ground due to the continuity. The James Webb space telescope is already in use, providing a particularly deep view of the sheer endless expanse of space and thus a completely new view of humanity.

How realistic is power from space then?

According to Vijendran, from a purely technical point of view, nothing stands in the way of space-based solar energy. Flights into space, for example, have become cheaper thanks to SpaceX, and solar panels can also be mass-produced. Caltech’s successful experiment and the technical possibilities speak in favor of such a project. Nevertheless, questions arise:

• Can microwave radiation heat parts of the atmosphere? It is being discussed whether microwave radiation heats up parts of the atmosphere, for example the ionosphere, particularly strongly. However, it is not yet possible to assess whether and what the consequences of this will be. What is certain, however, is that the process does not additionally warm the earth overall. The sun’s rays would have reached the earth anyway and generated the corresponding heat.
• Are other satellites and objects in space a problem? A solar farm in space would be placed in a very high orbit where few other objects are stationed and potential hazards are therefore low. In this context, Golem speaks of an altitude of 36,000 kilometers. At this altitude, even a system measuring one square kilometer would not cloud the view of space. Nevertheless, the increasing littering of orbit is a problem that is causing many more problems now and in the future.
• Are there any dangers for humans and animals? The ESA also clears up other questions, such as safety for humans and animals. The frequency of microwave radiation is said to be too low to harm living beings. In addition, instead of a highly focused beam, a kilometer wider but weaker beam would be sent to Earth.
• Can the microwaves cause problems with airplanes? There is no answer for this yet. However, it is conceivable that the radiation will have an effect on passing aircraft and other objects, such as satellites on a lower orbin.

How do we assess solar power from space?

In addition to ESA, China and the Japanese space agency Jaxa are also dealing with the topic and are at least considering voting on test facilities. At first glance, this is quite optimistic. However, in our opinion there are still too many unanswered questions to actually assume that it will be implemented in the near future. As much as the heart of science fiction beats for space-based solar energy, in the end it still sounds like a very distant dream of the future.

how do you see it? Do you think we will see solar panels in space anytime soon? Or do you think like us and rather believe that something like this is still in the far distant future? Write it to us in the comments!