If we could utilize all the energy in the sun’s rays that hit the earth, humanity’s entire need for electricity would be covered in an hour. But it is important to succeed in capturing the energy. We have become better at doing this and solar power is gaining importance every year.
What is solar power?
The sun’s energy can be utilized in two ways: Using solar cells that convert rays into electricity, or by concentrating the sun’s rays and powering steam turbines (thermal production). Both ways are increasing in importance, but the solar cells are the largest energy source.
The reduced cost of solar panels has now made it cheaper in many places to generate electricity from the sun than electricity from fossil fuels. Therefore, in more sunny parts of the world, more and more solar power plants are being built where large areas are covered with solar panels or mirrors for thermal electricity generation. An important part of solar power is also the many smaller units that are mounted on roofs around the world.
Crystalline solar cells
SOLAR CELLS. The silicon-based classic solar cell of crystalline type.
The solar cell consists of different substances that have been combined so that the sun’s rays create a deficit of electrons in one layer and an excess in another. If these layers are then connected, an electric current is generated. This is also called photovoltaic electricity generation. Each individual solar cell generates a small amount of power, but the more connected, the greater the electricity generation.
There are different types of solar cells. Those who came first are called crystalline and largely consist of silicon. It is still the most common type you see, with a shimmering and hard surface. The advantage is that the technology is mature and silicon is a common element. The disadvantage is that manufacturing is complicated and requires heating to over 1000 degrees.
An alternative that has been developed is different types of thin film solar cells. They are plastic-based and can be bent. They are still more expensive than the crystalline ones, but the technology allows you to embed solar cells in, for example, roof tiles and generate energy from the roof without being visible.
Other alternatives at the research stage are the so-called perovskite cells, which have the potential to be considerably cheaper to manufacture.
The environmental impact of solar cells
Once in place, solar cells are a very environmentally friendly way of generating electricity. No emissions or noises occur in the process and the solar cell can produce electricity for several decades.
However, a lot of energy is spent on manufacturing, transport and assembly. A rough estimate is that crystalline-type solar cells have “paid off” their environmental debt after two years. However, this should be compared to, for example, coal power that never pays off any debt.
Solar power plants use more land than other power plants. It does not have to be a problem in, for example, deserts, but can conflict with other needs in more densely populated areas.
An alternative to converting the sun’s rays into electricity directly via solar cells is to utilize the heat in the rays and heat water to a steam turbine, which in turn generates electricity. By concentrating the sun’s rays you can create a very powerful heating system.
In many deserts or other dry and sunny areas around the world, these solar power plants are growing. They can consist of concave mirrors that capture and concentrate the sun’s rays toward its center. A more striking and futuristic construction is a tower surrounded by mirrors that catch and direct the rays towards the top of the tower, where a strong heat generation can occur.
Thermal solar power plants can even work at night. If you use specially composed salts instead of water, you can “save” the heat. The salts melt, and retain the energy. When the sun goes down, the salts emit the heat and the production of electricity can continue.
Thermal solar vs solar cells
Electricity generation using thermal solar power plants is similar to traditional electricity generation in, for example, coal-fired power plants, with a steam-powered turbine that delivers electricity in the grid in the same way. This is an advantage of such projects, but in the longer term, solar cells are probably more efficient.
The cost of production for the panels falls and you do not have to build a generator plant. Most predict that solar cells will be a much larger electricity source than thermal power plants.
Illustration of solar cells and solar power plants.
Some advantages of solar power
- Electricity production is completely emission-free.
- The sun’s rays do not end until five billion years.
Some disadvantages of solar power
- Does not work at night and very bad in cloudy weather.
- It requires large surface areas.
In many countries, solar power has become a natural feature of the household. It can be a simple barrel on the roof that, with the help of the sun’s rays, heats water for the household’s needs. It can also be about more advanced solar collectors or solar cells that make the house independent of the electricity grid. Using solar radiation at the household level on the houses to create heat and electricity is an important part of a sustainable future society.
As the technologies spread and costs go down, more people can invest in their own plants, especially in countries with a lot of solar radiation.
The expansion of solar power based on solar cells has exploded over the past decade. The development curve is exponential, ie there is a doubling of generated electricity from solar cells every year and it is hoped by many that this increase will continue, but there are no guarantees for it.
The development is based on both conscious investments in solar panels in, for example, China and lower costs for the panels. An important breaking point has been reached in many countries where the cost of producing electricity with solar cells has been lower than producing electricity with fossil fuels.
If growth in the solar sector persists, if new materials and manufacturing methods make the panels even cheaper and new technologies for converting the sun’s rays into electricity develop, solar power can become the dominant way of producing electricity within a few decades.
This would mean a lot for the transition to climate-friendly electricity production.
In the longer term, it may be possible to build large solar power plants in orbit around the earth. These could send the energy down to the earth’s surface via microwaves. The advantage of having solar panels in space is that they never end up on the night side of the earth and never under a cloud cover. They are constantly illuminated.